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Biomedical subjects

J W Meredith

Publications and source records attributed to J W Meredith.

69 records · Page 4Linked to original sources
PubMed1985

Myocardial biopsy drill: construction details and techniques.

The modification of currently available dental equipment to construct a myocardial biopsy drill by the technique of Poole et al. (P. E. Poole, G. F. Norris, R. M. Lewis, and J. W. Covell, J. Appl. Physiol. 24: 832, 1968) is described. In dogs, five to seven full-thickness myocardial cores 3 mm in diameter and weighing 40 to 70 mg could be obtained consistently with the drill without affecting left ventricular function. The positive pressure/negative pressure system allowed separation of contaminating blood from the myocardial sample and rapid myocardial freezing. Assessment by a modification of the technique of Estabrook et al. (R. W. Estabrook, J. R. Williamson, R. Frenkel, and P. K. Maitra, In R. W. Estabrook and M. E. Pullman (Eds.), Methods in Enzymology, New York: Academic Press, 1967. Vol. 10, p. 474). yielded myocardial ATP levels of 32.12 +/- 0.90 nmole/mg of protein.

Adenosine Triphosphate↗
PubMed1984

Comparison of suture technique on patency of polytetrafluoroethylene-microarterial anastomoses.

Polytetrafluoroethylene (PTFE) grafts, 1 mm in internal diameter, were interpositioned in the infrarenal aortas of 20 adult Sprague-Dawley rats with either continuous or interrupted sutures. The interrupted-suture (I-S) technique was used in ten rats, the continuous-suture (C-S) technique in the other ten. After followup of 90 days, the overall patency rate for the 20 rats was 95% (19/20); all grafts in the C-S group were patent; one graft in the I-S group had occluded on the day of operation. Since excellent patency rates were obtainable with these minute PTFE grafts placed in the rat aorta by either technique, the speed with which the C-S technique can be accomplished appears to make it preferable.

Animals↗
PubMed1984

Abdominal wound closure. A comparison of polydioxanone, polypropylene, and Teflon-coated braided Dacron sutures.

A midline abdominal wound was made in 135 Harlan Sprague-Dawley rats, and the fascia was then closed by the continuous suture technique with 4-0 absorbable monofilament polydioxanone sutures (n = 45 rats), 4-0 permanent monofilament polypropylene sutures (n = 45 rats), or 4-0 Teflon-coated braided Dacron sutures (n = 45 rats). At 1-, 2-, and 6-month intervals, wound-bursting pressures were determined in 15 animals from each group. At 1 month and at 6 months, there was no significant difference in wound-bursting strength among the three types of sutures. At 2 months, wounds closed with Teflon-coated braided Dacron were significantly stronger than wounds closed with the other types of sutures. In most of the braided Dacron suture animals, the fascia burst in areas other than the abdominal wound, indicating that the wound was stronger at that time than was the surrounding fascia. There is no advantage to that added strength, and braided Dacron sutures have been shown to cause greater tissue reaction than monofilament sutures. Therefore, except in patients with poor wound healing who are highly susceptible to dehiscence and in whom permanent low-tissue-reaction sutures may be beneficial, the authors recommend a running suture technique using absorbable monofilament suture, such as polydioxanone, for the routine closure of clean abdominal wounds.

Abdomen↗
PubMed1984

Suture technique and wound-bursting strength.

Despite advances in wound healing, fascial dehiscence continues to be a problem in celiotomy wounds. Experimental and clinical studies on suture material and on patient-related factors in wound disruption are abundant, but little attention has been given to mechanical factors in wound closure, although they may be of greater importance. A midline abdominal wound was made in 120 Harlan Sprague-Dawley rats, and the fascia was closed with Dacron in one of six ways: simple interrupted, interrupted figure-of-eight, and running, each tied loosely in one half of each group and tightly in the other half. One week later, the rats were reanesthetized and wound-bursting strength was measured. In general, the running suture technique resulted in the greatest wound-bursting pressures. A loosely tied figure-of-eight technique was nearly as good as a loosely tied running stitch, but tying figure-of-eight sutures tightly caused a significant decrease in wound-bursting pressure. The simple interrupted technique was unaffected by suture tension but was generally inferior to the running stitch in terms of wound-bursting strength. Histologic studies were performed, but most of the disparity in wound strength among the suture techniques apparently was due solely to mechanical factors. Closing midline abdominal fascial wounds with a running suture may be a superior method of closure in clean, incised wounds.

