Desmond Bohn

Outcome of Out-of-Hospital Cardiac or Respiratory Arrest in Children

BACKGROUND Among adults who have a cardiac arrest outside the hospital, the survival rate is known to be poor. However, less information is available on out-of-hospital cardiac arrest among children. This study was performed to determine the survival rate among children after out-of-hospital cardiac arrest and to identify predictors of survival. METHODS We reviewed the records of 101 children (median age, two years) with apnea or no palpable pulse (or both) who presented to the emergency department at the Hospital for Sick Children in Toronto. The characteristics of the patients and the outcomes of illness were analyzed. We assessed the functional outcome of the survivors using the Pediatric Cerebral and Overall Performance Category scores. RESULTS Overall, there was a return of vital signs in 64 of the 101 patients; 15 survived to discharge from the hospital, and 13 were alive 12 months after discharge. Factors that predicted survival to hospital discharge included a short interval between the arrest and arrival at the hospital, a palpable pulse on presentation, a short duration of resuscitation in the emergency department, and the administration of fewer doses of epinephrine in the emergency department. No patients who required more than two doses of epinephrine or resuscitation for longer than 20 minutes in the emergency department survived to hospital discharge. The survivors who were neurologically normal after arrest had had a respiratory arrest only and were resuscitated within five minutes after arrival in the emergency department. Of the 80 patients who had had a cardiac arrest, only 6 survived to hospital discharge, and all had neurologic sequelae. CONCLUSIONS These results suggest that out-of-hospital cardiac arrest among children has a very poor prognosis, especially when efforts at resuscitation continue for longer than 20 minutes and require more than two doses of epinephrine.

Ventilatory predictors of pulmonary hypoplasia in congenital diaphragmatic hernia, confirmed by morphologic assessment

We carried out a prospective study in 66 infants with congenital diaphragmatic hernia within the first 6 hours of life to determine whether outcome is related to the degree of underlying pulmonary hypoplasia, as predicted by preoperative PaCO2, when correlated with an index of ventilation (VI = mean airway pressure X respiratory rate) and confirmed by postmortem analysis of the lung. Those infants with PaCO2 greater than 40 mm Hg before surgery had a 77% mortality; when PaCO2 reduction could be achieved only with VI greater than 1000, the mortality was still greater than 50%. After repair, however, the ability to hyperventilate to PaCO2 less than 40 mm Hg proved to be an important determinant of survival; only one of 31 infants in this group died, whereas only two of 27 infants with PaCO2 greater than 40 mm Hg survived. In 16 infants with PaCO2 greater than 40 mm Hg despite hyperventilation, high-frequency oscillatory ventilation was started. This resulted in a rapid fall in PaCO2, but 14 of the 16 infants had only temporary improvement in oxygenation, and died. In five of the infants who died, alveolar number was assessed by postmortem morphometric analysis; there was a severe reduction to less than 10% of published normal neonatal values. Pulmonary vascular changes of increased muscularization were less remarkable than those observed in infants with persistent pulmonary hypertension. Our findings suggest that the degree of pulmonary hypoplasia (which would not be influenced by surgical repair), rather than the pulmonary vascular abnormality, mainly determines survival. Consideration could therefore be given to an initial nonsurgical approach to congenital diaphragmatic hernia, with the expectation that pulmonary function might improve and pulmonary vascular resistance decrease.

Effect of surgical repair on respiratory mechanics in congenital diaphragmatic hernia

To determine whether surgical repair of congenital diaphragmatic hernia (CHD) results in improvement in respiratory mechanics, we measured respiratory system compliance in nine patients (five survivors and four nonsurvivors) before and after operation. In all nine infants, CHD was diagnosed within 6 hours of life, and surgical repair was through an abdominal approach after a period of stabilization. Measurements were made noninvasively, using the passive expiratory flow-volume technique. In only one of the nine infants did compliance immediately improve after surgical repair, and in another it showed no change. Both of these infants survived, with an uneventful postoperative course. In the remaining seven infants, however, postoperative compliance immediately decreased to 10% to 77% from the preoperative value. The four infants with more than 50% decrease in compliance died with increasing hypoxemia and acidosis. These results suggest that respiratory mechanics in CHD, far from improving, frequently deteriorate as a result of repair of the hernia. The role of urgent surgery in this malformation should be reevaluated.

