Caesarean Delivery Rate Review: An Evidence-Based Analysis.

BACKGROUND: In 2007, caesarean deliveries comprised 28% of all hospital deliveries in Ontario. Provincial caesarean delivery rates increased with maternal age and varied by Local Health Integration Network. However, the accepted rate of caesarean delivery in a low-risk maternal population remains unclear. OBJECTIVES: To review the literature to assess factors that affect the likelihood of experiencing a caesarean delivery, and to examine Ontario caesarean delivery rates to determine whether there is rate variation across the province. DATA SOURCES: Data sources included publications from OVID MEDLINE, OVID MEDLINE In-Process and Other Non-Indexed Citations, OVID Embase, EBSCO Cumulative Index to Nursing & Allied Health Literature (CINAHL), and EBM Reviews, as well as data from the Canadian Institute for Health Information Discharge Abstracts Database and the Better Outcomes and Registry Network. REVIEW METHODS: A mixed-methods approach was used, which included a systematic review of the literature to delineate factors associated with the likelihood of caesarean delivery and an analysis of administrative and clinical data on hospital deliveries in Ontario to determine provincial caesarean delivery rates, variation in rates, and reasons for variation. RESULTS: Fourteen systematic reviews assessed 14 factors affecting the likelihood of caesarean delivery; 7 factors were associated with an increased likelihood of caesarean delivery, and 2 factors were associated with a decreased likelihood. Five factors had no influence. One factor provided moderate-quality evidence supporting elective induction policies in low-risk women. The overall Ontario caesarean delivery rate in a very-low-risk population was 17%, but varied significantly across Ontario hospitals. LIMITATIONS: The literature review included a 5-year period and used only systematic reviews. The determination of Robson class for women is based on care received in hospital only, and the low-risk population may have included data from women with obstetrical conditions that warranted a caesarean delivery. CONCLUSIONS: There is moderate-quality evidence that-compared with expectant management-an induction policy is associated with a decrease in caesarean delivery rates in low-risk women. There is significant caesarean delivery rate variation among Ontario hospitals.

Beta2 adrenergic antagonist inhibits cerebral cortical oxygen delivery after severe haemodilution in rats.

BACKGROUND: Haemodilution has been associated with neurological morbidity in surgical patients. This study tests the hypothesis that inhibition of cerebral vasodilatation by systemic beta2 adrenergic blockade would impair cerebral oxygen delivery leading to tissue hypoxia in severely haemodiluted rats. METHODS: Under general anaesthesia, cerebral tissue probes were placed to measure temperature, regional cerebral blood flow (rCBF) and tissue oxygen tension (P(Br)O2) in the parietal cerebral cortex or hippocampus. Baseline measurements were established before and after systemic administration of either a beta2 antagonist (10 mg kg(-1) i.v., ICI 118, 551) or saline vehicle. Acute haemodilution was then performed by simultaneously exchanging 50% of the estimated blood volume (30 ml kg(-1)) with pentastarch. Arterial blood gases (ABGs), haemoglobin concentration (co-oximetry), mean arterial blood pressure (MAP) and heart rate (HR) were also measured. Data were analysed using a two-way anova and post hoc Tukey's test [mean (sd)]. RESULTS: Haemodilution reduced the haemoglobin concentration comparably in all groups [71 (9) g litre(-1)]. There were no differences in ABGs, co-oximetry, HR and MAP measurements between control and beta2 blocked rats, either before or 60 min after drug or vehicle administration. In rats treated with the beta2 antagonist there was a significant reduction in parietal cerebral cortical temperature, regional blood flow and tissue oxygen tension, relative to control rats, 60 min after haemodilution (P<0.05 for each). These differences were not observed when probes were placed in the hippocampus. CONCLUSION: Systemic beta2 adrenergic blockade inhibited the compensatory increase in parietal cerebral cortical oxygen delivery after haemodilution thereby reducing cerebral cortical tissue oxygen tension.

Single-breath vital capacity rapid inhalation induction in children: 8% sevoflurane versus 5% halothane.

