Spaceflight and protein metabolism, with special reference to humans.

Human space missions have shown that human spaceflight is associated with a loss of body protein. Specific changes include a loss of lean body mass, decreased muscle mass in the calves, decreased muscle strength, and changes in plasma proteins and amino acids. The major muscle loss is believed to be associated with the antigravity (postural) muscle. The most significant loss of protein appears to occur during the first month of flight. The etiology is believed to be multifactorial with contributions from disuse atrophy, undernutrition, and a stress type of response. This article reviews the results of American and Russian space missions to investigate this problem in humans, monkeys, and rats. The relationship of the flight results with ground-based models including bedrest for humans and hindlimb unweighting for rats is also discussed. The results suggest that humans adapt to spaceflight much better than either monkeys or rats.

Improvement in circulatory and oxygenation status by perflubron emulsion (Oxygent HT) in a canine model of surgical hemodilution.

To examine the effect of a low dose of Oxygent HT on hemodynamics and oxygen transport variables in a canine model of profound surgical hemodilution, two groups of adult anesthetized splenectomized beagles were hemodiluted with Ringer's solution to Hb 7 g/dL. The treated group received 1 mL/kg Oxygent HT (90% w/v perflubron emulsion [perfluorooctyl bromide], Alliance Pharmaceutical Corp.) and both groups (7 controls and 10 treated) were further hemodiluted using 6% hydroxyethyl starch until cardiorespiratory decompensation occurred. Pulmonary artery catheterization data and oxygen transport variables were recorded at Hb decrements of 1 g/dL breathing room air. There was no difference among groups during initial hemodilution. However, in the Oxygent HT group there was a statistically significant improvement in mean arterial pressure, CVP, cardiac output, PvO2, SvO2, DO2, and pulmonary venous admixture shunt during profound hemodilution to Hb levels of 6, 5, and 4 g/dL. A low dose of Oxygent HT offered benefit in improving hemodynamics and oxygen transport parameters even under air breathing conditions in a model of surgical hemodilution. This effect was most apparent at lower levels of Hb.

Simultaneous coronary artery bypass and carotid endarterectomy. Determinants of outcome.

From January of 1988 to May of 1993, simultaneous single-stage coronary revascularization and carotid endarterectomy was performed in 33 patients (mean age, 69 years). Thirty-one patients (94%) were in New York Heart Association class III or IV, 15 (46%) had unstable angina, and 7 (21%) were operated on because of evolving myocardial infarction. One or more previous myocardial infarctions were present in 18 patients (54%). Nineteen patients (58%) presented with neurologic symptoms, and 22 (67%) had severe bilateral carotid stenosis. Thirty (91%) had triple-vessel or left main coronary artery disease. Sequential reconstruction of the carotid artery followed by coronary artery bypass grafting was performed in all patients. In 4 cases, additional cardiac procedures were performed. Operative mortality (6%) was cardiac related. Perioperative morbidity included myocardial infarction in 1 patient (3%) and neurologic deficit in 6 (18%), with permanent functional impairment in 2 patients (6%). The stroke rate was higher in the bilateral than in the unilateral carotid stenosis group (22.7% vs 9.1%, p = 0.047). Previously completed stroke influenced the operative outcome (55.6% vs 4.2%, p = 0.003). Low ejection fraction (33.5% +/- 7.5% vs 52.8% +/- 3.5%, p = 0.03) and left main coronary artery disease (36% vs 5%, p = 0.03) also predicted postoperative neurologic complications. During a mean follow-up of 24.6 +/- 3.5 months, 3 patients died. The 5-year life-table survival rate was 85%. Eighty-nine percent of long-term survivors were free of cardiovascular disease symptoms. Our results show that the out come of simultaneous carotid endarterectomy/coronary artery bypass grafting in this high-risk population depends upon the preoperative absence or presence of completed stroke or bilateral carotid stenosis, upon the preoperative ejection fraction, and upon the extent of the left main coronary artery disease.

