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Biomedical subjects

S J Phelps

Publications and source records attributed to S J Phelps.

At least 19 recordsLinked to original sources
PubMed1992

Prevalence of, and risk factors for, upper gastrointestinal tract bleeding in critically ill pediatric patients.

OBJECTIVE: To determine the occurrence of, and risk factors for, the development of upper gastrointestinal (GI) tract bleeding in critically ill pediatric patients. DESIGN: Prospective, descriptive, comparative study. SETTING: ICU in a tertiary care pediatric hospital affiliated with a university. PATIENTS: All patients < 19 yrs of age who were admitted to the ICU for a 4-month period (n = 429) were eligible for inclusion. A total of 221 patients were excluded for reasons listed below. Thus, 208 patients were studied. INTERVENTION: None. MEASUREMENTS AND MAIN RESULTS: Patients were evaluated for overt upper GI bleeding as indicated by coffee ground material or bright red blood in gastric aspirates or black, tarry stools. Excluded were patients who were transferred out of the ICU within 24 hrs of admission, were receiving medications that would alter their risk for upper GI bleeding, or had a GI tract surgical procedure. Patients were categorized by diagnoses and analyzed for relative risk for upper GI bleeding. Of the 208 patients included, 25% had evidence of upper GI bleeding. There was no association between upper GI bleeding and age, weight, race, or sex. Diagnoses independently associated with an increased risk for upper GI bleeding were: circulatory shock, an operative procedure > or = 3 hrs in duration, and trauma. No clinically important sequelae were directly attributable to upper GI bleeding in this group of patients; however, intervention with antacids and histamine-2 receptor (H-2) antagonists likely decreased the progression of GI bleeding. CONCLUSIONS: Overt evidence of upper GI bleeding is not uncommon in critically ill pediatric patients. Certain diagnoses or risk factors may predispose these patients to develop upper GI bleeding.

Adolescent↗
PubMed1992

Ability of three pharmacokinetic equations to predict steady-state serum theophylline concentrations in pediatric patients.

The pharmacokinetic equations of Chiou, Koup, and Kurland are often used in the pediatric setting to predict steady-state theophylline clearance using non-steady serum theophylline concentrations. However, these equations have not been validated or compared in a pediatric population. We evaluated the ability of these equations to predict steady-state serum theophylline concentrations in 61 children (0.21-14.3 years) who received a continuous intravenous theophylline (0.79 +/- 0.12 mg/kg/h) infusion for a minimum of five half-lives. Theophylline concentrations used in the Kurland equation were obtained 10.8 +/- 4.5 h after initiation of therapy and the time between the two concentrations used in the Chiou and Koup equations was 9.2 +/- 3.9 h. Predicted steady-state theophylline concentration values for the three methods were not different from each other (p = 0.91), nor were they different from the observed steady-state concentration values (p = 0.92). The coefficient of determination for predicted vs. observed steady-state concentrations was statistically significant (p less than 0.001) and was comparable for the three methods. There was no difference in mean bias (p = 0.78), precision (p = 0.82), or % error (p = 0.86) values for the three methods. Regardless of the method used, 75 to 82% of all predicted theophylline concentrations were within 20% of the observed steady-state value. However, on average, all methods underpredicted the clearance and hence overpredicted the serum theophylline concentration. The Kurland method did not predict steady-state concentrations any better in patients who had received theophylline prior to admission.(ABSTRACT TRUNCATED AT 250 WORDS)

Child↗
PubMed1992

Antipyretic therapy in the febrile child.

General principles of thermoregulation, the pathophysiology of fever, controversies concerning the use of antipyretic therapy, and nonpharmacologic and pharmacologic treatments commonly used for antipyresis in the pediatric population are reviewed. Several arguments can be made for not ameliorating the febrile response. Fever is an important diagnostic and prognostic clinical sign that may have beneficial effects for the host. In addition, body temperatures of < or = 41 degrees C (105.8 degrees F) are relatively harmless. Reasons for treating fever include patient discomfort, the potential for adverse sequelae, the possibility of seizures, and the possibility that fever could affect the pharmacokinetic profiles of drugs. Nonpharmacologic treatment for fever includes environmental measures to enhance dissipation of body heat and sponging. Aspirin and acetaminophen are the agents used most frequently for antipyresis in pediatric patients. However, aspirin use in children with a viral illness has been associated with development of Reye's syndrome. As a result, its use in children has declined in the United States. Acetaminophen is relatively free of adverse effects and is considered first-line pharmacologic antipyresis therapy. Ibuprofen suspension should be considered as second-line antipyretic therapy. Combination therapy with acetaminophen and aspirin may be considered if the patient fails to respond to other nonpharmacologic and pharmacologic therapies; however, combination therapy may result in increased risk of drug toxicity, increased probability of adverse reactions, and increased risk of intoxication. Aspirin, acetaminophen, and ibuprofen are equally effective for antipyresis in pediatric patients. However, because acetaminophen is the safest medication, it is currently the therapy of choice.

