Anesthesia and analgesia
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Anesthesia and analgesia · Apr 1999
Randomized Controlled Trial Comparative Study Clinical TrialThe epidural "top-up" in combined spinal-epidural anesthesia: the effect of volume versus dose.
The reinforcement of anesthesia by an epidural "top-up" in combined spinal-epidural anesthesia may be explained by a dual mechanism: a volume effect compressing the dural sac and a local anesthetic effect. The purpose of our study was to investigate the relative importance of each of these factors. Fifty patients scheduled for lower limb orthopedic surgery under combined spinal-epidural anesthesia were randomly allocated to one of five groups comprising 10 patients each. Using a needle-through-needle technique, all patients received a subarachnoid injection of 10 mg of plain bupivacaine and an epidural catheter. After the maximal level of sensory blockade as a result of the subarachnoid injection had been established, an epidural top-up was given according to the randomization code. Patients in Group 1 received 10 mL of bupivacaine 0.25%; patients in Group 2 received 10 mL of saline; patients in Group 3 received 5 mL of bupivacaine 0.5%; patients in Group 4 received 5 mL of saline; and patients in Group 5 received no epidural top-up. The maximal level of sensory blockade was then assessed for an additional 30 min. In Groups 1-4, the maximal level of sensory blockade increased significantly, whereas there was no significant increase in Group 5. There was no significant difference in the increase in the maximal level of sensory blockade among Groups 1-4. We conclude that, under the conditions of our study, there is no difference between 5 and 10 mL with regard to the volume effect of an epidural top-up in combined spinal-epidural anesthesia and that to produce an additional local anesthetic effect with bupivacaine, the dose must be larger than 25 mg. ⋯ In combined spinal-epidural anesthesia, an epidural "top-up" may increase the maximal level of sensory blockade by means of a volume effect and a local anesthetic effect. In this study, volumes of 5 and 10 mL produced a similar increase, and 25 mg of bupivacaine was insufficient to produce an additional local anesthetic effect.
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Anesthesia and analgesia · Apr 1999
Randomized Controlled Trial Comparative Study Clinical TrialHigh thoracic epidural anesthesia, but not clonidine, attenuates the perioperative stress response via sympatholysis and reduces the release of troponin T in patients undergoing coronary artery bypass grafting.
In this prospective study, we evaluated whether high thoracic epidural anesthesia (TEA) or i.v. clonidine, in addition to general anesthesia, affects the cardiopulmonary bypass- and surgery-associated stress response and incidence of myocardial ischemia by their sympatholytic properties. Seventy patients scheduled for elective coronary artery bypass graft (CABG) received general anesthesia with sufentanil and propofol. TEA was randomly induced before general anesthesia and continued during the study period in 25 (anesthetized dermatomes C6-T10). Another 24 patients received i.v. clonidine as a bolus of 4 microg/kg before the induction of general anesthesia. Clonidine was then infused at a rate of 1 microg x kg(-1) x h(-1) during surgery and at 0.2-0.5 microg x kg(-1) x h(-1) postoperatively. The remaining 21 patients underwent general anesthesia as performed routinely (control). Hemodynamics, plasma epinephrine and norepinephrine, cortisol, the myocardial-specific contractile protein troponin T, and other cardiac enzymes were measured pre- and postoperatively. During the preoperative night and a follow-up of 48 h after surgery, five-lead electrocardiogram monitoring was used for ischemia detection. Both TEA and clonidine reduced the postoperative heart rate compared with the control group without jeopardizing cardiac output or perfusion pressure. Plasma epinephrine increased perioperatively in all groups but was significantly lower in the TEA group. Neither TEA nor clonidine affected the increase in plasma cortisol. The release of troponin T was attenuated by TEA. New ST elevations > or = 0.2 mV or new ST depression > or = 0.1 mV occurred in > 70% of the control patients but only in 40% of the clonidine group and in 50% of the TEA group. We conclude that TEA (but not i.v. clonidine) combined with general anesthesia for CABG demonstrates a beneficial effect on the perioperative stress response and postoperative myocardial ischemia. ⋯ Thoracic epidural anesthesia combined with general anesthesia attenuates the myocardial sympathetic response to cardiopulmonary bypass and cardiac surgery. This is associated with decreased myocardial ischemia as determined by less release of troponin T. These findings may have an impact on the anesthetic management for coronary artery bypass grafting.
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Anesthesia and analgesia · Apr 1999
Randomized Controlled Trial Comparative Study Clinical TrialOnset time, recovery duration, and drug cost with four different methods of inducing general anesthesia.
