Search PubMed⌕ Search

Biomedical subjects

S A Conrad

Publications and source records attributed to S A Conrad.

At least 19 recordsLinked to original sources
PubMed1995

Intravenacaval membrane oxygenation and carbon dioxide removal in severe acute respiratory failure.

STUDY OBJECTIVE: To characterize the physiologic response to, and safety of, intravenacaval membrane oxygenation and carbon dioxide removal. DESIGN: Interventional before-after study. SETTING: University teaching hospital ICU. PATIENTS: Twenty-two patients with severe acute respiratory distress syndrome (ARDS). INTERVENTIONS: Implantation of a hollow-fiber membrane oxygenator (IVOX; CardioPulmonics; Salt Lake City, Utah) into the superior and inferior venae cavae by venotomy of the right femoral or right internal jugular vein for a duration of up to 20 days. MEASUREMENTS: Hemodynamic measurements using pulmonary artery and systemic artery catheters, ventilator settings (FIO2, minute ventilation, peak inspiratory pressure, and positive end-expiratory pressure), arterial and mixed venous blood gases (pH, PCO2, PO2, and measured saturation), and clinical laboratory determinations (CBC, fibrinogen, plasma hemoglobin, complement C3 and C5) were obtained. Calculations of PaO2/FIO2 ratio and PaCO2-VE product were used to assess gas exchange efficacy. Microbiologic cultures were obtained from the device and wound following explantation. Survival to ICU discharge and hospital discharge were recorded. RESULTS: Implantation was successful in 20 of 22 patients. Gas exchange rates averaged 50.4 +/- 15.8 mL.min-1 for carbon dioxide and 71.1 +/- 20.2 mL.min-1 for oxygen. A reduction in FIO2 from 0.78 +/- 0.16 to 0.63 +/- 0.21 and in VE from 177 +/- 94 mL.kg-1.min-1 to 127 +/- 58 mL.kg-1.min-1 was possible within 4 h post-implantation. By 12 h, FIO2 was reduced to 0.57 +/- 0.18. Indices of gas exchange improved significantly after implantation, with PaO2/FIO2 ratio increasing from 79 +/- 20 to 112 +/- 47 and PaCO2-VE product decreasing from 7.6 +/- 4.2 to 4.9 +/- 2.5 within 4 h. A significant reduction in peak inspiratory pressure was achieved (45 +/- 10 to 38 +/- 9 cm H2O). Major complications were blood loss during implantation requiring transfusion in 11 patients, a retroperitoneal bleed in 1 patient, and femoral deep venous thrombosis in 4 patients, but there were no long-term sequelae or IVOX-related deaths. The ICU and hospital survival were 10/20 (50%) and 8/20 (40%), respectively. CONCLUSIONS: Intravenacaval membrane oxygen and carbon dioxide removal can provide partial respiratory support during severe respiratory failure and permit reductions in the level of mechanical ventilator support, with an acceptable safety profile.

Adult↗
PubMed1994

In vivo gas transfer performance of the intravascular oxygenator in acute respiratory failure.

The intravascular oxygenator (IVOX) has undergone both animal and clinical trials. Data from the animal studies have demonstrated that the device is capable of transferring up to approximately 100 ml/min of oxygen and carbon dioxide. Initial data from the human trials suggest that gas transfer, although approaching these levels, varied widely in patients with respiratory failure. We studied the factors affecting gas exchange in 26 patients with severe acute respiratory failure who underwent intravenacaval support of gas exchange with IVOX. The patients underwent monitoring of IVOX gas transfer rates, hemodynamics, blood gases, and ventilation parameters at scheduled intervals following device insertion. All devices functioned following implantation. The mean value for O2 transfer was 64 +/- 21 SD ml/min (range 15-114 ml/min) and for CO2 transfer was 48 +/- 17 ml.min-1 (range 14-112 ml/min). CO2 transfer correlated positively with device surface area, cardiac output, and mixed venous Pco2 and negatively with duration of implantation. O2 transfer did not correlate with any patient factors probably due to error inherent in the measurement of this variable. Independent measurements of IVOX gas transfer by respiratory gas exchange in a subset of patients with normal values of mixed venous Pco2 were in good agreement with the routine measurements and indicated that the device provided up to 26% of gas exchange requirements in this subset. We conclude that IVOX transfers clinically useful amounts of oxygen and carbon dioxide in vivo. Factors that influence gas transfer include device surface area, PvCO2, cardiac output, and duration of implantation. Optimization of these factors (such as with permissive hypercapnea) could result in enhanced performance in vivo.

Acute Disease↗
PubMed1994

Major findings from the clinical trials of the intravascular oxygenator.

