A marked increase in gastric fluid volume during cardiopulmonary bypass

Abstract

Major physiological stress occurs during cardiac surgery with cardiopulmonary bypass. This is related to hypothermia and artificial organ perfusion. Thus, serious gastrointestinal complications, particularly upper gastrointestinal bleeding, sometimes follow cardiac surgery. We have compared the antisecretory effects of a preanesthetic H(2) antagonist (roxatidine, cardiopulmonary bypass-H(2) group, n = 15) and a proton pump inhibitor (rabeprazole, cardiopulmonary bypass-PPI group, n = 15) in patients undergoing cardiac surgery with cardiopulmonary bypass, and also compared in patients undergoing a off-pump coronary artery bypass graft surgery (off-pump cardiopulmonary bypass-H(2) group, n = 15). Gastric pH (5.14 ± 0.61) and gastric fluid volume (13.2 ± 2.4 mL) at the end of surgery in off-pump cardiopulmonary bypass-H(2) groups was significantly lower and higher than those in both cardiopulmonary bypass-H(2) (6.25 ± 0.54, 51.3 ± 8.0 mL) and cardiopulmonary bypass-PPI (7.29 ± 0.13, 63.5 ± 14.8 mL) groups, respectively although those variables did not differ between groups after the induction of anesthesia. Plasma gastrin (142 ± 7 pg/mL) at the end of surgery and maximal blood lactate levels (1.50 ± 0.61 mM) in off-pump cardiopulmonary bypass-H(2) group were also significantly lower than those in both cardiopulmonary bypass-H(2) (455 ± 96 pg/mL, 3.97 ± 0.80 mM) and cardiopulmonary bypass-PPI (525 ± 27 pg/mL, 3.15 ± 0.44 mM) groups, respectively. In addition, there was a significant correlation between gastric fluid volume and maximal blood lactate (r = 0.596). In conclusion, cardiopulmonary bypass may cause an increase in gastric fluid volume which neither H(2) antagonist nor PPI suppresses. A significant correlation between gastric fluid volume and maximal blood lactate suggests that gastric fluid volume may predict degree of gastrointestinal tract hypoperfusion.

Keywords: H2 antagonists; cardiopulmonary bypass; gastric acidity; gastrointestinal ischemia; proton pump inhibitors.

Fig. 1

Changes in gastric pH (A), gastric fluid volume (B), plasma gastrin (C) and maximal blood lactate level (D) at the beginning and end of surgery. Pre: before cardiopulmonary bypass (CPB), Post: after cessation of CPB, Mean ± SEM, *p<0.01 vs Pre, ^#p<0.01 vs OPCAB-H₂ group.

Fig. 2

Correlation between gastric fluid volume and maximal blood lactate (r = 0.596, p<0.01).