Oxygenation and plasma endothelin-1 concentrations in healthy horses recovering from isoflurane anaesthesia administered with or without pulse-delivered inhaled nitric oxide.
OBJECTIVE
To assess oxygenation, ventilation-perfusion (V/Q) matching and plasma endothelin (ET-1) concentrations in healthy horses recovering from isoflurane anaesthesia administered with or without pulse-delivered inhaled nitric oxide (iNO).


METHODS
Prospective experimental trial.


METHODS
Healthy adult Standardbred horses.


METHODS
Horses were anaesthetized with isoflurane in oxygen and placed in lateral recumbency. Six control (C group) horses were anaesthetized without iNO delivery and six horses received pulse-delivered iNO (NO group). After 2.5 hours of anaesthesia isoflurane and iNO were abruptly discontinued, inhaled oxygen was reduced from 100% to approximately 30%, and the horses were moved to the recovery stall. At intervals during a 30-minute period following the discontinuation of anaesthesia, arterial and mixed venous blood gas values, shunt fraction (Qs/Qt), plasma ET-1 concentration, pulse rate and respiratory rate were measured or calculated. Repeated measures anova and a Bonferroni post hoc test was used to analyze data with significance set at p < 0.05.


RESULTS
At all time points in the recovery period, NO horses maintained better arterial oxygenation (oxygen partial pressure: NO 13.2 ± 2.7-11.1 ± 2.7 versus C 6.7 ± 1.1-7.1 ± 1.1 kPa) and better V/Q matching (Qs/Qt NO 0.23 ± 0.05-0.14 ± 0.06 versus C 0.48 ± 0.03-0.32 ± 0.08%) than C horses. Mixed venous oxygenation was higher in NO for 25 minutes following the discontinuation of anaesthesia (NO 6.3 ± 0.2-4.5 ± 0.07 versus C 4.7 ± 0.6-3.7 ± 0.3 kPa). In both groups of horses arterial oxygenation remained fairly stable; venous oxygenation declined over this time period in the NO group but still remained higher than venous oxygen in the C group. ET-1 concentrations were higher at most time points in C than NO. Changes in other parameters were either minor or absent.


CONCLUSIONS
Delivery of iNO to healthy horses during anaesthesia results in better arterial and venous oxygenation and V/Q matching (as determined by lower Qs/Qt) and lower ET-1 concentrations throughout a 30-minute anaesthetic recovery period.
Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman, WA, USADepartment of Animal Environment and Health, Faculty of Veterinary Medicine and Animal Husbandry, Swedish University of Agricultural Sciences, Skara, SwedenDepartment of Clinical Sciences, Faculty of Veterinary Medicine and Animal Husbandry, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Tamara
T
Grubb
Anna
A
Edner
Jan Hm
JH
Frendin
Pia
P
Funkquist
Anneli
A
Rydén
Görel
G
Nyman
D000769:Anesthesia, Inhalation / Q000379:methods / Q000662:veterinary*; D018685:Anesthetics, Inhalation; D000818:Animals; D001784:Blood Gas Analysis / Q000662:veterinary; D019332:Endothelin-1 / Q000097:blood*; D005260:Female; D006736:Horses / Q000097:blood* / Q000601:surgery; D007530:Isoflurane; D008297:Male; D009569:Nitric Oxide / Q000008:administration & dosage; D010100:Oxygen / Q000097:blood*
D018685:Anesthetics, Inhalation; D019332:Endothelin-1; D009569:Nitric Oxide; D007530:Isoflurane; D010100:Oxygen