The volume-dependent effect of phenylephrine on cardiac output in patients under general anesthesia.

Yeung, M.H. (2013) The volume-dependent effect of phenylephrine on cardiac output in patients under general anesthesia. thesis, Medicine.

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Abstract

Background: Phenylephrine, an α1-adrenergic agonist, is widely used during surgery and intensive care settings for its antihypotensive effect. Nevertheless, the effects of phenylephrine are not completely understood yet. In some patients phenylephrine may cause a decrease in cardiac output (CO) due to an increase in afterload through vasoconstriction in the arterioles. In other patients phenylephrine may cause an increase in cardiac output due to an increase in preload through an increase in venous return. These inconsistent effects may be dependent on the volume status of a patient. Objectives: In this pilot study, we wanted to observe the volume dependent effect of phenylephrine on cardiac output in patients under general anesthesia. Materials & methods: Hemodynamic variables (cardiac output, mean arterial pressure, stroke volume, heart rate and systemic vascular resistance) were measured in a non-invasive way with the Nexfin® monitor. In our study protocol, phenylephrine (100μg) and Voluven® (6% hydroxyethyl starch) were used according to normal clinical management. Patients who had elective surgery and underwent general anesthesia were included if phenylephrine and Voluven® were used in the sequence of our study protocol. The effects of a bolus of phenylephrine (100μg) on the hemodynamic variables were analyzed. Furthermore, the hemodynamic changes induced by phenylephrine between two different volume statuses in one patient were compared. Results: Ten patients were eligible to be included in our data analysis. Before Voluven® administration, phenylephrine significantly increased CO (0,51 ± 0,57 L/min; P < 0,006). After Voluven® administration, phenylephrine also significantly increased CO (00,47 ± 0,33 L/min; P < 0,009). The increase in CO before Voluven® administration did not significantly differ from the increase in CO after Voluven® administration (difference of 0,04 ± 0,63 L/min; P = 0,844). Conclusions: This pilot study showed that a bolus of phenylephrine administration (100μg) significantly increased CO in patients who had elective surgery and underwent general anesthesia. We conclude that the beneficial effect of increase in preload is higher than the negative effect of increase in afterload. However, there was no significant difference in increase in CO between before and after Voluven® administration, suggesting that the effects of phenylephrine are not dependent on volume status.

Item Type:	Thesis (Thesis)
Supervisor name:	Scheeren, prof. Dr. T.W.L.
Faculty:	Medical Sciences
Date Deposited:	25 Jun 2020 10:50
Last Modified:	25 Jun 2020 10:50
URI:	https://umcg.studenttheses.ub.rug.nl/id/eprint/1105

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