Effect of ventilation on cerebral oxygenation in patients undergoing surgery in the beach chair position: a randomized controlled trial.

BACKGROUND: Surgery in the beach chair position (BCP) may reduce cerebral blood flow and oxygenation, resulting in neurological injuries. The authors tested the hypothesis that a ventilation strategy designed to achieve end-tidal carbon dioxide (E'(CO2)) values of 40-42 mm Hg would increase cerebral oxygenation (Sct(O2)) during BCP shoulder surgery compared with a ventilation strategy designed to achieve E'(CO2) values of 30-32 mm Hg. METHODS: Seventy patients undergoing shoulder surgery in the BCP with general anaesthesia were enrolled in this randomized controlled trial. Mechanical ventilation was adjusted to maintain an E'(CO2) of 30-32 mm Hg in the control group and an E'(CO2) of 40-42 mm Hg in the study group. Cerebral oxygenation was monitored continuously in the operating theatre using near-infrared spectroscopy. Baseline haemodynamics and Sct(O2) were obtained before induction of anaesthesia, and these values were then measured and recorded continuously from induction of anaesthesia until tracheal extubation. The number of cerebral desaturation events (CDEs) (defined as a ≥20% reduction in Sct(O2) from baseline values) was recorded. RESULTS: No significant differences between the groups were observed in haemodynamic variables or phenylephrine interventions during the surgical procedure. Sct(O2) values were significantly higher in the study 40-42 group throughout the intraoperative period (P<0.01). In addition, the incidence of CDEs was lower in the study 40-42 group (8.8%) compared with the control 30-32 group (55.6%, P<0.0001). CONCLUSIONS: Cerebral oxygenation is significantly improved during BCP surgery when ventilation is adjusted to maintain E'(CO2) at 40-42 mm Hg compared with 30-32 mm Hg. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov NCT01546636.

Influence of a vital capacity maneuver on pulmonary gas exchange after cardiopulmonary bypass.

OBJECTIVE: To investigate the effect of a single, vital capacity breath (vital capacity maneuver [VCM]), administered at the end of cardiopulmonary bypass (CPB), on pulmonary gas exchange in patients undergoing coronary artery bypass graft surgery. DESIGN: Prospective, randomized, double-blind study. SETTING: University-affiliated hospital. PARTICIPANTS: Forty patients scheduled for elective coronary artery bypass graft surgery and early tracheal extubation. INTERVENTIONS: Patients were randomized to 1 of 2 groups. VCM patients received a VCM at the conclusion of CPB. Control patients received no VCM. MEASUREMENTS AND MAIN RESULTS: Intrapulmonary shunt (Q(S)/Q(T)), arterial oxygenation (PaO2), and alveolar-arterial oxygen gradients (P(A-a)O2) were measured after induction of anesthesia, CPB, intensive care unit (ICU) arrival, and extubation. The duration of postoperative intubation was recorded for each group. Q(S)/Q(T) increased significantly 30 minutes after CPB in the control group (15.7 +/- 1.8% to 27.4 +/- 2.6%; p = 0.01). In the VCM group, a small decrease in Q(S)/Q(T) occurred (16.1 +/- 2.0% to 14.9 +/- 2.0%). After ICU arrival and extubation, no significant difference in Q(S)/Q(T) existed between the 2 groups. With the exception of a higher P(A-a)O2 in the control group at induction of anesthesia, no differences in PaO2 or P(A-a)O2 were present between the 2 groups at any measurement interval. Patients who received a VCM were extubated earlier than the control group (6.5 +/- 2.1 hours v 9.4 +/- 4.2 hours; p = 0.01). CONCLUSION: The use of a VCM prevented an increase in Q(S)/Q(T) from occurring in the operating room. Although a VCM did not influence pulmonary gas exchange in the ICU, its application in the operating room appears to exert a beneficial effect on tracheal extubation times after cardiac surgery.

Commentary. Balancing sedation and analgesia in the critically ill.

