Effect of propofol on stroke volume and shunt in patients undergoing thoracic surgery with the exclusion of one-lung ventilation during planned operations
© BioMed Central Ltd. 2004
Published: 15 March 2004
Thoracic surgery usually requires anaesthesia excluding one-lung ventilation (OLV). OLV causes the increase of shunt (Qs/QT), the clinical exponent of which is the lowering of oxygen pressure in blood (and the lowering of SpO2). The defence mechanism, which prevents lowering of oxygen pressure, is hypoxic pulmonary vasoconstriction (HPV) in the lung excluded from ventilation. The anaesthetics used for anaesthesia (especially inhalatory ones) inhibit HPV.
The purpose of this study is the evaluation of the effect of anaesthesia total intravenous anaesthesia (TIVA) (oxygen, air, propofol) on shunt and some haemodynamic parameters in patients undergoing operations connected with neoplastic lung disease requiring OLV. Shunt and haemodynamic parameters were evaluated using the data collected from the catheter introduced to the pulmonary artery (Swan–Ganz catheter).
Materials and methods
The study was carried out on 11 patients (American Society of Anesthesiologists [ASA]I and ASAII) undergoing planned operations. All the patients were premedicated orally with midazolam. The catheter was introduced to the pulmonary artery before the anaesthetic induction according to the pressure curve. Patients received balanced anaesthesia that was the combination of epidural anaesthesia in the thoracic segment (thoracic epidural anaesthesia: fentanyl + 0.9% saline) and TIVA (propofol according to Roberts' schema). The heart rate, blood pressure, SpO2, temperature in the pulmonary artery, pulmonary artery pressure, pulmonary capillary wedge pressure, cardiac output, cardiac index (CI) and Qs/QT were marked at nine intervals: (I) before the induction of anaesthesia (10–30 min); (II) immediately after the induction of anaesthesia (after checking the tube position) – horizontal position; (III) after determining the respiratory mixture (during two-lung ventilation) – lateral position; (IV) 5 min after starting OLV – lateral position; (V) 30 min after starting OLV – lateral position; (VI) 5 min after starting two-lung ventilation or immediately after the pulmonary artery ligation of the operated lung; (VII) 30 min after starting two-lung ventilation or immediately after pulmonary artery ligation of the operated lung; (VIII) 5–10 min before extubation; and (IX) 15 min after extubation.
The obtained results were analysed statistically: SpO2 decreased substantially (IV, V), mean arterial pressure (MAP) (V), and CO (IV) in relation to output values. A statistical increase was noticed in the pressure in the pulmonary artery (II–V, VIII) and Qs/QT (II–VIII), the highest in interval IV and V.
OLV causes the increase of Qs/QT and, consequently, the lowering of SpO2 in the 5th min (43.78%) and 30th min (35.4%) after excluding an operated lung from ventilation. OLV is connected with the lowering of SpO2 and increasing pressure in the pulmonary artery. Propofol used in TIVA causes the increase of shunt – approximately four times. Increasing Qs/QT does not cause the critical lowering of oxygen pressure in arterial blood. During TIVA a transitional decrease of CI and MAP was noticed.