BACKGROUND: The authors compared the speed of induction of anesthesia with sevoflurane with and without nitrous oxide with the speed of halothane and nitrous oxide using a single-breath vital capacity induction. METHODS: With informed parental consent, 51 healthy unpremedicated children aged 5-12 yr were randomized to inhale a single breath of one of three gas mixtures: 8% sevoflurane in 66% nitrous oxide, 8% sevoflurane in oxygen, or 5% halothane in 66% nitrous oxide. A blinded observer recorded the times to loss of the eyelash reflex, return of conjugate gaze, the presence of airway reflex responses, involuntary movement, and hemodynamic responses. RESULTS: Forty-two children completed the study. The times (mean +/- SD) to loss of the eyelash reflex with sevoflurane/nitrous oxide, 38+/-8 s, and for sevoflurane-oxygen, 34+/-12 s, were less than that with halothane-nitrous oxide, 58+/-17 s (P < 0.01). Movement occurred less frequently during sevoflurane than during halothane anesthesia (P < 0.05). The times to return of conjugate gaze and the incidence of airway reflex responses were similar among the groups. The incidence of dysrhythmias in the sevoflurane groups was less than that in the halothane group (P < 0.01). CONCLUSIONS: Induction of anesthesia with a single breath of 8% sevoflurane with or without 66% nitrous oxide is more rapid than with 5% inspired halothane with 66% nitrous oxide in children. The incidence of movement and dysrhythmias during a single-breath induction with sevoflurane are less than they are with halothane.

Recovery characteristics of propofol anaesthesia, with and without nitrous oxide: a comparison with halothane/nitrous oxide anaesthesia in children.

Few studies have examined whether nitrous oxide influences the recovery characteristics of propofol anaesthesia. The present study examined the effect of nitrous oxide on the recovery characteristics of propofol anaesthesia, and compared these data with those for halothane/nitrous oxide anaesthesia. Sixty children aged 3-12 years were assigned at random to receive one of three maintenance regimens: propofol with or without nitrous oxide (70%) or halothane/nitrous oxide (70%). During propofol/N2O anaesthesia, the infusion rate of propofol (180 +/- 39 micrograms.kg-1.min-1) required to maintain the mean arterial pressure and heart rate within 20% of the baseline values was significantly less than that during propofol/O2 (220 +/- 37 micrograms.kg-1.min-1; P < 0.005). The time from discontinuation of anaesthesia to eye-opening (11 +/- 6 min), to response to commands (12 +/- 6 min), and to return of full wakefulness (21 +/- 10 min) after propofol/N2O were similar to those after propofol/O2, but significantly less (by approximately 30%) than those after halothane (P < 0.05). The overall incidence of emesis after propofol/N2O (53%) was greater than that after propofol/O2 (17%, P < 0.05) and comparable to that after halothane/N2O (58%). These data suggest that N2O has little effect on the rate of recovery after propofol, but significantly increases the incidence of postoperative emesis, thereby attenuating one of the main attributes of propofol anaesthesia.

Vomiting after adenotonsillectomy in children: a comparison of ondansetron, dimenhydrinate, and placebo.

UNLABELLED: We compared the effectiveness of ondansetron, dimenhydrinate, and placebo for the prevention of postoperative vomiting in children after adenotonsillectomy. In a randomized, placebo-controlled, double-blind study, 74 children, 2-10 yr of age scheduled for adenotonsillectomy as outpatients were given a single i.v. dose of ondansetron (0.1 mg/kg, n = 26), dimenhydrinate (0.5 mg/kg, n = 25), or placebo (saline, n = 23) at induction of anesthesia. The incidence of retching and vomiting (POV) and side effects observed 24 h after surgery were recorded. Demographic data were similar among the three groups. The 24-h incidence of POV was 42%, 79%, and 82% in the ondansetron, dimenhydrinate, and placebo groups, respectively (ondansetron compared with dimenhydrinate [P < 0.02] or placebo [P < 0.01]). The study was stopped after two children vomited large volumes of bloody fluid 9 and 22 h after surgery without previous signs of occult bleeding. Both children had received ondansetron. We conclude that ondansetron is superior to dimenhydrinate or placebo for the prevention of POV after adenotonsillectomy in children. Antiemetics may mask the signs of bleeding after adenotonsillectomy. IMPLICATIONS: I.v. ondansetron (0.1 mg/kg) is more effective than both dimenhydrinate and placebo in preventing vomiting after adenotonsillectomy in healthy children. However, antiemetics may also mask the presence of blood in the stomach by preventing vomiting, and this should be appreciated when adenotonsillectomy is performed on an outpatient basis.

Bupivacaine 0.125% produces motor block and weakness with fentanyl epidural analgesia in children.

