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Biomedical subjects

W Meadow

Publications and source records attributed to W Meadow.

28 records · Page 2Linked to original sources
PubMed1993

Relative contribution of endothelium-derived relaxation factor to vascular tone in the systemic, pulmonary, and cerebral circulations of piglets.

UNLABELLED: We determined the contribution of endothelium-derived relaxation factor (EDRF) to vascular tone in the systemic, pulmonary, and cerebral circulations of piglets. METHODS: 11 piglets were anesthetized and mechanically ventilated. Systemic cardiac output was determined by an electromagnetic flow probe placed on the main pulmonary artery. Cerebral blood flow was assessed by determining unilateral internal carotid artery blood flow (ICBF) using a flow probe placed on the common carotid artery after ligation of the ipsilateral external carotid circulation. Progressive inhibition of EDRF was achieved by continuous infusion of the substituted L-arginine analog N-nitro-L-arginine (NNLA). Hemodynamic observations were compared at 0, 0.1, 1.0, 10, 30, and 80 mg/kg cumulative dose of NNLA. RESULTS: At all NNLA doses > or = 1 mg/kg, both systemic blood pressure and systemic vascular resistance were elevated. At all NNLA doses > or = 10 mg/kg, systemic cardiac output was reduced. At all NNLA doses > or = 10 mg/kg, pulmonary artery pressure and pulmonary vascular resistance were elevated. Although cerebral vascular resistance was elevated at all NNLA doses > or = 10 mg/kg, ICBF was maintained at or near baseline values up to a dose of 80 mg/kg. At all levels of EDRF inhibition, both the pulmonary and systemic circulations demonstrated approximately equal magnitudes of vasoconstriction. In contrast, at 30 and 80 mg/kg cumulative dose of NNLA, the cerebral circulation was relatively less constricted by NNLA than was the systemic circulation. Systemic VO2 was significantly reduced at 30 mg/kg and 80 mg/kg cumulative NNLA dose, while cerebral VO2 was preserved at both NNLA doses. CONCLUSIONS: EDRF contributes to resting vasodilator tone in the systemic, pulmonary, and cerebral circulations in piglets. Progressive inhibition of EDRF constricts the systemic and pulmonary circulation equally. Inhibition of EDRF does not impair the ability of the brain to vary cerebral vascular resistance in order to redistribute blood flow towards itself during a period of reduced cardiac output.

Animals↗
PubMed1992

Transplacental immunity to varicella-zoster virus in extremely low birthweight infants.

Sixteen infants in our intensive care nursery (ICN) were inadvertently exposed to an adult who presented the next day with chickenpox. Since a majority of the patients were extremely premature, we were concerned that they might not have received transplacental varicella-zoster virus (VZV) antibody, and consequently would be at risk for contracting chickenpox. Serum samples were obtained from each infant and examined for the presence or absence of VZV antibody. Fourteen of the 16 infants had antibody levels equal to or in excess of 1:16 by indirect fluorescent antibody, including six of eight infants with birthweights equal to or less than 1000 gm, and eight of ten infants with gestational ages equal to or less than 28 weeks. Passive transfer of immunity to VZV appears to be common in infants as young as 24 to 28 weeks' gestation.

Antibodies, Viral↗
PubMed1992

What is the legal 'standard of medical care' when there is no standard medical care? A survey of the use of home apnea monitoring by neonatology fellowship training programs in the United States.

In treating a patient, a doctor is obliged to use the skill and care that is ordinarily used by reasonably well-qualified doctors in similar cases. In addition, the only way in which a juror may decide whether the defendant used the skill and care which the law required of him or her is from evidence presented by doctors called as expert witnesses (cf Illinois Pattern Jury Instructions). However, what should be done if expert opinions differ concerning the care that is "ordinarily used"? Home apnea monitoring (HAM) is prescribed at times for graduates of neonatal intensive care units despite the fact that indications for its use are not well established and efficacy is completely unknown. The authors attempted to determine standards for HAM as it is currently practiced in neonatology training programs. The primary teaching hospital for each of the 99 neonatology training programs in the United States was identified. Both the medical director (MD) and a neonatal intensive care unit nurse manager (RN) were asked about the use of HAM in their own nursery for four clinical vignettes. Each vignette depicted a 1000-g birth weight infant, currently 7 weeks old and ready for discharge. In three vignettes, the infant had demonstrated no apnea, mild apnea (resolved by 2 weeks of age), or moderate apnea (requiring theophylline therapy at discharge) during the hospital course. In the fourth vignette, the infant had no apnea but was to be discharged home with supplemental oxygen. For 67 of 99 training programs, paired responses of RN managers and MD directors were obtained.(ABSTRACT TRUNCATED AT 250 WORDS)

