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Background Myocardial ischemia may be considered both a consequence of weaning from ventilation and a potential cause of weaning failure. A limited number of investigations have evaluated myocardial ischemia during mechanical ventilation and weaning and its effect on weaning success. The purpose of this pilot investigation was to determine the prevalence of myocardial ischemia in a diverse group of medical intensive care unit (MICU) patients during baseline mechanical ventilation, during weaning using continuous positive airway pressure, and up to 24 hours after extubation and to evaluate the relationship between ischemia and weaning failure. Methods This study was a prospective, repeated-measure, descriptive investigation that studied 43 ventilated MICU patients. Slightly more than half of participants were male (53%), and participants had a mean age of 51.1 ± 14.6 years and were ventilated an average of 11.7 ± 11.3 days. Myocardial ischemia was evaluated by examination of plasma cardiac troponin I, creatine phosphokinase–myocardial band (CK-MB), and ST-segment changes on electrocardiogram. Continuous electrocardiographic data were obtained by a calibrated, frequency-modulated, continuous 3-channel electrocardiographic recorder using leads I, II, and V2. Results Seventy percent of these participants ( n = 30) exhibited ST-segment deviation at some point during data collection (baseline mechanical ventilation, during weaning, after extubation). Twenty-four participants exhibited ST-segment deviation at baseline, 7 during weaning, and 8 after extubation. Nine participants exhibited ST-segment deviation at >1 data collection time point. None had ST-segment deviation at all 3 time points. Cardiac enzyme concentrations were highly variable; five participants demonstrated clinically important increases in either CK-MB and/or troponin I. Thirty-five percent of participants required >1 weaning trial. Participants who exhibited ST-segment deviation during baseline ventilation were 60% more likely to fail their initial weaning trial. There were no significant differences in CK-MB or troponin I levels between those participants who were successfully weaned with 1 trial and those who failed to wean during that first trial. Conclusions Silent myocardial ischemia was a common occurrence in this diverse group of MICU patients, although only 21% had previously diagnosed coronary disease. Clinicians must be aware of the potential for silent ischemia, monitor and evaluate their patients for such, and intervene to promote optimal cardiovascular function, particularly during the stress of ventilator weaning.

• Background Cardiac dysfunction can prevent successful discontinuation of mechanical ventilation. Critically ill patients may have undetected cardiac disease, and cardiac dysfunction can be produced or exacerbated by underlying pathophysiology. • Objective To describe and compare hemodynamic function and cardiac rhythm during baseline mechanical ventilation with function and rhythm during a trial of continuous positive airway pressure in medical intensive care patients. • Methods A convenience sample of 43 patients (53% men; mean age 51.1 years) who required mechanical ventilation were recruited for this pilot study. Cardiac output, stroke volume, arterial blood pressure, heart rate, cardiac rhythm, and plasma catecholamine levels were measured during mechanical ventilation and during a trial of continuous positive airway pressure. • Results One third of the patients had difficulty discontinuing mechanical ventilation. Successful patients had significantly increased cardiac output and stroke volume without changes in heart rate or arterial pressure during the trial of continuous positive airway pressure. Unsuccessful patients had no significant changes in cardiac output, stroke volume, or heart rate but had a significant increase in mean arterial pressure. The 2 groups of patients also had different patterns in ectopy. Concurrently, catecholamine concentrations decreased in the successful patients and significantly increased in the unsuccessful patients during the trial. • Conclusions Patterns of cardiac function and plasma catecholamine levels differed between patients who did or did not achieve spontaneous ventilation with a trial of continuous positive airway pressure. Cardiac function must be systematically considered before and during the return to spontaneous ventilation to optimize the likelihood of success.

