The knee-chest position does not improve the efficacy of ipecac-induced emesis

Previous studies have shown that ipecac-induced emesis, even if instituted very early, removes only a mean of 28% to 45% of an ingested tracer. Because vomiting is an ancient reflex that occurs in mammals, reptiles, and other animals, we speculated that, in humans, maintaining a sitting rather than a horizontal posture during induced emesis might decrease the efficacy of gastric emptying. To test this hypothesis, 20 normal fasting adult subjects underwent induced emesis in the knee-chest position on one day and in the sitting position on another. Twenty-five 100-micrograms tablets of cyanocobalamin were ingested as a tracer along with 250 mL tap water. Ten minutes after tracer ingestion, 30 mL ipecac syrup and 640 mL tap water were swallowed. All resulting vomitus was homogenized, frozen, and later assayed for cobalt using atomic absorption spectrophotometry. There was no difference in mean tracer recovery with the two positions: knee-chest, 47.2% v sitting, 46.9% (paired t test, P greater than .95). Analysis of cobalt recovery for all 40 episodes of emesis revealed a mean of 51.2 +/- 23.7 (SD) micrograms out of 108.7 micrograms total cobalt ingested (95% Cl, 43.6 to 58.7 micrograms). This represented 47.1% of the administered tracer dose (95% Cl, 40.1% to 54.0%). Even if initiated only ten minutes after an ingestion, ipecac-induced emesis removes an average of less than half of an ingested tracer dose, with a high degree of intersubject variability. Horizontal patient positioning does not appear to improve the efficacy of this procedure.