Does anesthesia duration or number of cases per patient predict safety events?

BACKGROUND

The need for dental rehabilitation under general anesthesia is increasing, with varying needs between patients. Mortality has been found to be a rare event in these patients; however other perioperative events can and do occur. Previous studies have established increased incidence of perioperative events with younger, sicker children, and longer anesthetics, however, no studies to date have evaluated if the incidence of perioperative events is more closely associated with one long anesthetic or multiple anesthetics per patient.

AIMS

To evaluate the association of perioperative events related to single anesthetic duration or number of anesthetics per patient for dental rehabilitation.

METHODS

After Children's Wisconsin Human Research Protection Program determined this quality activity did not meet the definition of human subjects research, we performed an epidemiologic observational evaluation by extracting all dental related cases (dental alone or with oral surgeon vs. dental with other specialties) with an associated general anesthesia encounter from Children's Wisconsin electronic data warehouse from June 1, 2015 to December 31, 2021. These cases occurred at a free-standing children's hospital or associated pediatric-only ambulatory surgery center. The risk of perioperative safety events was analyzed for previously identified risk groups such as American Society of Anesthesiologists Physical Status (ASA-PS), patient age, anesthesia case time with the addition of number of dental cases per patient.

RESULTS

In this study, 8468 procedures were performed on 8082 patients. Of this cohort, 7765 patients underwent one procedure for dental care while 317 patients underwent a total of 703 dental-related procedures, ranging from two to five procedures per patient. Multivariable logistic regression identified increased risk of perioperative events in patients with ASA-PS 3 (n = 1459, rate 1.78%, p value .001, OR 5.7, CI 2.1-15.5) and ASA-PS 4 (n = 86, rate 5.8%, p < .001, OR 17.2, CI 4.4-67.3), anesthesia duration (p < .001, OR 1.46, CI 1.21-1.76), but no increased risk with number of anesthetics per patient (p value .54, OR 0.81, CI 0.4-1.61).

CONCLUSIONS

Limiting dental care under general anesthesia to multiple short cases may decrease the risk of perioperative events when compared to completing all treatment in one long operative session.

Transabdominal Intrapericardial Approach in Liver Transplantation for Unresectable Primary Hepatic Functioning Paraganglioma With Invasion Into Hepatic Veins and Suprahepatic Vena Cava: A Surgical and Anesthesia Management Challenge

Primary hepatic functional paraganglioma is a rare form of extra-adrenal catecholamine-secreting tumor. Definitive treatment of functioning paraganglioma is challenging because of the critical location of the tumor frequently in close proximity to vital structures and risk of excessive catecholamine release during operative manipulation. We report the multidisciplinary management approach for a case of unresectable primary hepatic functional paraganglioma with invasion into the hepatic veins and suprahepatic vena cava. To our knowledge, this is the first report showing that orthotopic liver transplantation is curative for patients with unresectable primary hepatic paraganglioma. For locally advanced unresectable hepatic paraganglioma that involves the intrapericardial vena cava, a meticulous pre- and intraoperative medical management and transabdominal intrapericardial vascular control of the suprahepatic vena cava during orthotopic liver transplantation allows for complete extirpation of the tumor and achieves optimal outcome.

Home surveillance program prevents interstage mortality after the Norwood procedure

OBJECTIVE

To determine whether early identification of physiologic variances associated with interstage death would reduce mortality, we developed a home surveillance program.

METHODS

Patients discharged before initiation of home surveillance (group A, n = 63) were compared with patients discharged with an infant scale and pulse oximeter (group B, n = 24). Parents maintained a daily log of weight and arterial oxygen saturation according to pulse oximetry and were instructed to contact their physician in case of an arterial oxygen saturation less than 70% according to pulse oximetry, an acute weight loss of more than 30 g in 24 hours, or failure to gain at least 20 g during a 3-day period.

RESULTS

Interstage mortality among infants surviving to discharge was 15.8% (n = 9/57) in group A and 0% (n = 0/24) in group B (P =.039). Surveillance criteria were breached for 13 of 24 group B patients: 12 patients with decreased arterial oxygen saturation according to pulse oximetry with or without poor weight gain and 1 patient with poor weight gain alone. These 13 patients underwent bidirectional superior cavopulmonary connection (stage 2 palliation) at an earlier age, 3.7 +/- 1.1 months of age versus 5.2 +/- 2.0 months for patients with an uncomplicated interstage course (P =.028). A growth curve was generated and showed reduced growth velocity between 4 and 5 months of age, with a plateau in growth beyond 5 months of age.

CONCLUSION

Daily home surveillance of arterial oxygen saturation according to pulse oximetry and weight selected patients at increased risk of interstage death, permitting timely intervention, primarily with early stage 2 palliation, and was associated with improved interstage survival. Diminished growth identified 4 to 5 months after the Norwood procedure brings into question the value of delaying stage 2 palliation beyond 5 months of age.

L-arginine infusion lowers blood pressure in children

Eleven children were studied during L-arginine infusion. Blood pressure decreased, and mean plasma L-arginine and L-citrulline increased compared with baseline levels. The change in blood pressure was inversely related to the change in plasma L-citrulline. These results suggest that L-arginine decreased blood pressure via increased nitric oxide production.