Abdomen↗
PubMed1984

Inhibition of platelet deposition on polytetrafluoroethylene grafts by antiplatelet agents.

The effects of ibuprofen (Motrin), dipyridamole (Persantine), and prostacyclin on the deposition of platelets on polytetrafluoroethylene grafts (5.5 cm long, 4 mm internal diameter implanted into both femoral arteries of 21 dogs) were studied by harvesting autologous platelets, labeling them with 51Cr, and reinjecting them 15 minutes before cross-clamping. Arterial flow was adjusted to 65 ml/min and monitored continuously. Ibuprofen (12.5 mg/kg) and dipyridamole (2.5 mg/kg) were each administered as a single intravenous injection in four dogs (eight grafts) and five dogs (10 grafts), respectively. Prostacyclin (50 ng/kg/min) was administered by continuous intravenous infusion in five dogs (10 grafts). Seven dogs (14 grafts) served as controls. Grafts were removed 2 hours after implantation, and radioactivity (counts per 10 minutes) was determined in four segments of each graft (including both anastomoses) with a gamma-counter. Counts were averaged for each group of dogs. Significance was calculated by the Student t test. Platelet deposition in control dogs averaged 10,033.9 +/- 1134.2 SE; that in prostacyclin-treated dogs averaged 2513.7 +/- 276 SE (p less than 0.001); that in ibuprofen-treated dogs averaged 5453.4 +/- 1336.3 SE (p = 0.02); that in dipyridamole-treated dogs averaged 11,213.7 +/- 1632.5 SE (p = 0.55). These data demonstrate the effectiveness of prostacyclin and ibuprofen in reducing platelet deposition on polytetrafluorethylene grafts in dogs.

Animals↗
PubMed1983

Surgical implications in malignant cardiac disease.

Despite the rarity of primary malignant tumors of the heart (0.0017 to 0.03% of large postmortem series) and the infrequency of clinical signs and symptoms (0 to 50%) of the more common metastatic cardiac tumors, many cardiothoracic surgeons at some time will encounter a patient with one of these two conditions. A review of the medical literature yielded 28 cases of primary cardiac tumors, 10 of secondary tumors, and 12 of carcinoid heart disease treated surgically and followed sufficiently for retrospective evaluation. We summarized those cases and made the following conclusions. Primary malignant tumors of the heart are occasionally resectable, although cure is unlikely; survival may be enhanced by postoperative irradiation but probably not by postoperative chemotherapy. For patients with secondary malignant tumors of the heart, surgical intervention is rarely of benefit except for establishing a tissue diagnosis, effecting artificial cardiac pacing, decompressing symptomatic pericardial effusions, or reducing an obstructive tumor mass. Patients with carcinoid heart disease affecting the valves may derive benefit from valve replacement or repair. Thus, in selected patients with malignant cardiac disease, surgical intervention may be feasible and should always be among the therapeutic options considered.

Adult↗
PubMed1983

The diagnosis of aortoiliac disease. A noninvasive femoral cuff technique.

An inexpensive femoral "cuff" developed in this noninvasive vascular laboratory allows pulse volume recordings and systolic pressure measurements of the femoral arteries. Using the parameters 1) femoral/brachial systolic pressure ratio, 2) wave amplitude, and 3) status of the dicrotic notch for assessment of results, it was found that the cuff correctly identified 59 of 62 limbs with at least 50% aortoiliac stenosis, with only two false-positive results, for an accuracy of 97%. The high, wide thigh cuff identified 57 of the 62 limbs, but had 45 false-positive results (77% accuracy). Use of the femoral "cuff" has refined the ability to identify the anatomic location of significant arterial stenoses in the lower extremities.

Adult↗
PubMed1983

Measurement of extravascular lung water in sheep during colloid and crystalloid resuscitation from smoke inhalation.

