Biomedical subjects

D M Habib

Publications and source records attributed to D M Habib.

13 recordsLinked to original sources

PubMed2003

Second-trimester pregnancy termination: comparison of three different methods.

The object of this study was to compare intravaginal misoprostol and dinoprostone (prostaglandin E2) for second-trimester pregnancy termination, and to examine the role of the nitric oxide donor, glyceryl trinitrate, as a possible alternative to prostaglandins to induce cervical ripening in second-trimester pregnancy termination. This was a randomised clinical trial. The trial involved pregnant women between 13 and 28 weeks' gestation admitted with clear medical or obstetric indications for pregnancy termination, and was carried out in the department of obstetrics and gynecology, Assiut University Hospital, Egypt. Patients were classified into Group A, where pregnancy termination was induced by vaginal misoprostol 100 micrograms every 4 hours with a maximum dose of 500 micrograms; Group B, where induction was by vaginal dinoprostone 6 mg every 6 hours with a maximum dose of 24 mg; and Group C, where induction involved vaginal glyceryl trinitrate 500 micrograms every 6 hours with a maximum dose of 2.5 mg. Twenty-four hours after the start of induction, the rate of complete abortion in the three groups was 100%, 66.67% and 0%, respectively. The rate of complete abortion was 100% in the nitric oxide (glyceryl trinitrate)-induced group after introducing a complementary procedure. The induction-abortion interval was significantly shorter, the number of doses needed was less and the maximum Bishop score reached was greater with misoprostol than with dinoprostone. A higher rate of side effects occurred with the misoprostol-induced group (74%) compared with the other two groups (46.6% and 0%). Misoprostol is a cheap, effective drug for second-trimester pregnancy termination with short induction abortion intervals but a higher rate of side effects. Prostin E2 is also effective in termination of second-trimester pregnancy but is expensive and may require high doses to be administered. Glyceryl trinitrate is an effective drug for cervical ripening (softening) but it has no role in the stimulation of uterine contractions.

Abortifacient Agents↗

PubMed2002

Two administration methods for inhaled salbutamol in intubated patients.

AIMS: To compare serum concentrations and effects on respiratory mechanics and haemodynamics of salbutamol administered by small volume nebuliser (SVN) and metered dose inhaler (MDI) plus spacer. METHODS: Blinded, randomised, crossover study in 12 intubated infants and children (mean age 17.8 months) receiving inhaled salbutamol therapy. Subjects received salbutamol as 0.15 mg/kg by SVN and four puffs (400 microg) by MDI plus spacer at a four hour interval in random order. Passive respiratory mechanics were measured by a single breath/single occlusion technique, and serum salbutamol concentrations by liquid chromatography-mass spectrometry at 30 minutes, 1, 2, and 4 hours after each dose. Haemodynamics (heart rate and blood pressure) were recorded at each measurement time. RESULTS: There was no difference in percentage change in respiratory mechanics or haemodynamics between the two methods of administration. Mean area under the curve (AUC(0-4)) was 5.86 for MDI plus spacer versus 4.93 ng/ml x h for SVN. CONCLUSIONS: Serum concentrations and effects on respiratory mechanics and haemodynamics of salbutamol were comparable with the two administration methods under the conditions studied. Future studies are needed to determine the most effective and safe combination of dose and administration method of inhaled salbutamol in mechanically ventilated infants and children.

Albuterol↗

PubMed2001

Effects of a weaning protocol on ventilated pediatric intensive care unit (PICU) patients.

As part of a learning collaborative sponsored by the Center for the Evaluative Clinical Sciences (CECS) at Dartmouth College, a multidisciplinary pediatric intensive care unit (PICU) group began meeting in 1997 to evaluate potential performance improvement (PI) opportunities. A reduction in mechanical ventilation (MV) hours was the initial team focus. The multidisciplinary team developed and implemented protocols and physician order sets outlining care for MV weaning, neuromuscular blockade/therapeutic paralyzation, and enteral feedings. Since the initiation of our protocols in July 1997, we have significantly reduced the number of hours our PICU patients receive MV.

Algorithms↗

PubMed1999

Emergency cardiopulmonary bypass for cardiac arrest refractory to pediatric advanced life support.

