Introduction

In human dialyzed patients several functional pulmonary abnormalities have been described. The aim of this study is to evaluate arterial blood gas parameters (pH, PaO₂, PCO₂, SO₂ P/F ratio, P[A-a]O₂ gradient and HCO₃^- ) in azotemic dogs during hemodialysis (HD).

Materials and Methods

Arterial blood samples were obtained from the dorsal pedal artery at room air (FiO₂ 21%) at hospital admission (T0) and serially from an arterial catheter placed on the dorsal pedal artery at T1 (3 minutes after starting HD), T2 (2 h into treatment), T3 (end of HD) and T4 (2 h after the end of HD). Dogs were then divided according to outcome: survivors (S) and non-survivors (NS). Normal distribution was assessed using D’Agostino-Pearson. One-way ANOVA was used to compare pH, PaCO₂, PaO₂, P[A-a]O₂ gradient, PaO₂/FiO₂ and HCO₃^- at different times, and Mann-Whitney test was used to compare (S) and (NS).

Results

Twenty-two (22) azotemic dogs referred for HD were enrolled. Fifteen of 22 (46,8%) did not survive, 7/22 (32%) survived. A statistically significant difference (p<0.0001) in pH was found among T0 (7.28±0.085) vs. T2 (7.36±0.06) vs. T3 (7.38±0.06) vs. T4 (7.37±0.06) and for pH at T1 (7.26±0.067) vs. T2, T3 and T4. A statistically significant difference in PaCO₂ was found between T0 (28.9±4.43 mm Hg) and T2 (33.83±3.18 mm Hg), T3 (35.5±2.67 mm Hg) and T4 (36.5±2.8 mm Hg) and between T1 (32±3.18 mm Hg) and T4 (36.54±2.8 mm Hg). A statistically significant difference in HCO₃^- was found between T0 (13.8±4.7 mEq/L) and T2 (18±3.1 mEq/L), T3 (20±3.62 mEq/L) and T4 (19.21±3.84 mEq/L) and between T1 (14.4±4.2 mEq/L) and T2, T3 and T4. No significant differences in PaO₂, P[A-a]O₂ and %SaO₂ were found at any timepoint. No significant differences were found between survivors and non-survivors.

Conclusions

To the authors’ knowledge this is the first study evaluating oxygen tension indices during hemodialysis in dogs. A statistically significant increase in pH, PaCO₂ and HCO₃^- as a beneficial effect of hemodialysis in restoring acid-base balance was found. Ventilation to perfusion (V/Q) inequalities are the main cause of arterial hypoxemia during HD. No significant changes in oxygen tension-based indices were found. Further evaluations are recommended.

E-mail: gianilaceccherini@virgilio.it