Acetaminophen↗
PubMed1991

Determining efficacy of monitoring devices: evaluating new technologies.

We point out the connection between electronic monitoring and repeated screening tests, and suggest a flexible and practical method to determine the efficacy of monitoring devices and new technologies. We point out the benefits of the Mantel-Haenszel estimator of an odds ratio for determining diagnostic test indices. From estimates of sensitivities and specificities, we produce receiver operating characteristic (ROC) curves to compare the performance of two or more monitoring devices in a clinical setting.

Algorithms↗
PubMed1991

Temporal dynamics of pituitary prolactin depletion and release in three strains of rats.

Previous reports have shown that pituitary prolactin is rapidly transformed to a less soluble, but much more releasable, form prior to release from the lactotroph. One manifestation of this transformation is that pituitary prolactin depletion is significantly greater than concurrent release both in vivo and in vitro. The objective of this study was to compare the magnitude and temporal dynamics of depletion and release from pituitaries of ovariectomized estrogen-treated rats of three different strains in vitro to assess the effect of strain on the transformation process. Mature ovariectomized Wistar-Furth (WF), Sprague-Dawley (SD) and Long-Evans (LE) rats (7-10/group) were killed by decapitation 7 days after a single s.c. injection of 100 micrograms of polyestradiol phosphate. The anterior pituitaries were quickly removed and cut into quarters which were incubated for up to 4 hrs in the absence of dopamine or other prolactin secretagogues. Representative fragments from each strain were not incubated but were snap frozen to measure pre-incubation content. Fragments from each strain were removed from incubation at 30, 60, 120, 180 and 240 min for prolactin content measurement. Medium was collected at 30 min intervals and replaced with fresh medium. The experiments were repeated twice. Prolactin in medium and pituitary homogenates was measured by radioimmunoassays using NIAMDD-RP-1 as standard. In all three stains release of prolactin was approximately 30-50% of the prolactin depleted from the pituitary in 4 hrs. Strains varied in the magnitude of this difference and the time course over which it occurred. WF and SD rats showed significantly greater depletion and release of prolactin than did LE rats when the data were expressed as micrograms prolactin/mg pituitary. When the data were expressed as a percentage of prolactin available for release, the differences in depletion between strains disappeared and the LE rats released a significantly greater percentage of the prolactin available for release than did the other two strains. We conclude that pituitary prolactin undergoes a process of transformation prior to release which causes it to disappear from the pituitary but not appear in culture medium. We further conclude that the magnitude and temporal dynamics of this process are not equivalent across all strains of rats.

Animals↗
PubMed1991

Toxicities of parenteral nutrition in the critically ill patient.

Critically ill patients have unique nutritional substrate requirements. Although important advances have been made in understanding these requirements in the face of pathophysiologic and biochemical alterations induced by stress or trauma, nutrition-associated toxicities still occur. The importance of these toxicities to the critically ill patients cannot be over-stated. Many of these toxicities can be avoided by conservative use of selected nutrition substrates in specific subsets of the critically ill population. Practitioners must continue to anticipate and recognize parenteral nutrition-associated toxicities, however, as well as delineate any toxicity from the progression or exacerbation of disease.

Catheters, Indwelling↗
PubMed1991

Effect of an infusion device on the integrity of whole blood and packed red blood cells.

