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Arterial blood P o 2 and P co 2 in horses during early halothane — oxygen anaesthesia
Author(s) -
GRANDY JACQUELINE L.,
STEFFEY E. P.,
MILLER M.
Publication year - 1987
Publication title -
equine veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.82
H-Index - 87
eISSN - 2042-3306
pISSN - 0425-1644
DOI - 10.1111/j.2042-3306.1987.tb01419.x
Subject(s) - halothane , anesthesia , pco2 , arterial blood , medicine , arterial oxygen tension , respiratory acidosis , horse , general anaesthesia , blood pressure , oxygen , acidosis , chemistry , lung , paleontology , organic chemistry , biology
Summary Arterial blood was collected from 25 clinically normal horses immediately before and serially throughout the first hour of halothane oxygen anaesthesia. Blood was analysed for oxygen and carbon dioxide partial pressure ( P ao 2 , P aco 2 ). Measurements of inspired oxygen concentration during anaesthesia permitted direct correlation with blood gases. Horses were divided arbitrarily into two groups based on their age: two to seven years, n = 15; over seven years, n = 10. Average (±sd) P ao 2 and P aco 2 was 14.1 ± 1.5 kPa (106 ± 11 mmHg) and 5.9 ± 0.6 kPa (44.4 ± 4.4 mmHg) respectively in conscious, young horses and 14.0 ± 0.7 and 5.8 ± 0.5 kPa (105 ± 5 and 43.3 ± 3.8 mmHg) respectively in conscious older horses. Arterial oxygen tension decreased to 9.3 ± 1.0 and 8.5 ± 1.4 kPa (69.6 ± 7.8 and 63.7 ± 10.4 mmHg) in young and older air breathing horses respectively immediately following intravenous anaesthetic induction, recumbency and orotracheal intubation. At this time, P aco 2 was 6.5 ± 0.5 and 6.0 ± 0.7 kPa (48.7 ± 3.5 and 45.1 ± 4.9 mmHg) respectively. By 30 mins after the start of halothane in oxygen (6 litres/min) anaesthesia P ao 2 increased to a maximum in both study groups. Arterial P co 2 increased steadily during anaesthesia and 60 mins after induction P aco 2 was 10.5 ± 2.4 kPa (78.5 ± 17.8 mmHg) in the younger horses and 9.2 ± 1.6 kPa (68.8 ± 11.8 mmHg) in the older horses. During inhalation anaesthesia P ao 2 tended to be greater at comparable time periods in the younger horses despite a slightly greater degree of hypoventilation.