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Shock is a life-threatening clinical condition that arises when there is inadequate oxygen metabolism at a cellular level. It can occur in a wide range of clinical conditions and without prompt identification and management it has a high morbidity and mortality. Treatment focuses on both correcting the cause and managing the abnormal physiology associated with shock. Clinicians use a number of tools including clinical examination, biochemical markers and haemodynamic monitoring to both identify and treat shock. In this article we will review the normal physiology of oxygen delivery, the aetiology and pathophysiology of shock and how haemodynamic monitoring is used to manage patients presenting with shock. [ABSTRACT FROM AUTHOR]

Arterial pressure monitoring and management are mainstays of haemodynamic therapy in patients having surgery. This article presents updated consensus statements and recommendations on perioperative arterial pressure management developed during the 11th POQI PeriOperative Quality Initiative (POQI) consensus conference held in London, UK, on June 4–6, 2023, which included a diverse group of international experts. Based on a modified Delphi approach, we recommend keeping intraoperative mean arterial pressure ≥60 mm Hg in at-risk patients. We further recommend increasing mean arterial pressure targets when venous or compartment pressures are elevated and treating hypotension based on presumed underlying causes. When intraoperative hypertension is treated, we recommend doing so carefully to avoid hypotension. Clinicians should consider continuous intraoperative arterial pressure monitoring as it can help reduce the severity and duration of hypotension compared to intermittent arterial pressure monitoring. Postoperative hypotension is often unrecognised and might be more important than intraoperative hypotension because it is often prolonged and untreated. Future research should focus on identifying patient-specific and organ-specific hypotension harm thresholds and optimal treatment strategies for intraoperative hypotension including choice of vasopressors. Research is also needed to guide monitoring and management strategies for recognising, preventing, and treating postoperative hypotension. [ABSTRACT FROM AUTHOR]

It is unclear whether optimising intraoperative cardiac index can reduce postoperative complications. We tested the hypothesis that maintaining optimised postinduction cardiac index during and for the first 8 h after surgery reduces the incidence of a composite outcome of complications within 28 days after surgery compared with routine care in high-risk patients having elective major open abdominal surgery. In three German and two Spanish centres, high-risk patients having elective major open abdominal surgery were randomised to cardiac index-guided therapy to maintain optimised postinduction cardiac index (cardiac index at which pulse pressure variation was <12%) during and for the first 8 h after surgery using intravenous fluids and dobutamine or to routine care. The primary outcome was the incidence of a composite outcome of moderate or severe complications within 28 days after surgery. We analysed 318 of 380 enrolled subjects. The composite primary outcome occurred in 84 of 152 subjects (55%) assigned to cardiac index-guided therapy and in 77 of 166 subjects (46%) assigned to routine care (odds ratio: 1.87, 95% confidence interval: 1.03–3.39, P =0.038). Per-protocol analyses confirmed the results of the primary outcome analysis. Maintaining optimised postinduction cardiac index during and for the first 8 h after surgery did not reduce, and possibly increased, the incidence of a composite outcome of complications within 28 days after surgery compared with routine care in high-risk patients having elective major open abdominal surgery. Clinicians should not strive to maintain optimised postinduction cardiac index during and after surgery in expectation of reducing complications. NCT03021525. [ABSTRACT FROM AUTHOR]

The microcirculation describes the network of the smallest vessels in our cardiovascular system. On a microcirculatory level, oxygen delivery is determined by the flow of oxygen-carrying red blood cells in a given single capillary (capillary red blood cell flow) and the density of the capillary network in a given tissue volume (capillary vessel density). Handheld vital videomicroscopy enables visualisation of the capillary bed on the surface of organs and tissues but currently is only used for research. Measurements are generally possible on all organ surfaces but are most often performed in the sublingual area. In patients presenting for elective surgery, the sublingual microcirculation is usually intact and functional. Induction of general anaesthesia slightly decreases capillary red blood cell flow and increases capillary vessel density. During elective, even major, noncardiac surgery, the sublingual microcirculation is preserved and remains functional, presumably because elective noncardiac surgery is scheduled trauma and haemodynamic alterations are immediately treated by anaesthesiologists, usually restoring the macrocirculation before the microcirculation is substantially impaired. Additionally, surgery is regional trauma and thus likely causes regional, rather than systemic, impairment of the microcirculation. Whether or not the sublingual microcirculation is impaired after noncardiac surgery remains a subject of ongoing research. Similarly, it remains unclear if cardiac surgery, especially with cardiopulmonary bypass, impairs the sublingual microcirculation. The effects of therapeutic interventions specifically targeting the microcirculation remain to be elucidated and tested. Future research should focus on further improving microcirculation monitoring methods and investigating how regional microcirculation monitoring can inform clinical decision-making and treatment. [ABSTRACT FROM AUTHOR]

Flow-directed, balloon-tipped pulmonary artery catheters allow measuring cardiac output and other haemodynamic variables including intracardiac pressures. We propose classifying pulmonary artery catheters by generations and specifying additional measurement modalities. Based on the method used to measure cardiac output, pulmonary artery catheters can be classified into three generations: first-generation using intermittent pulmonary artery thermodilution; second-generation using a thermal filament for automated pulmonary artery thermodilution; and third-generation combining thermal filament-based automated pulmonary artery thermodilution and pulmonary artery pulse wave analysis. Each of these pulmonary artery catheter generations can include additional measurements, such as continuous mixed venous oxygen saturation, right ventricular ejection fraction and end-diastolic volume, and right ventricular pressure. This classification should help define indications for pulmonary artery catheters in clinical practice and research. [ABSTRACT FROM AUTHOR]

'Goal-directed haemodynamic therapy' describes various haemodynamic treatment strategies that have in common that interventions are titrated to achieve predefined haemodynamic targets. However, the treatment strategies differ substantially regarding the underlying haemodynamic target variables and target values, and thus presumably have different effects on outcome. It is an over-simplifying approach to lump complex and substantially differing haemodynamic treatment strategies together under the term 'goal-directed haemodynamic therapy', an imprecise umbrella term that we should thus stop using. [ABSTRACT FROM AUTHOR]