We compared two conventional induction techniques (thiopental and propofol), an inhaled induction with sevoflurane using a circle system, and a rebreathing method. Fentanyl 1 microg/kg was given to women undergoing 10- to 20-min procedures. Anesthesia was induced (n = 20 each) with one of the following: 1) sevoflurane and N2O from a rebreathing bag (Sevo/Bag). A 5-L bag was prefilled with a mixture of sevoflurane 7% and N2O 60% in oxygen. The bag was connected between the normal circle system, separated by a spring-loaded valve; 2) sevoflurane 8% and N2O 60% from a circle system on a conventional anesthesia machine with a total fresh gas flow of 6 L/min (Sevo/Circle); 3) propofol 3 mg/kg as an i.v. bolus; 4) thiopental sodium 5 mg/kg as an i.v. bolus. Postoperative nausea and vomiting was treated with ondansetron. Induction times were comparable with each method. Recovery duration was shortest with sevoflurane, intermediate with propofol, and longest with thiopental. Induction drug costs were lowest with Sevo/Bag and thiopental, intermediate with Sevo/Circle, and highest with propofol. However, sevoflurane (by either method) caused considerable nausea and vomiting that required treatment. Consequently, total drug cost was least with thiopental, intermediate with Sevo/Bag and propofol, and greatest with Sevo/Circle. Thus, no single technique was clearly superior. ⋯ Anesthetic induction techniques influence awakening time, recovery duration, and drug costs. We tested two i.v. methods and two inhaled techniques. However, none of the four tested methods was clearly superior to the others.
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Anesthesia and analgesia · Apr 1999
Randomized Controlled Trial Clinical TrialOptimization of the dose of intrathecal morphine in total hip surgery: a dose-finding study.
We designed this study to determine the optimal intrathecal dose of morphine in total hip surgery. The optimal intrathecal dose was defined as that providing effective analgesia and minimal side effects 24 h after total hip surgery. Patients (n = 143) scheduled for total hip surgery were randomized to four double-blinded groups with a standardized bupivacaine dose but different doses of intrathecal morphine (Group I = 0.025 mg, Group II = 0.05 mg, Group III = 0.1 mg, and Group IV = 0.2 mg). Pain scores, i.v. morphine intake (patient-controlled analgesia), and morphine-related side effects (respiratory depression, postoperative nausea and vomiting, itching, urinary retention) were recorded for 24 h after surgery. Excellent postoperative pain relief was present in all groups. The highest pain scores were found in Group I. The mean use of systemic morphine administered by patient-controlled analgesia infusion pump was 23.7, 17.8, 10.9, and 9.9 mg in Groups I-IV, respectively (P < 0.01 for Groups III and IV versus Group I). We conclude that 0.1 mg of intrathecal morphine is the optimal dose for pain relief after hip surgery with minimal side effects. ⋯ Earlier studies showed excellent postoperative pain relief after intrathecal morphine. However, the severity of side effects resulted in decreased enthusiasm for this anesthesia technique. In the present study, we show that an intrathecal dose of 0.1 mg of morphine can be used safely in total hip surgery with excellent postoperative pain relief.
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Anesthesia and analgesia · Apr 1999
Randomized Controlled Trial Comparative Study Clinical TrialLess core hypothermia when anesthesia is induced with inhaled sevoflurane than with intravenous propofol.
Hypothermia after the induction of anesthesia results initially from core-to-peripheral redistribution of body heat. Sevoflurane and propofol both inhibit central thermoregulatory control, thus causing vasodilation. Propofol differs from sevoflurane in producing substantial peripheral vasodilation. This vasodilation is likely to facilitate core-to-peripheral redistribution of heat. Once heat is dissipated from the core, it cannot be recovered. We therefore tested the hypothesis that the induction of anesthesia with i.v. propofol causes more core hypothermia than induction with inhaled sevoflurane. We studied patients undergoing minor oral surgery randomly assigned to anesthetic induction with either 2.5 mg/kg propofol (n = 10) or inhalation of 5% sevoflurane (n = 10). Anesthesia in both groups was subsequently maintained with sevoflurane and 60% nitrous oxide in oxygen. Calf minus toe skin temperature gradients <0 degrees C were considered indicative of significant vasodilation. Ambient temperature and end-tidal concentrations of maintenance sevoflurane were comparable in each group. Patients in both groups were vasodilated throughout most of the surgery. Nonetheless, core temperatures in patients who received propofol were significantly lower than those in patients who received inhaled sevoflurane. These data support our hypothesis that even a brief period of vasodilation causes substantial redistribution hypothermia that persists throughout surgery. ⋯ Core temperatures in patients who received i.v. propofol were consistently lower than those in patients who received inhaled sevoflurane, although anesthesia was subsequently maintained with sevoflurane in nitrous oxide in both groups. This suggests that even a brief period of propofol-induced vasodilation during anesthetic induction causes substantial redistribution hypothermia that persists throughout surgery.