Effects of anaesthesia-induced hypotension and phenylephrine on plasma volume expansion by hydroxyethyl starch: A...

Changes in blood haemoglobin concentration indicate plasma volume expansion following hydroxyethyl starch (HES) infusion, but may be affected by vascular tone and HES-induced shedding of the endothelial surface layer (ESL). We hypothesised that anaesthesia-induced hypotension enhances changes in plasma volume as assessed by blood haemoglobin concentration (ΔPV_Hb , %) following HES infusion.

Fifty-two patients undergoing abdominal surgery were randomised to receive a continuous infusion of saline (S group) or phenylephrine to restore vascular tone (P group) (n = 26 each). Both groups received an infusion of 8 mL/kg 6% HES solution after induction of general anaesthesia. We compared ΔPV_Hb at the end of fluid infusion (15 minutes) and 15 minutes later (30 minutes) between the two groups. We assessed changes in ESL structure by measuring plasma concentrations of hyaluronate and syndecan-1. P < .05 was considered statistically significant.

Mean arterial blood pressure was lower in the S group approximately by 30-40% compared to the P group (P < .001). ΔPV_Hb was larger in the S group compared to the P group at 15 minutes (24.9 [5.2] % vs 19.0 [5.2] %; P < .001) and 30 minutes (26.5 [5.9] % vs 16.9 [6.6] %; P < .001). There were no clinically significant differences in plasma concentrations of hyaluronate and syndecan-1 with time and between the groups.

Increased volume expansion of circulating plasma following HES infusion in anaesthesia-induced hypotension compared to when blood pressure is restored by phenylephrine may result from an attenuation of transcapillary fluid filtration, rather than ESL shedding. UMIN Clinical Trial Registration Number: UMIN000017394 (http://www.umin.ac.jp/ctr/index.htm).