Keith R. Walley

Comparison of transesophageal echocardiographic, fick, and thermodilution cardiac output in critically ill patients

PURPOSEnRecent observations have highlighted errors in the thermodilution technique of measuring cardiac output. Thus, cardiac output measurements using transesophageal echocardiography and the Fick method were compared with simultaneous thermodilution measurements.nnnMETHODSnIn 13 mechanically ventilated critically ill patients, cardiac output was determined simultaneously using (1) transesophageal echocardiography (COTEE, (2) the Fick method (COFICK, and (3) thermodilution (COTD immediately before and after a rapid infusion of 500 mL of saline. Left ventricular end-diastolic and end-systolic areas were measured using the transesophageal echocardiographic transgastric short axis view, and COTEE was calculated from the corresponding volumes. Absolute cardiac output values and the changes from before to after saline infusion (delta CO) were compared using analysis of variance, linear regression, and the Bland and Altman method.nnnRESULTSnThere were no significant differences between COTEE (8.0 +/- 3.4), COFICK (8.4 +/- 3.3), and COTD (8.3 +/- 3.0) or between delta COTEE, delta COFICK, and delta COTD using analysis of variance. However, correlations between COTEE and COTD (r2 = 0.46; P < .00001), COFICK and COTD (r2 = 0.46; P < .0001), and COTEE and COFICK (r2 = 0.42; P < .0001) were only moderately good. Using the method of Bland and Altman, the mean difference (+/-2 standard deviations) between COTEE and COTD was 0.3 +/- 4.3 L/min, between COFICK and COTD was -1.0 +/- 3.8 L/min, and between COTEE and COFICK was 0.6 +/- 5.6 L/min, whereas the difference between delta COTEE and delta COTD was 0% +/- 26%, between delta COFICK and delta COTD was 9% +/- 46%, and between delta COTEE and delta COFICK was 8% +/- 39%.nnnCONCLUSIONSnThere are substantial differences in cardiac output as measured by these three methods, best demonstrated using the method of Bland and Altman. The variability of cardiac output and its derivatives (eg, oxygen delivery) should be borne in mind when making clinical decisions on individual patients.

Impact of acid-base disorders on individual organ systems

More than other electrolyte disorders, abnormal hydrogen ion concentrations, particularly when excessive, are associated with organ dysfunction and damage [1, 2]. Therefore, physicians often intervene aggressively to compensate for inadequate ventilation and lower PaCO2 through institution of ventilatory support, and to correct acidosis by administration of alkali. However, over the past decade, it has become increasingly clear that acute acid-based disturbances have somewhat lesser effects on cardiovascular [3, 4] and other organ system function than previously thought. Further, aggressive correction of abnormal values of pH and PaCO2 without adequate regard to the pathophysiologic processes which underlie them is often ineffective and associated with significant deleterious effects [5–11]. Management of the critically ill patient with arterial blood gas abnormalities therefore should be based on correction of the underlying process of the acid-base disturbance, while minimizing therapies such as alkali administration (6) and excessive mechanical ventilation, which are intended merely to alter abnormal laboratory values without addressing their cause.

Acute respiratory distress syndrome : a comprehensive clinical approach

1. Overview and radiology of ARDS Dr Vinay Dhingra and Dr James Russell 2. Clinical causes and epidemiology Dr Bryan Garber and Dr Paul Hebert 3. Pathology Dr Joanne L. Wright 4. Molecular mechanisms Drs Steven Kunkel, T. J. Standiford, Cary Caldwell, Nicholas Lukacs, and Robert Strieter 5. Pulmonary physiology and monitoring Dr Keith Walley 6. Cardiovascular physiology and management Drs K. Walley, J. Russell 7. Mechanical ventilation Dr G. Schmidt 8. Weaning Dr Tobin and Dr Dhand 9. Clinical assessment and total patient care Dr J. Russell, Dr K. Walley and Dr V. Dhingra 10. Innovative therapy Dr Gordon Bernard 11. Pneumonia Dr R. B. Light and Dr Bahammam 12. Resolution and repair Dr M. Matthay, Dr R. Bowler and Dr Garat 13. Multiple system organ failure Dr James Russell and Dr Ari Uusaro 14. Outcome Dr R. Albert.