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Biomedical subjects

D D Muehrcke

Publications and source records attributed to D D Muehrcke.

28 records · Page 2Linked to original sources
PubMed1991

Cardiac contraction affects deep myocardial vessels predominantly.

To evaluate the roles of intramyocardial forces and systolic ventricular pressure in myocardial flow in the different layers separately, we measured myocardial flow in rabbit hearts during stable systolic contracture with left ventricular pressures of 60 (n = 5) and 0 mmHg (n = 5) and during stable diastolic arrest (n = 5). We also measured the number and size of the intramyocardial vessels after perfusion fixation (systolic arrest, n = 5; diastolic arrest, n = 5). In 25 rabbits, hearts were excised and perfused from the aortic root. Systolic arrest was achieved by perfusion of a low-Ca2+ Tyrode solution containing 2.0 mM Ba2+. Diastolic arrest was achieved by intraventricular injection of 700-1,000 mg pentobarbital sodium and was maintained by perfusion with St. Thomas cardioplegic solution. At perfusion pressure of 100 mmHg, subendocardial flow was lower than subepicardial flow during systolic arrest regardless of left ventricular pressure, whereas during diastolic arrest, subendocardial flow was higher than subepicardial flow. Subendocardial-to-subepicardial flow ratios for a physiological range of perfusion pressures were lower during systolic arrest with low rather than with high left ventricular pressure. Small arteriolar and capillary densities showed no difference between subendocardium and subepicardium. During systolic arrest, diameters of subendocardial terminal arterioles (4.6 +/- 1.3 microns) and capillaries (4.0 +/- 1.3 microns) were smaller than those in the subepicardium (8.8 +/- 1.7 and 7.1 +/- 1.6 microns, respectively; P less than 0.0001), whereas during diastolic arrest, diameters of subendocardial terminal arterioles (10.1 +/- 2.0 microns) and capillaries (7.6 +/- 1.8 microns) were slightly larger than those in the subepicardium (9.5 +/- 1.5 and 6.7 +/- 1.0 microns, respectively; P less than 0.01). We conclude that cardiac contraction predominantly affects subendocardial vessels and impedes subendocardial flow more than subepicardial flow regardless of left ventricular pressure.

Animals↗
PubMed1990

Nonuniform blood flow in the canine left ventricle.

In order to investigate the relationship between coronary perfusion pressure and blood flow distribution in the left ventricle (LV), we measured myocardial blood flow in small regions using radioactive microspheres in six anesthetized, open-chest dogs. Mean coronary perfusion pressure (CPP) was controlled with a femoral artery to left main coronary artery shunt which included a pressurized, servo-controlled blood reservoir. In each dog, we measured flow in 192 regions of the LV free wall (mean weight per region = 206 +/- 38 mg) at different perfusion pressures. At CPP = 80 mm Hg, blood flow to individual regions varied fourfold (0.30 to 1.18 ml/min/g; relative dispersion (RD) = 21.8 +/- 2.3%). At CPP = 50 mm Hg, flow varied over sevenfold (0.08 to 0.60 ml/min/g; RD = 42.8 +/- 10%; P less than 0.01 vs 80 mm Hg). This relationship between flow variability and CPP was present within individual LV layers as well between layers and is much higher than the error associated with the microsphere technique. We conclude that blood flow to small regions of the LV is markedly nonuniform. This heterogeneity becomes more profound at lower CPP. These findings suggest that (1) global measurements of coronary flow must be interpreted with caution, and (2) even in hearts with normal coronary arteries some regions of the LV are more susceptible to ischemia than others. In addition, these findings may help explain the patchy nature of myocardial damage that occurs following periods of low coronary pressure or inadequate myocardial protection during cardiopulmonary bypass.

Animals↗
PubMed1989

Complications after esophagogastrectomy using stapling instruments.

We studied 195 patients undergoing esophageal resection using stapling instruments during a period of over 8.5 years. Of these, 178 (91.2%) underwent operation for malignant disease. Operative death occurred in 19 patients (9.7%). Nine (4.6%) postoperative complications, excluding stricture formation, were related to the use of stapling instruments, including two operative deaths (1.0%). Anastomotic leaks and gastrotomy staple line leaks were the most common complications (four each). In 7 patients (3.6%) the circular stapler tore the esophagus; anastomotic leaks subsequently developed in 43% of these patients. After we began oversewing gastrotomy staple lines in 1984, we experienced only one gastrotomy leak due to a technical error. Postoperative stricture formation occurred soon after resection and responded well to one or two dilations. It is better to err on the side of choosing too small a stapling head when performing an esophageal anastomosis because this may reduce the incidence of leaks, and further strictures are easily dealt with.

Adult↗
PubMed1989

Use of pericardium to control bleeding after ascending aortic graft replacement.

