Liver function in patients with mild alcoholic hepatitis, after enflurane, nitrous oxide-narcotic, and spinal anesthesia.

The effects of three anesthetic techniques on liver function were compared in patients with mild alcoholic hepatitis who required surgery, both peripheral and superficial. Thirty patients were randomly assigned to receive one of three anesthetics: thiopental, nitrous oxide and oxygen, enflurane, plus muscle relaxant; thiopental, nitrous oxide and oxygen, narcotic, plus muscle relaxant; or spinal anesthesia with tetracaine. Measurements of hepatic function were made preoperatively (on the day of operation) and on the first and third postoperative days. Levels of serum bilirubin, serum glutamic oxaloacetic transaminase, serum glutamic pyruvic transaminase, and lactate dehydrogenase liver isoenzyme were similar in the three groups on both postoperative days. They were not significantly different from those obtained preoperatively, although mean values decreased by the first postoperative day and again on the third. The data suggest that the choice among the three anesthetic methods studied could be based on factors other than the presence of mild alcoholic hepatitis and that, when peripheral surgery is required, one may not anticipate a worsening of any biochemical disorder in the first three postoperative days.

Pulmonary, chest wall, and lung-thorax elastances in acute respiratory failure.

The usefulness of lung-thorax compliance (or elastance) as an index of pulmonary compliance (or elastance) was examined in 15 patients being ventilated for acute respiratory failure. Mean lung-thorax elastance (ELT) was 27.9 +/- 2.6 cm H2O/L, and the chest wall accounted for 34 +/- 2 percent of the mean total value. Changes in ELT caused by increments of positive end-expiratory pressure correlated only with changes in pulmonary elastance (r = 0.96; P less than 0.001) and not with chest wall elastance, although individual patients varied as to the contribution of the chest wall component. Lung-thorax elastance increased in direct proportion (1:1) to increases in pulmonary elastance, whereas the changes in lung-thorax compliance were only half those in pulmonary compliance. We conclude that elastance is a more useful clinical index than compliance.

Measurement of functional residual capacity during mechanical ventilation by simultaneous exchange of two insoluble gases.

A precise method for rapid measurement of functional residual capacity (FRC) during mechanical ventilation that uses the simultaneous exchange of argon and nitrogen is described. Circuit leaks were immediately recognizable upon completion of a run, and pneumotachygraphic inaccuracies due to turbulent flows, changes in viscosity, and time delays between pneumotachygraph and mass spectrometer signals were avoided. For 166 duplicate determinations, the first measurement of FRC differed from the second by 0.5 +/- 0.5 per cent (mean +/- SE). The technique does not affect pulmonary gas exchange. During 35 consecutive determinations of FRC (with an inspired oxygen of 50 per cent), mixed expired oxygen and carbon dioxide tensions varied less than 7 and 1.5 torr, respectively.

Time course and mechanisms of lung-volume increase with PEEP in acute pulmonary failure.

To determine the effects of a step change in end-expiratory pressure on functional residual capacity (FRC) and lung-thorax compliance (CLT), 10 cm H2O positive end-expiratory pressure (PEEP) was applied in eight patients who needed mechanical ventilation for acute pulmonary failure. Of the total change in FRC, 66 +/- 5.3 per cent (mean +/- SEM) was complete within the next breath, and 90 per cent change was achieved in 4.6 +/- 1.4 breaths (24 +/- 6.4 sec). There was no statistically significant difference between times to 90 per cent FRC change with application and with removal of PEEP. In another 13 patients, PEEP was increased in 5 cm H2O steps from 3 to 18 cm H2O. Mean FRC at 3 cm H2O PEEP was 1.51 +/- 0.20 1 (55 +/- 7.0 per cent predicted supine value). Mean CLT did not change significantly until 18 cm H2O PEEP was reached, at which point it decreased (P < 0.005). The static compliance derived from change in FRC (deltaFRC/deltaPEEP) increased with increments of PEEP (P < 0.05) compared with the initial level. At PEEP levels of 8 and 13 cm H2O, mean FRC was larger than would be predicted from mean CLT (P < 0.005), but it was not significantly different at 3 cm H2O PEEP. The lung component accounted for 62 +/- 3.7 per cent of the lung-thorax compliance difference. These data define a time-dependent increase in lung volume that resembles pressure-volume hysteresis in normal man. Possible mechanisms include surface tension changes, recruitment of nonventilated lung, and stress relaxation of lung and chest wall. This study may explain the greater efficiency of PEEP compared with large tidal-volume ventilation in increasing PaO2 in patients with acute pulmonary failure.