Effect of Clonidine Supplementation on Jugular Bulb Oxygen Saturation and Carbon Dioxide Reactivity during Desflurane Anesthesia / 대한마취과학회지

BACKGROUND: The alpha2-agonist clonidine is an adjunct in general anesthesia. Clonidine constricts cerebral arteries and decreases cerebral blood flow (CBF), but does not alter cerebral metabolic rate (CMR). Thus cerebral ischemia is possible due to CBF/CMR imbalance. This study was designed to prove the effects of clonidine bolus up on CBF and CO2 reactivity in desflurane anesthesia. METHODS: Thirty patients were divided into a clonidine group (n = 15) and a control group (n = 15). Anesthesia was induced with thiopental and pancuronium, and maintained with 50% N2O/O2/ Desflurane. The jugular bulb was cannulated to measure jugular bulb oxygen saturation (SjO2). MAP and SjO2 were measured after induction, after clonidine (2 microgram/kg) or normal saline administration and during hyperventilation. RESULTS: After clonidine administration, MAP decreased from 95.7+/-9.8 mmHg to 81.1+/-6.3 mmHg and was 79.9+/-5.0 mmHg during hyperventilation. In the control group, the corresponding MAP values 95.7+/-9.8 mmHg, 81.1+/-6.3 mmHg and 79.9+/-5.0 mmHg. After clonidine administration, SjO2 was decreased from 84.7+/-3.7% to 81.1+/-5.2%, and was 71.5+/-8.4% during hyperventilation (P = 0.003, P = 0.000) and in control group, there were 95.7+/-9.8%, 81.1+/-6.3% and 79.9+/-5.0%, respectively. CO2 reactivity was expressed as a change of SjO2 per unit change of PaCO2, 1.15+/-1.19%/mmHg versus 1.43+/-0.98%/mmHg (P = 0.49). CONCLUSIONS: During desflurane anesthesia, clonidine-induced constriction of the cerebral arteries was demonstrated but CO2 reactivity was well preserved.

Reliability of rSO2 to Measure CO2 Reactivity of Cerebral Vasculatures during Desflurane-N2O Anesthesia / 대한마취과학회지

BACKGROUND: Near infrared spectroscopy (NIRS) to monitor regional cerebral oxygen saturation (rSO2) is a noninvasive and simple modal ity in clinical use. The ability of rSO2 as an index of cerebral oxygenation has been well demonstrated. However, the reliability of rSO2 to reflect the changes of cerebral vascular reactivity in the changes of arterial partial pressure of CO2 (PaCO2) has not been established. The aim of this study was to verify the reliability of rSO2 to measure the CO2 reactivity of cerebral vasculatures. METHODS: Twenty healthy adult patients undergoing general anesthesia were enrolled in this study. Anesthesia was induced with propofol and maintained with desflurane/N2O. Respiration was mechanically controlled. The radial artery and jugular bulb were cannulated. The sensor of the NIRS was attached to the ipsilateral forehead. During normocapnia (PaCO2 40 +/- 1.3 mmHg) and hypocapnia (PaCO2 30 +/- 2.4 mmHg), blood was obtained from the radial artery and jugular bulb and analyzed. rSO2 was compared with fSO2 (estimated field oxygen satuation), and the gold standard of tissue oxygen saturation. fSO2 was calculated from the following equation: fSO2 = 0.75 SjO2 + 0.25 SaO2. RESULTS: rSO2 significantly correlated with fSO2 (P = 0.000, r2 = 0.56). A bias of - 5.8% with a precision 12.94% was found. CONCLUSIONS: We concluded that rSO2 can be a reliable predictor to measure CO2 reactivity of cerebral vasculatures during normocapnia and hypocapnia.

Effects of propofol-alfentanil and sevoflurane-N_2O anesthesia on cerebrovascular CO_2 reactivity / 中华麻醉学杂志

Objective To compare the effects of propofol-alfentanil and sevoflurane-N2O anesthesia on cerebral vascular reactivity to the changes in carbon dioxide (CO2). Methods Forty ASA class I - II patients undergoing abdominal operations, were randomly divided into two groups. In group I (n = 20), anesthesia was maintained with infusion of propofol at 0.1mg.kg-1 .min-1, plus alfentanil at 1ug.kg-1. min-1. In group II (n = 20), anesthesia was maintained with 1 % sevoflurane and N2 O-O2 (N2 O: O2 = 3: 2). Mean arterial blood pressure (MAP), heart rate (HR), body temperature (T), end-tidal CO2 tension (PETCO2 ), sevoflurane concentrations, pulse O2 saturation (SpO2 ) and the parameters of the middle cerebral artery blood flow, including mean blood flow velocity (Vm), diastolic blood flow (Vd), pulse index (PI) and resistance index (RI), were measured at following occasions: after intubation and when PETCO2 reached 40, 45, 50, 45, 40, 35, 30 and 40mmHg, which was achieved through adjusting mechanical ventilation. The CO2 reactivity index (CRI) was calculated as delta Vm/delta PETCO2 ratio. Results CRI and Vm were lower in propofol--alfentanil group than sevoflurane-N2O group (P

The Effects of Fentanyl and Isoflurane on the Cerebrovascular CO2 Reactivity / 대한마취과학회지

