Anesthesia and analgesia
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Anesthesia and analgesia · Apr 1999
Randomized Controlled Trial Comparative Study Clinical TrialA comparison of epidural ropivacaine infusion alone and in combination with 1, 2, and 4 microg/mL fentanyl for seventy-two hours of postoperative analgesia after major abdominal surgery.
Our aim in this prospective, randomized, double-blinded study was to compare the analgesic effectiveness and side effects of epidural infusions with ropivacaine 2 mg/mL alone (Group R; n = 60) and in combination with fentanyl 1 microg/mL (R1F; n = 59), 2 microg/mL (R2F; n = 62), and 4 microg/mL (R4F; n = 63) for up to 72 h after major abdominal surgery. Effective epidural neural blockade was established before surgery; postoperatively, the infusion rate was titrated to a maximum of 14 mL/h for analgesia. No additional analgesics other than acetaminophen were permitted during the infusion. The median of individual visual analog scale score with coughing were <20 mm for all groups (0 = no pain, 100 = worst pain) and was significantly lower (P < 0.01) for Group R4F at rest and with coughing (compared with Group R). Infusions were discontinued due to inability to control pain in significantly fewer patients in Group R4F (16%) than the other groups (34% to 39%; P < 0.01). For all groups, >90% of patients had no detectable motor block after 24 h. Hypotension, nausea, and pruritus were more common with the larger dose of fentanyl. We conclude that, after major abdominal surgery, an epidural infusion of ropivacaine 2 mg/mL with fentanyl 4 microg/mL provided significantly more effective pain relief over a 3-day period than ropivacaine alone or ropivacaine with lower concentrations of fentanyl. ⋯ Postoperative epidural analgesic infusions are widely used, but there is little information regarding optimal strengths of opioid with local anesthetic. In this blinded, prospective study, we compared four different epidural infusion solutions for efficacy and side effects over a clinically useful postoperative period and conclude that an epidural infusion of ropivacaine 2 mg/mL with fentanyl 4 microg/mL was most effective.
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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.
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Anesthesia and analgesia · Apr 1999
Randomized Controlled Trial Clinical TrialPreoperative oral dextromethorphan does not reduce pain or analgesic consumption in children after adenotonsillectomy.
In this randomized, double-blinded, placebo-controlled, prospective study, we evaluated the analgesic efficacy of dextromethorphan 0.5 mg/kg or 1.0 mg/kg p.o. 1 h before adenotonsillectomy in 57 children 6-12 yr of age. Anesthetic management was standardized. Morphine 0.075 mg/kg i.v. and acetaminophen 25-35 mg/kg p.r. were administered after anesthetic induction but before the start of surgery. A 4-point behavioral score (1 = asleep, 2 = awake and calm, 3 = awake and crying, 4 = thrashing) was recorded on admission to and discharge from the postanesthesia care unit (PACU). In the PACU, pain was assessed with Children's Hospital of Eastern Ontario Pain Scale (CHEOPS) and recorded every 15 min until the patient was transferred to the day surgery unit (DSU). In the DSU, patients rated their pain using a 10-cm baseline 0-10 visual analog pain scale (VAS) every 30 min until they were discharged home. A 24-h VAS was obtained by phone interview, and parental satisfaction was scored (yes/no) regarding their child's postoperative analgesia. Morphine 0.025 mg/kg i.v. was administered to children with CHEOPS score >6, who verbalized pain, or who were crying in any consecutive 5-min observation periods in the PACU. Total morphine consumption was recorded. The study groups were comparable with respect to demographic variables. We were unable to detect any differences between study groups with respect to postoperative morphine consumption, CHEOPS, behavior scores, VAS, or parental satisfaction. ⋯ Premedication with dextromethorphan 0.5 or 1.0 mg/kg p.o. does not improve postoperative analgesia in school-aged children who receive preemptive morphine 0.075 mg/kg i.v. and acetaminophen 25-35 mg/kg p.r. during nitrous oxide and desflurane anesthesia for adenotonsillectomy.
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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 TrialThe target plasma concentration of propofol required to place laryngeal mask versus cuffed oropharyngeal airway.
To determine the target plasma concentration of propofol required to place either a laryngeal mask airway (LMA) or a cuffed oropharyngeal airway (COPA), we started a continuous target-controlled infusion of propofol in 60 ASA physical status I or II unpremedicated patients scheduled for minor orthopedic surgery with peripheral nerve block. The target plasma concentration of propofol was initially set at 2 microg/mL. When the effect-site calculated concentration of propofol was equal to the plasma concentration according to the computer simulation, the target plasma concentration was increased by 0.5-microg/mL steps until successful placement of either the LMA (n = 30) or the COPA (n = 30). The mean target plasma concentration of propofol required to place a LMA was 4.3 +/- 0.8 microg/mL compared with 3.2 +/- 0.6 microg/mL to place a COPA (P < 0.001). To successfully place the airways in 95% of patients, the target plasma concentration of propofol had to be increased up to 4 microg/mL for the COPA and 6 microg/mL for the LMA. We conclude that placing a LMA in healthy, unpremedicated patients requires target plasma concentrations of propofol higher than those required for placing a COPA. ⋯ We evaluated the use of target-controlled infusion of propofol to place extratracheal airways in this prospective, randomized study and demonstrated that the target plasma concentration of propofol required to successfully place a laryngeal mask in >95% of healthy, unpremedicated patients is 6 microg/mL, compared with 4 microg/mL to place a cuffed oropharyngeal airway.