Monitoring of acid-base and regulating variables during abdominal lavage.

This prospective clinical study was performed to determine acid-base regulating variables during abdominal lavage treatment for patients with severe peritonitis or after abdominal surgery. Arterial blood was sampled from twelve patients with secondary peritonitis and nine patients after abdominal surgery without peritonitis at three time points: immediately before, immediately after and 15 minutes after abdominal lavage with normal saline solution. The total amount of irrigant fluid, the strong ion difference [(Na+ + K+)-(Cl- + lactate-)], and total protein concentrations were determined and standard bicarbonate, standard base excess were calculated from pH and PaCO2. Peritonitis patients developed a moderate alkalaemia (pH 7.440-7.485). The alkalaemia was unmasked after optimization of mild hypoventilation, but was supported by a decrease in protein concentration of about 3.4 mEql/l in the first 15 minutes after the lavage. There was no marked increase in chloride concentration in either the peritonitis or the control group. The data indirectly exclude major fluid absorption during abdominal lavage with 3000 to 6000 ml normal saline, given that we found no clinically relevant electrolyte and acid-base changes that might be expected after rapid fluid absorption. The factors of major influence in acid-base regulation were ventilation and protein loss in the course of abdominal lavage. Monitoring of the Stewart variables is an easily applicable method of monitoring acid-base regulating variables in the perioperative course of patients undergoing abdominal lavage therapy.