Iatrogenic exposure to mercury after hepatitis B vaccination in preterm infants.

Thimerosal, a derivative of mercury, is used as a preservative in hepatitis B vaccines. We measured total mercury levels before and after the administration of this vaccine in 15 preterm and 5 term infants. Comparison of pre- and post-vaccination mercury levels showed a significant increase in both preterm and term infants after vaccination. Additionally, post-vaccination mercury levels were significantly higher in preterm infants as compared with term infants. Because mercury is known to be a potential neurotoxin to infants, further study of its pharmacodynamics is warranted.

Maternal drug use during pregnancy: are preterm and full-term infants affected differently?

This study examined whether preterm infants are more vulnerable to the effects of prenatal drug exposure than are full-term infants. The sample of 235 low-income African American mothers and their infants included 119 cocaine-polydrug users, 19 alcohol-only users, and 97 nonusers; 148 infants were full term and 87 were preterm. Direct effects of exposure on birth weight, birth length, ponderal index, and irritability were moderated by length of gestation: Fetal growth deficits were more extreme in later-born infants, whereas increases in irritability were more extreme in earlier born infants. Effects of exposure on cardiorespiratory reactivity to a neonatal exam were not moderated by length of gestation. In general, effects of exposure occurred for both cocaine-polydrug and alcohol only users and so could not be unambiguously attributed to either of these drugs alone.

Mercury toxicity awareness in the nursery.

Mercury vapor may pose an environmental risk to the developing newborn. Two case reports from Southeastern urban hospitals are presented describing potential problem identification, air sampling methods, and recommendations for minimizing the risk. Current convenience sampling of hospital nurseries revealed 11% to 20% use of mercury-filled glass thermometers. Because this use continues to place infants at risk, health care provides must be educated in removing mercury to the extent possible and in ensuring a mechanism for cleaning mercury spills.

Organization and function of a hospital ethics committee.

The developing ethics committee must address many issues around the structure and function of the committee. This article reviews such matters as membership, training, and committee policy. Committee functions are reviewed with suggestions about education as well as ethics consultation.

Ethical decision making in perinatal asphyxia.

This article examines the difficulties of defining perinatal asphyxia. Once the central clinical concern is identified, the ethical questions become clearer. A variety of procedural and ethical issues also need to be considered; especially those related to how physicians introduce and dialogue with parents about difficult life and death decisions. Depending on how well this is accomplished, sound medical practice, parental autonomy and the patient's best interest issues can all be effectively addressed with a minimum of conflict.

Comparison of band and spot electrodes for the measurement of stroke volume by the bioelectric impedance technique.

OBJECTIVES: Conventional impedance cardiography uses a tetrapolar band electrode configuration to determine thoracic bioelectrical impedance changes and to quantify cardiovascular variables. The present study evaluated the effect of electrode type, band or electrocardiograph (spot), placed in the same anatomical location, on both the absolute value of cardiovascular variables and the percent change in the variable when the patient changed position from supine to standing. DESIGN: Prospective, randomized studies using repeated-measures design. SETTING: Research laboratory. PATIENTS: Twenty-one adult volunteer subjects. INTERVENTIONS: Subjects were studied while supine and again when standing, in random order as to first position. MEASUREMENTS AND MAIN RESULTS: Stroke volume and impedance-derived variables were measured. Values for stroke volume measured by the band electrode array were 85 +/- 7 and 49 +/- 3 mL for supine and standing, respectively. In contrast, stroke volume measured through the spot electrodes was 110 +/- 8 and 59 +/- 3 mL, respectively. These differences were due to a lower baseline thoracic bioelectrical impedance value measured through the spot electrodes. However, the percent changes for stroke volume with standing subjects were the same when measured through band (-41 +/- 3%) or spot (-44 +/- 3%) electrodes. CONCLUSIONS: The comparison of cardiovascular values obtained by impedance cardiography should be accomplished only when the values are obtained using similar electrode configuration and type. While there may be a variation in the absolute value of the variable, the direction and magnitude of the change in the variable is relatively unaffected by the electrode types as used in this study.