Effect of sodium nitroprusside on paraplegia during cross-clamping of the thoracic aorta.

Sodium nitroprusside (SNP) is usually used to control excessive proximal pressure after aortic cross-clamping. To assess the effect of SNP on circulatory dynamics, somatosensory evoked potentials, and neurologic outcome, 10 adult mongrel dogs that underwent 45 minutes of cross-clamping of the thoracic aorta were randomly assigned to receive either 50 mg/kg of SNP or no treatment for excessive proximal hypertension. There was a statistically significant difference noted between the SNP-treated animals and the control animals in terms of the proximal mean arterial pressures (112 +/- 13 versus 142.2 +/- 15 mm Hg, respectively; p < 0.05) and the mean distal arterial pressures (15 +/- 3 mm Hg versus 23 +/- 1 mm Hg; p = 0.04). However, the electrical activity of the spinal cord, as indicated by the somatosensory evoked potentials, returned significantly faster in the nontreated group than in the SNP-treated group (15 +/- 9 versus 44 +/- 13 minutes; p < 0.05). Control animals exhibited a significantly better neurologic outcome and no paraplegia 24 hours postoperatively. We conclude that the use of SNP to treat excessive proximal hypertension may be detrimental to the spinal cord during cross-clamping of the thoracic aorta, resulting in a decline in the ischemic tolerance.

[Unsolved problems of the surgical treatment of dissecting aneurysms of the ascending aorta (analysis of complications)]. / Nereshennye voprosy khirurgicheskogo lecheniia rasslaivaiushchikh anevrizm voskhodiashchei aorty (analiz oslozhnennii).

It is shown that various complications occurring after surgical treatment of dissecting aneurysms of the ascending aorta with or without aortic insufficiency depend mainly on the methods of correction applied and the etiology of the disease. As the result of the study the authors conclude that the Bentall-De Bono and Cabroe's operations are radical methods for surgical management of dissecting aneurysms of the ascending aorta irrespective of the etiology of the disease. Wide introduction of these operative methods into the clinical practice led to an essential decrease of hospital mortality and the frequency of complications in the immediate and late-term postoperative period.

[Surgical tactics in dissecting aneurysms of the ascending aorta]. / Khirurgicheskaia taktika pri rasslaivaiushchikh anevrizmakh voskhodiashchei aorty.

The aspects of surgical tactics in management of dissecting aneurysms of the ascending aorta are analysed in relation to the disease etiology, the anatomical pattern of the aortic root, presence of attending aortic insufficiency, and dissection extension. Based on the experience of 32 operations (March 1979--February 1988), it is concluded that the abnormal type must be the best criterion for choosing the surgical technique. In dissecting aneurysms due to aortic wall degeneration, Bentall-De Bono and Cabrol's modifications are preferable. In dissecting aneurysms of atherosclerotic origin, the boundary of the proximal extension of dissection should be taken into account. When the dissection extends into the aortic root, the operation using a valve-containing conduit with reimplantation of the ostia of the coronary arteries is feasible. If the aortic root is not involved, isolated prosthesis of the ascending aorta or separate prosthesis of the aortic valve and ascending aorta may be performed depending on the presence of aortic failure.

Surgical treatment of dissecting aneurysm of the ascending aorta: immediate and late results.

The authors describe experience gained with surgical treatment of dissecting aneurysm of the ascending aorta in the period from 1978 to 1987. 30 patients were operated on using the techniques proposed by Bentall, De Bono and Carbrol. All patients exhibited the presence of annulo-aortic ectasia. Hospital mortality in the past four years was 20%. On the basis of an analysis of immediate and late results the authors come to the conclusion that Bentall's, De Bono's and Cabrol's technique is the method of choice for surgical corrections of annulo-aortic ectasia and Marfan's syndrome.