The authors have presented a template for a systematic approach to comforting critically ill patients that can be modified to suit institutional preferences. In this algorithm, the cause of patient discomfort is sought with the priority given to pain and then to anxiety. Special attention is directed to the identification of correctable causes of pain and anxiety with application of nonpharmacologic techniques or medications to control patient discomfort. This step is followed by subsequent reassessment of the need for sedation or anxiolysis and titration or discontinuation of therapy as able. The benefits of protocol-driven care are becoming increasingly evident, and the authors believe the algorithm outlined here provides a rational and practical approach to patient management. It also prompts the caregiver to reevaluate patients' needs and to keep to patients at target sedation levels. Doing so can promote cost effectiveness, reduce side effects caused by drugs, and decrease morbidity and ICU stay. Any treatment protocol or algorithm is simply a guide to therapy and cannot address every clinical situation. The importance of individualized care and physician or care team judgment must be emphasized.

Anxiety, delirium, and pain in the intensive care unit.

Anxiety, agitation, delirium, and pain are common findings in the ICU. These unhealthy states may lead to increased irritability, discomfort, hypertension, tachycardia, cardiac ischemia, harmful motor activity, and psychologic disquiet for the patient. The appropriate treatment of these conditions may lead to decreased morbidity and mortality in the critically ill patient. Unfortunately, the management of anxiety, agitation, delirium, and pain in the intensive care unit is not ideal. Many patients interviewed after an ICU stay rate their pain control as poor and their memories of their stay as unpleasant. Furthermore, many caregivers lack sufficient understanding of the appropriate or indicated uses of drugs to allay patients' fears and pain. The use of suitable protocols for the proper titration of sedation of mechanically ventilated patients and monitoring of the level of sedation in ventilated patients may decrease the amount of time that patients are ventilated and may alleviate some of the emotional stresses of recall of painful procedures or uncomfortable mechanical ventilation. Future research into protocols for the care of the critically ill patient can enhance the overall well-being of these patients.

Neuromuscular-blocking drugs. Use and misuse in the intensive care unit.

The use of NMB agents for more than 24 to 48 hours in critically ill patients is associated with many potential complications. Neuromuscular-blocking drugs should be used only when their use is essential for optimal patient care. The indications for neuromuscular blockade must be defined clearly, and patients should be evaluated during treatment for the need for continued muscle relaxation. The smallest doses of NMB agents that will accomplish clinical goals should be used. This dosage can be determined through clinical evaluations and peripheral nerve monitoring. It is essential that all patients treated with NMB drugs receive appropriate sedation and analgesia. Myopathies, neuropathies, and alterations of the neuromuscular junction can occur in the ICU setting, and nondepolarizing muscle relaxants seem to be involved in the development of these disorders. Clinicians should be aware of risk factors that may predispose certain patients to neuromuscular complications, including sepsis and the use of high-dose steroids. Neuromuscular-blocking agents should be avoided in these patients if possible. Although not proved, early recognition and treatment of iatrogenic neuromuscular complications may improve patient outcome.

A multicenter evaluation of a new continuous cardiac output pulmonary artery catheter system.

OBJECTIVE: To validate a new system of continuous cardiac output monitoring. DESIGN: Multicenter, prospective, nonrandomized clinical study. SETTING: Four university hospitals. PATIENTS: Forty-seven adult intensive care unit patients. INTERVENTIONS: Pulmonary artery catheterization. MEASUREMENTS AND MAIN RESULTS: Continuous and bolus cardiac output measurements were obtained over 72 hrs. The 327 continuous cardiac output measurements compared favorably with bolus cardiac output measurements (bias = 0.12 L/min, precision = +/-0.84). The continuous cardiac measurement was not adversely affected by temperatures of <37 degrees C or >38 degrees C, high (>7.5 L/min) or low (<4.5 L/min) cardiac output values, or duration (72 hrs) of the study. CONCLUSIONS: This continuous cardiac output system provides a reliable estimate of cardiac output for clinical use if applied in conditions similar to this study. The combination of a continuous measure of cardiac output with other continuous physiologic monitoring (arterial and mixed venous oxygen saturation, oxygen consumption, etc.) may provide important information that no single parameter could achieve.

Resolved: A pulmonary artery catheter should be used in the management of the critically ill patient. Pro.

