Biomedical subjects
Publications and source records attributed to M J Botham.
A case of primary cardiac non-Hodgkin's B cell lymphoma is described in a patient presenting with obstructive right heart failure. Unlike the majority of cases, in this case the tumor was diagnosed ante mortem. THe patient's history combined with the aggressive use of noninvasive echocardiography are helpful in diagnosing this rare lesion.
Correction of congenital esophageal atresia and tracheoesophageal fistula (TEF) with either a primary or staged repair may result in recurrence of the TEF, most often at the site of esophageal anastomosis. Definitive operative repair of a recurrent TEF involves isolation and resection of the fistula with closure of the tracheal and esophageal defects. A technique is described, whereby mobilization of a vascularized pedicle of pericardium allows further enhancement of the standard repair of a recurrent TEF. The vascularized pedicle of pericardium serves to isolate the tracheal and esophageal suture lines from each other, as well as aid in sealing leaks at either or both suture lines. This may dramatically reduce the incidence of second recurrences and lower the overall operative mortality, reportedly as high as 59%.
The ability of a chronic high-salt diet to prevent fatal hemorrhagic shock was examined in 36 mongrel dogs. Twenty-one dogs received a dietary supplement of 9 g sodium chloride/day for 6 wk, and 15 dogs received the same basic diet for 6 wk but without the sodium chloride supplement. Hemorrhagic shock was induced in all dogs by bleeding into an overhanging sealed reservoir. After 3 h of shock, salt-pretreated dogs had a lower systemic vascular resistance of 0.70 +/- 0.02 versus 1.44 +/- 0.04 mmHg X ml-1 X min X kg (P less than 0.01) and a higher cardiac output of 53 +/- 3 versus 26 +/- 3 ml X min-1 X kg-1 (P less than 0.01) than was observed in controls. At 2.5 h of shock, the salt-pretreated dogs also experienced an increase in gastrointestinal (P less than 0.01), hepatic arterial, (P less than 0.05), kidney (P less than 0.05), brain (P less than 0.01), and heart blood flows (P less than 0.001) compared with 0.5 h of shock, whereas the control dogs experienced no increased flow during this same period. We also observed that after 3 h of hypotension there was a significantly smaller increase in plasma renin activity in the salt-pretreated dogs. Administration of 0.1 U X kg-1 X min-1 of hog renin eliminated the differences in systemic vascular resistance, cardiac output, and survival in five salt-pretreated dogs.
The relationship between epicardial and transmural function (measured with sonomicrometers) was examined in 13 anesthetized open-chest dogs. Systolic wall thickening was used as a standard of integrated transmural function to compare with epicardial function measured as segment shortening parallel to surface fibers. Three levels of coronary inflow restriction were produced by using decrements in systolic wall thickening as an index of changes in the transmural distribution of myocardial blood flow (microspheres) in myocardium perfused by the left anterior descending artery (anterior-apical group, n = 7) or circumflex artery (posterior-basal group, n = 6). Levels 1 and 2 were characterized by reductions in systolic wall thickening of 35% and 80%, respectively, and marked decreases in deep myocardial blood flow. In the subepicardium, myocardial blood flow was minimally affected at levels 1 and 2 and there was no change in posterior-basal epicardial segment shortening, but anterior segment shortening decreased significantly (by 21% and 37%, respectively). At level 3 myocardial blood flow was reduced transmurally, producing systolic wall thinning and marked epicardial dysfunction in both groups. Parallel epicardial segment shortening underestimated the extent of transmural dysfunction in both groups at levels 1 and 2 but the degree of underestimation was greatest in the posterior-basal group. Anterior-apical segment shortening was impaired at levels 1 and 2, whereas posterior-basal segment shortening was unaffected, suggesting that significant regional variability exists in the epicardial response to nontransmural ischemia.
Seventy adult patients with thoracic empyema were treated at the University of Michigan Medical Center between 1978 and 1982. Twenty-two (31%) of the empyemas were associated with pneumonia, 23 (33%) occurred as postoperative complications, and seven (10%) were iatrogenic. When used as the initial mode of drainage, repeat thoracentesis was successful in only four of 11 cases (36%). Similarly, closed tube thoracostomy, as initial treatment, was successful in only 14 of 40 cases (35%). Rib resection, however, provided cure or control in 10 of 11 patients (91%) when employed as the first treatment method. Eight of 12 patients (67%) with parapneumonic empyemas were treated successfully with closed tube thoracostomy, in contrast to only two of 17 patients (12%) with postoperative empyemas so treated. Eventual control or cure of empyema was achieved in 57 patients (81%), whereas 13 (19%) died (five from their empyema and eight with empyema as an active problem at the time of death). All of the five empyema-caused deaths occurred in patients who underwent chest tube drainage as the most invasive treatment modality. The mortality rate for immunosuppressed patients was 40% (four of 10 patients). This analysis of a large recent series of adult empyemas suggests that chest tube drainage is often inadequate and more aggressive management is likely to result in fewer treatment failures and fewer total procedures. Early rib resection, especially for postoperative empyemas and those in immunocompromised patients, is recommended.
The effects of experimental right ventricular (RV) pressure overload and RV hypertrophy on coronary vasodilator reserve in young animals is not well established. Therefore, we measured coronary vasodilator reserve in the right ventricle of dogs from 7 to 12 months old with moderate RV hypertrophy due to pulmonary artery banding performed 3 to 7 days after birth. In the 5 dogs with pulmonary artery banding, substantial RV hypertension developed (RV pressure at rest, 73 +/- 11 mm Hg) as did RV hypertrophy (ratio of RV free wall/left ventricular free wall weight, 1.86 +/- 0.41 gm/kg). The reactive hyperemic response following brief coronary occlusions was used as an index of coronary vasodilator reserve. The ratios of peak reactive hyperemic response to resting flow, however, were not significantly different in the 5 banded dogs compared with 7 control animals (3.6 +/- 1.0 versus 2.6 +/- 0.6); this implies that the extent of vasodilator reserve was similar with or without moderate RV hypertrophy. In addition, myocardial blood flow, as determined using radioactive microspheres, was not significantly different at rest: 0.57 +/- 0.09 ml/min per gram in the banded dogs versus 0.48 +/- 0.12 ml/min per gram in the controls. Uniform transmural distribution of blood flow was maintained during infusion of isoproterenol, which was used to increase myocardial oxygen requirements in both groups. Minimum coronary vascular resistance was significantly lower in the banded than the control dogs (1.5 +/- 0.6 versus 6.2 +/- 2.3; p less than 0.01). This difference suggests that the cross-sectional area of the right coronary vascular bed increased with the development of RV hypertrophy.
A complication of cardiac surgical procedures is postoperative low cardiac output syndrome. Treatment with norepinephrine plus phentolamine (N + P) is beneficial, but the effect of these agents on regional organ blood flow has not been evaluated. Therefore, in 6 dogs with long-term instrumentation, pentobarbital was infused to simulate low cardiac output (32 + 10% of the conscious control level). Infusions of N + P at 0.2, 0.5, and 1.0 microgram/kg/min restored cardiac pump performance to conscious control levels. Regional blood flows, determined with tracer-labeled microspheres, were substantially reduced in the low cardiac output state but increased to values not markedly different from control levels in all organs studied except stomach fundus during infusion of N + P. The pressure-work index, an indirect measure of myocardial oxygen consumption, did not increase to more than the conscious level except at the highest dose. The data demonstrate that simultaneous infusion of N and P is capable of successfully improving cardiac pump performance with restoration of vital organ perfusion and without evidence of excessive myocardial oxygen consumption.