An open system of delivery of supplemental oxygen was compared with a closed system during endotracheal suction (ETS) at zero end-expiratory pressure (ZEEP) and 10 cm H2O positive end-expiratory pressure (PEEP). Four protocols in a 2 x 2 design were administered in random order to 12 anesthetized and oleic acid-injured animals. Statistically significant differences were found between protocols for arterial carbon dioxide tension (PaCO2), arterial oxygen saturation (SaO2), airway pressure (Paw), right atrial pressure (Pra), intrathoracic pressure (Pit), arterial pressure, and right ventricular afterload. Intrathoracic pressure and systolic aortic pressure differed between open and closed systems. Statistically significant differences between ZEEP and PEEP were found for PaCO2, SaO2, Paw, Pra, Pit, aortic pressure, and right ventricular afterload. Suctioning through a closed system made little difference in subject responses, but clinically significant differences existed when suctioning subjects on and off PEEP.

Pulmonary aspiration of gastric contents is the most serious complication of tube feeding. However, little consensus exists on how frequently it occurs in patients receiving mechanical ventilation because researchers who studied this problem used widely varied definitions of aspiration and methods for its detection. A well-controlled study by Torres et al1 suggested that aspiration occurs in 32% of patients receiving mechanical ventilation when the patients are semirecumbent and in 68% when they are supine. Aspiration of gastric contents has numerous deleterious consequences, including transient hypoxemia, chemical pneumonitis, and potentially life-threatening nosocomial pneumonia. Aspiration of gastric contents is one cause of ventilator-associated pneumonia, a condition that increases duration of mechanical ventilation, length of hospital stays, and use of medical resources. In a study2 of 120 critically ill patients receiving mechanical ventilation, patients with ventilator-associated pneumonia had a 16-day greater length of stay and almost a $30000 greater cost per case than did patients without pneumonia. Although observed single aspirations of a large volume of gastric contents sometimes occur, most tube-fed patients experience repeated unobserved aspirations of small volumes of gastric contents that can ultimately lead to pneumonia.3 Clinicians try to detect aspiration early so that interventions can be implemented to prevent further aspiration events and poor outcomes. In clinical settings, methods used to detect aspiration of tube feedings include (1) adding food dye to the enteral formula and then observing for dye-stained tracheal secretions and (2) using glucose oxidase reagent strips to test tracheal secretions for the presence of glucose-rich formula. Unfortunately, neither method is wholly satisfactory.4 For example, the sensitivity and safety of the dye method5-7 and the specificity of the glucose method8,9 have been questioned. Therefore, the search for effective, yet harmless, clinical methods to detect aspiration of gastric contents should continue. Because pepsin is plentiful in gastric juice, but not in tracheal secretions, several groups of investigators have suggested that pepsin would be a good marker or indicator for the aspiration of gastric juice.10,11 To test this hypothesis, Ufberg et al11 used unspecified methods to detect pepsin in specimens of gastric fluid and tracheal secretions obtained from 10 fasting preoperative patients. All 10 of the gastric specimens tested positive for pepsin, and all 10 of the tracheal specimens were negative. Ufberg et al concluded that a pepsin assay is a promising tool for the diagnosis of occult pulmonary aspiration of gastric contents. Using a pepsin assay developed by Anson12 (a method in which proteolytically active pepsin is allowed to digest a known quantity of hemoglobin), Badellino et al10 tested the same hypothesis in an animal model. Human gastric juice (2 mL/kg) was instilled intratracheally into 24 rabbits; similar volumes of isotonic sodium chloride solution were instilled intratracheally in 10 control rabbits. Bronchoalveolar lavage was performed 15 minutes, 30 minutes, or 60 minutes after the instillation of fluid. In the rabbits given human gastric juice, peptic activity was detected in the lavage fluid in 8 of 8 animals at 15 minutes, 6 of 8 at 30 minutes, and 5 of 8 at 60 minutes. Because the Anson method relies on the presence of proteolytically active pepsin to digest a hemoglobin substrate, it cannot be used to detect pepsin that has been degraded in the alkaline environment of the lung. This factor explains why fewer specimens tested positive for pepsin at the 30- and 60-minute times. No peptic activity was present in lavage fluid from control animals at any time. In another study,13 the Anson method was used to assay for pepsin in 102 specimens of tracheal secretions collected from acutely ill human subjects. Only 2 of the 102 specimens contained sizeable amounts of pepsin (66.2 and 83.1 μg/mL). Because a variety of other proteins in addition to pepsin are detected with the Anson method, these values may be overestimations of the actual amount of pepsin in the 2 samples.

