sodium-bicarbonate and Pneumonia--Aspiration

Gastric pH and volumes were measured in 84 women who had general anaesthesia for emergency Caesarean section. Forty-eight received only 20 ml 8.4% sodium bicarbonate immediately before induction of anaesthesia and 36 ranitidine 150 mg 6-hourly during labour in combination with NaHCO3. Gastric pH was less than 2.5 in four women who received only bicarbonate. All aspirates from the ranitidine plus bicarbonate group had a pH greater than 2.5. Mean volumes of gastric content aspirated were 87 (SD 87.4) and 60 (SD 46.3) ml for the bicarbonate alone and bicarbonate plus ranitidine series respectively. These differences were not significant. Twenty millilitres of 8.4% NaHCO3 cannot be recommended as a single dose antacid for emergency Caesarean section. Ranitidine plus bicarbonate is considered a reliable antacid regimen to ensure elevation of gastric pH to safe levels.

Topics: Anesthesia, General; Anesthesia, Obstetrical; Antacids; Bicarbonates; Cesarean Section; Emergencies; Female; Gastrointestinal Contents; Humans; Hydrogen-Ion Concentration; Labor, Obstetric; Pneumonia, Aspiration; Pregnancy; Premedication; Ranitidine; Sodium; Sodium Bicarbonate

A commercially available antacid, a mixture of sodium and potassium bicarbonates and citric acid (Alka-Seltzer Effervescent), was evaluated experimentally and clinically for its efficacy in neutralizing 0.1 N HCl and gastric contents. In an in vitro titration study, Alka-Seltzer Effervescent buffered 5-30 times the volume of HCl with a pH between 1.0 and 2.0 to above a pH of 2.5. In an isolated canine pulmonary lobe model, aspiration of the antacid or acid-antacid mixture caused only a mild increase in lobe weight and did not increase intrapulmonary shunting. In the clinical study, when the antacid was given 5-40 min before administration of general anesthesia in a group of patients for emergency surgery, the pH of the gastric contents in each patient was increased to above 4.0. This contrasts with the control group of patients, which showed 50% (P less than 0.05) of the patients were at risk when no antacid was administered. Preoperative administration of Alka-Seltzer effectively increases the pH of the gastric contents in patients undergoing emergency surgery.

Topics: Adolescent; Adult; Aged; Anesthesia, General; Animals; Aspirin; Bicarbonates; Child; Citrates; Dogs; Drug Combinations; Gastric Acid; Gastric Acidity Determination; Humans; In Vitro Techniques; Intraoperative Complications; Middle Aged; Pneumonia, Aspiration; Premedication; Sodium Bicarbonate