The changes of arterial carbon dioxide partial pressure considerably influence cerebral blood flow and different anesthetic agents have different effects on cerebrovascular physiology. However the importance of these differences in neuroanesthetic practice are unclear. Transcranial Doppler ultrasonography allows the noninvasive direct measurements of cerebral blood flow velocity and direction in the basal brain arteries. The authors performed transcranial Doppler ultrasonography to measure the blood flow velocity of middle cerebral artery in 12 patients who were anesthetized with 10 mcg/kg of fentanyl and 66 % nitrous oxide in oxygen(fentanyl group) and 12 patients with 1.0 vo1% isoflurane and 66 % nitrous oxide in oxygen(isoflurane group) during normocapnia(P(ET)CO(2)=38 mmHg) and hypocapnia(P(ET)CO(2)=28 mmHg)state. The carbon dioxide reactivity was expressed as the changes in mean blood flow velocity per unit changes in endtidal carbon dioxide partial pressure(P(ET)CO(2)). Mean blood flow velocity of middle cerebral artery decreased from 46.6+/-8.9 cm/s to 30.0+/-5.3 cm/s in the fentanyl group and 42.7+/-5.6 cm/s to 32.5+/-4.6 cm/s in the isoflurane group as the P(ET)CO(2) decreased from 38 mmHg to 28 mmHg. There was a significant difference between the CO2 reactivity of fentanyl group(1.7+/-0.7 cm/s/mmHg) and isoflurane group(1,0+/-0,2 cm/s/mmHg) (p<0.05). It is concluded that hyperventilation is more likely to affect cerebral blood flow during fentanyl-nitrous oxide anesthesia than during isoflurane-nitrous oxide anesthesia.

The Effect of Stellate Ganglion Block on Mean Blood Flow Velocity and Carbon Dioxide Reactivity of the Middle Cerebral Artery / 대한마취과학회지

We studied the effect of stellate ganglion block on the mean blood flow velocity and carbon diaxide reactivity of the middle cerehral artery in nine healthy volunteers. Mean blood flow velocity of the right middle cerebral artery was measured under normocapnia and carbon dioxide reactivity to end-tidal PCO2 of 30 mmHg, 40 mmHg, and 50 mmHg was assessed before and after right stellate ganglion block. End-tidal PCO2 was controlled by hyperventilation and rebthing technique. Mean blood flow velocity was measured using transcranial Doppler sonography, and carbon dioxide reactivity was expressed as the percentage change in mean blood flow velocity per unit change in end-tidal PCO2. There was no difference in mean blood flow velocity under normocapnia (37.7+/-1.1 mmHg) between the values measured before stellate ganglion block (60.3+/-4.9 cm/sec) and the values measured after stellate ganglion block (58.6+/-4.9 cm). Mean blood flow velocity increased as end-tidal PCO2 increased from 30 mmHg to 40 mmHg, and from 40 mmHg to 50 mmHg (p<0.01) both before and after stellate ganglion block. Carbon dioxide reactivity of mean blood flow velocity did not change after stellate ganglion block. Heart rate decreased from 77.1+/-3.5 beats/min to 70+/-2.5 beats/min when end-tidal PCO2 was controlled from 30 mmHg to 40 mmHg after stellate ganglion block (p<0.05). Mean arterial blood pressure did not change after stellate ganglion block at any end-tidal PCO2 level. These results suggest that stellate ganglion block does not induce the change of mean blood flow velocity and carbon dioxide reactivity of the middle cerebral artery.

Transcranial Doppler Study in Carbon Dioxide Reacitivity of Middle Cerebral Blood Flow Velocity During Hypothermic Nonpulsatile Cardiopulmonary Bypass / 대한마취과학회지

The recording of middle cerebral artery (MCA) flow veloeity by transcrsnisl Doppler technique offers s new, noninvasive, and continuous technique for studies of cerebral circu lation. The influence of changes in PaCO2 on MCA flow velocity were observed during hypothermic cardiopulmonary bypass(CPB) surgery by means of transcranial Doppler tech- niques. In ten patients who were undergoing hypothermic CPB surgery, the right MCA flow velocity was measured before initiation of CPB(prebypass period) and after the termination of CPB (postbypass period). During steady state CPB(constant hematocrit, constant temperature, and constant total pump flow), baseline MCA flow velocity(CPB I period) was measured and then repeated after specific alteration of PaCO2 achieved by changing of fresh gas flow to oxygenetors(CPB II period). And carbon dioxide reactivity defined as percent change of MCA flow velocity per mmHg changes in PaCO2 was observed during stable hypothermic CPB. MCA flow veocity showed no statistical difference between the prebypass value(56.9+/-13.5 cm/sec) and the postbypass value(64.7+/-29.7 cm/sec). PaCO2 of 20.5+/-2.5 mmHg was associated with MCA flow velocity of 25.2+/-10.1 cm/sec in the CPB I period while PaCO2 of 27.1+/-3.5 mmHg was associated with MCA flow velocity of 35.3+/-12.9 cm/sec. MCA flow velocity carbon dioxide reactivity during steady state hypothermie CPB was 6.68+/-2.26 %/ mmHg. These results have demonstrated that the response of MCA flow velocity to changes in PaO2 was well maintained during hypothermic CPB and the use of transcrsnial Doppler would give valuable results in the study of cerebral circulation during hypothermic CPB.