Jeffrey P. Morray

Effect of pH and Pco2 on pulmonary and systemic hemodynamics after surgery in children with congenital heart disease and pulmonary hypertension

Fourteen children with congenital heart disease and associated pulmonary hypertension (preoperative mean pulmonary artery pressure (MPAP) 48 mm Hg +/- 1 SEM were examined to determine the effect of arterial carbon dioxide tension (PaCO2) and pH on pulmonary and systemic hemodynamics after surgical repair. Baseline measurements were obtained with hyperventilation to PaCO2 20 to 30 mm Hg (pH 7.56 +/- 0.01 mm Hg). The addition of carbon dioxide to inspired gas to achieve a PaCO2 40 to 45 mm Hg (pH 7.35 +/- 0.01) resulted in a significant increase in MPAP, from 32 +/- 5 mm Hg to 47 +/- 8 mm Hg (p less than 0.05). An increase in mean cardiac index (CI) from 2.7 +/- 0.3 L/min/m2 to 3.3 +/- 0.3 L/min/m2 (p less than 0.05) explained in part the associated increase in MPAP. For a subgroup of eight patients with postoperative MPAP greater than 30 mm Hg (at pH 7.35 to 7.40), pulmonary vascular resistance index (PVRI) also significantly increased (p less than 0.05) as PaCO2 was increased, implying a direct pulmonary vasodilating effect of alkalosis. Removal of carbon dioxide from inspired gas returned hemodynamic values to baseline. The higher the MPAP at physiologic pH the greater the absolute amount of MPAP reduction and PVRI reduction (p less than 0.05) with alkalosis. No complications from alkalosis were seen. We suggest that a trial of hypocarbic alkalosis in the child with severe residual pulmonary hypertension after surgical repair of congenital heart disease is warranted to reduce right ventricular afterload.

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.

Coma scale for use in brain-injured children

The association between admission coma score and eventual outcome was assessed using a coma scale developed for children with a variety of central nervous system injuries. As opposed to the Glasgow coma scale, this scale does not demand assessment of verbalization, and thus can be applied to the preverbal or previously intubated child. Cortical function is graded from 6 (purposeful, spontaneous movements) to 0 (flaccid), and brainstem function is graded from 3 (intact) to 0 (absent and apneic). Maximum total score is 9.In 91 children treated for intracranial hypertension, the association was moderately good. The scale was better in predicting the outcome of patients with hypoxic encephalopathy and head trauma than that of patients with Reyes syndrome, meningitis, or encephalitis. No child with a score of less than 3 survived in spite of intensive therapy. Most of these children were flaccid with depressed or absent brainstem reflexes. No child with flaccidity on admission survived.

Oxygen Delivery and Consumption during Hypothermia and Rewarming in the Dog

Changes in oxygen consumption (VO2) and oxygen delivery (DO2) were compared in three groups of paralyzed, sedated dogs: 1) a group (n = 5) cooled to 29 degrees C and immediately rewarmed to 37 degrees C; 2) a group (n = 5) cooled to and maintained at 29 degrees C for 24 h, and then rewarmed; and 3) a group (n = 5) maintained at 37 degrees C for 24 h. During the cooling phase, in both the acute and prolonged hypothermia animals, VO2 and DO2 decreased significantly from control values (P less than 0.05). The decrease in DO2 occurred as a result of a similar decrease in cardiac index (CI; P less than 0.05) that was associated with a significant increase in systemic vascular resistance index (SVRI; P less than 0.05). Arteriovenous oxygen content difference (C(a-v)O2), O2 extraction ratio, mixed venous oxygen tension (PVO2), pH, and base deficit (BD) were not different from control values even during prolonged hypothermia. Normothermic control dogs also demonstrated a significant decrease in CI (P less than 0.05) at 24 h. Surface rewarming increased VO2 back to control values in the acute hypothermia group and to values above control (P less than 0.05) in the prolonged hypothermia group. DO2 remained below control in both groups, resulting in a significant increase in O2 extraction (P less than 0.05) and a decrease in PVO2 (P less than 0.05) in the prolonged hypothermia animals. Following rewarming administration of sodium nitroprusside returned DO2, CI, and SVRI to control values but did not increase VO2. All animals survived the study without need for inotropic support.(ABSTRACT TRUNCATED AT 250 WORDS)

Thermal injury caused by hot pack application in hypothermic children

A three-year 1 l-month-old boy fell through a layer of ice into a pond. When retrieved about 15 minutes later, he was apneic and pulseless. Cardiopulmonary resuscitation (CPR) was begun. and two varieties of hot packsS§ were placed on his abdomen and back to initiate field rewarming. On arrival at the emergency department a physician noticed that one hot pack was painfully hot and removed the packs. After 20-30 minutes of continued CPR, a heart beat without perfusion was noted. After 45 minutes in the emergency department, effective perfusion and spontaneous respiration returned, but core temperature had fallen to 29°C. Further warming was done in a bath of 38-39°C water. Burns were noticed at the sites of one type of hot pack+ prior to transfer to intensive care (Fig. 1). Subsequent therapy included intracranial pressure monitoring and therapy with hyperventilation, paralysis, mannitol, and pentobarbital coma. During a 1 ‘iz-month hospitalization, he slowly regained speech and ambulation, but developed a hyperactive behavior disorder and did not regain his pre-injury mental development. Several well-circumscribed third degree burns were present on his anterior and posterior trunk and inner arms. They required serial excision, pigskin coverage, and eventual homografting.

