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Surgical emphysema is a well-recognised complication of laparoscopic surgery, but its impact on end-tidal carbon dioxide levels and carbon dioxide elimination is seldom reported and may not be fully appreciated by anaesthetists. Four cases are presented where extensive surgical emphysema occurred during laparoscopic surgery. The visual display of the anaesthetic record using the software program Monitor showed substantial rises in end-tidal carbon dioxide levels and allowed calculation of the carbon dioxide elimination, which increased two- to three-fold above normal levels. Having a visual record of carbon dioxide changes facilitated the recognition of surgical emphysema in three out of the four cases. Strategies such as estimating and tracking changes in carbon dioxide elimination from the minute ventilation and end-tidal carbon dioxide levels may assist in early identification, and palpating for surgical emphysema is recommended during laparoscopy if other causes of increased carbon dioxide levels are excluded. [ABSTRACT FROM AUTHOR]

The study objective was to show that fentanyl given five minutes prior to induction improved insertion conditions for the Classic Laryngeal Mask Airway. Previous work had shown fentanyl at 90 seconds to be unpredictable. A probit analysis design was used in which success/failure rates of different doses of fentanyl were measured and dose-response curves drawn from which the ED50 and ED95 with 95% confidence intervals were determined. Adult Chinese patients with American Society of Anesthesiologists physical status classification I or II and requiring anaesthesia for minor surgery with a laryngeal mask were recruited. They were randomly assigned to one of six dosage groups: 0.25, 0.5, 1.0, 1.5, 2.0 and 3.0 microg x kg1. Fentanyl was given prior to propofol 25 mg x kg(-1), and insertion was assessed 90 seconds later using six categories of patient response. Ninety-six patients, aged 18 to 63 years, were studied. The six dosage groups were similar As the fentanyl dose increased, fewer patients responded to insertion (P < 0.01). Dose-responses could be predicted for all categories, except resistance to insertion and laryngospasm. Probit analysis predicted an ED50 of 0.5 microg x kg(-1) and ED, of 7.5 microg x kg(-1) for ideal insertion conditions (i.e., no swallowing, gagging, body movement or laryngospasm). Commonly used fentanyl doses of 1 to 2 microg x kg(-1) only prevented patients responding to insertion in 70 to 80% of cases. When using propofol 2.5 mg x kg(-1), administering fentanyl five minutes before laryngeal mask insertion does not provide ideal insertion conditions in 95% of cases unless excessively large doses are used. An ideal dose of fentanyl that produces optimum insertion conditions could not be determined. [ABSTRACT FROM AUTHOR]

We describe a novel technique, previously applied to small children, for adult one-lung anaesthesia in which a single-lumen endotracheal tube is used with an endobronchial balloon blocker The main aims of the technique are to reduce the likelihood of cephalad displacement of the balloon into the trachea and to facilitate directional placement of the endobronchial balloon. We present five illustrative cases of one-lung anaesthesia in patients of adult size, in which the endotracheal tube-endobronchial balloon technique was considered preferable to the use of a double-lumen tube technique. The situations included difficult intubation, need for postoperative ventilation, a tortuous trachea and an unexpected need to perform one-lung anaesthesia. The technique involved deliberate placement of the endotracheal tube tip near the carina to block cephalad dislodgement of the blocker The chance of the balloon blocking the endotracheal tube tip could be further reduced by having the intraluminal endobronchial balloon blocker emerge through the Murphy eye. [ABSTRACT FROM AUTHOR]

Formative Assessment Case Studies (FACS) are an e-learning resource consisting of a case scenario punctuated with decision-making steps (multiple-choice questions) and feedback for wrong answers. FACS was developed to enhance clinical decision-making skills. We wrote six FACS scenarios covering preoperative assessment topics and made them accessible to 149 final year medical students as part of their two-week anaesthesia module. A data management system recorded usage and performance by each student. Eighty-one percent of students attempted FACS (six cases 53%, five cases 17%, one to four cases 9%) and 61 to 70% completed all steps. On average FACS was attempted 1.5 times. Students required 44 to 95% more steps than the minimum to complete each case. There were two patterns of use: some students completed the cases within five to seven minutes (first quartile) focusing on the questions, while others spent over 22 to 35 minutes (fourth quartile) exploring the FACS and feedback. FACS usage correlated (r2 = 0.32: P < 0.01) with written case report marks. The students' evaluation of FACS was high. FACS is an e-learning resource that is interactive and facilitates higher learning. It can be applied successfully to disciplines less well represented in the medical curriculum, such as anaesthesia. FACS facilitated our teaching of preoperative assessment to a group of final year medical students. It was well received and shown to facilitate the learning of decision-making skills. The students' usage of FACS could have been enhanced by making FACS compulsory and using summative FACS for assessment. [ABSTRACT FROM AUTHOR]

OBJECTIVE: Intraabdominal hypertension reduces organ blood flow. Restoring abdominal perfusion pressure (APP) may restore renal blood flow, especially when sepsis is present. The effects of intra-abdominal pressure (IAP), followed by restoration of APP with norepinephrine, on renal blood flow were determined. DESIGN: Longitudinal study with bacteremia after nonbacteremic (control) conditions. SETTING: University animal laboratory. SUBJECTS: Ten anesthetized mongrel dogs. INTERVENTIONS: IAP was raised to 10, 20, and 30 mm Hg, using intra-abdominal bags filled with saline. After each intervention, decompression was achieved by emptying the bag. Bacteremia was induced by injection of Escherichia coli. Cardiac output and renal blood flow were measured using surgically placed flow probes. Norepinephrine infusion was used to restore the mean arterial pressure to baseline at each IAP. A hypervolemic circulation was maintained throughout by infusing saline. MEASUREMENTS AND MAIN RESULTS: Induction of bacteremia resulted in significant decreases in blood pressure, cardiac output, and renal blood flow (p < .01). Serial increases in IAP decreased cardiac output and renal blood flow both in control and bacteremic dogs (p < .001). These decreases were substantially corrected by abdominal decompression. In nonbacteremic control conditions, restoring APP back to baseline with norepinephrine did not fully restore cardiac output and renal blood flow (p < .001). However, in bacteremic conditions, norepinephrine was able to substantially restore cardiac output and renal blood flow to bacteremic baseline at all levels of IAP. In bacteremic conditions, the renal perfusion fraction returned to bacteremic baseline levels after correction of APP with norepinephrine and after decompression. CONCLUSIONS: Restoration of APP using norepinephrine improves renal blood flow in bacteremic animals with IAPs up to 30 mm Hg, and maintaining a therapeutic APP may preserve renal blood flow in patients with intra-abdominal hypertension who are at risk of IAP-induced renal injury but who have yet to meet accepted criteria for surgical decompression. [ABSTRACT FROM AUTHOR]