Background Closed-system suction catheters (CSSC) were designed to eliminate the need to disconnect the patient from the ventilator during endotracheal suctioning (ETS). During data collection on an NIH-funded study, it was noted that moisture accumulated on the inside of the CSSC and sleeve when attached to the patient for 30 minutes. Because CSSC are not disconnected, they present unique methodologic problems related to measurement of secretions as a dependent variable in clinical research. Objectives To describe a valid, reliable, and practical method for weighing secretions obtained during ETS using a CSSC; and to determine the change in weight of a CSSC after its attachment for 30 minutes to a mechanically ventilated patient. Methods After being weighed, a CSSC and sputum trap were attached to the endotracheal tube of a mechanically ventilated adult and remained attached for 43 minutes (30 minutes to allow positive end expiratory pressure and oxygenation levels to return to normal and 13 minutes to mimic the time frame for the ETS procedure used in another study). No ETS occurred. The CSSC and sputum trap were then removed and reweighed. Results A convenience sample consisted of 50 adults who were critically ill and mechanically ventilated. Independent variables included tidal volume, pressure support, body temperature, and respiratory rate. The dependent variable was wet weight of the CSSC, determined by subtracting the preprotocol catheter weight from the postprotocol catheter weight. The mean wet weight for all catheters was 0.5142 +/- 0.1215 grams. In a subset of 37 patients, two wet weights (74 paired observations) were determined. The mean wet weight for these catheters was 0.54014 +/- 0.1404 grams. The paired wet weights were statistically different (t = 2.433; df = 36; p = 0.02). Pearson correlation coefficients and beta coefficients were computed. While tidal volume and pressure support were highly correlated (r = 0.678; p = 0.011), there were no other statistically significant associations. Conclusions The amount of secretions is a common dependent variable in ETS research. During the time that CSSC are attached to the patient and ventilator, moisture from either the ventilator's humidification system or the patient accumulates in the CSSC. This wet weight is not actually part of the secretions retrieved during ETS and should not be considered in the actual weight of secretions. Further study on the determinants of wet weight is warranted.

