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Biomedical subjects

A M Harrison

Publications and source records attributed to A M Harrison.

At least 19 recordsLinked to original sources
PubMed2005

Resective surgery to treat refractory status epilepticus in children with focal epileptogenesis.

Prolonged high-dose suppressive therapy (HDST) is a mainstay in the management of refractory status epilepticus (RSE), albeit with high morbidity and mortality. The authors studied 10 patients who were carefully selected for epilepsy surgery after failing prolonged (>2 weeks) HDST. Status epilepticus was stopped acutely in all of them with no mortality and no substantial morbidity. At follow-up (median 7 months), 7 (70%) of 10 patients were seizure free, and 3 (30%) of 10 had significant improvement in their epilepsy.

Adolescent↗
PubMed2001

Pharmacokinetics and pharmacodynamics of ranitidine in critically ill children.

OBJECTIVE: To determine the pharmacokinetics and pharmacodynamics of ranitidine in critically ill children and to design a dosage regimen that achieves a gastric pH > or =4. DESIGN: Prospective, open-label, pharmacokinetic-pharmacodynamic study. SETTING: Pediatric intensive care unit in a tertiary care children's hospital. PATIENTS: Mechanically ventilated, critically ill children > or =10 kg who required intravenous ranitidine for stress ulcer prophylaxis. INTERVENTIONS: Ranitidine pharmacokinetics were determined after a single intravenous dose. Gastric pH was monitored hourly via nasogastric pH probe. After the last blood sample, patients received an intravenous bolus of ranitidine (0.5 mg/kg) followed by a continuous infusion (0.1 mg x kg(-1) x hr(-1)). The infusion was increased incrementally (0.05 mg x kg(-1) x hr(-1)) until reaching gastric pH > or =4 for > or =75% of a 24-hr period, after which steady-state plasma concentrations were measured. Plasma concentrations were analyzed by high-pressure liquid chromatography. MEASUREMENTS AND MAIN RESULTS: Twenty-three children (ranging in age from 1.4 to 17.1 yrs) were studied. Pharmacokinetic variables included a clearance of 511.7 +/- 219.7 mL x kg(-1) x hr(-1), volume of distribution of 1.53 +/- 0.99 L/kg, and half-life of 3.01 +/- 1.35 hrs. After the single intravenous dose (1.52 +/- 0.47 mg/kg), gastric pH increased from 1.6 +/- 1.0 to 5.1 +/- 1.1 (p <.001), which was associated with a plasma concentration of 373 +/- 257 ng/mL. Based on the pharmacokinetic variables, the dose of intravenous ranitidine required to target 373 ng/mL as the average steady-state concentration is 1.5 mg/kg administered every 8 hrs. During the continuous infusion, the mean steady-state ranitidine concentration associated with gastric pH > or =4 was 287 +/- 133 ng/mL. This concentration may be achieved with an intravenous loading dose of 0.45 mg/kg followed by a continuous infusion of 0.15 mg x kg(-1) x hr(-1). CONCLUSIONS: The pharmacokinetics of ranitidine in critically ill children are variable. The description of ranitidine's pharmacokinetics and pharmacodynamics in this study may used to design an initial ranitidine dosage regimen that targets a gastric pH > or =4. Thereafter, gastric pH should be monitored and the dose of ranitidine adjusted accordingly.

Adolescent↗
PubMed2001

Effect of RSV bronchiolitis practice guidelines on resource utilization.

We sought to determine whether institution of respiratory syncytial virus (RSV) practice guidelines decreased resource utilization for a heterogeneous population of children hospitalized with RSV bronchiolitis. Patients less than 24 months old with RSV bronchiolitis at a pediatric referral center were identified by retrospective chart review for consecutive RSV seasons. Before the guidelines were instituted patients were less likely to have a documented physician's assessment of response to albuterol, were more likely to have received supplemental oxygen and cardiorespiratory monitoring, and to be discharged on an albuterol regimen. Patients received more albuterol treatments. After the guidelines were in place fewer resources were utilized in the care of patients with RSV bronchiolitis. RSV practice guidelines may simplify and streamline the care of a heterogeneous population of children with bronchiolitis.

Adrenergic beta-Antagonists↗
PubMed2000

Modified Norwood procedure with a high-flow cardiopulmonary bypass strategy results in low mortality without late arch obstruction.