We report the application of emergent cardiopulmonary bypass (CPB) for three pediatric patients in the cardiac catheterization laboratory with cardiac arrest who did not respond to conventional resuscitation efforts. All three patients had return of baseline prearrest rhythms within minutes of the initiation of artificial cardiopulmonary support and the return of spontaneous circulation upon weaning CPB. Two patients had normal neurologic outcomes despite an interval of over 30 minutes from arrest to CPB. The continued judicious application and study of this technology in a small subpopulation of pediatric cardiac arrest patients is warranted.

Adolescent↗

PubMed1999

Effect of helium-oxygen on delivery of albuterol in a pediatric, volume-cycled, ventilated lung model.

Pulmonary delivery of inhaled bronchodilators in mechanically ventilated patients is inefficient whether administered by metered-dose inhaler (MDI) or small-volume nebulizer. One of the factors that causes inefficient aerosol delivery is turbulent gas. Heliox (He:O2) is a blend of helium and oxygen that is less dense than air, making turbulent flow less likely. We assessed the effect of 70% He:O2 on albuterol delivery in a mechanically ventilated pediatric lung model. Albuterol was administered by MDI with spacer, collected on a filter proximal to a test lung, and measured by high-performance liquid chromatography. Mean amount and percentage albuterol delivered were significantly (p<0.05) greater for 70% He:O2 (395+/-29 microg, 20+/-3.2%) than for 70% nitrogen:30% oxygen (241+/-29 microg,12+/-1.7%). Thus 70% He:O2 can increase the amount of albuterol delivered at the end of the endotracheal tube, suggesting a potential role for it in the care of critically ill ventilated patients.

Administration, Inhalation↗

PubMed1997

Pediatric ECMO for severe quinidine cardiotoxicity.

We report the use of extracorporeal membrane oxygenation (ECMO) to establish and maintain cardiovascular stability in a 16 month old with refractory bradydysrrhythmias and hypotension after an acute overdose of quinidine. He underwent an 11-day course of ECMO and was discharged with normal neurologic function. This case illustrates the role ECMO can play in the treatment of profound cardiovascular collapse caused by toxic ingestions. To be optimally effective, management of such patients must be anticipatory.

Anti-Arrhythmia Agents↗

PubMed1996

Albuterol delivery by metered-dose inhaler in a mechanically ventilated pediatric lung model.

OBJECTIVES: To assess albuterol delivery by metered-dose inhaler in a mechanically ventilated pediatric lung model and to determine the influence of the following variables on albuterol delivery: endotracheal tube diameter; type of spacer; humidification; and pulmonary mechanics. DESIGN: Prospective, in vitro, laboratory study. SETTING: Research laboratory. INTERVENTIONS: A model, consisting of a volume-cycled ventilator, pediatric breathing circuit, 4.0- or 6.0-mm endotracheal tube, and lung simulator, was assembled. Ventilator settings were: tidal volume 250 mL; FIO2 0.5; inspiration/expiration ratio 1:3; respiratory rate 25 breaths/min; positive end-expiratory pressure 3 cm H2O; temperature 35 degrees C; and a decelerating flow pattern, using dry and humidified air. Lung simulator compliance and resistance values were consistent with those values reported for healthy childeren (20 mL/cm H2O and 40 cm H20/L/sec) and children with pulmonary disease (10 mL/cm H2O and 60 cm H2O/L/sec). Pulmonary mechanics were verified with a pulmonary function diagnostic system. Ten metered-dose inhaler canisters were used to administer 2000 micrograms of albuterol, using either a collapsible or a rigid spacer. A circuit filter placed immediately proximal to the test lung collected drug exiting the endotracheal tube. The filter was rinsed with water and albuterol concentrations were determined by high-performance liquid chromatography. Each variable was tested in triplicate. MEASUREMENTS AND MAIN RESULTS: Albuterol delivery was significantly (p < or = .05) greater for the 6.0-mm endotracheal tube, rigid spacer, dry air, and pulmonary disease mechanics by multifactor analysis of variance. Drug delivery in humidified air with pulmonary disease mechanics using the rigid chamber was 2.5 =/- 0.27% and 6.3 =/- 0.99% for the 4.0- and 6.0-mm endotracheal tubes, respectively. CONCLUSIONS: These in vitro results suggest that pulmonary disease mechanics and a 6.0-mm endotracheal tube improve albuterol delivery. Future clinical investigations in intubated pediatric patients with pulmonary disease are needed to address the clinical significance of these results.

