Urinary catecholamine excretion on induction to high altitude (3,658 m) by air and road

In a preliminary pilot study we had reported a significant difference in urinary catecholamine excretion between symptomatic and asymptomatic individuals inducted to high altitude by air. The present study covers slower induction by road; 25 lowlanders ascended from 1,800 to 3,658 m in 50 h and 33 similar subjects covered the journey in 6 h. They were studied according to the protocal used in the initial study. None of the 58 subjects inducted by road developed symptoms of high-altitude illness. Their urinary catecholamine excretion remained normal during the 10 days' stay at high altitude. These findings lend support to our earlier contention that there might be a relationship between increased sympathoadrenal activity and high-altitude illnesses.

Effect of high-altitude exposure for 10 days on stroke volume and cardiac output

Resting stroke volume and cardiac output of 50 normal healthy sea-level residents (group A) were estimated by the noninvasive technique of electrical impedance plethysmography. They were then airlifted to an altitude of 3,658 m and serial estimations carried out at 0-4 h and 5-8 h and on the 2nd, 3rd, 4th, 5th, and 10th days. The subjects were brought back to sea level and studied for up to 5 days. Thirty permanent residents of high altitude (group B) and sixteen lowlanders temporarily resident at high altitude (group C) were also subjected to similar studies. It was found that resting stroke volume and cardiac output of group A started falling immediately on arrival at high altitude, reached the minimum on the 3rd day and tended to improved on the 4th and 5th day, but showed a secondary fall on the 10th day. The reduction in stroke volume in this group was not fully compensated by tachycardia. On return to sea level the cardiac output normalized immediately, the stroke volume on the 2nd day. At sea level goup A had values similar to group B and at high altitude to group C.

Changes in transthoracic electrical impedance at high altitude

Mean transthoracic electrical impedance (impedance) which is inversely related to intrathoracic extravascular fluid volume was measured in 121 normal healthy volunteers at sea-level and at 3658 metres altitude. Fifty (group A) reached the high altitude location after an hour's journey in a pressurised aircraft. Twenty-five (group D) underwent slow road ascent including acclimatisation en route. Thirty permanent residents (group B) and 16 temporary residents at high altitude (group C) were also studied. Serial studies in the 30 subjects of group A who developed symptoms of high altidue sickness showed a significant decrease of impedance up to the fourth day of exposure to high altitude which later returned to normal. The 4 volunteers who developed severe symptoms showed the largest drop in impedance. A case of acute pulmonary oedema developing at 4300 metres showed an impedance value of 24-1 ohms on admission. After effective treatment the impedance increased by 11-9 to 36-0 ohms. Twenty asymptomatic subjects of group A and 25 of group D showed a small average increase in impedance values at high altitude. These obstructions suggest that measurement of transthoracic electrical impedance may be a valuable means of detecting incipient high altitude pulmonary oedema.

Urinary catecholamine excretion on acute induction to high altitide (3,658 m)

Fifty healthy male volunteers, 21-34 yr of age, normally resident at altitudes less than 1,000 m, were airlifted to 3,658 m. Urinary excretion of catecholamines was measured at sea level (198 m) and on the 1st, 2nd, 4th, and 10th day of a stay at high altitude. The symptoms observed on exposure to high altitude were assigned arbitrary scores. The volunteers could, on this basis, be divided into "symptomatic" and "asymptomatic" groups. The two groups showed a markedly different pattern of urinary catecholamines excretion on exposure to high altitude and on return to sea level. Significant increase in the catecholamine excretion was observed in the symptomatic group only. A possible role for enhanced sympathoadrenal activity in the etiopathogenesis of high-altitude illnesses is postulated.

Verapamil in ischaemic heart disease--quantitative assessment by serial multistage treadmill exercise

The efficacy of verapamil in a dose of 120 mg thrice daily was assessed by an objective protocol. Twenty-five patients with ischaemic heart disease were subjected to serial, measured multistage treadmill exercise without any drugs, and after propranolol 40 mg t.d.s. for 3 days to assess the stress response to beta-blockade. The tests were repeated after 2, 4 and 8 weeks of verapamil. The assessment was based on computerized ST segment changes, the anginal threshold and other objective parameters. Verapamil rendered eight out of thirteen symptomatic patients pain free and significantly increased the anginal threshold in all others. The ischaemic response as assessed by the ST segment changes on exercise showed a marked improvement in the symptomatic as well as the asymptomatic groups. No major side effects were encountered throughout the study. It was concluded that verapamil in a dose of 360 mg/day is an effective antianginal agent free from significant side effects.

