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Biomedical subjects

M S Chow

Publications and source records attributed to M S Chow.

At least 91 records · Page 5Linked to original sources
PubMed1988

Multidisciplinary program for promoting single prophylactic doses of cefazolin in obstetrical and gynecological surgical procedures.

A multidisciplinary cost-containment program for promoting the use of single prophylactic doses of cefazolin for obstetrical and gynecological surgical procedures is described. Following a one-month review of patient charts to identify the antimicrobial regimens used most frequently for prophylaxis in obstetrical and gynecological surgical procedures, the department of pharmacy services, with the cooperation of the pharmacy and therapeutics (P&T) committee and the departments of obstetrics and gynecology and infectious diseases, implemented an educational program to promote the use of single doses of cefazolin for surgical prophylaxis. The program included inservice education and distribution of letters of support and a therapeutics newsletter. Drug stocking patterns in the operating and delivery rooms were changed to make cefazolin more accessible, and the P&T committee formally restricted the use of prophylactic antimicrobial agents in obstetrical and gynecological surgical procedures to single doses of cefazolin unless a consulting infectious-disease physician recommended otherwise. Compliance with the program increased as each step was implemented; data collected 16 months after the program was initiated demonstrated a compliance rate of 78.8%. Based on comparison of data collected before initiation and six months after initiation of the program, an actual cost savings of +7,125 was realized, which extrapolates to +14,250 annually. No apparent adverse effects on patient care were noted. The multidisciplinary approach to promoting the use of single doses of cefazolin was effective.

Cefazolin↗
PubMed1987

Lorcainide for the treatment of refractory ventricular tachycardia: clinical and electrophysiologic results.

The electrophysiologic effects and antiarrhythmic efficacy of lorcainide were evaluated using programmed electrical stimulation (PES) in 14 patients with ventricular tachycardia (VT) refractory to conventional drug therapy. Lorcainide was administered orally (200-400 mg/d, eight patients), intravenously (150 mg/d, one patient), or by both routes (250-380 mg/d, five patients) prior to PES. In 13 patients undergoing both control and lorcainide PES, lorcainide increased the QRS duration (102 +/- 28 to 125 +/- 28 ms, P less than .001) and the QTc interval (430 +/- 39 to 471 +/- 32 ms, P less than .01) but had no effect on the RR interval (786 +/- 156 to 780 +/- 172 ms, P greater than .2). The right ventricular effective refractory period increased from 258 +/- 8 to 285 +/- 22 ms (P less than .001). Lorcainide prevented VT induction or resulted in induction of only well-tolerated, nonsustained VT in six of 14 patients (43%). The cycle length of induced VT increased from 264 +/- 32 to 306 +/- 34 ms (P less than .01). Of six patients started on chronic therapy, four still receive lorcainide after 18 +/- 7 months. Adverse effects have consisted mainly of sleep disturbances. Thus, it can be stated that lorcainide is effective in certain patients with VT refractory to conventional therapy.

Adult↗
PubMed1987

Transfer from immediate-release disopyramide to controlled-release disopyramide.

Simulation of serum disopyramide concentrations during transfer from steady-state immediate-release (IR) disopyramide to a sustained-release disopyramide preparation was performed based on pharmacokinetic parameters obtained from IR disopyramide and serum concentrations measured following an initial dose of controlled-release (CR) disopyramide phosphate. Based on the results of simulation, a typical patient with good cardiac, renal, and hepatic function can be transferred from a q 6 h IR disopyramide to an equivalent daily dose of controlled-release disopyramide administered q 12 h beginning at 6 hours after the final IR disopyramide dose.

Anti-Arrhythmia Agents↗
PubMed1986

Prediction of steady-state trough serum procainamide concentrations after administration of a sustained-release procainamide preparation.