Background: Aortocaval compression (ACC) can result in haemodynamic disturbances and uteroplacental hypoperfusion in parturients. Its detection is difficult because in most patients, sympathetic compensation results in no signs or symptoms. However, profound hypotension may develop after sympathectomy during regional anaesthesia. In this prospective observational study, we aimed to detect ACC by analysing haemodynamic changes in term parturients who were positioned sequentially at different angles of lateral tilt.Methods: We studied haemodynamic changes in 157 non-labouring term parturients who were positioned in random order at 0°, 7.5°, 15°, and full left lateral tilt. Cardiac output (CO), stroke volume, and systemic vascular resistance were derived using suprasternal Doppler. Non-invasive arterial pressure (AP) measured in the upper and lower limbs was analysed to detect aortic compression.Results: CO was on average 5% higher when patients were tilted at ≥15° compared with <15°. In a subgroup of patients (n=11), CO decreased by more than 20%, without changes in systolic AP, when they were tilted to <15° which was considered attributable to severe inferior vena caval compression. Only one patient in the supine position had aortic compression with the systolic AP in the upper limb 25 mm Hg higher than the lower limb.Conclusions: Patients with ACC can be identified by the CO changes from serial measurements between supine, 15°, or full lateral tilt. Our findings suggest that in non-labouring parturients, ACC is asymptomatic and can be effectively minimized by the use of a left lateral tilt of 15° or greater. [ABSTRACT FROM AUTHOR]

Background: During general anaesthesia (GA) for Caesarean section (CS), fetal oxygenation is increased by administering an inspired oxygen fraction (Fi(o(2))) of 1.0. However, it is unclear whether such high Fi(o(2)) will increase oxygen free radical activity.Methods: We randomized 39 ASA I-II parturients undergoing elective CS under GA to receive 30% (Gp 30), 50% (Gp 50), or 100% (Gp 100) oxygen with nitrous oxide and sevoflurane adjusted to provide equivalent minimum alveolar concentration. Baseline maternal arterial blood before preoxygenation and maternal arterial, umbilical arterial and venous blood at delivery were sampled for assays of the by-product of lipid peroxidation, isoprostane, and for measurement of blood gases and oxygen content.Results: Maternal and umbilical isoprostane concentrations were similar among the three groups at delivery, despite significantly increased maternal and fetal oxygenation in Gp 100. However, paired comparisons of maternal delivery vs baseline concentration of isoprostane showed an increase at delivery for all groups [Gp 30: mean 342 (sd 210) vs 154 (65) pg ml(-1), P=0.016; Gp 50: 284 (129) vs 156 (79) pg ml(-1), P=0.009; Gp 100: 332 (126) vs 158 (68) pg ml(-1), P<0.001]. The magnitude of increase was similar in all three groups and independent of the Fi(o(2)) or duration after induction.Conclusions: GA for CS is associated with a marked increase in free radical activity in the mother and baby. The mechanism is unclear but it is independent of the inspired oxygen in the anaesthetic mixture. Therefore, when 100% oxygen is administered with sevoflurane for GA, fetal oxygenation can be increased, without inducing an increase in lipid peroxidation. [ABSTRACT FROM AUTHOR]

Background: Controversy still exists if the administration of supplementary oxygen to patients having emergency Caesarean section (CS) under regional anaesthesia is beneficial or potentially harmful. Therefore, in a prospective double-blinded study, we randomized patients having emergency CS under regional anaesthesia to receive either air or 60% oxygen until delivery and compared the effects on fetal oxygenation and lipid-peroxidation in the mother and baby.Methods: We recruited 131 women having emergency CS under regional anaesthesia. Either 21% (air group) or 60% oxygen (oxygen group) was administered using a Venturi-type facemask until delivery. We compared the oxygen exposure duration, umbilical arterial (UA) and venous (UV) blood gases and oxygen content, and plasma concentration of 8-isoprostane. Subanalysis was performed according to whether or not fetal compromise was considered present.Results: Data from 125 patients were analysed. For the oxygen group vs the air group, there were greater values for UA PO(2) [mean 2.2 (SD 0.5) vs 1.9 (0.6) kPa, P=0.01], UA O(2) content [6.6 (2.5) vs 4.9 (2.8) ml dl(-1), P=0.006], UV PO(2) [3.8 (0.8) vs 3.2 (0.8) kPa, P<0.0001], and UV O(2) content [12.9 (3.5) vs 10.4 (3.8) ml dl(-1), P=0.001]. There was no difference between the groups in maternal, UA, or UV 8-isoprostane concentration. Apgar scores and UA pH were similar between the groups. Similar changes were observed regardless of whether fetal compromise was considered present (n=37) or not (n=88).Conclusions: Breathing 60% oxygen during emergency CS under regional anaesthesia increased fetal oxygenation with no associated increase in lipid-peroxidation in the mother or fetus. [ABSTRACT FROM AUTHOR]

The assessment and optimization of cardiovascular and hemodynamic variables is a mainstay of patient management in the care for critically ill patients in the intensive care unit (ICU) or the operating room (OR). It is, therefore, of outstanding importance to meticulously validate technologies for hemodynamic monitoring and to study their applicability in clinical practice and, finally, their impact on treatment decisions and on patient outcome. In this regard, the Journal of Clinical Monitoring and Computing (JCMC) is an ideal platform for publishing research in the field of cardiovascular and hemodynamic monitoring. In this review, we highlight papers published last year in the JCMC in order to summarize and discuss recent developments in this research area.