PURPOSE: Epidural infusions of fentanyl (2 micrograms.ml-1) alone or combined with bupivacaine 0.125% were compared for perioperative analgesia, motor block and other side-effects in children who underwent urological surgery. METHODS: In a prospective, double-blind study, 42 children, ASA I-II, 1-16 yr, were randomly allocated to receive either epidural F (fentanyl bolus 2 micrograms.kg-1 in 0.5 ml.kg-1 saline followed by 2 micrograms.ml-1 fentanyl infusion) or epidural F-B (fentanyl bolus 2 micrograms.kg-1 in 0.5 ml.kg-1 bupivacaine 0.25% followed by 2 micrograms.ml-1 fentanyl infusion in bupivacaine 0.125%) after induction of general anaesthesia. Adequacy of analgesia, lower limb motor block and side-effects were assessed four hourly postoperatively. RESULTS: Both infusion regimens provided excellent analgesia (median objective pain scores = 0). Epidural infusion rates were similar in the F (0.29 +/- 0.07 ml.kg-1.hr-1) and F-B (0.26 +/- 0.05 ml.kg-1.hr-1) groups. Three children in the F group and all children in the F-B group developed lower limb weakness. (P < 0.05) Bromage scores were different in the F group (median 0, range 0-0.66) compared with the F-B group (median 0.33, range 0-1) (P < 0.001). Other side-effects did not differ. CONCLUSION: Postoperative epidural fentanyl infusion provides equipotent analgesia to administration of a solution including both fentanyl and bupivacaine 0.125% and causes less lower limb weakness. No reduction in the fentanyl requirement resulted from the addition of bupivacaine 0.125%.

Maintenance and recovery characteristics after sevoflurane or propofol during ambulatory surgery in children with epidural blockade.

PURPOSE: To compare the maintenance and recovery characteristics after sevoflurane with those after propofol in children with epidural blockade. METHODS: Fifty unpremedicated, children ASA I-II, 2-8 yr of age, scheduled for elective urological surgery as outpatients, were randomly allocated to receive either: 1) sevoflurane for induction and maintenance of anaesthesia or 2) propofol for induction (2-3 mg.kg-1 i.v.) and for maintenance (5-10 mg.kg-1.hr-1 i.v.). All children received N2O 70% in oxygen before induction and throughout the anaesthetic, rocuronium for neuromuscular blockade and a lumbar or caudal epidural block before incision. Heart rate (HR), systolic blood pressure (SBP), recovery times and all side effects during maintenance and recovery were recorded by a blinded observer. Adverse events during the first 24 hr were also recorded. RESULTS: Mean HR increased 5-10% after induction in both groups reaching a maximum by five minutes. Heart rate returned to baseline by skin incision in the sevoflurane group and by 10 min after induction in the propofol group. During maintenance, HR decreased by 10-20% below baseline values by 20 min in the propofol group only, where it remained for the remainder of the anaesthetic. Similarly, SBP increased by 10% after induction of anaesthesia in both groups, but returned to baseline by 10 min. Light anaesthesia occurred in four (16%) children, all in the propofol group. Emergence and recovery indices were similar in the two groups. DISCUSSION: Sevoflurane and propofol exhibit similar maintenance and recovery profiles when combined with epidural analgesia in children undergoing ambulatory surgery.

Subhypnotic propofol does not treat postoperative vomiting in children after adenotonsillectomy.

PURPOSE: To investigate the efficacy of a subhypnotic dose of propofol to treat vomiting in children after adenotonsillectomy. METHODS: Two hundred and fifty-two children, aged 2-12 yr, underwent a standardized anaesthetic opioid administration, and postoperative care after adenotonsillectomy, adenoidectomy or tonsillectomy. A prospective, double-blinded, placebo-controlled study was performed in 70 of the patients who retched or vomited after surgery and who had intravenous access. Patients were assigned randomly to receive either 0.2 mg.kg-1) propofol (n = 35), or placebo (intralipid 10%, n = 35). RESULTS: The overall incidence of vomiting during the first 18-24 hr was 50%. Of those who had received propofol after the first episode of vomiting, 63% relapsed requiring a rescue antiemetic compared with 57% of those who had received intralipid (P = NS). Of the children who received propofol, 54% experienced pain on injection and 46% were mildly sedated compared with 3% and 11%, respectively, in the placebo group (P < 0.003). CONCLUSION: We conclude that an intravenous bolus of 0.2 mg.kg-1 propofolis not effective in the treatment of postoperative vomiting in children after adenotonsillectomy when a standardized anaesthetic with thiopentone, halothane, nitrous oxide, and 1.5 mg.kg-1 codeine phosphate is used, but it does cause sedation and pain on injection.

Parental perceptions, expectations and preferences for the postanaesthetic recovery of children.

