No abstract

To assess whether the rheological properties of blood might be altered by exercise, we measured whole blood viscosity, plasma viscosity, and its components in healthy female subjects before, immediately after, and 1 h after maximal upright exercise using the Bruce graded exercise protocol. Forty-seven female subjects (15 sedentary, 14 who ran 5-15 miles/wk, and 18 who ran greater than 50 miles/wk), ages 18-43 yr, were evaluated. Whole blood viscosity, measured with a cone and plate viscometer, increased an average of 12.6% with exercise. The increase was greater than can be attributed to the observed 8.9% increase in hematocrit alone due to a coincident increase in plasma protein concentration. However, plasma viscosity did not rise to the degree expected, likely due to a disproportionate observed loss of fibrinogen from the protein pool. These changes were independent of conditioning level or aerobic capacity. In this cross-sectional study, there appears to be no adaptive adjustment in females to physical conditioning that results in changes in blood viscosity.

Carotid loop (CL) surgery involves the permanent externalization of a common carotid artery in a skin tube. The CL facilitates repeated access to the systemic arterial system for blood sampling and blood pressure measurement in laboratory sheep. It eliminates the need for arterial cut-downs and chronic indwelling catheters, reduces the risk of sepsis and infection, and adds flexibility to research protocols. The surgical procedure is aseptically performed under general anesthesia and involves isolation of the common carotid artery, creation of a bipedicled skin tube, and permanent envelopment of the artery in the skin tube. The primary complication is ischemic necrosis with sloughing of the middle of the loop and is usually due to failure to adhere to the critical length-to-width ratio (2.5:1). We have performed 150 CL procedures with an overall success rate of 94%. Nine CL ablations were required, due to necrosis with exposure of the artery (7/9) or stricture formation with loss of patency (2/9). Twenty-two CLs developed complications secondary to partial necrosis, but did not require ablation. Results indicate that the CL is a reliable method to ensure repeated access to the systemic arterial system in sheep. A modification of the standard CL procedure in which the artery is surrounded by a skin tunnel rather than enclosed in a skin loop was performed in 10 sheep. Preliminary results indicate significant reduction in the incidence of complications associated with the standard CL.

Benzocaine (BNZ) and lidocaine (LC) are commonly used topical (spray) anesthetics approved for use in humans. Benzocaine has structural similarities to methemoglobin (MHb)-forming drugs that are current candidates for cyanide prophylaxis, while LC has been reported to increase MHb in man. In this study, we compared MHb and sulfhemoglobin (SHb) production in three groups of Macaques (Chinese rhesus and Indian rhesus (Macaca mulatta) and pig-tailed macaques (Macaca nemestrina)) after exposure to BNZ and LC. Formation of SHb, unlike MHb, is not thought to be reversible and therefore is considered to be of greater toxic significance. Both MHb and SHb levels were measured periodically on a CO-Oximeter. All rhesus macaques (n = 8) were administered an intratracheal/intranasal) dose of 56 mg (low dose) or 280 mg (high dose) of BNZ or 40 mg of LC in a randomized cross-over design (all animals received all three treatments). Pig-tailed macaques (n = 6) were given an intranasal dose of 56 mg of BNZ and 40 mg of LC. As no differences in the peak MHb or time to peak (mean +/- SD) were observed among the three macaque subspecies, the data were pooled. Lidocaine did not cause MHb or SHb formation above baseline in any monkey. In contrast, all monkeys (n = 14) had a significant elevation in peak MHb formation after 56 mg of BNZ, which ranged from 4.0% to 19.4% with an average of 8.6 +/- 4.0% (mean +/- SD), with peak MHb levels reached at 30 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Butorphanol tartrate (0.5 mg/kg intravenously [IV]) was administered to six ewes (group 1), 10 minutes before administration of tiletamine-zolazepam (12 mg/kg IV). In six ewes (group 2), butorphanol tartrate and tiletamine-zolazepam were administered simultaneously. Time of administration of butorphanol did not alter hemodynamics or duration of anesthesia significantly. Anesthesia was adequate for 25 to 45 minutes (mean, 31 min) in group 1. The sheep in group 2 were anesthetized effectively for 25 to 50 minutes (mean, 39 min). Neither dosing regimen caused significant changes in right atrial pressure, heart rate, pulmonary vascular resistance, or pulmonary capillary wedge pressure. Mean arterial blood pressure (MABP) decreased an average of 18% from baseline values of 113 mm Hg to a minimum of 84 mm Hg at minute 60 in group 1, and from 111 mm Hg to 92 mm Hg at minute 75 in group 2. The decrease was significant only for group 1. Cardiac output (CO) was significantly decreased 24% from 6.6 L/min at minute 45 in group 1, and 32% from 6.3 L/min at minute 15 in group 2. Systemic vascular resistance (SVR) was increased significantly at minute 15, 11% in group 1 and 37% in group 2. Mild respiratory acidosis was measured by significant decreases in arterial pO2 and pH and a significant increase in pCO2 without significant changes in HCO3-. Results of this study show that (1) tiletamine-zolazepam and butorphanol tartrate produce adequate anesthesia for 25 to 50 minutes; (2) the cardiovascular and anesthetic effects of the dosing schedules were similar; and (3) tiletamine-zolazepam and butorphanol result in decreased CO and MABP with a concomitant increase in SVR, and mild respiratory acidosis.