Volatile anesthetic agents and vascular communication in the microcirculation of the hamster cheek pouch

Background: There is communication between tissue and the vascular network involved in regulating distribution of blood flow. Signals generated by the tissue are communicated upstream to create a coordinated network response in unison with other controllers of blood flow, such as myogenic and flow-dependent responses. Methods: This vascular communication was modeled with the microapplication of methacholine (10^-4 M) or potassium chloride solution (KCl; 100 mM) to arterioles (40-60 μm in diameter) of the cheek pouch of anesthetized hamsters and viewed with videomicroscopy. Local and conducted (500 μm upstream) responses were measured. Responses to KCl and methacholine were then repeated in the presence of an anesthetic agent. Results: Halothane and isoflurane increased the resting diameter of the arterioles. They also decreased the methacholine-initiated dilations. To test for the effects of increased resting diameter on the dilations, 0%, 5% and 10% oxygen alone was applied to the pouch to alter the tone, and the methacholine responses were repeated. The dilations decreased with oxygen- induced increases in resting diameter, but the conducted dilation decreased to a lesser extent than was seen with the volatile anesthetic agents. Neither halothane nor isoflurane decreased constrictions caused by KCl. Conclusions: Decreased methacholine-initiated conducted dilations caused by halothane and isoflurane were not due to decreases in cell-cell communication because KCl conducted responses persisted. Therefore, cell-cell vascular communication appears intact in the presence of clinical concentrations of halothane and isoflurane.