Rosemary J. Orr

Induction, recovery, and safety characteristics of sevoflurane in children undergoing ambulatory surgery. A comparison with halothane.

Background Sevoflurane is an inhalational anesthetic with characteristics suited for use in children. To determine whether the induction, recovery, and safety characteristics of sevoflurane differ from those of halothane, the following open‐labeled, multicenter, randomized, controlled, phase III study in children undergoing ambulatory surgery was designed. Methods Three hundred seventy‐five children, ASA physical status 1 or 2, were randomly assigned in a 2:1 ratio to receive either sevoflurane or halothane, both in 60% N2 O and 40% O2. Anesthesia was induced using a mask with an Ayres t piece or Bain circuit in four of the centers and a mask with a circle circuit in the fifth center. Maximum inspired concentrations during induction of anesthesia were 7% sevoflurane and 4.3% halothane. Anesthesia was maintained by spontaneous ventilation, without tracheal intubation. End‐tidal concentrations of both inhalational anesthetics were adjusted to 1.0 MAC for at least 10 min before the end of surgery. Induction and recovery characteristics and all side effects were recorded. The plasma concentration of inorganic fluoride was measured at induction of and 1 h after anesthesia. Results During induction of anesthesia, the time to loss of the eyelash reflex with sevoflurane was 0.3 min faster than with halothane (P < 0.001). The incidence of airway reflex responses was similar, albeit infrequent with both anesthetics. The total MAC *symbol* h exposure to sevoflurane was 11% less than the exposure to halothane (P < 0.013), although the end‐tidal MAC multiple during the final 10 min of anesthesia was similar for both groups. Early recovery as evidenced by the time to response to commands after sevoflurane was 33% more rapid than it was after halothane (P < 0.001), although the time to discharge from hospital was similar for both anesthetics. The mean (+/‐SD) plasma concentration of inorganic fluoride 1 h after discontinuation of sevoflurane was 10.3+/‐3.5 micro Meter. The overall incidence of adverse events attributable to sevoflurane was similar to that of halothane, although the incidence of agitation attributable to sevoflurane was almost threefold greater than that attributable to halothane (P < 0.004). Conclusions Sevoflurane compared favorably with halothane. Early recovery after sevoflurane was predictably more rapid than after halothane, although this was not reflected in a more rapid discharge from the hospital. The incidence of adverse events was similar for both anesthetics. Clinically, the induction, recovery, and safety characteristics of sevoflurane and halothane are similar. Sevoflurane is a suitable alternative to halothane for use in children undergoing minor ambulatory surgery.

A randomized, double-blinded study of remifentanil versus fentanyl for tonsillectomy and adenoidectomy surgery in pediatric ambulatory surgical patients.

UNLABELLED We compared, in a double-blinded manner, the anesthetic maintenance and recovery properties of remifentanil with a clinically comparable fentanyl-based anesthetic technique in pediatric ambulatory surgical patients. Anesthesia was induced with either halothane or sevoflurane and nitrous oxide and oxygen. Patients were randomized (computer generated) to receive either remifentanil or fentanyl in a blinded syringe with nitrous oxide and oxygen in one of four possibilities: halothane/remifentanil, halothane/fentanyl, sevoflurane/remifentanil or sevoflurane/fentanyl. In patients receiving remifentanil, a placebo bolus was administered, and a continuous infusion (0.25 microg. kg(-1). min(-1)) was begun. In patients receiving fentanyl, a bolus (2 microg/kg) was administered followed by a placebo continuous infusion. The time from discontinuation of the anesthetic to extubation, discharge from the postanesthesia care unit (PACU), and discharge to home, as well as pain scores, were assessed by a blinded nurse observer. Systolic blood pressure and heart rate were noted at selected times, and adverse events were recorded. Remifentanil provided faster extubation times and higher pain-discomfort scores. PACU and hospital discharge times were similar. There were no statistical differences among the groups for adverse events. There were statistically, but not clinically, significant differences in hemodynamic variables. We noted that continuous infusions of remifentanil were intraoperatively as effective as bolus fentanyl. Although patients could be tracheally extubated earlier with remifentanil, this did not translate to earlier PACU or hospital discharge times. In addition, remifentanil was associated with higher postoperative pain scores. The frequent incidence of postoperative pain observed in the postoperative recovery room suggests that better intraoperative prophylactic analgesic regimens for postoperative pain control are necessary to optimize remifentanils use as an anesthetic for children. IMPLICATIONS This is a study designed to examine the efficacy and safety of a short-acting opioid, remifentanil, when used in pediatric patients. The frequent incidence of postoperative pain observed in the postoperative recovery room suggests that better intraoperative prophylactic analgesic regimens for postoperative pain control are necessary to optimize remifentanils use as an anesthetic for children.