Two-Week (Ten-Day) Inhalation Toxicity and Two-Week Recovery Study of Phenol Vapor in the Rat

The toxicity of phenol vapor was evaluated in male and female Fischer 344 rats (20/sex/group) via flow-past nose-only inhalation exposure. The test animals were exposed to target concentrations of 0 (air control), 0.5, 5.0, or 25 parts per million (ppm) of phenol in air for 6 hours/day, 5 days/week, for 2 weeks. High pressure liquid chromatography (HPLC) measurement of phenol test atmospheres determined mean (+/- standard deviation) analytical concentrations of 0.0 +/- 0.0, 0.52 +/- 0.078, 4.9 +/- 0.57, and 25 +/- 2.2 ppm, respectively. After 2 weeks of exposure, 10 test animals/sex/group were sampled for clinical chemistry and hematology parameters, and then sacrificed. Histopathological examination included the nasopharyngeal tissues, larynx, trachea, lungs with mainstem bronchi, kidney, liver, and spleen. The remaining 10 animals/sex/group were retained for a 2-week recovery period. Recovery groups of animals were evaluated as described previously and then sacrificed. No signs of toxicity in clinical observations (including overt neurological signs), body weights, food consumption, clinical pathology, organ weights, macroscopic pathology or microscopic pathology were seen during the exposures or at either sacrifice interval. In conclusion, 2-week inhalation exposures to phenol vapor at concentrations up to and including 25 ppm did not produce any adverse effects.

Two-week (ten-day) inhalation toxicity and two-week recovery study of phenol vapor in the rat

The toxicity of phenol vapor was evaluated in male and female Fischer 344 rats (20/sex/group) via flow-past nose-only inhalation exposure. The test animals were exposed to target concentrations of 0 (air control), 0.5, 5.0, or 25 parts per million (ppm) of phenol in air for 6 hours/day, 5 days/week, for 2 weeks. High pressure liquid chromatography (HPLC) measurement of phenol test atmospheres determined mean (+/- standard deviation) analytical concentrations of 0.0 +/- 0.0, 0.52 +/- 0.078, 4.9 +/- 0.57, and 25 +/- 2.2 ppm, respectively. After 2 weeks of exposure, 10 test animals/sex/group were sampled for clinical chemistry and hematology parameters, and then sacrificed. Histopathological examination included the nasopharyngeal tissues, larynx, trachea, lungs with mainstem bronchi, kidney, liver, and spleen. The remaining 10 animals/sex/group were retained for a 2-week recovery period. Recovery groups of animals were evaluated as described previously and then sacrificed. No signs of toxicity in clinical observations (including overt neurological signs), body weights, food consumption, clinical pathology, organ weights, macroscopic pathology or microscopic pathology were seen during the exposures or at either sacrifice interval. In conclusion, 2-week inhalation exposures to phenol vapor at concentrations up to and including 25 ppm did not produce any adverse effects.

Venous saturation and the anaerobic threshold in neonates after the Norwood procedure for hypoplastic left heart syndrome

BACKGROUND

Reduction in oxygen delivery can lead to organ dysfunction and death by cellular hypoxia, detectable by progressive (mixed) venous oxyhemoglobin desaturation until extraction is limited at the anaerobic threshold. We sought to determine the critical level of venous oxygen saturation to maintain aerobic metabolism in neonates after the Norwood procedure (NP) for the hypoplastic left heart syndrome (HLHS).

METHODS

A prospective perioperative database was maintained for demographic, hemodynamic, and laboratory data. Invasive arterial and atrial pressures, arterial saturation, oximetric superior vena cava (SVC) saturation, and end-tidal CO2 were continuously recorded and logged hourly for the first 48 postoperative hours. Arterial and venous blood gases and cooximetry were obtained at clinically appropriate intervals. SVC saturation was used as an approximation of mixed venous saturation (SvO2). A standard base excess (BE) less than -4 mEq/L (BElo), or a change exceeding -2 mEq/L/h (deltaBElo), were used as indicators of anaerobic metabolism. The relationship between SvO2 and BE was tested by analysis of variance and covariance for repeated measures; the binomial risk of BElo or deltaBElo at SvO2 strata was tested by the likelihood ratio test and logistic regression, with cutoff at p < 0.05.

RESULTS

Complete data were available in 48 of 51 consecutive patients undergoing NP yielding 2,074 valid separate determinations. BE was strongly related to SvO2 (model R2 = 0.40, p < 0.0001) with minimal change after adjustment for physiologic covariates. The risk of anaerobic metabolism was 4.8% overall, but rose to 29% when SvO2 was 30% or below (p < 0.0001). Survival was 100% at 1 week and 94% at hospital discharge.

CONCLUSIONS

Analysis of acid-base changes revealed an apparent anaerobic threshold when SvO2 fell below 30%. Clinical management to maintain SvO2 above this threshold yielded low mortality.

Patients at risk for low systemic oxygen delivery after the Norwood procedure

BACKGROUND

Identification of patients at risk for inadequate systemic oxygen delivery following the Norwood procedure could allow for application of more intensive monitoring, provide for earlier intervention of decreased cardiac output, and result in improved outcome.

METHODS AND RESULTS

Superior vena cava saturation (SvO2) and arteriovenous oxygen content difference were prospectively monitored as indicators of systemic oxygen delivery and recorded hourly for the first 48 hours in 29 of 33 consecutive patients following the Norwood procedure. Risk factors were evaluated using multiple linear regression to determine their impact on SvO2 and arteriovenous oxygen content difference. Age less than 8 days, weight less than 2.5 kg, aortic atresia, and prolonged cardiopulmonary bypass time were risk factors for low SvO2 and wide arteriovenous oxygen content difference (p < 0.05). Phenoxybenzamine and increasing time after operation were associated with higher SvO2 and narrower arteriovenous oxygen content difference (p < 0.05). Thirty-day survival was 97% and hospital survival was 94%. The earliest death occurred on postoperative day 20. Survival to bidirectional cavopulmonary shunt was 77%. Preoperative mechanical ventilation was the only risk factor identified for late death.

