Cerebral Hemodynamics and Cerebral Metabolism During Cold and Warm Stress1

Abstract

The purpose of this study was to examine if local thermo-applications affect central nervous reactions. In a crossover study, six normal, healthy volunteers at first received cold packs (Cryogel, 8-12 degrees C; Pino GmbH, Hamburg, Germany) and afterwards hot packs (Parafango, 50-60 degrees C; Pino GmbH), and another six volunteers started with the hot packs and had the cold packs later; both groups administered the hot and cold packs to their thighs. Before, during, and after treatment, cerebral blood flow velocity (CBFV) in the middle cerebri-artery (MCA) was measured continuously by transcranial Doppler sonography, whereas cerebral respiratory chain enzyme cytochrome aa3 (cCytaa3) and cerebral oxygen saturation (cHbO2) were measured by transcranial near infrared spectroscopy in frontal brain tissue. Furthermore, CO2 end-tidal and arterial blood pressure (noninvasive) were also measured. Six other volunteers received only one treatment; therefore, 15 measurements with cold and 15 measurements with hot packs were performed. During application of cold packs, a decrease of cHbO2 of 10.5% (P < 0.001) and cCytaa3 of 6.7% (P < 0.001) was found, whereas the CBFV(MCA) increased significantly (3.9%; P < 0.001) between preliminary and post-stimulus periods. When cold packs were removed, a significant increase of the cHbO2 (16.9%; P < 0.001) and cCytaa3 (9.7%; P < 0.001) was measured. With these values, cHbO2 and cCytaa3 showed an overshooting counterreaction beyond the initial level. When applying the hot packs, a contrary course of the parameters was found. cCytaa3 showed a significant increase of 9.3% (P < 0.001) at the end of the stimulus phase and a decrease of 1.9% (P = 0.02) during the post-stimulus period. The correlating increase of cHbO2 was significant at 13.7% (P < 0.005). At the end of the post-stimulus phase, a significant decrease of cHbO2 at 1.9% (P = 0.004) was recorded. With Parafango applications, a significant decrease of CBFV(MCA) at 6.9% (P < 0.001) was measured at the end of the stimulus in comparison with the preliminary phase. Crossover analysis showed no significant period effects and intraindividual changes between period and treatment. Therefore, both treatments can be compared within the individual using paired t test. Local cold and warm stimuli influence the cerebral hemodynamics and cerebral metabolism. Cerebral hemodynamics (CBFV(MCA) in comparison with cerebral metabolism (cCytaa3, cHbO2) show opposite reactions under thermo-stress. Of special interest is the overshooting counter-regulation of cerebral metabolism after cold stimulation. These effects may open new thermotherapeutic aspects in central nervous system diseases.

Skin cooling maintains cerebral blood flow velocity and orthostatic tolerance during tilting in heated humans

“…This decrease in cerebral blood flow velocity is somewhat higher than the previously reported decrease of 6.9% during minor heating via application of hot packs sufficient to increased T sl by 0.2°C (6). Comparison of physiological responses between these studies is difficult because of different magnitudes of heating, different modes of heating, and the lack of reporting of efferent responses (i.e., skin blood flow and sweat rate) in the prior study (6). Nevertheless, the mechanism responsible for the reduction in cerebral blood flow velocity is unclear; however, heat-induced alterations in perfusion pressure cannot be excluded.…”

“…It is interesting to note that increasing core temperature 0.8-0.9°C, independent of orthostatic stress, significantly decreased cerebral blood flow velocity by ϳ12%. This decrease in cerebral blood flow velocity is somewhat higher than the previously reported decrease of 6.9% during minor heating via application of hot packs sufficient to increased T sl by 0.2°C (6). Comparison of physiological responses between these studies is difficult because of different magnitudes of heating, different modes of heating, and the lack of reporting of efferent responses (i.e., skin blood flow and sweat rate) in the prior study (6).…”

“…Thus these responses occurred when the individual remained hyperthermic as indicated by the elevated core temperature. Others have reported that the application of cold packs increases cerebral blood velocity in normothermic individuals (6). Hence, rapid skin-surface cooling possibly maintains arterial blood pressure and increases cerebral blood velocity during a heat stress, thereby improving orthostatic tolerance in the heated human.…”

“…Nevertheless, syncope during orthostatic stress will always occur if cerebral perfusion is sufficiently reduced (31). Interestingly, mild heating itself has been reported to reduced cerebral blood flow velocity (6).…”

Transcranial Doppler Ultrasound in the Acute Phase of Aneurysmal Subarachnoid Hemorrhage

“…These results are consistent with the hypothesis that vasospasm during the acute phase of SAH is associated with a systemic inflammatory response. We did not find an association between increased mBFV and other biological variables that have been related to increased TCD velocities, such as low hematocrit and body temperature [11, 12]. …”