Major clinically relevant findings have been extracted and summarized from the database developed from the international multicenter clinical trials of the intravascular oxygenator (IVOX) as a means for augmenting the deficient blood gas transfer of patients in advanced acute respiratory failure (ARF). Between February 1990 and May 1993, a total of 164 IVOX devices were utilized in 160 clinical trial patients who were hypoxemic and/or hypercarbic while receiving closed system positive pressure mechanical ventilator support at or exceeding generally accepted minimum safe levels of intensity. The average rates of oxygen and carbon dioxide transfer into and out of circulating venous blood by means of the IVOX device varied from 40-70 ml/min. Evidence of patient benefit during IVOX utilization includes improvement in blood gas partial pressures associated with decreased intensity of mechanical ventilation, improved hemodynamics in patients with mechanical ventilator depressed cardiovascular function, and decreased indices of lung dysfunction. Clinically recognized IVOX-related complications or adverse events were reported in 24.5% of the clinical trials patients. At necropsy examination of 68 clinical trials patients who died during or after IVOX utilization, forensic pathologists reported 4 cases in which IVOX utilization could have been a primary or contributing cause of death. Significant IVOX device mechanical and/or performance malfunction problems were recognized in 29 (17.7%) of the IVOX devices utilized in clinical trials. IVOX clinical trials data collected and analyzed to date indicate IVOX utilization has a favorable risk/benefit ratio in patients in severe, acute, potentially reversible ARF.

Acute Disease↗
PubMed1992

Alterations in the microbial flora and in the incidence of bacteremia at a university hospital after adoption of amikacin as the sole formulary aminoglycoside.

Because of the rapid emergence of resistance to gentamicin and tobramycin among isolates of aerobic and facultative gram-negative bacteria at our university hospital, we designed a prospective study to track aminoglycoside resistance, bacteremic episodes, and bacteremia-associated deaths before and after the institution of amikacin as the sole formulary aminoglycoside. From June 1984 through June 1987 (immediately before this policy change), amikacin accounted for only 20% of patient-days of aminoglycoside therapy, and rates of resistance to gentamicin, tobramycin, and amikacin among aerobic and facultative gram-negative bacterial isolates were 12.8%, 10.8%, and 5.9%, respectively. During the next 30 months (immediately after the change in policy), amikacin accounted for 98% of patient-days of aminoglycoside therapy, and rates of resistance to gentamicin, tobramycin, and amikacin were 6.3%, 5.0%, and 3.3%, respectively. Furthermore, during the latter 30 months, the incidence of both bacteremia and bacteremia-associated death decreased significantly. Hospitals at which resistance to gentamicin or tobramycin is increasing among the gram-negative flora may benefit from the use of amikacin as the principal aminoglycoside.

Amikacin↗
PubMed1991

The residual central venous catheter track--an occult source of lethal air embolism: case report.

Air embolization through a residual track after removal of a central venous catheter is an elusive mechanism of a treacherous problem. Prompt diagnosis is necessary for successful application of established therapy, as demonstrated by this case report. Awareness of this unusual mechanism of air embolism with utilization of simple prophylactic measures, however, remains the best treatment.

Catheterization, Central Venous↗
PubMed1990

Cardiovascular and metabolic response to red blood cell transfusion in critically ill volume-resuscitated nonsurgical patients.

We examined the cardiovascular and metabolic response to RBC transfusion in patients with circulatory shock after volume resuscitation. Data were analyzed from 36 transfusions in 32 patients who were undergoing continuous hemodynamic monitoring. Transfusions were administered for moderate to severe anemia, mean Hgb 8.3 g/dl. The diagnosis were sepsis (19/36), cardiogenic shock (14/36), connective tissue disease (2/36), and severe hypocalcemia (1/36). Benefit from transfusion was defined as an improvement in tissue oxygen utilization (increased oxygen consumption [VO2] or decreased lactate), a decrease in myocardial VO2 (MAP x HR), or a decrease in myocardial work (left ventricular work index). Mean transfusion volume was 577 ml over 4.5 h. Hgb and oxygen delivery (DO2) increased by 27% and 28%, respectively, while pulmonary artery wedge pressure and cardiac index were unchanged. No significant change was noted in VO2, or lactate, after augmentation of red cell mass. An increase occurred in myocardial work indices and MAP x HR. No changes were identified when subgroups were analyzed based on diagnosis, pretransfusion Hgb, lactate, or VO2 levels. We conclude that selective increase in DO2 by augmentation of RBC mass and oxygen-carrying capacity did not improve the shock state in these volume-resuscitated patients, regardless of the etiology of the shock.

Adolescent↗
PubMed1990

Accuracy of flexible fiberoptic endoscopy in identifying abnormal endotracheal tube positions.