A randomized multicenter study of remifentanil compared with halothane in neonates and infants undergoing pyloromyotomy. I. Emergence and recovery profiles

Pyloric stenosis is sometimes associated with hemodynamic instability and postoperative apnea. In this multicenter study we examined the hemodynamic response and recovery profile of remifentanil and compared it with that of halothane in infants undergoing pyloromyotomy. After atropine, propofol, and succinylcholine administration and tracheal intubation, patients were randomized (2:1 ratio) to receive either remifentanil with nitrous oxide and oxygen or halothane with nitrous oxide and oxygen as the maintenance anesthetic. Pre- and postoperative pneumograms were done and evaluated by an observer blinded to the study. Intraoperative hemodynamic data and postanesthesia care unit (PACU) discharge times, PACU recovery scores, pain medications, and adverse events (vomiting, bradycardia, dysrhythmia, and hypoxemia) were recorded by the study’s research nurse. There were no significant differences in patient age or weight between the two groups. There were no significant differences in hemodynamic values between the two groups at the various intraoperative stress points. The extubation times, PACU discharge times, pain medications, and adverse events were similar for both groups. No patient anesthetized with remifentanil who had a normal preoperative pneumogram had an abnormal postoperative pneumogram, whereas three patients with a normal preoperative pneumogram who were anesthetized with halothane had abnormal pneumograms after.

A randomized multicenter study of remifentanil compared with halothane in neonates and infants undergoing pyloromyotomy. II. Perioperative breathing patterns in neonates and infants with pyloric stenosis

Although former preterm birth infants are at risk for postoperative apnea after surgery, it is unclear whether the same is true of full-term birth infants. We evaluated the incidence of apnea in 60 full-term neonates and infants undergoing pyloromyotomy both before and after anesthesia. All subjects were randomized to a remifentanil- or halothane-based anesthetic. Apnea was defined by the presence of prolonged apnea (>15 s) or frequent brief apnea, as observed on the pneumocardiogram. Apnea occurred before surgery in 27% of subjects and after surgery in 16% of subjects, with no significant difference between subjects randomized to remifentanil or halothane anesthesia. This apnea was primarily central in origin, occurred throughout the recording epochs, and was associated with severe desaturation in some instances. Of the subjects with normal preoperative pneumocardiograms, new onset postoperative apnea occurred in 3 (23%) of 13 subjects who received halothane-based anesthetics versus 0 (0%) of 22 subjects who received remifentanil-based anesthetics (P = 0.04). Thus, postoperative apnea can follow anesthesia in otherwise healthy full-term infants after pyloromyotomy and is occasionally severe with desaturation. New-onset postoperative apnea was not seen with a remifentanil-based anesthetic.