Intraoperative hypotension is associated with myocardial injury, acute kidney injury, and death. In routine practice, specific causes of intraoperative hypotension are often unclear. A more detailed understanding of underlying haemodynamic alterations of intraoperative hypotension may identify specific treatments. We thus aimed to use machine learning – specifically, hierarchical clustering – to identify underlying haemodynamic alterations causing intraoperative hypotension in major abdominal surgery patients. Specifically, we tested the hypothesis that there are distinct endotypes of intraoperative hypotension, which may help refine therapeutic interventions. We conducted a secondary analysis of intraoperative haemodynamic measurements from a prospective observational study in 100 patients who had major abdominal surgery under general anaesthesia. We used stroke volume index, heart rate, cardiac index, systemic vascular resistance index, and pulse pressure variation measurements. Intraoperative hypotension was defined as any mean arterial pressure ≤65 mm Hg or a mean arterial pressure between 66 and 75 mm Hg requiring a norepinephrine infusion rate exceeding 0.1 μg kg−1 min−1. To identify endotypes of intraoperative hypotension, we used hierarchical clustering (Ward's method). A total of 615 episodes of intraoperative hypotension occurred in 82 patients (46 [56%] female; median age: 64 [57, 73] yr) who had surgery of a median duration of 270 (195, 335) min. Hierarchical clustering revealed six distinct intraoperative hypotension endotypes. Based on their clinical characteristics, we labelled these endotypes as (1) myocardial depression , (2) bradycardia , (3) vasodilation with cardiac index increase , (4) vasodilation without cardiac index increase , (5) hypovolaemia , and (6) mixed type. Hierarchical clustering identified six endotypes of intraoperative hypotension. If validated, considering these intraoperative hypotension endotypes may enable causal treatment of intraoperative hypotension. [ABSTRACT FROM AUTHOR]

Retrospective observational studies have reported a significant association between intraoperative hypotension and postoperative morbidity. However, association does not imply causation, and whether preventing intraoperative hypotension can improve patient outcome remains to be demonstrated. In this issue of the British Journal of Anaesthesia , D'Amico and colleagues meta-analysed 10 prospective randomised trials comparing low (≤60 mm Hg) and higher mean arterial pressure targets during anaesthesia and surgery. They did not observe an increase in postoperative morbidity and mortality in the low target group. In contrast, they reported a statistically significant (but not clinically relevant) reduction in postoperative cardiac arrhythmia and hospital length of stay when targeting mean arterial pressure ≤60 mm Hg. These findings suggest that during most surgical cases, intraoperative hypotension is a marker of the severity, frailty, or both rather than a mediator of postoperative complications. [ABSTRACT FROM AUTHOR]

The analysis of arterial pressure waveforms with machine learning algorithms has been proposed to predict intraoperative hypotension. The ability to forecast arterial hypotension 5–15 min ahead of the fall in blood pressure allows clinicians to be pro-active instead of reactive, and could potentially decrease postoperative morbidity. However, the predictive value of machine learning algorithms has been overestimated due to selection bias in several clinical studies, and they might not be superior to mere observation of arterial pressure. Continuous blood pressure monitoring enables immediate detection of hypotension, and giving fluid, vasopressors or inotropes to patients who are not yet (and might never become) hypotensive based on an algorithm is questionable. Finally, recent prospective interventional studies suggest that reducing intraoperative hypotension does not improve postoperative outcomes. [ABSTRACT FROM AUTHOR]

Intraoperative hypotension is common and is associated with adverse postoperative outcomes. A substantial fraction of all perioperative hypotension occurs shortly after induction of anaesthesia and before the procedure begins. Arterial pressure monitoring is usually intermittent in this period, with a risk of missing significant hypotensive events. Continuous blood pressure monitoring might help reduce hypotension. There are now strong arguments that if an arterial line is indicated, it should be placed before induction of anaesthesia to obtain maximal benefit. [ABSTRACT FROM AUTHOR]

Background: Hypotension during induction of anaesthesia is associated with organ injury. Continuous arterial pressure monitoring might help reduce hypotension. We tested the hypothesis that continuous intra-arterial compared with intermittent oscillometric arterial pressure monitoring reduces hypotension during induction of anaesthesia in noncardiac surgery patients.Methods: In this single-centre randomised trial, 242 noncardiac surgery patients in whom intra-arterial arterial pressure monitoring was planned were randomised to unblinded continuous intra-arterial or to intermittent oscillometric arterial pressure monitoring (with blinded intra-arterial arterial pressure monitoring) during induction of anaesthesia. The primary endpoint was the area under a mean arterial pressure (MAP) of 65 mm Hg within the first 15 min of induction of anaesthesia. Secondary endpoints included areas under MAP values of 60, 50, and 40 mm Hg and durations of MAP values <65, <60, <50, and <40 mm Hg.Results: There were 224 subjects available for analysis. The median (25th-75th percentile) area under a MAP of 65 mm Hg was 15 (2-36) mm Hg • min in subjects assigned to continuous intra-arterial monitoring and 46 (7-111) mm Hg • min in subjects assigned to intermittent oscillometric monitoring (P<0.001). Subjects assigned to continuous intra-arterial monitoring had smaller areas under MAP values of 60, 50, and 40 mm Hg and shorter durations of MAP values <65, <60, <50, and <40 mm Hg than subjects assigned to intermittent oscillometric monitoring.Conclusion: Continuous intra-arterial arterial pressure monitoring reduces hypotension during induction of anaesthesia compared with intermittent oscillometric arterial pressure monitoring in noncardiac surgery patients. In patients for whom an arterial catheter is planned, clinicians might therefore consider inserting the arterial catheter before rather than after induction of anaesthesia.Clinical Trials Registration: NCT04894019. [ABSTRACT FROM AUTHOR]

Use of pulmonary artery catheters on general intensive care units has declined. Reasons for this decline are explored and the evidence for and against their use is re-examined. We conclude that the growing consensus for a lack of benefit is not justified, and use of pulmonary artery catheters can still be appropriate. [ABSTRACT FROM AUTHOR]

Purpose: Fluid boluses (FB) are often used in post-cardiac arrest (CA) patients with haemodynamic instability. Although FB may improve cardiac output (CO) and mean arterial pressure (MAP), FB may also increase central venous pressure (CVP), reduce arterial PaO2, dilute haemoglobin and cause interstitial oedema. The aim of the present study was to investigate the net effect of FB administration on cerebral tissue oxygenation saturation (SctO2) in post-CA patients.Methods: Pre-planned sub-study of the Neuroprotect post-CA trial (NCT02541591). Patients with anticipated fluid responsiveness based on stroke volume variation (SVV) or passive leg raising test were administered a FB of 500 ml plasma-lyte A (Baxter Healthcare) and underwent pre- and post-FB assessments of stroke volume, CO, MAP, CVP, haemoglobin, PaO2 and SctO2.Results: 52 patients (mean age 64 ± 12 years, 75% male) received a total of 115 FB. Although administration of a FB resulted in a significant increase of stroke volume (63 ± 22 vs 67 ± 23 mL, p = 0.001), CO (4,2 ± 1,6 vs 4,4 ± 1,7 L/min, p = 0.001) and MAP (74,8 ± 13,2 vs 79,2 ± 12,9 mmHg, p = 0.004), it did not improve SctO2 (68.54 ± 6.99 vs 68.70 ± 6.80%, p = 0.49). Fluid bolus administration also resulted in a significant increase of CVP (10,0 ± 4,5 vs 10,7 ± 4,9 mmHg, p = 0.02), but did not affect PaO2 (99 ± 31 vs 94 ± 31 mmHg, p = 0.15) or haemoglobin concentrations (12,9 ± 2,1 vs 12,8 ± 2,2 g/dL, p = 0.10). In a multivariate model, FB-induced changes in CO (beta 0,77; p = 0.004) and in CVP (beta -0,23; p = 0.02) but not in MAP (beta 0,02; p = 0.18) predicted post-FB ΔSctO2.Conclusions: Despite improvements in CO and MAP, FB administration did not improve SctO2 in post-cardiac arrest patients. [ABSTRACT FROM AUTHOR]