Over the past several years, the editors of leading international cardiovascular journals have met to form the HEART Group and to discuss areas of growing, common interest. Recently, the HEART Group has developed a document that addresses general ethical principles in the conduct of the scientific process with which all of the editors concur. Published essentially simultaneously in all of the participating journals, including this journal, this document presents the ethical tenets accepted by all of the undersigned editors that will (continue to) guide their decisions in the editorial process. These are the general principles on which the HEART Group is based and by which we, as a group, abide; however, please note that individual journal members and their respective societies may have their own rules and regulations that supersede the guidelines of the HEART Group. Acta Cardiologica Hugo Ector, MD, PhD Editor-in-Chief Patrizio Lancellotti, MD Editor-in-Chief American Journal of Cardiology William C. Roberts, MD Editor-in-Chief American Journal of Geriatric Cardiology Nanette K. Wenger, MD Editor-in-Chief Annals of Noninvasive Electrocardiology Arthur J. Moss, MD Editor-in-Chief Canadian Journal of Cardiology Eldon R. Smith, MD Editor-in-Chief Cardiology Jeffrey S. Borer, MD Editor-in-Chief Cardiosource Review Journal Kim A. Eagle, MD Editor-in-Chief Cardiovascular Drug Reviews Jane Freedman, MD Incoming Editor-in-Chief Henry Krum, PhD Incoming Editor-in-Chief Chim Lang, MD Incoming Editor-in-Chief Cardiovascular Drugs and Therapy Willem J. Remme, MD, PhD Editor-in-Chief Cardiovascular Research Hans Michael Piper, MD, PhD Editor-in-Chief Catheterization and Cardiovascular Interventions Christopher J. White, MD Editor-in-Chief Circulation Joseph Loscalzo, MD, PhD Editor-in-Chief Circulation Research Eduardo Marban, MD, PhD Editor-in-Chief Coronary Artery Disease Burton E. Sobel, MD Editor Current Opinion in Cardiology Robert Roberts, MD Editor Current Problems in Cardiology Shahbudin H. Rahimtoola, MD Editor Europace A. John Camm, MD Editor-in-Chief European Heart Journal Frans Van de Werf, MD Editor-in-Chief European Journal of Heart Failure Karl Swedberg, MD, PhD Editor-in-Chief Heart Adam D. Timmis, MD Editor Heart & Lung: The Journal of Acute and Critical Care Kathleen S. Stone, PhD, RN Editor-in-Chief Heart Rhythm Douglas P. Zipes, MD Editor-in-Chief International Journal of Interventional Cardioangiology David G. Iosseliani, MD Editor-in-Chief Journal of Cardiovascular Computed Tomography Allen J. Taylor, MD Editor-in-Chief Journal of Cardiovascular Pharmacology Michael R. Rosen, MD Editor Journal of Interventional Cardiology Cindy L. Grines, MD Editor-in-Chief Journal of the American College of Cardiology Anthony N. DeMaria, MD Editor-in-Chief JACC: Cardiovascular Imaging Jagat Narula, MD, PhD Editor-in-Chief JACC: Cardiovascular Interventions Spencer B. King III, MD Editor-in-Chief Journal of Electrocardiology Galen S. Wagner, MD Editor-in-Chief Journal of Interventional Cardiac Electrophysiology Sanjeev Saksena, MD Editor-in-Chief Journal of the American Society of Echocardiography Alan S. Pearlman, MD Editor-in-Chief Journal of Heart Valve Disease Endre Bodnar, MD, PhD Editor-in-Chief Robert W. Emery, MD Incoming Editor-in-Chief Journal of Thoracic and Cardiovascular Surgery Lawrence H. Cohn, MD Editor-in-Chief Netherlands Heart Journal Ernst E. van der Wall, MD Editor-in-Chief Pediatric Cardiology Ra-id Abdulla, MD Editor-in-Chief Progress in Cardiovascular Diseases Michael Lesch, MD Editor Revista Espanola de Cadiologia Fernando Alfonso, MD, PhD Editor-in-Chief Scandinavian Cardiovascular Journal Rolf Ekroth, MD Chief Editor

BACKGROUND: Intracranial hypertension occurs in response to routine procedures such as endotracheal suctioning in patients with severe head injuries. In some patients, the intracranial pressure does not immediately return to baseline levels. OBJECTIVES: To examine the effect of drug administration on cerebrovascular response to endotracheal suctioning in adults with severe head injuries. METHODS: Seventy-one subjects were divided into 3 groups: those who received no drugs, those treated with opiates only (morphine sulfate and fentanyl citrate), and those treated with a neuromuscular blocking agent (vecuronium bromide) plus opiates. A controlled protocol involving 2 sequences of endotracheal suctioning that included hyperoxygenation, hyperinflation, and suctioning was used for all subjects. Two-way repeated-measures analyses of variance were done with type of drug as the between-subject factor and phase of suctioning as the within-subject factor. Survival analysis was used to compare the return of intracranial pressure to baseline levels among the 3 groups. RESULTS: Changes in intracranial pressure were significantly smaller in subjects who received a neuromuscular blocking agent plus opiates than in subjects who did not receive any drugs or received opiates only. The greatest increase in intracranial pressure from baseline was in the first and second phases of suctioning. The 3 groups showed no significant difference in the return of intracranial pressure to baseline level. CONCLUSIONS: Neuromuscular blockers attenuate the increases in intracranial pressure that occur with endotracheal suctioning. It is not known whether control of procedurally induced elevations in intracranial pressure affects long-term outcomes in adults with severe head injuries.

