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D L Wessel

Publications and source records attributed to D L Wessel.

At least 55 records · Page 3Linked to original sources
PubMed1995

Cerebrovascular accidents following the Fontan operation.

The Fontan operation is one of the most common cardiac operations for children with congenital heart disease beyond the first year of age. Although the surgical mortality of this procedure has improved over the past 2 decades, the neurologic outcome in this population is not well described. We performed a retrospective review of 645 patients who underwent the Fontan procedure at Children's Hospital in Boston over the 15-year period between August, 1978 and July, 1993, to describe the incidence of postoperative cerebrovascular accidents or strokes among survivors. We identified 17 patients (2.6%) who suffered a stroke following the Fontan operation. The risk period for stroke in our population extended from the first postoperative day to 32 months after the Fontan procedure. The pre-, intra-, and postoperative clinical features of these patients are described.

Adolescent↗
PubMed1995

Clinical applications of inhaled nitric oxide in children with pulmonary hypertension.

We have presented our experience with the use of inhaled nitric oxide in children with congenital heart disease and pulmonary hypertension, which indicates that nitric oxide is a selective pulmonary vasodilator that may improve patient management, particularly after surgical procedures requiring cardiopulmonary bypass. Indeed, we have now seen several patients in whom all resuscitative maneuvers for the treatment of pulmonary hypertensive crises were unsuccessful until inhaled nitric oxide was added to the therapeutic regimen. In addition, our studies using inhaled nitric oxide as an investigational probe point toward endothelial injury as a contributor to post-cardiopulmonary bypass pulmonary vasoconstriction. Inhaled nitric oxide relieves pulmonary vasoconstriction associated both with left atrial or pulmonary venous hypertension and following the relief of mitral valve or pulmonary venous obstruction. Absence of a response on the usually reactive pulmonary vascular bed of the neonate should prompt a careful search for anatomic, and possibly surgically remediable, pulmonary vascular obstruction. In the short term nitric oxide is less effective in the older patient with obliterative pulmonary vascular disease. It is possible that recent experimental work with long-term nitric oxide inhalation might be applicable to this group of patients. Nitric oxide may have a unique role in the management of the patient after lung transplantation, as it both reduces right ventricular afterload and improves intrapulmonary shunting. Is nitric oxide the ideal agent for testing pulmonary vascular reactivity? Nitric oxide is simple to deliver by either mask or ventilator and, as a trial of vasoreactivity over 15 min, remains free of side effects that might be encountered during long-term administration, such as methemoglobinemia or nitrogen dioxide toxicity. Indeed, no patient developed significant methemoglobinemia after a trial of nitric oxide and neither was a level of nitrogen dioxide above 1 ppm registered during the administration. Thus, nitric oxide gas fulfills many of the ideal characteristics, as suggested by Rubin,92 required of a drug to test the acute responsiveness of the pulmonary circulation. It has better pulmonary dilating effects than systemic, a short half-life, and minimal adverse effects and it can be both easily and quickly administered. Whether it is able to reliably predict the effect of long-term administration of orally active agents awaits confirmation. Certainly, inhaled nitric oxide is rapidly becoming the standard agent to test pulmonary vascular reactivity during diagnostic cardiac catheterization at our institution.

Administration, Inhalation↗
PubMed1995

Pulmonary vascular resistance in infants after cardiac surgery: role of carbon dioxide and hydrogen ion.