The demise of the pulmonary artery catheter as a gold standard in cardiac output measurement has created the need for new standard. Doppler cardiac output can be measured suprasternally (USCOM) and via the oesophagus (CardioQ). Use in tandem they may provide a reliable trend line of cardiac output changes against which new technologies can be assessed. Data from three similar clinical studies was pooled. Simultaneous USCOM and CardioQ readings, 13 (7-27), were performed every 15-30 min intraoperatively. Within individual patient regression analysis was performed. Data was normalized, CardioQ against USCOM, to eliminate the systematic error component following calibration. Bland-Altman and trend, concordance and polar analysis, were performed on the grouped data. Cardiac output was indexed (CI) to BSA. Data from 53 patients, aged 59 (26-81) years, scheduled for major surgery were included. Within-individual mean (SD) CI was 3.4 (0.6) L min(-1) m(-2). Correlation was good to excellent in 83 % of cases, R(2) > 0.80, and reasonable in 96 %, R(2) > 0.60. Percentage error was 38 %, and decreased to 14 % with normalization. The estimated 95 % precision for a single Doppler reading was ±10 %. Concordance rate was 96.6 % (confidence intervals 94.7-99.5 %) and above the >92 % threshold for good trending ability. Polar analysis also confirmed good trending ability. The regression line between Doppler methods was offset with a slope of 0.9, thus CardioQ CI readings increased relative to USCOM. Both Doppler methods trended cardiac output reliably. Used in tandem they provide a new standard to assess cardiac output trending.

To compare the performance of a bioreactance cardiac output (CO) monitor (NICOM) and transcutaneous Doppler (USCOM) during head up tilting (HUT). Healthy young adult subjects, age 22 ± 1 years, 7 male and 7 female, were tilted over 3-5 s from supine to 70° HUT, 30° HUT and back to supine. Positions were held for 3 min. Simultaneous readings of NICOM and USCOM were performed 30 s into each new position. Mean blood pressure (MBP), heart rate (HR), CO and stroke volume (SV), and thoracic fluid content (TFC) were recorded. Bland-Altman, percentage changes and analysis of variance for repeated measures were used for statistical analysis. Pre-tilt NICOM CO and SV readings (6.1 ± 1.0 L/min and 113 ± 25 ml) were higher than those from USCOM (4.1 ± 0.6 L/min and 77 ± 9 ml) (P < 0.001). Bland-Altman limits of agreement for CO were wide with a percentage error of 38 %. HUT increased MBP and HR (P < 0.001). CO and SV readings decreased with HUT. However, the percentage changes in USCOM and NICOM readings did not concur (P < 0.001). Whereas USCOM provided gravitational effect proportional changes in SV readings of 23 ± 15 % (30° half tilt) and 44 ± 11 % (70° near full tilt), NICOM changes did not being 28 ± 10 and 33 ± 11 %. TFC decreased linearly with HUT. The NICOM does not provide linear changes in SV as predicted by physiology when patients are tilted. Furthermore there is a lack of agreement with USCOM measurements at baseline and during tilting.

Background: Hypotension is a common side effect of general anesthesia induction, and when severe, it is related to adverse outcomes. Ultrasonography of inferior vena cava (IVC) is a reliable indicator of intravascular volume status. This study investigated whether preoperative ultrasound IVC measurements could predict hypotension after induction of anesthesia., Methods: One hundred four adult patients, conforming to American Society of Anesthesiologists physical status I to III, scheduled for elective surgery after general anesthesia were recruited. Maximum IVC diameter (dIVCmax) and collapsibility index (CI) were measured preoperatively. Before induction, mean blood pressure (MBP) was recorded. After induction, MBP was recorded for 10 min after intubation. Hypotension was defined as greater than 30% decrease in MBP from baseline or MBP less than 60 mmHg. Receiver operating characteristic curve analysis with gray zone approach and regression analyses were used., Results: IVC scanning was unsuccessful in 13.5% of patients. Data from 90 patients were analyzed. After induction, 42 patients developed hypotension. Areas (95% confidence interval) under the curves were 0.90 (0.82 to 0.95) for CI and 0.76 (0.66 to 0.84) for dIVCmax. The optimal cutoff values were 43% for CI and 1.8 cm for dIVCmax. The gray zone for CI was 38 to 43% and included 12% of patients and that for dIVCmax was 1.5 to 2.1 cm and included 59% of patients. After adjusting for other factors, it was found that CI was an independent predictor of hypotension with the odds ratio of 1.17 (1.09 to 1.26). CI was also positively associated with a percentage decrease in MBP (regression coefficient = 0.27)., Conclusions: Preoperative ultrasound IVC CI measurement was a reliable predictor of hypotension after induction of general anesthesia, wherein CI greater than 43% was the threshold.

Background: The thoracic aorta elongates and unfolds with advancing age. Lateral displacement and tortuosity of the descending part may affect oesophageal Doppler monitoring (ODM) readings because probe alignment becomes slanted. This investigation aimed to relate aortic displacement as it appears on the chest radiograph with variations in ODM readings as the probe is inserted to different depths., Methods: In anaesthetized patients a series of three to five ODM stroke volume (SV) readings were obtained at insertion depths of 35-45 cm during stable haemodynamics. The coefficient of variation (CV=standard deviation/mean %) was calculated. The degree of descending aorta unfolding was measured by (i) lateral displacement (LD), that is, the difference in the maximum and minimum distances between the midline and para-aortic line; and (ii) curvature angle (CA), the angle formed by a tangential line from the intersection of the para-aortic line and the diaphragm to its curve with the vertical line., Results: Data from 70 patients were analysed. The median CV of SV readings was 14% (range 4-48). Variation between ODM readings, shown by the CV of SV readings, increased linearly with aortic unfolding: R2=0.44 for LD and R2=0.60 for CA. Patients with a CA ≤15° were younger and had significantly lower CVs of ODM readings than those with a CA >15° (P=0.001). Age and hypertension was associated with increased CA., Conclusions: Increased lateral displacement and tortuosity of the descending aorta reduces the reliability of ODM measurements as probe depth is varied, especially with aging., (© The Author 2015. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Virtual patients are computerised representations of realistic clinical cases. They were developed to teach clinical reasoning skills through delivery of multiple standardized patient cases. The anesthesia course at The Chinese University of Hong Kong developed two novel types of virtual patients, formative assessment cases studies and storyline, to teach its final year medical students on a 2 week rotational course. Acute pain management cases were used to test if these two types of virtual patient could enhance student learning. A 2 × 2 cross over study was performed in academic year 2010-2011 on 130 students divided into four groups of 32-34. Performance was evaluated by acute pain management items set within three examinations; an end of module 60-item multiple choice paper, a short answer modified essay paper and the end of year final surgery modified essay paper. The pain management case studies were found to enhanced student performance in all three examinations, whilst the storyline virtual patient had no demonstrable effect. Student-teaching evaluation questionnaires showed that the case studies were favored more than the storyline virtual patient. Login times showed that students on average logged onto the case studies for 6 h, whereas only half the students logged on and used the storyline virtual patient. Formative assessment case studies were well liked by the students and reinforced learning of clinical algorithms through repetition and feedback, whereas the educational role of the more narrative and less interactive storyline virtual patient was less clear .

