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Biomedical subjects

A M Lynn

Publications and source records attributed to A M Lynn.

At least 19 recordsLinked to original sources
PubMed1992

The maturation of morphine clearance and metabolism.

OBJECTIVE: To determine how early in childhood the clearance of morphine sulfate reaches that in adults. DESIGN: Patient series. SETTING: Children's Hospital and Medical Center, Seattle, Wash. PARTICIPANTS: Forty-nine children aged 1 day to 2.5 years with normal renal and hepatic function. All children were receiving a constant rate intravenous infusion of morphine for postoperative analgesia for greater than 24 hours. INTERVENTIONS: Blood and urine samples were collected during infusion and immediately after discontinuation of the morphine infusion. MEASUREMENTS: Morphine concentrations were determined and clearance was calculated using the infusion data. Half-life and volume of distribution were calculated using the postinfusion data. The formation of metabolites was evaluated using the urine data. Morphine clearance increased with age, median clearances ranging from 5 mL/kg per minute in neonates aged 1 to 7 days to 21 mL/kg per minute in infants aged 6 months and older. This change in clearance correlated with age. The formation clearance of morphine glucuronide was correlated with age, whereas the formation clearance of morphine sulfate and the renal clearance of morphine were independent of age. CONCLUSIONS: Morphine clearance reaches adult values by age 6 months to 2.5 years. In contrast to previous reports on the maturation of sulfate conjugation, it does not appear that morphine sulfate clearance is enhanced relative to glucuronidation in early infancy.

Analgesia↗
PubMed1991

After the contract ... which way now?

There can be little doubt that the treadmill of NHS dentistry has done little to improve standards, and one can only applaud those who are so actively seeking to do so. But, perhaps sometimes we should examine our motives. Why do we want to improve? We cannot all hope to provide the very best for everyone. There simply are not the funds or the dentists. Is it so that we can obtain more money, or greater job satisfaction, or to give the patient a better deal?

Dental Auxiliaries↗
PubMed1991

Age-dependent morphine partitioning between plasma and cerebrospinal fluid in monkeys.

Steady-state partitioning of morphine between blood and cerebrospinal fluid (CSF) was evaluated in pigtailed monkeys at three ages: 2-3 days, 1 month and 1 year. Protein binding of morphine to serum proteins was assessed by ultrafiltration. Newborns showed a higher CSF to plasma ratio than the 1-month- or 1-year-old monkeys (0.506 vs. 0.369 or 0.374, respectively). Protein binding of morphine was 11% in newborns, and 17% at 1 year of age, not explaining the increased morphine penetration into CSF in newborns. Increased CSF morphine is a transient finding in infant macaques, which appears to reach young adult values by 1 month of age.

Aging↗
PubMed1991

Pharmacokinetics and pharmacodynamics of morphine in infant monkeys.

We report the pharmacokinetics of morphine administered as intravenous boluses in newborn (less than 7 days) and 3- to 4-month-old macaque monkeys. Morphine was administered in a series of bolus doses until PaCO2 was elevated greater than 50 mm Hg. In newborns less than 7 days of age, a mean dose of 1.4 mg/kg was required (range 0.75-2.8 mg/kg), and in the 3-month-olds, a mean dose of 1.88 mg/kg was required (range 1.5-2.5 mg/kg). The respiratory effects measured by PaCO2 and respiratory rate did not correlate with declining serum or cerebrospinal fluid morphine levels. Both newborn and 3- to 4-month-old macaque monkeys show only mild respiratory depression after intravenous morphine, at serum concentrations as high as 300-400 ng/ml. Infant and young macaque monkeys appear to be less sensitive to the respiratory depressant effect of morphine than humans.

Aging↗
PubMed1988

From Black to White.

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Dental Restoration, Permanent↗
PubMed1988

Short-acting barbiturate sedation: effect on arterial pH and PaCO2 in children.

One hundred and fifteen unpremedicated children, induced with thiamylal, a short-acting thiobarbiturate, administered rectally (25 mg.kg-1 body wt) or intravenously (6 mg.kg-1) had arterial pH of 7.36 +/- 0.03 and PaCO2 of 40 +/- 4 mmHg. In 22 children over two years of age, the use of fentanyl (1.2 +/- 0.7 microgram.kg-1) in addition to the thiamylal did not change blood gas data compared to those children over two years receiving only barbiturates (pH 7.36 vs 7.36, PaCO2 41 vs 40 mmHg). Children with cyanotic congenital heart disease showed similar pH and PaCO2 to acyanotic children following administration of the short-acting barbiturate. Thiobarbiturates, given in a titrated fashion under direct observation, have clinically small effects on arterial pH and PaCO2 in paediatric patients.

Administration, Rectal↗
PubMed1988

Effect of pH and PCO2 on pulmonary and systemic hemodynamics after surgery in children with congenital heart disease and pulmonary hypertension.

Fourteen children with congenital heart disease and associated pulmonary hypertension (preoperative mean pulmonary artery pressure (MPAP) 48 mm Hg +/- 1 SEM were examined to determine the effect of arterial carbon dioxide tension (PaCO2) and pH on pulmonary and systemic hemodynamics after surgical repair. Baseline measurements were obtained with hyperventilation to PaCO2 20 to 30 mm Hg (pH 7.56 +/- 0.01 mm Hg). The addition of carbon dioxide to inspired gas to achieve a PaCO2 40 to 45 mm Hg (pH 7.35 +/- 0.01) resulted in a significant increase in MPAP, from 32 +/- 5 mm Hg to 47 +/- 8 mm Hg (p less than 0.05). An increase in mean cardiac index (CI) from 2.7 +/- 0.3 L/min/m2 to 3.3 +/- 0.3 L/min/m2 (p less than 0.05) explained in part the associated increase in MPAP. For a subgroup of eight patients with postoperative MPAP greater than 30 mm Hg (at pH 7.35 to 7.40), pulmonary vascular resistance index (PVRI) also significantly increased (p less than 0.05) as PaCO2 was increased, implying a direct pulmonary vasodilating effect of alkalosis. Removal of carbon dioxide from inspired gas returned hemodynamic values to baseline. The higher the MPAP at physiologic pH the greater the absolute amount of MPAP reduction and PVRI reduction (p less than 0.05) with alkalosis. No complications from alkalosis were seen. We suggest that a trial of hypocarbic alkalosis in the child with severe residual pulmonary hypertension after surgical repair of congenital heart disease is warranted to reduce right ventricular afterload.

