Effect of Controlled Hypotension Combined with Hemodilution on Gastric Intramural pH

Abstract

Study Objective: To evaluate the effect of controlled hypotension combined with hemodilution on gastric intramural pH in the clinical setting. Design: Randomized, prospective study. Setting: Inpatient surgery at Nagasaki Rosai Hospital. Patients: 30 ASA physical status I and II patients scheduled for total hip arthroplasty. Interventions: Patients were randomly divided into two groups. Group A (n = 15) received controlled hypotension with mild hemodilution. Group B (n = 15) received controlled hypotension with moderate hemodilution. Hemodilution was carried out after induction of anesthesia. Drawn blood was replaced with 6% hydroxyethyl starch solution. Final hematocrit values were 32 ± 2% (mean ± SD) in Group A and 23 ± 2% in Group B. Controlled hypotension was induced with prostaglandin E 1 (PGE 1) to maintain mean arterial blood pressure at 55 mmHg for 80 minutes. Measurements and Main Results: Measurements included gastric intramural pH (pHi), arterial blood pH (pHa), and plasma lactate. These indices were measured before hemodilution, after hemodilution, 80 minutes after starting hypotension, 60 minutes after recovery from hypotension, and on the first postoperative day. The value of pHi was measured by tonometry. The pHa and lactate values showed no change in either Group A or Group B throughout the time course. Gastric pHi values showed no change in Group A throughout the time course. The pHi value in Group B showed a significant decrease from 7.420 ± 0.028 to 7.339 ± 0.034 (p < 0.05) after hemodilution, while it showed no further decrease at 80 minutes after starting hypotension (7.331 ± 0.039) and 60 minutes after recovery from hypotension (7.330 ± 0.048). Conclusion: The results suggest that moderate hemodilution, such as 23% of hematocrit value, might impair oxygenation in gastrointestinal mucosa, whereas controlled hypotension induced by PGE 1 combined with the hemodilution would not increase this impairment.