[Long-term results of the surgical treatment of aneurysm of the ascending aorta in combination with aortic valve insufficiency]. / Otdalennye rezul'taty khirurgicheskogo lecheniia anevrizm voskhodiashchego otdela aorty s sochetanii s nedostatochnost'iu aortal'nogo klapana.

Four of 28 patients who were operated on died in late-term periods, four from advancing cardiac failure and one died 5 years after an operation from cardiac tamponade. In the group of four patients one underwent Cabrol's operation, three were operated on by the Bentall-De Bono method. The condition of 25 patients considerably improved and they were related to the II and I functional classes. The result was poor in three patients due to initial severity of the process in one, dilatation of the arch of the aorta in another, the presence of a fistula in the distal anastomosis in the third. One patient treated by Cabrol's operation and another who was operated on by the Bentall-De Bono method had pseudoaneurysms in the orifices of the coronary arteries. Despite some complications which occurred in the late postoperative periods, the Cabrol and Bentall-De Bono operations are the most radical means today for surgical treatment of aneurysms of the ascending aorta.

[Surgical treatment of aneurysm of the ascending aorta in Marfan syndrome]. / Khirurgicheskoe lechenie anevrizmy voskhodiashchei aorty pri sindrome Marfana.

An experience with 26 operations for aneurysms of the ascending aorta with a concomitant insufficiency of the aorta valve in Marfan syndrome is described. We started using operations after Bentall-De Bono in 1979 and operations after Cabrol in 1983 which were used in cases with low localization of openings of the coronary arteries in relation to the fibrous ring of the aorta valve, as well as in cases with the dissecting aorta wall, especially involving the area of the openings. These operations allowed the intrahospital lethality to be reduced: in the period of 1979-86 it made up 30% (6 patients died out of 20), in 1983-86 it was 15.4%, in 1986 it was 12.5%.

[Immediate results of the surgical treatment of aneurysms of the ascending aorta associated with aortic insufficiency]. / Neposredstvennye rezul'taty khirurgicheskogo lecheniia anevrizm voskhodiaschei aorty s soputstvuiushchei aortal'noi nedostatochnost'iu.

Experience with surgical treatment of ascending-artery aneurysms with concomitant aortic insufficiency is summed up. Forty-four patients were operated on, 30 of those having dissecting aneurysm of the ascending aorta. There were 6 operations where coronary arterial openings were isolated and stitched into a valve-containing conduit and 8 supracoronary resections with prosthetic aortic valve implantation. Hospital mortality rate was 78.6%. Thirty patients underwent Bentall-De Bono operation or Cabrol's operation. Hospital mortality was 26.6%. As surgical techniques and corrective methods improved, hospital mortality could be considerably reduced (to 7.7%).

[Detection of latent disorders of coronary circulation and heart rhythm in ischemic heart disease patients by using psychoemotional loading]. / Vyiavlenie skrytykh narushenii koronarnogo krovoobrashcheniia i ritma serdtsa u bol'nykh ishemicheskoi bolezn'iu serdtsa s primeneniem psikhoémotsional'noi nagruzki.

A relationship between the emergence of ventricular arrhythmias and other signs of myocardial ischemia was assessed in 96 coronary patients on the basis of comparative results of the physical and psychoemotional stressful tests, and the nitroglycerin and aspirin tests. Ventricular rhythm disorders may develop in the course of mental exercise in some coronary patients with low hemodynamic values as the only manifestation of myocardial ischemia. Large-scale use of the mental stressful test is advocated for cardiologic medical institutions.

[Effectiveness of lidocaine use in the initial period of acute myocardial infarct]. / Effektivnost' primeneniia lidokaina v nachal'nom periode ostrogo infarkta miokarda.

The efficiency of variant regimens of lidocaine management of acute myocardial infarction is compared. The need for continuous infusion of the drug throughout the first day of the attack at the rate of 1 mg per minute, and the reduction in the maximum heart rate as well as the incidence, rate and duration of the ventricular tachycardia runs are demonstrated.