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Biomedical subjects

J L Falk

Publications and source records attributed to J L Falk.

At least 55 records · Page 3Linked to original sources
PubMed1995

Reliability of infrared tympanic thermometry in the detection of rectal fever in children.

STUDY OBJECTIVE: Recently published clinical guidelines for the management of febrile children are based on studies that used rectal temperature data to stratify the risk of bacteremia and septic complications. Appropriate management decisions rely on accurate detection and categorization of fever. Accordingly, this study compared the newer infrared tympanic thermometry (ITT) to rectal thermometry in this regard. DESIGN: Prospective observational study. SETTING: Urban teaching hospital ED with annual census of 60,000. PARTICIPANTS: Consecutive children 6 months to 6 years old who had rectal temperatures measured. INTERVENTIONS: Triage nurses recorded rectal temperatures and bilateral ITT temperatures. Temperatures were correlated by Pearson correlation coefficients and compared using paired t tests with significance set at P < .01. Children were categorized by degree of fever using rectal temperature (afebrile, less than 100.4 degrees F; low fever, 100.4 to 102.9 degrees F; and high fever, more than 102.9 degrees F), and the accuracy of ITT in detecting fever and high fever was determined. RESULTS: Three hundred seventy patients were enrolled in the study. The mean age was 18.4 +/- 11.3 months; boys comprised 56% of patients. The mean temperatures were rectal, 101.0 +/- 2.0 degrees F; right tympanic membrane, 100.4 +/- 1.9 degrees F; and left tympanic membrane, 100.3 +/- 1.9 degrees F. The tympanic membrane temperatures were significantly lower than rectal readings (P << .001 for both right and left versus rectal). Rectal temperatures showed good correlation with both right and left tympanic membrane temperatures (r = .83 and .85, respectively). ITT was 76% sensitive and 92% specific in detecting fever of 100.4 degrees F or more (positive predictive value, 0.92; negative predictive value, 0.76). In the detection of high fever, ITT was only 57% sensitive but 98% specific (positive predictive value, 0.90; negative predictive value, 0.90). Rectal and TM temperatures differed by at least 0.5 degree F in 70% of the patients, 1.0 degree F in 41%, 2.0 degrees F in 12%, and 3.0 degrees F in 3%. CONCLUSION: Despite the statistical correlation between ITT and rectal temperatures, the modalities may yield significantly different temperatures. The poor sensitivity of ITT in detecting fever and high fever may result in clinically important miscategorizations of individual patients. Current clinical management that is based on the presence and height of fever may be adversely affected if ITT is used.

Child↗
PubMed1995

Cerebrospinal fluid shunt complications: an emergency medicine perspective.

Shunt malfunction and shunt infections are the most significant complications associated with cerebrospinal fluid shunts. Most cases of shunt infection are due to S. epidermidis or S. aureus. Seventy percent of all shunt infections present within two months of the shunt surgery. The most common factor associated with shunt infection is age under three months. Even fever may not be a consistent sign of shunt infection. A high index of suspicion for shunt infection or malfunction must be maintained when evaluating the patient with a cerebrospinal fluid shunt. There are many types of shunt systems in use today. An understanding of current shunt systems and their associated problems should allow physicians to promptly diagnose and initiate treatment for patients with cerebrospinal fluid shunts. Prompt neurosurgical consultation is mandatory whenever shunt malfunction or infection is suspected.

Anti-Bacterial Agents↗
PubMed1994

Acute and chronic nicotine effects on multiple-schedule behavior: oral and SC routes.

For rats responding on a 3 h FI 4 min FR 20 schedule of food reinforcement, presession SC nicotine doses (0.1-0.8 mg/kg) produced depression in all responding followed by stimulation of FI responding that was dependent upon both time and dose. With daily presession 0.8 mg/kg SC nicotine injections for 9 days, no tolerance to the depressive or stimulatory effects of nicotine occurred. When nicotine solutions were orally self-administered by presession exposure to 3 h of schedule-induced polydipsia, the subsequent FR responding was unaffected, but the degree of FI response stimulation and its duration occurred in a dose-related fashion (1.18-4.10 mg/kg). Prolonged daily sessions of oral nicotine self-administration provide a technique for investigating the effects of chronic exposure to nicotine. The postingestive effects of nicotine reveal stimulatory effects that last for at least 3 h.