Background: Different mathematical approaches are used to calculate arterial pulse pressure wave analysis (PPWA) cardiac output. The CardioQ-Combi is a research oesophageal Doppler (COODM) monitor that includes these five fundamental PPWA algorithms. We compared these PPWA cardiac output readings to COODM and suprasternal USCOM Doppler (COUS) over a range of cardiac output values induced by dopamine infusion in patients undergoing major surgery. USCOM acted as a control., Methods: Serial sets of cardiac output data were recorded at regular intervals as cardiac output increased. Formulae included: cardiac output calculated form systemic vascular resistance (COMAP), pulse pressure (COPP), Liljestrand-Zander formula (COLZ), alternating current power (COAC) and systolic area with Kouchoukos correction (COSA). The reference method for comparisons was COODM. Statistical methods included: Scatter plots (correlation), Bland-Altman (agreement) and concordance (trending) and polar (trending)., Results: From 20 patients 255 sets of cardiac output comparative data were collected. Mean cardiac output for each method ranged between 5.0 and 5.5 litre min(-1). For comparisons between COUS and the five PPWA algorithms with COODM: Correlation was best with COUS (R(2)=0.81) followed by COLZ (R(2)=0.72). Bias ranged between 0.1 and 0.5 litre min(-1). Percentage error was lowest with COUS (26.4%) followed by COLZ (35.2%), others (40.7 to 56.3%). Concordance was best with COUS (92%), followed by COLZ (71%), others (64 to 66%). Polar analysis (mean(standard deviation)) were best with COUS (-2.7 (21.1)), followed by COLZ (+4.7 (26.6)., Conclusions: The Liljestrand-Zander PPWA formula was most reliable compared with oesophageal Doppler in major surgical patients under general anaesthesia, but not better than USCOM., (© The Author 2015. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Objective: To evaluate the risks of perioperative respiratory complications and postoperative morbidity associated with active and passive cigarette smoking., Background: Environmental tobacco smoke is associated with perioperative respiratory events in children, but its effect in adults is unknown., Methods: We conducted a cohort study of 736 adult patients receiving general anesthesia for major elective surgery. Patients were classified according to their self-reported smoking history and urinary cotinine concentration within 48 hours before surgery. The main outcomes were composite measures of perioperative respiratory complications and postoperative morbidity on the third day after surgery., Results: There were 313 (42.5%) never-smokers (reference group), 92 (12.5%) passive nonsmokers, 157 (21.3%) ex-smokers without environmental tobacco smoke exposure, 53 (7.2%) passive ex-smokers, and 121 (16.4%) smokers. The incidence of perioperative respiratory complications and postoperative morbidity was 9.5% [95% confidence interval (CI), 7.5-11.8] and 29.2% (95% CI, 26.0-32.6), respectively. Smoking was significantly associated with an increased risk of perioperative respiratory complications [relative risk (RR), 4.40; 95% CI, 2.20-8.80] and postoperative morbidity (RR, 1.86; 95% CI, 1.22-2.83). Although passive smoking was not associated with the risk of perioperative respiratory complications, the risk of postoperative morbidity was increased in passive nonsmokers (RR, 1.51; 95% CI, 1.04-2.21) and passive ex-smokers (RR, 2.21; 95% CI, 1.39-3.50)., Conclusions: One in 5 adults was exposed to environmental tobacco smoke before surgery. Passive cigarette smoking showed very little, if any, increased risk of perioperative respiratory complications. Both active exposure and passive exposure to cigarette smoke increased the risk of postoperative morbidity.

Problem: The availability of less expensive and smaller ultrasound machines has enabled the use of ultrasound in virtually all major medical/surgical disciplines. Some medical schools have incorporated point-of-care ultrasound training into their undergraduate curriculum, whereas many postgraduate programs have made ultrasound training a standard. The Chinese University of Hong Kong has charged its Department of Anaesthesia and Intensive Care to spearhead the introduction of ultrasound into the final-year medical curriculum by introducing handheld transthoracic echocardiography as part of perioperative assessment., Intervention: All 133 final-year students completed a 2-week anesthesia rotation, which began with a half-day session consisting of a lecture and hands-on practice session during which they learned 9 basic transthoracic echocardiography views using 4 basic ultrasound probe positions., Context: Each student was required to perform a transthoracic echocardiography-examine under supervision of 1 patient/week for 2 weeks, and their results were compared against that of the supervisor's. Most patients were elective cardiac surgery patients. One long question on transthoracic echocardiography was included in their end-of-year surgery examination paper. Students provided feedback on their experience., Outcome: Most students learned the basic transthoracic echocardiography views fairly efficiently and had variable, though generally favorable, success rates in identifying obvious cardiac anomalies, including use of color Doppler. A few common mistakes were identified but were easily correctable. Logistics for mobilizing enough bedside supervision were challenging. Students reported positive feedback on the teaching initiative., Lessons Learned: We were able to execute a successful short training course on transthoracic echocardiography during the final-year medical degree anesthesia rotation. Our initiative may set an example for other clinical departments to design similar courses pertinent to their specialties and syllabuses.

Minimally-invasive cardiac output (CO) monitoring to follow changes in CO would be helpful in anaesthesia practice. Two Doppler systems marketed for this purpose include the CardioQ (Deltex Medical Group, Chichester, United Kingdom), which uses an oesophageal probe, and the USCOM (USCOM Ltd., Sydney, NSW, Australia), which uses a hand-held probe. The aim of the study was to assess the ability of these two methods to track CO during major surgery and to determine their relationship. Twenty patients, age 58 (26 to 81) years, (m/f) 15/5, requiring abdominal surgery were studied. The surgical procedures lasted between 128 and 408 minutes and a total of 285 data pairs (8 to 22 per case) were collected. Time plots showed good tracking ability across a wide range of CO in most patients. Correlation between the two devices was excellent in 14 patients (R² >0.85), good in another four (R² >0.64) and poor in two. Regression line data supported the hypothesis that CardioQ under-reads at low CO and over-reads at high CO in respect to the USCOM. However, the precision between the two CO readings was poor with wide limits of agreement and a percentage error of ± 37%. These findings indicate that these devices individually track changes in CO in many patients but cannot be relied upon to provide the same values.

