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Biomedical subjects

J D Sink

Publications and source records attributed to J D Sink.

At least 55 records · Page 3Linked to original sources
PubMed1979

The effects of hypothermia on myocardial oxygen consumption and transmural coronary blood flow in the potassium-arrested heart.

Hypothermia remains the primary adjunct employed to lower cellular metabolism during various cardiac procedures. In these experiments, left ventricular myocardial oxygen consumption (MVO2) and transmural blood flow (TBF) were measured during cardiopulmonary bypass with the range of temperatures used clinically. Determinations were made in empty beating normothermic hearts and after potassium cardioplegia at 37, 32, 28, 22, 18, and 15 degrees (K+ = 15--37 meq/L: Hct 25 volumes %). Oxygen content of the total coronary sinus collection was compared with a large volume arterial sample using a Lex-O2-Con-TL analyzer (vs Van Slyke, R = 0.98). Transmural blood flow was measured at each temperature using microspheres (8 microns), and perfusion was maintained at 80 mmHg. Asystole (37 degrees) alone decreased MVO2 from 5.18 +/- 0.55 to 1.85 +/- 0.20 ml O2/min/100 g of left ventricle or approximately 65% (p less than 0.001). With progressive cooling to 15 degrees an additional 82% decrement in oxygen uptake occurred during asystole (p less than 0.001). During asystole at 37 degrees the decrease in MVO2 was reflected mainly by a large decrement (p less than 0.01) in TBF (1.27 +/- 0.19 to 0.74 +/- 0.17 ml/min/g of mean left ventricular flow). However, with cooling below 32 degrees, the arteriovenous oxygen difference narrowed progressively (p less than 0.001) while TBF paradoxically returned to control levels. Endocardial/epicardial flow ratios were not altered by cooling. These data not only confirm earlier reports describing a sequential drop in MVO2 with incremental myocardial cooling, but also establish MVO2 levels for perfused hearts arrested by potassium at lower temperatures (18--15 degrees). Moreover, as transmural blood flow becomes independent of metabolic necessity during hypothermia, coronary autoregulation appears to be impaired, possibly affecting detrimental tissue over perfusion.

Animals↗
PubMed1979

Protection of mitochondrial function during ischemia by potassium cardioplegia: correlation with ischemic contracture.

The effect of potassium cardioplegia on mitochondrial function was evaluated in the ischemic isolated rat heart. Mitochondrial function as well as adenosine triphosphate (ATP) levels were determined at the initiation of ischemic contracture, at the completion of ischemic contracture, and 20 minutes following contracture completion. Group I received no cardioplegia prior to ischemia, while Group II received potassium cardioplegia prior to the onset of ischemia. The respiratory control index (RCI), which is the primary measure of the intactness of mitochondrial function, was calculated with both a NAD (nicotinamide adenine dinucleotide)-linked substrate and a FAD (flavin adenine dinucleotide)-linked substrate. Potassium cardioplegia significantly delayed ischemic contracture initiation and completion. Although the RCI and ATP levels decreased significantly at successive levels of contracture, there was no difference in the RCI or ATP content between Group I and Group II at contracture initiation or completion. Unlike previous investigations that have used a time-base to examine mitochondrial function and acute cardiac ischemic injury, we correlated mitochondrial function with the measurable physiologic event ischemic contracture. The data indicated that potassium cardioplegia preserved ATP content and mitochondrial function, and that contracture initiation and completion correlate well with specific ATP levels and mitochondrial respiratory control. The relationship between mitochondrial function and ATP content indicates that the beneficial effect of potassium cardioplegia on mitochondrial function may be secondary to the preservation of high-energy phosphate levels which provide energy for mitochondrial maintenance.

Adenosine Triphosphate↗
PubMed1979

Effects of phenylephrine on transmural distribution of myocardial blood flow in regions supplied by normal and collateral arteries during cardiopulmonary bypass.

Cardiopulmonary bypass is frequently accompanied by decreased peripheral vascular resistance with resultant hypotension that is unresponsive to increased flow rates. Alpha adrenergic agonists are routinely used to increase peripheral vascular resistance and augment blood pressure. In this study, the effects of the alpha adrenergic stimulant phenylephrine on blood flow distribution during cardiopulmonary bypass in myocardium supplied by normal and collateral arteries were studied in eight mongrel dogs. Microsphere determinations of blood flow were made following augmentation of perfusion pressure with phenylephrine and were compared with intraoperative normotensive and hypotensive control levels. With systemic flow rates held constant, phenylephrine was infused in doses adequate to raise perfusion pressure to normotensive levels following hypotension. In the normal region (NR), blood flow was returned to normotensive control levels with flow favoring the subendocardium. In the region supplied by collateral vessels (CR), however, phenylephrine infusion failed to return flow to the normotensive control level in the subendocardial layer, and the flow imbalance present during hypotension was not corrected. An analogue model of the calculable resistances in the CR is presented, which indicates that phenylephrine increased resistance in the collateral vessels. Associated with this inflow restriction is decreased resistance or vasodilatation of the intramyocardial vessels supplied by collateral coronary arteries.

Animals↗
PubMed1978

Cloacogenic carcinoma.

Cloacogenic carcinoma is a rare tumor of the anorectal region originating from a persistant remnant of the cloacal membrane of the embryo. The tumor accounts for 2-3% of anorectal carcinomas and occurs more than twice as often in women. Most tumors present as fungating or ulcerating lesions, but the tumor may arise in anal ducts and present as a submucosal mass. Wide abdominoperineal resection is the treatment of choice with a five year survival of 50%. Metastases occurs to the inguinal lymph nodes in more than 50% of the patients at sometime during the course of the disease with distant metastases occuring most commonly to liver and lungs.

Anus Neoplasms↗
PubMed1976

Evaluation of catheter placement in the treatment of venous air embolism.

Venous air embolism is a potential complication of many surgical, therapeutic, and diagnostic procedures. Aspiration of air via a catheter placed in the superior vena cava or right atrium or placed in the pulmonary outflow tract and pulled through the right heart chambers had been advocated for the treatment of venous air embolism. In this study, three catheter positions were analyzed to determine which was best for removal of gas after induction of massive venous air embolism in dogs. In 18 dogs, 9 of which were suspended by their forelegs to simulate the sitting position used in posterior fossa exploration and 9 of which were supine, a Swan-Ganz catheter was placed in the right atrium, right ventricle, or pulmonary artery. A measured amount of air was injected into the left jugular vein and syringe aspiration of the air was attempted through the catheter. In the group with the catheter in the pulmonary artery, aspiration was continuous while the catheter was withdrawn through the right heart chambers. The amount of air aspirated varied widely among the three catheter positions, and no one catheter position proved superior to the other two.

Animals↗
PubMed1976

Ruptured abdominal aortic aneurysms: review of 33 cases treated surgically and discussion of prognostic indicators.

Over an eight-year peroid at NCBH, 33 patients were operated for ruptured abdominal aortic aneurysm. Factors associated with an increased mortality included preoperative blood urea nitrogen levels of more than 20 mg per cent, severe preoperative hypotension, duration of symptoms of less than 24 hours, free peritoneal rupture and blood transfusions of greater than 19 units. Preoperative hypotension was the most selective preoperative prognostic parameter. From a review of this and other reported series, it was concluded that reduced mortality from ruptured abdominal aortic aneurysm can best be achieved by prompt diagnosis followed by surgical treatment before cardiovascular collapse can occur.

Aged↗