Understanding fluid physiology in homeostasis and disease is a key part of anaesthesia and intensive care. Decision making in perioperative fluid therapy is guided by knowledge of fluid compartments, shifts in illness and surgery and the composition of commonly used intravenous fluids. The implication of poor fluid management has significant outcomes for the patient, with both under-resuscitation and over administration of fluids leading to organ dysfunction and postoperative morbidity and mortality. Increasing use of haemodynamic monitoring within a guideline framework is advised. The evidence base for type of fluid, timing and volume remain areas of investigation and ongoing clinical debate, and it is vital as clinicians involved in perioperative care to continually update our knowledge of this area. Research is currently ongoing to determine whether restrictive, liberal or goal-directed fluid therapy is optimal to guide our practice. In the meantime, advice is to both individualize management to the patient condition and develop local protocols where possible. [ABSTRACT FROM AUTHOR]

The management of the circulation in critically ill patients presents significant challenges. Shock is a potentially reversible life-threatening physiological state characterized by end-organ dysfunction due to an imbalance in oxygen delivery (DO 2) and tissue demand (VO 2). Independent of its aetiology, untreated shock precipitates a cascade of pro-inflammatory mediators resulting in cellular damage and end-organ dysfunction. Thus it is the duty of all clinicians to promptly recognize, diagnose and initiate treatments to halt this process. Despite optimum management, shock can progress to multi-organ failure necessitating critical care admission and advanced haemodynamic management. This article will classify shock syndromes, discuss the principles of diagnosis, use of haemodynamic monitoring and management strategies for circulatory failure in the critically ill patient. [ABSTRACT FROM AUTHOR]

Pulse wave analysis (PWA) allows estimation of cardiac output (CO) based on continuous analysis of the arterial blood pressure (AP) waveform. We describe the physiology of the AP waveform, basic principles of PWA algorithms for CO estimation, and PWA technologies available for clinical practice. The AP waveform is a complex physiological signal that is determined by interplay of left ventricular stroke volume, systemic vascular resistance, and vascular compliance. Numerous PWA algorithms are available to estimate CO, including Windkessel models, long time interval or multi-beat analysis, pulse power analysis, or the pressure recording analytical method. Invasive, minimally-invasive, and noninvasive PWA monitoring systems can be classified according to the method they use to calibrate estimated CO values in externally calibrated systems, internally calibrated systems, and uncalibrated systems. [ABSTRACT FROM AUTHOR]

Background: Transthoracic oesophagectomy is associated with major morbidity and mortality, which may be reduced by goal-directed therapy (GDT). The aim of this multicentre, RCT was to evaluate the impact of intraoperative GDT on major morbidity and mortality in patients undergoing transthoracic oesophagectomy.Methods: Adult patients undergoing transthoracic oesophagectomy were randomised to receive either minimally invasive intraoperative GDT (stroke volume variation <8%, plus systolic BP maintained >90 mm Hg by pressors as necessary) or haemodynamic management left to the discretion of attending senior anaesthetists (control group; systolic BP >90 mm Hg alone). The primary outcome was the incidence of death or major complications (reoperation for bleeding, anastomotic leakage, pneumonia, reintubation, >48 h ventilation). A Cox proportional hazard model was used to examine whether the effects of GDT on morbidity and mortality were independent of other potential confounders.Results: A total of 232 patients (80.6% male; age range: 36-83 yr) were randomised to either GDT (n=115) or to the control group (n=117). After surgery, major morbidity and mortality were less frequent in 22/115 (19.1%) subjects randomised to GDT, compared with 41/117 (35.0%) subjects assigned to the control group {absolute risk reduction: 15.9% (95% confidence interval [CI]: 4.7-27.2%); P=0.006}. GDT was also associated with fewer episodes of atrial fibrillation (odds ratio [OR]: 0.18 [95% CI: 0.05-0.65]), respiratory failure (OR: 0.27 [95% CI: 0.09-0.83]), use of mini-tracheotomy (OR: 0.29 [95% CI: 0.10-0.81]), and readmission to ICU (OR: 0.09 [95% CI: 0.01-0.67]). GDT was independently associated with morbidity and mortality (hazard ratio: 0.51 [95% CI: 0.30-0.87]; P=0.013).Conclusions: Intraoperative GDT may reduce major morbidity and mortality, and shorten hospital stay, after transthoracic oesophagectomy.Clinical Trial Registration: UMIN000018705. [ABSTRACT FROM AUTHOR]

Background: During sepsis, heart rate (HR) reduction could be a therapeutic target, but identification of responders (non-compensatory tachycardia) and non-responders (compensatory for 'fixed' stroke volume [SV]) is challenging. We tested the ability of the difference between systolic and dicrotic pressure (SDPdifference), which reflects the coupling between myocardial contractility and a given afterload, in discriminating the origin of tachycardia.Methods: In this post hoc analysis of 45 patients with septic shock with persistent tachycardia, we characterised features of haemodynamic response focusing on SDPdifference, classifying patients according to variations in arterial dP/dtmax after 4 h of esmolol administration to maintain HR <95 beats min-1. A cut-off value of 0.9 mm Hg ms-1 was used for group allocation.Results: After reducing HR, arterial dP/dtmax remained above the cut-off in 23 patients, whereas it decreased below the cut-off in 22 patients (from 0.99 [0.37] to 0.63 [0.16] mm Hg ms-1; mean [SD], P<0.001). At baseline, patients with decreased dP/dtmax after esmolol had lower SDPdifference than those with higher dP/dtmax (40 [19] vs 53 [16] mm Hg, respectively; P=0.01). The SDPdifference remained unchanged after esmolol in the higher dP/dtmax group (49 [16] mm Hg), whereas it decreased significantly in patients with lower dP/dtmax (29 [11] mm Hg; P<0.001). In the latter, the HR reduction resulted in a significant cardiac output reduction with unchanged SV, whereas in patients with higher dP/dtmax SV increased (from 48 [12] to 67 [14] ml; P<0.001) with maintained cardiac output.Conclusions: A decrease in SDPdifference could discriminate between compensatory and non-compensatory tachycardia, revealing a covert loss of myocardial contractility not detected by conventional echocardiographic parameters and deteriorating after HR reduction with esmolol.Clinical Trial Registration: NCT02188888. [ABSTRACT FROM AUTHOR]