Hemodynamic and metabolic effects of two anesthetic techniques in children undergoing surgical repair of acyanotic congenital heart disease

Few comparative data are available to indicate whether fentanyl or isoflurane is better for use in children undergoing operative repair of acyanotic congenital heart disease. In addition, the catecholamine responses in children with congenital heart disease before cardiopulmonary bypass have not been described with either technique. The purpose of our study was to compare the hernodynamic and catecholamine responses to anesthesia and surgical stimulation with isoflurane to those with a fentanyl/diazepam combination in the pre-bypass period, in children undergoing surgical repair of acyanotic congenital heart disease.

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.

Multi-Institutional Survey of Graduates of Pediatric Anesthesia Fellowship: Assessment of Training and Current Professional Activities

We surveyed all the graduates of four fellowship programs in pediatric anesthesia between 1985 and 1993 to assess their current professional activities, their evaluation of fellowship training, and their opinions on future directions of such training.One-hundred ninety-one (62%) of the graduates responded. Nearly all of the respondents had sought fellowship training for pediatric anesthesia and thought that the training was worth-while. At the time of the survey, 40% worked in a childrens hospital, 72% had university or affiliate positions, and 54% had a practice that was >50% pediatric. Those with >or=to12 mo fellowship and/or board certification in pediatrics were the most likely to have a pediatric-dedicated practice. Seventy percent of the respondents thought that fellowship training should be for 12 mo, and the proportion of respondents who recommended inclusion of training in pain management and clinical research was greater than the number who had actually received such training. Fifty-eight percent of respondents supported restriction of fellowship positions in the future, but 83% did not support a mandatory 2-yr fellowship with research training. We conclude that fellowships in pediatric anesthesia seem to be successful in providing training that is not only satisfying to the trainees, but that is also followed by active involvement in the care of children and in the training of residents and fellows in anesthesia. Additional information should be gathered to assess the impact of this training on pediatric care, to formulate a standardized curriculum, and to justify support for such training in the future. Implications: We surveyed graduates of four fellowship programs in pediatric anesthesia (1985-1993) to assess current professional activities, fellowship training, and future directions of such training. Fellowships in pediatric anesthesia seem to provide training that is satisfying to trainees and that is followed by active involvement in the care of children. (Anesth Analg 1997;85:1191-5)

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.

Short-acting barbiturate sedation: effect on arterial pH and PaCO2 in children

One hundred and fifteen unpremedicated children, induced with thiamylal, a short-acting thiobarbiturate, administered rectally (25 mg·kg-1 body wt) or intravenously (6 mg·kg-1) had arterial pH of 7.36 ± 0.03 and PaCO2 of 40 · 4 mmHg. In 22 children over two years of age, the use of fentanyl (1.2 · 0.7 μg·kg-1) in addition to the thiamylal did not change blood gas data compared to those children over two years receiving only barbiturates (pH 7.36 vs 7.36, PaCO2 41 vs 40 mmHg). Children with cyanotic congenital heart disease showed similar pH andPaCO2 to acyanotic childrenfollowing administration of the short-acting barbiturate. Thiobarbiturates, given in a titrated fashion under direct observation, have clinically small effects on arterial pH and PaCO2 in paediatric patients.RésuméCent-quinze enfants non prémédiqués induits avec du thiamylal, un thiobarbilurique à courte action, administré par voie rectale (25 mg·kg-1) ou par voie intraveineuse (6 mg·kg-1) avait un pH artériel de 7.36 ± 0.03 et une PaCO2 à 40 ± 4 mmHg. Chez 22 enfants âgés de plus que deux ans, ľutilisation du fentanyl (1.2 ± 0.7 μg·kg-1) en plus du thiamylal n’a pas altéré les données de la gazométrie comparativement aux enfants ayant reçu uniquement les barbituriques (pH 7.36 vs 7.36, PaCO2 41 versus 40 mmHg). Les enfants atteints ďune maladie cardiaque congénitale cyanogène ont démontré des pH et des PaCO2 identique aux enfants acyanotiques après administration du barbiturique à courte action. Des thiobarbituriques, administrés sous surveillance et titrés provoquent de faibles effets cliniques sur le pH artériel et la PaCO2 chez les patients pédiatriques.