Clinical physiology (Oxford, England)
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Sixteen subjects were studied with regard to lung tissue changes during general anaesthesia. The transverse area and the structure of the lung tissue were studied by computerized tomography. No abnormalities were noted in the lung tissue before anaesthesia, but within five minutes after induction, all subjects had developed crest-shaped dependent changes of an increased density in both lungs. ⋯ The size of the densities could not be correlated to the age of the subjects, or time of the anaesthesia, and they were not affected by the inspiratory oxygen fraction. They could be rotated by turning the patient, and the application of a positive end-expiratory pressure eliminated or reduced the densities. It is suggested that the densities are atelectases, which develop by compression of lung tissue, and not by gas resorption.
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Comparative Study
In vitro analysis of thermal transport in coronary sinus thermodilution catheters.
The continuous thermodilution technique for measuring blood flow in the range 50-300 ml/min was evaluated in vitro. Experiments indicated that thermotransport within the catheter from the indicator line to the mixing thermistor exists. ⋯ Flows derived with the standard Ganz formula were significantly lower than timed volumetric flows, whereas flows obtained with the modified formula agreed with volumetric flow. The coefficient of variation for four consecutive measurements was 3.4%.
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Comparative Study
Cardiovascular response to spinal anaesthesia in elderly men: effects of head-up tilt and dihydroergotamine administration.
In nine elderly (mean age 60, rang 42-74 years) cardiovascular pressures and cardiac output have been measured by catheterization of the pulmonary and brachial artery during spinal anaesthesia without and with dihydroergotamine (DHE) and during an added slight head-up (10-15 degrees). Spinal anaesthesia lowered arterial pressure and also stroke volume. After DHE arterial pressures as well as stroke volume were normalized. ⋯ It is concluded that in elderly men, unlike the young men previously studied, spinal anaesthesia decreases arterial blood pressures by a combination of reduced peripheral resistance and decreased stroke volume. The decreases in stroke volume and cardiac output were most pronounced in those patients with a reduced blood volume. DHE also prevents arterial pressure fall with head-up tilt during spinal anaesthesia.