This study was carried out to investigate the accuracy of a simple, nonmaneuverable, flexible fiberoptic catheter in identifying both normal and abnormal endotracheal tube (ETT) positions. In addition, the utility of flexible fiberoptic endoscopy (FFE) for ETT position determination in inexperienced hands was examined. One adult dog was sedated and instrumented in the esophagus and trachea with identical ETTs. Four possible ETT positions (trachea, carina, bronchus, esophagus) were randomly assigned. One investigator positioned the ETT into the assigned position by fluoroscopy. Four other blinded investigators were asked to determine the ETT position using the fiberoptic catheter. Each blinded investigator was given 15 seconds to complete the examination and record the ETT position. Randomization resulted in 25 ETT positions examined by each of the four blinded investigators for a total of 100 FFE determinations. FFE ETT determination was correct in 97% of the examinations. All esophageal intubations were correctly identified. Two tracheal locations were misdiagnosed as carina and bronchial, while one carinal location was incorrectly judged as tracheal. The sensitivity of FFE ETT localization was 91.7%, and the specificity was 98.6%. There was no difference in performance by investigator training level or endoscopy experience. We conclude that FFE is a rapid and accurate method for determining both normal and abnormal ETT locations. ETT position determination can be confidently performed by health professionals with minimal training.

Animals↗
PubMed1990

Effect of red cell transfusion on oxygen consumption following fluid resuscitation in septic shock.

Previous studies have shown that fluid resuscitation in septic shock improves oxygen consumption. Red cell transfusion during resuscitation from septic shock has also been shown to enhance oxygen consumption in patients with elevated lactate levels. This study investigates the effect of increasing oxygen delivery (DO2) through an isolated increase in arterial oxygen content following adequate fluid resuscitation from septic shock in humans. Nineteen patients receiving red cell transfusion (591 +/- 55 SEM ml) were monitored for changes in hemodynamic and oxygen utilization variables before and after transfusion. Transfusion resulted in a significant increase in hemoglobin (8.3 +/- 0.3 to 10.7 +/- 0.3 g.dl-1) and DO2 (483 +/- 29 to 621 +/- 32 ml.min-1.m-2). No increase in cardiac output or pulmonary artery wedge pressure (PAWP) resulted from the transfusion. In spite of the increase in delivery, there was no increase in oxygen consumption (VO2) or decrease in lactate. Subset analysis revealed that a pretransfusion oxygen extraction ratio under 24% was associated with an increase in VO2, but the pretransfusion level of cardiac index, PAWP, lactate, or VO2 was not. An isolated increase in arterial oxygen content as a means of increasing DO2 does not improve VO2 in septic shock following adequate fluid resuscitation. Patients with a low oxygen extraction ratio (less than 24%) represent a subset of patients which did improve consumption with transfusion, and may represent a more severe microcirculatory disturbance not amenable to fluid loading.

Blood Transfusion↗
PubMed1989

Microbial contamination of arterial infusions used for hemodynamic monitoring: a randomized trial of contamination with sampling through conventional stopcocks versus a novel closed system.

Arterial catheters are now commonly used to monitor blood pressure and obtain blood samples for arterial blood gas and other laboratory determinations. Stopcocks inserted into the pressure monitoring circuit have been the primary means of obtaining blood from arterial catheters. However, these stopcock systems have been associated with nosocomial contamination and bacteremias. Because of the problems of bacterial contamination and blood wasting with the stopcock sampling systems, we compared the frequency and extent of contamination of external sampling ports and the monitoring tubing fluid in stopcocks with that of a novel closed needle-sampling system (Lab-Site, Migada Ltd, Rehovot, Israel), incorporated into pressure monitoring tubing (Abbott Laboratories Inc., North Chicago, Illinois). We found that use of the novel sampling system resulted in significantly fewer episodes of internal bacterial contamination of the arterial monitoring line (7%) than did the use of a stopcock system (61%). External contamination of the sampling port was also lower in the novel system (8%) than in the stopcock system (37%). This suggests that the closed system may reduce the risk of nosocomial infections in patients requiring arterial pressure monitoring.

Adult↗
PubMed1988

Results of a prospective statewide reporting system for infective endocarditis.

To better understand the microbiology, anatomy, and demography of infectious endocarditis, we devised a prospective statewide reporting system to study these infections. Because our study design required accurate diagnosis, reliable case reporting, and a high probability of physician-to-case exposure, we enlisted the help of cardiologists, cardiovascular surgeons, and infectious disease specialists throughout Louisiana. All Louisiana members of the American College of Cardiology and the Infectious Diseases Society of America were invited to participate. Participants were supplied with a brief endocarditis report form and asked to complete the form as they saw patients with infective endocarditis. Seventy-five patients with infective endocarditis were reported for a case rate of 1.7 per 100,000 persons per year. This report analyzes the results from this one-year study.