Supra-sternal Doppler (USCOM Ltd., Sydney, Australia) can be used during anaesthesia to measure cardiac output (CO) and related flow parameters. However, before the USCOM can be used routinely, its utility and limitations need to be fully understood and critical information about its use disseminated. In "Window to the Circulation" we use the example of an elderly man undergoing major urological robotic surgery to highlight the utility and limitations of intra-operative USCOM use. USCOM readings were verified against oesophageal Doppler. Despite the lack of major blood loss (<500 ml in 8-h), significant changes in haemodynamics were recorded. CO ranged from 3.2 to 8.3 l/min. The quality of USCOM scans and reliability of data was initially poor, but improved as CO increased as surgery progressed. When USCOM scans became acceptable the correlation with oesophageal Doppler was R(2) = 8.0 (p < 0.001). Several characteristic features of the supra-sternal Doppler scans were identified: Aortic and pulmonary flow waves, valve closure, E and A waves, false A-wave and aberrant arterial flow patterns. Their identification helped with identifying the main flow signal across the aortic valve. The USCOM has the potential to monitor changes in CO and related flow parameters intra-operatively and thus help the anaesthetist to more fully understand the patient's haemodynamics. However, achieving a good quality scan is important as it improves the reliability of USCOM data. The supra-sternal route is rich in flow signals and identifying the aortic valve signal is paramount. Recognizing the other characteristic waveforms in the signal helps greatly.

Objective: The precision of thermodilution cardiac output measurement using a pulmonary artery catheter can be divided into random and systematic errors. This study determined the systematic component., Design: Comparative validation against a transonic flow probe on the aortic root., Setting: Animal research laboratory., Participants: Eight anesthetized pigs, weight 27 to 32 kg., Interventions: Thermodilution measurements were compared to those from an aortic flow probe. One (or two) catheters were tested in each pig, with multiple paired readings recorded as cardiac output was varied pharmacologically by esmolol, epinephrine, or dopamine. Linear regression lines were drawn for each pig as well as the slope used to quantify systematic error. Regression analysis of data from each pig was used to assess trending. Bland-Altman analysis also was performed., Measurements and Main Results: Systematic error derived from slope data was ± 26%. Trending was reliable in 8 out of 10 catheter placements (p value>0.95). Bland- Altman analysis (n = 77 basal anesthesia and 165 pharmacologic intervention data pairs) provided percentage errors of ± 23% and ± 34-39%, respectively. This percentage error increase was due to variations in calibration and the slopes of regression lines for each catheter tested as the lines diverged as cardiac output increased, widening the spread of data., Conclusions: Thermodilution does trend cardiac output reliably in most cases. However, the systematic error is large and has a significant effect on the percentage error as cardiac output increases. The precision error of ± 20% currently used for thermodilution measurement may be set too low and is dependent on the clinical setting., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Background: The ultrasound cardiac output monitor (USCOM) is a continuous wave Doppler system designed to measure cardiac output (CO) non-invasively and intermittently either from the pulmonary or from the aortic valve. USCOM scan quality is critical to obtaining reliable data and during anaesthesia it is said to deteriorate with increasing age. The aim of this study was to investigate the effect of age on supra-sternal USCOM scan repeatability during anaesthesia., Methods: We performed a series of 6 USCOM scans in 180 patients of all ages after induction for routine surgery. A 12-point Cattermole (CS) score and 10-point insonation (IS) score were used to evaluate scan quality and ease of insonation. The coefficients of variation (CVs) of USCOM variables [CO, peak velocity, stroke volume index (SVI) and the corrected flow time] were derived from the series of six readings., Results: In >95% of young patients (age <50 yr), it was easy to obtain a good-quality USCOM scan (CS>8). In these patients, repeatability of serial readings was good with CVs<5% and precision of less than ±10%. In older patients (>50 yr), scan quality and ease of insonation declined, with >25% of patients >60 yr having unreliable USCOM scans (CS<5). In these patients, the CV was >5-10%. In several elderly patients (>65 yr), we failed to locate the USCOM signal. Average scan time increased with age (30 to >60 s). SVI was also strongly correlated with scan quality (R(2)=0.77)., Conclusions: Increasing age has a significant effect on USCOM scan quality and data reliability.

Objective: To evaluate the ability of the third-generation (3.01) of FloTrac/Vigileo monitor (Edwards Lifesciences, Irvine, CA) to follow variations in cardiac output (∆CO) using the new polar plot approach., Design: Prospective interventional study., Setting: Single hospital university study., Participants: Twenty-five patients referred for cardiac surgery., Interventions: CO was measured simultaneously by 3 to 5 bolus thermodilution (COtd measurements), using a pulmonary artery catheter and by arterial pulse contour analysis, using the FloTrac/Vigileo (COvi). Data were collected at eight time points: before incision, after sternotomy, before and after protamine sulfate infusion, at the start of sternal closure, at the end of surgery, on arrival to intensive care unit, and after a standardized volume expansion with 500 mL of hetastarch 6%., Measurements and Main Results: One-hundred thirty-five pairs of CO data were collected; the mean bias of all CO measurements corrected for repeated measures was 0.2 L/min with limits of agreements of -3.3 L/min and +2.9 L/min. The percentage error was 66.5%. The polar plot analysis included 71 significant ∆CO and showed a mean polar angle of -3.4 degrees with 95% polar percentage error equivalent limits of -61 to 55; 69% of analysed data points fell within the 30-degree limits and provided a correct polar concordance rate., Conclusions: Third-generation FloTrac/Vigileo software still lacks the accuracy to reliably detect changes in cardiac output (∆CO) in cardiac surgery. Improvements to FloTrac/Vigileo CO algorithm and software still are needed in this particular setting., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Background: Cardiac output (CO) measurement with lithium dilution (COLD) has not been fully validated in sheep using precise ultrasonic flow probe technology (COUFP). Sheep generate important cardiovascular research models and the use of COLD has become more popular in experimental settings., Methods: Ultrasonic transit-time perivascular flow probes were surgically implanted on the pulmonary artery of 13 sheep. Paired COLD readings were taken at six time points, before and after implantation of a left ventricular assist device (LVAD) and compared with COUFP recorded just after lithium injection., Results: The mean COLD was 5.7 litre min(-1) (range 3.8-9.6 litre min(-1)) and mean COUFP 5.9 litre min(-1) (range 4.0-9.2 litre min(-1)). The bias (standard deviation) was 0.3 (1.0) litre min(-1) [5.1 (16.9)%] and limits of agreement (LOA) were -1.7 to 2.3 litre min(-1) (-28.8 to 39.0%) with a percentage error (PE) of 34.4%. Data to assess trending [rate (95% confidence intervals)] included a 78 (62-93)% concordance rate in the four-quadrant plot (n=27). In the half moon polar plot (n=19), the mean polar angle was +5°, the radial LOA were -49 to +35° and 68 (47-89)% of data points fell within 22.5° of the mean polar angle. Both tests indicated moderate to poor trending ability., Conclusion: COLD is not precise when evaluated against COUFP in sheep based on the statistical criteria set, but the results are comparable with previously published animal studies.