CONCLUSIONS

Aortic atresia, low weight, younger age, and prolonged cardiopulmonary bypass, previously identified risk factors for mortality, were associated with decreased SvO2 and narrower arteriovenous oxygen content difference in the early postoperative period. The impact of this hemodynamic vulnerability on mortality was minimized by continuous SvO2 monitoring.

Pulmonary vascular responses during acute and sustained respiratory alkalosis or acidosis in intact newborn piglets

Acute alkalosis-induced pulmonary vasodilation and acidosis-induced pulmonary vasoconstriction have been well described, but responses were generally measured within 5-30 min of changing pH. In contrast, several in vitro studies have found that relatively brief periods of sustained alkalosis can enhance, and sustained acidosis can decrease, vascular reactivity. In this study of intact newborn piglets, effects of acute (20 min) and sustained (60-80 min) alkalosis or acidosis on baseline (35% O2) and hypoxic (12% O2) pulmonary vascular resistance (PVR) were compared with control piglets exposed only to eucapnia. Acute alkalosis decreased hypoxic PVR, but sustained alkalosis failed to attenuate either baseline PVR or the subsequent hypoxic response. Acute acidosis did not significantly increase hypoxic PVR, but sustained acidosis markedly increased both baseline PVR and the subsequent hypoxic response. Baseline PVR was similar in all piglets after resumption of eucapnic ventilation, but the final hypoxic response was greater in piglets previously exposed to alkalosis than in controls. Thus, hypoxic pulmonary vasoconstriction was not attenuated during sustained alkalosis, but was accentuated during sustained acidosis and after the resumption of eucapnia in alkalosis-treated piglets. Although extrapolation of data from normal piglets to infants and children with pulmonary hypertension must be done with caution, this study suggests that sustained alkalosis may be of limited efficacy in treating acute hypoxia-induced pulmonary hypertension and the risks of pulmonary hypertension must be considered when using ventilator strategies resulting in permissive hypercapnic acidosis.

Dose-dependent metabolism of fluoromethyl-2,2-difluoro-1-(trifluoromethyl)vinyl ether (compound A), an anesthetic degradation product, to mercapturic acids and 3,3,3-trifluoro-2-(fluoromethoxy)propanoic acid in rats

The volatile anesthetic sevoflurane is degraded in anesthesia machines to fluoromethyl-2,2-difluoro-1-(trifluoromethyl)vinyl ether (FDVE), to which humans are exposed. FDVE is metabolized in rats and humans to two alkane and two alkene glutathione S-conjugates that are hydrolyzed to the corresponding cysteine S-conjugates. The latter are N-acetylated to mercapturic acids, or bioactivated by renal cysteine conjugate beta-lyase to metabolites which may react with cellular macromolecules or hydrolyze to 3,3,3-trifluoro-2-(fluoromethoxy)propanoic acid. FDVE causes nephrotoxicity in rats, which evidence suggests is mediated by renal uptake of FDVE S-conjugates and metabolism by beta-lyase. Although pathways of FDVE metabolism have been described qualitatively, the purpose of this investigation was to quantify FDVE metabolism via mercapturic acid and beta-lyase pathways. Fischer 344 rats underwent 3-h nose-only exposure to FDVE (0 +/- 0, 46 +/- 19, 98 +/- 7, 150 +/- 29, and 220 +/- 40 ppm), and urine was collected for 24 h. Urine concentrations of the mercapturates, N-acetyl-S-(1,1,3,3, 3-pentafluoro-2-fluoromethoxypropyl)-L-cysteine and N-acetyl-S-(1-fluoro-2-fluoromethoxy-2-(trifluoromethyl)vinyl)-L- cysteine, the beta-lyase-dependent metabolite 3,3, 3-trifluoro-2-(fluoromethoxy)propanoic acid, and its degradation product trifluorolactic acid, were determined by GC/MS. There was dose-dependent urinary excretion of the alkane mercapturate N-acetyl-S-(1,1,3,3,3-pentafluoro-2-fluoromethoxypropyl)-L- cysteine and 3,3,3-trifluoro-2-(fluoromethoxy)propanoic acid, while excretion of the alkene mercapturate N-acetyl-S-(1-fluoro-2-fluoromethoxy-2-(trifluoromethyl)vinyl)-L- cysteine plateaued at higher FDVE exposures. The alkane:alkene mercapturic acid excretion ratio was between 2:1 and 4:1. Trifluorolactic acid was only rarely observed. Urine excretion of the beta-lyase-dependent metabolite 3,3, 3-trifluoro-2-(fluoromethoxy)propanoic acid was 10-fold greater than that of the combined mercapturates. Results show that FDVE cysteine S-conjugates undergo facile metabolism via renal beta-lyase, particularly in comparison with detoxication by mercapturic acid formation. The quantitative assay developed herein may provide a biomarker for FDVE exposure and relative metabolism via toxification and detoxifying pathways, applicable to animal and human investigations.

Unmeasured anions identified by the Fencl-Stewart method predict mortality better than base excess, anion gap, and lactate in patients in the pediatric intensive care unit

OBJECTIVES

This study was undertaken to compare three methods for the identification of unmeasured anions in pediatric patients with critical illness. We compared the base excess (BE) and anion gap (AG) methods with the less commonly used Fencl-Stewart strong ion method of calculating BE caused by unmeasured anions (BEua). We measured the relationship of unmeasured anions identified by the three methods to serum lactate concentrations and to mortality.

DESIGN

Retrospective cohort study.

SETTING

Tertiary care pediatric intensive care unit in an academic pediatric hospital.

PATIENTS

The study population included 255 patients in the pediatric intensive care unit who had simultaneous measurements of arterial blood gases, electrolytes, and albumin during the period of July 1995 to December 1996. Sixty-six of the 255 patients had a simultaneous measurement of serum lactate.