Albuterol↗

PubMed1996

Prediction of childhood drowning and near-drowning morbidity and mortality.

OBJECTIVES: (a) Evaluate the presenting hemodynamic status and neurologic function of a series of warm water submersion injuries. (b) To ascertain the importance of the timing of the neurologic examination. (c) To identify risk factors that predict which patients will not return to presubmersion status. DESIGN: Retrospective review of all patients with a diagnosis of drowning/near-drowning responded to by the Children's Hospital pediatric transport service. Data were collected over a 24-month period regarding patient characteristics, submersion medium, rescue efforts, time out of sight, elapsed times to emergency department (ED) and pediatric intensive care unit (PICU) arrival, neurologic and hemodynamic status on arrival at the ED and PICU, reconstructed Conn-Modell category, and neurologic outcome. SETTING: EDs of the referring hospitals and PICU of the Children's Hospital of Orange County (CHOC), California. PATIENTS: Ninety-three submersion victims at an average age of 31 months. All patients were provided intensive care support. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Twenty-three percent (21/ 93) of patients died or survived vegetative. No patient arriving comatose and asystolic in the ED survived neurologically intact (n = 21, three patients expired in the ED). This group of patients had a mean duration of documented asystole = 41 minutes, range of 18 to 107 minutes, and time to ED arrival = 21 minutes. All patients with a detectable pulse and blood pressure (n = 72) on arrival to the ED, regardless of their neurologic status, recovered to their presubmersion status. Patients arriving comatose (decorticate, decerebrate, or flaccid posture) in the PICU (n = 18, mean arrival = 192 minutes) all died or were vegetative. All patients with non-coma (n = 72, Conn-Modell category A or B) on arrival to the PICU recovered normally. CONCLUSIONS: Hemodynamic status in the ED and neurologic status in the PICU are highly predictive of outcome. On arrival to the ED, the cardiovascular status is more predictive of abnormal outcome than neurologic status. Poor neurologic outcome appears inevitable for warm water submersion victims who are asystolic at ED arrival and remain comatose for more than 200 minutes.

Child, Preschool↗

PubMed1992

Dobutamine pharmacokinetics and pharmacodynamics in pediatric intensive care patients.

OBJECTIVE: To evaluate the pharmacokinetics and pharmacodynamics of dobutamine in critically ill children. DESIGN: A prospective study of pediatric patients receiving continuous infusions of dobutamine in a stepwise format from 2.5 to 10.0 micrograms/kg/min. SETTING: A pediatric critical care unit. PATIENTS: Twelve children ranging in age from 1 month to 17 yrs with primary medical conditions. MEASUREMENTS: Plasma dobutamine concentrations and hemodynamic responses were measured at each infusion rate at steady state. Dose response data were analyzed to determine the threshold or minimum plasma dobutamine concentration necessary for discernible hemodynamic effects. MAIN RESULTS: Dobutamine plasma clearance rates ranged from 40 to 130 mL/kg/min. Each patient presented a linear increase in the plasma dobutamine concentration at each infusion rate (r2 = .97, p less than .001). Plasma clearance rate vs. actual dobutamine concentration did not vary. Cardiac output, BP, and heart rate increased 30%, 17%, and 7%, respectively, at maximal dose. The dobutamine concentration thresholds for changes in cardiac output, BP, and heart rate were 13 +/- 6, 23 +/- 14, and 65 +/- 30 ng/mL, respectively. CONCLUSIONS: There was no effect of plasma dobutamine concentration or infusion rate on plasma clearance rate. For this group of patients, over the range of the intravenous doses studied, dobutamine pharmacokinetics followed a first-order kinetic model. Threshold values for dobutamine usually show increases in cardiac output before changes in heart rate. These data demonstrate that dobutamine is an effective inotropic agent in critically ill pediatric patients and has minimal chronotropic action.

Blood Pressure↗

PubMed1991

Pulmonary clearance of norepinephrine in lambs.