Single-Dose Ondansetron Prevents Postoperative Vomiting in Pediatric Outpatients

This randomized, double-blind, parallel-group, multicenter study evaluated the safety and efficacy of ondansetron (0.1 mg/kg to 4 mg intravenously) compared with placebo in the prevention of postoperative vomiting in 429 ASA status I-III children 1-12 yr old undergoing outpatient surgery under nitrous oxide- and halothane-based general anesthesia. The results show that during both the 2-h and the 24-h evaluation periods after discontinuation of nitrous oxide, a significantly greater percentage of ondansetron-treated patients (2 h 89%, 24 h 68%) compared with placebo-treated patients (2 h 71%, 24 h 40%) experienced complete response (i.e., no emetic episodes, not rescued, and not withdrawn; P < 0.001 at both time points). Ondansetron-treated patients reached criteria for home readiness one-half hour sooner than placebo-treated patients (P < 0.05). The age of the child, use of intraoperative opioids, type of surgery, and requirement to tolerate fluids before discharge may also have affected the incidence of postoperative emesis during the 0- to 24-h observation period. Use of postoperative opioids did not have any effect on complete response rates in this patient population. We conclude that the prophylactic use of ondansetron reduces postoperative emesis in pediatric patients, regardless of the operant influential factors. Implications: Postoperative nausea and vomiting often occur after surgery and general anesthesia in children and are the major reason for unexpected hospital admission after ambulatory surgery. Our study demonstrates that the prophylactic use of a small dose of ondansetron reduces postoperative vomiting in pediatric patients. (Anesth Analg 1997;85:538-45)

Bronchospasm after rapacuronium in infants and children.

IN December 2000, subscribers to the Paediatric Anaesthesia Conference discussion group were invited to post their experiences with rapacuronium (Raplon; Organon Inc., West Orange, NJ) in children in the USA. Specific side effects or responses to rapacuronium were neither requested nor encouraged. The postings yielded 19 cases of bronchospasm, of which 12 were described as severe, from six respondents. These reports caused such concern that the respondents felt obliged to bring this to the attention of their colleagues. Three of the cases are summarized below.

Paramedic intubation training in a pediatric operating room

The authors conducted a prospective study to assess the performance of paramedics with prior adult endotracheal intubation experience in pediatric intubation in the operating room of a teaching hospital. Nineteen paramedic students were observed attempting endotracheal intubation on a total of 57 anesthetized pediatric patients undergoing scheduled surgical procedures. The average age of patients was 5.1 years (range, 6 months to 15.2 years). Average duration of intubation attempts was 22.7 +/- 10.7 seconds, with a success rate on first attempt of 74%. Only minor complications occurred, and were limited to intubation attempts of greater than 45 seconds duration in four cases (6%), and patient oxygen saturation less than 90% in one case (2%). The study suggests that paramedics may be successfully incorporated into a hospitals clinical training program, and can receive closely supervised experience in pediatric endotracheal intubation without compromising patient care. Such training may increase the willingness of paramedics to attempt emergent prehospital endotracheal intubation of children, as well as increase their success with this potentially life-saving procedure.

Sedation and anesthesia for the pediatric patient undergoing radiation therapy.

Purpose of review Radiation oncology is a cornerstone in the treatment of cancer in children. Although painless, there is a requirement for the child to lie still by themselves in the radiation treatment room, for multiple daily or twice daily treatments for up to 6 weeks. Anesthesia or sedation is usually necessary to achieve this in younger children. This review provides a brief update of the latest developments in radiation oncology and describes the current best practice in anesthesia for these children. Recent findings Advances in radiation therapy and the newer modality of proton beam therapy have enabled radiation oncologists to target tumors more successfully, while avoiding damage to normal tissues. Anesthesiologists are increasingly being asked to provide sedation or anesthesia to ensure a completely immobile patient during radiation therapy. Summary In the vast majority of cases, total intravenous anesthesia or sedation using propofol ensures that the child remains immobile, whilst maintaining spontaneous respiration, an unobstructed airway, and cardiovascular stability.

Pregnancy testing in adolescent presurgical patients.