MEASUREMENTS AND MAIN RESULTS

The BEua was calculated using the Fencl-Stewart method. The AG was defined as (sodium plus potassium) - (chloride plus total carbon dioxide). BE was calculated from the standard bicarbonate, which is derived from the Henderson-Hasselbalch equation and reported on the blood gas analysis. A BE or BEua value of < or =-5 mEq/L or an AG > or =17 mEq/L was defined as a clinically significant presence of unmeasured anions. A lactate level of > or =45 mg/dL was defined as being abnormally elevated for this study. The presence of unmeasured anions identified by significantly abnormal BEua was poorly identified by BE or AG. Of the 255 patients included in the study, 67 (26%) had a different interpretation of acid base balance when the Fencl method was used compared with when BE and AG were used. Plasma lactate concentration correlated better with BEua (r2 = .55; p = .0001) than with AG (r2 = .41; p = .0005) or BE (r2 = .27; p = .025). Mortality was more strongly related to BEua < or =-5 mEq/L (relative risk of death = 10.25; p = .002) than to lactate > or =45 mg/dL (relative risk of death = 2.35; p = .04). In logistic regression analysis, mortality was more strongly associated with BEua (area under the receiver operating characteristic curve = 0.79; p = .0002) than lactate (receiver operating characteristic curve area = 0.63; p = .05), BE (receiver operating characteristic curve area = 0.53; p = .32), or AG (receiver operating characteristic curve area = 0.64; p = .08) in this patient sample.

CONCLUSIONS

Critically ill patients with normal BE and normal AG frequently have elevated unmeasured anions detectable by BEua. The Fencl-Stewart method is better than BE and similar to AG in identifying patients with high lactate levels. Elevated unmeasured anions identified by the Fencl-Stewart method were more strongly associated with mortality than with BE, AG, or lactate in this patient sample.

Phenoxybenzamine improves systemic oxygen delivery after the Norwood procedure

BACKGROUND

Achieving adequate systemic oxygen delivery after the Norwood procedure frequently is complicated by excessive pulmonary blood flow at the expense of systemic blood. We hypothesized that phenoxybenzamine could achieve a balanced circulation through reduction of systemic vascular resistance.

METHODS

In this prospective, nonrandomized study, oximetric catheters were placed in the superior vena cava for continuous monitoring of systemic venous oxygen saturation. Postoperative hemodynamic variables were compared between 7 control patients and 8 patients who received phenoxybenzamine.

RESULTS

The hospital survival rate was 93% (14 of 15 patients). Improvements in postoperative hemodynamics in the phenoxybenzamine group included a higher systemic venous oxygen saturation, a narrower arteriovenous oxygen content difference, a lower ratio of pulmonary to systemic flow, and a lower indexed systemic vascular resistance. In the phenoxybenzamine group, mean arterial blood pressure was related directly to systemic oxygen delivery, in contrast to the control group, where mean arterial pressure was related directly to indexed systemic vascular resistance and the ratio of pulmonary to systemic circulation.

CONCLUSIONS

Continuous postoperative monitoring of systemic venous oxygen saturation in a patient who has undergone the Norwood procedure provides early identification of low systemic oxygen delivery and an elevated ratio of pulmonary to systemic circulation. In this pilot study, phenoxybenzamine appeared to improve systemic oxygen delivery during the early postoperative period after the Norwood procedure. Further studies are indicated to confirm these results.

Subchronic inhalation toxicity study of caprolactam (with a 4-week recovery) in the rat via whole-body exposures

This study was designed to assess the potential subchronic inhalation toxicity of caprolactam when administered as a 3-micron aerosol from an aqueous solution to Sprague-Dawley CD rats (10/sex/group) via whole-body exposure. The study was enhanced with the inclusion of motor activity measurements and a functional observational battery to assess the neurotoxic potential of caprolactam. The rats were exposed at least 65 times over a 13-week period for 6 h per day, 5 days per week, to target concentrations (3 microns, mass median aerodynamic diameter) of 0, 25, 75, and 250 milligrams per cubic meter (mg/m3). An additional 10 animals/sex/group were similarly exposed and then held for a 4-week recovery period. Exposure levels were determined gravimetrically six times daily; one daily sample was analyzed by high-pressure liquid chromatography. No deaths were observed in the study during the exposure or recovery periods. Treatment-related responses such as labored breathing and nasal discharge were seen during many of the exposures. Similar responses as well as moist rales were seen during the nonexposure periods during the 13 weeks of exposure. However, these responses abated during the 4-week recovery period. There were no clearly treatment-related responses observed with ophthalmoscopic examinations, body weight measurements, food consumption measurements, neurobehavioral evaluations, clinical pathology evaluations, organ weight measurements, or macroscopic pathology examinations. Microscopic findings that were considered related to exposure to the test material were seen in the nasoturbinal tissues (hypertrophy/hyperplasia of goblet cells in the respiratory mucosa and intracytoplasmic eosinophilic material in epithelial cells of the olfactory mucosa) of the two higher-exposure group animals and in the laryngeal tissues (squamous/squamoid metaplasia/hyperplasia of the pseudostratified columnar epithelium covering the ventral seromucous gland) of all three exposure group animals. These changes were considered to be adaptive responses to an irritant (caprolactam). The keratinization of the metaplastic epithelium in the larynx was considered to be an adverse effect. By the end of the 4-week recovery period, there was complete regression of the keratinization in the larynx, but recovery of the adaptive nasoturbinal effects had not completely resolved. In conclusion, the whole-body exposure of Sprague-Dawley rats to caprolactam as a respirable aerosol for 6 h/day, 5 days/week, for 13 weeks at gravimetrically determined levels of 24, 70, and 243 mg/m3 resulted in respiratory tract effects (laryngeal) at the highest exposure level with complete recovery within 4 weeks postexposure. The results indicate that the no-observed-adverse-effect level for caprolactam is 70 mg/m3, based on upper respiratory effects, with 243 mg/m3 representing a no-observed-effect level for systemic toxicity, neurotoxicity, and lower respiratory tract effects.