OBJECTIVE: The objective of this study was to describe the effects of altering arterial PCO2 and pH on pulmonary vascular resistance in infants after cardiopulmonary bypass for cardiac surgery. DESIGN: Prospective study (with each patient as his or her own control). SETTING: Cardiac intensive care unit in a children's hospital. PATIENTS: We studied 15 infants (ages ranging from 0.4 to 15.6 months; median 5.7) who were mechanically ventilated during the immediate postoperative period after corrective cardiac surgery. INTERVENTIONS: The study was designed to have the following three stages: In the baseline stage, the initial postoperative hemodynamic parameters were stabilized and body temperature was normalized. In the hypercarbia stage, with FIO2 at 0.40, the rate of ventilation was decreased to produce an end-tidal CO2 level of > 55 torr (> 7.3 kPa). This stage established a clinical model of increased pulmonary vascular resistance. With the minute ventilation held constant in order to maintain a constant PaCO2, the arterial pH was increased by administration of a 4-mEq/kg iv dose of sodium bicarbonate (sodium bicarbonate stage). Arterial blood gas and hemodynamic determinations were obtained after a 10-min stabilization period at each stage. Drug infusions were not altered during the study period. MEASUREMENTS AND MAIN RESULTS: In the hypercarbia stage (stage 2), the mean PaCO2 increased from 36 +/- 5 torr (4.8 +/- 0.7 kPa) (at baseline) to 55 +/- 16 torr (7.3 +/- 2.1 kPa) (p < .01). As a result, the mean arterial pH decreased from 7.48 +/- 0.05 to 7.31 +/- 0.03 (p < .01). During this stage, the mean pulmonary arterial pressure increased from 21 +/- 6 to 30 +/- 8 mm Hg (p < .01) but the cardiac index remained unchanged (3.7 +/- 1.2 to 3.8 +/- 1.2 L/min/m2). Pulmonary vascular resistance index increased from 4.1 +/- 2.0 to 6.0 +/- 3.1 U.m2 (p < .01). After the administration of sodium bicarbonate (stage 3), the arterial pH increased to 7.44 +/- 0.06 (p < .05), while the PaCO2 was unchanged. The pulmonary vascular resistance index decreased to 3.1 +/- 1.5 U.m2 (from 6.0 +/- 3.1 U.m2; p < .01) as a result of both a decrease in mean pulmonary arterial pressure (to 26 +/- 6 mm Hg; p < .01) and a concomitant increase in cardiac index to 5.1 +/- 1.6 L/min/m2 (p < .01). CONCLUSIONS: Increasing the arterial pH by the administration of sodium bicarbonate both lowers the pulmonary arterial pressure and increases the cardiac index, resulting in a decrease in pulmonary vascular resistance. These changes were observed without alteration in PaCO2. Metabolic alkalosis may have a role in the treatment of increased pulmonary vascular resistance in infants after cardiopulmonary bypass for cardiac surgery.

Carbon Dioxide↗
PubMed1995

Milrinone: systemic and pulmonary hemodynamic effects in neonates after cardiac surgery.

