Anesthesia and analgesia
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Anesthesia and analgesia · Jun 2000
Randomized Controlled Trial Clinical TrialOndansetron given before induction of anesthesia reduces shivering after general anesthesia.
The neurotransmitter pathways involved in the mechanism of postanesthetic shivering (PAS) are poorly understood. Meperidine, clonidine, and physostigmine are all effective treatments, indicating that opioid, alpha(2)-adrenergic, and anticholinergic systems are probably involved. We investigated the effect of ondansetron, a 5-HT(3) antagonist used to treat postoperative nausea and vomiting, on intraoperative core and peripheral temperatures and PAS. Eighty-two patients (age, 18-60 yr) undergoing orthopedic, general, or urological surgery were randomized into three groups in this double-blinded, placebo-controlled, study: Group O4 (n = 27) received ondansetron 4 mg IV, Group O8 (n = 27) received ondansetron 8 mg IV, and Group C (n = 28) received saline IV immediately before the anesthetic induction. Core (tympanic) and fingertip temperature (dorsum of middle finger) were recorded. Anesthesia was induced with IV fentanyl 1 microg/kg and propofol 2.0-2.5 mg/kg and maintained with 1 minimum alveolar anesthetic concentration isoflurane in 70% nitrous oxide/oxygen. The occurrence of shivering was documented clinically during recovery by nursing staff, who were unaware of the group assignment. PAS occurred in 16 of 28 (57%) patients in Group C, compared with 9 of 27 (33%) in Group O4 (P = 0.13) and 4 of 27 (15%) patients in Group O8 (P = 0.003). Within each group, core temperature decreased and peripheral temperature increased significantly, but there were no significant differences among the groups at any time interval. We conclude that ondansetron 8 mg IV given during the induction of anesthesia prevents PAS without affecting the core-to-peripheral redistribution of heat during general anesthesia. This suggests that serotonergic pathways have a role in the regulation of PAS. ⋯ In a randomized, double-blinded, placebo-controlled, clinical study, ondansetron 8 mg IV, given just before the induction, reduced the incidence of postanesthetic shivering compared with saline. The anticipated core-to-peripheral redistribution of body temperature during general anesthesia was not affected. This implies that ondansetron probably acts by a central inhibitory mechanism, and that 5-hydroxytryptaminergic pathways have a role in regulating postanesthetic shivering.
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Anesthesia and analgesia · Jun 2000
Randomized Controlled Trial Clinical TrialLumbar sympathetic block for sympathetically maintained pain: changes in cutaneous temperatures and pain perception.
Lumbar sympathetic block (LSB) is used in the management of sympathetically maintained pain states. We characterized cutaneous temperature changes over the lower extremities after LSB. Additionally, we examined the effects of iohexol, a radio-opaque contrast medium, on temperature changes and pain relief. After institutional review board approval and written, informed consent, 28 LSBs were studied in 17 patients. Iohexol or normal saline was injected in a randomized, double-blinded fashion before bupivacaine. Lower extremity cutaneous temperatures were measured. Pain, allodynia, interference with daily function, and perceived pain relief were reported in a subset of 15 LSBs for 1 wk after the block. The distal lower extremity ipsilateral to the LSB had the greatest magnitude (8.7 degrees +/- 0.8 degrees C) and rate (1.1 degrees +/- 0.2 degrees C/min) of temperature change. The great toe temperature was within 3 degrees C of core temperature within 35 min after LSB. There were no differences in temperature change between the groups. The iohexol group had greater relief of pain until the morning of the first postblock day (P = 0.002) and longer perceived relief of pain (P = 0.01). The maximum temperature of the great toe correlated with allodynia relief (P = 0.0007). Thus clinicians should expect ipsilateral toe temperatures to increase to within approximately 3 degrees C of core temperature. Iohexol does not alter the efficacy of LSB and may improve relief of symptoms. The magnitude of temperature change may predict relief of allodynia. ⋯ Cutaneous toe temperatures approaching core temperature provide a useful monitor of lumbar sympathetic block and may predict relief of sympathetically maintained pain. Iohexol will not compromise temperature changes or pain relief.
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Anesthesia and analgesia · Jun 2000
Randomized Controlled Trial Comparative Study Clinical TrialAmbulatory labor epidural analgesia: bupivacaine versus ropivacaine.