The lungs play an important role in the metabolism of vasoactive substances including endogenous amines. The role of pulmonary clearance of circulating norepinephrine has not been well defined in the young lamb (7-8 d of age). Using radiolabeled tracer norepinephrine in acutely instrumented lambs, we determined the in vivo pulmonary clearance and spillover rate of norepinephrine under baseline and hypoxic conditions. The fractional extraction of norepinephrine, the percent removed on a single pass through the pulmonary circulation, was 23 +/- 2%. The corresponding pulmonary clearance rate was 61 +/- 10 mL/kg/min and the net pulmonary norepinephrine removal rate was 0.41 +/- 0.14 nmol/kg/min. This clearance represented over 70% of whole body norepinephrine clearance. The spillover of synaptic norepinephrine was 0.22 +/- 0.13 nmol/kg/min. During hypoxia, animals showed significant increases in pulmonary artery pressure and resistance. Fractional extraction and norepinephrine decreased to 16 +/- 3%, p less than 0.005. Pulmonary clearance decreased to 31 +/- 7 mL/kg/min, and net pulmonary norepinephrine removal rate decreased to 0.27 +/- 0.07 nmol/kg/min. These results demonstrate that pulmonary clearance plays a significant role in norepinephrine clearance in 1-wk-old lambs. Alteration of norepinephrine clearance during physiologic states such as hypoxia may be important in the pathophysiology of altered pulmonary vascular resistance in newborn animals.

Animals↗

PubMed1991

Neonatal adaptation: cardiac adrenergic effector mechanisms after birth in newborn sheep.

At birth, there is a marked increase in circulating plasma catecholamine concentrations. This increase is critical to many of the physiologic adjustments to postnatal life. Because the levels observed are higher than those seen in most other physiologic conditions in adults, previous investigators have suggested that the newborn is less sensitive to adrenergic stimulation or that desensitization to adrenergic stimulation occurs rapidly. To investigate this question, we designed experiments to measure myocardial beta-adrenergic receptor density and sensitivity before and after exposure to the catecholamine surge at birth in term newborn sheep. We also measured the status of sympathetic innervation, reflected by myocardial norepinephrine content. At birth, plasma catecholamines increased 4- to 6-fold with associated increases in heart rate, blood pressure, and cardiac output. Myocardial beta-adrenergic receptor at birth (135 fmol/mg protein) did not change significantly by 6 h of life (157 fmol/mg protein). Myocardial adenyl cyclase activity, reflecting receptor sensitivity, and myocardial sympathetic innervation also did not change. These results suggest that, despite exposure to sustained adrenergic stimulation, myocardial adrenergic effector mechanisms do not change in the newborn sheep at birth.

Adaptation, Physiological↗

PubMed1990

Pharmacokinetics of dopamine in critically ill newborn infants.

Dopamine pharmacokinetics was investigated in 14 critically ill newborn infants ranging from 27 to 43 weeks of gestational age and from 0.9 to greater than 4 kg birth weight. Plasma clearance rate was determined from dopamine levels during controlled infusions under actual clinical conditions. Dopamine was administered in stepwise increasing doses up to 8 micrograms/kg/min. Dopamine concentration and dopamine clearance rate were determined from duplicate samples drawn during each infusion in each patient. Steady-state plasma dopamine concentrations and plasma clearance rates were observed within 20 minutes at each infusion. Plasma dopamine concentration ranged from 0.5 ng/ml before infusion to almost 70 ng/ml at an infusion rate of 4 to 8 micrograms/kg/min. There was a linear correlation between infusion rate and plasma dopamine concentration (r = 0.68, p less than 0.001). Neither plasma dopamine concentration nor infusion rate had a significant effect on clearance rate. These data are consistent with first-order kinetics for administered dopamine in critically ill neonates over the range of concentrations studied.

Birth Weight↗

PubMed1989

Thresholds for the physiologic effects of adrenergic agents: a methodologic appraisal.

For hemodynamic responses to adrenergic agents, classical pharmacodynamic theory describes differences between agents in receptor specificity, potency and pharmacologic profile from derived parameters such as the ED50 or half-maximal concentration. However, pharmacodynamic parameters are derived exclusively from in vitro studies. We describe a method of analysis which permits derivation of the 'threshold' or minimum plasma drug concentration associated with discernible effects. The threshold is derived by graphic analysis of in vivo dose response data. We provide examples of both animal and human data which demonstrate agreement of experimental results with predicted responses. This approach permits more direct comparison of studies from different investigators, from different patient or diagnostic categories or at different developmental ages.

Adrenergic Agonists↗