OBJECTIVE: To evaluate the hemodynamic effects of intravenous milrinone in neonates with low cardiac output after cardiac surgery. DESIGN: Prospective cohort study. SETTING: Pediatric cardiac intensive care unit. PATIENTS: Ten neonates with low cardiac output (cardiac index of < or = 3.0 L/min/m2) after corrective cardiac surgery were enrolled in the study. The neonates' ages ranged from 3 to 27 days (median 5) and their weights ranged from 2.0 to 4.8 kg (median 3.7). The diagnoses were: transposition of the great arteries (n = 6, including two with ventricular septal defect), tetralogy of Fallot (n = 2), truncus arteriosus (n = 1), and total anomalous pulmonary venous connection (n = 1). INTERVENTIONS: Milrinone was intravenously administered in three stages: a) baseline stage, in which patients had a stable hemodynamic status, ventilation and gas exchange, hemostasis, and body temperature; b) loading stage, in which a 50 microgram/kg intravenous loading dose of milrinone was administered over 15 mins; and c) infusion stage, in which milrinone was continuously infused at 0.50 microgram/kg/min for 30 mins. MEASUREMENTS AND MAIN RESULTS: The mean heart rate increased after the loading stage (149 +/- 13 to 163 +/- 12 beats/min, p < .01) but slowed during the infusion stage (154 +/- 11 beats/min, p < .01 vs. loading stage). Both right and left atrial pressures were lowered in all ten neonates. Compared with baseline, mean arterial pressure decreased after the loading stage (66 +/- 12 to 57 +/- 10 mm Hg, p < .01) but did not decrease further at the infusion stage (59 +/- 12 mm Hg); changes in mean pulmonary arterial pressure were comparable. Cardiac index increased from a baseline mean of 2.1 +/- 0.5 to 3.0 +/- 0.8 L/min/m2 (p < .01) with the loading stage, and was maintained at 3.1 +/- 0.6 L/min/m2 during the infusion stage. Systemic vascular resistance index decreased below baseline values with loading, from 2136 +/- 432 to 1336 +/- 400 dyne.sec/cm5.m2 (p < .01), and pulmonary vascular resistance index also decreased with loading dose of milrinone, from 488 +/- 160 to 360 +/- 120 dyne.sec/cm5.m2 (p < .01). There was no change in the rate pressure index, an indirect measurement of myocardial oxygen consumption, throughout the study. CONCLUSIONS: Administration of milrinone in neonates with low cardiac output after cardiac surgery lowers filling pressures, systemic and pulmonary arterial pressures, and systemic and pulmonary vascular resistances, while improving cardiac index. Milrinone increases heart rate without altering myocardial oxygen consumption. While milrinone appears to be effective and safe during short-term use, the relative distribution of inotropic and vasodilatory properties of milrinone remains to be elucidated.

Cardiac Output, Low↗
PubMed1995

Inhalation of nitric oxide. An innovative therapy for treatment of increased pulmonary vascular resistance.

Critical care of patients during pulmonary hypertensive crises is difficult and treatment is hazardous. Conventional therapy has relied on hyperventilation with oxygen and the use of nonselective intravenous vasodilators. The limitations of this approach have prompted clinical investigations of new therapeutic modalities based on recent advances in vascular biology. Inhaled nitric oxide can be used selectively to manipulate the pulmonary vasculature and treat a variety of pulmonary hypertensive disorders. Preliminary studies appear promising as results of properly conducted trials to evaluate efficacy and toxicity are awaited.

Administration, Inhalation↗
PubMed1994

Inhaled nitric oxide in the treatment of postoperative graft dysfunction after lung transplantation.

Pulmonary hypertension and transient graft dysfunction may complicate the postoperative course of patients undergoing lung transplantation. We report the acute effect of inhaled nitric oxide (80 ppm) on hemodynamics and gas exchange in 6 patients (median age, 14 years; range, 5 to 21 years) after lung transplantation as well as the effect of extended treatment over 40 to 69 hours in 2 patients. In 5 patients with pulmonary hypertension nitric oxide lowered mean pulmonary artery pressure (from 38.4 +/- 1.6 to 29.4 +/- 3.1 mm Hg; p < 0.05), pulmonary vascular resistance index (from 9.3 +/- 1.4 to 6.4 +/- 1.3 Um2; p < 0.05), and intrapulmonary shunt fraction (from 28.6% +/- 8.3% to 21.0% +/- 5.7%; p < 0.05). There was a 28.4% +/- 7.2% reduction in transpulmonary pressure gradient with only minor accompanying effects on the systemic circulation. Mean arterial pressure decreased only 2.7% +/- 5% (from 76.4 +/- 2.2 to 74 +/- 2.3 mm Hg; p = not significant), and systemic vascular resistance index by 4.2% +/- 9.7% (from 21.7 +/- 3.1 to 20.6 +/- 3.6 Um2; p = not significant). Cardiac index was unchanged (from 3.5 +/- 0.8 to 3.6 +/- 0.7 L.min-1.m-2; p = not significant). Nitric oxide caused a sustained improvement in oxygenation and pulmonary artery pressure during extended therapy at doses of 10 ppm. There were no major side effects. However, transient methemoglobinemia (9%) developed in 1 patient after 10 hours of nitric oxide treatment. Nitric oxide may be useful in the treatment of pulmonary hypertension and the impaired gas exchange that occurs after lung transplantation.

