Georg von Knobelsdorff

Physostigmine Prevents Postanesthetic Shivering As Does Meperidine or Clonidine

BackgroundPostanesthetic shivering develops in as many as one half of patients recovering from isoflurane anesthesia. Cholinergic stimulation of the hypothalamic-pituitary-adrenal axis and adrenal medulla by physostigmine enhances secretion of arginine vasopressin, epinephrine, and norepinephrine. B

The Effect of Remifentanil on Cerebral Blood Flow Velocity

In the present study, we investigated the effect of remifentanil on cerebral blood flow velocity (CBFV).We investigated 20 patients (ASA physical status III) scheduled for elective coronary artery bypass graft surgery. Anesthesia was induced with remifentanil 5 [micro sign]g/kg IV (Group 1, n = 10) or 2 [micro sign]g/kg IV (Group 2, n = 10) and was maintained with 3 [micro sign]g [center dot] kg-1 [center dot] min-1 IV (Group 1) or 1 [micro sign]g [center dot] kg-1 [center dot] min-1 IV (Group 2). Pancuronium (0.1 mg/kg IV) was administered for muscle relaxation. Assisted ventilation followed by controlled ventilation via a mask was performed with the PaCO2 kept constant. Mean cerebral blood flow velocity (Vmean) was measured in the middle cerebral artery using a transcranial Doppler sonography system. Mean arterial pressure (MAP) was kept constant by the IV administration of norepinephrine. Measurements were made at baseline and every minute after remifentanil infusion for 10 min. Data were analyzed by using analysis of variance and a post hoc t-test (P < 0.05). Heart rate, MAP, and PaCO2 did not change over time in either group. Vmean did not change in Group 2. In contrast, there was a 31% decrease of Vmean in Group 1 (P < 0.05). The results show that large-dose, but not moderate-dose, remifentanil reduces CBFV unrelated to any changes in systemic hemodynamics in isocapnic cardiac patients. Implications: Transcranial Doppler sonography was used to monitor remifentanil-induced changes in cerebral perfusion. We found that large doses of remifentanil reduced cerebral blood flow velocity despite constant perfusion pressure. This may implicate a central mechanism for cerebral hemodynamic effects of remifentanil. (Anesth Analg 1998;87:569-73)

Hypercapnia prevents jugular bulb desaturation during rewarming from hypothermic cardiopulmonary bypass.

Background The rewarming period of hypothermic cardiopulmonary bypass (CPB) is associated with reduced jugular bulb venous oxygen saturation (SjO (2)). This study investigates the effects of normocapnia vs. hypercapnia on changes in SjO2 during rewarming from hypothermic CPB for coronary artery bypass graft in patients classified as American Society of Anesthesiologists physical status III. Methods Anesthesia was induced and maintained with fentanyl, midazolam, and continuous infusion of etomidate. Hypothermic CPB (27 [degree sign]C) was managed according to alpha‐stat conditions. The SjO2 percentage was measured using a fiberoptic catheter placed in the right jugular bulb via the right internal jugular vein. Data were recorded before and during the rewarming period. Patients were assigned to a normocapnic (PaCO(2): 36–40 mmHg, n = 10) or hypercapnic (PaCO(2): 45–50 mmHg, n = 10) PaCO(2) regimen during rewarming. Results The maximum reduction of SjO2 occurred during rewarming with the jugular bulb temperature at 35–36 [degree sign]C. In contrast, SjO (2) did not change during rewarming from hypothermia in hypercapnic patients. Conclusions These results show that mild hypercapnia prevents the desaturation of SjO2 seen with the normocapnic group during the rewarming period from hypothermic CPB. These data suggest that mild hypercapnia during rewarming from CPB is associated with a better balance between cerebral oxygen supply and demand.

Topography of Clonidine-induced Electroencephalographic Changes Evaluated by Principal Component Analysis

Background Principal component analysis is a multivariate statistical technique to facilitate the evaluation of complex data dimensions. In this study, principle component analysis was used to reduce the large number of variables from multichannel electroencephalographic recordings to a few components describing changes of spatial brain electric activity after intravenous clonidine. Methods Seven healthy volunteers (age, 26 ± 3 [SD] yr) were included in a double-blind crossover study with intravenous clonidine (1.5 and 3.0 &mgr;g/kg). A spontaneous electroencephalogram was recorded by 26 leads and quantified by standard fast Fourier transformation in the &dgr;, &thgr;, &agr;, and &bgr; bands. Principle component analysis derived from a correlation matrix calculated between all electroencephalographic leads (26 × 26 leads) separately within each classic frequency band. The basic application level of principle component analysis resulted in components representing clusters of electrodes positions that were differently affected by clonidine. Subjective criteria of drowsiness and anxiety were rated by visual analog scales. Results Topography of clonidine-induced electroencephalographic changes could be attributed to two independent spatial components in each classic frequency band, explaining at least 85% of total variance. The most prominent effects of clonidine were increases in the delta band over centroparietooiccipital areas and decreases in the alpha band over parietooccipital regions. Clonidine administration resulted in subjective drowsiness. Conclusions Data from the current study supported the fact that spatial principle component analysis is a useful multivariate statistical procedure to evaluate significant signal changes from multichannel electroencephalographic recordings and to describe the topography of the effects. The clonidine-related changes seen here were most probably results of its sedative effects.