Aftercare↗
PubMed1988

Selective inhibition of thromboxane synthetase reduces group-B-beta-hemolytic-streptococci-induced pulmonary hypertension in piglets.

13 newborn piglets with group-B-beta-hemolytic-streptococci (GBS)-induced pulmonary hypertension were assigned to receive either placebo (group 1) or Dazmegrel, a thromboxane synthetase inhibitor (group 2). All piglets with pulmonary hypertension had increased thromboxane B2 (TxB2) and 6-keto PGF1 alpha levels. With continued GBS infusion, the placebo group demonstrated a continued elevation of pulmonary artery pressure (PAP) and of TxB2. The Dazmegrel piglets, however, despite continued GBS infusion, demonstrated a selective decrease in PAP associated with a significant decrease in TxB2 levels and stability of systemic pressure and cardiac output. These data demonstrate that thromboxane synthetase inhibition is effective therapeutically in selectively reducing PAP.

6-Ketoprostaglandin F1 alpha↗
PubMed1986

Clinical correlates do not predict PaO2 response after tolazoline administration in hypoxic newborns.

In an attempt to determine which hypoxic newborns might benefit from administration of tolazoline hydrochloride (Tz), we identified all neonates known to have received Tz at four Chicago area perinatal centers over a 4-yr period. For each of 41 infants, five statistical analyses were used to correlate 31 clinical and ventilatory variables with PaO2 values before and after Tz administration. Fourteen neonates responded to Tz infusion with more than a two-fold increase in PaO2. None of 31 clinical variables successfully predicted a positive Tz response in these infants, and a positive response (increased PaO2) was not associated with increased likelihood of survival. BP fell after Tz in 72% of patients, while heart rate rose after Tz treatment in 66% of cases. These data suggest a need to re-evaluate the administration of Tz to hypoxic newborn infants.

Blood Pressure↗
PubMedDate not supplied

Hemodynamic effects of combining epinephrine with nitroglycerin or nitroprusside during group B streptococcal sepsis in piglets.

Septic shock in young children is often characterized by clinical findings consistent with a reduction in cardiac index (CI) and elevation of systemic vascular resistance index (SVRI). In this context, infusion of inotropic agents, alone or in combination with vasodilators, has been recommended. We have utilized group B streptococcal (GBS) infusion in piglets to develop a model of low-CI/high-SVRI septic shock, and report here the effects of the combination of epinephrine (EPI) plus either nitroglycerin (NG) or nitroprusside (NP) in this model of infant sepsis. Piglets were anesthetized, intubated, and ventilated. All piglets received GBS continuously for 90 minutes and were further divided into three experimental groups. Group 1 received NG 16 micrograms/kg.min plus EPI 2 micrograms/kg.min; group 2 received NP 10 micrograms/kg.min plus EPI 2 micrograms/kg.min, and group 3 received 0.9% sodium chloride (saline) only. CI, which fell for all three groups at the onset of GBS infusion, rose significantly in group 2 animals (but not in groups 1 and 3). This effect was mediated entirely by an increase in myocardial stroke volume. Aortic blood pressure, initially unaffected by GBS infusion, rose significantly in both group 1 and 2 compared with group 3. SVRI, which rose for all three groups at the onset of GBS infusion, was further markedly elevated in group 1 (but not in groups 2 and 3). Pulmonary artery pressure and pulmonary vascular resistance index, both significantly increased after GBS infusion, were reduced in group 2 but not groups 1 and 3. These observations illustrate the potential for unexpected, and possibly detrimental, hemodynamic consequences when vasoactive agents are combined in young septic animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