Cardiac output can be measured non-invasively using supra-sternal Doppler (USCOM, Sydney, NSW, Australia). However, scanning can be difficult in practice in older patients, the reason for which has not been elucidated previously. Chest radiographs from 60 previously studied anaesthetised patients were reviewed and scored for aortic unfolding, enlargement and calcification, and cardiac enlargement. Corresponding supra-sternal Doppler scans were graded as easy or difficult using the Cattermole scoring system. Twenty patients who were difficult to scan, aged 60-88 years, had mean (SD) radiological scores of 5.9 (2.5) out of 12, while 20 adult controls, 40-60 years, and 20 older patients who were easy to scan, 60-80 years, had radiological scores of 0.9 (1.1) and 1.7 (1.4), respectively (p < 0.001). Over 75% of the patients who were difficult to scan had two or more radiological features suggestive of aortic unfolding and cardiac enlargement. Morphological or anatomical changes associated with ageing within the upper chest play an important part in the success of using supra-sternal Doppler in older patients., (© 2013 The Association of Anaesthetists of Great Britain and Ireland.)

Objectives: Musculoskeletal structures often appear brighter on imaging in the elderly, which makes it difficult to accurately delineate a peripheral nerve during ultrasound-guided regional anaesthetic procedures. The echo intensity of skeletal muscles is significantly increased in the elderly. However, there are no data comparing the echo intensity of peripheral nerves in the young and the elderly, which this study was designed to evaluate., Methods: 13 healthy, young volunteers (aged <30 years) and 11 elderly patients (aged >60 years) who were scheduled to undergo orthopaedic lower limb surgery were recruited. The settings of the ultrasound system were standardised and a high-frequency linear array transducer was used for the scan. A transverse scan of the median nerve (MN) and the flexor muscles (FMs) at the left mid-forearm was performed and three video loops of the ultrasound scan were recorded for each subject. Still images were captured from the video loops and normalised. Computer-assisted greyscale analysis was then performed on these images to determine the echo intensity of the MN and the FMs of the forearm., Results: The echo intensity of the MN and FMs of the mid-forearm was significantly increased in the elderly (p<0.005). There was also a reduction in contrast between the MN and the adjoining FM in the elderly (p = 0.04)., Conclusion: Under the conditions of this study, the MN and the FMs in the forearm appeared significantly brighter than those in the young, and there was a loss of contrast between these structures in sonograms of the elderly.

Background: Cannulation of the internal jugular vein (IJV) is traditionally performed using the central-longitudinal approach. Pneumothorax, carotid artery puncture, and failure to cannulate are uncommon, but by no means rare, complications. Ultrasound (US) guidance for IJV cannulation has reduced but not eliminated such complications., Technique: We herein introduce a new approach, coined the "medial-transverse approach" due to the perpendicular angle at which the introducer needle is advanced toward the IJV from the median to lateral direction., Discussion: The direction of the introducer needle is not toward the lung, thus virtually eliminating the possibility of pneumothorax. The image of the entire needle is seen when the US probe is typically orientated for a short-axis view of the IJV and carotid artery, thus improving the chance of uncomplicated IJV puncture. We have used this technique with apparent success in thousands of cases over the past 20 years in two different institutions., Conclusion: A modified IJV cannulation technique that seems to have unique advantages over traditional approaches has been described. This technique is compatible with the blind and US-guided approaches., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Background: Reliable cardiac output monitoring is particularly useful in the cirrhotic patient undergoing liver transplant surgery, because cirrhosis of the liver is associated with a vasodilated and high output state, known as cirrhotic cardiomyopathy, that challenges the reliability of pulse contour cardiac output technology. The contractility of the ventricle in cirrhosis is impaired, which is tolerated even though the ejection fraction and cardiac output are elevated because of the low peripheral resistance. However, during surgery the cirrhotic patient can decompensate because of the physiological changes and stress of surgery. Recently, we showed that the FloTrac/Vigileo™ failed to perform in cirrhotic patients undergoing transplant surgery. In response, the company upgraded their software. Therefore, we have assessed the accuracy and reliability of this new third-generation (version 3.02) FloTrac/Vigileo algorithm software in the same setting., Methods: The cardiac index was measured simultaneously by single-bolus thermodilution (CI(TD)), using a pulmonary artery catheter, and pulse contour analysis, using the FloTrac/Vigileo (CI(V)). Readings were made at 10 time points during and after liver transplant surgery in 21 patients. Comparisons with data from our 2009 study, which used second-generation (version 01.10) software, were also made., Results: Our new data show that version 3.02 software significantly reduced the adverse effect on pulse contour cardiac output reading bias in low peripheral resistance states, and thus improves the overall precision and trending ability of the system. Regression analysis between CI(TD) and CI(V) showed that the correlation was moderate (r =0.67, 95% confidence interval, 0.40 to 0.86). The Bland and Altman analysis showed that bias was 0.4 L.min(-1) · m(-2), and the percentage error was 52% (95% confidence interval, 49% to 55%). Trending ability of the new software also was improved but was still well below the current benchmarks., Conclusion: The new software (version 3.02) provided substantial improvements over the previous versions with better overall precision and trending ability. Further algorithm refinements will increase this technology's reliability to be extensively used in the highly complex setting of cirrhotic patients undergoing liver transplantation.