Role of the renal cysteine conjugate beta-lyase pathway in inhaled compound A nephrotoxicity in rats

BACKGROUND

The sevoflurane degradation product compound A is nephrotoxic in rats and undergoes metabolism to glutathione and cysteine S-conjugates, with further metabolism by renal cysteine conjugate beta-lyase to reactive intermediates. Evidence suggests that toxicity is mediated by renal uptake of compound A S-conjugates and metabolism by beta-lyase. Previously, inhibitors of the beta-lyase pathway (aminooxyacetic acid and probenecid) diminished the nephrotoxicity of intraperitoneal compound A. This investigation determined inhibitor effects on the toxicity of inhaled compound A.

METHODS

Fischer 344 rats underwent 3 h of nose-only exposure to compound A (0-220 ppm in initial dose-response experiments and 100-109 ppm in subsequent inhibitor experiments). The inhibitors (and targets) were probenecid (renal organic anion transport mediating S-conjugate uptake), acivicin (gamma-glutamyl transferase), aminooxyacetic acid (renal beta-lyase), and aminobenzotriazole (cytochrome P450). Urine was collected for 24 h, and the animals were killed. Nephrotoxicity was assessed by histology and biochemical markers (serum BUN and creatinine; urine volume; and excretion of protein, glucose, and alpha-glutathione-S-transferase, a predominantly proximal tubular cell protein).

RESULTS

Compound A caused dose-related proximal tubular cell necrosis, diuresis, proteinuria, glucosuria, and increased alpha-glutathione-S-transferase excretion. The threshold for toxicity was 98-109 ppm (294-327 ppm-h). Probenecid diminished (P < 0.05) compound A-induced glucosuria and excretion of alpha-glutathione-S-transferase and completely prevented necrosis. Aminooxyacetic acid diminished compound A-dependent proteinuria and glucosuria but did not decrease necrosis. Acivicin increased nephrotoxicity of compound A, and aminobenzotriazole had no consistent effect on nephrotoxicity of compound A.

CONCLUSIONS

Nephrotoxicity of inhaled compound A in rats was associated with renal uptake of compound A S-conjugates and cysteine conjugates metabolism by renal beta-lyase. Manipulation of the beta-lyase pathway elicited similar results, whether compound A was administered by inhalation or intraperitoneal injection. Route of administration does not apparently influence nephrotoxicity of compound A in rats.

The use of inhaled nitric oxide in a wide variety of clinical problems

Inhaled nitric oxide (NO) clearly decreased pulmonary vascular resistance in pediatric patients with pulmonary hypertension, regardless of the underlying origin of the pulmonary hypertension. In persistent pulmonary hypertension of the neonate (PPHN) and CHD, the use of inhaled NO appears to improve the outcome of these patients. In acute respiratory distress syndrome (ARDS) and surfactant deficiency the role of inhaled NO therapy remains unclear. The use of inhaled NO is safe in a carefully monitored setting with a delivery system designed to minimize the generation of NO2.

Inhaled nitric oxide reduces the utilization of extracorporeal membrane oxygenation in persistent pulmonary hypertension of the newborn

OBJECTIVE

To determine if the use of inhaled nitric oxide therapy reduces the need for extracorporeal membrane oxygenation (ECMO) in persistent pulmonary hypertension of the newborn.

DESIGN

A matched cohort study with retrospective data extraction.

SETTING

Pediatric and neonatal intensive care units at a medical school-affiliated children's hospital serving as a regional referral center for respiratory failure.

PATIENTS

Records of all neonates transferred for rescue therapy for persistent pulmonary hypertension during the study period were analyzed, with inclusion in the study based on defined gas exchange parameters, and with exclusion from the study based on the presence of congenital heart disease, diaphragmatic hernia, or lethal chromosomal abnormality. Assignment to cohorts was based on availability of inhaled nitric oxide therapy: group 1 patients were admitted when inhaled nitric oxide was unavailable; group 2 patients were admitted when inhaled nitric oxide was available.

INTERVENTIONS

Standard criteria (alveolar-arterial oxygen tension gradient of > 600 torr [> 80 kPa], or oxygenation index of > 40) were used to trigger initial evaluation for ECMO when these criteria were met for 2 hrs, and ECMO was initiated if these criteria continued to be met for 12 hrs, or if cardiovascular instability occurred. Ventilator management in all patients was directed to improve arterial oxygenation, such that ECMO criteria were no longer met. Patients in group 2 only were treated with inhaled nitric oxide after meeting ECMO evaluation criteria, and they continued to receive inhaled nitric oxide if a quantifiable improvement in gas exchange occurred.

MEASUREMENTS AND MAIN RESULTS

Fifty patients qualified for inclusion in the analysis (29 patients in group 1, and 21 patients in group 2). In group 1, 21 (72%) patients met ECMO criteria, and 16 (76%) patients required ECMO therapy. In group 2, 16 (76%) patients met ECMO criteria, 15 patients received inhaled nitric oxide therapy, and only four (25%) patients required ECMO therapy (p = .003 compared with group 1). Treatment with inhaled nitric oxide resulted in an initial increase in PaO2, without adverse effects, in all of the treated patients. The reduction in ECMO utilization in group 2 was achieved with a higher rate of complication-free survival (survival without oxygen, requirement at 28 days, p = .018; survival without intracranial hemorrhage, p = .048), and a lower hospital cost per survivor (p = .021), compared with group 1 patients.