OBJECTIVE: The results of our modification of the stage I Norwood procedure, in which we use only autologous tissue to reconstruct the aortic arch, were reviewed. A high-flow, low-pressure cardiopulmonary bypass protocol (with phenoxybenzamine), before and after a period of deep hypothermic circulatory arrest, was used. METHODS: Between 1993 and 1999, 59 patients, aged 1 to 353 days (median 4 days) and weighing 1.7 to 6.8 kg (median 3.2 kg), underwent a modified Norwood procedure. The ascending aortic diameter ranged from 1.5 to 8 mm (median 3 mm). The modified Blalock-Taussig shunt was 3 mm in 21 patients (36%) and 3.5 mm or larger in 38 patients (64%). RESULTS: Deep hypothermic circulatory arrest and cardiopulmonary bypass times ranged from 15 to 64 minutes (median 37 minutes) and 44 to 144 minutes (median 88 minutes), respectively. Early postoperative survival was 83%. By univariate analysis, early mortality was associated with an ascending aortic diameter of 2.5 mm or less (P =.01). Weight, circulatory arrest and bypass times, diagnosis (hypoplastic left heart syndrome vs variant), shunt size, and date of the procedure did not affect survival. For a median follow-up period of 37 months (range 4-63 months), 42 (61%) patients underwent bidirectional cavopulmonary shunts, 10 (17%) had Fontan operations, and 1 patient underwent transplantation after a bidirectional cavopulmonary shunt. Eight patients subsequently died, for a 1-year actuarial survival of 72% (95% confidence interval: 60%-84%). Neoaortic arch obstruction was corrected in 3 patients (5%). CONCLUSIONS: At intermediate-term follow-up, our modification of the Norwood procedure together with our perioperative strategies has resulted in acceptable outcomes with a low incidence of neoaortic arch obstruction. Patients with a small ascending aortic diameter have emerged as a high-risk group, but a recent technical modification may improve the outlook for these patients.

Aorta, Thoracic↗
PubMed1999

Respiratory syncytical virus-induced chemokine expression in the lower airways: eosinophil recruitment and degranulation.

Characterization of chemokine expression patterns in virus-infected epithelial cells provides important clues to the pathophysiology of such infections. The aim of this study was to determine the chemokine response pattern of respiratory epithelium when infected with respiratory syncytial virus (RSV). Macrophage inflammatory protein-1-alpha (MIP-1-alpha), interleukin-8 (IL-8), and RANTES concentrations were measured from RSV-infected HEp-2, MRC-5, and WI-38 cell culture supernatants daily following infection. Additionally, MIP-1-alpha, IL-8, and RANTES concentrations were measured from lower respiratory secretions obtained from 10 intubated infants (0-24 mo) with RSV bronchiolitis, and from 10 control subjects. Our results indicate that respiratory epithelial cells respond to RSV infection by producing MIP-1-alpha, IL-8, and RANTES. Production of MIP-1-alpha required ongoing viral replication, whereas RANTES and IL-8 could be elicited by inactivated forms of the virus. MIP-1-alpha, RANTES, and IL-8 were also present in lower airway secretions obtained from patients with RSV bronchiolitis. Eosinophil cationic protein (ECP) and eosinophil-derived neurotoxin (EDN), the eosinophil secretory ribonucleases, were detected in lower airway secretions from RSV-infected patients; ECP concentrations correlated with MIP-1-alpha concentrations (r = 0.93). We conclude that MIP-1-alpha is present in the lower airways during severe RSV disease. The correlation between MIP-1-alpha and ECP concentrations suggests a role for eosinophil degranulation products in the pathogenesis of RSV bronchiolitis.

Blood Proteins↗
PubMed1999

Can pediatricians define and apply the concept of brain death?