Congenital diaphragmatic hernia—A tale of two cities: The Toronto experience☆

PURPOSE The optimal therapy for congenital diaphragmatic hernia (CDH) is evolving. This study analyzes the results of treatment of CDH in a large tertiary care pediatric center using conventional and high-frequency oscillatory ventilation (HFOV) without extracorporeal membrane oxygenation (ECMO) contrasting these with a parallel study from a similar large urban center using conventional ventilation with ECMO. METHODS Between 1981 and 1994, 223 consecutive neonates who had CDH diagnosed in the first 12 hours of life were referred for treatment before repair. Conventional ventilation was used with conversion to HFOV for refractory hypoxemia or hypercapnia, and a predicted near 100% mortality rate. ECMO was used in only three patients, all of whom died. A retrospective database was collected. Thirty-one clinical variables were tested for their association with the outcome. Common ventilatory and oxygenation indices were tested for their prognostic capability. RESULTS Apgar scores, birth weight, right-sided defects, pneumothorax, total ventilatory time, and the use of high frequency oscillatory ventilation were the only variables associated with outcome. A modified ventilatory index and postductal A-aDo2 were strong prognostic indicators. From 1981 to 1984 surgery was performed on an emergency basis. Since 1985 surgery was deferred until stabilization had been achieved. This resulted in a shift in the mortality from postoperative to preoperative with no change in total survival. HFOV did not alter the overall survival. Results of autopsies performed (70%) showed significant pulmonary hypoplasia and barotrauma as the primary causes of death. The survival was 54.7%. CONCLUSION Conventional ventilation with HFOV produced equal survival to conventional ventilation with ECMO in two comparable series. Pulmonary hypoplasia was the principle cause of death. This continued high mortality at both centers suggests that new therapies are required to improve outcomes.

Pediatric in-intensive-care-unit cardiac arrest: incidence, survival, and predictive factors.

Objective:To describe the incidence, survival, and neurologic outcome of in–intensive-care-unit (ICU) cardiac arrest and to identify factors predictive of survival to hospital discharge. Methods:We performed a retrospective cohort study. Eligible patients were <18 yrs of age and experienced a cardiac arrest during their admission to a multidisciplinary pediatric intensive care unit in the 5.5-yr period ending June 2002. Cardiac arrest was defined as the administration of chest compressions or defibrillation for a nonperfusing cardiac rhythm. Mortality and the Paediatric Cerebral Performance Score were measured and presented according to the Utstein style. Factors predictive of survival to hospital discharge were identified by univariate analysis and independent predictors were identified by multivariate analysis. Main Measurements and Results:Ninety-one children had cardiac arrest, yielding an incidence of 0.94 cardiac arrests per 100 admissions. Resuscitation was successful in 75 (82%) children, 61 (67%) survived 24 hrs, 25 (27%) children survived to ICU discharge and 23 (25%) to hospital discharge. At hospital discharge, the median Pediatric Cerebral Performance Category score was 2 (range, 1–3) and the median Pediatric Overall Performance Category score was 3 (range, 1–4). No child was assessed as normal on both scores. The independent positive predictors of hospital mortality were the presence of renal failure before cardiac arrest (odds ratio [OR], 6.1; 95% confidence interval [CI], 1.8–31), being on epinephrine infusion at time of cardiac arrest (OR, 9.5; 95% CI, 1.5–62), and the administration of one or more calcium boluses during resuscitation (OR, 5.4; 95% CI, 1.1–25). The use of extracorporeal membrane oxygenation (ECMO) within 24 hrs after cardiac arrest was associated with reduced hospital mortality (OR, 0.18; 95% CI, 0.04–0.76). Conclusions:In-ICU cardiac arrest is associated with high in-hospital mortality and subsequent morbidity in survivors. Prearrest renal dysfunction and epinephrine infusion were associated with increased in-hospital mortality. The use of post-arrest ECMO within 24 hrs was associated with reduced mortality. Rigorous prospective evaluation of the role of ECMO following cardiac arrest is needed.

Influence of hypothermia, barbiturate therapy, and intracranial pressure monitoring on morbidity and mortality after near-drowning

We retrospectively evaluated the clinical and pathologic effects of hypothermia and high-dose barbiturate therapy on hypoxic/ischemic cerebral injury after near-drowning in children. Of 40 near-drowned patients admitted to the ICU, 13 died, seven had permanent cerebral damage, and 20 survived. Twenty-four patients (group 1) were treated with a regime of hyperventilation, hypothermia, and high-dose phenobarbitone while intracranial pressure (ICP) was continuously monitored. Of ten who died in this group, three were diagnosed as having cerebral death shortly after admission; autopsy revealed severe cerebral edema with herniation. The remaining seven nonsurvivors had severe cerebral hypoxia without raised ICP and had the features of severe adult respiratory distress syndrome and hypoxic/ischemic damage to other organs. Six of these seven patients developed septicemia which was invariably associated with a profound neutropenia. Sixteen patients (group 2) were treated with a similar protocol but without hypothermia. Three of these patients died but only one developed septicemia. Neutropenia after resuscitation from near-drowning seemed to indicate a poor prognosis; the mean polymorphonuclear leukocyte count in nonsurvivors (1.9 ± 0.5 x 109 cell/L) was significantly (p < .01) lower than that in survivors (6.4 ± 1.1 x 109 cell/L). Hypothermia was associated with a decreased number of circulating PMNs but did not increase the number of neurologically intact survivors. Similarly, although barbiturates may control ICP, their use did not improve outcome. Because severe cerebral edema and herniation after near-drowning is usually associated with irreversible brain damage, measures to control brain swelling such as hypothermia and barbiturates will be of little benefit. Therapy should be directed at maintaining cerebral perfusion and adequate oxygenation to prevent further damage to vital organs.