Acetylcholine↗
PubMed1994

Size disparity in pediatric lung transplantation.

Donor scarcity and the limitations of organ preservation dictate that a wide size range be used to maximize effective donor utilization in pulmonary transplantation. Problems of size disparity are magnified in the pediatric population, where relevant dimensions vary considerably by age. There have been 10 pediatric lung recipients (7 bilateral, 2 single, 1 heart-lung) at our institution since 1991. The age range was 3 to 26 years (mean, 13.7), and the weight range was 15 to 57 kg (mean, 33.6). Diagnoses included cystic fibrosis (5), pulmonary fibrosis (2), pulmonary hypertension (2), and arteriovenous malformation (1). The donor-to-recipient weight ratio ranged from 0.45 to 1.9, and the donor-to-recipient thoracic height ratio ranged from 0.6 to 1.6. Lobar resection and delayed chest closure was required in one case and was successful. Cardiopulmonary bypass was used electively in seven cases. No reexplorations for bleeding were necessary. Two of the three hospital deaths resulted from right ventricular failure, judged to be secondary to excessive pulmonary artery pressures intraoperatively associated with small donor allografts. Elective bypass had not been used. Inhaled nitric oxide (6 patients) and/or extracorporeal membrane oxygenation (2 patients) were used for temporary postoperative support. The hospital survival rate was 70% (7/10). One late death occurred 14 months postoperatively and was caused by obliterative bronchiolitis. The authors conclude that size disparity is a significant problem in pediatric lung transplantation. However, with elective use of cardiopulmonary bypass and aggressive postoperative support, a broad size range can be used.

Adolescent↗
PubMed1994

West syndrome following deep hypothermic infant cardiac surgery.

Postoperative seizures are among the more common complications of cardiac surgery in children. These seizures have traditionally been considered benign, transient phenomena with little, if any, prognostic significance. We report 4 infants with early postoperative seizures following cardiac surgery who later developed the previously unreported complication of West syndrome, with infantile spasms, hypsarrhythmia, and developmental delay. This group constitutes 6% of 67 infant spasms evaluated over a 5-year period at Boston Children's Hospital. The postoperative seizures in these 4 patients were more difficult than usual to control with antiepileptic therapy; otherwise no intra- or perioperative features distinguished these infants who later developed West syndrome from infants with apparently benign "postpump seizures."

Adrenocorticotropic Hormone↗
PubMed1994

Management and outcome of low birth weight neonates with congenital heart disease.

In 100 consecutive neonates with birth weights < or = 2500 gm (range, 540 to 2500 gm; median, 2200 gm), major congenital heart disease (excluding patent ductus arteriosus, isolated atrial septal defect, and ventricular septal defect) was diagnosed between January 1987 and January 1991; 46 had ductus-dependent lesions. Of the 100 neonates, 30 had genetic aberrations or significant associated congenital anomalies. The four most common cardiac diagnoses were tetralogy of Fallot with or without pulmonary atresia (n = 16); coarctation of the aorta (n = 12); transposition of the great arteries (n = 11); and common atrioventricular canal (n = 11). The hospital survival rate for the entire group of 100 neonates was 70%. The patients were separated into three groups on the basis of the time of intervention. Group 1 (early intervention) included 62 infants. These neonates (including 31 with ductus-dependent lesions) had surgical or catheter intervention during the initial hospitalization (median age, 9 days), all at weights < or = 2500 gm. The hospital survival rate was 81% (50/62); survival rates for palliation (78%, 18/23) and for correction (82%, 32/39) were similar. There were 26 neonates in group 2 (late intervention). These neonates did not have surgical intervention during the initial hospitalization. All were managed medically; survivors were discharged and had surgical procedures later (at a median age of 4.3 months). Six neonates (23%) died during medical management; all 20 survivors returned and had surgical procedures, with 90% survival. Overall survival rate for this group was 69% (18/26). The remaining 12 patients (group 3) had complicating features that precluded intervention; none survived. On the basis of these results, we conclude that early intervention, even with corrective surgery, can be performed in low birth weight neonates with an acceptable mortality rate. Prolonged medical therapy to achieve further weight gain did not appear to improve the survival rate.