Prolonged rewarming after hypothermic cardiopulmonary bypass does not attenuate reduction of jugular bulb oxygen saturation

OBJECTIVE This study investigates the effects of rapid versus graded rewarming on decreases in jugular bulb oxygen saturation (SjO2) during cardiopulmonary bypass (CPB) in a prospective nonrandomized and nonblinded design. SETTING AND PARTICIPANTS At the Department of Anesthesiology (University Hospital Eppendorf, Germany), 28 patients (ASA III) undergoing coronary artery bypass graft were investigated. INTERVENTION CPB was managed according to alpha-stat conditions during moderate hypothermia (27 degrees C). In group 1 (n = 17), rewarming was performed by increasing the perfusate temperature to 36 degrees C within 7 minutes, in group 2 (n = 11) within 15 minutes. MEASUREMENTS AND MAIN RESULTS SjO2 was measured by a fiberoptic catheter placed in the right jugular bulb. Data were recorded before and 40 minutes after the start of rewarming every 5 minutes. During rewarming of CPB, SjO2 was decreased to 43 +/- 7% in group 1 and to 44 +/- 4% in group 2. In groups 1 and 2, the maximum reduction of SjO2 occurred 17 minutes and 30 minutes after start of rewarming, respectively. The delayed reduction of SjO2 in group 2 correlated strongly with the prolonged increase in jugular bulb temperature. CONCLUSION The current data show that slow rewarming does not attenuate reductions of SjO2. This suggests that the reduction of SjO2 during rewarming of CPB is not a function of the rewarming speed but is strongly correlated with the increase in jugular bulb temperature, with a maximum effect just before reaching normothermia of the brain.

Perioperative and Postoperative Management

Developments in surgical as well as anesthetic management have meant that the morbidity and the mortality of esophageal surgery have substantially reduced during the last decade. Modern anesthetic management allows targeted risk stratification, especially of cardiac and pulmonary risk factors, thus providing a rationale for intraoperative monitoring and choice of anesthetic technique as well as postoperative pain and intensive care therapy. It is essential for the attending anesthesiologist to understand the underlying principles of the pathophysiology and surgery of esophageal diseases and to cooperate closely with the surgeon in order to provide the best care possible for the patient.

Physostigmine Prevents Postanesthetic Shivering as Does Meperidine or Clonidine

Background Postanesthetic shivering develops in as many as one half of patients recovering from isoflurane anesthesia. Cholinergic stimulation of the hypothalamic‐pituitary‐adrenal axis and adrenal medulla by physostigmine enhances secretion of arginine vasopressin, epinephrine, and norepinephrine. Because the hypothalamus is the dominant thermoregulatory controller in mammals, and these neurotransmitters may be involved in body temperature control, physostigmine administration may influence the incidence of shivering. Accordingly, the authors tested the hypothesis that physostigmine administration inhibits postanesthetic shivering. Its efficacy was compared with that of saline (negative control) and meperidine and clonidine (positive controls). Methods Sixty patients having surgery of the ear or nose were tested. General anesthesia was induced with 2 mg/kg propofol, 0.1 mg/kg vecuronium, and 1.5 micro gram/kg fentanyl and maintained with isoflurane (1.5 +/‐ 0.4%) in 70% nitrous oxide. At the end of surgery, the patients were randomly assigned to receive an intravenous bolus of 0.04 mg/kg physostigmine, isotonic saline, 0.5 mg/kg meperidine, or 1.5 micro gram/kg clonidine. Heart rate, mean arterial blood pressure, oxygen saturation, visual analog pain score, temperature, and postanesthetic shivering were measured during recovery. Results Postanesthetic shivering occurred in 6 of 15 (40%) patients given saline. In contrast, postanesthetic shivering was significantly reduced in physostigmine‐treated patients (1 of 15, or 7%) and was absent in patients given clonidine or meperidine. Conclusions Physostigmine inhibited shivering as well as did two established treatments, meperidine and clonidine. These data suggest that cholinergic systems contribute to the genesis and control of postanesthetic shivering.