Because the incidence of pregnancy is approximately 10% in 1519 yr olds (l), some anesthesiologists have suggested that presurgical adolescent females be tested for pregnancy, regardless of their sexual history (23). It is my contention that this is unnecessary and that the available information does not support the practice of screening all presurgical adolescents. Although it is recommended that elective surgery be avoided in pregnancy, two large studies failed to demonstrate an increase in congenital defects after an anesthetic was administered during pregnancy (4,5). And the reality is that the anesthesiologist infrequently sees a pregnant teenager because, over the period of a year, no more than 7.5% would be pregnant, and of these almost half would terminate the pregnancy (1). The lower the prevalence of a condition in a population, the less accurately a screening test predicts the condition (6). In a test population where approximately 5% of the individuals have the condition, the incidence of false positives becomes high relative to the number of affected individuals. When the test is performed on an individual likely to have the condition (pregnancy&for example, on an adolescent who is sexually active, who is not using contraception, and who has missed a period-the possibility of a false positive is very small. The imp&awe of obtaining a good history is evident. When a young woman is being prepared for surgery and changing outdoor clothes for a hospital gown in a private area, the admitting nurse can ask questions regarding menstrual and sexual history. If the anesthesiologist feels that pregnancy test is indicated, a urine test can be performed. The possibility of a false positive result, the delay of surgery while waiting for results, the low yield of positive results in this group, and the possible emotional upheaval do not uphold the practice of universal pregnancy testing in these patients.

Anesthesia for microlaryngoscopy

1 Mazzeo AT, Spada A, Pratico C et al. Hypercapnia: what is the limit in pediatric patients? A case of near-fatal asthma successfully treated by multipharmacological approach. Pediatr Anesth 2004; 14: 596–603. 2 Laffey J, Kavanagh B. Carbon dioxide and the critically ill – too little of a good thing? Lancet 1999; 354: 1283–1286. 3 Laffey J, Kavanagh B. Biological effects of hypercapnia. Intensive Care Med 2000; 26: 133–138. 4 Amato M, Barbas C, Medeiros D et al. Effect of a protectiveventilation strategy on mortality in the acute respiratory distress syndrome. N Engl J Med 1998; 338: 347–354. 5 Nomura F, Aoki M, Forbess J et al. Effects of hypercarbic acidotic reperfusion on recovery of myocardial function after cardioplegic ischemia in neonatal lambs. Circulation 1994; 90: 321–327. 6 Vanucci R, Towfighi J, Heitjan D et al. Carbon dioxide protects the perinatal brain from hypoxic-ischemic damage: an experimental study in the immature rat. Pediatrics 1995; 95: 868–874. 7 Akça O, Payne R, Goldbart R et al. Hypercapnic – but not metabolic acidosis preconditions brain slices to hypoxia. Crit Care Med 2003; 31 (Suppl. 2): 143. 8 Shibata K, Cregg N, Engelberts D et al. Hypercapnic acidosis may attenuate acute lung injury by inhibition of endogenous xanthine oxidase. Am J Respir Crit Care Med 1998; 158: 1578– 1584. 9 Litt L, Gonzalez-Mendez R, Severinghaus JW et al. Cerebral intracellular changes during supercarbia: an in vivo 31P nuclear magnetic resonance study in rats. J Cereb Blood Flow Metab 1985; 5: 537–544. 10 Litt L, Gonzalez-Mendez R, Severinghaus JW et al. Cerebral intracellular ADP concentrations during hypercarbia: an in vivo 31P nuclear magnetic resonance study in rats. J Cereb Blood Flow Metab 1986; 6: 389–392. 11 Akça O, Doufas A, Morioka N et al. Hypercapnia improves tissue oxygenation. Anesthesiology 2002; 97: 801–806. 12 Akca O, Liem E, Suleman MI et al. Effect of intra-operative end-tidal carbon dioxide partial pressure on tissue oxygenation. Anaesthesia 2003; 58: 536–542.