Impact of a hypotension treatment algorithm in dogs undergoing general anaesthesia for desexing surgery

To determine if the use of an algorithm for guiding treatment of hypotension during general anaesthesia was effective in limiting the severity or duration of hypotension. The algorithm-guided treatment included both fluid therapy and pharmacological interventions.

Retrospective before-and-after cohort study.

University teaching hospital.

Anaesthetised healthy dogs undergoing elective desexing surgery. The before period included 72 dogs and the after period included 81 dogs.

Anaesthetic records for the 2 years before and after the algorithm was introduced were searched. Inclusion criteria were cases that underwent surgery within the specified time periods. Data extracted included signalment, preanaesthetic tests, drug doses, anaesthetic duration, interventions for hypotension, mean arterial pressure (MAP), heart rate and temperature. Complications between the two time periods were compared.

There was a greater proportion of female dogs in the after period. All other signalment details, preanaesthetic findings, drug doses and anaesthetic duration were the same. Hypotension defined as MAP <60 mmHg occurred in 65% of before and 74% of after cases. Hypotension duration was 40 ± 25.2 and 23 ± 16.9 min (P = 0.0001), and lowest MAP was 46 ± 8.2 and 51 ± 5.8 mmHg (P = 0.007) before and after, respectively. Hypothermia was less severe in the after period (P = 0.033). Algorithm use was associated with more frequent atropine use and lower cumulative volume of intravenous fluid administered.

Introduction of the algorithm significantly reduced the severity and duration of hypotension and the severity of hypothermia. The algorithm could be used by veterinarians to improve outcomes for dogs undergoing elective surgery.