Dopexamine does not improve intestinal mucosal perfusion measured by scanning laser Doppler flowmetry

Background

There is conflicting evidence that dopexamine hydrochloride exerts a selective vasodilating effect upon the gastrointestinal mucosa. Whilst some human studies conducted in the critically ill and in high risk surgical patients have suggested that dopexamine may cause an increase in tonometrically measured gastric intra-mucosal pH (pHi) and an improvement in clinical outcome, this has not been confirmed in other randomised trials. Furthermore, there is no data with regard to dopexamine's influence upon small bowel perfusion. Laser Doppler flowmetry has been used to measure gastrointestinal mucosal blood flow, and the recent advent of scanning laser Doppler flowmetry appears to overcome some of the limitations of the single point method. This study employed this new technique to assess the effect of dopexamine on ileostomy mucosal blood flow.

Method

The study was prospective and double-blind. Fourteen patients with ileostomies were randomised into treatment (n = 7) and placebo groups (n = 7). The stomas were exposed to the air for a period of 20 min whilst the laser Doppler scanner (Moore Instruments, Axminster, Devon, UK) was positioned above the patient at a distance of 32 cm. A laser scan was then made, and the stoma outlined on the photographic image. This equated to over 2500 individual perfusion measurements on the corresponding perfusion image, allowing calculation of mean perfusion units (PUs) within the stomal mucosa. Heart rate and mean arterial pressure were recorded. An intravenous infusion of either dopexamine (2 μg/kg/min) or of a placebo was then commenced and after 30 min the recordings were repeated. The infusion was then stopped and a final set of recordings made after 30 min. The results were analysed using the Mann–Whitney test for non-parametric data.

Results

There were no significant changes in systemic arterial in either group during the study. However, in the dopexamine group there was a significant increase in mean (SD) heart rate from 80 (14) to 94 (7) beats per minute during the infusion and a subsequential fall to 83 (12) beats per minute after its cessation (in both cases P < 0.05). There was no significant change in mucosal perfusion measured using the scanning laser Doppler during dopexamine or placebo infusion (in all cases P > 0.05).

Conclusion

This study is the first to directly measure the influence of dopexamine hydrochloride on ilea mucosal perfusion. The scanning laser Doppler flowmeter produced easily interpreted images of the stomas. Dopexamine caused no demonstrable increase in ileostomy blood flow, and this finding suggests that any improvement in outcome caused by the drug in the critically ill may be caused by an alternative mode of action.

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