Determination of rebreathing oxygen consumption and derivation of oxygen delivery in intubated mongrel dogs after phlebotomy and isoproterenol infusion.

This study attempted to determine the correlation between oxygen consumption (VO2), pulmonary-capillary blood flow (QEPC), and oxygen delivery (DO2) by rebreathing and invasive techniques obtained over a range of hemoglobin concentration and cardiac output. Twenty mongrel dogs were instrumented with central arterial and venous catheters to determine DO2 by thermodilution cardiac output and standard formulas. The animals were administered isoproterenol in doses that increased DO2 and subsequently were serially phlebotomized by 30%, 40%, and 50% to decrease DO2. All animals were studied using a rebreathing technique to determine noninvasively VO2, QEPC, and DO2. Sixteen dogs completed the experimental protocol. A correlation analysis was carried out for VO2, QEPC, and DO2 obtained by the rebreathing and invasive methods. Thermodilution cardiac output increased from 3.91 +/- 1.77 L/min at baseline to 8.19 +/- 2.50 L/min during isoproterenol infusion. Hemoglobin varied from 12.21 +/- 1.26 gm% at baseline to 5.21 +/- 1.36 g% at 50% phlebotomy. Over this range of conditions, significant correlations were obtained between rebreathing VO2 and invasive VO2 (r = 0.80, p < 0.0001), rebreathing QEPC and invasive QEPC (r = 0.79, p < 0.0001), and rebreathing DO2 and invasive DO2 (r = 0.82 p < 0.0001). These data demonstrate that the rebreathing technique can be used to monitor oxygen metabolism over wide ranges of DO2.

Perinatal pathology casebook.

Citrullinemia, a rare inborn error of metabolism, is characterized by a deficiency of argininosuccinic acid synthetase that results in large increases in plasma ammonia, citrulline, and glutamine, with normal acid-base balance. The neurologic symptoms vary from poor feeding, vomiting, and irritability to hypotonia, apnea, and death. The most common pathologic findings at autopsy are cerebral edema and focal neuronal necrosis. We describe a case of fulminant citrullinemia in an infant in whom the major pathologic findings included diffuse cerebral edema and a lack of overt metabolic derangement characteristic of neonates with a urea cycle defect. Our case differs from the classic presentation of citrullinemia in that subarachnoid hemorrhage was identified early in the clinical course. We report the first observation of subarachnoid hemorrhage in an infant with a urea cycle defect.

Esophageal-aortic erosion associated with double aortic arch and tracheomalacia. Experience with 2 infants.

Patients with double aortic arch may require lengthy intubation for ventilatory support. The need for endotracheal and nasogastric intubation may be prolonged in such patients because of associated tracheomalacia. Iatrogenic tracheal or esophageal erosion with subsequent aortic fistulization is an unusual but catastrophic complication that may result from such intubation. We report the cases of 2 infants with double aortic arch and tracheomalacia who developed iatrogenic esophageal-aortic erosion. This complication was successfully managed in 1 of the infants. We conclude from our experience that the important steps in preventing this complication include 1) expediting the exclusion of upper-airway compromise in intubated infants who have a presentation characteristic of bronchospastic airway disease (hyperinflation and hypercapnia) that seems unresponsive to usual therapeutic measures; and 2) expediting the diagnosis of vascular ring in order to minimize the duration of dual tracheal and esophageal intubation. Effective management of this problem, once established, requires primary closure of the esophageal perforation, removal of the nasogastric tube, interposition of thick viable tissue between the esophagus and the aorta, and decompressive gastrostomy and feeding jejunostomy. Concomitant aortopexy may be appropriate.

Laryngeal papillomatosis presenting as acute airway obstruction in a child.

Upper airway obstruction, regardless of cause, can masquerade or be misdiagnosed as lower airway disease in children. In such cases, therapeutic trials of antibiotics, bronchodilators, and over-the-counter medications for symptom relief routinely fail; however, the original diagnosis often goes unchallenged. If the obstructive process is progressive, then acute occlusion of the airway may occur, rapidly leading to suffocation and death if resuscitation is unsuccessful. Outlined in this report is the case of a young female with a history of asthma, poorly responsive to outpatient treatment, who presented with respiratory arrest. The cause of the respiratory collapse was later identified as a large laryngeal papilloma, a condition rarely encountered by emergency physicians.

Accuracy and utility of a continuous intra-arterial blood gas monitoring system in pediatric patients.

OBJECTIVES: To determine the accuracy of the Paratrend 7 continuous intra-arterial blood gas monitor (CI-ABGM) in radial and femoral artery catheters placed in children compared with simultaneous measurements of pH, Pa(CO2), and Pa(O2) performed by intermittent blood gas analysis. To determine sensor longevity in pediatric patients at different arterial sites. To determine the utility of CI-ABGM for tracking unanticipated events related to blood gas deterioration. SETTING: A pediatric intensive care unit of a university hospital. DESIGN: A prospective clinical investigation. PATIENTS: Fifty critically ill pediatric patients, ranging in age from 1 wk to 18 yrs of age, who required either radial or femoral artery catheters for intermittent arterial blood gas monitoring. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: A Paratrend 7 intra-arterial sensor was placed through either an 18- or 20-gauge catheter previously inserted into the radial or femoral artery. At clinically predetermined intervals ranging from every 1 to 8 hrs, the CI-ABGM measurements of pH, P(CO2), and P(O2) were compared with the values determined by standard intermittent blood gas analysis. The Paratrend 7 system values were individually adjusted to match ABG results when the Paratrend 7 pH differed by greater than +/-0.05 units, P(CO2) was greater than +/-5 torr (0.7 kPa), and P(O2) was greater than +/-15% of the ABG value. Significant aberrations in gas exchange defined as unanticipated events were categorized as isolated metabolic acidosis (pH <7.20), hypercapnia (P(CO2), >70 torr; 9.3 kPa), and hypoxemia (P(O2), <50 torr; 6.7 kPa). All unanticipated events were earmarked from consecutive monitoring epochs ranging from 4 to 24 hrs duration from the time of Paratrend 7 sensor insertion to the time of sensor removal. Fifteen sensors were placed into the radial artery, 34 sensors were placed into the femoral artery, and one sensor was initially placed in the radial and moved to a femoral artery location. Mean radial artery insertion duration was 35 hrs. Mean femoral artery duration was 137.2 hrs. A total of 1445 pairs of ABG results were available for comparison. After removal of individual values, which did not meet inclusion criteria, 1411 pH data pairs, 1408 P(CO2) data pairs, and 1326 P(O2) data pairs were analyzed. The bias and precision for the pH data were 0.00 and 0.04 units, respectively; for the P(CO2) data were -0.4 and 4.8 torr (-0.05 and 0.64 kPa), respectively; and for the P(O2) data 1.0 and 25 torr (0.1 and 3.3 kPa), respectively. Detection of unanticipated events was evenly spread across the three categories and was most commonly related to iatrogenic causes or cardiac failure. Persistent waveform dampening necessitating sensor removal was more frequently encountered in radial placement compared to femoral placement. CONCLUSIONS: The Paratrend 7 CI-ABGM is accurate within the extremes of physiologic gas exchange typically encountered in the pediatric intensive care setting. The device is capable of tracking extreme fluctuations in gas exchange with a response rate suitable for making real-time therapeutic decisions. The sensor can be recommended for insertion into a femoral artery cannula. There is a high incidence of blood pressure waveform dampening encountered in radial artery use.