Improvements in anaesthesia have led to the introduction of rapid-acting agents which quicken recovery and decrease sleepiness. Whether parents believe a rapid postanaesthetic recovery is an advantage is unknown. Therefore, we evaluated the parental perceptions, expectations and preferences for the postanaesthetic recovery of children. One hundred and three parents of children having ambulatory surgery completed a structured questionnaire and the results of 101 are presented. Results indicate that 93% of parents expect their child to be sleepy after surgery. Seventy-four per cent of parents indicated they would prefer their child to be sleepy or tired in the first 24 h postoperatively. Eight-five percent of parents would not be upset if their child's discharge was delayed up to three hours because their child was too sleepy. Finally 45.5% of parents are extremely concerned about their child experiencing postoperative pain and 68% believe that their child would be in more pain if they recovered rapidly from the anaesthetic. These results indicate that rapid recovery from anaesthesia and quick discharge from hospital are not key expectations of parents of children admitted for day surgery. Parents associate a rapid recovery with more pain. Parents need to be more fully informed of the advantages of a rapid recovery and reassured that children can recover quickly and completely but at the same time be comfortable postanaesthetic.

Anaesthesia for insertion of ear tubes in children: comparison of propofol, thiopentone and halothane.

To determine the quality of anaesthesia and speed of recovery after propofol anaesthesia for myringotomy in children, 100 children 2-12 years were randomized to one of four anaesthetic regimens for induction/maintenance: thiopentone (STP) (5 mg.kg-1)/halothane, propofol (3 mg.kg-1)/halothane, halothane/halothane or propofol (3 mg.kg-1)/propofol bolus (0.5 mg.kg-1 every 3 min (10 mg.kg-1.h-1)). Nitrous oxide (70%) in oxygen (30%) was used to facilitate insertion of an intravenous catheter and was continued throughout the anaesthetic. We found that the incidence of intraoperative movement in response to surgical stimulation was significantly greater in the prop/prop group 32%, compared with the three other groups (P < 0.02). Although some recovery variables (time to response to questions, sit unaided, tolerate oral fluids, and discharge with fluids) were achieved more rapidly by the prop/ prop group than the other three groups, the times to open eyes, obey commands and, most importantly, discharge from recovery without fluids did not differ between the prop/prop and the hal/ hal groups. We conclude that there is little benefit in using propofol as an induction agent alone or in combination with a propofol maintenance anaesthetic for paediatric myringotomy and tube surgery.

Pharmacokinetics of the active metabolite (MDL 74,156) of dolasetron mesylate after oral or intravenous administration to anesthetized children.

BACKGROUND: Dolasetron mesylate is a selective 5-HT3 receptor antagonist under investigation as an antiemetic in children. Published studies indicate that its antiemetic activity results from the active metabolite (MDL 74,156), which is produced within 10 minutes of administration of dolasetron mesylate. METHODS: The pharmacokinetics of MDL 74,156 and the safety and tolerability of dolasetron mesylate were studied after a single oral or intravenous dose of 1.2 mg.kg-1 dolasetron mesylate to healthy children from 2 to 12 years of age. Oral dolasetron was administered to 12 children 1 to 2 hours before anesthesia. Intravenous dolasteron was administered to 18 children at induction of anesthesia. Serial blood samples were collected for 24 hours after dosing to measure the plasma concentration of MDL 74,156. Indexes of liver and kidney function were determined, and electrocardiograms and adverse events were recorded.

Dimenhydrinate decreases vomiting after strabismus surgery in children.

Dimenhydrinate, an H1-receptor antagonist, has been used to both prevent and treat postoperative vomiting (POV) in children for several decades. However, its effectiveness for POV after strabismus surgery remains anecdotal. This study was designed to determine the effectiveness and side effects of dimenhydrinate for the prevention of POV in children after strabismus surgery. Eighty ASA physical status I or II children, ages 1-12 yr inclusive, who were undergoing strabismus surgery, were prospectively and randomly allocated to receive either dimenhydrinate 0.5 mg/kg intravenously (n = 40) or placebo (n = 40) at induction of anesthesia. The incidence of POV and the times to arousal (and discharge from the recovery room and hospital) were recorded postoperatively in a double blinded manner. For 24 h after discharge from the hospital, all emetic episodes and medications given were recorded by the parents. Demographic data did not differ between the groups. Children who received dimenhydrinate had significantly less POV both inhospital (10%) and overall (30%) than those who received placebo (in-hospital 38%, P < 0.008; overall 65%, P < 0.003). The times to arousal and discharge from the hospital did not differ between the two groups. Dimenhydrinate (0.5 mg/kg) is an effective, safe, and inexpensive antiemetic in children undergoing strabismus surgery. It significantly reduces the incidence of vomiting for 24 h postoperatively and is not associated with prolonged sedation or other adverse effects.

