The American journal of physiology
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Comparative Study
Arteriovenous oximeter for O2 content difference, O2 saturations, and hemoglobin content.
We combined two spectrophotometric oximeters to measure continuously and simultaneously arteriovenous O2 content difference (AVOD) as well as arterial and venous oxyhemoglobin saturations (SaO2, SvO2) and total hemoglobin concentration (Hb). AVOD of the flowing arterial and venous whole blood was determined by the method of Guyton et al. (J. Appl. ⋯ AVOD, SaO2, SvO2, and Hb were compared with the data of the arterial and venous blood sampled near the oximeter cuvettes and measured with an IL282 CO oximeter. In one dog experiment and one in vitro blood experiment, AVOD data of the same arterial and venous blood were compared by connecting the present oximeter in series with an A-VOX Systems oximeter developed by Shepherd and Burgar. The results showed that the new arteriovenous oximeter can continuously measure AVOD, SaO2, SvO2, and Hb over wide ranges with reasonable accuracy.
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Body temperature, plasma responses, and subjective ratings of thirst and hotness were studied in 5 older men (OM, 61-67 yr) and 6 younger men (YM, 21-29 yr) during 180-min thermal dehydration and subsequent 60-min rehydration (45 degrees C, 25% relative humidity). Rectal temperature (Tre) increased more rapidly and to a greater magnitude in OM, while average total body sweat rates and chest sweat rates were not significantly different. During dehydration, both OM and YM lost similar body weight (1.52 +/- 0.11 vs. 1.55 +/- 0.22%, mean +/- SE). ⋯ Within 30 min of drinking, YM had restored Pv and Posm, whereas OM showed slower responses, restoring Posm after 60 min and Pv only after a subsequent 30 min at 25 degrees C. Despite a higher Tre and greater change in Pv and Posm, OM rated themselves less thirsty and not significantly hotter than YM. These findings suggest that aging results in decreased ability to maintain Tre during heat stress and that the mechanisms comprise a combination of alterations in body fluid distribution and perception.
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The effect of verapamil (VER) resuscitation from shock on cardiac function, regional blood flow, as well as skeletal muscle transmembrane potential (TMP) and electrolyte redistribution were studied. Two hours of hypotensive shock in the dog significantly impaired cardiac function and coronary perfusion; TMP fell from 89.9 +/- 0.9 to 75.1 +/- 1.2 mV. Skeletal muscle (SMS) extracellular water decreased 40 +/- 2%, whereas intracellular sodium and chloride increased and intracellular potassium fell. ⋯ SMS calcium was lower in VER dogs (148 +/- 4 micrograms/g) compared with dogs treated with fluid alone (322 +/- 24 micrograms/g, P = 0.01). Myocardial calcium fell in all dogs after volume replacement regardless of calcium-channel blockade (VER: 148 +/- 8, Ringer: 165 +/- 17 micrograms/g; P greater than 0.05). Our data indicate a potential role for calcium-entry blockade in the treatment of hemorrhagic shock.