Hyperthermic intraperitoneal chemotherapy (HIPEC) is a surgical technique for peritoneal carcinomatosis combining cytoreduction surgery and peritoneal irrigation of cytotoxic agents responsible for haemodynamics and fluid homeostasis alterations. To this day, no guidelines exist concerning intraoperative management. To review data on haemodynamic monitoring and management of patients undergoing HIPEC and to help design a standardised anaesthetic protocol. MEDLINE, EMBASE and Cochrane library were searched using the following. Original articles and case-reports. Letters to editors and reviews were excluded. Data on haemodynamic management, morbidity and mortality. Haemodynamic management during HIPEC is highly variable and depends on local protocols. Only one randomised controlled trial evaluated the benefit of goal-directed fluid administration (GDFA). GDFA guided by advanced haemodynamic monitoring resulted in significantly less complication, shorter length of stay and less mortality compared to standard fluid administration. Renal protection protocol did not decrease the risk of acute kidney injury (AKI). Our review reveals that fluid administration guided by advanced monitoring seems to be associated with less postoperative morbidity and mortality after HIPEC. Nevertheless, the literature review shows that intraoperative haemodynamic management is highly variable for this surgery. The use of renal protection strategy does not decrease the prevalence of AKI. Further prospective trials comparing different fluid management and haemodynamic monitoring strategies are urgently needed (PROSPERO registration CRD42018115720) [ABSTRACT FROM AUTHOR]

Background: Despite several clinical trials on haemodynamic therapy, the optimal intraoperative haemodynamic management for high-risk patients undergoing major abdominal surgery remains unclear. We tested the hypothesis that personalised haemodynamic management targeting each individual's baseline cardiac index at rest reduces postoperative morbidity.Methods: In this single-centre trial, 188 high-risk patients undergoing major abdominal surgery were randomised to either routine management or personalised haemodynamic management requiring clinicians to maintain personal baseline cardiac index (determined at rest preoperatively) using an algorithm that guided intraoperative i.v. fluid and/or dobutamine administration. The primary outcome was a composite of major complications (European Perioperative Clinical Outcome definitions) or death within 30 days of surgery. Secondary outcomes included postoperative morbidity (assessed by a postoperative morbidity survey), hospital length of stay, mortality within 90 days of surgery, and neurocognitive function assessed after postoperative Day 3.Results: The primary outcome occurred in 29.8% (28/94) of patients in the personalised management group, compared with 55.3% (52/94) of patients in the routine management group (relative risk: 0.54, 95% confidence interval [CI]: 0.38 to 0.77; absolute risk reduction: -25.5%, 95% CI: -39.2% to -11.9%; P<0.001). One patient assigned to the personalised management group, compared with five assigned to the routine management group, died within 30 days after surgery (P=0.097). There were no clinically relevant differences between the two groups for secondary outcomes.Conclusions: In high-risk patients undergoing major abdominal surgery, personalised haemodynamic management reduces a composite outcome of major postoperative complications or death within 30 days after surgery compared with routine care.Clinical Trial Registration: NCT02834377. [ABSTRACT FROM AUTHOR]

Background: Finger cuff technologies allow continuous noninvasive arterial blood pressure (AP) and cardiac output/index (CO/CI) monitoring.Methods: We performed a meta-analysis of studies comparing finger cuff-derived AP and CO/CI measurements with invasive measurements in surgical or critically ill patients. We calculated overall random effects model-derived pooled estimates of the mean of the differences and of the percentage error (PE; CO/CI studies) with 95%-confidence intervals (95%-CI), pooled 95%-limits of agreement (95%-LOA), Cochran's Q and I2 (for heterogeneity).Results: The pooled mean of the differences (95%-CI) was 4.2 (2.8 to 5.62) mm Hg with pooled 95%-LOA of -14.0 to 22.5 mm Hg for mean AP (Q=230.4 [P<0.001], I2=91%). For mean AP, the mean of the differences between finger cuff technologies and the reference method was ≤5±8 mm Hg in 9/27 data sets (33%). The pooled mean of the differences (95%-CI) was -0.13 (-0.43 to 0.18) L min-1 with pooled 95%-LOA of -2.56 to 2.23 L min-1 for CO (Q=66.7 [P<0.001], I2=90%) and 0.07 (0.01 to 0.13) L min-1 m-2 with pooled 95%-LOA of -1.20 to 1.15 L min-1 m-2 for CI (Q=5.8 [P=0.326], I2=0%). The overall random effects model-derived pooled estimate of the PE (95%-CI) was 43 (37 to 49)% (Q=48.6 [P<0.001], I2=63%). In 4/19 data sets (21%) the PE was ≤30%, and in 10/19 data sets (53%) it was ≤45%.Conclusions: Study heterogeneity was high. Several studies showed interchangeability between AP and CO/CI measurements using finger cuff technologies and reference methods. However, the pooled results of this meta-analysis indicate that AP and CO/CI measurements using finger cuff technologies and reference methods are not interchangeable in surgical or critically ill patients.Clinical Trial Number: PROSPERO registration number: CRD42019119266. [ABSTRACT FROM AUTHOR]

