Single-dose ondansetron prevents postoperative vomiting in pediatric outpatients.

UNLABELLED: 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patients (2 h 71%, 24 h 40%) experienced complete response (i.e., no emetic episodes, not rescued, and not withdrawn; P 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.

Acquired QT interval changes and neck dissections.

STUDY OBJECTIVE: To determine if acquired long QT syndrome following right or left, radical or modified, neck dissections result in malignant arrhythmias or deaths. DESIGN: Prospective study. SETTING: Inpatient head and neck service of the Massachusetts Eye and Ear Infirmary. PATIENTS: 69 patients who underwent extensive neck surgery, without congenital long QT syndrome, medications known to prolong the QT interval, preoperative ventricular arrhythmias, or electrolyte abnormalities. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Preoperative and postoperative electrolytes were evaluated. Preoperative and postoperative electrocardiograms and QT intervals were evaluated. Continuous intraoperative and 10- to 12-hour postoperative monitoring of lead II or V5 were evaluated. Twenty-six patients (Group 1) underwent either right radical neck dissection or modified right radical neck dissection, 25 patients (Group 2) underwent either left radical neck dissection or modified left neck dissection, and 18 patients (Group 3) underwent extensive neck surgery without radical or modified neck dissection. Postoperatively, 38 patients (19 Group 1, 11 Group 2, and 8 Group 3 patients) developed a QT interval corrected for heart rate (QTc) of greater than 440 milliseconds. Repeated measures analysis of variance, comparing preoperative and postoperative QTc showed a statistically significant preoperative to postoperative change, but no significant difference among the three groups. No malignant arrhythmias or deaths were recorded in any of the three groups. CONCLUSIONS: Acquired long QT syndrome following radical neck dissection, without congenital, metabolic, or pharmacologic disturbance, is unlikely to trigger malignant arrhythmias, as previously reported for right radical neck dissection.

Metoclopramide reduces the incidence of vomiting after tonsillectomy in children.

The efficacy of intravenous metoclopramide in controlling vomiting in children after tonsillectomy was determined in a prospective randomized, double-blind investigation. One hundred two unpremedicated, ASA physical status I or II children between the ages of 1 and 15 yr who were undergoing surgical removal of the tonsils, with or without adenoidectomy, were studied. Anesthesia was induced either with halothane, nitrous oxide, and oxygen by mask or by intravenous thiopental and was maintained with halothane, nitrous oxide, oxygen, and intravenous morphine (0.1 mg/kg). Each child randomly received either 0.15 mg/kg of metoclopramide or saline solution placebo intravenously after transfer to the postanesthesia care unit. All episodes of vomiting were recorded for 24 h after completion of surgery. The incidence of vomiting in the saline solution group was 70%, compared with 47% in the metoclopramide group (P = 0.026). The authors conclude that the administration of intravenous metoclopramide in a dose of 0.15 mg/kg on arrival in the postanesthesia care unit significantly decreases the incidence of vomiting in children after tonsillectomy.

A comparison of propofol, midazolam, and methohexital for sedation during retrobulbar and peribulbar block.

STUDY OBJECTIVE: To compare the efficacy of propofol, methohexital, and midazalom in providing adequate sedation during administration of retrobulbar block and satisfactory postoperative amnesia. DESIGN: Retrospective chart review over a 4-month period. SETTING: Ambulatory patients in the main operating room of a university-affiliated hospital. PATIENTS: One hundred forty-seven ambulatory patients undergoing ophthalmologic surgery of less than 2 hours' duration under regional anesthesia consisting of retrobulbar or peribulbar block and intravenous (IV) sedation. INTERVENTIONS: One of three drugs--propofol 0.47 +/- 0.06 mg/kg, midazolam 0.02 +/- 0.005 mg/kg, or methohexital 0.45 +/- 0.16 mg/kg--was administered IV. Patients were observed for a minimum of 60 seconds or until adequate sedation was achieved, after which a retrobulbar or peribulbar block was performed. MEASUREMENTS AND MAIN RESULTS: Blood pressure, electrocardiogram, and oxygen saturation were monitored and recorded. Patients were observed for apnea, hiccups, pain on injection, excitement, tremor, grimacing, or verbal response during the block. The requirement for additional sedation intraoperatively was noted. Patients were questioned postoperatively in the ambulatory recovery room for recall of needle insertion or discomfort during the block, as well as about their satisfaction with the overall experience. CONCLUSIONS: Grimacing or verbal response during the retrobulbar or peribulbar block did not predict or correlate with patient recall. Propofol was equal to both midazolam and methohexital in providing adequate sedation and postoperative amnesia but possesses the added advantages of reduced postoperative vomiting, lower intraocular pressure, and earlier return-to-home readiness.

