Comparison of two doses of lidocaine constant rate infusion on cardiopulmonary function and recovery in isoflurane-anesthetized horses.

OBJECTIVE

To compare cardiopulmonary variables and recovery scores in isoflurane-anesthetized horses undergoing arthroscopy using two different intravenous (IV) lidocaine constant rate infusions (CRIs; 50 or 100 μg kg-1 minute-1) under intermittent positive pressure ventilation (IPPV) or spontaneous ventilation (SV).

STUDY

DESIGN

Prospective, randomized, clinical study.

ANIMALS: A group of 30 client-owned horses, 8-156 months old (range), with body masses of 280-550 kg.

METHODS

Anesthesia protocol consisted of xylazine, ketamine and diazepam, and maintenance with isoflurane and a CRI of dexmedetomidine. All groups were given an IV bolus of lidocaine (2 mg kg-1) 15 minutes after induction and were randomized to CRI 50 or 100 μg kg-1 minute-1 under IPPV or SV (groups IPPV50, IPPV100, SV50 and SV100). Lidocaine was stopped before recovery. Cardiopulmonary variables, plasma lidocaine concentrations during anesthesia and recovery, and a numerical and descriptive score for quality of recovery were compared between groups. Data were analyzed using one- or two-way ANOVA or Kruskal-Wallis tests when appropriate.

RESULTS

SV groups had significantly higher arterial and end-tidal CO2 tensions and lower pH (p < 0.0001). Mean arterial blood pressure differed by ≤ 7 mmHg between groups, was significantly higher in SV100 (p < 0.0001) and IPPV100 (p = 0.0001) than SV50, and was higher in SV100 than IPPV50 (p = 0.044). Intraoperative lidocaine concentrations were significantly higher (p = 0.0005-0.049) with the higher CRI, and in all groups decreased significantly by 20 minutes in recovery (p < 0.0001-0.002). All groups had similar numerical (p = 0.529) and similar descriptive recovery scores [p = 0.413; IPPV50: 2 (1,2), IPPV100: 1 (1,3), SV50: 2 (1,2), SV100: 2 (2,3), median (range)], and of good quality.

CONCLUSIONS AND CLINICAL RELEVANCE: Low and high CRI lidocaine resulted in similar cardiopulmonary function and quality of recovery in healthy horses undergoing arthroscopy. SV resulted in hypercapnia.