Purpose of Review: Thoracic trauma leading to multiple fractured ribs (MFR) remains very common. Good analgesia may help to improve a patient's respiratory mechanics and to avoid intubation of the trachea for ventilatory support and therefore may dramatically alter the course of recovery. We herein review the analgesia options for patients with MFR., Recent Findings: For healthy patients with one to two fractured ribs, systemic analgesics may suffice. For more than three to four fractured ribs, studies and experience have reaffirmed the superior analgesia made possible with thoracic epidural, thoracic paravertebral, and intercostal blocks. From experience, interpleural block has significant drawbacks. Catheterization allows the continuation of analgesia for 2 or more days with just one block. Use of the landmark technique is usually satisfactory for accurate block placement but ultrasound and nerve stimulation are showing promise in further improving needle and catheter placement accuracy, especially in the presence of difficult anatomy., Summary: Thoracic epidural, thoracic paravertebral, and intercostal blocks are the top choices for patients with MFR and they are of equivalent efficacy. Each has unique advantages and disadvantages. Our preference tends to be the thoracic paravertebral approach.

Objectives: To develop a valid statistical method of showing acceptable cardiac output (CO) trending ability when new CO monitors are compared to a reference standard, such as thermodilution, using polar coordinates., Design: Developing a new statistical analytic method using historic data., Setting: University Hospital Anesthesia and Intensive Care Department., Participants: Data taken from previously published CO validation studies., Interventions: Cartesian data were reanalyzed, being uplifted using Data Thief 3.0 software (http://datathief.org/). Polar plots were constructed from this data. Central zone data (<0.5 L/min or <10% change) were excluded because they introduced statistical noise. Trial polar criteria were set using data from a study that compared 5 CO monitors against thermodilution. Then, these criteria were further validated using data extracted from 15 other studies. Mean (95% confidence intervals) polar angles were used., Measurements and Main Results: Trial data suggest ±5° (angle) ±30° (95% confidence interval) as acceptance limits. Concordance rates (ie, >95%-90%) from 5 articles supported trending, and polar data from these studies concurred with the authors' pilot criteria. Favorable comments on trending also were found in 8 of 15 articles in which radial limits were less than ±32°. Good calibration was associated with a mean polar angle of less than ±5°., Conclusions: Polar plots can be used to show the trending ability of CO monitors in comparative validation studies. They overcome the deficiencies of concordance analysis, which uses the direction of change as a statistic and ignores the magnitude of change in CO., (Copyright © 2011 Elsevier Inc. All rights reserved.)

e-Learning has revolutionized the way in which undergraduate medical education is delivered. One e-learning tool of note is the virtual patient (VP), a type of computer software that simulates real-life clinical scenarios, in which the learner emulates the role of health care provider to obtain the history, conduct examination, and make diagnoses and management decisions. VPs have been in use since 1993. Early designs were based on serial screen-cards of patient history, examination, investigations, diagnoses, treatment, and outcome, which the learner explored. With the development of web technology, VPs can now be accessed via the Internet and are more versatile, supporting different structural designs to suit a variety of learning objectives, and they can branch via different routes through a case. Using VPs has a number of advantages: 1) VPs improve access to learning material, 2) VPs help learners to acquire higher order cognitive skills like strategic thinking and decision making, 3) VPs provide a safe environment to practice, 4) VPs help to teach interdisciplinary care, and 5) VPs can be used instead of patients for examination. A number of well-known VP player systems are in use today: CASUS, CAMPUS, web-based Simulation of Patients, OpenLabyrinth, and vpSim. At the Chinese University of Hong Kong, we have also developed a web-based VP authoring and player system called Formative Assessment Case Studies (FACS), which is run by our Teaching and Learning Resources Centre. FACS has been integrated into Year-5 Anesthesia teaching since 2006. Three VP products have been developed: Anaesthesia FACS (six cases) that teaches preoperative assessment, Acute Pain Management FACS, and an eight-part longitudinal VP which tells the story of a patient's stay, and anesthesia care, for routine gynecological surgery. Students spend about 3 hours on each during a 2-week clinical attachment. Our VPs have been well received and have overcome problems of providing adequate clinical exposure.

Three pulse contour systems for monitoring cardiac output - LiDCO Plus™, PiCCO Plus™ and FloTrac™ - were compared in postcardiac surgery patients. None of the three methods demonstrated good trending ability according to concordance analysis. Pulse contour systems remain unreliable in the haemodynamically unstable patient., (© 2011 BioMed Central Ltd)

Background: Thermodilution cardiac output using a pulmonary artery catheter is the reference method against which all new methods of cardiac output measurement are judged. However, thermodilution lacks precision and has a quoted precision error of ± 20%. There is uncertainty about its true precision and this causes difficulty when validating new cardiac output technology. Our aim in this investigation was to determine the current precision error of thermodilution measurements., Methods: A test rig through which water circulated at different constant rates with ports to insert catheters into a flow chamber was assembled. Flow rate was measured by an externally placed transonic flowprobe and meter. The meter was calibrated by timed filling of a cylinder. Arrow and Edwards 7Fr thermodilution catheters, connected to a Siemens SC9000 cardiac output monitor, were tested. Thermodilution readings were made by injecting 5 mL of ice-cold water. Precision error was divided into random and systematic components, which were determined separately. Between-readings (random) variability was determined for each catheter by taking sets of 10 readings at different flow rates. Coefficient of variation (CV) was calculated for each set and averaged. Between-catheter systems (systematic) variability was derived by plotting calibration lines for sets of catheters. Slopes were used to estimate the systematic component. Performances of 3 cardiac output monitors were compared: Siemens SC9000, Siemens Sirecust 1261, and Philips MP50., Results: Five Arrow and 5 Edwards catheters were tested using the Siemens SC9000 monitor. Flow rates between 0.7 and 7.0 L/min were studied. The CV (random error) for Arrow was 5.4% and for Edwards was 4.8%. The random precision error was ± 10.0% (95% confidence limits). CV (systematic error) was 5.8% and 6.0%, respectively. The systematic precision error was ± 11.6%. The total precision error of a single thermodilution reading was ± 15.3% and ± 13.0% for triplicate readings. Precision error increased by 45% when using the Sirecust monitor and 100% when using the Philips monitor., Conclusion: In vitro testing of pulmonary artery catheters enabled us to measure both the random and systematic error components of thermodilution cardiac output measurement, and thus calculate the precision error. Using the Siemens monitor, we established a precision error of ± 15.3% for single and ± 13.0% for triplicate reading, which was similar to the previous estimate of ± 20%. However, this precision error was significantly worsened by using the Sirecust and Philips monitors. Clinicians should recognize that the precision error of thermodilution cardiac output is dependent on the selection of catheter and monitor model.