Interaction of intraocular air and sulfur hexafluoride with nitrous oxide: a computer simulation.

The diffusion dynamics of intravitreal gas bubbles injected during retinal reattachment procedures were studied using a mathematical model. This model predicts the effect of 70 per cent nitrous oxide anesthesia on the volume of the intravitreal bubble. The calculations indicate that when 70 per cent nitrous oxide administration is continued following intravitreal gas injection, there is a rapid, almost threefold increase in the volume of the injected bubble. When nitrous oxide is discontinued at the time of intravitreal injection, a maximum initial bubble expansion of only 35 per cent occurs. If nitrous oxide is discontinued 15 minutes prior to intravitreal injection, the mathematical model indicates that, at most, there will be a 15 per cent expansion of the bubble volume. The model calculations indicate that there is little difference in intravitreal bubble volume whether air of 100 per cent oxygen is used during the anesthetic. The two major factors that influence intravitreal bubble volume are the mixture of air or SF6 injected and the pattern of nitrous oxide use during anesthesia. These factors can be controlled. The importance of bubble volume changes on intraocular pressure and retinal blood flow also depend on other factors such as scleral rigidity, blood pressure, the presence of glaucoma, and the size of the injected gas bubble relative to the total vitreal volume.

Local anesthesia for ophthalmic surgery: patient preparation and management.

Many ophthalmic procedures are performed in elderly patients who have serious concurrent disease. Local anesthesia with sedation can be a safe, advantageous method of management. Uneventful ophthalmic surgery under local anesthesia depends on proper patient selection, preparation, and perioperative management. Patients should understand the procedures and be cooperative. Preparation includes a through medical evaluation. Medical problems must be stable and appropriately managed. The goal of premedication is to have a calm, cooperative patient. Narcotic and an antiemetic sedative such as either promethazine, hydroxyzine, or droperidol should be given according to age and weight. A benzodiazepine may be added for amnesia and anxiolytic effect. Naloxone or physostigmine are available to specificity reverse the effects of narcotics or benzodiazepines, respectively. Awareness of the toxicity and limitations of local anesthetics is important for their safe use.

Cumulative dose-response curves for gallamine: effect of altered resting thumb tension and mode of stimulation.

Neuromuscular blockade studies often use the thumb adductor twitch response to ulna nerve stimulation. Two factors that may influence the results are the resting muscle tension (initial fiber length) and the pattern of the stimulus wave form. This study was undertaken to improve understanding of the effect of these factors and lead to better controlled study conditions and more consistent data. During nitrous oxide-barbiturate-narcotic anesthesia in 10 normal adult patients, as the resting thumb tension was increased from 50 to 200 g, the evoked thumb adductor twitch response (Grass stimulator, 0.25 Hz) was augmented by 28%. There was only a 2.5% increase in the evoked (developed) tension when the resting tension was further increased from 200 to 300 g. Developed tension at 50 g was significantly (p less than 0.001) less than at the other resting tensions. The developed tension at 100 g was also significantly (p less than 0.05) less than at resting tensions of 200 or 300 g. Cumulative dose-response curves for gallamine in nine patients were not significantly altered by increasing resting tension from 50 to 200 g. Biphasic (Block-Aide monitor) or single square wave (Grass stimulator) stimuli wave forms in nine normal adult patients yielded gallamine dose-response curves that were not statistically different. The muscle response to biphasic stimulation during a non-depolarizing blockade was not affected by the average muscle refractory period. Because of the significantly lower developed tension at resting tension settings of 50 to 100 g, a practical consideration during neuromuscular function studies would be to have the resting thumb tension adjusted and rechecked for each patient and kept within the 200-300-g range to ensure maximum uniform developed tension. The type of stimulus wave form selected will not affect results as long as it is used consistently throughout the study.

Re-evaluation of dosage and duration of action of d-tubocurarine in the pediatric age group.

A cumulative dose-response curve for d-tubocurarine based on body weight was determined for 44 infants and children 1 day to 7 years of age during halothane, nitrous oxide and oxygen anesthesia. Depression of thumb adduction was measured. Age difference did not affect the mean dose-effect response. Infants less than 10 days old, however, showed the wideest deviation of responses. When the effect of d-tubocurarine is determined by twitch response, infants and children are more resistant to d-tubocurarine and recover faster than adults from similar levels of neuromuscular depression. Monitoring of neuromuscular function by train-of-four stimulation proved as useful as it is in adults.