# Preoperative Oral Rehydration Therapy Mitigates Circulatory Suppression During Anesthesia Induction: A Retrospective Study of 1,000 Elective Surgery Cases Exploring Appropriate Preoperative Intake Volume

## TL;DR

This study found that drinking more preoperative oral rehydration solution before surgery can reduce the need for vasopressors during anesthesia.

## Contribution

The study identifies an optimal preoperative oral rehydration solution intake volume (800-1,500 mL) that reduces vasopressor use during anesthesia induction.

## Key findings

- ORS intake of ≥800 mL was significantly associated with lower vasopressor administration rates.
- ORS intake of <800 mL increased vasopressor use to 52%, while ≥800 mL reduced it to 40%.
- Higher risk of hypotension was observed in older, underweight patients and those with higher ASA scores.

## Abstract

Background and objective

Preoperative oral rehydration therapy has been introduced as an alternative to conventional IV fluid management. It helps shorten the preoperative fasting period, prevents and corrects dehydration before surgery, and supports circulatory stability during anesthesia induction. Appropriate preoperative oral rehydration solution (ORS) intake may help alleviate circulatory fluctuations. This study aimed to examine the relationship between ORS intake volume and circulatory fluctuations during anesthesia induction in 1,000 elective surgery cases.

Methods

We conducted a retrospective study at an independent administrative institution affiliated with the Kanagawa Prefectural Hospital Organization. We examined 1,000 patients who underwent elective surgery under general anesthesia between April 1, 2021, and December 27, 2021. Eligible patients were provided with three 500 mL bottles of ORS within 12-18 hours before surgery. Patients were classified into two groups: those who received vasopressors after anesthesia induction (V group) and those who did not (N group). Demographic and clinical data were obtained from electronic medical and anesthesia record systems. We examined whether differences in patient demographics and anesthesia-related factors influenced vasopressor administration. The primary outcome was the dose-response relationship between ORS intake volume and vasopressor administration, while secondary outcomes included identifying patient- and anesthesia-related factors influencing vasopressor use.

Results

Of the 1,000 patients enrolled, 473 (47%) received vasopressors between anesthesia induction and the start of surgery. ORS intake of <800 mL increased the rate of vasopressor administration from 50% to 52%. In contrast, ORS intake of ≥ 800 mL reduced the rate of vasopressor administration, reaching a minimum of 40%. Multivariable analysis revealed that ORS intake of ≥ 800 mL was significantly associated with a lower frequency of vasopressor administration.

Conclusions

Appropriate preoperative ORS intake may help mitigate circulatory suppression during anesthesia induction. Analysis of 1,000 patients undergoing elective surgery revealed an association between an ORS intake volume of 800-1,500 mL and reduced vasopressor requirements during anesthesia induction. The risk of hypotensive events was particularly high in patients receiving total IV anesthesia with combined epidural analgesia, older patients, underweight patients, those who skipped dinner the night before surgery, and patients with higher American Society of Anesthesiologists Physical Status classification.