Decreased mivacurium requirements and delayed neuromuscular recovery during sevoflurane anesthesia in children and adults.

UNLABELLED: The purpose of this study was to compare the mivacurium infusion requirements and neuromuscular recovery in adults and children during propofol/opioid and sevoflurane anesthesia. Seventy-five adult and 75 pediatric patients were randomized to receive propofol/opioid 0.5 or 1.0 minimum alveolar anesthetic concentration (MAC) (age-related) sevoflurane anesthesia. Plasma cholinesterase (PChE) activity was measured. Neuromuscular blockade was monitored by train-of-four (TOF) stimulation every 10 s and adductor pollicis electromyography. A bolus of 2 x the 95% effective dose of mivacurium (0.25 mg/kg) was followed by an infusion titrated to maintain 90%-95% blockade. Mivacurium doses were recorded every 5 min. At the end of surgery, the infusion was stopped, and recovery from mivacurium was monitored until TOF > or =0.7. PChE concentrations were within the normal range (adults 4-12 KU/L, children 6-16 KU/L) and correlated with mivacurium dose. Mivacurium infusion rates were higher in children than in adults: at 30 min, the rates in children were 13.1 +/- 6.4, 8.1 +/- 4.7, and 5.2 +/- 2.9 microg x kg(-1) x min(-1) at 0, 0.5, and 1.0 MAC sevoflurane, respectively; the corresponding rates in adults were 5.9 +/- 3.1, 4.3 +/- 1.7, and 2.9 +/- 0.7 microg x kg(-1) x min(-1) (P < 0.01). Sevoflurane decreased mivacurium requirements, maximal decreases at 45 min in children and 10 min in adults, and delayed neuromuscular function recovery. Children recovered twice as quickly as adults, achieving TOF > or =0.7 at 9.8 +/- 2.5, 11.4 +/- 2.8, and 19.6 +/- 6.3 min compared with 19.9 +/- 5.4, 26.4 +/- 8.3, and 32.9 +/- 9.8 min in adults (P < 0.0001). In conclusion, mivacurium requirements were correlated with PChE, were greater in children than in adults, and were reduced by sevoflurane. Neuromuscular recovery occurred more rapidly in children and was delayed by sevoflurane. IMPLICATIONS: The mivacurium infusion requirement to maintain constant 90%-95% neuromuscular block during anesthesia is correlated with plasma cholinesterase activity. It is increased in children and reduced by the inhaled anesthetic sevoflurane. Despite the larger dose administered to children, recovery from block occurred more rapidly in children than in adults and was delayed by sevoflurane.

The effectiveness of clonidine as an analgesic in paediatric adenotonsillectomy.

PURPOSE: To compare the analgesic effects of preoperative oral clonidine with intraoperative intravenous fentanyl in children undergoing tonsillectomy or adenotonsillectomy. METHODS: This randomized, controlled, double-blind study of 36 ASA I-II children, age 7-12 yr undergoing adenotonsillectomy was conducted at a tertiary care paediatric teaching hospital. Either 4 micrograms.kg-1 clonidine po was given 60-90 min preoperatively or 3 micrograms.kg-1 fentanyl i.v. was given intraoperatively. Postoperatively visual analog pain scores (VAS) were recorded at rest and on swallowing every 10 min for the first 30 min and then every 15 min for two hours. Morphine 0.05 mg.kg-1 i.v. was given for VAS > or = 5. If > 3 doses were required, 1.5 mg.kg-1 codeine po and 20 mg.kg-1 acetaminophen po were given. Sedation and anxiety scores were recorded preoperatively. Haemodynamic changes, blood loss, recovery scores, and the incidence of vomiting, hypotension, and airway obstruction were recorded. RESULTS: Children who received clonidine had a higher incidence of preoperative sedation (63%) than those receiving fentanyl (6%). Preinduction mean arterial pressure was lower in the clonidine group but required no intervention. VAS scores were similar throughout the observation period. There was no difference either in the number of morphine or codeine rescue doses administered or in the incidence of side effects. CONCLUSION: Oral clonidine is an effective analgesic and sedative for children undergoing tonsillectomy or adenotonsillectomy.

Reversal of doxacurium and pancuronium neuromuscular blockade with neostigmine in children.

