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Biomedical subjects

J A Stanfield

Publications and source records attributed to J A Stanfield.

11 recordsLinked to original sources
PubMed1990

Assessment of cefazolin and cefuroxime tissue penetration by using a continuous intravenous infusion.

A continuous intravenous infusion was used to assess the tissue penetration of cefazolin (14 subjects) and cefuroxime (15 subjects) in orthopedic surgery patients. Subjects were randomly assigned to receive a continuous intravenous infusion of cefazolin (mean, 178.6 mg/h) or cefuroxime (mean, 330.0 mg/h) at a rate estimated to achieve a target steady-state total concentration of 50 micrograms/ml in serum. The infusion was initiated 12 to 14 h before surgery, and blood and muscle tissue samples were collected intraoperatively at the times of incision and wound closure. Although there was a significant difference between the free concentrations of cefazolin (at incision, 9.3 micrograms/ml; at closure, 9.2 micrograms/ml) and cefuroxime in serum (at incision, 26.9 micrograms/ml; at closure, 31.8 micrograms/ml), there was no difference in the total concentrations in muscle at either surgical incision (cefazolin, 6.1 micrograms/g; cefuroxime, 5.6 micrograms/g) or wound closure (cefazolin, 7.7 micrograms/g; cefuroxime, 7.4 micrograms/g). There was a significant correlation between the pooled free serum and total muscle concentrations for cefazolin (P = 0.001); however, there was no correlation between these variables with the pooled cefuroxime data (P = 0.403). These findings indicate that the free drug concentration in serum alone is not consistently predictive of the total concentration of cephalosporin in muscle.

Cefazolin↗
PubMed1989

Single-dose cefmetazole versus multiple dose cefoxitin for prophylaxis in abdominal surgery.

One hundred and ninety-five patients undergoing abdominal surgical procedures completed a multicentre, randomized, open-label study comparing the safety and efficacy of cefmetazole and cefoxitin for the prevention of postoperative wound infection. Cefmetazole was administered iv in a single 2 g dose given within 90 min of the operation. Cefoxitin was administered in a single 2 g, similarly timed, preoperative dose and two additional doses given at 6 h intervals after surgery. For operations that exceeded 2-4 h duration an additional dose of each agent was administered. Patients undergoing colorectal operations received oral neomycin and erythromycin as bowel preparation. Colorectal operations were performed most frequently (49% of patients) followed by cholecystectomies (26%) and gastroduodenal procedures (21%). The operative site infection rate was 6.5% for cefmetazole and 7.7% for cefoxitin (P greater than 0.05). Serious drug related adverse effects were not observed. This study demonstrates that administration of single-dose cefmetazole is as effective as a standard three dose regimen of cefoxitin for prophylaxis with abdominal operations.

Abdomen↗
PubMed1989

Comparative intraoperative concentrations of two cephalosporins with activity against anaerobic bacteria.

We determined the intraoperative concentrations of cefmetazole and cefoxitin in serum and muscle from the wound of 30 patients who were undergoing cholecystectomies. The study employed an open-label design in which all patients randomly received cefoxitin sodium (30 mg/kg) or cefmetazole sodium (15 or 30 mg/kg) intravenously with the induction of anesthesia. Total serum and wound-muscle concentrations achieved with cefmetazole 30 mg/kg were significantly greater than those achieved with a similar dose of cefoxitin. Cefmetazole in a 15 mg/kg dose was comparable with cefoxitin 30 mg/kg in achieved concentrations. The elimination half-life for cefoxitin was much shorter than that for cefmetazole (41 min v. 64-68 min, respectively) and this relates to a shorter duration of action for the former. The choice of agent for surgical prophylaxis should incorporate factors relating to drug pharmacokinetic properties as well as microbiological factors.

Adolescent↗
PubMed1985

Esophageal source measurement of Tc-99m attenuation coefficients for use in left ventricular volume determinations.

