Accuracy of different oxygenation indices in estimating intrapulmonary shunting at increasing infusion rates of dobutamine in horses under general anaesthesia.
The aim of this study was to evaluate the correlation of commonly used oxygenation indices with venous admixture (Qs/Qt) in anaesthetised horses under different infusion rates of dobutamine. Six female horses were anaesthetised with acepromazine, xylazine, diazepam, ketamine, and isoflurane, and then intubated and mechanically ventilated with 100% O2. A Swan-Ganz catheter was introduced into the left jugular vein and its tip advanced into the pulmonary artery. Horses received different standardised rates of dobutamine. For each horse, eight samples of arterial and mixed venous blood were simultaneously obtained at fixed times. Arterial and venous haemoglobin (Hb) concentration and O2 saturation, arterial oxygen partial pressure (PaO2), venous oxygen partial pressure (PvO2), and barometric pressure were measured. Arterial (CaO2), mixed venous (CvO2), and capillary (Cc'O2) oxygen contents were calculated using standard formulae. The correlations between F-shunt, arterial oxygen tension to fraction of inspired oxygen ratio (PaO2/FiO2), arterial to alveolar oxygen tension ratio (PaO2/PAO2), alveolar to arterial oxygen tension difference (P[A - a]O2), and respiratory index (P[A - a]O2/PaO2) were tested with linear regression analysis. The goodness-of-fit for each calculated formula was evaluated by means of the coefficient of determination (r(2)). The agreement between Qs/Qt and F-shunt was analysed with the Bland-Altman test. All tested oxygen tension-based indices were weakly correlated (r(2) < 0.2) with the Qs/Qt, whereas F-shunt showed a stronger correlation (r(2) = 0.73). F-shunt also showed substantial agreement with Qs/Qt independent of the dobutamine infusion rate. F-shunt better correlated with Qs/Qt than other oxygen indices in isoflurane-anaesthetised horses under different infusion rates of dobutamine.
Dipartimento di Scienze Veterinarie, Università di Pisa, Pisa, Italy.
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Briganti
Dipartimento di Scienze Veterinarie, Università di Pisa, Pisa, Italy.
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Portela
DETO Sezione di Anestesia e Terapia Intensiva, Università degli Studi di Bari, Bari, Italy.
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Grasso
Dipartimento di Scienze Veterinarie, Università di Pisa, Pisa, Italy.
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Sgorbini
Dipartimento di Scienze Veterinarie, Università di Pisa, Pisa, Italy.
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Tayari
Dipartimento di Scienze Veterinarie, Università di Pisa, Pisa, Italy.
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Bassini
Dipartimento di Scienze Veterinarie, Università di Pisa, Pisa, Italy.
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Vitale
Department of Experimental and Clinical Medicine, Internal Medicine and Cardiology, AOUC Careggi, University of Florence, Florence, Italy.
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Romano
D.E.T.O. Sezione di Cliniche Veterinarie e Produzioni Animali, Università degli Studi di Bari, Bari, Italy.
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Crovace
Dipartimento di Scienze Veterinarie, Università di Pisa, Pisa, Italy.
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Breghi
D.E.T.O. Sezione di Cliniche Veterinarie e Produzioni Animali, Università degli Studi di Bari, Bari, Italy. Electronic address: francesco.staffieri@uniba.it.
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Staffieri
D000768:Anesthesia, General; D000818:Animals; D004280:Dobutamine / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D006736:Horses / Q000097:blood*; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption; D010313:Partial Pressure; D011659:Pulmonary Gas Exchange; D012119:Respiration
D004280:Dobutamine; D010100:Oxygen
Anaesthesia; F-shunt; Horse; Intrapulmonary shunt; Oxygenation index