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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 sup -4 M) or potassium chloride solution (KCl; 100 mM) to arterioles (40-60 micro meter in diameter) of the cheek pouch of anesthetized hamsters and viewed with videomicroscopy. Local and conducted (500 micro meter upstream) responses were measured. Halothane or isoflurane (1%, 2%, and 3%) was equilibrated with the superfusion solution and applied to the entire tissue. 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.

(C) 1998 American Society of Anesthesiologists, Inc.