Excitation-contraction coupling in heart. XIX. Effect of hypoxia on calcium transport by subcellular particles in the isolated perfused rat heart

To examine the role of changes in calcium transport by subcellular particles in the pathogenesis of contractile failure due to oxygen lack, both mitochondrial and microsomal fractions were obtained from the isolated hypoxic rat hearts and their calcium binding and uptake abilities were determined by the Millipore filtration technique. The contractile force decreased by about 40, 60 and 70% of the control within 5, 10 and 30 min respectively, of perfusing the heart with hypoxic medium containing glucose. In hearts perfused for 10 min with hypoxic medium containing glucose, calcium binding and uptake by the microsomal fraction decreased significantly. However, mitochondrial calcium binding, but not uptake, decreased significantly on perfusing the hearts with hypoxic medium containing glucose for 20 to 30 min when the microsomal calcium transport was markedly depressed. Reduction in contractile force, calcium binding and uptake by the microsomal fraction as well as calcium binding by mitochondria of hearts made hypoxic for 30 min recovered towards normal upon reperfusion with control medium for 15 min. On the other hand, omitting glucose from the hypoxic medium significantly decreased calcium binding by mitochondrial and microsomal fractions within 10 min of perfusion in comparison to the control and accelerated the effects of hypoxia upon contractile force and microsomal calcium uptake. In contrast to the hypoxic hearts, the mitochondrial calcium uptake decreased significantly and the magnitude of depression in the microsomal calcium binding was appreciably greater in hearts made to fail to a comparable degree upon perfusion with substrate-free medium. The observed defects in calcium transporting properties of microsomal and mitochondrial membranes appear secondary to the contactile failure in hypoxic hearts.

A kinetic study of the chlorination of ketones by chloramine-T: Novel concentration dependences on the chlorinating agent and the ketones

The chlorination of acetone in aqueous acidic medium in the presence of acetic acid and dimethylformamide was subjected to kinetic study. Although the kinetics follows the traditional mechanism at high concentrations of chloramine-T (cat) and in aqueous acetic acid in the presence of sodium acetate, a term in the rate law independent of ketone concentration is reported for the first time in strongly acidic medium at low concentrations of chloramine-T. Generation of the chlorinating species is considered as the rate-determining step (Scheme 1). The mechanistic changes which occur on addition of chloride and on changing the structure of the ketone are reported. The effect of acetate on the rate in aqueous acetic acid medium is rationalized by invoking a prior equilibrium formation of enolate followed by a rate-controlling chlorination by chlorinium acetate. The retardation in rate and the consequent changes in mechanism in the case of p-bromo- and p-nitroacetophenone are accounted for by invoking a complex between the enol and the positive chlorine species similar to that in the mechanism for the chlorination of phenols.

Changes in transthoracic electrical impedance during submaximal treadmill exercise in patients with ischemic heart disease--A preliminary report

Twenty normal subjects and 32 patients with ischemic heart disease (IHD) were subjected to submaximal treadmill exercise. The mean transthoracic electrical impedance (TEI) was measured with a tetrapolar lead system and the changes were correlated to the extent of ST depression observed on an on-line digital computer. Six subjects of pre-excitation syndrome with "false" ST depression were also studied. The normal subjects did not show a significant change of TEI during exercise. The patients with IHD showed a steady and significant decrease in TEI, correlating with the extent of ST depression. Recovery was slow after the cessation of exercise. The subjects with false ST changes showed no decrease of TEI. The changes were more profound in subjects who developed anginal pain during the test. These findings are attributed to an increase in the thoracic blood volume and pulmonary extravascular water due to transient left ventricular dysfunction in angina.