CONCLUSION

In neonates with persistent pulmonary hypertension, therapy with inhaled nitric oxide reliably and safely improves oxygenation, thereby resulting in a decreased need for ECMO therapy, improved patient outcome, and lower hospital costs.

Epidural analgesia improves outcome following pediatric fundoplication. A retrospective analysis

BACKGROUND AND OBJECTIVES

Nissen fundoplication is a common procedure in high-risk pediatric patients. This cohort study evaluated the influence of epidural versus intravenous opioid analgesia on the postoperative course of infants and children undergoing fundoplication.

METHODS

A retrospective review was made of the perioperative courses of 155 consecutive patients, aged 1 month to 19 years, who underwent elective open fundoplication from January 1993 to October 1994. Of these 155 patients, 72 received perioperative analgesia with epidural opioids, while 83 received parenteral opioids. Outcome variables included major morbidity factors, recovery of bowel and bladder function, and economic impact.

RESULTS

Patients in the epidural and parenteral groups did not differ with respect to age, weight, or associated preoperative medical diagnoses. The postoperative complication rate was significantly decreased in the epidural group (5.5% versus 20%) (P < .001). In the epidural group 4 patients required mechanical ventilation for longer than 24 hours, compared with 15 in the parenteral group. Patients in the epidural group were discharged earlier from the hospital and incurred approximately 20% less in hospital charges on average than their cohorts in the intravenous group.

CONCLUSIONS

These findings suggest that perioperative epidural analgesia, administered by a dedicated pain service, amy improve outcome in high-risk pediatric patients undergoing fundoplication.

Inhalation toxicity study of a haloalkene degradant of sevoflurane, Compound A (PIFE), in Sprague-Dawley rats

BACKGROUND

Under certain circumstances in the clinical setting, contact of the anesthetic sevoflurane with a CO2 absorbent (e.g., soda lime, Baralyme) leads to the formation of a degradant designated as pentafluoroisopropenyl fluoromethyl ether (PIFE; Compound A). Previous studies have shown that the kidney is the primary target organ for toxicity in the rat. This study was designed to determine the impact of PIFE on rat renal histology correlated with functional changes. The findings are discussed in terms of probable mechanism of action and relevance to humans.

METHODS

Male and female Sprague-Dawley rats were exposed to 0, 30, 61, 114, or 202 ppm PIFE for a single 3-h period via nose-only inhalation. Rats were observed daily for behavioral changes or external physical signs of toxicity (i.e., lacrimation, dyspnea, piloerection, etc.) and body weights were recorded at 6, 4, and 1 day preexposure and 1, 3, 7, and 13 days postexposure. Animals were evaluated for hematologic, clinical chemistry and/or urinalysis changes immediately postexposure and/or at 1, 4, and 14 days postexposure. Rats were killed, subjected to a macroscopic postmortem examination, and evaluated for histopathologic changes in all major tissues and organs at 1, 4, and 14 days postexposure.

RESULTS

Labored breathing was observed in 3 of the 20 and 2 of the 20 rats in the 114 ppm and 202 ppm groups, respectively, during the 3-h exposure period. No significant reductions in body weight gain were noted during the 2-week study period. Clinical chemistry evaluations revealed increases in blood urea nitrogen and creatinine 1 day postexposure in males and females exposed to 202 ppm PIFE. Changes in urinary glucose, protein and N-acetyl-beta-glucoaminidase/creatinine were evident one day postexposure in males and females exposed to 202 ppm and in males exposed to 114 ppm PIFE. Most values were within normal ranges by 4 or 14 days postexposure. No drug-related alterations in hematologic parameters were noted. Evidence of olfactory epithelial degeneration and desquamation in the nasal turbinates was noted at 4 days postexposure in male and female rats exposed to 202 ppm PIFE. Concentration-dependent renal tubular necrosis and tubular cell hyperplasia, in the corticomedullary border, were observed in males and females exposed to 114 and 202 ppm PIFE. The severity of tubular necrosis in both males and females was considered minimal to slight at the 114 ppm exposure concentration and slight to moderate at the 202 ppm exposure. Both the numbers of affected animals and severity were reduced over time. The most marked changes in serum and urine chemistry were associated with the animals described as having moderate renal necrosis. Male rats appeared more susceptible to nephropathy than female rats. There were no other PIFE-related histopathologic findings.

CONCLUSIONS

The renal histopathologic findings in this study are consistent with those reported in previous acute studies in rats after PIFE administration. Functional changes in the kidney, as evidenced by serum chemistry and urinalyses, were observed at exposure concentrations that induced morphologic alterations.

Validation of a volumeless breath-by-breath method for measurement of respiratory quotient

Measurement of respiratory quotient (RQ) is useful as an indicator of changes in CO2 equilibrium or metabolism. Because of technical difficulties when volumetric or mixed expired methods are applied to clinical practice, we sought to validate a method of volumeless breath-by-breath RQ measurement based on real-time analysis of inspired and alveolar concentrations of O2, CO2, and N2 alone. We derived our volumeless method from a modified three-compartment lung model and tested the validity of the model by comparing it with a standard volumetric open-circuit method. Data from 1,736 breaths from 25 healthy adult volunteers for a total of 78 epochs were collected. Inspired, end-tidal, and mixed expired gas compositions were analyzed by Raman spectroscopy, and RQ values from 0.6 to 2.4 were obtained. Linear regression of the volumeless breath-by-breath method against the open-circuit method yielded a line with a slope of 1.002 (95% confidence interval 0.928 to 1.076) and an intercept of 0.066 (95% confidence interval -0.008 to 0.146) with an R2 of 0.91 (P < 0.001). We analyzed agreement by several methods and used mathematical modeling to predict precision with variations in epoch length and breath volume, which were verified by Monte Carlo techniques. We demonstrated that RQ can be measured reliably and easily using this volumeless breath-by-breath technique.