Administration, Oral↗
PubMed1994

Tolerance to oral and IP caffeine: locomotor activity and pharmacokinetics.

Locomotor activity increase was a bitonic function of acute caffeine IP doses (2.5-40 mg/kg) in rats. When the schedule-induced polydipsic, orally self-administered dose of caffeine was increased over blocks of daily 3 h sessions from 9.3 to 36.5 mg/kg, postsession activity increased monotonically as a function of dose. The rate of tolerance development to the increase in locomotor activity produced by caffeine depended on the route of administration. Tolerance onset occurred on the fourth day of chronic IP doses, but remained incomplete after 21 doses. With the highest dose level of oral caffeine self-administration, tolerance developed on day 13, but remained incomplete even after 17 doses. Acute tolerance occurred for each of the IP doses, whereas a linear relation between locomotor activity and serum caffeine concentration was obtained after oral self-administration. There were two- to threefold higher locomotor activity AUCs(4 h) with oral caffeine at three dose levels compared to the activity AUCs(4 h) for IP doses.

Administration, Oral↗
PubMed1994

End-tidal carbon dioxide during extremely low cardiac output.

STUDY OBJECTIVE: A number of studies have shown that expired CO2 concentration is closely related to cardiac output, but that cardiac output was not controlled as an independent variable. In addition, the partial pressure of end-tidal CO2 (PETCO2) during extremely low cardiac output has not been reported. The objective of the present study was to measure PETCO2 during well-controlled, very low blood flow rates under conditions of constant minute ventilation. DESIGN: Ten anesthetized, intubated, and mechanically ventilated swine (weight, 43 to 102 kg) were placed on two ventricular assist devices in order to control cardiac output. Minute ventilation was measured and kept constant. Ventricular assist device output (measured with an ultrasonic flow probe); PETCO2; and aortic, pulmonary artery, and central venous pressures were recorded continuously. INTERVENTIONS: After electrical induction of ventricular fibrillation, pump output was decreased in steps. MEASUREMENTS AND MAIN RESULTS: Cardiac index ranged from 0 to 5,371 mL/min/m2; 59% of PETCO2 measurements were made at cardiac indexes of less than 1,313 mL/min/m2 (30 mL/min/kg). The relationship of PETCO2 levels to cardiac index was determined with linear regression analysis; P < .05 was statistically significant. PETCO2 correlated significantly with cardiac index (P < .0001). The best-fit line by least-squares analysis produced the equation: PETCO2 = 4.98 + 0.012 [cardiac index] (r2 = .82). CONCLUSION: Under conditions of constant minute ventilation, PETCO2 correlated closely with cardiac index over a large range of blood flow rates, including extremely low rates.

Animals↗
PubMed1994

Effect of ventilation on acid-base balance and oxygenation in low blood-flow states.