Four methods of predicting steady-state trough serum procainamide concentrations (SPC) were compared in 15 patients receiving sustained-release procainamide (Procan-SR) therapy. All methods were based on a one-compartment pharmacokinetic model. Method 1 utilized nine initial measured SPC and individualized pharmacokinetic parameters for prediction of the steady-state SPC. Method 2 utilized three SPC and individualized pharmacokinetic parameters. Method 3 utilized two SPC and an individualized apparent elimination rate constant plus other average pharmacokinetic parameters. Method 4 utilized all averaged pharmacokinetic parameters (required no initial SPC). The predicted and measured SPCs for each method were analyzed by linear regression. Regression equations and correlation coefficients (r) for Methods 1, 2, 3, and 4 were as follows: predicted SPC = 0.72 measured SPC + 1.60 (r = 0.86), predicted SPC = 0.67 measured SPC + 1.74 (r = 0.82), predicted SPC = 0.13 measured SPC + 2.57 (r = 0.58), and predicted SPC = 0.15 measured SPC + 2.47 (r = 0.52), respectively. The precision, as measured by the mean squared prediction error (95% confidence interval) for Methods 1, 2, 3, and 4 was 1.44 (0.61, 2.27), 1.75 (0.93, 2.57), 2.81 (1.3, 4.49), and 3.68 (1.12, 6.26), respectively. (Eighty-five percent of the predictions were within +/- 1.5 micrograms/ml of the measured SPC by Methods 1 and 2, as compared with 69% by Methods 3 and 4.) Bias, as measured by the mean prediction error (95% confidence interval) for Methods 1, 2, 3, and 4 were -0.44 (-0.90, 0.03), -0.34 (-0.87, 0.18), -0.43 (-1.09, 0.24), and -0.98 (-1.66, -0.31).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1986

Two-point method for determination of aminoglycoside pharmacokinetics: theoretical and practical considerations.

A method is described that utilizes any two serum concentrations obtained during a multiple dosage regimen to estimate aminoglycoside pharmacokinetics. The accuracy of this method was tested theoretically using simulated patient data. In addition, the ability of this method to estimate gentamicin pharmacokinetics and predict serum gentamicin concentrations (SGC) in individual patients was evaluated and compared with the method of Sawchuk and Zaske. Based on the theoretical and patient data evaluations, reasonably accurate pharmacokinetic parameters were derived by the present method, especially when a pair of peak and trough SGC were utilized. In addition, the prediction error of this two-point fitting method (using pairs of peak-trough SGC) was not significantly different from that of the Sawchuk-Zaske method. These results indicate that the present two-point method (when using a pair of peak-trough SGC) provides a convenient and useful approach in individualization of aminoglycoside therapy in patients.

Aminoglycosides↗
PubMed1986

The effect of lidocaine and bretylium on the defibrillation threshold during cardiac arrest and cardiopulmonary resuscitation.

The effect of intravenous lidocaine, 2 mg/kg, and bretylium, 5 mg/kg, on defibrillation threshold (DFT) was investigated in alpha-chloralose anesthetized dogs undergoing conventional closed chest cardiopulmonary resuscitation (CPR) following induced ventricular fibrillation. Ventricular fibrillation was induced electrically and CPR was performed by a pneumatic device set to compress the chest 60 times and inflate the lung 12 times a minute. Defibrillation was achieved using underdamped sinusoidal current shocks from a special defibrillator which allowed determination of delivered energy. The DFT was defined as the peak current which defibrillated, but no more than 20% higher than a current which did not defibrillate. All DFTs were obtained within 5 min of CPR. The mean +/- SD current and energy thresholds required for defibrillation during lidocaine-CPR (seven dogs) were 17.0 +/- 8.9 A and 53.0 +/- 40.7 J as compared to 12.5 +/- 6.2 A and 34.3 +/- 30.7 J, respectively during control-CPR (P less than 0.05). The mean +/- SD current and energy thresholds during bretylium-CPR were 11.0 +/- 3.4 A and 24.1 +/- 1.3 J as compared to 11.8 +/- 1.7 A and 29.4 +/- 9.6 J, respectively, during control-CPR (NS). These results show that lidocaine acutely elevated defibrillation threshold whereas bretylium did not produce such an effect. The effect on DFT along with other pharmacologic properties should be considered when lidocaine or bretylium is used in the setting of cardiac arrest and CPR.

Animals↗
PubMed1986

Accuracy of Bayesian and Sawchuk-Zaske dosing methods for gentamicin.

The derived pharmacokinetic variable estimates from a Bayesian aminoglycoside dosing program were compared with those from the Sawchuk-Zaske method to determine which variable estimates were the most accurate in fitting the test dose and in predicting subsequent peak and trough serum concentrations. Data on 17 patients with moderately impaired but stable renal function were analyzed. All patients received gentamicin sulfate for treatment of their infections. To determine the individualized variables using the Bayesian program, demographic data, dosing history, and one (midpoint), two (peak and trough), or four serum drug concentrations were entered into the program. The Sawchuk-Zaske method used three serum concentrations determined following a first dose or four concentrations before and after a subsequent dose to derive individualized pharmacokinetic variables. The estimates of pharmacokinetic variables determined using the Bayesian method with one, two, or four serum concentrations did not differ significantly from those obtained using all the available serum concentrations with the Sawchuk-Zaske method. Although the actual numeric differences of prediction, absolute, and squared errors for fitting the test dose were minimal, significant differences were seen. All methods were similar in predicting serum concentrations from continued dosing. For the prediction error from continued dosing, a slight but significant difference was observed with the Bayesian method using one serum concentration when compared with the other methods. The Bayesian method using one, two, or four serum gentamicin concentrations individualized pharmacokinetic variables as well as the Sawchuk-Zaske method.