The purpose of this study was to examine the effects of three lung hyperinflation/suction sequences on mean arterial pressure (MAP). The results indicate both lung hyperinflation (LHS) and suction sequences (SS) significantly increased MAP ( p = .05) from baseline. There was a mean increase in MAP of 13.72 mm Hg over the three lung hyperinflation/suction sequences. The results showed a significant increase in MAP from baseline between SS 1 to LHS 2 (3.62 mm Hg), from LHS 2 to SS 2 (4.36 mm Hg), and from LHS 3 to SS 3 (2.84 mm Hg) at p = .05. The increase in MAP was cumulative with each successive lung hyperinflation/suction sequence. Consequently, the number of repeated lung hyperinflation/suction episodes should be limited to only those necessary to maintain airway patency.

Mechanical ventilator support and the resumption of spontaneous ventilation or weaning create significant alterations in alveolar and intrathoracic pressure that influence thoracic blood volume and flow. Compensatory autonomic tone alterations occur to ensure adequate tissue oxygen delivery, but autonomic responses may produce cardiovascular dysfunction with subsequent weaning failure. The authors describe autonomic responses of critically ill patients ( n = 43) during a 24-hr period of mechanical ventilatory support and during the 24 hr that included their initial spontaneous breathing trial using continuous positive airway pressure. Nearly two thirds of these patients demonstrated abnormal autonomic function and this dysfunction was more severe in those patients who were unable to sustain spontaneous ventilation ( n = 15). With further systematic study, autonomic responses may be useful in the identification of patients who are likely to develop cardiac dysfunction with the resumption of spontaneous breathing.

A critical review and analysis of the current research on the efficacy of the ventilator versus the manual resuscitation bag (MRB) as the method of delivering hyperoxygenation/hyperinflation breaths before, during, and/or after endotracheal suctioning (ETS) is presented. Current research findings indicate that hyperoxygenation/hyperinflation breaths at 100% oxygen (O2) delivered via the ventilator have resulted in elevated blood-O2 levels which are either superior or equivalent to the MRB in preventing suction-induced hypoxemia. Delivery of hyperoxygenation/hyperinflation breaths using the MRB results in increased airway pressure, and increased hemodynamic consequences. Guidelines of clinical practice, based on current research findings, are presented. Areas for further research are identified

Undergraduate and graduate nursing students were partnered in a short-term transcultural nursing experience in Choluteca Honduras. Learning objectives specific to the level of the student were developed to meet their individual needs with a women's health focus. Learning opportunities were created to encourage interaction between the undergraduate and graduate students. The students partnered to deliver women's health care in a primary health care clinic, through a women's health seminar, a community health fair, in a hospital-based labor management clinical experience and in a rural health clinic.

Study objective To determine the extent to which a mixture of human gastric juice and enteral formula stained with two concentrations of FD&C Blue No. 1 food dye (0.8 and 1.5 mL/L) is visible in suctioned tracheobronchial secretions following three forced small-volume pulmonary aspirations over a 6-h period in an animal model. Design Experimental 2 × 3 repeated measures. Setting Animal laboratory and an acute care hospital. Participants Ninety New Zealand white rabbits weighing approximately 3 kg each, and 90 acutely ill adults who furnished gastric juice. Interventions A mixture of human gastric juice and enteral formula stained with 0.8 or 1.5 mL of dye per liter was instilled intratracheally over a 30-min period into anesthetized intubated animals at baseline, 2 h, and 4 h. A total of 0.4 mL/kg of the mixture was instilled at each session. Ninety minutes after each instillation, suctioned secretions were examined for visible dye and blood. Measurements and results Dye was visible in 46.3% of the secretions (125 of 270). The concentration of dye had no significant effect on dye visibility. Blood that was present in 114 of 270 of the secretions (42.2%) interfered with dye visibility in all but two secretions. For reasons unknown, even in the absence of blood, dye visibility decreased from 90.2% (55 of 61 secretions) after the first aspiration event to only 61% (25 of 41 secretions) after the third aspiration event. Conclusions Findings from this animal model study do not support the use of the dye method to detect repeated small-volume aspirations. For clinicians who choose to use the dye method in selected situations, it appears that a dye concentration of 0.8 mL/L may be as effective in detecting aspiration as a 1.5 mL/L concentration.