OBJECTIVE: We sought to determine pediatric residents' and attending physicians' ability to define brain death, their ability to apply this standard of death to a clinical scenario, and their knowledge regarding the legal necessity of confirmatory testing when determining death by brain criteria. We compared resident and attending self-confidence at discussing brain death with their ability to define brain death and apply this concept to a clinical scenario. METHODOLOGY: A questionnaire was sent to 136 residents, postgraduate years 1 through 3, at four accredited pediatric training programs in the United States. Participation was tracked by return address. One follow-up request for participation was made. A similar procedure was followed for 140 faculty pediatricians at two of the institutions. Demographic information including level of training, subspecialty training, training program, and formal ethics training was collected. Respondents defined brain death, interpreted a clinical scenario, and stated whether confirmatory testing is legally required to determine death by brain criteria. Respondents rated their confidence at explaining brain death to a patient's family on a scale from 1 to 5. RESULTS: Eighty-seven percent (118/136) of resident surveys were returned. Thirty-six percent (42/118) of the residents correctly defined brain death. Forty-three percent (51/118) of residents correctly interpreted the clinical scenario. Fifty-five percent (65/118) of the residents correctly recognized that brain death could be determined without a confirmatory test. Residents who correctly defined brain death were as confident as those who did not (2.8 +/- 1 vs 1.5 +/- 1). Residents who correctly interpreted the clinical scenario were as confident as those who did not (2.6 +/- 1 vs 1.9 +/- 0.9). Eighty percent (112/140) of attending physician surveys were returned. Thirty-nine percent (44/112) of attending physicians correctly defined brain death. Fifty-three percent (59/112) correctly interpreted the clinical scenario. Fifty-eight percent (65/112) recognized that brain death can be diagnosed without confirmatory testing. All pediatric intensivists (n = 12) correctly answered all three questions. Their performance was significantly better than other pediatricians. Attendings who correctly defined brain death were more confident than those who did not (4.2 +/- 1 vs 1.1 +/- 0. 9). Attendings who correctly interpreted the clinical scenario were more confident than those who did not (3.8 +/- 1.2 vs 2.2 +/- 1.2). CONCLUSIONS: Pediatric residents and attendings have difficulty defining and applying the concept of brain death. This concept is difficult to grasp and internalize for many pediatricians. To ensure that critical decisions are made by knowledgeable physicians and well-informed families, more effective educational strategies need to be identified.

Brain Death↗
PubMed1998

Gastric pH control in critically ill children receiving intravenous ranitidine.

OBJECTIVE: To determine whether the dose of ranitidine recommended in commonly used pediatric drug dosage handbooks (2 to 4 mg/kg/day i.v.) results in successful gastric pH control (pH of >4) in critically ill children. DESIGN: Prospective sample. SETTING: Pediatric intensive care unit in a tertiary care children's hospital. PATIENTS: Fifty consecutive patients who received >24 hrs of scheduled intermittent intravenous ranitidine for stress ulcer prophylaxis were enrolled in the study. Patients with renal or hepatic dysfunction and those who received enteral nutrition through the nasogastric tube were excluded from enrollment. INTERVENTION: Gastric pH was determined at the end of the ranitidine dosing interval, 1 hr after the dose, and at the midpoint between doses. All pH measurements were made from a sample of nasogastric aspirate, using pH sensitive paper. Gastric pH control with ranitidine was considered unsuccessful (poorly controlled) if the pH was <4 for any of the three measurements. MEASUREMENTS AND MAIN RESULTS: Forty-five patients (median age 36 mos; range 2 wks to 264 mos) were included in the analysis. Eighty-two percent of the patients were mechanically ventilated, 16% were pharmacologically paralyzed, 18% required vasoactive infusions, 36% were nourished via transpyloric feeding tubes, and 7% received total parenteral nutrition. Gastric pH was poorly controlled in 36% of patients. Among these patients, the pH at the end of the dosing interval was significantly lower than the pH measured at 1 hr or at the midpoint between doses (p < .05). Seventy-one percent of patients who received <3 mg/kg/day of ranitidine had poor gastric pH control as compared with 19% who received a minimum of 3 mg/kg/day (p< .05). Poor control of gastric pH was not associated with feeding, intubation status, presence of pharmacologic paralysis, use of vasoactive infusions, or age (p > .05). CONCLUSIONS: The minimum ranitidine dose recommended in commonly used pediatric drug references resulted in unsuccessful gastric pH control in a high percentage of pediatric intensive care unit patients. Critically ill children with normal renal and hepatic function should be treated with a minimum 3 mg/kg/day of intravenous ranitidine and the dose should be titrated to a gastric pH of > or =4.

Child↗
PubMed1998

Non-interpretive mechanisms in psychoanalytic therapy. The 'something more' than interpretation. The Process of Change Study Group.

It is by now generally accepted that something more than interpretation is necessary to bring about therapeutic change. Using an approach based on recent studies of mother-infant interaction and non-linear dynamic systems and their relation to theories of mind, the authors propose that the something more resides in interactional intersubjective process that give rise to what they will call 'implicit relational knowing'. This relational procedural domain is intrapsychically distinct from the symbolic domain. In the analytic relationship it comprises intersubjective moments occurring between patient and analyst that can create new organisations in, or reorganise not only the relationship between the interactants, but more importantly the patient's implicit procedural knowledge, his ways of being with others. The distinct qualities and consequences of these moments (now moments, 'moments of meeting') are modelled and discussed in terms of a sequencing process that they call moving along. Conceptions of the shared implicit relationship, transference and countertransference are discussed within the parameters of this perspective, which is distinguished from other relational theories and self-psychology. In sum, powerful therapeutic action occurs within implicit relational knowledge. They propose that much of what is observed to be lasting therapeutic effect results from such changes in this intersubjective relational domain.

