Oxygen Consumption and Lactate Release by the Lung After Cardiopulmonary Bypass and During Septic Shock
ABSTRACT
Objective:
We sought to determine whether a correlation exists between lung lactate release and lung oxygen consumption by studying adult intensive care patients, either after cardiopulmonary bypass (CPB) or with septic shock.
Methods:
A prospective observational study of six post cardiopulmonary bypass patients and seven patients with septic shock was performed in an intensive care unit of a major teaching hospital. Pulmonary oxygen consumption was estimated by subtracting oxygen consumption calculated using the reverse Fick equation ( O2Fick) from that measured by indirect calorimetry ( O2meas). Pulmonary lactate release was derived from the difference between arterial and mixed-venous lactate, multiplied by cardiac output.
Results:
Pulmonary oxygen consumption comprised a substantial component of total oxygen consumption (CPB-median: 20.6%; interquartile range (IQR): 15.4 - 27.3%; septic shock-median: 32.3%; IQR: -4.0 - 35.4%). Lung lactate release occurred both after CPB (median: 27.5mmol/hr; IQR: 24.8-64.1 mmol/hr) and with septic shock (median: 55.4 mmol/hr; IQR: 24.3 - 217.6 mmol/hr). Although no correlation was found between lung lactate release and pulmonary oxygen consumption, lactate release correlated with O2meas and O2Fick in septic patients (p < 0.005).
Conclusions:
We conclude that lung oxygen consumption and lactate release are substantial in conditions associated with lung inflammation. Lactate release and lung oxygen consumption may not share a common pathogenesis, however there is an association between lung lactate release and systemic oxygen consumption in sepsis. (Critical Care and Resuscitation 1999; 2: 181-187)
Key words:
Critical illness, lactate, lung, oxygen consumption, sepsis
