Abstracts of Posters Presented at the International Anesthesia Research Society; 72nd Clinical and Scientific Congress; Orlando, FL; March 7-11, 1998: Cardiovascular Anesthesia
INTRODUCTION: Aortic cross clamping reduces or abolishes blood flow to the pelvis and lower extremities distal to the clamp. The haemodynamic responses to aortic cross clamping consist of an increase in arterial pressure and systemic vascular resistance with a reduction in cardiac output. Attention has recently focused on the adequacy of splanchnic bed perfusion during acute changes in cardiac output. The objectives of this study were to assess the effects of dopexamine (a dopaminergic (DA-1) and beta2 adrenoreceptor agonist) infusion on haemodynamic function, tissue oxygen delivery and consumption, splanchnic perfusion and gut permeability following aortic cross-clamp and release.
METHODS: Following institutional ethics committee approval, twenty four patients scheduled for elective infrarenal abdominal aortic aneurysm repair (ASA physical status II-IV) were studied in two centres. Patients were randomly assigned to one of two treatment groups.
Group I received a dopexamine infusion titrated from 0.5[micro sign]g kg-1 min-1 up to 2[micro sign]g kg-1 min-1. Group II received a placebo infusion titrated in the same volumes following induction of anesthesia. Measured and derived haemodynamic data; tissue oxygen delivery and extraction, intra-mucosal gastric pH and gut permeability were recorded at set time points throughout the procedure.
RESULTS: Dopexamine infusion (0.5 -2[micro sign]g kg-1 min-1) was associated with significantly improved haemodynamic functions. Cardiac index and tissue oxygen delivery increased from 3.1 to 4.0L min-1 m-2 and 395 to 483ml min-1 m-2 respectively while systemic vascular resistance index decreased from 1843 to 1183 dyn.s cm-5 m-2 Compared with the control group, dopexamine infusion was associated with significantly reduced systemic vascular resistance index, mean arterial pressure and oxygen extraction during aortic cross clamping (p<0.05). Baseline pHi values remained above 7.33 during aortic cross clamping in the twelve patients included in this study. However, pHi values decreased to 7.25 in the control group compared to 7.30 in the dopexamine-treated patients 30 minutes following cross clamp release. The lactulose/rhamnose permeation ratio was elevated above 0.2 in both groups (reference values 0-0.05)
CONCLUSIONS: The study suggests that dopexamine infusion (0.5 -2 [micro sign]g. kg-1 min-1) may enhance haemodynamic function, tissue oxygenation and gastric mucosal pHi values during cross clamping in patients undergoing elective abdominal aortic aneurysm repair.