Adolescent↗
PubMed1986

Optimal dose of fenoterol by metered-dose inhaler in asthmatic adults.

Three doses of fenoterol were administered by metered-dose inhaler to 20 adult subjects with asthma in order to determine the optimal dose for routine administration. Inhaled doses of 100 micrograms, 200 micrograms, and 400 micrograms of fenoterol with isoproterenol and placebo controls were administered in a randomized double-blind crossover regimen. We found that 200 micrograms of fenoterol by metered-dose inhaler produced a longer duration of action, greater peak response, and greater overall time-weighted responses in the forced expiratory volume in one second, in the mean forced expiratory flow during the middle half of the forced vital capacity, and in airway resistance than did the other drug regimens. The 400 micrograms dose of fenoterol produced no increase in response over that seen after the 200 micrograms dose. Side effects were minimal and no greater than with isoproterenol.

Administration, Intranasal↗
PubMed1985

Comparison of the effects of labetalol and hydrochlorothiazide on the ventilatory function of hypertensive patients with asthma and propranolol sensitivity.

Previous studies have shown that labetalol, a new alpha- and beta-adrenergic antagonist, is relatively safe for the treatment of hypertension in patients with chronic obstructive pulmonary disease (COPD). This multicenter study was designed to evaluate its effects in hypertensive patients with asthma and propranolol sensitivity. Hypertension was successfully controlled in 18 of 21 patients who received labetalol in increasing doses, up to 1,200 mg/day. The decrease in mean FEV1 (1.5 percent) two hours after the highest dose of labetalol was not statistically significant, although there was a gradual decline in mean baseline FEV1 during the four-week treatment period. Antihypertensive agents other than adrenergic antagonists should be considered for the management of hypertension in patients with asthma, especially those with marked reversibility of airflow. If treatment with beta-adrenergic antagonists is indicated, labetalol is recommended over other currently available agents.

Adolescent↗
PubMed1985

The use of labetalol for the treatment of hypertension in patients with reversible airway obstruction.

Beta-adrenergic blocking agents are commonly used for the management of hypertension, cardiac arrhythmias, and angina pectoris; several of these agents are now available for clinical use (1-5). A significant side effect of these agents in patients experiencing reversible airway obstruction is that they block the effects of beta-adrenergic agonists and can precipitate or worsen bronchospasm (6-8). Labetalol, a new adrenergic antagonist with both alpha- and beta-adrenergic blocking effects, has been shown to have certain advantages for the management of hypertension and is widely used for this purpose in many countries (9). To evaluate its effects on airway resistance in patients with obstructive lung disease, the authors conducted two separate clinical studies. This article summarizes the results of these trials.

Airway Resistance↗
PubMed1983

Effects of labetalol in hypertensive patients with chronic obstructive pulmonary disease.

Labetalol is a new adrenergic antagonist with both alpha- and beta-blocking effects. To evaluate its usefulness in the treatment of hypertension in patients with coexisting chronic obstructive pulmonary disease (COPD), labetalol was administered in gradually increasing doses to a group of 11 patients with mild-to-moderate hypertension and COPD with a mild reversible component. Ten patients given hydrochlorothiazide served as control subjects. Blood pressure was controlled in seven of the 11 patients given labetalol and in six of the ten patients given hydrochlorothiazide in dosages up to 1,200 mg/day and 150 mg/day, respectively. No significant changes occurred in the FEV1 or FEF25-75% two hours after the administration of the maximum dose of either drug or after exercise on the same day. Labetalol was well tolerated in the doses given.

Adult↗
PubMed1979

Alpha1-antitrypsin quantitation and Pi typing of stored postmortem blood.

Correlation of necropsy findings with protease inhibitor levels and phenotype is sometimes desirable. This study was designed to determine the feasibility of postmortem protease inhibitor assessment. One hundred fifteen consecutive postmortem samples, stored at -20 C for 24 to 53 months, were analyzed. The time from death to necropsy, storage time, and the pH values of the sera were correlated with alpha1-antitrypsin levels, trypsin inhibitory capacity, and Pi typability. The alpha1-antrypsin level and trypsin inhibitory capacity were not significantly correlated with morgue time, serum storage time, or pH, and mean values were within the expected ranges. A significant decrease in Pi typability occurred when pH was less than 7.0. Moreover, while most (86%) of the sera stored for 2 to 2 1/2 years were typable, only 30% of those stored for more than four years were typable. Determination of alpha1-antitrypsin and trypsin inhibitory capacity are possible with the use of stored postmortem blood. Pi typing is usually possible, provided sera are not acidic and are examined within 2 1/2 years.

Female↗