Cardiac Catheterization↗
PubMed1994

Delivery and monitoring of inhaled nitric oxide in patients with pulmonary hypertension.

OBJECTIVE: The development of a safe, portable, accurate, and adaptable system to deliver nitric oxide to patients with pulmonary hypertension. DESIGN: A prospective, clinical study. SETTING: Tertiary care pediatric intensive care unit and cardiac catheterization laboratory. PATIENTS: One hundred twenty-three patients (median age 11 months, range 1 day to 72 yrs) with pulmonary hypertension who were administered nitric oxide between November 1991 and July 1993. Ninety-one patients were mechanically ventilated (volume-controlled ventilator, n = 53; pressure-controlled ventilator, n = 5; and a pressure-limited, time-cycled infant ventilator, n = 25). The system was adapted to allow high-frequency oscillator (n = 2) or hand ventilation, and for intraoperative use with an anesthesia machine (n = 6). Thirty-two patients were breathing spontaneously through a mask without assistance. INTERVENTIONS: Nitric oxide was delivered at 10 to 80 parts per million (ppm); the dose was adjusted independently of the FIO2 without altering minute ventilation or tidal volume. MEASUREMENTS AND MAIN RESULTS: Nitrogen dioxide was continuously monitored and exceeded 3 ppm in only four patients. Methemoglobin concentrations were < 5% in all but four patients. Nitric oxide doses remained stable, independent of minute ventilation and could be changed easily and quickly. CONCLUSIONS: Inhaled nitric oxide can be administered precisely and reliably through a variety of delivery systems which can be used in patients of any size. Potential toxicity requires careful monitoring and continued improvement on apparatus design.

Adolescent↗
PubMed1994

Therapeutic use of inhaled nitric oxide.

Nitric oxide is a gaseous endogenous mediator of vascular dilation, neural transmission, defense against microorganisms, and inhibitor of platelet adhesion. Endothelium-derived nitric oxide is important in the maintenance of normal vascular tone in the systemic and pulmonary circulation. The discovery of a selective pulmonary vasodilator has eluded investigators for many years. Inhaled nitric oxide can be used to selectively manipulate the pulmonary vasculature and represents an important advance in pharmacologic strategies aimed at the treatment of the diseased pulmonary circulation. Indeed, preliminary studies of the therapeutic use of inhaled nitric oxide in human pulmonary hypertension and respiratory failure are yielding encouraging and exciting results. Controlled and randomized studies will be required to show improvement in patient outcome and the absence of adverse sequelae from inhaled nitric oxide therapy.

Administration, Inhalation↗
PubMed1994

Gamma-globulin treatment of acute myocarditis in the pediatric population.

