RESPIRATORY EMERGENCIES IN DOGS: EVALUATION OF ARTERIAL BLOOD GAS AND RADIOGRAPHIC FINDINGS

Objective: To evaluate arterial blood gas (pH, PaO2, PCO2, SO2 P/F ratio, P[A-a]O2 gradient and HCO3-) and pulmonary radiographs in dogs presented in emergency setting with respiratory distress. Materials and Methods: Arterial blood was obtained from the dorsal pedal artery at room air (FiO2 21%), were analyzed (ABL 700 seires, Radiometer-Copenhagen). A chest radiography was performed for each patient using a digital radiological equipment (Multimage, Cosmovet). Radiographs were evaluated for presence of 4 distinct pulmonary patterns: normal, alveolar, interstitial and mixed pattern. Animals were divided in 2 groups according to outcome: survivor (S) and not survivor (NS). Normal distribution was assessed using D’Agostino-Pearson test. T student test and Mann Whitney were used to compare pH, PaCO2, PaO2, P[A−a]O2 gradient, PaO2/FiO2, HCO3- and SO2 in (S) versus (NS) respectively. ANOVA one-way was used to compare radiographic pattern with PaO2/FiO2 and P[A−a]O2 gradient values. Results: thirty-nine dogs were enrolled. Nine out of 39 (23%) did not survive (1 euthanized), 30/39 (77%) survived. Incidence of a PaO2/FiO2 <200mmHg was 13%, while a PaO2/FiO2 between 200-300 mmHg was found in 10/39 (25.6%) of subjects. A P[A-a]O2 gradient >20 mmHg was found in 30/39 (77%) dogs. In (S) group pH resulted 7.39±0.04, PaO2 77.2±18 mmHg, PCO2 33±5.7 mmHg, SO2 97.5% (66-101,8%), PaO2/FiO2 368±85 mmHg, P[A-a]O2 gradient 31±17 mmHg, HCO3- 19.3±3 mEq/L. In (NS) group pH resulted 7.33±0.1, PaO2 51±17 mmHg, PCO2 31.2±7 mmHg, SO2 74% (46.5-100,6%), PaO2/FiO2 242.5±84 mmHg, P[A-a]O2 gradient 59.7±22,4 mmHg, HCO3- 16.5±4.7 mEq/L. Alveolar pattern was identified in 9/39 (23.8%) dogs, interstitial pattern in 6/39 (15.3%), mixed pattern in 16/39 (41%), normal pattern in 3/39 (7.6%). In 5/39 was identified pleural effusion and pneumothorax. The mortality rate of alveolar pattern group (44%) was greater than other pattern groups. The Mann-Whitney test revealed a significant difference for pH, PaO2, SO2, PaO2/FiO2, P[A-a]O2 gradient and bicarbonate between (S) and (NS) (p<0.05). No statistically significant difference was found for radiographic pulmonary patterns with PaO2/FiO2 (p=0.5) and P[A−a]O2 gradient values (p=0.4). Conclusion: animals with respiratory distress in the emergency setting are at higher risk of death when alveolar pattern and PaO2/FiO2 lower than 200 mmHg are present.