Effect of submaximal exercise on fibrinolytic activity in ischaemic heart disease

Fibrinolytic activity and platelet adhesiveness are normal in cases of angina pectoris and healed myocardial infarction, whereas fibrinolytic activity is diminished in acute myocardial infarction. Exercise increases fibrinolytic activity in normal people but the effect on it of submaximal exercise in patients with ischaemic heart disease is not known. Resting platelet adhesiveness and fibrinolytic activity were determined in 20 patients suffering from ischaemic heart disease and eight healthy controls. Both groups were then subjected to submaximal exercise on a motor-driven treadmill. The ST segment of the electrocardiogram and the heart rate were monitored during exercise by an on-line digital computer. Fibrinolytic activity determinations were repeated immediately after exercise. There was a significant increase in fibrinolytic response in both groups but it was significantly less in the ischaemic groups (36-2%) compared with the controls (55-9%) (P less than 0-01). The ST segment depression was 2-3 mm in the ischaemic group and 0-52 mm in controls--also a significant difference (P less than 0-01). There was no correlation, however, between the ST change and the fibrinolytic response. A diminished response in the ischaemic group may favour their predisposition to thrombotic episodes.

Effects of high altitude hypoxia on left ventricular systolic time intervals in man

Effects of high altitude hypoxia on systolic time intervals were examined in 34 healthy men: 20 sea level residents studied at rest and at the end of 3 minutes steady isometric (handgrip) exercise at sea level and then serially for the first 5 days and on the tenth day, at an altitude of 3658 m, and I4 permanent residents at high altitude studied at high altitude. In the sea level residents there was a significant increase in the pre-ejection period (PEP), abbreviation of the left ventricular ejection time (LVET), both corrected for heart rate, and prolongation of the PEP/LVET ratio at high altitude. The maximum changes were seen on days 2 and 3; these parameters tended to approach sea level control values by the tenth day. The systolic time interval values of high altitude residents were similar to the control values of the sea level residents obtained at sea level but significantly different from the changes in the sea level values seen in the first 4 days at high altitude. It thus appears that while the high altitude residents do not show any left ventricular dysfunction as determined by systolic time intervals, healthy sea level residents when exposed to high altitude hypoxia show a significant depression of the left ventricular function for at least the first 4 days. This might be a contributing factor in the genesis of high altitude pulmonary oedema.

Transthoracic electrical impedance in cases of high-altitude hypoxia

Changes in transthoracic electrical impedance (T.E.I.) due to high-altitude hypoxia (3,658 m) have been measured in 20 young, healthy Indian soldiers. They were first studied at sea level (198 m) and then rapidly transported by air to 3,658 m, where they were studied daily from day 1 to day 5 and then on days 8 and 10. The mean (+/-S.D.) T.E.I. at sea level (34.6+/-0.6Omega) fell sharply to 29.6+/-0.8Omega, 30.3+/-0.9Omega, and 30.5+/-1.1Omega on days 1, 2, and 3 (P <0.001) and levelled off at 31.5+/-0.7Omega on day 10, which was comparable to the mean value obtained in 13 persons permanently resident at high altitude (32.2+/-0.7Omega). Five sea-level residents who had acute mountain sickness (A.M.S.) or high-altitude pulmonary oedema (H.A.P.O.) had a still lower mean value (22.5+/-1.1Omega). One normal healthy subject who at sea level had a T.E.I. of 34.7Omega developed H.A.P.O. when the T.E.I. fell to 21.1Omega. Ninety minutes after the administration of 80 mg of intravenous frusemide the value increased to 35.5Omega. In another subject with A.M.S. who received 40 mg of frusemide intravenously the T.E.I. rose from 21.9 to 33.2Omega.Since the study was non-invasive the changes in impedance could not be correlated objectively with alterations in either pulmonary blood volume or pulmonary extravascular water space. In the subject, however, with x-ray evidence of H.A.P.O. and a low T.E.I. intravenous frusemide produced a marked rise in T.E.I. together with clearing of the chest x-ray picture within 24 hours, indicating an inverse relationship between impedance and thoracic fluid volume. It is suggested that with further objective verification in man the measurement of T.E.I. may be a potentially promising technique for the early detection of increased pulmonary fluid volume.