To evaluate the effect of volume of aspirates with different pHs on mortality associated with pulmonary aspiration, hydrochloric acid solutions were injected into the tracheas of 336 Sprague-Dawley rats. The rats were divided randomly into 33 groups, were observed for 96 hr after aspiration, and were not resuscitated. Deaths were divided into two groups: early, less than 30 min after aspiration, and late, greater than 4 hr after aspiration. Late deaths, accounting for 22% of all fatalities, occurred exclusively in animals aspirating solutions with a pH less than 2.5. These late deaths indicated progressive lung damage as opposed to acute cardiorespiratory failure, which early deaths suggested. Low volume pulmonary aspirates (0.3 ml/kg) with extremely low pH (1.0) resulted in a high mortality rate (90%). Conversely, higher volume pulmonary aspirates (1.0-2.0 ml/kg) with a higher pH (greater than or equal to 1.8) resulted in a low mortality rate (14%). These data demonstrate an important interaction between pH and volume of aspirates: even low volumes have a high mortality rate if pH is very low, whereas if gastric fluid is effectively buffered, then much higher volumes than previously thought can be tolerated. This suggests that the routine use of nonparticulate antacids may be indicated in patients at risk from aspiration of stomach contents and should not be withheld because of concern of increasing gastric volume.

Pulmonary Aspiration — Effects of Volume and pH in the Rat

Management of the pregnant oral and maxillofacial surgery patient

Thirty-two healthy term parturients undergoing elective cesarean section randomly received either no antacid (n = 10), 30 ml of 0.3 molar sodium citrate less than 60 min preoperatively (n = 11), or 30 ml of 0.3 molar sodium citrate longer than 60 min preoperatively (n = 11). Immediately after delivery, the stomach was emptied as completely as possible through a #18 Salem Sump tube passed orally. Mean gastric pH in the three groups was 1.8 +/- 2.7 (SD), 5.0 +/- 1.5, and 2.7 +/- 1.2, respectively. Gastric pH was significantly higher in the short interval group than in either the control group or in patients receiving their sodium citrate more than 60 min in advance. Gastric volumes were similar. All control patients had a gastric pH less than 2.5. Nine percent of patients receiving sodium citrate less than 60 min in advance and 50% of patients receiving their sodium citrate longer than 60 min in advance had a pH of less than 2.5. Volumes exceeding 25 ml occurred with equal frequency. No patient in the short interval group had a combination of both pH of less than 2.5 and a volume exceeding 25 ml. This combination occurred with equal frequency in control patients (64%) and in those patients receiving their sodium citrate more than 60 min in advance (50%). We conclude that sodium citrate effectively increases gastric pH when given less than 60 min prior to the induction of anesthesia.

Sodium citrate pretreatment in elective cesarean section patients.

SUMMARY One hundred and forty-seven patients undergoing elective or emergency Caesarean section under general anaesthesia were allocated randomly to three groups: group 1 (n = 28) received no premedication; group 2 (n = 58) received 0.3-molar sodium citrate 15 ml (sodium citrate 1.16 g); group 3 (n = 61) received effervescent cimetidine-sodium citrate combination (cimetidine 400 mg with sodium citrate 0.9 g) after entering the operating room. Gastric pH was measured at tracheal intubation (pH1) and extubation (pH2). Mean pH1 and mean pH2 values in group 1 were, respectively, 2.25 (SD 1.35) and 2.83 (1.64). Mean pH1 and pH2 values in group 2 were, respectively, 4.38 (1.44) and 4.57 (1.51). In group 3 mean pH1 and pH2 values were, respectively, 5.07 (1.13) and 5.37 (1.30). Percentages of patients with pH1

Lynn Spohr

Papers

The effectiveness of sodium citrate as an antacid.

The Effectiveness of Sodium Citrate as an Antacid