Variations in intrathoracic pressure generated by different ventilator weaning modes may significantly affect intrathoracic hemodynamics and cardiovascular stability. Although several investigators have attributed cardiovascular alterations during ventilator weaning to augmented sympathetic tone, there is limited investigation of changes in autonomic tone during ventilator weaning. Heart rate variability (HRV), the analysis of beat-to-beat changes in heart rate, is a noninvasive indicator of autonomic tone that might be useful in the identification of patients who are at risk for weaning difficulty due to underlying cardiac dysfunction. The authors describe HRV and hemodynamics in response to 3 ventilatory conditions: pressure support (PS) 10 cmH2O, continuous positive airway pressure (CPAP) 10 cmH2O, and a combination of PS 10 cmH2O and CPAP 10 cmH2O (PS+CPAP) in a group of canines with normal ventricular function. Six canines were studied in the laboratory. Continuous 3-lead electrocardiographic data were collected during baseline (controlled mechanical ventilation) and following transition to each of the ventilatory conditions (PS, CPAP, PS+CPAP) for analysis of HRV. HRV was evaluated using power spectral analysis to define the power under the curve in a very low frequency range (0.0033 to < 0.04 Hz, sympathetic tone), a low frequency range (0.04 to < 0.15 Hz, primarily sympathetic tone), and a high frequency range (0.15 to < 0.40 Hz, parasympathetic tone). A thermodilution pulmonary artery catheter measured cardiac output and right ventricular end-diastolic volume to describe global hemodynamics. There were significant increases in very low frequency power (sympathetic tone) with a concomitant significant reduction in high-frequency power (parasympathetic tone) with exposure to PS+CPAP. These alterations in HRV were associated with significantly increased heart rate and reduced right ventricular end-diastolic volume. Although there was a small but significant increase in cardiac output with exposure to PS, HRV was unchanged. These data indicate that there was a relative shift in autonomic balance to increased sympathetic and decreased parasympathetic tone with exposure to PS+CPAP. The increase in intrathoracic pressure reduced right ventricular end-diastolic volume (preload). This hemodynamic alteration generated a change in autonomic tone, so that cardiac output could be maintained. Individuals with autonomic and/or cardiovascular dysfunction may not be capable of this type of response and may fail to successfully wean from mechanical ventilation.

The immediate transition from positive pressure mechanical ventilation to spontaneous ventilation may generate significant cardiopulmonary hemodynamic alterations based on the mode of weaning selected, particularly in individuals with preexisting cardiac dysfunction. The purpose of this study was to compare hemodynamic responses associated with the initial transition to 3 modes of ventilator weaning (spontaneous ventilation/T-piece, pressure support [PS], and continuous positive airway pressure [CPAP]). Right ventricular hemodynamic responses were evaluated with a thermodilution pulmonary artery catheter; while left ventricular hemodynamic responses were measured by a transducer-tipped Millar catheter and conductance catheter. Two groups of canines were studied. Group 1: normal biventricular function (n = 10) and group 2: propranolol-induced biventricular failure (n = 10). Dependent variables were measured at baseline on controlled mechanical ventilation (MV) and following the initial transition to each of 3 randomized spontaneous ventilatory conditions: T-piece, PS 5 cmH2O, and CPAP 5 cmH2O. Both groups significantly increased cardiac output in response to T-piece. Right ventricular stroke work was also significantly increased with T-piece and CPAP in both groups of subjects. Left ventricular response depended on baseline ventricular function. Baseline ventricular function influenced hemodynamic response to the immediate transition from mechanical to spontaneous ventilation. There were also differential hemodynamic responses based on the ventilatory mode. Consideration of baseline cardiac function may be an important factor in the selection of an appropriate mode of spontaneous ventilation following controlled MV.

