Introduction: Acquired cholestatic liver dysfunction and hypoxic hepatitis, distinguished by laboratory parameters, are associated with increased morbidity/mortality in intensive care unit in humans. The prognostic significance of serum total bilirubin (tBIL) and alanine-amino-transferase (ALT) in hospitalized critically ill dogs was evaluated.

Methods: Retrospective study on 622 dogs admitted to the intensive care unit (ICU) of a Veterinary University Hospital (January 2017–October 2018). Dogs with primary hepatic or hemolytic diseases, or that received red blood cells transfusion or parenteral nutrition were excluded. Medical records were reviewed for: clinical diagnosis, values of tBIL and ALT at ICU admission (T0) and after 72 hours (T72), and outcome. Non-parametric statistic was used for comparison. Significance was set at <0.05.

Results: Median values of tBIL at T0 and T72 were 0.19 mg/dl (0.01–14.47, n=515; R.I. 0.07–0.33) and 0.23 mg/dL (0.01–13.27, n=141), respectively. Median values of ALT at T0 and T72 were 66 U/L (2–14564, n=491; R.I. 15–65) and 46 U/L (1–1985, n=60), respectively. The overall mortality rate at hospital discharge was 21% (132/622). Median values of tBIL at T0 and T72 in nonsurvivors were significantly higher than in survivors: 0.24 (0.01–3.94, n=107) vs. 0.18 (0.01–14.47, n=408), p=0.0003, and 0.35 (0.1–3.9, n=25) vs. 0.22 (0.01–13.27, n=116), p=0.001, respectively. Median values of ALT at T72 in non-survivors were significantly higher than in survivors: 263 (25–1985, n=8) vs. 40 (1–603, n=529), p=0.001. A significant increase of tBIL from T0 to T72 was reported in non-survivors (n=23): 0.24 (0.01–3.94) vs. 0.35 (0.1–3.9), p=0.02. A significant decrease of ALT from T0 to T72 was reported in survivors (n=44): 64 (44–137) vs. 40 (21–57), p=0.0004. According to the AUROC curve analysis, tBIL>0.34 mg/dl had a fair accuracy (AUC=0.706) to correctly predict mortality at T72 (p=0.0002), while ALT>77 U/L had a good accuracy (AUC=0.851) to correctly predict mortality at T72 (p<0.0001).

Conclusions: In this population of critically ill dogs, mild increment of tBIL during ICU stay was revealed in non-survivors, however its clinical relevance and prognostic significance need to be elucidated. Moreover, a persistent high serum activity of ALT seems to be associated to a worse outcome.