Ventilation by high-frequency oscillation in humans.

In a recent demonstration in anesthetized dogs normal gas exchange was maintained over prolonged periods of time by applying at the airway very high frequency (15 Hz) sinusoidal oscillations with a volume less than half that of the physiologic dead space. Now, 12 patients have been ventilated in this way for as long as 1 hour. All were being mechanically ventilated either following major vascular surgery or for treatment of respiratory failure. Their ages varied from 3 days to 74 years; weights ranged from 2.5 to 100 kg. Oscillatory volumes of 1.5 to 3.0 ml/kg of body weight were delivered using a piston pump operating at a frequency of 15 Hz. Baseline cardiorespiratory data obtained during standard mechanical ventilation were compared to the means of four to six observations obtained during the period of oscillation. The calculated shunt fraction decreased significantly from 12.5 ± 9.1 during mechanical ventilation to 8.2 ± 6.8 during oscillation with no change in either arterial CO2 tensions (37.7 ± 5.0 torr during mechanical ventilation; 37.6 ± 5.4 torr during oscillation) or cardiac output (6.1 ± 2.1 L/min during mechanical ventilation; 6.0 ± 2.3 L/min during oscillation). Two patterns of response were evident. Patients with predominantly right to left shunting (e. g., septic shock) showed little change in calculated Qs/Qt with oscillation. In patients with chronic obstructive lung disease in whom one would expect to have extensive V/Q mismatch, oscillation resulted in large decreases in Qs/Qt ratio (e. g., 25.0 ± 13.0). Oscillatory ventilation appears to be a promising new way of achieving gas exchange with minimal risk of barotrauma to the lung.

Lesson of the week: Acute hyponatraemia in children admitted to hospital: retrospective analysis of factors contributing to its development and resolution.

Do not infuse a hypotonic solution if the plasma sodium concentration is less than 138 mmoVl

Pulse oximetry in pediatric intensive care: Comparison with measured saturations and transcutaneous oxygen tension

We evaluated a new pulse oximeter designed to monitor beat-to-beat arterial oxygen saturation (SaO2) and compared the monitored SaO2 with arterial samples measured by co-oximetry. In 40 critically ill children (112 data sets) with a mean age of 3.9 years (range 1 day to 19 years), SaO2 ranged from 57% to 100%, and PaO2 from 27 to 128 mm Hg, heart rates from 85 to 210 beats per minute, hematocrit from 20% to 67%, and fetal hemoglobin levels from 1.3% to 60%; peripheral temperatures varied between 26.5 degrees and 36.5 degrees C. Linear correlation analysis revealed a good agreement between simultaneous pulse oximeter values and both directly measured SaO2 (r = 0.95) and that calculated from measured arterial PaO2 (r = 0.95). The device detected several otherwise unrecognized drops in SaO2 but failed to function in four patients with poor peripheral perfusion secondary to low cardiac output. Simultaneous measurements with a tcPO2 electrode showed a similarly good correlation with PaO22 (r = 0.91), but the differences between the two measurements were much wider (mean 7.1 +/- 10.3 mm Hg, range -14 to +49 mm Hg) than the differences between pulse oximeter SaO2 and measured SaO2 (1.5% +/- 3.5%, range -7.5% to -9%) and were not predictable. We conclude that pulse oximetry is a reliable and accurate noninvasive device for measuring saturation, which because of its rapid response time may be an important advance in monitoring changes in oxygenation and guiding oxygen therapy.

Hypotonic versus isotonic saline in hospitalised children : a systematic review

Background: The traditional recommendations which suggest that hypotonic intravenous (IV) maintenance fluids are the solutions of choice in paediatric patients have not been rigorously tested in clinical trials, and may not be appropriate for all children. Aims: To systematically review the evidence from studies evaluating the safety of administering hypotonic versus isotonic IV maintenance fluids in hospitalised children. Methods: Data sources: Medline (1966–2006), Embase (1980–2006), the Cochrane Library, abstract proceedings, personal files, and reference lists. Studies that compared hypotonic to isotonic maintenance solutions in children were selected. Case reports and studies in neonates or patients with a pre-existing history of hyponatraemia were excluded. Results: Six studies met the selection criteria. A meta-analysis combining these studies showed that hypotonic solutions significantly increased the risk of developing acute hyponatraemia (OR 17.22; 95% CI 8.67 to 34.2), and resulted in greater patient morbidity. Conclusions: The current practice of prescribing IV maintenance fluids in children is based on limited clinical experimental evidence from poorly and differently designed studies, where bias could possibly raise doubt about the results. They do not provide evidence for optimal fluid and electrolyte homoeostasis in hospitalised children. This systematic review indicates potential harm with hypotonic solutions in children, which can be anticipated and avoided with isotonic solutions. No single fluid rate or composition is ideal for all children. However, isotonic or near-isotonic solutions may be more physiological, and therefore a safer choice in the acute phase of illness and perioperative period.