Robert G. Kettrick

Comparison of cuffed and uncuffed endotracheal tubes in young children during general anesthesia

Background Uncuffed endotracheal tubes are routinely used in young children. This study tests a formula for selecting appropriately sized cuffed endotracheal tubes and compares the use of cuffed versus uncuffed endotracheal tubes for patients whose lungs are mechanically ventilated during anesthesia. Methods Full‐term newborns and children (n = 488) through 8 yr of age who required general anesthesia and tracheal intubation were assigned randomly to receive either a cuffed tube sized by a new formula [size(mm internal diameter) = (age/4) + 3], or an uncuffed tube sized by the modified Coles formula [size(mm internal diameter) = (age/4) + 4]. The number of intubations required to achieve an appropriately sized tube, the need to use more than 21 [center dot] min sup ‐1 fresh gas flow, the concentration of nitrous oxide in the operating room, and the incidence of croup were compared. Results Cuffed tubes selected by our formula were appropriate for 99% of patients. Uncuffed tubes selected by Coles formula were appropriate for 77% of patients (P < 0.001). The lungs of patients with cuffed tubes were adequately ventilated with 2 1 [center dot] min sup ‐1 fresh gas flow, whereas 11% of those with uncuffed tubes needed greater fresh gas flow (P < 0.001). Ambient nitrous oxide concentration exceeded 25 parts per million in 37% of cases with uncuffed tubes and in 0% of cases with cuffed tubes (P < 0.001). Three patients in each group were treated for croup symptoms (1.2% cuffed; 1.3% uncuffed). Conclusions Our formula for cuffed tube selection is appropriate for young children. Advantages of cuffed endotracheal tubes include avoidance of repeated laryngoscopy, use of low fresh gas flow, and reduction of the concentration of anesthetics detectable in the operating room. We conclude that cuffed endotracheal tubes may be used routinely during controlled ventilation in full‐term newborns and children during anesthesia.

Noninvasive ventilation via bilevel positive airway pressure support in pediatric practice.

OBJECTIVE To evaluate the efficacy of bilevel positive airway pressure support in critically ill children with underlying medical conditions. DESIGN Prospective, clinical study. SETTING Pediatric intensive care unit (ICU). PATIENTS Thirty-four patients (6 mos to 20 yrs, mean 11.06 +/- 0.9 yrs) with impending respiratory failure were enrolled in the study. All patients required airway or oxygenation/ventilation support (awake or asleep) and required admission to our pediatric ICU. Each patient served as his or her own control. Exclusion criteria were absent cough or gag reflex, multiple organ system failure, age of <6 mos, vocal cord paralysis, and noncooperation with nasal mask. INTERVENTIONS Bilevel positive airway pressure support ventilation. MEASUREMENTS AND MAIN RESULTS Thirty-four patients with 35 episodes of respiratory insufficiency requiring airway support or oxygenation/ventilatory support were treated with bilevel positive airway pressure support ventilation. Dyspnea score decreased at least two deviations in all patients; dyspnea score decreased five deviations in 67% of patients. Resting heart rate decreased from 126 +/- 3.2 to 102 +/- 3.2 beats/min (p < .001), respiratory rate decreased from 39 +/- 3 to 25 +/- 1 breaths/min (p < .004), bicarbonate concentrations decreased from 30.0 +/- 1.0 to 24.0 +/- 0.7 mmol/L (p < .01), and room air saturation increased from 85 +/- 2% to 97 +/- 1%. Bilevel positive airway pressure support ventilation failure was characterized by an inability to stabilize progression of respiratory failure and the subsequent placement of an artificial airway. Three patients required placement of an artificial airway. CONCLUSIONS A decrease in respiratory rate, heart rate, and dyspnea score and an improvement in oxygenation were noted in >90% of patients studied, resulting in only an 8% frequency of intubation. The efficacy of bilevel positive airway pressure support ventilation in selected groups of patients indicates the need to include this form of noninvasive pressure support ventilation in the care offered by pediatric ICUs.