Numerous cardiac output (CO) monitors have been produced that provide continuous rather than intermittent readings. Bland and Altman has become the standard method for validating their performance against older standards. However, the Bland and Altman method only assesses precision and does not assess how well a device detects serial changes in CO (trending ability). Currently, there is no consensus on how trending ability, or trend analysis, should be performed. Therefore, we performed a literature review to identify articles published between 1997 and 2009 that compared methods of continuous CO measurement. Identified articles were grouped according to measurement technique and statistical methodology. Articles that analyzed trending ability were reviewed with the aim of finding an acceptable statistical method. Two hundred two articles were identified. The most popular methods were pulse contour (69 articles), Doppler (54), bioimpedance (38), and transpulmonary or continuous thermodilution (27). Forty-one articles addressed trending, and of these only 23 provided an in-depth analysis. Several common statistical themes were identified: time plots, regression analysis, Bland and Altman using change in CO (ΔCO), and the 4-quadrant plot, which used direction of change of ΔCO to determine the concordance. This plot was further refined by exclusion of data when values were small. Receiver operating characteristic curves were used to define the exclusion zone. In animal studies, a reliable reference standard such as an aortic flowprobe was frequently used, and regression or time plots could be used to show trending. Clinical studies were more problematic because data collection points were fewer (8-10 per subject). The consensus was to use the 4-quadrant plot with exclusion zones and apply concordance analysis. A concordance rate of >92% when using a 15% zone indicated good trending. A new method of presenting trend data (ΔCO) on a polar plot is proposed. Agreement was shown by the angle with the horizontal axis and ΔCO by the distance from the center. Trending can be assessed by the vertical limits of the data, similar to the Bland and Altman method.

During trauma resuscitation involving massive transfusion, the best fresh-frozen plasma to packed red blood cells ratio is unknown. No randomised controlled trial (RCT) is available on this subject, although there are plenty of observational studies suggesting that the ratio should be about 1:1. This ratio also makes more physiological sense, and we suggest that in patients with massive and ongoing bleeding, it is a sensible strategy with which to start resuscitation., (Copyright 2010 Elsevier Ireland Ltd. All rights reserved.)

Background: Since thromboelastography (TEG) can detect hypercoagulable states, it is a potentially useful test for predicting postoperative thromboembolic complications. Therefore, we performed a systematic review of the literature to evaluate the accuracy of TEG in predicting postoperative thromboembolic events., Methods: PUBMED and EMBASE electronic databases were searched by two independent investigators to identify prospective studies involving adult patients undergoing operative procedures in which a TEG test was performed perioperatively and outcomes were measured by reference standards. The quality of included studies was assessed and measures of diagnostic test accuracy were estimated for each included study., Results: Ten studies (with a total of 1056 patients) were included in this analysis; however, only five reported measures of TEG test accuracy. The overall quality of the studies and level of diagnostic evaluation of the studies were highly variable, from poor to good. As there were variations in the definition of hypercoagulability, TEG methodology and patient characteristics, reference standards used and outcomes measured, a meta-analysis was not undertaken. The sensitivity and specificity ranged from 0% to 100% and 62% to 92%, respectively. The diagnostic odds ratio ranged from 1.5 to 27.7; area under the curve ranged from 0.57 to 0.91. Of the TEG variables, maximum amplitude seems to be the best parameter to identify hypercoagulable states and to predict thromboembolic events., Conclusions: The predictive accuracy of TEG for postoperative thromboembolic events is highly variable. To determine if the TEG is a clinically useful screening test in high-risk surgical populations, more prospective studies are needed.

Airway, breathing, and circulation are top priorities in any resuscitation. However, in cardiac tamponade, the decision to intubate the trachea and initiate positive pressure ventilation (PPV) should only be taken after consideration of the deleterious haemodynamic effects of positive intrathoracic pressure. We suggest that the threshold for intubation and PPV should be raised in tamponade and that intubation and PPV should, if possible, be timed so that relief of tamponade can immediately follow. In the trauma setting, emergency thoracotomy is the best approach. When intubation is unavoidable because of very low oxygen saturation or cardiac arrest, high ventilatory pressures should be avoided.

Background: The pulmonary artery catheter is invasive and may cause serious complications. A safe method of cardiac output (CO) measurement is needed. We have assessed the accuracy and reliability of a recently marketed self-calibrating arterial pulse contour CO monitoring system (FloTrac/Vigileo) in end-stage liver failure patients undergoing liver transplant. The pattern of alterations known as cirrhotic cardiomyopathy, and the transplant procedure itself, provided an evaluation under varying clinical conditions., Methods: The cardiac index was measured simultaneously by thermodilution (CI(TD): mean of four readings) using a pulmonary artery catheter and pulse contour analysis (CI(V): mean value computed by the FloTrac/Vigileo over the same time period). Readings were made at 10 time-points during liver transplant surgery (T1-T5) and on the intensive care unit (T6-T10). CI(V) was computed using the latest Vigileo software version 01.10., Results: A total of 290 paired readings from 29 patients were collected. Mean (SD) CI(TD) was 5.2 (1.3) and CI(V) was 3.9 (0.9) litre min(-1) m(-2), with a corrected for repeated measures bias between readings of 1.3 (0.2) litre min(-1) m(-2) and 95% limits of agreement of -1.5 (0.2) to 4.1 (0.3) litre min(-1) m(-2). The percentage error (2SD(Bias)/meanCI(TD)) was 54%, which exceeded a 30% limit of acceptance. Low peripheral resistance and increasing bias were related (r=0.69; P<0.001). The Vigileo system failed to reliably trend CI data, with a concordance compared with thermodilution below an acceptable level (at best 68% of sequential readings)., Conclusions: In cirrhotic patients with hyperdynamic circulation, the Vigileo system showed a degree of error and unreliability higher than that considered acceptable for clinical purposes.

The present study was performed to test a new software version of the FloTrac/Vigileo using head-up-head-down tilting in post-cardiac surgery patients. Impressive improvements in Bland and Altman limits of agreement from 37.5% to 21.6% were recorded. The results, however could be attributed to a failure to produce a wide enough range of test circulatory conditions. A more rigorous test of performance is needed before any real conclusion concerning use of the FloTrac/Vigileo in clinical practice can be made.