Aged↗
PubMed1985

Antifibrillatory effects of lidocaine and bretylium immediately postcardiopulmonary resuscitation.

The antifibrillatory effects of lidocaine and bretylium in the postcardiopulmonary resuscitation (CPR) setting were examined using ventricular fibrillation threshold (VFT) determinations in anesthetized dogs. The dogs were fibrillated and CPR was carried out with a pneumatic device. Lidocaine and bretylium were administered intravenously at the onset of CPR, and VFT was serially determined after defibrillation following three consecutive 3-minute CPR periods. A dose of 2 mg/kg of lidocaine caused a significant increase in VFT determinations after the first but not subsequent 3-minute CPR periods; a dose of 1 mg/kg of lidocaine was ineffective at any time point. A dose of 5 mg/kg of bretylium elevated the VFT after the second and third but not the first 3-minute period. In dogs who received lidocaine, a significant elevation of VFT determinations were found to be associated with a high blood lidocaine concentration (mean 13.8 +/- 8.3 micrograms/ml). The present study demonstrates that a 2 mg/kg dose of lidocaine administered during CPR rapidly increases VFT determinations after CPR (within 5 minutes), whereas, a 5 mg/kg dose of bretylium significantly elevates VFT determinations but at a later time (within 10 minutes). The observed significant effect of lidocaine appears to be associated with high lidocaine blood concentrations (greater than 6 micrograms/ml).

Animals↗
PubMed1985

Estimation of renal creatinine clearance in patients with unstable serum creatinine concentrations: comparison of multiple methods.

The accuracy of different methods of calculating 24-hour creatinine clearance in patients with unstable renal function was compared using simulated data (based on a one-compartment pharmacokinetic model), as well as data from postrenal transplant patients. When creatinine clearance was calculated from the urinary creatinine excretion and a serum creatinine concentration, the use of the midpoint serum creatinine concentration produced the lowest degree of error. Therefore, this method is recommended for routine clinical determination of creatinine clearance in such patients. When the urinary creatinine excretion was unknown, an iteration method produced the lowest degree of error among four methods, and therefore is recommended to estimate creatinine clearance in such patients.

Adult↗
PubMed1984

Half-life prediction in unstable renal function: its utility in therapeutic drug monitoring and theoretical and practical considerations.

A simple equation is derived to describe the changes in drug elimination half-life (t1/2) in correspondence to the changes in renal function (as measured by creatinine clearance). This equation can be utilized to predict the t1/2 at any time following an initial period in patients with unstable renal function provided that the initial t1/2 and renal function corresponding to each period are known. The clinical application of this equation in predicting 21 serum gentamicin concentrations (SGC) was evaluated in patients with unstable renal function. Excellent correlation (coefficient of determination, r2 = 0.88) between the predicted and measured SGC was obtained.

Bacterial Infections↗
PubMed1983

Isolation and Partial Characterization of Two Aeromonas hydrophila Bacteriophages.

Two Aeromonas hydrophila bacteriophages, Aeh1 and Aeh2, were isolated from sewage. Both phages showed binal symmetry. The dimensions of A. hydrophila phages Aeh1 and Aeh2 differed from those of the other Aeromonas phages. Also, phage Aeh2 was the largest Aeromonas phage studied to date. Phage Aeh1 formed small, clear plaques, and phage Aeh2 formed turbid plaques with clear centers. Both phages were sensitive to chloroform treatment, being totally inactivated after treatment for 1 h at 60 degrees C at pH 3 and 11. However, the infectivity of Aeh1 phage stocks increased by approximately fivefold after they were treated at pH 10 for 1 h at 22 degrees C. Phages Aeh1 and Aeh2 were serologically unrelated and had latent periods of 39 and 52 min, respectively. The average burst sizes of phages Aeh1 and Aeh2 were 17 and 92 PFU per cell, respectively. Phage Aeh1 infected 13 of 22 A. hydrophila strains tested, whereas phage Aeh2 infected only its original host. Phage Aeh1 infected some A. hydrophila strains only at or below 37 degrees C. Neither phage infected the two A. (Plesiomonas) shigelloides strains used in this study.

Journal Article↗
PubMed1983

Effect of external cardiopulmonary resuscitation on lidocaine pharmacokinetics in dogs.