The pathophysiology of pulmonary inhalation injury, a major cause of morbidity and mortality from fires, is poorly understood. To examine the effects of colloid and crystalloid resuscitation on extravascular lung water (EVLW) during a standard smoke inhalation injury, we subjected 12 sheep to 8 minutes of cool pine smoke inhalation. The animals were then resuscitated to a pulmonary capillary wedge pressure (PCWP) of 10 +/- 1.5 mm Hg with either lactated Ringer's solution or plasma protein derivative. EVLW, cardiac output, vascular resistance, colloid oncotic pressure (COP), arterial and pulmonary artery pressures, PCWP, and blood gases were monitored during 4 hours of resuscitation. In colloid-treated animals, EVLW increased from 8.3 +/- 1.2 to 11.1 +/- 0.9 ml/kg with injury; it increased only to 12.5 +/- 1.3 ml/kg during resuscitation. In crystalloid-treated animals, EVLW increased from 8.0 +/- 1.0 to 10.3 +/- 0.8 ml/kg with injury and further increased to 17.4 +/- 1.6 ml/kg during resuscitation, a level significantly higher than that in the colloid group (P less than 0.05). The increases in EVLW were associated with progressive hypoxia, which was worse in the crystalloid group. In the crystalloid group, COP decreased from 27.3 +/- 0.9 to 14.2 +/- 0.4 mm Hg and intravascular driving force (COP-PCWP) dropped from 17.6 to 3.26 +/- 1.5 mm Hg; COP and COP-PCWP were maintained in the colloid group. These data demonstrate that supporting serum COP minimizes the increase in EVLW with smoke inhalation injury and suggests that smoke inhalation does not lead to a dramatic increase in alveolar capillary membrane permeability to protein.

Animals↗
PubMed1983

Is a left ventricular vent necessary for coronary artery bypass operations performed with cardioplegic arrest?

The need for ventricular venting with hypothermic cardioplegic arrest is controversial. We report an evaluation of the need for left ventricular venting in a canine model that closely simulates conditions during routine coronary artery bypass grafting (CABG). Thirty-five dogs were placed on cardiopulmonary bypass for 60 minutes of hypothermic cardioplegic arrest (18 vented, 17 nonvented) and then reperfused for 30 minutes. Myocardial temperature and left atrial pressure (LAP) were recorded continuously. Before and 30 minutes after hypothermic cardioplegic arrest, left ventricular function curves were generated (six vented, six nonvented), and biopsy specimens of the left ventricle were taken for adenosine triphosphate (ATP) determinations (11 vented, 10 nonvented) and semiquantitative grading of mitochondrial ultrastructure (six vented, six nonvented). LAP in nonvented dogs was 7.4 mm Hg during hypothermic cardioplegic arrest and 5.0 mm Hg during reperfusion. Temperature during hypothermic cardioplegic arrest was 12.3 degrees C in vented dogs and 11.3 degrees C in nonvented dogs (p = 0.5). There were no differences in left ventricular function or preservation of mitochondrial ultrastructure between vented and nonvented dogs. ATP after hypothermic cardioplegic arrest was 96.6% of control (4.30 microM/gm) in vented dogs and 94.6% (4.37 microM/gm) in nonvented dogs (p = 0.7). The absence of left ventricular venting did not lead to ventricular distention or more rapid rewarming. These data in vented dogs and nonvented dogs strongly support the belief that left ventricular venting is not necessary during routine CABG.

Adenosine Triphosphate↗
PubMedDate not supplied

Occult pneumothorax in patients with abdominal trauma: CT studies.

Abdominal CT, which routinely includes the lower thorax, is an important adjunct to supine chest radiography in detecting chest injury in patients with blunt abdominal trauma. In 1,086 consecutive patients with blunt abdominal trauma, 223 of whom had both supine chest radiography and abdominal CT, 49 patients examined with both techniques had pneumothoraces, 28 of them occult (seen only on CT). To help guide management, we established three categories of occult pneumothorax, based on size and location: (a) minuscule (< 1 cm in greatest thickness, seen on four or fewer images); (b) anterior (> 1 cm in greatest thickness, but not extending beyond the midcoronal line); (c) anterolateral (extending beyond the midcoronal line). In our study four of six patients with minuscule pneumothorax, including one who required mechanical ventilation, were observed without complications; two of six patients had chest tube placement. Seven of 14 cases with anterior pneumothorax were observed and resolved without complication; seven had chest tube placement. All eight patients with anterolateral pneumothoraces underwent percutaneous tube thoracostomy, regardless of proposed management.

Abdominal Injuries↗