In utero exposure to cocaine: a review.

Cocaine is now regarded as one of the most dangerous illicit drugs available today. A disturbing trend in the pattern of cocaine use is that groups long considered unlikely to be involved in drug use, including women of childbearing age, pregnant women, the pediatric age group, fetuses, and neonates, are showing an alarming increase in cocaine exposure. Substantial data have been derived from clinical observations, clinical studies, and animal studies indicating that prenatal exposure to cocaine may have detrimental short-term and possibly long-term effects on the mother, the developing fetus, and the neonate. The effects attributed to cocaine may, however, be due to other substances (eg, alcohol) ingested by the drug-using woman, to prematurity, or to the environmental chaos in which the infant must develop. Prospective controlled studies are needed to define further the effects of cocaine as distinct from other negative influences having an impact on the developing fetus, the newborn, or the infant.

Cocaine: a neonatal perspective.

This paper focuses on cocaine misuse as it impacts on neonates born at Grady Memorial Hospital in Atlanta, Georgia. The majority of infants of cocaine-using mothers (ICAM) appear clinically normal and pass through the "normal nursery." However, the longer hospital stay for the smaller, sicker ICAMs means that many cocaine-exposed sick infants are in the hospital at any time. The misperceptions of the pregnant cocaine-misusing woman often cause the ICAM to be born prematurely. The prematurity then superimposes other potential threats on the infant. Further, the environmental chaos into which these mothers and infants return following discharge may also contribute to the difficulties seen among these children. Finally, there are unanswered questions that have to be confronted by the hospital staff. These include ethical questions related to the "costs" of care to the cocaine-exposed infant.

Radioimmunoassay screening of dried blood spot materials for benzoylecgonine.

Residual samples of blood spots, which are routinely collected on almost all newborns in the United States, can be used to determine seroprevalence information on newborns and maternal exposures to various substances, including drugs of abuse. By modifying a commercial radioimmunoassay (RIA) kit for urinary samples, one can use blood spotted on filter paper as a matrix to quantitate the cocaine metabolite benzoylecgonine (BE). BE is stable for long periods of time in blood spots and we were able to quantitatively extract it with aqueous buffer. There were no matrix effects of the blood spot eluate on the RIA, and excess lipid in the blood did not alter measurement of BE. By using standards made up of BE in negative blood spot eluate and calibrators of blood that were spiked with BE and then spotted on filter paper to determine extraction efficiency, low levels of BE in blood could be measured. The limit of detection was 5 ng/mL, and the limit of quantitation was 10 ng/mL. Levels of BE in blood collected at autopsy in eluates of blood spots were measured, and they established excellent correlation (r2 = 0.93) with gas chromatography/mass spectrometry measurements. To test this technology, residual blood spots on 545 infants from three states were analyzed for BE.

Cardiothoracic variables measured by bioelectrical impedance in preterm and term neonates.