The effects of the Gemini PC-2 linear peristaltic infusion device on the integrity of packed red blood cells (RBC) and whole blood products are reported. Thirty-eight units of blood products were infused at rates of 999, 100, 50, and 5 mL/hr under simulated clinical conditions. To evaluate the effect of hematocrit on cell survival, fresh and stored packed RBCs preserved with adenine-saline 3 (AS-3) and fresh and stored packed RBCs and fresh and stored whole blood preserved with citrate-phosphate-dextrose-adenine 1 (CPDA-1) were used. No two units tested came from the same donor. Plasma potassium and plasma free hemoglobin concentrations were determined before and after simulated infusion for 80 experimental runs. Preinfusion plasma potassium and free hemoglobin concentrations varied significantly among the blood products. Stored products were associated with higher plasma potassium and free hemoglobin levels than fresh units, both before and after infusion. Concentrations also differed significantly between AS-3-preserved and CPDA-1-preserved fresh and stored packed RBCs. Infusion did not change plasma potassium values appreciably under any conditions. Plasma free hemoglobin increased in the fresh products only. Donor-specific differences were significant for potassium but not for free hemoglobin. There was no significant effect of infusion rate on either biochemical marker. In all the experimental runs, less than 0.01% of cells were lysed. The Gemini PC-2 linear peristaltic infusion device delivered a variety of blood products at a wide range of infusion rates without inducing a substantial degree of hemolysis.

Blood Transfusion↗
PubMed1990

Inability of inline pressure monitoring to predict or detect infiltration of peripheral intravenous catheters in infants.

Monitoring of inline intravenous pressure as a method for predicting or detecting infiltration of peripheral catheter sites in infants was evaluated. Inline intravenous pressure was measured every 30 minutes in infants less than 12 months of age who had standardized peripheral catheters through which they were receiving a continuous infusion. Pressure was measured by an inline pressure transducer, and the signal was recorded by a strip chart recorder. Physical activities or manipulations of the patients were recorded simultaneously with each pressure reading. The catheter site was inspected hourly for clinical signs of infiltration. There was no significant difference in baseline or final pressure measurements between patients whose catheter sites became infiltrated (n = 20) and patients whose catheter sites did not (n = 22). Likewise, changes in pressure from baseline did not differ between the infiltrated and noninfiltrated groups. At 12 hours before the final reading, pressures for the infiltrated group did not differ significantly from pressures for the noninfiltrated group, nor did these values differ from the respective baseline values. Over the final 12 hours of catheterization, mean slopes (changes in pressure over time) for the two groups did not differ significantly from 0 or from each other. Intrapatient specificity and sensitivity of the method and the false-alarm rate were clinically unacceptable. Monitoring of inline intravenous pressure is not useful for predicting or detecting infiltration of peripheral catheter sites in infants.

Catheterization, Peripheral↗
PubMed1989

Parenteral nutrition in the critically ill patient.

The metabolic alterations, nutritional and metabolic assessment, and nutritional requirements of critically ill patients are discussed, and parenteral nutrition support therapies are reviewed. Physiological alterations in the metabolism of the injured or septic patient are mediated through the interactions of neuroendocrine, cardiovascular, toxic, and starvation responses. These responses cause mobilization of nutritional substrates in an effort to maintain vital organ function and immune defenses. A patient's nutritional status can be determined from anthropometric measurements, creatinine excretion rate, and evaluations of protein stores and immune reserves and function; body weight is a poor indicator. Nitrogen-balance calculations are also useful for determining the adequacy of nutritional intake and the degree of metabolic stress. Early assessments of nutritional status may assist in identifying those patients for whom nutritional support interventions are needed. Nutritional requirements are altered by the metabolic responses to injury and sepsis. Studies suggest that use of nutrient solutions enriched for branched-chain amino acids may enhance nitrogen retention and that energy expenditures in injured or septic patients are only moderately elevated. Most nonprotein calories in parenteral nutrient solutions are provided as glucose, but lipids are an important source of energy in the critically ill patient who has high energy requirements or carbohydrate intolerance; however, clearance of lipids may be decreased. Fluid, electrolyte, and mineral status must be evaluated frequently. Critically ill patients have unique nutritional requirements, and parenteral nutrition support therapies for these patients are being investigated and refined.

Critical Care↗
PubMed1988

The influence of gestational age and preeclampsia on the presence and magnitude of serum endogenous digoxin-like immunoreactive substance(s).