Hemodynamic instability during weaning from mechanical ventilation is one proposed cause of weaning failure. This study evaluated cardiac power output (CPO) as an indicator of significant hemodynamic alteration and cardiac reserve during the transition from controlled mechanical ventilation to spontaneous ventilation using three clinical weaning modes. It also compared CPO with commonly used indicators of hemodynamic instability during weaning. The data suggest that CPO is a sensitive indicator of significant hemodynamic alteration and could be used to optimize cardiovascular function during weaning from mechanical ventilation to increase the likelihood of weaning success. Key words: cardiac output, cardiac power output, hemodynamic monitoring, mechanical ventilation

A repeated measures randomized within-group design was used to determine the effectiveness of controlled short-duration hyperventilation (HV) in blunting the increase of intracranial pressure (ICP) during endotracheal suctioning (ETS). A multimodal continuous real-time computerized data acquisition procedure was used to compare the effects of two HV ETS protocols on ICP, arterial pressure, cerebral perfusion pressure (CPP), heart rate, and arterial oxygen saturation in severe head-injured adult patients. The results indicated that short-duration HV for 1 minute, which decreases the PaCO2, reduced ETS-induced elevations in ICP while maintaining CPP. However, it is not clear whether short-duration HV is neuroprotective, particularly in ischemic regions of the brain. Therefore, before a change in practice is implemented on the use of short-duration HV as a prophylactic treatment against ETS-induced elevations in ICP, additional questions on cerebral oxygen delivery and uptake need to be answered.

Endotracheal suctioning (ETS) is a common procedure done in the critical care environment. There are many different practices related to ETS. With the proliferation of research studies about ETS, a change in practice is needed to incorporate these research findings. The authors present a creative teaching strategy that was used to implement a research-based ETS protocol

Endotracheal suctioning (ETS) is a conventional nursing intervention used to decrease pulmonary complications in the critically ill patient. ETS provides a particular dilemma for the head-injured patient because it increases intracranial pressure and may put the patient at increased risk for intracranial hypertension and cerebral ischemia. Research in endotracheal suctioning targets understanding the ETS response in the severely head-injured patient. This article reviews the major research focused on suctioning the head-injured patient. The guidelines for practice based on this research include preoxygenating patients prior to suctioning, limiting suction duration to 10 seconds, limiting suction passes to 1-2 per procedure, using hyperventilation with caution, not rotating the head, keeping negative suction pressure under 120 mm Hg, and not using suction catheters with outer to inner diameter ratios greater than .50.

The purpose of this study was to examine the effect of sequential lung hyperinflation breaths followed by suction on mean arterial pressure (MAP), cardiac output (CO), pulmonary artery pressure (PAP), and pulmonary airway pressure (Paw) to elucidate the mechanism for the increase in MAP seen with lung hyperinflation and suction. Thirty-four postoperative coronary artery bypass graft patients were randomly exposed to three lung hyperinflation breaths at one of five volumes (tidal volume, 12cc/kg, 14cc/kg, 16cc/kg, and 18cc/kg of lean body weight) using a ventilator followed by 10 s of suctioning repeated for a total of three times. There was a mean increase in MAP (13.71 torr), CO (12.2%), PAP (4 torr), and Paw (23.5 torr) above baseline over the three sequences. The mechanism for the increase in MAP with lung hyperinflation may be attributed to transient increases in intrathoracic pressure, resulting in increased left ventricular preload and CO.

The purpose of this study was to determine the minimum amount of discard sample required to remove all heparinized normal saline from an indwelling arterial catheter to obtain an accurate arterial blood gas (ABG) sample. The pH and partial pressure of oxygen (PO2) and carbon dioxide (PCO2) were adjusted to known values prior to the onset of the study. The discard sample size ranged from zero to 5 cubic centimeters (cc), increasing at 0.5-cc increments. Twenty-nine sets of 11 consecutive discard/ABG samples, totaling 319 ABG specimens, were drawn over 20 minutes. Based on the data, a 2-cc discard is sufficient to guarantee accurate blood gases when withdrawing blood from an arterial catheter with a 1-cc dead space volume.