Ventilatory response to carbon dioxide in term infants after halothane and nitrous oxide anesthesia

The purpose of this study was to determine whether the ventilatory response to CO2 is depressed in term infants after halothane and N2O anesthesia. Ventilatory response to CO2 was determined by using a maskless CO2 response test in which a ventilation ratio is calculated from measurements of transcutaneous PCO2 (PtcCO2). Ventilation ratio represents the fractional increase in ventilation that occurs in response to inspired CO2. Eight infants were studied who were at least 36 wk gestational age and 12 +/- 4 wk postnatal age, did not have apnea in the perioperative period (values are means +/- SD). Ventilation ratio measured with a 4%-inspired-CO2 stimulus increased significantly after anesthesia (3.5 +/- 0.8 vs 3.0 +/- 0.5, P = 0.02). Baseline PtcCO2 was significantly lower after anesthesia than before anesthesia (37 +/- 4 vs 42 +/- 3, P < 0.01) which may reflect the development of a relative metabolic acidosis. (The occurrence of postoperative metabolic acidosis was in fact documented in another group of eight infants.) Ventilatory response to CO2 was not depressed after halothane and nitrous oxide anesthesia in these term and near-term infants.

Diagnostic value of anemia, red blood cell morphology, and reticulocyte count for sickle cell disease

STUDY OBJECTIVE

To determine the diagnostic value of anemia, RBC morphology, and reticulocyte count for differentiating patients with sickle cell trait from those with sickle cell disease, who have acute medical or surgical conditions and a positive sickle cell screen.

DESIGN

Retrospective chart review.

SETTING

A midwest urban children's hospital with 220 beds and 36,000 emergency department visits per year.

PARTICIPANTS

One hundred six patients with sickle cell trait and 152 patients with sickle cell hemoglobinopathies.

RESULTS

Anemia was observed significantly more often in patients with sickle cell disease compared with sickle cell trait (P less than .001) at all ages 3 months and older. However, anemia alone as a diagnostic test lacked high sensitivity and specificity in children less than 4 years old. Sensitivity approached 100% with the presence of anemia, abnormal RBC morphology, or reticulocyte count of more than 2%.

CONCLUSION

Absence of anemia alone does not exclude the diagnosis of sickle cell disease in children less than 4 years old. To differentiate trait from sickle cell disease, we recommend determination of not only hemoglobin adjusted for age but also of RBC morphology and reticulocyte count on all children presenting with acute medical and surgical conditions and a positive sickle cell screen.

Acute inhalation toxicity studies in several animal species of an ethylene oxide/propylene oxide copolymer (UCON 50-HB-5100)

An acute inhalation toxicity study in several species of animals with an ethylene oxide/propylene oxide copolymer (EO/PO) having a molecular weight of 4000 [UCON-50-HB-5100, CAS #9038-95-3] was designed to determine if any species variation could be shown. Species tested included: rats, mice, hamsters, guinea pigs, and dogs. The test material was administered as a respirable liquid aerosol for 4 hours at target concentrations of 50, 100, 200, and 500 mg/m3. A vehicle control group was exposed to a distilled water aerosol. The 4 hours LC50's were calculated to be 147 mg/m3 [rats], 174 mg/m3 [mice], 293 mg/m3 [guinea pigs] and 511 mg/m [hamsters]. The dog LC50 was determined to be greater than 500 mg/m3 since all the test animals survived exposure to this concentration. These values show that rats and mice were the most sensitive species with a declining response in guinea pigs, hamsters and dogs. Lung weights were increased at all exposure concentrations in rats, mice and hamsters. Lung weights were increased in guinea pigs at exposure concentrations of 100 mg/m3 and above. Lung weights in dogs were increased only at the 500 mg/m3 exposure concentration. Significant pathological changes were limited to the lungs and were more common in animals which died prior to scheduled sacrifice. Grossly, these lung changes consisted of red discoloration, edema, emphysema, and surface irregularities. Microscopic findings in the lungs included acute congestion and hemorrhage and, less commonly, acute interstitial inflammation.

Postoperative pain relief in children from the parascalene injection technique

Nineteen pediatric patients aged 6 months to 12 years scheduled for elective upper extremity surgery were randomly assigned to receive either a parascalene block or sham injection. Both groups received a potent inhalational agent for operative anesthesia. At completion of surgery, the treatment group received an injection of 0.5 ml/kg 0.25% bupivacaine with 1:200,000 epinephrine into the brachial plexus via the parascalene approach with the aid of a nerve stimulator; the control group received a subcutaneous needle puncture only. Patients in the parascalene group had superior postoperative analgesia, as evidenced by significantly less opioid requirement in the first 12 postoperative hours and by significantly lower scores on an objective pain scale. We found the parascalene approach to the brachial plexus a simple and reliable analgesic technique in anesthetized children.

Corticosteroids as adjunctive therapy in bacterial meningitis. A meta-analysis of clinical trials

A meta-analysis of all nine available controlled trials of corticosteroids for adjunctive therapy for bacterial meningitis was performed. Risks of various outcomes were assessed for control and treatment groups from each study, and risk differences were determined. For each outcome a weighted average of the individual risk differences was calculated. The results show that corticosteroid administration did not reduce the risk of death or neurologic abnormality at hospital discharge or follow-up examination. Based on statistically combined results of the three most recent trials, there is evidence that dexamethasone reduces the risk of bilateral moderate or more severe hearing loss (risk difference, -9%; 95% confidence limits, -15% and -3%). However, this may be true only for children with meningitis caused by Haemophilus influenzae type b. There are inadequate data in adults or in children with meningitis due to other organisms to demonstrate the benefit of dexamethasone administration. Further study is necessary to fully assess the benefits and risks of corticosteroids for adjunctive therapy for bacterial meningitis.

