Catecholamine release during and after cross clamping of descending thoracic aorta.

During graft replacement of descending thoracic and thoracoabdominal aneurysms, aortic cross clamping without the use of bypass or shunts is accompanied by underperfusion of distal vascular beds. This study, comprising 10 patients, was based on the hypothesis that ischemia of the lower spinal cord and adrenal glands might precipitate release of catecholamines. Arterial blood samples, obtained before (control), during, and after arterial cross clamping, were analyzed for epinephrine (E) and norepinephrine (NE). The E/NE ratio was used as an index of ischemic sympathoadrenal activation. During cross clamping, mean E and E/NE increased by a factor of 4.5 (P = 0.03) and 2.4 (P = 0.001), respectively. The greatest increases were observed in the 5 min postclamp sample: relative to control, mean E increased 22-fold (P = 0.011), NE 3-fold (P = 0.009), and E/NE 8.4-fold (P = 0.013). During the immediate postclamp period, mean E/NE fell exponentially with an average "half-life" of 12.05 +/- 5.83 min (SD). A second-order polynomial related (P = 0.004) log E/NE in first postclamp sample to the ratio between clamp time and mean proximal arterial pressure during clamping (T/AP). Left-ventricular-minute-work-function correlations: (1) positive with log E during clamping (P = 0.043); and (2) none with log E (P = 0.563) or log (E + NE) (P = 0.641) 5 min post-clamp; (3) positive with log (E + NE) 30 min post-clamp (P = 0.016). It is concluded that (1) distal ischemia caused by cross clamping the descending thoracic aorta without bypass or shunts, results in distal regional sympathoadrenal activation, independent of known central reflex mechanisms; (2) this activation leads to marked increases of E/NE and is, in part, dependent upon T/AP during clamping; (3) the activation is probably transitory; (4) by indirect evidence, cardiodepressant factor(s) may transiently be present following declamping; (5) by its magnitude, sympathoadrenal activation is likely to provide compensation for deleterious factors that may affect cardiovascular functions during cross clamping and after declamping; alternatively, it might contribute to postoperative hypertension and cardiac complications such as myocardial ischemia and arrhythmias.

Graft replacement of aneurysm in descending thoracic aorta: results without bypass or shunting.

During the 24-year period from 1956 to 1980, 148 patients with aneurysms confined to the thoracic aortic segment, bounded above by the left subclavian artery and below the diaphragm, were treated with replacement therapy. From 1956 to 1967, 36 patients were treated by use of temporary bypass or shunts which carried a 6% incidence of paraplegia and a mortality rate of 22%. From 1962 to 1980, 112 patients were treated without shunts or bypass; this report is concerned with the latter cases. The incidence of paraplegia and the survival rate in this group were 0.9% and 91%, respectively. There were 89 men and 25 women in the series whose ages ranged from 22 to 87 years with an average age of 61. All types of aneurysms were represented; however, arteriosclerosis and dissection were the most common causes. The extent of aneurysm was variable, but most of the descending thoracic aorta was involved in more than half the cases. Associated diseases were present in 77% of cases. Operation consisted of aneurysmal replacement using inclusion technique with cardiac hemodynamics controlled by vasodilators and fluid replacement. During the past 4 years, proximal blood pressure has been controlled with nitroprusside. Cardiovascular hemodynamics, blood gases, electrolytes, and plasma osmolarity were monitored extensively and frequently to achieve the most desirable physiologic response to aortic clamping and operation. During this time 69 patients were treated. There were four (6%) deaths. None developed paraplegia or renal failure. Concomitant subclavian artery clamping was employed in 34 of these patients and in 22 additional patients with distal arch lesions. None in either group developed paraplegia. This indicated the safety of temporary subclavian artery occlusion. Death, both early and late, was due to a number of causes, but rupture of another aneurysm was the most common. This emphasizes the value of concomitant operation in patients with multiple aneurysms and careful follow-up in all patients.

Control and monitoring system for clinically employed pneumatic blood pumps.

Instantaneous position of the flexing member in pneumatic blood pumps is monitored on-line by measuring the electrical capacitance across the gas space within the pump. Monitor output is utilized in closed-loop pump control and for automatic pump shutdown in response to operational abnormalities. Thus, safety and efficacy are enhanced through operational optimization, automatic safety features, and facilitated evaluation.

Oxidized orlon as a blood interface.

Polyacrylonitrile fabric (Orlon) may by oxidized by heating in air, when it becomes black and carbonized. During the heat treatment, the fibers shrink; this shrinkage allows components such as diaphrams to be shaped around molds. Oxidation reduces the tensile strength by about 25% and also reduces the stiffness of the material. The oxidized Orlons was screened in tissue culture for possible cytotoxic effects. Finding none, patches of the material were sutured into the right atrium of dogs and examined after 48 hr. Because of encouraging results, 10 atrial patches, consisting of Dacron velour and oxidized Orlon side-by-side, were implanted into the right atrium of dogs. Five patches were backed with Silastic to render them impervious, and five with segmented polyurethane. The atrial patches were examined after 48 hr, and in all instances the oxidized Orlon part of the patch was coated with a thinner and smoother fibrin layer than was the Dacron velour half. a left ventricular bypass pump was fabricated from oxidized Orlon and spray-coated on the nonblood surface with segmented polyurethane. After 48 hr implantation in the chest cavity of a calf, pumping without systemic anticoagulation, the pump was found covered by a thin, smooth, firmly attached layer of fibrin.