OBJECTIVES: To investigate how minute ventilation affects the partial pressure of end-tidal CO2 and arterial and mixed venous pH, PCO2, PO2, and the concentration of bicarbonate during low blood-flow states. We tested the null hypothesis that acid-base conditions during low rates of blood flow are not significantly different when minute ventilation is doubled or halved. DESIGN: Prospective, experimental, animal study. SETTING: University hospital laboratory. SUBJECTS: Domestic swine. INTERVENTIONS: We studied ten anesthetized and mechanically ventilated swine (weight, 43 to 102 kg) in a new model of controlled systemic and pulmonary blood flow in which each animal was maintained on ventricular assist devices. After electrical induction of ventricular fibrillation, ventricular assist device blood flow was decreased in steps. At each decrease, control minute ventilation, two times the control minute ventilation (hyperventilation), and one-half the control minute ventilation (hypoventilation) were administered; each ventilatory change was maintained for 6 mins. MEASUREMENTS AND MAIN RESULTS: Aortic, pulmonary arterial and central venous pressures, ventricular assist device blood flow, and end-tidal CO2 were recorded continuously. Acid-base conditions were studied at three different mean blood flow rates: 49%, 30%, and 12% of baseline prearrest cardiac index. Arterial pH and PaO2 and mixed venous pH varied directly (p < .003) with minute ventilation, while PaCO2 and mixed venous PCO2, and end-tidal CO2 varied inversely (p < .0001) with minute ventilation. Mixed venous PO2 was not significantly related to minute ventilation (p = .6). PaCO2 and arterial bicarbonate; mixed venous pH, mixed venous PO2, and mixed venous bicarbonate, and end-tidal CO2 varied directly (p < .001) with blood flow, while mixed venous PCO2 varied inversely with blood flow (p < .05). Arterial pH was not significantly related to blood flow (p = .3). When minute ventilation changed from hyperventilation to hypoventilation at a mean blood flow rate of 49%, mean arterial pH decreased 0.22 +/- 0.06 (p < .05), mean PaCO2 increased 28 +/- 6 torr (3.7 +/- 0.8 kPa) (p < .05), and mean PaO2 decreased 99 +/- 77 torr (13.2 +/- 10 kPa); mean mixed venous pH decreased 0.11 +/- 0.02, mean mixed venous PCO2 increased 16 +/- 2.2 torr (2.1 +/- 0.3 kPa) (p < .05), and mean mixed venous PO2 did not change; mean end-tidal CO2 increased 18 +/- 2 torr (2.4 +/- 0.3 kPa) (p < .05). The effect of changes in minute ventilation on blood gases and end-tidal CO2 was similar for mean blood flow rates of 30% and 12% of baseline cardiac index. CONCLUSIONS: During low rates of blood flow similar to those rates found in shock and cardiopulmonary resuscitation, alterations in minute ventilation significantly influenced end-tidal CO2 and both arterial and mixed venous pH and PCO2. These findings may have clinical importance in improving the treatment of shock and cardiac arrest.

Acid-Base Equilibrium↗
PubMed1993

Dexamethasone as adjuvant therapy for severe acute pharyngitis.

STUDY OBJECTIVE: To determine the efficacy of dexamethasone as adjuvant therapy to improve pain relief in patients with severe, acute exudative pharyngitis. DESIGN: Prospective, randomized, double-blinded, placebo-controlled clinical trial. SETTING: Large, urban community hospital emergency department with an emergency medicine residency program. TYPE OF PARTICIPANTS: Patients aged 12 to 65 years old with exudative pharyngitis and severe dysphagia/odynophagia. Patients with cancer, AIDS, diabetes mellitus, recent steroid use, pregnancy, or suspicion of peritonsillar abscess were excluded. INTERVENTIONS: All patients received oral penicillin (500 mg Pen VK) or erythromycin (333 mg base) three times daily for ten days in addition to either 10 mg single-dose dexamethasone or saline placebo IM injection. MEASUREMENTS AND RESULTS: Fifty-eight patients graded their initial degree of throat pain on a visual-analog scale that was 15 cm long and scored from 0 to 3.0 in 0.5-cm increments. Follow-up was obtained on 51 patients to determine their condition at 24 hours. At entry, there was no difference in age, weight, antibiotic assignment, or initial pain score between groups. Improvement in pain score (initial versus 24 hours) was 1.8 +/- 0.8 in the 26 patients of the dexamethasone group and 1.2 +/- 0.9 in the 25 patients of the placebo group (P < .05). Time to onset of pain relief was also faster in steroid-treated patients who demonstrated relief beginning at 6.3 +/- 5.3 hours, compared with 12.4 +/- 8.5 hours in the placebo group (P < .01). Of the 26 patients evaluated at seven days (13 in each group), time to complete lack of pain averaged 15.0 +/- 11.4 hours in the dexamethasone group and 35.4 +/- 17.9 hours in the placebo group (P < .02). Complications attributable to dexamethasone were not observed. CONCLUSION: In patients with severe, acute exudative pharyngitis, single-injection dexamethasone adjuvant compared with placebo resulted in statistically and clinically significant improvement, as evidenced by more rapid onset and greater degree of pain relief.

Acute Disease↗
PubMed1993

Pathophysiologic and therapeutic implications of acid-base changes during CPR.

