Search Results

You are looking at 1 - 3 of 3 items for

  • Author or Editor: Randall L. Tackett x
  • Refine by Access: All Content x
Clear All Modify Search

SUMMARY

Postadulticide pulmonary hypertension mechanisms and treatment with antihistamines and supplemental oxygen were studied in eight dogs with heartworm disease. To ensure severe postadulticide thromboembolism, additional heartworms (either 20 or 40 into 4 dogs each) were transplanted into naturally infected dogs before thiacetarsamide treatment. During pentobarbital anesthesia, 2 pulmonary hemodynamic studies were conducted on each dog with a sequence of baseline, hypoxia with FlO2 = 10%, hyperoxia with FlO2 = 100%, a second baseline, treatment with either diphenhydramine (D) or cimetidine (C), and another hypoxia.

All dogs were pulmonary hypertensive, with each dog having a mean pulmonary arterial pressure (PPA) > 20 mm of Hg. Mean PPA increased from baseline conditions (25.0 ± 4.5 SD for D and 24.3 ± 4.4 for C) to hypoxia (28.5 ± 4.7 for D and 28.4 ± 3.7 for C), and decreased during hyperoxia (16.9 ± 3.0 for D and 17.4 ± 3.0 for C), respectively. Neither antihistamine reduced PPA at normoxia. The degree of pulmonary hypertension when breathing room air increased even more during hypoxia, and this increase was not attenuated by either antihistamine. Histamine did not appear to mediate pulmonary hypertension during postadulticide thromboembolism, nor to modify the hypoxia-mediated pulmonary hypertension at this disease stage. Because baseline PO2 was low (66.6 ± 11.7 mm of Hg for D and 69.4 ± 14.2 for C) and because PPA decreased during administration of oxygen, the pulmonary hypertension was mostly hypoxia-induced. In addition to the arterial lesions, much of the pulmonary hypertensive mechanism was an active and reversible vasoconstriction in response to hypoxia caused by the secondary lung disease. Supplemental oxygen to dogs with pulmonary hypertension could reduce PPA and right ventricular afterload. This study supports the use of oxygen, but not antihistamine drugs, in the treatment of postadulticide heartworm disease in dogs that are hypoxic, with signs of congestive heart failure or dyspnea.

Free access
in American Journal of Veterinary Research

Abstract

Objective

To compare in vitro smooth muscle relaxation of palmar digital vessels from healthy horses with those from horses in the prodromal stage of experimentally (carbohydrate) induced laminitis.

Animals

16 adult horses.

Procedure

Segments of palmar digital vessels were obtained from 5 healthy horses and 6 horses given carbohydrate. Vascular rings from the palmar digital artery and vein were suspended in individual organ baths containing buffer solution and indomethacin; isometric tension was recorded, and contraction and relaxation were compared. Smooth muscle contraction in response to cumulative addition of phenylephrine was recorded in the absence and presence of 1 µM NG- nitro-L-arginine methyl ester (L-NAME). After wash out, vascular rings were preconstricted with phenylephrine (0.3 µM), and cumulative endothelium-dependent (acetylcholine-induced) and independent (nitroprusside-induced) smooth muscle relaxations were recorded in the absence or presence of L-NAME.

Results

Phenylephrine increased vascular smooth muscle tone in ring preparations of palmar digital arteries and veins. Addition of acetylcholine or nitroprusside induced relaxation of palmar digital artery and vein ring preparations. Use of L-NAME (1 µM) significantly reduced maximal relaxation induced by acetylcholine, but not by nitroprusside. Maximal relaxation induced by acetylcholine, but not by nitroprusside, was reduced in vascular rings prepared from carbohydrate-overloaded horses.

Conclusion and Clinical Relevance

Reduced endothelium-dependent relaxation of palmar digital vessels may have a role in the pathophysiology of acute laminitis after carbohydrate overload in horses. (Am J Vet Res 1999;60:233–239)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To identify clinical indicators that may help identify postoperative pain in cats after ovariohysterectomy.

Animals

Healthy, laboratory animal source cats.

Procedure

Clinical indicators of pain were identified, and relief from pain in response to butorphanol was studied in 5 groups of cats. 10 cats had 1 hour of general anesthesia only, followed by recovery without additional medication. 10 cats had general anesthesia and ovariohysterectomy, followed by recovery without additional medication. 10 cats had general anesthesia, ovariohysterectomy, and postoperative administration of 0.1 mg of butorphanol/kg of body weight. Another 10 cats had general anesthesia, ovariohysterectomy, and postoperative administration of 0.3 mg butorphanol/kg. 10 cats received 0.1 mg of butorphanol/kg, IM, only. Samples and recorded data were obtained before, during, and after the anesthesia period. Clinical variables measured included heart rate, blood pressure, respiratory rate, rectal temperature, PCV, and blood glucose concentration. Results were compared with changes in norepinephrine, epinephrine, and cortisol concentrations.

Results

Cats that did not receive analgesics had higher cortisol concentration than did cats without surgery and cats that received butorphanol after surgery. Systolic blood pressure measured by ultrasonic Doppler was found to be predictive of cortisol concentration, using a multiple linear regression model.

Conclusions

Cortisol concentration increased in response to surgical stress and pain, and this increase was diminished by use of butorphanol.

Clinical Relevance

Systolic blood pressure was the best clinical predictor of postoperative pain. (Am J Vet Res 1996;209:1674–1678)

Free access
in American Journal of Veterinary Research