Selected studies showing both positive and negative outcomes with the use of pulmonary artery catheters (PACs) are reviewed. Indications for use of a PAC are controversial, although clearly the "red cap syndrome" is an indication for its insertion. There are sufficient data as well as personal experience to suggest that PACs do make a difference in the management of critically ill patients. Attention is focused on the level of physician expertise in interpreting data provided by PAC monitoring as the most critical limitation on the physician's ability to make appropriate clinical decisions. Studies are reviewed that addressed physician level of expertise related to PAC insertion, complications, data and waveform interpretation, and management. User knowledge clearly is suboptimal. Before attempting to draw conclusions from outcome studies, criteria for appropriate use need to be developed and clinician knowledge needs to be significantly improved.

Training requirements for pulmonary artery catheter utilization in adult patients.

OBJECTIVE: To review the literature addressing the issue of training requirements for pulmonary artery catheter (PAC) utilization in adult patients. DATA SOURCE: All pertinent English language articles dealing with training requirements for pulmonary artery catheterization were retrieved from 1984 through 1997. STUDY SELECTION: Articles were chosen if issues related to training and pulmonary artery catheterization were studied or reviewed. DATA EXTRACTION: From the articles selected, information about PAC training was obtained. DATA SYNTHESIS: The PAC is a commonly employed monitoring tool in the management of critically ill patients. Recent publications have strongly implied that PAC monitoring is associated with an increased morbidity and no notable clinical benefit. In response to these findings, the value of PAC monitoring has been questioned. The benefit assessment of any technology on clinical outcome presumes that the care provider possesses the skills and knowledge to optimally utilize the data obtained and simultaneously minimize the potential complications. Several recent articles have addressed physician and nurse knowledge as it pertains to PAC monitoring. The results of these studies are quite alarming. Marked deficiencies of knowledge were noted particularly in area of data interpretation and patient management. Extrapolating from their conclusions, it appears that any effort to proactively assess the value of PAC monitoring will be compromised until attempts are made to standardize and optimize the clinical skills of those involved in utilization of the technology. This article provides a proposed program for clinical education and raises the question regarding the necessity of demonstrated proficiency. CONCLUSION: Training, credentialing, and continued quality improvement related to PAC should be improved.

Point-of-care testing.

Point-of-care testing refers to testing outside of the central laboratory at or near the patient's bedside. The practice greatly decreases turnaround time for testing and has improved outcome and decreased length of stay in some patient groups. Advances in technology have made analyzers increasingly portable with expanded testing capacities while maintaining standards for accuracy required by regulatory agencies. It is possible for clinicians to perform testing that historically was performed only in the central laboratory by trained laboratory technicians. Determination of all appropriate bedside testing for different clinical areas and patient groups will require further investigation and debate.

Clinical evaluation of continuous noninvasive blood pressure monitoring: accuracy and tracking capabilities.

A continuous, noninvasive device for blood pressure measurement using pulse transit time has been recently introduced. We compared blood pressure measurement determined using this device with simultaneous invasive blood pressure measurements in 35 patients undergoing general endotracheal anesthesia. Data were analyzed for accuracy and tracking ability of the noninvasive technique, and for frequency of unavailable pressure measurements by each method. A total of 25,133 measurements of systolic pressure, diastolic pressure, and mean arterial pressure (MAP) by each method were collected for comparison from 35 patients. Accuracy was expressed by reporting mean bias (invasive pressure minus noninvasive pressure) and limits of agreement between the two measurements. After correction for the offset found when measuring invasive and oscillometric methods of arterial pressure measurement, the mean biases for systolic, diastolic, and mean pressures by the pulse wave method were -0.37 mm Hg, -0.01 mm Hg, and -0.05 mm Hg, respectively (p < 0.001). The limits of agreement were: -29.0 to 28.2 mm Hg, -14.9 to 14.8 mm Hg, and -19.1 to 19.0 mm Hg, respectively (95% confidence intervals). When blood pressure measured invasively changed over time by more than 10 mm Hg, the noninvasive technique accurately tracked the direction of change 67% of the time. During the entire study, 3.2% of the invasive measurements were unavailable and 12.9% of the noninvasive measurements were unavailable. The continuous noninvasive monitoring technique is not of sufficient accuracy to replace direct invasive measurement of arterial blood pressure, owing to relatively wide limits of agreement between the two methods.(ABSTRACT TRUNCATED AT 250 WORDS)

Arterial blood gas monitoring.