Countertransference↗
PubMed1997

Comparison of simultaneously obtained arterial and capillary blood gases in pediatric intensive care unit patients.

OBJECTIVE: To determine whether capillary blood gas measurements provide a clinically acceptable estimate of arterial pH, PCO2, and PO2. DESIGN: Prospective convenience sample. SETTING: Pediatric intensive care unit at a referral children's hospital. PATIENTS: Fifty children > 1 month of age with indwelling arterial catheters. INTERVENTIONS: A local anesthetic was applied to the third finger of the hand contralateral to a radial artery catheter. After 90 mins, simultaneous arterial and capillary blood gases were drawn. MEASUREMENTS AND MAIN RESULTS: Arterial and capillary pH, PcO2, and PO2 were measured. Heart rate and Wong/Baker faces score were noted before and during capillary blood gas collection to assess discomfort associated with blood collection. There was a strong correlation between capillary and arterial pH (r2 = .903, p < .0001). The relative average bias of the capillary pH was 0.009, with capillary lower than arterial and 95% limits of agreement of +/- 0.032. In all patients, the absolute value of the difference between arterial and capillary pH was < or = 0.05. There was a strong correlation between arterial and capillary PCO2 (r2 = .955, p < .0001). The relative average bias of the capillary PCO2 was 1.6 torr (0.21 kPa), with capillary higher than arterial and 95% limits of agreement of +/- 4.5 torr (+/- 0.6 kPa). In two of 50 patients, the absolute value of the difference between arterial and capillary PCO2 was > 6.5 torr (> 0.87 kPa). Despite a statistically significant correlation between capillary and arterial PO2 (r2 = .358, p < .0001), the absolute value of the difference between arterial and capillary PO2 was > 6.5 torr (> 0.87 kPa) in 42 of 50 patients. Pain, endotracheal intubation, vasoactive drips, or pharmacologic paralysis did not affect accuracy of the capillary pH or PCO2. CONCLUSIONS: Capillary blood gases accurately reflect arterial pH and PCO2 in most pediatric intensive care unit patients. Capillary samples did not significantly underestimate arterial hypercarbia or acidosis. This conservative reflection of metabolic status may be particularly useful in hemodynamically stable patients with mild-to-moderate lung disease.

Acidosis↗
PubMed1997

Nonradiographic assessment of enteral feeding tube position.

OBJECTIVE: To determine whether a clinical, nonradiographic criterion can be used to predict when the tip of a blindly placed feeding tube is in the small intestine. DESIGN: Prospective sample. SETTING: Pediatric intensive care unit at a tertiary care children's hospital. PATIENTS: Critically ill children requiring transpyloric feeding. INTERVENTIONS: The small bowel was intubated, using a blind, bedside transpyloric feeding tube placement protocol. The feeding tube was considered to be in the small bowel when <2 mL of a 10- mL aliquot of insufflated air could be aspirated from the feeding tube. This clinical criterion was confirmed with an abdominal radiograph. MEASUREMENTS AND MAIN RESULTS: Patient age ranged from 1 month to 19 yrs (median 6 months). Weight ranged from 2.2 to 60 kg (median 4.9). Median time to feeding tube placement was 10 mins (range 5 to 60). Eighty-nine percent of the patients were mechanically ventilated, while 28% of these patients were pharmacologically paralyzed. Seventy-five feeding tubes were inserted. There were no known complications. Ninety-nine (74/75) percent of the feeding tubes were positioned in the small bowel. The inability to aspirate insufflated air correctly predicted small bowel intubation with 99% certainty (Sequential Probability Ratio Test, p = .05 and power = .80). This test incorrectly predicted the position of only one feeding tube, the 26th, which was in the stomach. Of the 74 feeding tubes positioned in the small bowel, 13 feeding tubes were in the duodenum and 61 were in the jejunum. CONCLUSIONS: The inability to aspirate insufflated air confirms the transpyloric position of a feeding tube. Other clinical criteria did not successfully predict small bowel intubation. Use of this single test may obviate confirmatory abdominal radiographs in carefully selected patients and may lead to more cost-effective and timely initiation of enteral feedings.

Adolescent↗
PubMed1997

Treatment of convulsive status epilepticus with propofol: case report.