OBJECTIVE: To report the range of normal values for impedance-derived cardiac output, stroke volume, and the baseline transthoracic impedance in the healthy preterm and term neonate over the weight range generally found in the intensive care nursery. DESIGN: Prospective, case-referent study. SETTING: University medical center special care and term nurseries. PATIENTS: Twenty-seven preterm and 25 term newborns with no evidence of cardiovascular problems. INTERVENTIONS: We determined the values for impedance cardiac output and stroke volume to be used as reference values. Also measured was the baseline transthoracic impedance, a number that reflects the air/fluid ratio of the thorax. MEASUREMENTS AND MAIN RESULTS: Stroke volume and stroke volume index were, respectively, 2.0 +/- 0.8 (SD) mL and 1.4 +/- 0.5 mL/kg for preterm infants, and 5.0 +/- 2.0 mL and 1.6 +/- 0.7 mL/kg for term neonates. Cardiac output and cardiac index were, respectively, 304 +/- 114 mL/min and 214 +/- 68 mL/min.kg for preterm newborns, and 648 +/- 244 mL/min and 205 +/- 78 mL/min.kg in term newborns. These values compared favorably with published values utilizing other techniques for these populations. Both cardiac output and stroke volume were linearly correlated to body weight, being largest in the heavier neonates. Transthoracic impedance values were 42.7 +/- 9.0 ohms and 6.7 +/- 1.7 ohms/cm for preterm infants and 32.3 +/- 4.3 ohms and 3.9 +/- 0.6 ohms/cm for term infants. Transthoracic impedance and transthoracic impedance/cm values were correlated negatively to body weight and were curvilinearly related to body weight. CONCLUSIONS: These values for transthoracic impedance and transthoracic impedance/cm are the first reported using the standard electrode lead configuration in neonates.

A model for diagnosis and initial therapy of pneumothorax in the neonate.

Treatment of pneumothorax may require prompt and aggressive medical management. Currently, the only models for practicing detection and evacuation of pneumothoraces are in living animals. This paper describes a simple doll model for diagnosis and treatment with needle aspiration. This easily made model demonstrates unilateral or bilateral pneumothorax to test the diagnostic and therapeutic capabilities of the trainee. The other major benefit is to avoid trauma or death in the living animal model.

Withdrawal emergent syndrome in an infant associated with maternal haloperidol therapy.

Withdrawal emergent syndrome (WES) is a subtype of tardive dyskinesia that has been reported in children who were taken off antipsychotic therapy. We present the first case of WES in an infant born to a mother taking haloperidol during her pregnancy. The infant developed repeated tongue thrust, abnormal hand posturing, and tremor of all extremities. Most symptoms resolved within several days, but tongue thrust continued until 6 months of age.

The combined effects of hypoxemia and mechanical ventilation on renal function.

The combined effects of hypoxemia and mechanical ventilation on renal function were investigated in anesthetized dogs. Spontaneously breathing dogs (S) and dogs mechanically ventilated with a volume-ventilator (V) were made hypoxemic by breathing hypoxic gas to achieve PaO2 values of 35 and 22 mm Hg. At a PaO2 of 35 mm Hg, urine output and sodium excretion were increased in both groups. These responses closely followed the blood pressure response, which was greater in the V group. Renal blood flow (RBF), glomerular filtration rate (GFR), and fractional sodium excretion (FNA) were unchanged. At a PaO2 of 22 mm Hg, both groups demonstrated a reduction in urine flow, sodium excretion, FNA, RBF, and GFR. However, the mechanism involved was different and ventilator-dependent. At this low PaO2, arterial blood pressure was reduced in the S group with no change in renal resistance, while blood pressure increased in the V group with a marked increase in renal resistance as a result of the modification of the cardiovascular effects of lung inflation reflexes by mechanical ventilation. These results indicate that renal function is well-maintained at low PaO2 values (35 mm Hg) and reduced at more severe hypoxemia, mainly in response to systemic hemodynamics.

Oscillatory cardiopulmonary effects of high-frequency jet ventilation.

The cardiovascular effects of high-frequency jet ventilation (HFJV) were compared with conventional volume ventilation in the anesthetized dog. A unique effect of HFJV on stroke volume and cardiac output was observed when stroke volume was analyzed on a beat-by-beat basis with impedance cardiography. A pronounced amplitude modulation of stroke volume, as well as of pulmonary and arterial pressure, occurred when the frequency of the HFJV approached the heart rate. The beat frequency of these amplitude oscillations was equal to that predicted based upon the frequency of the HFJV and the heart rate. Cardiac outputs obtained by techniques which average several beats will not detect these oscillations in cardiac output. These findings suggest that HFJV can generate an oscillation in thoracic hemodynamics which affects ventricular output in a similar manner.

