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Respiratory alkalosis and primary hypocapnia in Labrador Retrievers participating in field trials in high–ambient-temperature conditions

Janet E. Steiss DVM, PhD1 and James C. Wright DVM, PhD2
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  • 1 Department of Anatomy, Physiology, and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849.
  • | 2 Department of Pathobiology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849.

Abstract

Objective—To determine whether Labrador Retrievers participating in field trials develop respiratory alkalosis and hypocapnia primarily in conditions of high ambient temperatures.

Animals—16 Labrador Retrievers.

Procedures—At each of 5 field trials, 5 to 10 dogs were monitored during a test (retrieval of birds over a variable distance on land [1,076 to 2,200 m]; 36 assessments); ambient temperatures ranged from 2.2° to 29.4°C. For each dog, rectal temperature was measured and a venous blood sample was collected in a heparinized syringe within 5 minutes of test completion. Blood samples were analyzed on site for Hct; pH; sodium, potassium, ionized calcium, glucose, lactate, bicarbonate, and total CO2 concentrations; and values of PvO2 and PvCO2. Scatterplots of each variable versus ambient temperature were reviewed. Regression analysis was used to evaluate the effect of ambient temperature (≤ 21°C and > 21°C) on each variable.

Results—Compared with findings at ambient temperatures ≤ 21°C, venous blood pH was increased (mean, 7.521 vs 7.349) and PvCO2 was decreased (mean, 17.8 vs 29.3 mm Hg) at temperatures > 21°C; rectal temperature did not differ. Two dogs developed signs of heat stress in 1 test at an ambient temperature of 29°C; their rectal temperatures were higher and PvCO2 values were lower than findings in other dogs.

Conclusions and Clinical Relevance—When running distances frequently encountered at field trials, healthy Labrador Retrievers developed hyperthermia regardless of ambient temperature. Dogs developed respiratory alkalosis and hypocapnia at ambient temperatures > 21°C.

Abstract

Objective—To determine whether Labrador Retrievers participating in field trials develop respiratory alkalosis and hypocapnia primarily in conditions of high ambient temperatures.

Animals—16 Labrador Retrievers.

Procedures—At each of 5 field trials, 5 to 10 dogs were monitored during a test (retrieval of birds over a variable distance on land [1,076 to 2,200 m]; 36 assessments); ambient temperatures ranged from 2.2° to 29.4°C. For each dog, rectal temperature was measured and a venous blood sample was collected in a heparinized syringe within 5 minutes of test completion. Blood samples were analyzed on site for Hct; pH; sodium, potassium, ionized calcium, glucose, lactate, bicarbonate, and total CO2 concentrations; and values of PvO2 and PvCO2. Scatterplots of each variable versus ambient temperature were reviewed. Regression analysis was used to evaluate the effect of ambient temperature (≤ 21°C and > 21°C) on each variable.

Results—Compared with findings at ambient temperatures ≤ 21°C, venous blood pH was increased (mean, 7.521 vs 7.349) and PvCO2 was decreased (mean, 17.8 vs 29.3 mm Hg) at temperatures > 21°C; rectal temperature did not differ. Two dogs developed signs of heat stress in 1 test at an ambient temperature of 29°C; their rectal temperatures were higher and PvCO2 values were lower than findings in other dogs.

Conclusions and Clinical Relevance—When running distances frequently encountered at field trials, healthy Labrador Retrievers developed hyperthermia regardless of ambient temperature. Dogs developed respiratory alkalosis and hypocapnia at ambient temperatures > 21°C.

Contributor Notes

Supported by grants from the S. D. Bechtel Jr. Foundation, the R. K. Mellon Family Foundation, and Mr. W. E. Bowen.

The authors thank Chris Ledford, Wild Wind Kennels, Buckhead, Ga; Dr. Don Sorjonen, Professor Emeritus, Auburn University, Auburn, Ala; Mr. and Mrs. Joseph Cooper III, Atlanta Retriever Club, Waverly, Ala; and Paula Reissdorf, Ebony Gilbreath, and Judith Hones, Tuskegee University, Tuskegee, Ala, for technical assistance.

Address correspondence to Dr. Steiss.