Clinical evaluation of ketamine and lidocaine intravenous infusions to reduce isoflurane requirements in horses under general anaesthesia.
OBJECTIVE
To compare isoflurane alone or in combination with systemic ketamine and lidocaine for general anaesthesia in horses.


METHODS
Prospective, randomized, blinded clinical trial.


METHODS
Forty horses (ASA I-III) undergoing elective surgery.


METHODS
Horses were assigned to receive isoflurane anaesthesia alone (ISO) or with ketamine and lidocaine (LKI). After receiving romifidine, diazepam, and ketamine, the isoflurane end-tidal concentration was set at 1.3% and subsequently adjusted by the anaesthetist (unaware of treatments) to maintain a light plane of surgical anaesthesia. Animals in the LKI group received lidocaine (1.5 mg kg(-1) over 10 minutes, followed by 40 microg kg(-1) minute(-1)) and ketamine (60 microg kg(-1) minute(-1)), both reduced to 65% of the initial dose after 50 minutes, and stopped 15 minutes before the end of anaesthesia. Standard clinical cardiovascular and respiratory parameters were monitored. Recovery quality was scored from one (very good) to five (very poor). Differences between ISO and LKI groups were analysed with a two-sample t-test for parametric data or a Fischer's exact test for proportions (p < 0.05 for significance). Results are mean +/- SD.


RESULTS
Heart rate was lower (p = 0.001) for LKI (29 +/- 4) than for ISO (34 +/- 6). End-tidal concentrations of isoflurane (ISO: 1.57% +/- 0.22; LKI: 0.97% +/- 0.33), the number of horses requiring thiopental (ISO: 10; LKI: 2) or dobutamine (ISO:8; LKI:3), and dobutamine infusion rates (ISO:0.26 +/- 0.09; LKI:0.18 +/- 0.06 microg kg(-1) minute(-1)) were significantly lower in LKI compared to the ISO group (p < 0.001). No other significant differences were found, including recovery scores.


CONCLUSIONS
These results support the use of lidocaine and ketamine to improve anaesthetic and cardiovascular stability during isoflurane anaesthesia lasting up to 2 hours in mechanically ventilated horses, with comparable quality of recovery.
Enderle
Alke K
AK
Wahlstedt Private Equine Veterinary Clinic, Wahlstedt, Germany.
Levionnois
Olivier L
OL
Kuhn
Matthias
M
Schatzmann
Urs
U
D000762:Anesthesia Recovery Period; D000768:Anesthesia, General / Q000662:veterinary*; D000778:Anesthetics, Dissociative; D018685:Anesthetics, Inhalation / Q000008:administration & dosage* / Q000493:pharmacokinetics; D000779:Anesthetics, Local / Q000008:administration & dosage* / Q000494:pharmacology; D000818:Animals; D005260:Female; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006736:Horses / Q000502:physiology*; D007262:Infusions, Intravenous / Q000662:veterinary; D007530:Isoflurane / Q000008:administration & dosage* / Q000493:pharmacokinetics; D007649:Ketamine / Q000008:administration & dosage / Q000494:pharmacology; D008012:Lidocaine / Q000008:administration & dosage / Q000494:pharmacology; D008297:Male; D011446:Prospective Studies; D011897:Random Allocation
D000778:Anesthetics, Dissociative; D018685:Anesthetics, Inhalation; D000779:Anesthetics, Local; D007649:Ketamine; D008012:Lidocaine; D007530:Isoflurane