Improvement in Lung Mechanics as a Function of Age in the Infant with Severe Bronchopulmonary Dysplasia

Summary: Pulmonary function tests were performed in two groups of infants with bronchopulmonary dysplasia; a group less than 7 months of age with severe ventilator-dependent respiratory failure (Group A), and a group 7–22 months of age during resolution of their disease (Group B). Group A patients had significantly elevated minute volume, low specific compliance, elevated inspiratory and expiratory pulmonary resistance, and low functional residual capacity. Group B patients also demonstrated elevated minute volume, whereas specific compliance, inspiratory pulmonary resistance and functional residual capacity were within normal limits, and expiratory pulmonary resistance was only slightly above normal. With the exception of minute volume, the differences between the groups were significant (P < 0.05). Sequential studies of resistance and compliance over 4–5 months in two patients in the younger group demonstrated values that approached or achieved normal range. It is concluded that pulmonary mechanics improve with age in the infant with severe bronchopulmonary dysplasia.Speculation: The high minute ventilation demonstrated in children with branchopulmonary dysplasia results from increased dead space ventilation. With low compliance and high resistance the young infant cannot sustain the high minute ventilation required, and respiratory failure ensues, requiring mechanical ventilation. As the child grows, chest wall strength, compliance, and resistance improve, allowing the infant to sustain a high spontaneous minute ventilation, and thus to tolerate gradual reduction and eventual removal of mechanical ventilatory support.

Ondansetron reduces the incidence and severity of poststrabismus repair vomiting in children

This prospective, randomized, placebo-controlled, double-blinded study evaluated the antiemetic efficacy of ondansetron and metoclopramide in 90 ASA physical status I or II children, 2-17 yr of age, undergoing strabismus repair. After anesthetic induction and prior to eye muscle manipulation, subjects received normal saline 0.3 mL/kg (Group 1), metoclopramide 0.25 mg/kg (Group 2), or ondansetron 0.15 mg/kg (Group 3), intravenously. There were no differences between groups with respect to age, weight, gender, fluids received, number of eye muscles repaired, anesthetic technique, or time in the operating room. The incidence of vomiting in Groups 1, 2, and 3 was 50%, 27%, and 10% prior to discharge, and 67%, 53%, and 30% during the 24 h after surgery, respectively. The number of children vomiting prior to discharge and within 24 h of surgery was significantly reduced in Group 3 compared with Group 1 (P < 0.003 and P < 0.015, respectively). The number of vomiting episodes per patient in Groups 1, 2, and 3 was 1.1, 0.5, and 0.1 prior to discharge, and 4.5, 2.6, and 1.2 during the 24 h after surgery (P < 0.0005 and P < 0.004, respectively). Ondansetron 0.15 mg/kg intravenously after the induction of anesthesia reduces the incidence and severity of vomiting after strabismus repair both prior to discharge from the hospital and during the 24 h after surgery.

A Study of Desmopressin and Blood Loss during Spinal Fusion for Neuromuscular Scoliosis A Randomized, Controlled, Double-Blinded Study

Background: Studies examining the use of desmopressin acetate (DDAVP) have shown variable results in DDAVPs efficacy for reducing blood loss. Studies of adults having cardiac surgery and of children having spinal fusion have suggested that patients with complicated medical histories and complex surgical procedures may benefit from use of DDAVP. Therefore, this study was designed to examine the homeostatic effects of DDAVP in children with severe cerebral palsy undergoing spinal fusion. Methods: A randomized, double‐blinded, and placebo‐controlled trial of DDAVP was designed to enroll 40 patients. However, termination of the study was advised by the Institutional Review Board after 21 patients were enrolled. All patients had spastic quadriplegic‐type cerebral palsy and were randomly assigned to one of two groups. The DDAVP group received 0.3 micro gram/kg DDAVP in 100 ml normal saline, and the placebo group received normal saline alone. All patients were anesthetized with nitrous oxide, oxygen, isoflurane, and fentanyl. Factor VIIIC and von Willebrands factor (vWF) concentrations were measured in blood drawn before DDAVP infusion and 1 h after infusion. Blood pressure was maintained at a systolic pressure of less than 100 mmHg. Use of crystalloids, packed erythrocytes, platelets, and fresh frozen plasma were based on criteria established by protocol. Estimated blood loss was assessed by weighing sponges and measuring suctioned blood from canisters. Results: Estimated blood loss (intraoperative and postoperative) and amount of packed erythrocytes transfused were similar for the DDAVP and placebo groups. Concentrations of both factor VIIIC and vWF were significantly greater after DDAVP infusion when compared with concentrations after placebo infusion. Conclusions: In the children who had complex spinal fusion, there was no difference in estimated blood loss between those who received DDAVP and those who received a placebo. Administration of DDAVP significantly increased factor VIIIC and vWF levels.

