Comparisons between Classic Shunt and Non-Invasive Shunt in One-Lung Ventilated and Hemodiluted Dogs / 대한마취과학회지

BACKGROUND: As the clinical application of non-invasive shunt estimation to operation under one-lung ventilation has not been reported, this study was carried out to evaluate the validity and accuracy of the non-invasive shunt estimations in one-lung ventilation with hemodilution. METHODS: Following general anesthesia with enflurane 0.5 1 vol.% and 100% oxygen in ten Mongrel dogs (B.W. around 16 kg), tracheostomy and insertion of left-side endobronchial tube and one-lung ventilation were performed. Acute normovolemic hemodilution was produced by sequential hemodilution with hydroxyethyl starch. The intrapulmonary shunt (QS/QT) was calculated by the classic shunt equation, by the oxygen contents-based estimated shunt equation, and by oxygen tension-based estimations such as alveolar to arterial oxygen difference (P(A-a)O2), respiratory index (RI, P(A-a)O2/PaO2), arterial oxygen tension to alveolar oxygen ratio (PaO2/PAO2), and PaO2 to FiO2 ratio. To assess the quantitative accuracy of the estimated shunt, the data were divided arbitrarily into two groups on the basis of the mean arteriovenous oxygen content difference (C(a-v)O2) being 3.6 ml/dl or greater (group 1) and less than 3.6 ml/dl (group 2). Relationships to QS/QT were analyzed by simple linear regression. RESULTS: In 104 measurements, the correlation between QS/QT and non-invasive shunt were poor (r = 0.66 - 0.76). However, in group 1 (n = 45), the correlation between QS/QT and the estimated shunt were very good (r = 0.93) and good for P(A-a)O2 (r = 0.83), RI (r = 0.87), PaO2/PAO2 (r = - 0.84), and PaO2/FiO2 (r = - 0.85). In group 2 (n = 58), the correlation between QS/QT and non-invasive shunt were worse than in group 1. Group 2 had lower hematocrit (20.6% vs 26.7 %, P < 0.001), higher cardiac output, and lower pulmonary and systemic vascular resistance than group 1 (P < 0.05). The difference between the estimated shunt and the classic shunt in group 1 remained constant when the classic shunt was increased further. However, the difference in group 2 was enhanced by the increment of the classic shunt. CONCLUSIONS: We conclude that even if the non-invasive shunt estimation might be affected by hemoglobin and cardiac output, it is a viable method in mild hemodiluted patients with good cardiovascular reserve.

The Effects of Thoracic Epidural Anesthesia on Pulmonary Shunt during One Lung Anesthesia / 대한마취과학회지

BACKGROUND: Hypoxemia during one lung ventilation (OLV) for thoracotomy in patients in the lateral position remains a clinical problem. And thoracic epidural anesthesia (TEA) during one lung ventilation recently has been combined with general anesthesia in our clinical practice for thoracic surgery. Then the effects of TEA combined with general anesthesia on PaO2 remains controversial. The aim of this study to investigate whether thoracic epidural anesthesia (TEA) affect PaO2 and pulmonary shunt during one lung anesthesia. METHODS: Fifteen patients undergoing lobectomy with one lung ventilation were examined. Each group was injected normal saline (control group, n = 7) or 1% lidocaine (TEA group, n = 8) 8 ml through thoracic epidural catheter after induction. We compared pulmonary shunt fraction (Qs/Qt) after OLV 30, 60 minutes and after two lung ventilation (TLV). RESULTS: We found the significant increases of intrapulmonary shunt fraction (%) in the TEA group compared to control group at each event, OLV30, 60 and TLV. And significant increase of intrapulmonary shunt was found after one lung ventilation in the both groups. CONCLUSIONS: These results suggest that TEA may influence hypoxic pulmonary vasoconstriction (HPV) by blockade of sympathetic activity during OLV.