Arterial blood gas determinations (ABGs) play an important role in diagnosing derangements in acid-base balance, oxygenation, and ventilation. Frequent assessment is necessary in the management of critically ill patients. This article reviews the technologic evolution of modern blood gas analysis and the clinical application of monitoring hydrogen ion content (pH), blood oxygen tension (PO2), and carbon dioxide tension (PCO2).

Oxygen therapy.

Understanding the various delivery systems of the most commonly used therapies in the critical care setting will help avoid iatrogenic problems and enhance ability to deliver effective goal-oriented critical care. Rational use of oxygen is a result of understanding the goals, complications, and risks of oxygen therapy.

Sedation, analgesia, and neuromuscular blockade in critical care: an overview.

The practice of critical care medicine has progressed dramatically over the past several decades. With the advent of new pharmacological therapies and technological interventions, our ability to manage a multitude of pathophysiologic conditions has grown. As a consequence of these advances, we have recognized the potential to reduce the morbidity and mortality associated with many disease states that were previously irreversible. Associated with new therapeutic and diagnostic interventions are secondary side effects and complications. It is often the undesired sequela of all interventions that forces clinicians to periodically reevaluate to whom, why, how, and when we employ new drugs or procedures.

Clinical utilization of pulmonary artery catheter monitoring.

Since the introduction of PA catheter monitoring in 1970, the applications for it have dramatically broadened. PA catheters are used to obtain hemodynamic data for the assessment, monitoring, and therapeutic management of critically ill, high-risk surgical patients. Because of potential complications associated with PA catheter monitoring, numerous editorials and articles have questioned the procedure's risk-to-benefit ratio. These articles address the inadequacy of outcome data and suggest no demonstrated benefit from PA monitoring. Subgroups of patients have been identified, however, in whom PA monitoring data altered clinicians' assessment and management. In spite of a study by Rao and colleagues implying that PA catheter monitoring can decrease the mortality rate in critically ill patients, no scientific study has confirmed this impression. A more recent article evaluated the impact of PA catheter monitoring on mortality with emphasis on how the information is used. This prospective study noted a potential benefit from PA catheter monitoring in a protocol group, but the limited sample size and selection criteria prevent definitive conclusions. Unfortunately, many of the reported studies are retrospective, nonrandomized, unblinded, limited in scope or size, and founded on subjective end points. Careful evaluation of individual studies is mandatory to avoid overinterpretation of the conclusions. Understanding the limits of PA monitoring is needed for therapy to be successful. Problems may stem not from technology but from the knowledge and expectations of clinicians. "Human" complications from inadequate understanding of the physiological data is not uncommon. Measured pressures by themselves can be misleading; indeed use of absolute numbers rather than trends or relative changes in the values monitored can compromise clinical assessment. Overzealous acceptance and utilization of any quantitative measurement without sound clinical judgment is fraught with failure.

Invasive cardiac monitoring.

Since its introduction in 1970, the application for PA catheter monitoring has dramatically broadened. PA catheters provide the ability to obtain hemodynamic data for the assessment, monitoring, and therapeutic management of critically ill patients. Because of the potential complications associated with PA catheter monitoring, numerous editorials and articles have questioned the procedure's risk to benefit ratio. These articles address the insufficient availability of adequate outcome data or suggest no demonstrated benefit from PA monitoring. Subgroups of patients have been identified in whom the data obtained from PA monitoring altered the clinician's assessment and management. In spite of the study of Rao, which implies that PA catheters can improve mortality in critically ill patients, no scientific study of outcome has been able to confirm this impression. If an adequate understanding of the limitations of PA monitoring does not exist, appropriate selection and implementation of therapy cannot occur. The problem is not as much the technology, as it is the knowledge and expectations of the clinician. "Human" complications from inadequate understanding of the physiologic data are quite common. Reliance on the measured pressure is often misleading. The use of "absolute numbers" rather than trends or relative changes in the values monitored can compromise clinical assessment. Overzealous utilization and acceptance of any quantitative measurement without coordination with clinical judgment is fraught with failure.

Noninvasive oxygen monitoring.

Assessment of oxygenation is an integral part of monitoring critically ill patients. Current available modalities including pulse oximetry, transcutaneous and transconjunctival oxygen measurements are reviewed. In addition, future modalities to assess oxygen delivery and utilization at the level of the intact end-organ are discussed.