Dose Response of Succinylcholine at the Adductor Pollicis of Children with Cerebral Palsy During Propofol and Nitrous Oxide Anesthesia

Children with cerebral palsy may be resistant to paralysis induced by nondepolarizing neuromuscular blocking drugs. Potency of a bolus of succinylcholine in children with cerebral palsy has not been studied previously. Therefore, we measured the response of the adductor pollicis to succinylcholine in children with cerebral palsy anesthetized with propofol and nitrous oxide. Forty children between the ages of 2 and 10.2 yr with spastic quadriplegic cerebral palsy were randomly assigned to receive 100, 175, 250, or 375 micrograms/kg of succinylcholine during anesthesia with propofol and nitrous oxide. The ulnar nerve was stimulated with a train-of-four supramaximal stimulus every 10 s and the compound electromyogram of the adductor pollicis recorded by a Datex NMT monitor. Plasma cholinesterase activity was measured in all patients with three different substrates (propionylthiocholine, benzoylcholine, and succinylcholine). Dibucaine number was also determined using inhibition of benzoylcholine degradation. ED50 of succinylcholine was 146.8 micrograms/kg with 95% confidence intervals of 111.4-193.7 micrograms/kg. ED95 of succinylcholine was 360.5 micrograms with 95% confidence intervals of 273.3-475.5 micrograms/kg. We conclude that children with cerebral palsy are slightly sensitive to succinylcholine, but probably not sufficiently to be clinically important.

Pulmonary function in chronic respiratory failure of infancy.

We studied pulmonary function in 7 infants age 3–16 months who were dependent upon mechanical ventilation due to bronchopulmonary dysplasia (BPD). Raised lower expiratory airway resistance (RAe), low dynamic lung compliance (CL) and rapid respiratory frequency (f) characterized the breathing pattern in these infants. End-tidal carbon dioxide tension (PECO2) was elevated in spite of abnormally high minute ventilation (VE). One infant died of respiratory failure, 1 died of sepsis and 1 of an occluded tracheostomy after discharge from the hospital. Another infant still requires mechanical ventilation at age 18 months. Recovery from chronic respiratory failure in 4 infants occurred between age 1.2–2.5 years. The infants recovered concomitant with the ability to sustain a high VE in spite of persistently elevated RA and low CL. All of the surviving infants, although developmentally delayed, have the potential for home care with further growth and development.

Clinical correlates of successful weaning from mechanical ventilation in severe bronchopulmonary dysplasia.

The hospital records of 7 patients with severe bronchopulmonary dysplasia (BPD) were reviewed. All patients were ventilator dependent for prolonged periods (mean duration intermittent mandatory ventilation (IMV) 14.3 ± 3.5 months) but eventually were successfully weaned from mechanical ventilation and sent home. The early phase of the disease was characterized by excessive CO2 retention, tachypnea, and inability to tolerate reductions in IMV. A turning point was reached halfway through the course of mechanical ventilation (7.3 ± 1.4 months) which was identified by a persistent and significant reduction in Paco2 and spontaneous respiratory rate. Thereafter, gradual reductions in IMV were generally well tolerated. Average monthly weight gain was less prior to the turning point than it was subsequently.

Juvenile laryngeal papillomatosis: scary anaesthetic!

We describe three children ages 20 to 33 months who presented for surgical resection of their laryngeal papillomata. Their anaesthetic management revealed the severity of obstruction which these children presented and the obstacles that faced the anaesthesiologist trying to secure the airway and provide adequate ventilation. The airway obstruction had both a fixed and a dynamic component to it. This was evidenced by the ability of the children to maintain ventilation when spontaneously breathing. But, they exhibited total obstruction when ventilation was attempted via mask using positive pressure. It is possible to encounter obstruction to ventilation after the trachea has been intubated because of papillomata that were ‘shaved off,’ filling the tracheal tube lumen.