Introduction: During rapid response team (RRT) management of haemodynamic instability (HI), continuous non-invasive haemodynamic monitoring may provide supplemental physiological information.Objectives: To continuously and non-invasively obtain the cardiac index (CI) and mean arterial pressure (MAP) in patients with HI at baseline and during RRT management using the ClearSight™ device.Methods: We performed a prospective observational study in adult patients managed by the RRT for tachycardia or hypotension or both. We assessed changes from baseline in heart rate (HR), MAP, CI, stroke volume index (SVI) and systemic vascular resistance index (SVRI) (i) at 5-minutely intervals up to 20 min, and (ii) over the entire 20-min period. We analysed patients by RRT trigger (tachycardia/hypotension) and intervention (fluid bolus therapy [FBT]/ no FBT).Results: We successfully recorded the CI in 47 of 50 (94%) patients. RRT reviews triggered by hypotension rather than tachycardia had a lower baseline HR (-45.4 bpm, p = <0.0001), MAP (-16.1 mmHg, p = 0.0007) and CI (1.0 L/min/m2, p = 0.0025). Compared to baseline, in the tachycardia group, there was a small increase in MAP overall and at the 15-20 min time-block from 83.2 mmHg to 87.1 mmHg (+3.9 mmHg, p = 0.0066) and 85.5 mmHg (+2.3 mmHg, p = 0.0061), respectively. In those who received FBT, there was a statistically significant increase in MAP overall and at the 15-20 min time-block compared to baseline, from 70.1 mmHg to 73.5 mmHg (+3.4 mmHg, p = 0.0036) and 74.3 mmHg (+4.2 mmHg, p = 0.0037), respectively. However, there were no statistically significant changes in mean HR, CI, SVI, or SVRI when comparing baseline to the entire 20-min period or 5-min time-blocks within any group.Conclusions: Continuous non-invasive measurement of haemodynamics during RRT management for HI was possible for 20 min. Patients with hypotension rather than tachycardia had lower baseline HR, MAP and CI values. There was a statistically significant but small increase in MAP at the 15-20 min time-block and overall, for both the tachycardia and FBT groups. [ABSTRACT FROM AUTHOR]

Less invasive or even completely non-invasive haemodynamic monitoring technologies have evolved during the last decades. Even established, invasive devices such as the pulmonary artery catheter and transpulmonary thermodilution have still an evidence-based place in the perioperative setting, albeit only in special patient populations. Accumulating evidence suggests to use continuous haemodynamic monitoring, especially flow-based variables such as stroke volume or cardiac output to prevent occult hypoperfusion and, consequently, decrease morbidity and mortality perioperatively. However, there is still a substantial gap between evidence provided by randomised trials and the implementation of haemodynamic monitoring in daily clinical routine. Given the fact that perioperative morbidity and mortality are higher than anticipated and anaesthesiologists are in charge to deal with this problem, the recent advances in minimally invasive and non-invasive monitoring technologies may facilitate more widespread use in the operating theatre, as in addition to costs, the degree of invasiveness of any monitoring tool determines the frequency of its application, at least perioperatively. This review covers the currently available invasive, non-invasive and minimally invasive techniques and devices and addresses their indications and limitations. [ABSTRACT FROM AUTHOR]

The impact of positive pressure ventilation extends the effect on lungs and gas exchange because the altered intra-thoracic pressure conditions influence determinants of cardiovascular function. These mechanisms are called heart-lung interactions, which conceptually can be divided into two components (1) The effect of positive airway pressure on the cardiovascular system, which may be more or less pronounced under various pathologic cardiac conditions, and (2) The effect of cyclic airway pressure swing on the cardiovascular system, which can be useful in the interpretation of the individual patient's current haemodynamic state. It is imperative for the anaesthesiologist to understand the fundamental mechanisms of heart-lung interactions, as they are a foundation for the understanding of optimal, personalised cardiovascular treatment of patients undergoing surgery in general anaesthesia. The aim of this review is thus to describe what the anaesthesiologist needs to know about heart-lung interactions. [ABSTRACT FROM AUTHOR]

Abstract The management of the circulation in critically ill patients presents significant challenges. Shock is a potentially reversible life-threatening physiological state characterized by end-organ dysfunction due to an imbalance in oxygen delivery (DO 2) and tissue demand (VO 2). Independent of its aetiology, untreated shock precipitates a cascade of pro-inflammatory mediators resulting in cellular damage and end-organ dysfunction. Thus it is the duty of all clinicians to promptly recognize, diagnose and initiate treatments to halt this process. Despite optimum management, shock can progress to multi-organ failure necessitating critical care admission and advanced haemodynamic management. This article will classify shock syndromes, discuss the principles of diagnosis, use of haemodynamic monitoring and management strategies for circulatory failure in the critically ill patient. [ABSTRACT FROM AUTHOR]

Understanding fluid physiology in homeostasis and disease is a key part of anaesthesia and intensive care. Decision making in perioperative fluid therapy is guided by knowledge of fluid compartments, shifts in illness and surgery and the composition of commonly used intravenous fluids. The implication of poor fluid management has significant outcomes for the patient, with both under-resuscitation and over administration of fluids leading to organ dysfunction and postoperative morbidity and mortality. Increasing use of haemodynamic monitoring within a guideline framework is advised. The evidence base for type of fluid, timing, and volume remain areas of investigation and ongoing clinical debate and it is vital as clinicians involved in perioperative care to continually update our knowledge of this area. Research is currently ongoing to determine whether restrictive, liberal or goal-directed fluid therapy is optimal to guide our practice. In the meantime, advice is to both individualize management to the patient condition and develop local protocols where possible. [ABSTRACT FROM AUTHOR]

Objective To evaluate the ability of a noninvasive cardiac output monitoring system with electrical velocimetry (EV) for predicting fluid responsiveness in dogs undergoing cardiac surgery. Study design Prospective experimental trial. Animals A total of 30 adult Beagle dogs. Methods Stroke volume (SV), stroke volume variation (SVV) and cardiac index were measured using the EV device in sevoflurane-anaesthetized, mechanically ventilated dogs undergoing thoracotomies for experimental creation of right ventricular failure. The dogs were considered fluid responsive if stroke volume (SVI; indexed to body weight), measured using pulmonary artery thermodilution, increased by 10% or more after volume loading (10 mL kg-1). Relationships of SVV, central venous pressure (CVP) and pulmonary artery occlusion pressure (PAOP) with SVI were analysed to estimate fluid responsiveness. Results Better prediction of fluid responsiveness, with a significant area under the receiver operating characteristic curve, was observed for SVV (0.85 ± 0.07; p = 0.0016) in comparison with CVP (0.65 ± 0.11; p = 0.17) or PAOP (0.60 ± 0.12; p = 0.35), with a cut-off value of 13.5% (84% specificity and 73% sensitivity). Conclusions and clinical relevance SVV derived from EV is useful for identification of dogs that are likely to respond to fluids, providing valuable information on volume status under cardiothoracic anaesthesia. [ABSTRACT FROM AUTHOR]