Digoxin-like immunoreactive substance(s) has been measured in serum during pregnancy. Because of its presence in pregnancy, investigators have suggested that digoxin-like immunoreactive substance may play an etiologic role in the development of preeclampsia. The objectives of this study were to evaluate the relationship between maternal digoxin-like immunoreactive substance and gestational age and compare digoxin-like immunoreactive substance concentrations in patients with and without preeclampsia who were in the third trimester. Two hundred twenty patients were studied during either the first (n = 53), second (n = 56), or third (n = 111) trimester of pregnancy. Digoxin-like immunoreactive substance was undetectable in the serum of patients during the first trimester; however, 11% of second-trimester and 96% of third-trimester patients had measurable levels of serum digoxin-like immunoreactive substance (p less than 0.05). The mean +/- SEM concentration of digoxin-like immunoreactive substance in serum in third-trimester patients was 0.29 +/- 0.01 ng/ml (range 0 to 0.58 ng/ml). Gestational age at delivery was significantly lower in patients with preeclampsia than in those without preeclampsia (36.3 +/- 0.6 versus 38.8 +/- 0.4 weeks; p less than 0.001). In addition, there was no statistical difference in mean +/- SEM concentration of digoxin-like immunoreactive substance between 27 patients without preeclampsia (0.32 +/- 0.02 ng/ml) and 27 patients with preeclampsia (0.30 +/- 0.02 ng/ml; p = 0.47) matched for gestational age. We conclude that (1) digoxin-like immunoreactive substance appearance and increasing serum concentration during pregnancy are correlated with increasing gestational age and (2) there is no difference in digoxin-like immunoreactive substance values between patients with and without preeclampsia, which may exclude digoxin-like immunoreactive substance as a predictor of preeclampsia.

Adolescent↗
PubMed1988

Parenteral nutrition in pediatric patients.

Protein, calorie, fluid, fat, and micronutrient requirements of pediatric patients are reviewed, as are methods of nutritional assessment and complications associated with the use of parenteral nutrition in these patients. In general, preterm infants and neonates require greater per-kilogram amounts of protein, calories, fluid, and micronutrients than older children. In addition, preterm infants and neonates have deficiencies in enzymes that metabolize certain amino acids, making otherwise nonessential amino acids essential. These unique protein needs have been addressed in amino acid formulations designed specifically for this group of patients. Supplying the neonate with the calcium and phosphorus needed for bone growth can be difficult because of solubility limitations in parenteral nutrient solutions. The use of intravenous fat emulsion in infants with hyperbilirubinemia or pulmonary complications is controversial. However, only rarely does fat emulsion have to be completely withheld. Complications associated with parenteral nutrition in pediatric patients include infection, metabolic disorders (cholestasis, bone demineralization), and mechanical problems. Cholestasis induced by parenteral nutrition has been shown to be more common in low-birth-weight infants; however, the precise etiology is unknown and may be multifactorial. Basic requirements necessary to promote growth while pediatric patients are receiving parenteral nutrition have been determined. However, current studies are challenging what were thought to be standards of pediatric parenteral nutrition therapy.

Child↗
PubMed1988

Rocky Mountain spotted fever.

The epidemiology, pathogenesis, clinical features, and treatment of Rocky Mountain spotted fever are reviewed. Rocky Mountain spotted fever is a severe infection caused by Rickettsia rickettsii transmitted to man by various species of ticks. High-incidence areas exist in the southeast and south central United States. Only 60-70% of patients with the disease report a history of tick bite or exposure to tick-infested areas. The disease is initially characterized by fever, headache, gastrointestinal complaints, myalgia, and a generalized rash. In several days generalized vasculitis may lead to periorbital edema and nonpitting edema of the face and extremities. Central nervous system involvement is common. Because signs and symptoms associated with the disease are nonspecific, the diagnosis is often delayed or missed. Traditionally diagnostic confirmation relied on serologic testing, but an indirect fluorescent antibody assay will soon be commercially available. Rocky Mountain spotted fever is usually treated with the rickettsiostatic agents chloramphenicol or tetracycline, but few comparative data on these agents in patients with the disease are available. For patients who cannot tolerate oral medications, intravenous chloramphenicol sodium succinate is the preferred treatment; chloramphenicol is also the drug of choice for children less than eight years of age. Otherwise, oral tetracycline hydrochloride is the drug of choice. Antibiotic therapy should be continued for 7-10 days or until the patient is afebrile for two to five days. All cases of Rocky Mountain spotted fever must be reported to the Centers for Disease Control. The best ways to decrease the morbidity and mortality of the disease are to increase awareness of its signs and symptoms and to prevent exposure to ticks.

Humans↗
PubMed1987

Digoxin-like immunoreactive substance in pregnancy.