INTRODUCTION: Convulsive status epilepticus (CSE) refractory to treatment with benzodiazepines, phenobarbital, and phenytoin presents a challenge to pediatric emergency and critical care specialists. Prompt seizure control may prevent mortality and morbidity. CASE: A nine-month-old girl with hereditary fructose intolerance had prolonged, refractory CSE. Her seizures promptly stopped after administration of propofol (3 mg/kg bolus followed by infusion of 100 micrograms/kg/min). This dose resulted in electroencephalographic burst suppression. She required endotracheal intubation, invasive hemodynamic monitoring, and pressor support. DISCUSSION: This is the first pediatric case of prolonged, refractory CSE treated with propofol. The adult experience is reviewed. Propofol should be used only in a setting where definitive airway control and hemodynamic support is possible.

Adult↗
PubMed1994

Fluoroscopic foley catheter removal of esophageal foreign bodies in children: experience with 415 episodes.

OBJECTIVE: This study sought to investigate the safety and efficacy of the fluoroscopic Foley catheter technique (FFCT) for removal of esophageal foreign bodies (EEBs) in children, and to identify factors associated with decreased success. DESIGN/SETTING/PATIENTS: An 11-year retrospective review of all pediatric patients undergoing the FFCT for removal of EFBs at a tertiary-care children's hospital was performed. RESULTS: Four-hundred and fifteen cases are reported. The median age was 29 months (range, 4 to 193); children < or = 24 months accounted for 45% (185) of the cases. Of all episodes 86% (355) involved children without known esophageal pathology. Coins comprised 76% (316) of the EFBs. The FFCT was successful in 91% (378) of the cases. In the 60 episodes involving children with underlying esophageal pathology, the technique had an 83% success rate compared to 92% in children without known pathology (P < .05). There were 290 patients where the duration of impaction was known. The success rate was 96% if the duration was 3 days or less compared to 50% if the duration was longer (P < .0001). Though the overall success in children < or = 24 months was less than older children (88% vs 94%, P < .05), this effect disappeared when corrected for duration of impaction. Minor complications occurred in 2% of the episodes, and major complications were noted in 1%. CONCLUSIONS: The FFCT appears to be a safe and effective method for removal of EFBs especially in children without underlying esophageal lesions and a duration of impaction < or = 3 days. Major complications are rare.

Catheterization↗
PubMed1991

Structure of 3-methyl-1,2,3,4,5,6-hexahydro-1,6-methano-3-benzazocinium hydrogen oxalate.

C13H18N+.C2HO4-, Mr = 277.3, orthorhombic, P2(1)2(1)2(1), a = 5.752 (1), b = 15.502 (2), c = 15.910 (2) A, V = 1418.6 (6) A3, Z = 4, Dx = 1.298 g cm-3, Mo K alpha (lambda = 0.71069 A), mu = 1.01 cm-1, F(000) = 592, T = 295 K. Final R = 0.035, wR = 0.042 for 1003 reflections with I greater than 3 sigma(I). The compound is an ammonium hydrogen oxalate. Both O atoms of the ionized carboxyl group act as acceptors in the formation of two hydrogen bonds: (a) an N--H...O bond linking the cation and anion with N...O and H...O distances of 2.722 (4) and 1.78 (5) A and (b) a strong O--H...O bond linking a chain of oxalate ions along a with O...O and H...O distances of 2.578 (4) and 1.59 (6) A. The relative stereochemistry of the heterocyclic and aromatic rings in the cation is similar to that in morphine.

Analgesics, Opioid↗
PubMed1990

Adventure in the outdoors. Its importance in the development of an adolescent boy.

This exploration of how the analyst works uses a 15-year-old boy's description of an adventure in the outdoors as the starting point for a sequence of associations which led first to a passage from a Wordsworth poem and then to memories from the analyst's own childhood. The related themes of rite of passage and adolescent mourning are elaborated.

Adolescent↗
PubMed1985

Parathyroid adenomas evaluated by Tl-201/Tc-99m pertechnetate subtraction scintigraphy and high-resolution ultrasonography.

Thallium-201/technetium-99m pertechnetate subtraction scintigraphy of the parathyroid glands was performed in a prospective study of 33 patients who had undergone bilateral neck exploration for elevated serum calcium and serum parathyroid hormone levels. In 31 cases, the Tl-201/Tc-99m subtraction technique yielded an overall sensitivity of 81%, specificity of 99%, and accuracy of 94% for identifying solitary parathyroid adenomas. Tl-201/Tc-99m subtraction scintigraphy correctly identified 73% of parathyroid adenomas weighing less than 499 mg, 79% of those weighing 500-1,499 mg, and 100% of adenomas weighing more than 1,500 mg. In a subgroup of 24 patients with solitary parathyroid adenomas who underwent both scintigraphy and high-resolution sonography, the sensitivity, specificity, and accuracy of both procedures were similar.

Adenoma↗