BACKGROUND: Myocardial damage in myocarditis is mediated, in part, by immunological mechanisms. High-dose intravenous gamma-globulin (IVIG) is an immunomodulatory agent that is beneficial in myocarditis secondary to Kawasaki disease, as well as in murine myocarditis. Since 1990, the routine management of presumed acute myocarditis at Children's Hospital, Boston, and Children's Hospital, Los Angeles, has included administration of high-dose IVIG. METHODS AND RESULTS: We treated 21 consecutive children presenting with presumed acute myocarditis with IVIG, 2 g/kg, over 24 hours, in addition to anticongestive therapies. A comparison group comprised 25 recent historical control patients meeting identical eligibility criteria but not receiving IVIG therapy. Left ventricular function was assessed during five time intervals: 0 to 7 days, 1 to 3 weeks, 3 weeks to 3 months, 3 to 6 months, and 6 to 12 months. At presentation, the IVIG and non-IVIG groups had comparable left ventricular enlargement and poor fractional shortening. Compared with the non-IVIG group, those treated with IVIG had a smaller mean adjusted left ventricular end-diastolic dimension and higher fractional shortening in the periods from 3 to 6 months (P = .008 and P = .033, respectively) and 6 to 12 months (P = .072 and P = .029, respectively). When adjusting for age, biopsy status, intravenous inotropic agents, and angiotensin-converting enzyme inhibitors, patients treated with IVIG were more likely to achieve normal left ventricular function during the first year after presentation (P = .03). By 1 year after presentation, the probability of survival tended to be higher among IVIG-treated patients (.84 versus .60, P = .069). We observed no adverse effects of IVIG administration. CONCLUSIONS: These data suggest that use of high-dose IVIG for treatment of acute myocarditis is associated with improved recovery of left ventricular function and with a tendency to better survival during the first year after presentation.

Acute Disease↗
PubMed1994

Regional cerebral perfusion abnormalities after cardiac operations. Single photon emission computed tomography (SPECT) findings in children with postoperative movement disorders.

Despite the clinical and pathologic indicators implicating injury to the basal ganglia in children with hyperkinetic movement disorders, we were previously unable to identify lesions in these structures by means of cranial computed tomography or magnetic resonance imaging. We evaluated regional cerebral perfusion measured by single photon emission computed tomography (SPECT) with technetium 99m hexamethyl propylene amine oxime as a technique to localize functional cerebral abnormalities in eleven children who had a movement disorder after hypothermic cardiac surgery. Perfusion defects of the deep gray matter were noted in six of these eleven patients and cortical perfusion defects in nine. For both cortical and subcortical defects a strong right-sided predilection was present. Our findings suggest functional brain injury not detectable by conventional cranial computed tomography and magnetic resonance imaging in these patients. We speculate that these perfusion defects might relate to the behavioral and developmental sequelae in survivors of this syndrome. SPECT may identify subclinical injury in patients at risk for future neurodevelopmental problems and contribute to our understanding of the mechanisms of cerebral injury in the patient operated on for cardiac disease.

Brain↗
PubMed1993

A comparison of the perioperative neurologic effects of hypothermic circulatory arrest versus low-flow cardiopulmonary bypass in infant heart surgery.

BACKGROUND: Hypothermic circulatory arrest is a widely used support technique during heart surgery in infants, but its effects on neurologic outcome have been controversial. An alternative method, low-flow cardiopulmonary bypass, maintains continuous cerebral circulation but may increase exposure to known pump-related sources of brain injury, such as embolism or inadequate cerebral perfusion. METHODS: We compared the incidence of perioperative brain injury after deep hypothermia and support consisting predominantly of total circulatory arrest with the incidence after deep hypothermia and support consisting predominantly of low-flow cardiopulmonary bypass in a randomized, single-center trial. The criteria for eligibility included a diagnosis of transposition of the great arteries with an intact ventricular septum or a ventricular septal defect and a planned arterial-switch operation before the age of three months. RESULTS: Of 171 patients with D-transposition of the great arteries, 129 (66 of whom were assigned to circulatory arrest and 63 to low-flow bypass) had an intact ventricular septum, and 42 (21 assigned to circulatory arrest and 21 to low-flow bypass) had a ventricular septal defect. After adjustment for diagnosis, assignment to circulatory arrest as compared with low-flow bypass was associated with a higher risk of clinical seizures (odds ratio, 11.4; 95 percent confidence interval, 1.4 to 93.0), a tendency to a higher risk of ictal activity on continuous electroencephalographic (EEG) monitoring during the first 48 hours after surgery (odds ratio, 2.5; 95 percent confidence interval, 1.0 to 6.4), a longer recovery time to the first reappearance of EEG activity (only in the group with an intact ventricular septum, P < 0.001), and greater release of the brain isoenzyme of creatine kinase in the first 6 hours after surgery (P = 0.046). Analyses comparing durations of circulatory arrest produced results similar to those of analyses comparing treatments. CONCLUSIONS: In heart surgery in infants, a strategy consisting predominantly of circulatory arrest is associated with greater central nervous system perturbation in the early postoperative period than a strategy consisting predominantly of low-flow cardiopulmonary bypass. Assessment of the effect of these findings on later outcomes awaits follow-up of this cohort.

