Influence of continuous administration of phenylephine versus dobutamine on paraspinal oxygen saturation

Abstract

Introduction: This randomized controlled trial evaluates the effect of continuous administration of phenylephrine versus dobutamine on paraspinal oxygenation, measured by near-infrared spectroscopy (NIRS). Paraspinal NIRS-monitoring evaluates the spinal oxygenation in an indirect, continuous and real-time manner. The influence of these drugs on the paraspinal oxygenation is unknown, but can be highly relevant during major aortic repair.

Methods: This dissertation discusses a preliminary data analysis concerning the first twenty patients included. Phenylephrine or dobutamine were administered continuously during elective arterial dilation procedures of the lower limb. Adhering to a predefined protocol, drug administration was titrated to maintain normotension. The primary outcome variable is the NIRS-measured paraspinal oxygen saturation (rS psO2), this at three distinct paraspinal levels (T3T4 – T9T10 – L1L2), and additionally at the deltoid muscle (rSdO2). A linear mixed modelling approach was used for statistical analysis. This manuscript adheres to the applicable CONSORT guidelines.

Results: Estimated mean relative NIRS-values (e.g. changes from baseline) were calculated at the different locations. We observed an overall positive effect on these oximetry values in the dobutamine administered group, this in contrast with an overall negative effect with phenylephrine administration. Significant differences in estimated mean relative values between the groups were observed at the lumbar level (-0.67% vs 2.97%) and at the deltoid muscle (-2.63% vs 2.01%), with significantly higher values during dobutamine administration.

Conclusion: By means of a mixed modelling approach to estimate mean relative values of rSpsO2 and rSdO2, we compared the effects of the administration of phenylephrine or dobutamine. Noticeable differences between the two groups were observed and seem to favour the use of dobutamine. Besides an overall positive effect of dobutamine administration, significant differences between the two interventions were observed at the lumbar level, in favour of dobutamine administration. Limitations of this analysis are the rather complex modelling, and the lack of implementation of cardiac output variables in the model.