Our aims were to determine the potential usefulness of digoxin-like immunoreactive substances in the prediction of preeclampsia, to study the relationship between fetal production of these substances and maternal serum levels, and to evaluate the association between digoxin-like immunoreactive substances and plasma volume findings in preeclamptic pregnancies. Serum digoxin-like immunoreactive substance concentrations were measured in normotensive and preeclamptic pregnant women and in umbilical artery and vein blood samples. None of the patients in the first trimester (n = 53) and 11% of those in the second (n = 56) had detectable levels of this substance. However, 91% of the patients in the third trimester (n = 161) had positive results. The concentrations of digoxin-like immunoreactive substances in the preeclamptic group (n = 78) were significantly (p less than 0.005) lower than those of third-trimester (n = 83) normotensive patients (0.22 +/- 0.12 versus 0.32 +/- 0.15 ng/ml). However, there were no significant differences between the two groups regarding digoxin-like immunoreactive substance concentrations when matched for gestational age (41 patients in each group). Digoxin-like immunoreactive substance concentrations in umbilical vessels were significantly higher (p less than 0.001) than the corresponding maternal levels. Umbilical vessel digoxin-like immunoreactive substance levels demonstrated good correlation with fetal gestational age and birth weight in both normotensive and preeclamptic pregnancies. On the other hand, there was a poor (r = 0.02; p = 0.91) correlation between plasma volume findings and digoxin-like immunoreactive substance concentration. We conclude that the digoxin-like immunoreactive substance level may be of very little value in the prediction of preeclampsia. The presence of digoxin-like immunoreactive substance at greater concentrations in the umbilical cord blood samples suggests the possibility of the fetus as the source of this substance. Digoxin-like immunoreactive substances may not play a major role in plasma volume expansion during pregnancy.

Blood Proteins↗
PubMed1987

Effect of age and serum creatinine on endogenous digoxin-like substances in infants and children.

An apparent digoxin-like immunoreactive substance(s) (DLIS) was evaluated in 374 pediatric patients, 0 to 72 months of age, not receiving digoxin. The relationship between DLIS presence or concentration and age, weight, gender, race, and serum creatinine was investigated. Twenty-seven percent of patients had a positive apparent DLIS concentration (greater than or equal to 0.2 ng/ml). The mean +/- SD concentration of DLIS in the positive group was 0.39 +/- 0.18 ng/ml (range 0.2 to 1.37 ng/ml). Patients in the DLIS-positive group were younger than those in the negative group (P less than 0.01). Although a greater percentage of infants younger than 6 months of age had measurable DLIS, the mean DLIS concentrations, when present, were not significantly different for all age groups (P greater than 0.05). No significant relationship was found between race or gender and DLIS. A weakly positive correlation between serum creatinine concentration and DLIS was noted (r = 0.22, P less than 0.03), but elevated serum creatinine measurements (greater than 0.6 mg/dL) did not correlate with DLIS concentration. These results support the hypothesis that the presence of DLIS is age related, but DLIS appears to be present in a much larger and older population of pediatric patients than previously reported.

Aging↗
PubMed1987

Risk factors affecting infiltration of peripheral venous lines in infants.

The influence of 11 variables on the infiltration of peripheral venous lines (PVLs) was evaluated during 151 infusions in patients younger than 1 year of age. Infusions were followed from the time of cannula placement to discontinuation. Fifty-eight percent of PVLs were infiltrated by 36.30 +/- 33.53 hours (mean +/- SD; median 40 hours, range 10 to 187 hours). No difference between infiltrated and noninfiltrated PVLs was noted with regard to patient age, gender, weight, cannula type, cannula gauge, cannula site, infusion device, potassium or dextrose concentration, medications, or rate of solution administration (P greater than 0.05). Infiltration was observed more often in black than in white infants (P = 0.03) and in patients with lower controller solution head heights (P = 0.01). The time to infiltration was decreased significantly for steel verus Teflon cannulas (P = 0.02), for administration of intravenous medication versus no administration of medication (P = 0.03), for peripheral parenteral nutrition solutions compared with 5% or 10% dextrose solutions (P = 0.014), and with increasing cannula gauge (P = 0.05). The time to infiltration did not differ significantly for gravity-controlled versus positive-pressure infusion device delivery (P = 0.51) or for potassium concentrations less than or equal to 20 mEq/L versus greater than 20 mEq/L (P = 0.13). Infusion device occlusion alarms were associated with only 19% of infiltrations. No sloughing of skin or necrosis of tissue occurred related to infiltration.

Black or African American↗