Acid-base changes occurring during cardiac arrest and subsequent CPR are related to a complex low-perfusion state characterized clinically by venous and tissue hypercarbic and metabolic (lactic) acidosis. This low-flow state is a dynamic process dependent on the time intervals between onset of arrest, initiation of CPR, and restoration of adequate spontaneous circulation. Increased release of CO2 from ischemic tissues and reduced CO2 transport from the tissues to the lungs result in profound tissue acidosis. However, recent experimental data suggest that even very low pH is compatible with neurologically intact survival. Thus, the clinical use of buffer agents, and especially of sodium bicarbonate, is currently controversial. Because results of controlled clinical studies are not available, a careful review of well-performed experimental studies is necessary. So far, the use of either CO2-generating or CO2-consuming buffers has not been proved conclusively to increase neurologically intact long-term survival after CPR. More importantly, adequate ventilation and effective chest compressions must be quickly established after cardiac arrest. This will counterbalance the hypercarbic and metabolic acidemia of cardiac arrest by creating concurrent hypocarbic arterial alkalemia during at least the early phase of CPR. Thus, the treatment of the complex acid-base changes associated with CPR is based primarily on the classical maneuvers of A and B (airway and breathing = adequate oxygenation and ventilation), C (chest compressions), and D (early defibrillation for rapid restoration of spontaneous circulation). In cases of prolonged cardiac arrest or preexisting metabolic acidemia, buffer therapy may be indicated.

Acid-Base Imbalance↗
PubMed1993

Acute urinary retention: an unusual presentation of appendiceal abscess.

Emergency physicians frequently encounter patients with acute urinary retention. Although most common among the elderly, pediatric and young adult patients occasionally may present with this complaint. The differential diagnosis and emergency department work-up must be age specific. We discuss the case of a young man who presented with acute urinary retention, subsequently found to be caused by undiagnosed appendicitis with appendiceal abscess formation. Only nine such cases have been reported in the literature thus far, with only one occurring in the nonpediatric population. This case represents the second such case to be reported. The importance of a thorough history, physical examination, and diagnostic work-up of patients who present with acute urinary retention, particularly those in the younger age group, is emphasized.

Abscess↗
PubMed1992

Prior exposure to a running wheel and scheduled food attenuates polydipsia acquisition.

Groups of rats were given different histories before exposure to daily, 2-h fixed-interval (FI) 1-min food-schedule sessions with water available. In a previous study, a group with a history of chronic exposure to FI 1-min sessions without water subsequently had a reduced rate of acquisition and final level of schedule-induced polydipsia compared to a control group lacking this history. In the present study, groups with histories of chronic exposure to FI 1-min sessions and a concurrent running wheel were even more attenuated in their subsequent acquisition of polydipsia. Substitution of 5% ethanol for session water in the final phase produced a convergence in group intakes, except for a group which continued to have access to the running wheel. The ethanol intake of this group was relatively suppressed.

Animals↗
PubMed1992

Oral cocaine self-administration: relation of locomotor activity to pharmacokinetics.

Rats were exposed to daily schedule-induced polydipsia sessions in which solutions of cocaine HCl were available. Both cocaine solution concentration (0.08-0.32 mg/ml) and session duration (0.25-3 h) were varied to determine their effects on locomotor activity rate. Additional animals were used to determine the effect of session length on serum cocaine and metabolite levels when drinking 0.32 mg/ml cocaine solution. Changes in locomotor activity rate were related to serum cocaine concentration by a linear concentration-effect model. By estimation from the linear model, the serum cocaine concentration threshold for increasing locomotor activity was about 0.01 microgram/ml. Under these schedule-induction conditions, there was no evidence for the development of acute tolerance to the locomotor-stimulating activity of cocaine.

Animals↗
PubMed1992

Orally self-administered cocaine: reinforcing efficacy by the place preference method.

In three separate place preference conditioning (PPC) experiments, groups of rats were exposed to different modes of receiving cocaine: IP cocaine doses (7.5 mg/kg), PO cocaine self-administered bolus doses (15 mg/kg), and 1-h schedule-induced cocaine-solution drinking sessions (19.1 mg/kg). Oral cocaine self-administration of PO bolus and schedule induction took place in situations that preceded transfer into an apparatus for PPC sessions. Thus, the reinforcing efficacies of the pharmacological consequences of both oral cocaine self-administration methods were evaluated by a procedure separate from the self-administration behavior itself. The IP cocaine dose imposition and the two oral cocaine self-administration arrangements all resulted in dose-exposure conditions sufficient for the production of PPC. The serum and brain cocaine pharmacokinetics sufficient for the production of reinforcing efficacy were measured and related to previous data.

