Use of lithium dilution and pulse contour analysis cardiac output determination in anaesthetized horses: a clinical evaluation.
OBJECTIVE
To assess the suitability of a human algorithm for calculation of continuous cardiac output from the arterial pulse waveform, in anaesthetized horses.


METHODS
Prospective clinical study.


METHODS
Twenty-four clinical cases undergoing anaesthesia for various conditions.


METHODS
Cardiac output (Qt), measured by lithium dilution (QtLiDCO), was compared with a preceding, calibrated Qt measured from the pulse waveform (QtPulse). These comparisons were repeated every 20-30 minutes. Positive inotropes or vasopressors were administered when clinically indicated. Cardiac indices from 30.7 to 114.9 mL kg(-1) minute(-1) were recorded. Unusually shaped QtLiDCO curves were rejected and the measurement was repeated immediately.


RESULTS
Eighty-nine comparisons were made between QtLiDCO and QtPulse. The bias between the mean (+/-SD) of the two methods (QtLiDCO - QtPulse) was -0.07 L minute(-1)(+/-3.08) (0.24 +/- 6.48 mL kg(-1) minute(-1)). The limits of agreement were -12.72 and 13.2 mL kg(-1) minute(-1) (Bland & Altman 1986; Mantha et al. 2000). Linear regression analysis demonstrated a correlation coefficient (r2) of 0.89. Cardiac output in individual patients varied from 49.1 to 183% of the initial measurement at the time of calibration. Linear regression of log-transformed Qt variation for each method found a mean difference of 9% with limits of agreement of -4.1 to 22.1%.


CONCLUSIONS
This method of pulse contour analysis is a relatively noninvasive and reliable way of monitoring continuous Qt in the horse under anaesthesia. The ability to easily monitor Qt might decrease morbidity and mortality in the anaesthetized horse.
Hallowell
Gayle D
GD
Equine Referral Hospital, Royal Veterinary College, Hertfordshire, UK.
Corley
Kevin T T
KT
D000768:Anesthesia, General / Q000662:veterinary*; D000818:Animals; D002302:Cardiac Output / Q000502:physiology*; D006736:Horses / Q000502:physiology / Q000601:surgery*; D007201:Indicator Dilution Techniques / Q000662:veterinary; D018021:Lithium Chloride; D016343:Monitoring, Intraoperative / Q000379:methods / Q000662:veterinary*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011674:Pulse
D018021:Lithium Chloride