Dilute concentrations of bupivacaine combined with fentanyl have recently been used to initiate labor epidural analgesia in an attempt to balance adequate analgesia and minimal maternal motor blockade. Similar concentrations of ropivacaine have not been evaluated. This prospective, randomized, double-blinded study was designed to compare the efficacy of 20 mL of either 0.08% bupivacaine plus 2 microg/mL fentanyl or 0.08% ropivacaine plus 2 microg/mL fentanyl to initiate ambulatory labor epidural analgesia. Forty nulliparous women in early ( 0 but < 20 at 20 min. The time (mean +/- SD) to visual analog scale score = 0 was BF (n = 18): 12.0 +/- 4.5 min and RF (n = 19): 12.4 +/- 4.0 min (P > 0.05). Spontaneous micturition was observed in 65% (13 of 20) BF compared with 100% (20 of 20) RF (P < 0.01), and ambulation was demonstrated in 75% (15 of 20) BF compared with 100% (20 of 20) RF (P < 0.03). The incidence of forceps delivery was 35% (7 of 20) BF compared with 10% (2 of 20) RF (P < 0.04). The results of this study indicate that dilute ropivacaine combined with fentanyl effectively initiates epidural analgesia while concurrently preserving maternal ability to void and ambulate. ⋯ As compared with a similar dilute concentration of bupivacaine, 20 mL of dilute (0.08%) ropivacaine combined with fentanyl (2 microg/mL) effectively initiates epidural analgesia in nulliparous women in early, established labor while preserving their ability to micturate and ambulate. Of importance, it appears that a true ambulatory epidural analgesic for women in labor is now possible.
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Anesthesia and analgesia · Jun 2000
Randomized Controlled Trial Clinical TrialThe effects of plasma fentanyl concentrations on propofol requirement, emergence from anesthesia, and postoperative analgesia in propofol-nitrous oxide anesthesia.
To determine the effects of plasma fentanyl concentrations on intraoperative propofol requirements, emergence from anesthesia, and relief of postoperative pain, we studied 60 ASA physical status I and II patients undergoing spine fusion. The patients were randomly assigned to four study groups according to the expected intraoperative plasma fentanyl concentrations. Group I received an infusion of saline, and Groups II, III, and IV received fentanyl infusions to maintain the blood levels at 1.5, 3.0, and 4.5 ng/mL, respectively. An infusion rate of propofol was adjusted to keep the mean arterial pressure within 15% of the control value. Inspired nitrous oxide concentrations were maintained at 67%. The following were investigated in each group: 1) an average propofol infusion rate, 2) time to spontaneous eye opening and recovery of orientation (name, date, and place), and 3) total dose of fentanyl used for 24 h after admission to the postanesthetic care unit. Average propofol infusion rates were 10.1 +/- 2.5 (mean +/- SD), 7.5 +/- 1.2, 5.7 +/- 1.1, and 4.9 +/- 1.2 mg. kg(-1). h(-1), in Groups I, II, III, and IV, respectively. Groups receiving fentanyl infusion had significantly smaller infusion rates of propofol (P < 0.01) than the group receiving saline. Among the three fentanyl infusion groups, Group II (P < 0.01) had more than Groups III and IV. The time to spontaneous eye opening and the recovery of orientation were directly related to plasma fentanyl concentrations. The plasma fentanyl levels between Groups III and IV were the same. The total amount of IV patient-controlled analgesia fentanyl during postoperative 24 h increased significantly when the order of plasma fentanyl concentrations was reversed, 913.1 +/- 58.4, 553.4 +/- 129, 222.7 +/- 73.4, and 135.1 +/- 69.5 microg in Groups I, II, III, and IV, respectively. These results suggest that the addition of fentanyl infusions had ceiling effects that reduce the intraoperative propofol requirements according to the plasma fentanyl concentrations. The ceiling effect was demonstrated in the recovery of consciousness but not in the fentanyl requirements for postoperative analgesia. ⋯ The addition of fentanyl, a potent opioid, reduced the intraoperative requirement of propofol, an IV anesthetic, in the order of the plasma fentanyl concentrations. The ceiling effects of fentanyl were demonstrated in the reduction of propofol requirements and recovery of consciousness but not in the fentanyl requirements for postoperative analgesia.
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Anesthesia and analgesia · Jun 2000
Comparative Study Clinical TrialRapid evaluation of coagulopathies after cardiopulmonary bypass in children using modified thromboelastography.
Complex coagulopathies follow cardiopulmonary bypass (CPB) in children. However, objective laboratory data that can be acquired rapidly to guide their management are lacking. Because thromboelastography has proven useful in this regard, we evaluated the use of celite or tissue factor (TF) activation and heparinase modification of blood samples to allow rapid determination of thromboelastogram data in children younger than 2 yr undergoing CPB. Celite or TF activation shortened the initiation of clotting and, thus, the time required for the important thromboelastogram alpha and maximum amplitude values to begin evolving. Although thromboelastogram alpha and maximum amplitude values were increased with these activators, correlations persisted between platelet count or fibrinogen level and each of these values. The additional use of heparinase allowed thromboelastograms to be obtained during CPB with values not different from those obtained without heparinase after protamine administration. Therefore, celite- or TF-activated, heparinase-modified thromboelastograms begun during CPB allow objective data to be available by the conclusion of protamine administration to help restore hemostasis after CPB in children. Thromboelastography identified transient fibrinolysis during CPB in some children that resolved by the conclusion of protamine administration. Future investigations of the effectiveness of modified thromboelastography-guided coagulopathy management after CPB in children are needed. ⋯ Thromboelastography is useful in assessing the coagulopathies that follow cardiopulmonary bypass in children. Modifying blood samples with celite or tissue factor and heparinase allows thromboelastography begun before the termination of cardiopulmonary bypass to become a rapid point-of-care monitor to provide objective data for guiding blood component therapy to manage these coagulopathies.