Evaluation of impedance cardiography in the canine pup.

This study evaluated the use of the noninvasive technique of impedance cardiography to assess central hemodynamics in an animal model similar in size to the neonate. Seven canine pups 5-6 wk of age, with an average weight of 2.2 kg, were studied. To alter cardiac output (Q), the pups were given 12 and 8% O2 to breathe, which produced an arterial PO2 of 30 and 21 Torr, respectively. Q was obtained simultaneously by impedance and thermal dilution under both normoxic and hypoxic conditions. The average Q measured by impedance and thermal dilution were within 10% agreement and moderately correlated (r = 0.76). Impedance Q and stroke volume (SV) averaged 201 ml X min-1 X kg-1 and 2.8 ml, respectively. Thermal dilution Q and SV averaged 212 ml X min-1 X kg-1 and 2.9 ml, respectively. Individual responses to the hyoxemia were variable, but the impedance technique appeared to measure these individual responses as well as the thermal-dilution technique. These findings demonstrate that impedance cardiography may be suitable to assess either the absolute or relative changes in central hemodynamics. The use of this technique in critical care neonatal and pediatric medicine seems justified.

Renal oxygen delivery and consumption during progressive hypoxemia in the anesthetized dog.

The relationship between renal oxygen delivery (RDO2) and function was evaluated during progressive hypoxemia. Seven anesthetized, spontaneously breathing dogs were given progressively lower oxygen concentrations to breathe while monitoring renal O2 consumption (RVO2), renal hemodynamic and excretory function. In addition, basal RVO2 was determined in three models of kidneys without filtration. RDO2 averaged 3648 mumole O2/min/100 g during normoxia. Basal RVO2 averaged 100 mumole O2/min/100 g kidney while total RVO2 was 466 mumole O2/min/100 g kidney during normoxia, leaving 366 mumole O2/min/100 g consumed by those processes involved in tubular transport. During hypoxemia, all renal parameters were well maintained until the lowest PaO2 (24.2 Torr). At this level, total RVO2 and RDO2 were significantly reduced. However, RDO2 remained well above RVO2 throughout hypoxemia. The reduction in RVO2 was a direct result of decreased O2 demand, as glomerular filtration and tubular load were also reduced. This associated decrease in O2 demand and RVO2 was indicated by the fact that the renal (a - v)O2 difference remained low and unchanged (1.9 vol%), fractional sodium excretion was unchanged, and the ratio of tubular sodium reabsorption to RVO2 also remained unchanged (30.8 meq Na/mmole O2). It was concluded that hypoxemia, while reducing both RDO2 and RVO2 at the lowest PaO2 (24.2 Torr), did not functionally impair renal excretory function by limiting RDO2 to the tubular transport processes. A reduction in RBF is far more likely to compromise the RDO2 needed to sustain basal and active transport processes than hypoxemia itself.

Erroneously high Dextrostix values caused by isopropyl alcohol.

Glucose oxidase peroxidase chromogen reagent (Dextrostix) in combination with the Eyetone colorimeter has become increasingly popular in the rapid detection of hypoglycemic states in the newborn. Although the reliability of this system is well documented, there are several factors which can compromise the accuracy of the procedure. One such problem is the glucose reading given after a blood-alcohol combination is tested. By decreasing the light reflected from the strip, the optical electrical interpretation of the Dextrostix is altered by alcohol such that there is an apparent increase in the glucose level as read by the eyetone meter.

Effect of epidermal growth factor on lung maturation in fetal rabbits.

Injection of epidermal growth factor (EGF) into 24-day rabbit fetuses (5 microgram, im or ip) induced accelerated maturation of the lung. On sacrifice at day 27, there was greater distensibility and stability on deflation associated with the appearance of a complement of type II cells approaching that of the rabbit at term. EGF treatment had no demonstrable effect on body weight or lung weight in this group of animals. Saline-injected control fetuses were not affected significantly.