Divers risk accelerated fatigue and core temperature rise during fully-immersed exercise in warmer water temperature extremes

Physiological responses to work in cold water have been well studied but little is known about the effects of exercise in warm water; an overlooked but critical issue for certain military, scientific, recreational, and professional diving operations. This investigation examined core temperature responses to fatiguing, fully-immersed exercise in extremely warm waters. Twenty-one male U.S. Navy divers (body mass, 87.3 ± 12.3 kg) were monitored during rest and fatiguing exercise while fully-immersed in four different water temperatures (Tw): 34.4, 35.8, 37.2, and 38.6°C (Tw_34.4, Tw_35.8, Tw_37.2, and Tw_38.6 respectively). Participants exercised on an underwater cycle ergometer until volitional fatigue or core temperature limits were reached. Core body temperature and heart rate were monitored continuously. Trial performance time decreased significantly as water temperature increased (Tw_34.4, 174 ± 12 min; Tw_35.8, 115 ± 13 min; Tw_37.2, 50 ± 13 min; Tw_38.6, 34 ± 14 min). Peak core body temperature during work was significantly lower in Tw_34.4 water (38.31 ± 0.49°C) than in warmer temperatures (Tw_35.8, 38.60 ± 0.55°C; Tw_37.2, 38.82 ± 0.76°C; Tw_38.6, 38.97 ± 0.65°C). Core body temperature rate of change increased significantly with warmer water temperature (Tw_34.4, 0.39 ± 0.28°C·h⁻¹; Tw_35.8, 0.80 ± 0.19°C·h⁻¹; Tw_37.2, 2.02 ± 0.31°C·h⁻¹; Tw_38.6, 3.54 ± 0.41°C·h⁻¹). Physically active divers risk severe hyperthermia in warmer waters. Increases in water temperature drastically increase the rate of core body temperature rise during work in warm water. New predictive models for core temperature based on workload and duration of warm water exposure are needed to ensure warm water diving safety.

Should coronary artery bypass be delayed following successful direct coronary artery streptokinase thrombolysis during evolving myocardial infarction?

The effect of deferring immediate coronary artery bypass was evaluated in two groups of similar patients having successful direct coronary artery thrombolysis with streptokinase in the treatment of evolving myocardial infarction. Within 6 hours of onset of myocardial infarction, 140 patients underwent immediate cardiac catheterization and infusion of intracoronary streptokinase up to 500,000 units. Of those patients having restoration of orthograde coronary blood flow coupled with immediate evidence of myocardial salvage, 31 patients (group I) had immediate coronary artery bypass and 34 patients (group II) had coronary artery bypass deferred. Group I had no hemorrhagic, hemodynamic, or new cardiac complications. There were no deaths, reinfarction, recurrence of angina, or loss of salvaged myocardium at restudy. In group II, 11 of 34 patients had early reinfarction (p less than 0.01 vs. group I), 16 of 34 patients had recurrent angina (p less than 0.01 vs. group I) and two deaths occurred from cardiac causes. Subsequent coronary bypass was needed in 16 patients. All restudied reinfarction patients lost restored myocardium. We concluded that immediate coronary artery bypass is safe after acute myocardial infarction and coronary artery thrombolysis with streptokinase, delay of coronary artery bypass leads to an unacceptable incidence of reinfarction and recurrent severe angina, and early coronary artery bypass is needed to ensure success of thrombolysis.

Revascularization of the extracranial vertebral artery at any level without cross-clamping

Hemodynamic insufficiency resulting from extracranial vertebral artery stenosis or occlusion is believed to be the major cause of vertebrobasilar transient ischemic attacks. The major difficulties in treating this disorder have been exposure of the vertebral artery distal to the stenosis and the risk of vertebral artery cross-clamping for vein grafting or carotid artery transposition. The authors describe a new technique for vertebral artery reconstruction at any level by the use of an intraluminal shunt, thus avoiding the necessity to cross-clamp the artery. This procedure was successfully performed at all three levels of the extracranial vertebral artery: C7-4, C3-1, and C-1 to the foramen magnum. The technique of exposure of the vertebral artery at these three levels and the method of vein grafting without cross-clamping are described. The initial results of the procedure are presented.

Subclavian to distal vertebral artery bypass. Case report

✓ A simple technique is described for extracranial vertebral artery vein bypass grafting, utilizing an internal shunt that avoids prohibitively dangerous vertebral artery cross-clamping. This procedure was carred out successfully in a patient with vertebrobasilar insufficiency.

Combined subclavian-external carotid and superficial temporal-middle cerebral artery bypass graft

A variation of a superficial temporal-middle cerebral artery bypass is presented that can serve as a surgical alternative to long vein subclavian-middle cerebral artery grafting in patients with common carotid artery occlusion and symptoms of ipsilateral ischemia. A vein graft from the subclavian to the external carotid artery at the carotid bifurcation is performed simultaneously with a standard superficial temporal-middle cerebral artery bypass. Advantages of this procedure over a long subclavian-middle cerebral artery vein graft are the technical simplicity associated with a standard superficial temporal-middle cerebral artery bypass, higher patency rates, and lower risk of graft leakage or torsion. Three patients have undergone this procedure, and all had patent bypasses one year after operation.

Therapeutic enigma of unilateral pulmonary artery coarctation in pulmonary hypertension

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