Effect of Propofol and Clonidine on Cerebral Blood Flow Velocity and Carbon Dioxide Reactivity in the Middle Cerebral Artery

Abstract

This study was designed to evaluate the effects of propofol alone and propofol-clonidine combination on human middle cerebral artery blood flow velocity (Vmca) and cerebrovascular carbon dioxide (CO2) response by using transcranial Doppler ultrasonography. Mean Vmca in response to changes in arterial partial pressure of CO2 (Paco2) was determined under the following conditions: awake (group 1), propofol anesthesia (group 2), and combined propofol-clonidine anesthesia (group 3). Normocapnic, hypercapnic, and hypocapnic values of heart rate, mean arterial pressure, partial end-tidal CO2 pressure, Paco2, and Vmca were obtained. The mean Vmca in groups 2 and 3 was significantly lower than that in group 1 at each level of Paco2. The calculated Vmca at each level of Paco2 was not different between groups 2 and 3. There was a correlation between Paco2 and Vmca in all groups, but in the anesthetized groups the effect of Paco2 on Vmca was attenuated. The present data demonstrated that clonidine-propofol does not change CO2 reactivity compared with propofol alone, but both anesthetics attenuate cerebral blood flow compared with awake controls.

Wpływ propofolu na prędkość przepływu krwi w tętnicy środkowej mózgu (VMCA) u chorych z niepękniętym tętniakiem wewnątrzczaszkowym podczas indukcji znieczulenia ogólnego

“…Our study findings demonstrated that propofol reduced V MCA . Similar results have been reported by many authors analysing V MCA during the use of anaesthetics [53,54]. A reduction in V MCA results from propofol-induced CBF depression [54].…”

Cerebrovascular Reactivity to Carbon Dioxide Under Anesthesia

“…[17][18][19]22 With higher doses of propofol (>150 mg/kg/ min or TCI concentration 6 mg/mL), absolute reactivity is reduced but the relative reactivity remained intact. 20,21,23,24 At doses leading to a broadly equivalent depth of anesthesia, the CVR-CO 2 values are the highest with isoflurane and the lowest with propofol (Fig. 2).…”

“…There were no similar studies under propofol anesthesia (Table 6). 19 Endoh et al, 22 Sakai et al, 23 Mirzai et al 24 ) were used (desflurane data were not included in this figure, as there were no studies where CBF was evaluated using TCD under desflurane anesthesia). CBFV indicates cerebral blood flow velocity; CVR, cerebrovascular reactivity; MAC, minimum alveolar concentration; TCD, transcranial Doppler.…”

“…4 An ideal anesthetic agent for neurosurgical procedures should preserve the CVR-CO 2 . Studies have shown that both inhalational agents [5][6][7][8][9][10][11][12][13][14][15][16] and intravenous agents [17][18][19][20][21][22][23][24] have variable effects on CVR-CO 2 . This effect is further modified by many physiological factors (age, body position) [25][26][27][28][29] and other medical comorbidities (diabetes, hypertension, stroke, intracranial pathologies).…”

A Comparison of Mixed and Central Venous Oxygen Saturation in Patients during and after Cardiac Surgery

“…10 However, the relationship between these variables might be affected by differential effects of general anaesthesia and other changes during the peri-operative period. 11 A number of investigators have described a poor relationship between ScvO 2 and S O 2 , both in septic and surgical patients. [12][13][14][15] The aim of this study was to assess whether the continuous measurement of S O 2 and ScvO 2 using continuous fibreoptic technology would confirm the poor relationship between the variables in patients during and after cardiac surgery.…”