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 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 TrialA dose-response study of prophylactic intravenous ephedrine for the prevention of hypotension during spinal anesthesia for cesarean delivery.
We performed a randomized, double-blinded dose-finding study of IV ephedrine for prophylaxis for hypotension in 80 women who received an IV crystalloid preload and spinal anesthesia for elective cesarean delivery. One minute after the intrathecal injection, patients were given saline control or ephedrine 10, 20, or 30 mg IV for 30 s. Systolic arterial pressure (SAP) in the first 12 min after the spinal injection was greater in the 30-mg group compared with other groups (P < 0.05). Hypotension occurred in 7 patients (35%) in the 30-mg group compared with 19 (95%), 17 (85%), and 16 (80%) patients in the control and 10- and 20-mg groups, respectively (P < 0.0001). Maximum decrease in SAP was smaller in the 30-mg group (mean lowest SAP 87% of baseline, range 58%-105%) compared with other groups (P < 0.01). Reactive hypertension occurred in 9 patients (45%) in the 30-mg group (mean highest SAP 120% of baseline, range 104%-143%) compared with 2 (10%), 1 (5%), and 5 (25%) patients in the other groups (P = 0.009). Heart rate changes, total ephedrine requirement, incidence of nausea and vomiting, and neonatal outcome were similar among groups. The proportion of patients with umbilical arterial pH < 7.2 was 10.5%, 25%, 42%, and 22% in the control, 10-, 20-, and 30-mg groups, respectively (P = 0. 12). We conclude that the smallest effective dose of ephedrine to reduce the incidence of hypotension was 30 mg. However, this dose did not completely eliminate hypotension, nausea and vomiting, and fetal acidosis, and it caused reactive hypertension in some patients. ⋯ We investigated different doses of IV ephedrine as prophylaxis for hypotension during spinal anesthesia for cesarean delivery and found that the smallest effective dose was 30 mg. However, this dose did not completely eliminate hypotension, caused reactive hypertension in some patients, and did not improve neonatal outcome.
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Anesthesia and analgesia · Jun 2000
Clinical TrialFalse alarms and sensitivity of conventional pulse oximetry versus the Masimo SET technology in the pediatric postanesthesia care unit.
We compared the incidence and duration of false alarms (FA)and the sensitivity of conventional pulse oximetry (CPO) with Masimo Signal Extraction Technology (Masimo SET; Masimo Corporation, Irvine, CA) in children in the postanesthesia care unit. Disposable oximeter sensors were placed on separate digits of one extremity. Computerized acquisition of synchronous data included electrocardiograph heart rate, SpO(2), and pulse rate via CPO and Masimo SET. Patient motion, respiratory, and other events were simultaneously documented. SpO(2) tracings conflicting with clinical observations and/or documented events were considered false. These were defined as 1) Data dropout, complete interruption in SpO(2) data; 2) False negative, failure to detect SpO(2)
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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.