Brain Ischemia↗
PubMed1993

Real-time gas-exchange measurement of oxygen consumption in neonates and infants after cardiac surgery.

OBJECTIVES: The purposes of this study were: a) to measure oxygen consumption (VO2) in ventilated neonates and infants after cardiac surgery, utilizing a real-time gas exchange system; and b) to assess this new method by comparing the measured VO2 with calculated VO2 (using the Fick equation and simultaneously determined thermodilution cardiac output, measured hemoglobin, and measured mixed venous and arterial saturations). DESIGN: Prospective, comparison study. Comparison of measured VO2 and calculated VO2 using correlation coefficient, linear regression analysis, and bias and precision. SETTING: Cardiac intensive care unit in a children's hospital. PATIENTS: A total of 60 direct comparisons were made between measured and calculated VO2 in 15 patients (ages ranging from 4 days to 14.1 months with median age of 2.4 months) who were receiving mechanical ventilation after undergoing corrective cardiac surgery. INTERVENTIONS: a) Direct measurement of VO2 using gas exchange method involving a pneumotachograph and a gas sampling system; b) determination of cardiac output by the thermodilution technique; c) measurement of arterial and mixed venous oxygen content by blood sampling. MEASUREMENTS AND RESULTS: The absolute measured VO2 ranged from 19 to 154 mL/min with a mean of 52 +/- 32 mL/min (when indexed, the range was 81 to 367 mL/min/m2 with mean 185 +/- 69 mL/min/m2, or range 4.7 to 18.8 mL/min/kg with mean 10.4 +/- 3.3 mL/min/kg). While 34 (57%) of 60 measured VO2 values were within 10% of their respective calculated VO2 values, 58 (97%) of 60 were within 25%; the mean percent difference between measured and calculated VO2 values was 10.6 +/- 7.7%. In comparing the measured VO2 and calculated VO2, the correlation coefficient was good (r2 = .87; p < .01) and the linear regression equation was: measured VO2 = 1.1 x calculated VO2 -9.0 mL/min/m2. The mean difference, or bias, was 0 mL/min/m2 with precision of 26 and 52 mL/min/m2 (at 1 and 2 SD). As an alternative means of examining the measured VO2 data, we also directly compared the thermodilution cardiac output with cardiac output derived by using the measured VO2 and the Fick equation. The range of Fick-derived cardiac output was between 1.69 to 8.11 L/min/m2 (mean 3.72 +/- 1.56) and the range of thermodilution cardiac output was between 1.75 to 7.42 L/min/m2 (mean 3.71 +/- 1.36). The correlation coefficient between thermodilution cardiac output and Fick-derived cardiac output was good with r2 = .88 (p < .01) and the linear regression equation was: thermodilution cardiac output = 0.81 x Fick-derived cardiac output + 0.71 L/min/m2. The bias was -0.01 L/min/m2 with a precision of 0.54 L/min/m2 at 1 SD (or 1.08 L/min/m2 for 2 SD). CONCLUSIONS: Measured VO2 using a gas-exchange system compared favorably with calculated VO2 values using the Fick equation and simultaneously obtained thermodilution cardiac output and arterial and venous oxygen concentrations. By employing this breath-by-breath gas-exchange system, real-time VO2 measurement in ventilated neonates and infants is now feasible.

Bias↗