Reliability of the commonly used oxygenation indices is still under debate (Cane et al. 1988). The aim of this study was to evaluate the correlation of different oxygenation indices with shunt fraction (Q . s/Q . t) in horses under general anaesthesia. Six female horses were anaesthetized with xylazine, diazepam, ketamine and isoflurane and placed in left lateral recumbency. The trachea was intubated and lungs were mechanically ventilated with 100% O2. A Swan-Ganz catheter was introduced in the left jugular vein and advanced into the pulmonary artery. Horses received different infusion rates of dobutamine (2.5, 5 and 7.5 lg kg)1 minute)1) in order to change cardiac output and Q . s/Q . t. For each horse 10 samples of arterial and mixed venous blood were simultaneously obtained at fixed times. Arterial and venous haemoglobin concentration and O2 saturation (cooximeter), PaO2, PvO2 and barometric pressure were measured. Arterial (CaO2), mixed venous (CvO2) and capillary (Cc¢O2) O2 contents were calculated. Oxygenation indices (Table 1) were compared with Q . s/Q . t measurements using Pearson correlation tests. Fifty-five paired measurements were obtained. Results are displayed in Table 1. Table 1 Indices Median (range) r p Q . s/Q . t: (Cc¢O2–CaO2)/ (Cc¢O2–CvO2) 33.0 (55.8–10.8) 1 – Alveolar-arterial PO2 difference: P(A-a)O2 43.2 (25.0–66.5) kPa 0.39 <0.01 PaO2-to-FiO2 ratio: PaO2/FiO2 42.6 (20.6–61.4) kPa )0.38 <0.01 F-shunt: (Cc¢O2-CaO2)/ [(Cc¢O2-CaO2) + 3.5 mL dL)1] 26.1 (38.0–15.5) 0.79 <0.01 Arterial-to-alveolar PO2 ratio: PaO2/PAO2 0.49 (0.70–0.23) )0.39 <0.01 Respiratory index: P(A-a)O2/PaO2 1.00 (3.22–0.40) 0.24 >0.05 In healthy horses under general anaesthesia Fshunt had a stronger correlation with Qs/Qt compared to the other oxygenation indices. Reference: Cane RD, Shapiro BA, Templin R et al. (1988) Unreliability of oxygen tension-based indices in reflecting intrapulmonary shunting in critically ill patients. Crit Care Med 16, 1243– 1245.
Comparison of different oxygenation indices for the estimation of intrapulmonary shunt in horses under general anaesthesia.
BRIGANTI, ANGELA;SGORBINI, MICAELA;BREGHI, GLORIA;
2011-01-01
Abstract
Reliability of the commonly used oxygenation indices is still under debate (Cane et al. 1988). The aim of this study was to evaluate the correlation of different oxygenation indices with shunt fraction (Q . s/Q . t) in horses under general anaesthesia. Six female horses were anaesthetized with xylazine, diazepam, ketamine and isoflurane and placed in left lateral recumbency. The trachea was intubated and lungs were mechanically ventilated with 100% O2. A Swan-Ganz catheter was introduced in the left jugular vein and advanced into the pulmonary artery. Horses received different infusion rates of dobutamine (2.5, 5 and 7.5 lg kg)1 minute)1) in order to change cardiac output and Q . s/Q . t. For each horse 10 samples of arterial and mixed venous blood were simultaneously obtained at fixed times. Arterial and venous haemoglobin concentration and O2 saturation (cooximeter), PaO2, PvO2 and barometric pressure were measured. Arterial (CaO2), mixed venous (CvO2) and capillary (Cc¢O2) O2 contents were calculated. Oxygenation indices (Table 1) were compared with Q . s/Q . t measurements using Pearson correlation tests. Fifty-five paired measurements were obtained. Results are displayed in Table 1. Table 1 Indices Median (range) r p Q . s/Q . t: (Cc¢O2–CaO2)/ (Cc¢O2–CvO2) 33.0 (55.8–10.8) 1 – Alveolar-arterial PO2 difference: P(A-a)O2 43.2 (25.0–66.5) kPa 0.39 <0.01 PaO2-to-FiO2 ratio: PaO2/FiO2 42.6 (20.6–61.4) kPa )0.38 <0.01 F-shunt: (Cc¢O2-CaO2)/ [(Cc¢O2-CaO2) + 3.5 mL dL)1] 26.1 (38.0–15.5) 0.79 <0.01 Arterial-to-alveolar PO2 ratio: PaO2/PAO2 0.49 (0.70–0.23) )0.39 <0.01 Respiratory index: P(A-a)O2/PaO2 1.00 (3.22–0.40) 0.24 >0.05 In healthy horses under general anaesthesia Fshunt had a stronger correlation with Qs/Qt compared to the other oxygenation indices. Reference: Cane RD, Shapiro BA, Templin R et al. (1988) Unreliability of oxygen tension-based indices in reflecting intrapulmonary shunting in critically ill patients. Crit Care Med 16, 1243– 1245.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