Administration, Oral↗
PubMed1992

Lactic acidosis in critical illness.

PURPOSE: This article reviews the current body of knowledge regarding lactic acidosis in critically ill patients. The classification of disordered lactate metabolism and its pathogenesis are examined. The utility of lactate as a metabolic monitor of shock is examined and current therapeutic strategies in the treatment of patients suffering from lactic acidosis are extensively reviewed. The paper is designed to integrate basic concepts with a current approach to lactate in critical illness that the clinician can use at the bedside. DATA SOURCES: Comprehensive review of the available, basic science, medical, surgical, and critical care literature. CONCLUSIONS: The severity of lactic acidosis in critically ill patients correlates with overall oxygen debt and survival. Lactate determinations may be useful as an ongoing monitor of perfusion as resuscitation proceeds. Therapy of critically ill patients with lactic acidosis is designed to maximize oxygen delivery in order to reduce tissue hypoxia by increasing cardiac index, while maintaining hemoglobin concentration. Buffering agents have not been shown to materially affect outcome from lactic acidosis caused by shock. The benefits of other specific therapies designed to reduce the severity of lactic acidosis remain unproven.

Acidosis, Lactic↗
PubMed1992

Fluid resuscitation in traumatic hemorrhagic shock.

Fluid resuscitation from traumatic hemorrhagic shock is a critical component of therapy for the critically injured patient. Therapy is aimed at restoring hemodynamic stability and oxygen delivery to tissues. The route and rate of fluid infusion, the temperature of the fluid infused, the type of asanguineous fluids chosen, and the timing of red cell transfusion may all impact substantially on the patient outcome. Complications of fluid therapy, especially edema, may be related to the choice of fluid infused. Identification of hypovolemia and methods to monitor tissue are important aspects of patient care.

Animals↗
PubMed1991

Cyclin promotes the tyrosine phosphorylation of p34cdc2 in a wee1+ dependent manner.

The regulation of p34cdc2 was investigated by overproducing p34cdc2, cyclin (A and B) and the wee1+ gene product (p107wee1) using a baculoviral expression system. p34cdc2 formed a functional complex with both cyclins as judged by co-precipitation, phosphorylation of cyclin in vitro, and activation of p34cdc2 histone H1 kinase activity. Co-production of p34cdc2 and p107wee1 in insect cells resulted in a minor population of p34cdc2 that was phosphorylated on tyrosine and displayed an altered electrophoretic mobility. When p34cdc2 and p107wee1 were co-produced with cyclin (A or B) in insect cells, there was a dramatic increase in the population of p34cdc2 that was phosphorylated on tyrosine and that displayed a shift in electrophoretic mobility. The phosphorylation of p34cdc2 on tyrosine was absolutely dependent upon the presence of kinase-active p107wee1. Tyrosine-specific as well as serine/threonine-specific protein kinase activities co-immunoprecipitated with p107wee1. These results suggest that cyclin functions to facilitate tyrosine phosphorylation of p34cdc2 and that p107wee1 functions to regulate p34cdc2, either directly or indirectly, by tyrosine phosphorylation.

Animals↗
PubMed1991

Sustained synergism by chronic caffeine of the motor control deficit produced by midazolam.

To evaluate the effects of chronic caffeine on the impairment of discriminative fine motor control produced by midazolam, rats were trained to hold a force transducer steady to deliver food pellets. Chronic, daily doses of midazolam (3 mg/kg SC) led to a stable level of motor impairment. Chronic caffeine (20 mg/kg IP) alone usually produced a more moderate deficit or, for one animal, no deficit. Combined, chronic administration of these doses yielded a sustained synergism in motor performance impairment, which contrasted with the antagonism usually found between the benzodiazepines and methylxanthines when performance is evaluated by psychomotor tests not requiring fine motor control. The observed synergism was not explicable in terms of measured disposition of the drugs. The synergistic production of fine motor dyskinesia by the concurrent administration of caffeine and midazolam may be relevant to the triggering of anxiety attacks by caffeine observed in panic disorder patients.

Animals↗