Objective To compare electrical velocimetry (EV) noninvasive measures of cardiac output (CO) and stroke volume variation (SVV) in dogs undergoing cardiovascular surgery with those obtained with the conventional thermodilution technique using a pulmonary artery catheter. Study design Prospective experimental trial. Animals Seven adult Beagle dogs with a median weight of 13.6 kg. Methods Simultaneous, coupled cardiac index (CI; CO indexed to body surface area) measurements by EV (CIEV) and the reference pulmonary artery catheter thermodilution method (CIPAC) were obtained in seven sevoflurane-anaesthetized, mechanically ventilated dogs undergoing experimental open-chest cardiovascular surgery for isolated right ventricular failure. Relationships between SVV or central venous pressure (CVP) and stroke volume (SV) were analysed to estimate fluid responsiveness. Haemodynamic data were recorded intraoperatively and before and after fluid challenge. Results BlandeAltman analysis of 332 matched sets of CI data revealed an overall bias and precision ofe 0.22 ± 0.52 L minute-1m-2 for CIEV and CIPAC (percentage error: 30.4%). Trend analysis showed a concordance of 88% for CIEV. SVV showed a significant positive correlation (r² = 0.442, p < 0.0001) with SV changes to a volume loading of 200 mL, but CVP did not (r² = 0.0002, p = 0.94). Better prediction of SV responsiveness (rise of SV index of ≥ 10%) was observed for SVV (0.74 ± 0.09; p=0.014) with a significant area under the receiver operating characteristic curve in comparison with CVP (0.53 ± 0.98; p = 0.78), with a cut-off value of 14.5% (60% specificity and 83% sensitivity). Conclusions and clinical relevance In dogs undergoing cardiovascular surgery, EV provided accurate CO measurements compared with CIPAC, although its trending ability was poor. Further, SVV by EV, but not CVP, reliably predicted fluid responsiveness during mechanical ventilation in dogs. [ABSTRACT FROM AUTHOR]

Over the last decade, there has been an increased interest in the use of goal-directed therapy (GDT) in patients undergoing high-risk surgery, and various haemodynamic monitoring tools have been developed to guide perioperative care. Both the complexity of the patient and surgical procedure need to be considered when deciding whether GDT will be beneficial. Ensuring optimum tissue perfusion is paramount in the perioperative period and relies on the coherence between both macrovascular and microvascular circulations. Although global haemodynamic parameters may be optimised with the use of GDT, microvascular impairment can still persist. This review will provide an overview of both haemodynamic optimisation and microvascular assessment in the perioperative period. [ABSTRACT FROM AUTHOR]

Over the past decades, there has been considerable progress in the field of less invasive haemodynamic monitoring technologies. Substantial evidence has accumulated, which supports the continuous measurement and optimization of flow-based variables such as stroke volume, that is, cardiac output, in order to prevent occult hypoperfusion and consequently to improve patients' outcome in the perioperative setting. However, there is a striking gap between the developments in haemodynamic monitoring and the increasing evidence to implement defined treatment protocols based on the measured variables, and daily clinical routine. Recent trials have shown that perioperative morbidity and mortality is higher than anticipated. This emphasizes the need for the anaesthesia community to address this issue and promotes the implementation of proven concepts into clinical practice in order to improve patients' outcome, especially in high-risk patients. The advances in minimally invasive and non-invasive monitoring techniques can be seen as a driving force in this respect, as the degree of invasiveness of any monitoring tool determines the frequency of its application, especially in the operating room (OR). From this point of view, we are very confident that some of these minimally invasive and non-invasive haemodynamic monitoring technologies will become an inherent part of our monitoring armamentarium in the OR and in the intensive care unit (ICU). [ABSTRACT FROM AUTHOR]

Haemodynamics is the measurement of the circulation within the body. Shock exists when the perfusion of vital organs is inadequate. The use of haemodynamic monitoring aims to identify hypoperfusion early, and allow for its correction in a timely manner, before irreversible organ dysfunction occurs. This article outlines the basic physiology of the circulation and the mechanisms of different forms of shock. Current invasive and non-invasive methods of haemodynamic monitoring are described, such as may be encountered in theatre or in the Critical Unit. [ABSTRACT FROM AUTHOR]

The management of the circulation in critically ill patients presents significant challenges. Shock is a potentially reversible life threatening physiological state characterized by end organ dysfunction due to an imbalance in oxygen delivery (DO 2 ) and tissue demand (VO 2 ). Independent of its aetiology, untreated shock precipitates a cascade of pro-inflammatory mediators resulting in cellular damage and end organ dysfunction. Thus it is the duty of all clinicians to promptly recognize, diagnose and initiate treatments to halt this process. Despite optimum management shock can progress to multi-organ failure necessitating critical care admission and advanced haemodynamic management. This article will classify shock syndromes, discuss the principles of diagnosis, use of haemodynamic monitoring and management strategies for circulatory failure in the critically ill patient. [ABSTRACT FROM AUTHOR]

Background Evidence for the benefit of an intraoperative use of a goal-directed haemodynamic management has grown. We compared the oesophageal Doppler monitor (ODM, CardioQ-ODM™) with a calibrated pulse contour analysis (PCA, PiCCO2™) with regard to assessment of stroke volume (SV) changes after volume administration within a goal-directed haemodynamic algorithm during non-cardiac surgery. Methods The data were obtained prospectively in patients with metastatic ovarian carcinoma undergoing cytoreductive surgery. During surgery, fluid challenges were performed as indicated by the goal-directed haemodynamic algorithm guided by the ODM. Monitors were compared regarding precision and trending. Clinical characteristics associated with trending were studied by extended regression analysis. Results A total of 762 fluid challenges were performed in 41 patients resulting in 1524 paired measurements. The precision of ODM and PCA was 5.7% and 6.0% (P=0.80), respectively. Polar plot analysis revealed a poor trending between ODM and PCA with an angular bias of −7.1°, radial limits of agreement of −58.1° to 43.8°, and an angular concordance rate of 67.8%. Dose of norepinephrine (NE) (scaled 0.1 µg kg−1 min−1) [adjusted odds ratio (OR) 0.606 (95% confidence interval, CI: 0.404–0.910); P=0.016] and changes in mean arterial pressure (MAP) to a fluid challenge (scaled 10%) [adjusted OR 0.733 (95% CI: 0.635–0.845); P<0.001] were associated with trending between ODM and PCA, whereas there was no relation to type of i.v. solution. Conclusions Despite a similar precision, ODM and PCA were not interchangeable with regard to measuring SV changes within a goal-directed haemodynamic algorithm. A decrease in interchangeability coincided with increasing NE levels and greater changes of MAP to a fluid challenge. [ABSTRACT FROM AUTHOR]