We present the case of a patient who required replacement of an ascending aortic composite graft for endocarditis complicated by uncontrollable bleeding from the proximal anastomotic site. A new method of creating a right atrial-to-periprosthetic space fistula with autologous pericardium was used with a favorable result.

Anastomosis, Surgical↗
PubMed1989

Oesophagogastrectomy in patients over 70.

Although the results of oesophageal resection for benign and malignant disease are well documented, the risk of operative death and long term survival in patients over the age of 70 is not well defined. The outcome has been reviewed for 46 patients (23 male, 23 female) aged 70 years or more (mean 74 years) undergoing oesophageal resection during a period of seven years; 16 patients were 75 years or over. All resections were performed with the EEA stapler, except for one cervical anastomosis that was stitched by hand. In 42 patients resection was for malignancy. Six patients died within 30 days of operation or during the initial hospital stay, giving an operative mortality of 13%. Only one of the 16 patients aged 75 years or more died. Cardiopulmonary complications accounted for most of the operative deaths. Patients were scored retrospectively by a multifactual risk factor. Patients who left hospital had a mean preoperative score of 3.66, compared with 15.2 for those who died. Use of such a score may help to improve selection for surgery in this age group. It is concluded that oesophagogastrectomy may be performed in selected patients over the age of 70 years with acceptable mortality, morbidity, and length of hospital stay.

Adenocarcinoma↗
PubMed1989

Anastomotic narrowing after esophagogastrectomy with the EEA stapling device.

We studied a series of 176 patients undergoing esophageal resection with the aid of the EEA surgical stapling device (Auto Suture U.K. Limited, Great Britain) during a period of 7 1/2 years. A total of 160 patients (91%) were operated on for malignant disease. Operative death occurred in 15 patients (8.5%), and there were three anastomotic leaks (1.7%). The prevalence of dysphagia caused by both benign and malignant strictures after esophageal resection in which the EEA stapler was used was 17.4%. The rate of benign anastomotic narrowing in discharged patients was 12.5%. Anastomotic stricture resulting from recurrent tumor caused dysphagia in 6.2% of the patients undergoing resection for malignant disease. The highest rate of benign anastomotic narrowing occurred in patients who had undergone esophageal resection for benign, nondilatable strictures. In these patients, the prevalence of benign anastomotic narrowing was 37.5%, compared with 9.6% in the patients undergoing resection for malignant disease (p less than 0.001). An additional trend was noted: The smaller the stapling head used to construct the anastomosis, the higher the prevalence of benign anastomotic narrowing; however, a statistically significant difference could not be documented. Ninety-five percent of patients with benign anastomotic narrowings complained of dysphagia within the first 6 months after the operation; 79% of these patients required two or fewer dilatations to relieve the dysphagia. Dysphagia after esophageal resection with the aid of EEA stapler occurred in just over one of six patients. The usual cause of the dysphagia was benign anastomotic narrowing, which responds well to dilatation.(ABSTRACT TRUNCATED AT 250 WORDS)

Anastomosis, Surgical↗
PubMed1988

Carcinoma of the bronchus with unsuspected microscopic resection-line involvement.

In a series of 560 pulmonary resections for bronchial carcinoma, unsuspected microscopic tumor was present at the bronchial resection margin in 26 patients (4.5%). Adjuvant chemotherapy or radiotherapy was given in two patients. In follow-up times ranging from 1 to 72 months (mean, 22 months), 58% of patients were alive and free of recurrent disease. Twelve patients underwent periodic surveillance bronchoscopy in an attempt to identify early local recurrence. Eighty-three percent of these patients were alive and disease-free in follow-up times from 4 to 72 months (mean, 29.7 months). Only one choscopies. It was concluded that microscopic residual resection-line tumor does not preclude prolonged survival and that no benefit from surveillance bronchoscopy could be demonstrated in this small patient sample.

Bronchi↗
PubMed1987

Pediatric splenic trauma: predicting the success of nonoperative therapy.

The charts of all pediatric patients discharged from the Massachusetts General Hospital with a diagnosis of a ruptured spleen were reviewed over a six-year period to determine if any factors could be used to predict which children could be managed safely without operation. Seventy-five percent of these injuries were so managed. The patients who required surgical intervention were older (mean age, 17 years), had multiple injuries (mean ISS, 41), presented with more blood loss (mean hematocrit, 23.5%), and suffered their injuries as a result of a motor vehicle accident. The patients who were successfully managed nonoperatively were younger (mean age, 12 years), had fewer associated injuries (mean ISS, 18), required fewer blood transfusions, and suffered their traumas secondary to falls, sporting events, or altercations. We propose that the injury severity score, the number of units of blood transfused, patient age, as well as the type of trauma suffered be used to predict which patients can be safely managed nonoperatively.

Abdominal Injuries↗