Adolescent↗
PubMed1987

AIDS and the dentist.

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Acquired Immunodeficiency Syndrome↗
PubMed1987

Morphine pharmacokinetics in early infancy.

The pharmacokinetics of morphine in ten infants less than or equal to 10 weeks of age who were receiving morphine infusions were determined. Infants 1-4 days of age (newborns) showed longer elimination half-lives than the older infants (6.8 vs. 3.9 h). Clearance in the newborns is less than one-half that found in older infants (6.3 vs. 23.8 ml X min-1 X kg-1). The combination of lower clearance and longer elimination half-life in newborns (0-7 days) may well explain a prolonged duration of action for morphine in very young infants, but other etiologies are needed to explain the respiratory sensitivity believed to persist in older infants.

Female↗
PubMed1987

Brain death?

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Brain Death↗
PubMed1987

Caudal morphine for postoperative analgesia in children: a comparison with caudal bupivacaine and intravenous morphine.

We compared the efficacy, duration, and side effects of preservative-free morphine injected into the caudal space in children, with caudal bupivacaine and with intravenous morphine administration for relief of postoperative pain. Forty-six children, ages 1-16 yr, were randomly assigned to receive intravenous morphine (control group), caudal bupivacaine (0.25%, 1 ml/kg), or caudal morphine (0.5 mg/ml, 0.1 mg/kg). In half the patients given caudal morphine, the morphine was mixed with a dose of lidocaine adequate to produce sacral analgesia, to confirm correct caudal injection of the morphine. Caudal injections were performed at the end of surgery. Time until the first required postoperative intravenous morphine dose was recorded for each patient. The duration of analgesia was significantly greater with caudal morphine (median 12 hr, P less than 0.02) than with caudal bupivacaine (median 5 hr), and both were greater than with intravenous morphine in control patients (median 45 min). Urinary retention, pruritus, and nausea appeared with slightly greater frequency in the caudal morphine group, but no delayed respiratory depression occurred. Caudal morphine (0.5 mg/ml, 0.1 mg/kg) provided 8-24 hr of analgesia in children without a significantly greater incidence of side effects than caudal bupivacaine or intravenous morphine.

Adolescent↗
PubMed1986

Pulse oximetry during cardiac catheterization in children with congenital heart disease.

One hundred and five children with congenital heart disease were monitored by pulse oximetry during cardiac catheterization. Excellent correlation (r = 0.95) was found between oxygen saturation values obtained with pulse oximetry and those obtained from arterial blood in 133 data pairs. This correlation was described by the regression equation y = 0.91x + 8.1. The correlation was also excellent in 47 data pairs with saturation values of less than 90% (r = 0.94, y = 0.93x + 6.0) from 36 cyanotic children. The clinical usefulness of pulse oximetry in the early recognition of decreased pulmonary blood flow or partial airway obstruction was demonstrated. Early diagnosis of changes in oxygenation was especially helpful in children with cyanotic congenital heart disease, in whom small changes in arterial oxygen tension may cause large changes in oxygen saturation.

Adolescent↗
PubMed1986

Systemic responses to tourniquet release in children.

The hemodynamic and metabolic effects of deflation of pneumatic tourniquets were assessed in 15 children, seven of whom had bilateral tourniquets applied. Systemic acidosis from release of lactate and PaCO2 after tourniquet deflation did not cause adverse effects in these healthy children. Larger increases in lactate were seen with longer tourniquet inflation times (greater than 75 min) or with bilateral tourniquets. The greatest decrease in pH was seen with simultaneous deflation of bilateral tourniquets. Heart rate did not change with tourniquet deflation, whereas systolic blood pressure decreased 8-10 mm Hg with deflation. Blood pressure returned to control values within 5-10 min; no arrhythmias were seen. Recommendations to minimize the systemic metabolic effects after release of tourniquets in children under general anesthesia include the following: 1) attempt to limit tourniquet inflation times to less than 75 min; 2) use controlled ventilation prior to and after tourniquet deflation to remove the respiratory component of acidosis; 3) check blood gas tensions within 5 min of tourniquet deflation in children with long tourniquet inflation times (greater than 75 min), and where bilateral tourniquets are deflated simultaneously or within 30 min of each other.

Adolescent↗
PubMed1985

Isolated deafness following recovery from neurologic injury and adult respiratory distress syndrome. A sequela of intercurrent aminoglycoside and diuretic use.

We report two children who survived neurologic injury (near-drowning and Reye's syndrome) and adult respiratory distress syndrome and who required prolonged ventilatory support. Follow-up examination in both children showed steady neurologic recovery, but five months following discharge from their acute illness, profound hearing loss was diagnosed in both children. A review of the literature is reported and the hypothesis that combined aminoglycoside antibiotic and loop diuretic therapy caused the hearing loss is presented. Recommendation is made for audiologic assessment within six months of recovery from critical illness of pediatric patients in whom therapy has included loop diuretic and aminoglycoside antibiotic therapy.

Aminoglycosides↗