Recovery after doxacurium and pancuronium neuromuscular blockade and their acceleration by neostigmine have not been compared in children. Therefore, 60 paediatric surgical patients aged 2-10 yr (ASA 1-2) were studied. They were randomized to receive doxacurium 30 micrograms.kg-1 or pancuronium 70 micrograms.kg-1 iv during propofol, fentanyl, isoflurane and nitrous oxide anaesthesia. Electromyographic (EMG) responses of the adductor pollicis to train-of-four (TOF) stimulation of the ulnar nerve were recorded every ten seconds using a Datex NMT monitor. Six patients in each relaxant group received neostigmine (0, 5, 10, 20 or 40 micrograms.kg-1) with atropine by random allocation when first twitch height (T1) had recovered to 25% of control. Spontaneous recovery after ten minutes was similar following doxacurium (mean +/- SEM values of 45.0 +/- 3.9 vs 49.5 +/- 10.0% for T1 and 25.2 +/- 3.8 vs 14.8 +/- 3.6% for TOF ratios). Dose-responses to neostigmine were calculated from the log dose vs logit of T1 or TOF ratio after ten minutes. Neostigmine-assisted recovery was not different in the two groups, with ED70 and ED90 doses for T1 of 14.3 +/- 1.8 and 25.7 +/- 2.7 micrograms.kg-1 for doxacurium and 12.5 +/- 1.7 and 25.3 +/- 2.3 micrograms.kg-1 for pancuronium. Time to recovery of TOF ratio to 70% after neostigmine 40 micrograms.kg-1 was 2.3 +/- 1.0 and 4.2 +/- 1.7 min (P = NS) following pancuronium and doxacurium, respectively. Adjusted recovery due to neostigmine alone (spontaneous recovery subtracted from the total) required two to three times higher doses of neostigmine.(ABSTRACT TRUNCATED AT 250 WORDS)

Propofol anaesthesia reduces early postoperative emesis after paediatric strabismus surgery.

Propofol anaesthesia may reduce postoperative emesis. The purpose of this study was to compare the incidence of emesis after propofol anaesthesia with and without nitrous oxide, compared with thiopentone and halothane anaesthesia, in hospital and up to 24 hr postoperatively, in outpatient paediatric patients after strabismus surgery. Seventy-five ASA class I or II, unpremedicated patients, aged 2-12 yr were randomly assigned to one of three groups: Thiopentone, 6.0 mg.kg-1 i.v. induction followed by halothane and N2O/O2 for maintenance (T/H); propofol for induction, followed by propofol and oxygen for maintenance (P/O2); and propofol for i.v. induction, followed by propofol infusion and N2O/O2 for maintenance (P/N2O). All received vecuronium, controlled ventilation, and acetaminophen pr. Morphine was given as needed for postoperative analgesia. There were no differences in age, weight, number of eye muscles operated upon, duration of anaesthesia or surgery. The P/N2O group (255 +/- 80 micrograms.kg-1 x min-1) received less propofol than the P/O2 group (344 +/- 60 micrograms.kg-1 x min-1) (P < or = 0.0001) and had shorter extubation (P < 0.001) and recovery (P < 0.01) times. Emesis in the hospital, in both the P/N2O (4.0%) and P/O2 group (4.0%) was less than in the T/H group (32%) (P < 0.01). Antiemetics were required in four patients in the T/H group (16.0%). Overall emesis after surgery was not different among the groups: T/H (48%), P/O2 (28%) and P/N2O (42%). The use of propofol anaesthesia with and without N2O decreased only early emesis. This supports the concept of a short-acting, specific antiemetic effect of propofol.

Low-dose bupivacaine does not improve postoperative epidural fentanyl analgesia in orthopedic patients.

Epidural infusions of 10 micrograms/mL fentanyl combined with low-dose bupivacaine (0.1%) were compared with epidural infusions of fentanyl alone for postoperative analgesia after total knee joint replacement. There were no detectable differences between the two groups in analgesia (visual analogue scale ranging between 15 and 40 mm), infusion rates (which averaged 7-9 mL/h), or serum fentanyl levels (which reached 1-2 ng/mL). The incidence of side effects, including nausea, vomiting, and pruritus, was also similar. Of the patients receiving fentanyl and low-dose bupivacaine, one developed a transient unilateral motor and sensory loss, and one developed significant hypotension and respiratory depression. The addition of low-dose bupivacaine does not improve epidural fentanyl infusion analgesia after knee surgery and may increase morbidity.