Survival after chloroquine ingestion in a child

We report the case of a 17 month old, 14 kg male who ingested 4 grams of chloroquine phosphate. He developed ventricular fibrillation and cardiovascular collapse 1 hour after the ingestion. After resuscitation he was treated with diazepam 2 mg/kg acutely, and 0.25 mg/kg/hour for 4 days with no further cardiac electrophysiologic abnormalities. Gallium-67 scan showed increased radionuclide uptake in heart and renal cortex, but there was no clinical evidence of myocardial or renal dysfunction at the time of the scan. He survived with severe neurologic sequelae from the cardiovascular collapse. He had dynamic peripheral neuropathy and progressive loss of retinal function, as evidence of ongoing chloroquine neurotoxicity.

Inhalation toxicity of hexafluoroisobutylene

An acute study of hexafluoroisobutylene (HFIB) determined its 4-hr LC50 in rats to be 1425 ppm. In a 2-week study, all animals exposed to 215 ppm for 4 days died or were sacrificed in extremis, while those exposed to the lowest level tested, 53 ppm, showed respiratory and renal effects. Based on the results of these studies, Fischer-344 rats were exposed 6 hr a day, 5 days a week, for 13 weeks to average HFIB concentrations of 3, 10, 30, and 90 ppm. No animals died due to the HFIB exposures. However, at the highest exposure level tested there were numerous marked signs of systemic toxicity in males and females. At all exposure levels, males were more affected than females. The lungs and kidneys were clearly target organs for HFIB, the kidneys being more sensitive in this study (having increased absolute and relative weights, alterations in relevant clinical chemistry parameters, and alterations in microscopic structure). A clear dose-response pattern for the above toxic effects was evident with 10 ppm in the males being an effect level. Male rats exposed to 30 ppm of HFIB had decreased body weights and significantly increased kidney weights. A satellite group of animals was maintained for 2 weeks after the completion of exposure. These animals showed some remission from the observed toxic effects, indicating recovery could be expected in rats from at least most of the toxic effects associated with exposure to HFIB. All effects observed in 3 ppm males disappeared by the end of the recovery period.

Inhalation toxicity studies with boron trifluoride

An acute study of boron trifluoride (BF3) in rats indicated the 4-hr LC50 to be 1.21 mg/liter. In a 2-week study, all animals exposed to 180 mg/m3 died prior to the sixth exposure, rats exposed at concentrations of 66 and 24 mg/m3 showed clinical signs of respiratory irritation, body weight gain depressions, increased lung weights, and depressed liver weights. Histopathology showed necrosis and pyknosis of the proximal tubular epithelium of the kidneys. This effect was limited to the high-concentration exposure group. Based on the results of these studies, Fischer 344 rats were exposed 6 hr/day, 5 days/week for 13 weeks to a respirable, liquid aerosol of BF3 at concentrations of 0, 2.0, 6.0, and 17 mg/m3. One rat in the high exposure group died. The most significant finding in this group was necrosis of the proximal tubular epithelium of the kidneys. Other observations noted during the study included dried material around the nose and mouth, rales and excessive lacrimation, reversible depression of serum total protein and globulin concentrations, and increases in urinary, serum, and bone fluoride amounts. In the lower exposure groups, findings of respiratory irritation were minimal. All observations occurred in a dose-related pattern. Based on this study, exposure to BF3 at 17 mg/m3 resulted in renal toxicity, while exposure at 6 mg/m3, although showing elevations of fluoride amounts, did not result in a toxic response.

Effect of thyroid hormones on human mononuclear leukocyte lysosomal acid lipase activity

Lysosomal acid lipase (LAL), the enzyme which hydrolyzes lipoprotein cholesteryl esters, is under thyroid hormone regulation in experimental animals. To evaluate whether human LAL is also under thyroid regulation, we measured mononuclear leukocyte LAL activity in 31 hypothyroid, hyperthyroid, and euthyroid children under treatment. LAL activity was positively correlated with serum T3 and serum T4 levels, and was significantly higher in hyperthyroid children than in those who were hypothyroid. In another study, 5 adult euthyroid males were given 50 micrograms L-T3 every 8 h for 4 days. Their LAL activities increased significantly after treatment. The data suggest that LAL activity in man, as in experimental animals, is influenced by thyroid hormone status. Hormonal control of LAL activity may be important in the regulation of human cholesterol metabolism.

Acid lipase activity of human lymphocytes

Acid lipase activity was examined in human leukocytes using 4-methylumbelliferyl esters in a fluorimetric assay. Mononuclear leukocytes had 10--15 times the acid lipase activity of polymorphonuclear leukocytes. The enzyme activity was highest using the oleate ester of 4-methylumbelliferone at pH 4.0, in the presence of L-alpha-phosphatidylcholine and taurodeoxycholic acid (sodium salt). Acid lipase activity was inhibited by diethylaminoethoxyhexestrol, sodium chloride and fluoride, potassium chloride, calcium chloride and albumin, but was unaffected by diethyl p-nitrophenyl phosphate or sulphydryl reagents. There were at least two forms of acid lipase activity: one (A form) was sensitive to heart inactivation (56 degrees C) and corresponded to the enzyme deficient in patients with Wolman's disease; the other (B form) was resistant to heat inactivation and corresponded to the residual enzyme activity found in Wolman's disease.