Anesthesia and analgesia
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Anesthesia and analgesia · Feb 1999
Randomized Controlled Trial Comparative Study Clinical TrialSomatosensory evoked potential monitoring used to compare the effect of three asymmetric sternal retractors on brachial plexus function.
We compared the effect of three different asymmetric sternal retractors on brachial plexus dysfunction using intraoperative somatosensory evoked potentials (SSEPs). We studied 60 patients undergoing coronary bypass and internal mammary harvest. Assessment of brachial plexus function was performed pre- and postoperatively. Patients were assigned the use of a Pittman (MN Scientific Instruments Inc., Minneapolis, MN), Rultract (Rultract Inc., Cleveland, OH), or Delacroix-Chevalier (Delacroix-Chevalier, Paris, France) asymmetric sternal retractor for internal mammary exposure. SSEP changes from baseline during asymmetric retractor use and removal were determined, and average changes were compared among the retractor groups. Patient demographics and baseline SSEP values were similar. Fewer patients in the Delacroix-Chevalier group had decreases in SSEP amplitudes after retractor placement. Of the patients in the Rultract and Pittman groups, 45% and 25%, respectively, had amplitude decreases of >50%, compared with only 5% of the Delacroix-Chevalier patients. Three patients in both the Pittman and Rultract groups and one patient in the Delacroix-Chevalier group suffered brachial plexus symptoms postoperatively. We conclude that the Delacroix-Chevalier retractor is associated with less neurophysiologic evidence of brachial plexus dysfunction during asymmetric sternal retraction compared with either the Pittman or Rultract sternal retractors. ⋯ We used somatosensory evoked potentials to assess the effect of several different asymmetric sternal retractors on brachial plexus dysfunction and to determine which produced the least evidence of nerve damage during surgical exposure of the internal mammary artery.
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Anesthesia and analgesia · Feb 1999
Randomized Controlled Trial Comparative Study Clinical TrialThe effects of prostaglandin E1 on intraoperative temperature changes and the incidence of postoperative shivering during deliberate mild hypothermia for neurosurgical procedures.
We investigated the effects of i.v. prostaglandin E1 (PGE1) on intraoperative changes of core temperature and the incidence of postoperative shivering in neurosurgical patients undergoing deliberate mild hypothermia. Eighty-three patients were randomly assigned to one of three groups: patients in the control group did not receive PGE1, whereas patients in the PG20 group and PG50 group received PGE1 at a dose of 0.02 and 0.05 microg x kg(-1) x min(-1), respectively. The administration of PGE1 was started just after the induction of anesthesia and continued until the end of anesthesia. Anesthesia was maintained with nitrous oxide in oxygen, sevoflurane, and fentanyl. After the induction of anesthesia, patients were cooled using a water blanket and a convective device blanket. Tympanic membrane temperature was maintained at 34.5 degrees C. During surgical wound closure, patients were rewarmed. Intraoperative changes in tympanic membrane and skin temperatures and the incidence of postoperative shivering were compared among groups. Demographic and intraoperative variables were similar among groups. There were no significant differences in tympanic temperatures among groups at each point during the operation. Skin temperature 30 min after rewarming and just after tracheal extubation was significantly lower in the PG20 group than in the PG50 group. Postoperative shivering was more frequent in the PG20 group (43%) than in the control (13%) and PG50 (17%) groups. These results suggest that the intraoperative administration of PGE1 does not affect changes in core temperature during deliberate mild hypothermia and that PGE1 at a dose of 0.02 microg x kg(-1) x min(-1) may increase the occurrence of postoperative shivering. ⋯ Deliberate mild hypothermia has been proposed as a means of providing cerebral protection during neurosurgical procedures. Vasodilating drugs may be used during deliberate mild hypothermia to maintain peripheral circulation and to enhance the cooling and rewarming rate. In the present study, however, we found no benefit from i.v. prostaglandin E1 administration during deliberate mild hypothermia in neurosurgical patients.
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Anesthesia and analgesia · Feb 1999
Comparative StudyAn examination of the interactions between the antinociceptive effects of morphine and various mu-opioids: the role of intrinsic efficacy and stimulus intensity.
We examined the effects of several opioids that vary in intrinsic efficacy at the mu-opioid receptor alone and in combination with morphine in a rat warm water tail withdrawal procedure using 50 degrees C and 52 degrees C water (i.e., low- and high-stimulus intensities). Morphine, levorphanol, dezocine, and buprenorphine produced dose-dependent increases in antinociception using both stimulus intensities. Butorphanol produced maximal levels of antinociception at the low, but not at the high, stimulus intensity, whereas nalbuphine failed to produce antinociception at either stimulus intensity. For cases in which butorphanol and nalbuphine failed to produce antinociception alone, these opioids dose-dependently antagonized the effects of morphine. When levorphanol, dezocine, and buprenorphine were combined with morphine, there was a dose-dependent enhancement of morphine's effects. Similar effects were obtained at the low-stimulus intensity when butorphanol was administered with morphine. In most cases, the effects of these combinations could be predicted by summating the effects of the drugs when administered alone. These results indicate that the level of antinociception produced by an opioid is dependent on the intrinsic efficacy of the drug and the stimulus intensity. Furthermore, the level of antinociception produced by the opioid, not necessarily the opioids' intrinsic efficacy, determines the type of interaction among opioids. ⋯ Compared with high-efficacy opioids, lower efficacy opioids produce lower levels of pain relief, especially in situations of moderate to severe pain. When opioids are given in combination, the effects can only be predicted on the basis of the antinociception obtained when the drugs are administered alone.
