Influence of the cold pressor test on the middle cerebral artery circulation

Cold presser test (CPT) evokes generalized activation of the sympathetic ne rvous system (SNS). The activity of SNS may be estimated by monitoring the mean blood velocity (upsilon(m)) in the middle cerebral artery (MCA) by usi ng a transcranial Doppler monitoring system (TCD). To determine the respons e of SNS, we studied the upsilon(m) during CPT. Thirty-four healthy volunte ers, 13 female and 21 male (mean age 34 +/- 9.5 years, range 18 to 55 years ) participated in our study. The experiment consisted of a 5-min baseline p eriod followed by a 3-min immersion of the right hand in ice water. Blood v elocity in both MCA's was monitored by bitemporal 2 MHz probes by using a M ulti-Dop X4. MAP and heart rate (HR) were measured simultaneously by a Fina pres non-invasive blood pressure monitor and a computerized ECG system. End -tidal CO2 (Et-CO2) was measured with an infrared capnograph. To determine upsilon(m) over a chosen time interval the TCD-8 software was utilized. The results showed that during CPT upsilon(m), MAP, and HR increased significa ntly (P < 0.01) for 9.8%, 18.5%, and 3.6%, respectively. Et-CO2 did not cha nge significantly(P > 0.05). The increase of upsilon(m) was also significan tly higher in the stimulated hemispheres (P = 0.005) regarding to unstimula ted ones. The increase of upsilon(m) during CPT was not gender dependent. T o establish the association between variables the models of multivariate re gression were used. Multiple regression CPT model was significant (P < 0.01 ) and fitted data moderately well (R-2 = 0.28). MAP and Et-CO2 were signifi cant in the model (P < 0.01). It seems that the reactivity of the SNS can b e estimated by measuring upsilon(m) with TCD during CPT. (C) 1998 Elsevier Science B.V. All rights reserved.