Background Cardiac output monitoring, as a part of a goal-directed haemodynamic management, has been shown to improve perioperative outcome in high-risk patients undergoing major surgical interventions. However, thorough validation of cardiac output monitoring devices in different clinical conditions is warranted. The aim of our study was to compare the reliability of a novel system for cardiac index (CI) monitoring based on uncalibrated pulse contour analysis (UPCA) with transpulmonary thermodilution (TPTD) during off-pump coronary artery bypass grafting (OPCAB). Methods Twenty patients undergoing elective OPCAB were enrolled into the study. CI measured by means of UPCA (CIUPCA) was validated against CI determined with TPTD technique (CITPTD). Parallel measurements of CI were performed at nine stages during the surgery and after operation. We assessed the accuracy and the precision of individual values and the agreement of trends of changes in CI. Results Totally, 180 pairs of data were collected. There was a significant correlation between CIUPCA and CITPTD (ρ=0.836, P<0.01). According to a Bland–Altman analysis, the mean bias between the methods was −0.14 litre min−1 m−2 with limits of agreement of ±0.82 litre min−1 m−2 and a percentage error of 31%. A polar plot trend analysis revealed acceptable angular bias (−0.54°), increased radial limits of agreement (±52.7°), and decreased polar concordance rate (74%). Conclusions In OPCAB, UPCA provides accurate and precise CI measurements compared with TPTD. However, the ability of this method to follow trends in cardiac output is poor. Clinical trial registration NCT01773720 (ClinicalTrials.gov). [ABSTRACT FROM AUTHOR]

Patients with limited cardiopulmonary reserve are at risk of mortality and morbidity after major surgery. Augmentation of oxygen delivery index (DO2I) with i.v. fluids and inotropes (goal-directed therapy, GDT) has been shown to reduce postoperative mortality and morbidity in high-risk patients. Concerns regarding cardiac complications associated with fluid challenges and inotropes may prevent clinicians from performing GDT in patients who need it most. We hypothesized that GDT is not associated with an increased risk of cardiac complications in high-risk, non-cardiac surgical patients. We performed a systematic search of Medline, Embase, and CENTRAL databases for randomized controlled trials (RCTs) of GDT in high-risk surgical patients. Studies including cardiac surgery, trauma, and paediatric surgery were excluded. We reviewed the rates of all cardiac complications, arrhythmias, myocardial ischaemia, and acute pulmonary oedema. Meta-analyses were performed using RevMan software. Data are presented as odds ratios (ORs), [95% confidence intervals (CIs)], and P-values. Twenty-two RCTs including 2129 patients reported cardiac complications. GDT was associated with a reduction in total cardiovascular (CVS) complications [OR=0.54, (0.38–0.76), P=0.0005] and arrhythmias [OR=0.54, (0.35–0.85), P=0.007]. GDT was not associated with an increase in acute pulmonary oedema [OR=0.69, (0.43–1.10), P=0.12] or myocardial ischaemia [OR=0.70, (0.38–1.28), P=0.25]. Subgroup analysis revealed the benefit is most pronounced in patients receiving fluid and inotrope therapy to achieve a supranormal DO2I, with the use of minimally invasive cardiac output monitors. Treatment of high-risk surgical patients GDT is not associated with an increased risk of cardiac complications; GDT with fluids and inotropes to optimize DO2I during early GDT reduces postoperative CVS complications. [ABSTRACT FROM PUBLISHER]

Background Respiratory variation in pulse pressure (ΔPP) is commonly used to predict the fluid responsiveness of critically ill patients. However, some researchers have demonstrated that this measurement has several limitations. The present study was designed to evaluate the proportion of patients satisfying criteria for valid application of ΔPP at a given time-point. Methods A 1 day, prospective, observational, point-prevalence study was performed in 26 French intensive care units (ICUs). All patients hospitalized in the ICUs on the day of the study were included. The ΔPP validity criteria were recorded prospectively and defined as follows: (i) mechanical ventilation in the absence of spontaneous respiration; (ii) regular cardiac rhythm; (iii) tidal volume ≥8 ml kg−1 of ideal body weight; (iv) a heart rate/respiratory rate ratio >3.6; (v) total respiratory system compliance ≥30 ml cm H2O−1; and (vi) tricuspid annular peak systolic velocity ≥0.15 m s−1. Results The study included 311 patients with a Simplified Acute Physiology Score II of 41 (39–43). Overall, only six (2%) patients satisfied all validity criteria. Of the 170 patients with an arterial line in place, only five (3%) satisfied the validity criteria. During the 24 h preceding the study time-point, fluid responsiveness was assessed for 79 patients. ΔPP had been used to assess fluid responsiveness in 15 of these cases (19%). Conclusions A very low percentage of patients satisfied all criteria for valid use of ΔPP in the evaluation of fluid responsiveness. Physicians must consider limitations to the validity of ΔPP before using this variable. [ABSTRACT FROM PUBLISHER]

Haemodynamic monitoring has developed considerably over the last decades, nowadays comprising a wide spectrum of different technologies ranging from invasive to completely non-invasive techniques. At present, the evidence to continuously measure and optimise stroke volume, that is, cardiac output, in order to prevent occult hypoperfusion in the perioperative setting and consequently to improve patients' outcome is substantial. Surprisingly, there is a striking discrepancy between the developments in advanced haemodynamic monitoring combined with evidence-based knowledge on the one hand and daily clinical routine on the other hand. Recent trials have shown that perioperative mortality is higher than anticipated, emphasising the need for the speciality of anaesthesiology to face the problem and to translate proven concepts into clinical routine to improve patients' outcome. One basic principle of these concepts is to monitor and to optimise cardiac function by means of advanced haemodynamic monitoring, using echocardiography, pulse contour analysis and beyond. [Copyright &y& Elsevier]

Abstract: INTRODUCTION: The diagnosis of intraoperative anaphylaxis is important but can be difficult as the symptoms can be varying and dependent on patient factors. PRESENTATION OF CASE: We describe an acute, unexpected and life threatening cardiovascular (CV) collapse, presumed to be due to an acute anaphylactic reaction secondary to gelatin administration, following induction of general anaesthesia (GA), in an ASA 3 patient scheduled for axillo-bifemoral bypass. DISCUSSION: The management of the profound cardiovascular (CV) collapse was greatly assisted by sophisticated haemodynamic, depth of anaesthesia and cerebral oximetry monitoring.1 As far as we are aware this is the first such case where the full haemodynamic, depth of anaesthesia and cerebral oxygenation changes during CV collapse, presumed due to an acute anaphylactic reaction under GA have been fully documented. CONCLUSION: The use of advanced monitoring intraoperatively proved extremely useful in guiding the resuscitation of a life threatening allergic reaction under general anaesthesia. [Copyright &y& Elsevier]