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Anesthesia and analgesia · Feb 1999
Comparative StudyChanges in maternal middle cerebral artery blood flow velocity associated with general anesthesia in severe preeclampsia.
In women with severe preeclampsia, significant increases in mean arterial pressures (MAP) are common after rapid induction of general anesthesia (GA) and tracheal intubation. The objectives of this prospective study were to assess the effects of the rapid induction-intubation technique on middle cerebral artery (MCA) flow velocity in severe preeclampsia and to examine the correlation between mean MCA flow velocity (Vm) and MAP. Eight women with severe preeclampsia (study group) and six normotensive women at term (control group) scheduled to undergo cesarean section under GA were studied. Before induction, patients in the study group received i.v. labetalol in divided doses to lower diastolic pressures to <100 mm Hg. Anesthesia was induced with pentothal 4-5 mg/kg, followed by succinylcholine 1.5 mg/kg to facilitate tracheal intubation. A transcranial Doppler was used to measure Vm. Both Vm and MAP were recorded before induction and every minute for 6 min after intubation. In the study group, after the administration of labetalol, MAP decreased from 129 +/- 9 to 113 +/- 9 mm Hg (P < 0.05), and Vm decreased from 59 +/- 11 to 54 +/- 10 cm/s (P < 0.05). After intubation, MAP increased from 113 +/- 9 to 134 +/- 5 mm Hg (P < 0.001), and Vm increased from 54 +/- 10 to 70 +/- 10 cm/s (P < 0.001). In the control group, while MAP increased significantly from 89 +/- 6 to 96 +/- 4 mm Hg (P < 0.05) after intubation, the concurrent increase in Vm from 49 +/- 5 to 54 +/- 7 cm/s was not significant. There was a significant positive pooled correlation between Vm and MAP (r = 0.5, P < 0.0006) in the study group but not in the control group (r = 0.24). After induction and intubation, both Vm and MAP values were significantly increased in the study group patients at all observation points compared with the control group patients. The findings indicate that Vm increases significantly after rapid-sequence induction of GA and tracheal intubation in women with severe preeclampsia, and there seems to be a direct relationship between MAP and Vm. ⋯ In women with severe preeclampsia, rapid-sequence induction of general anesthesia and tracheal intubation can cause severe hypertension. Our results indicate that the increase in blood pressure is associated with a significant increase in maternal cerebral blood flow velocity and that there is a significant correlation between these two variables.
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Anesthesia and analgesia · Feb 1999
Drug therapy before coronary artery surgery: nitrates are independent predictors of mortality and beta-adrenergic blockers predict survival.
We conducted this study to evaluate whether there is an association between preoperative drug therapy and in-hospital mortality in patients undergoing coronary artery graft surgery. We collected data on 1593 consecutive patients undergoing coronary artery surgery. The relative risk of in-hospital mortality was determined by logistic regression with in-hospital mortality as the dependent variable, and independent variables that included known risk factors and preoperative cardioactive or antithrombotic drug treatment, i.e., age; left ventricular function; left main coronary artery disease; urgent priority; gender; previous cardiac surgery; concurrent cardiovascular surgery; chronic lung disease; creatinine concentration; hemoglobin concentration; diabetes; hypertension; cerebrovascular disease; recent myocardial infarction; prior vascular surgery; number of arteries bypassed; and regular daily treatment with beta-blockers, aspirin within 5 days, calcium antagonists, angiotensin converting enzyme (ACE) inhibitors, digoxin, or warfarin. In-hospital mortality was 3.3%. The relative risk of in-hospital mortality (with 95% confidence intervals of the relative risk) associated with the following drug treatments was: nitrates 3.8 (1.5-9.6), beta-blockers 0.4 (0.2-0.8), aspirin within 5 days 1.0 (0.5-1.9), calcium antagonists 1.1 (0.6-2.1), ACE inhibitors 0.8 (0.4-1.5), digoxin 0.7 (0.2-1.8), and warfarin 0.3 (0.1-1.6). We conclude that in-hospital mortality is positively associated with preoperative nitrate therapy and negatively associated with beta-adrenergic blocker therapy. A significant association between in-hospital mortality and the preoperative use of calcium antagonists, ACE inhibitors, aspirin, digoxin, and warfarin was not confirmed. ⋯ We examined the association between common drug treatments for ischemic heart disease and short-term survival after cardiac surgery using a statistical method to adjust for patients' preoperative medical condition. Death after surgery was more likely after nitrate therapy and less likely after beta-blocker therapy.