Plasma inorganic fluoride concentrations after sevoflurane anesthesia in children.

BACKGROUND: Sevoflurane is degraded in vivo in adults yielding plasma concentrations of inorganic fluoride [F-] that, in some patients, approach or exceed the 50- micron theoretical threshold for nephrotoxicity. To determine whether the plasma concentration of inorganic fluoride [F-] after 1-5 MAC x h sevoflurane approaches a similar concentration in children, the following study in 120 children scheduled for elective surgery was undertaken. METHODS: Children were randomly assigned to one of three treatment groups before induction of anesthesia: group 1 received sevoflurane in air/oxygen 30% (n = 40), group 2 received sevoflurane in 70% N2O/30% O2 (n = 40), and group 3 received halothane in 70% N2O/30% O2 (n = 40). Mapleson D or F circuits with fresh gas flows between 3 and 61/min were used Whole blood was collected at induction and termination of anesthesia and at 1, 4, 6, 12, and 18 or 24 h postoperatively for determination of the [F-]. Plasma urea and creatinine concentrations were determined at induction of anesthesia and 18 or 24 h postoperatively. RESULTS: The mean (+/- SD) duration of sevoflurane anesthesia, 2.7 +/- 1.6 MAC x h (range 1.1-8.9 MAC x h), was similar to that of halothane, 2.5 +/- 1.1 MAC x h. The peak [F-] after sevoflurane was recorded at 1 h after termination of the anesthetic in all but three children (whose peak values were recorded between 4 and 6 h postanesthesia). The mean peak [F-] after sevoflurane was 15.8 +/- 4.6 microns. The [F-] decreased to <6.2 microns b 24 h postanesthesia. Both the peak [F-] (r2 = 0.50) and the area under the plasma concentration of inorganic fluoride-time curve (r2 = 0.57) increased in parallel with the MAC x h of sevoflurane. The peak [F-] after halothane, 2.0 +/- 1.2 microns, was significantly less than that after sevoflurane (P<0.00012) and did not correlate with the duration of halothane anesthesia (MAC x h; r2 = 0.007). Plasma urea concentrations decreased 24 h after surgery compared with preoperative values for both anesthetics (P<0.01), whereas plasma creatinine concentrations did not change significantly with either anesthetic. CONCLUSIONS: It was concluded that, during the 24 h after 2.7 +/- 1.6 MAC x h sevoflurane, the peak recorded [F-] is low (15.8 microns), F- is eliminated rapidly, and children are unlikely to be at risk of nephrotoxicity from high [F-].

Pharmacokinetics of intravenous ondansetron in healthy children undergoing ear, nose, and throat surgery.

BACKGROUND: To determine the pharmacokinetics of the 5-HT3 antagonist ondansetron in children, informed written consent was obtained from the parents of 21 healthy children aged from 3 to 12 years scheduled for ear, nose, and throat surgery. METHODS: The children were stratified according to age: 3 to 7 years and 7.1 to 12 years, and a single intravenous infusion of 2 or 4 mg ondansetron, respectively, was administered over 5 minutes before induction of anesthesia. After completion of the infusion, anesthesia was induced intravenously and maintained with inhalational anesthesia. Whole blood (3 ml) was obtained before administration of ondansetron, at completion of the infusion, at the beginning and end of surgery, and at 3, 4, 6, 8, 10, and 12 hours after start of the infusion. Pharmacokinetic variables were determined with use of standard noncompartmental techniques. RESULTS: Mean plasma clearance was 0.50 L.hr-1.kg-1 and 0.39 L.hr-1.kg-1, the mean volume of distribution at steady-state was 1.70 L.kg-1 and 1.61 L.kg-1, and the mean plasma terminal half-life was 2.6 hours and 3.1 hours for the 2 mg and 4 mg groups, respectively. On a body surface area basis, mean plasma clearance was 14.0 and 13.7 L.hr-1.m-2 and mean volume of distribution was 47.7 and 55.9 L.m-2 for the 2 and 4 mg groups, respectively. There were no serious adverse events attributable to ondansetron. CONCLUSIONS: These data indicate that the pharmacokinetics of ondansetron in children from 3 to 12 years old are predictable and similar to those in adults. The elimination half-life of ondansetron increases in parallel with age. However, clearance is constant when normalized to body surface area, but the volume of distribution increases over the age range studied.