Background Controversy exists regarding the optimal i.v. fluids for use with a goal-directed haemodynamic algorithm. Methods In a double-blind pilot study, we randomly assigned 50 patients with primary ovarian cancer undergoing cytoreductive surgery to receive either balanced crystalloid or balanced starch (HES, 130/0.4, 6%) solutions up to the dose limit (50 ml kg−1). Fluids were administered to optimize stroke volume measured by oesophageal Doppler within a goal-directed haemodynamic algorithm. Results Baseline subject characteristics were similar in both groups. The balanced HES solution maintained stroke volume (P=0.012) better with administration of less fluid. Subjects in the colloid group reached the dose limits of the study medication less frequently (92% vs 62%, P=0.036) and later (2:26 vs 3:33 h, P=0.006) and also required less transfusion of fresh-frozen plasma units (6.0 vs 3.5 units, P=0.035) compared with the crystalloid group. Intra- and postoperative urine output and perioperative plasma levels of creatinine and neutrophil gelatinase-associated lipocalin as renal injury marker were similar in both groups. No differences in the length of intensive care unit and hospital stay were found. Conclusions Using a goal-directed haemodynamic algorithm to optimize stroke volume, a balanced HES solution is associated with better haemodynamic stability and reduced need for fresh-frozen plasma. There were no signs of renal impairment by colloid solutions when fluid administration is targeted to optimize cardiac preload. [ABSTRACT FROM AUTHOR]

Abstract: The management of the circulation in critically ill patients presents significant challenges. Shock is a potentially reversible life-threatening physiological state characterized by end organ dysfunction due to an imbalance in oxygen delivery (DO2) and tissue demand (VO2). Independent of its aetiology, untreated shock precipitates a cascade of pro-inflammatory mediators causing cellular damage and end organ dysfunction.1 Thus it is the duty of the surgical team to promptly recognize, diagnose and initiate treatments to halt this process. Despite optimum management shock can progress to multi-organ failure necessitating critical care admission and advanced haemodynamic management. This article will classify shock syndromes, discuss the principles of diagnosis, use of haemodynamic monitoring and management strategies for circulatory failure in the critically ill patient. [Copyright &y& Elsevier]

Abstract: Purpose: Haemodynamic optimisation is a fundamental goal of post-cardiac arrest therapy. Therefore, predicting volume responsiveness is a key issue in therapy of these high-risk patients and transoesophageal echocardiography (TEE) may provide helpful information. The aim of the present study was to evaluate the performance of visual evaluation (eyeballing) of standardised TEE-loops to predict volume responsiveness during post-cardiac arrest period. Methods: After approval of the local animal investigation committee, TEE mid-oesophageal long-axis views were recorded before a 5ml/kg volume bolus at baseline and both 1 and 4h after return of spontaneous circulation (ROSC) from 8min electrically induced cardiac arrest. Post-hoc, TEE loops were independently presented in randomized order to 7 blinded TEE-experts and 14 blinded TEE novices who were asked to predict whether the ventricle will increase stroke volume ≥15% after volume loading or not. Statistics were performed calculating sensitivity and specificity for the correct evaluation and agreement of raters. Results: 14 out of 20 pigs were successfully resuscitated, and 924 ratings from 21 echocardiographers were included into analysis. Overall, we observed a sensitivity between 71 and 100%, whereas the specificity showed rather low values between 0 and 67% for prediction of volume responsiveness. Best prediction was recorded 1h after ROSC with median sensitivity (95% CI) of 100% (89–100%) and median specificity of 67% (61–72%). No significant difference was found between ratings of experienced and inexperienced echocardiographers. The concordance rate within the two groups was comparable. Conclusions: In post-cardiac arrest period, visual evaluation of long-axis TEE loops allows prediction of volume responsiveness with good sensitivity and reasonable specificity even by novice users, and may therefore be suitable for implementation into treatment protocols. [Copyright &y& Elsevier]

Background Pulse-contour analysis method (PCM) cardiac output (CO) monitors are increasingly used for CO monitoring during anaesthesia and in the critically ill. Very recently, several systems have been introduced that do not need calibration; among them the pressure recording analytical method (PRAM). Sparse data comparing the accuracy of the PRAM-CO with conventional thermodilution CO (ThD-CO) in cardiac surgery patients are available. Methods In this prospective comparison study, paired CO measurements with a pulmonary artery catheter and a PRAM monitoring set were obtained 20–30 min apart (t1, t2) in 23 extubated patients on the first postoperative day after cardiac surgery. Data were analysed by the Bland–Altman method. Results A total of 46 paired CO measurements (23 for each interval) were collected. The Bland–Altman analysis showed a mean difference (bias) of 0.0 litre min−1 and limits of agreement (1.96 sd) of 4.53 to −4.54 litre min−1 [upper 95% confidence interval (CI), 3.26–5.80; lower 95% CI, −5.8 to −3.27]. The percentage error (1.96 sd/mean of the reference method) was 87%. Conclusions These results question the reliability of the PRAM technology for the determination of CO in postoperative cardiac surgery patients. [ABSTRACT FROM AUTHOR]

Background The functional haemodynamic variables pulse pressure variation (PPV), stroke volume variation (SVV), and systolic pressure variation (SPV) are widely used to assess haemodynamic status. However, it is not known how these perform during acute lung injury (ALI). This study evaluated the effects of different ventilatory strategies on haemodynamic parameters in pigs with ALI during normovolaemia and hypovolaemia. Methods Eight anaesthetized Agroceres pigs [40 (1.9) kg] were instrumented with pulmonary artery, PiCCO, and arterial catheters and ventilated. Three ventilatory settings were randomly assigned for 10 min each: tidal volume (VT) 15 ml kg−1 and PEEP 5 cm H2O, VT 8 ml kg−1 and PEEP 13 cm H2O, or VT 6 ml kg−1 and PEEP 13 cm H2O. Data were collected at each setting at baseline, after ALI (lung lavage+Tween 1.5%), and ALI with hypovolaemia (haemorrhage to 30% of estimated blood volume). Results At baseline, high VT increased PPV, SVV, and SPV (P<0.05 for all). During ALI, high VT significantly increased PPV and SVV [(P = 0.002 and P = 0.008) respectively.]. After ALI with hypovolaemia, ventilation at VT 6 ml kg−1 and PEEP 13 cm H2O decreased the accuracy of functional haemodynamic variables to predict hypovolaemia, with the exception of PPV (area under the curve 0.875). The parameters obtained by PiCCO were less influenced by ventilatory changes. Conclusions VT is the ventilatory parameter which influences functional haemodynamics the most. During ventilation with low VT and high PEEP, most functional variables are less able to accurately predict hypovolaemia secondary to haemorrhage, with the exception of PPV. [ABSTRACT FROM AUTHOR]