The influence of controlled hypotension on splanchnic mucosal perfusion using gastric tonometry in patients undergoing resection of meningioma.

BACKGROUND

The aim of our research was to evaluate the influence of general anesthesia with controlled nitroglycerin-induced hypotension on splanchnic mucosal perfusion using gastric tonometry.

METHODS

In six patients (1 female, 5 males, median age 46 years, range 32-62) undergoing elective resection of meningiomas, measurements of gastric mucosal perfusion were taken by nasogastric tonometry. Controlled hypotension was initiated after craniotomy and terminated prior to hemostasis procedures. The mean arterial blood pressure (MAP) was maintained 25-30% below initial parameters during controlled hypotension. The adequacy of perfusion was defined by the intramucosal pH (pHi) and the difference between arterial and intramucosal pH (pHGAP). All parameters were analyzed before the induction of controlled hypotension, after the 1st, 2nd, and 3rd hour, and 1 hour after the termination of controlled hypotension.

RESULTS

The MAP decreased during controlled hypotension by ca. 26.5% (min. 21.1%; max 31.6%). The lower MAP was accompanied by a statistically significant increase in heart rate. A significant increase from baseline in regional prCO2 was seen after the 1st, 2nd, and 3rd hour of controlled hypotension. Intramucosal pH values decreased significantly during the same period, from 7.428+/-0.032 to 7.372+/-0.015. Despite these statistically significant differences during controlled hypotension, the pHi values were always greater than 7.35, and the pHGAP values were lower than 0.05, which were recognized as being within the normal range.

CONCLUSIONS

Controlled hypotension allows accurate evaluation of the blood flow quality at the level of microcirculation. Mild controlled hypotension slightly alters splanchnic mucosal perfusion, but does not lead to ischemia and hypoxia in tissues.