A linear attenuation coefficient for water (mu = .15 cm-1) at 140 keV has been used in the determination of left ventricular volumes (LVV) by attenuation-corrected equilibrium methods. This theoretical value ignores the effect of Compton scatter and thus may be too high for human LVV determinations. The effective attenuation coefficient, mu', of the human chest was determined in ten normal volunteers using a Tc-99m esophageal source imaged with a gamma camera. Values for mu' at 30 degrees LAO in end-expiration, quiet breathing, and end-inspiration were .125 +/- .006 cm-1, .125 +/- .005 cm-1, and .113 +/- .007 cm-1, respectively (95% confidence interval). Values of mu' at 45 degrees LAO were .122 +/- .006 cm-1, .119 +/- .007 cm-1, and .099 +/- .009 cm-1, respectively, for the same conditions. The measured value of mu' for the source in a water phantom was .127 +/- .001 cm-1. This suggests that a value of mu' of .125 cm-1 may be appropriate for use in determining LVV in patients.

Adult↗
PubMed1985

Factors affecting ventricular volumes determined by a count-based equilibrium method.

Using a 99mTc-filled source ("ventricle") in an elliptical torso phantom, we analyzed the effect of source depth, region of interest (ROI) size, background concentration and source shape on volumes determined by an attenuation-corrected count-based equilibrium method. The calculated volume of a 96 cc sphere decreased linearly from 103 to 82 cc with increasing depth from 4 to 18 cm [vol = -1.48 X depth (cm) + 109, r = 0.99]. The calculated volume of the same sphere imaged at a depth of 9 cm increased from 98 to 117 cc with ROI sizes increasing from 161 to 1,369 pixels (1 pixel = 0.17 cm2). With increasing background concentration from 0-2 microCi/ml calculated volumes decreased from 95 to 85 cc (vol = -5.3 X background concentration (microCi/ml) + 95, r = 0.97). However, with correction for over-subtraction of background, increasing background activity caused no decrease in calculated volume (mean = 95 cc, s.d. = 1). Calculated volumes for the sphere and various cylinders were accurate, while those for cones were up to 37% lower for actual volumes ranging from 56-608 cc. This study demonstrates that multiple factors produce variability in count-based determination of phantom volumes. A careful consideration of the interaction of these factors with the edge-detection and computational algorithms is required.

Cardiac Output↗
PubMed1984

Relation between radionuclide angiographic regional ejection fraction and left ventricular regional ischemia in awake dogs.

Multigated equilibrium radionuclide angiography was used to quantitate global and regional ejection fraction (EF) in 26 awake dogs 10 minutes after distal and then proximal occlusion of the left anterior descending (LAD) or left circumflex (LC) coronary artery. Changes in global and regional EF were correlated with simultaneous measurements of the extent of acute left ventricular (LV) ischemia measured by radioisotope-labeled microspheres. The extent of ischemia, defined as the percentage of LV mass with greater than 25% reduction in blood flow from normal regional flow, was linearly related to the percent change in global EF after LAD (r = 0.84) and LC (r = 0.77) occlusions. The extent of ischemia also correlated with regional EF (r = 0.47 to 0.88 for LAD and r = 0.41 to 0.69 for LC occlusions). In 24 of 25 LAD occlusions and in all 20 LC occlusions that produced a measurable ischemic zone, the maximal percent change in regional EF exceeded the percent change in global EF. Two LAD occlusions and 2 LC occlusions reduced regional EF but not global EF. Thus, global and regional EF decreased in direct proportion to the extent of acute myocardial ischemia; regional ischemia produced greater changes in regional than in global EF.

Animals↗
PubMed1981

The effects of host sex on enteric response to infection with Trichinella spiralis.

The effects of host sex on enteric inflammatory response to primary infection with Trichinella spiralis were examined. Enteritis in female mice was greater than that in male mice on days 7, 9 and 11 postinfection (PI) and similar to that in male mice by day 13 PI. Male and female mice given daily injections of 33 or 66 mg/kilo of cortisone acetate exhibited significantly reduced enteritis on days 7, 9 and 11 PI below that seen in uninjected, male and female mice. On days 7, 9 and 11 PI larviposition in vitro by adult worms isolated from uninjected female mice was significantly less than that for adult worms isolated from male mice. Suppression of enteritis below detectable levels in male and female mice by administration of cortisone acetate resulted in similar rates of larviposition by adult worms isolated from male or female mice (day 7 PI, 33 mg/kilo cortisone acetate; days 7, 9 and 11 PI, 66 mg/kilo cortisone acetate). A significantly greater percent of adult worms was recovered from the anterior half of the small intestines of uninjected male than from uninjected female mice on days 7, 9 and 11 PI. The percent of adult worms recovered on these same days from the anterior half of the small intestine of male and female mice injected with cortisone was similar.

Animals↗