Correlation between the Severity Prediction Index score (SPI-2) and tear production in 100 critically ill dogs admitted to the intensive care unit

urpose: To determine the relationship between the severity of a systemic disease and tear production (TP) in critically ill dogs admitted to the intensive care unit. Methods: One hundred dogs of various breeds and both sexes were enrolled in the study. Inclusion criteria were as follows: presence of a severe systemic disease, no anesthesiological procedures within the previous 24 h, and no therapy with drugs that could interfere with TP. Another inclu- sion criterium was the absence of any ocular abnormalities assessed by slit-lamp biomi- croscopy, indirect ophthalmoscopy, and applanation tonometry preceded by the Schirmer Tear Test type I in both eyes. For each dog the illness severity was calculated by a diagnosis independent score (Severity Prediction Index - SPI-2) which predicts probability of survival based on variation of 7 clinical parameters within 24 h of admission. Data were statistically analyzed and the Spearmann test was used to detect a possible correlation between SPI-2 score and TP. Results: In the 53 male and 47 female dogs no statistical difference in TP was found between left and right eyes. No significant effect of both, age and body weight on TP was detected. A difference related to gender was found, with intact male dogs showing a lower TP. The variables SPI-2 and TP in the critically ill dogs were correlated (P < 0.0001) and a positive correlation was detected (rs 0.957). Conclusion: This study demonstrated that tear production tends to decrease in dogs with lower SPI-2 scores, in other words in the more critically ill dogs.