Lidocaine pharmacokinetics were studied in five fibrillated dogs undergoing external cardiopulmonary resuscitation (CPR) and five comparable control dogs. All animals were anesthetized with sodium pentobarbital and their electrocardiogram, arterial blood pressure, left ventricular pressure and carotid blood flow were monitored continuously. All dogs received a 2 mg/kg i.v. bolus dose of lidocaine. Multiple blood samples from venous, arterial, left ventricular and right atrial sites were obtained for determination of blood lidocaine concentration. At 60 min, the dogs were sacrificed. Lung, liver, kidney, brain, skeletal muscle and heart tissue samples were collected. There were dramatic differences between the control and CPR groups in arterial pressure, left ventricular pressure and carotid blood flow. In the CPR dogs, lidocaine blood concentrations for the entire 60 min were significantly higher than the control dogs and lidocaine clearance was reduced at least by 8-fold. A comparison of extraction ratios across skeletal muscle demonstrated that the phase of tissue uptake was prolonged in the CPR group. In each of the tissue samples, significantly higher tissue concentrations were observed in the CPR group. The results of our study show that lidocaine disposition is greatly altered during CPR and this is most likely due to a tremendous reduction of cardiac output and blood flow during CPR.

Animals↗
PubMed1982

In vivo inactivation of tobramycin by ticarcillin. A case report.

Inactivation of tobramycin sulfate by ticarcillin disodium was observed in a patient with impaired renal function. Tobramycin elimination half-life was seven hours with concurrent ticarcillin therapy but 35 hours without ticarcillin therapy. The magnitude of change cannot be attributed to changing renal function or tobramycin accumulation. The present case demonstrates that in vivo inactivation of tobramycin by ticarcillin can substantially increase the overall tobramycin elimination rate in patients with severe renal failure; however, in patients with normal renal function such inactivation is predicted to cause little change in overall tobramycin elimination rate.

Aged↗
PubMed1982

Beneficial hemodynamic effects of intravenous terbutaline in patients with severe heart failure.

The hemodynamic effects of terbutaline infusion at rates of 0.15, 0.3, and 0.45 micrograms/kg/min were studied and compared in eight patients with severe heart failure. Terbutaline infusion at 0.15 micrograms/kg/min infusion produced insignificant effects at 30 minutes. At 0.3 micrograms/kg/min infusion highly significant beneficial hemodynamic effects were observed: at 60 minutes cardiac index increased from 1.79 +/- 0.38 to 3.60 +/- 0.96 (mean +/- SD) L/min/m2 (p less than 0.0001) and stroke volume index increased from 20.1 +/- 6.2 to 36.7 +/- 13.1 ml/beat/m2 (p less than 0.0001); mean pulmonary artery wedge pressure fell from 27.5 +/0- 5.5 to 18.5 +/- 5.7 mm Hg (p less than 0.0001); systemic vascular resistance fell from 2624 +/- 586 to 1455 +/- 500 dynes . sec . cm-5/m2 (p less than 0.0001); and pulmonary vascular resistance fell from 248 +/- 84 to 150 +/- 70 dynes . sec . cm-5/m2 (p less than 0.0005). Mean arterial pressure and O2 uptake did not change significantly; however, mean heart rate increased from 93.4 +/- 22 to 103.1 +/- 26 bpm (p less than 0.005) and plasma potassium fell from 3.86 +/- 0.14 to 3.12 +/ 0.23 mEq/L (p less than 0.05). The 0.45 micrograms/kg/min infusion at 30 minutes produced no greater hemodynamic changes than that from 0.3 micrograms/kg/min. Our study suggests that intravenous terbutaline produces beneficial effects and may be useful in the acute management of severe heart failure.

Adult↗
PubMed1981

Disopyramide hemodialysis and kinetics in patients requiring long-term hemodialysis.

Disopyramide hemodialysis and kinetics after 200 mg orally in six patients receiving long-term hemodialysis were examined. Mean volume of distribution (area) was 66.5 +/- 13 l. Mean times of the peak serum concentration and mean peak serum concentration were 2.3 +/- 0.9 hr and 3.1 +/- 0.9 microgram/ml. Mean absorption half-life (t 1/2) was 21.6 +/- 12.5 min. Mean disopyramide elimination t 1/2 during dialysis was 16.8 +/- 11.9 hr, not significantly different from mean elimination t 1/2 without dialysis of 16.1 +/- 5.2 hr. End-dialysis bath concentrations of disopyramide showed that not more than 2.4% of the dose was dialyzed during a 2-hr dialysis period. Our data indicate that at therapeutic concentrations disopyramide was not appreciably dialyzed.

Adult↗
PubMed1977

Aspirin.

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Aspirin↗