The Effects Of Propofol And Sevoflurane On Pulmonary Shunt Fraction During One-lung Ventilation

Objective:The aim of this study was to compare the effects of propofol and sevoflurane during one-lung ventilation in thoracic surgery on hypoxic pulmonary vasoconstriction and pulmonary shunt fraction.Methods:40 patients scheduled for a thoracotomy were randomly assigned to Group sevoflurane (Group S) and Group propofol (Group P).1.Conventional monitorings:In the operating room,a 18-gauge peripHeral i.v. canula was inserted into a large forearm vein,monitoring electrocardiogram (ECG), blood pressure (BP), oxygen saturation (SpO2), bispectral index (BIS),and inhaling pure oxygen 5 min/L with a mask.A 20-gauge radial artery canula was inserted for invasive monitoring arterial blood pressure (ART).Subclavian central vein was selected for catheterization.2. Induction:Anesthesia was inducted in all patients with propopol 2μg/ml by additional 0.5μg/ml for every 2 minutes to unconsciousness and sufentanil 0.25 ng/ml by TCI.Rocuronium 0.6mg/kg was given after pre-oxygenation. A double-lumen tube was placed (37#male and 35# female) which position was checked using a fibreoptic bronchoscope.Ventilatory settings were identical during two-lung ventilation (TLV) and one-lung ventilation(OLV):8mg/kg tidal volume,12/min ventilation, constant flow, inspiratory to expiratory ratio of 1:2 and FIO2:100%. After positioning the patient in lateral decubitus.the correct position of double-lumen tube was checked again.3.Maintenance:Sufentanil was maintained 0.15 ng/ml by TCI. Patients were assigned to maintenance of aneasthesia with sevoflurane (Group S) or propofol (Group P) in order to maintain a BIS between 40-60.30 minutes before the end of operation, sufentanil was reduced to 0.08ng/ml. Additional boluses of i.v. rocuronium were administered as necessary. Hypotension(SBP<80mmHg) and bradycardia(heart rate<50 bpm) were treated with i.v. epHedrine and atropine, respectively. If SpO2<=90%, TLV was reinstituted and arterial and central venous blood was drawn for analysis.4. Monitoring indicators:①Record preoperative pulmonary function and arterial blood gas:a second volume (FEV1), forced vital capacity (FCV), a second ratio (FEV1/FCV), pH, arterial partial pressure of oxygen (PaO2), arterial carbon dioxide tension (PaCO2), hemoglobin (Hb), bicarbonate (HCO3-).②Record before skin incision (TLV1),15 minutes after OLV (OLV1),30minutes (OLV2), 60minutes (OLV3), and 15 minutes after TLV resumed (TLV2)-this five time points, mean arterial pressure (MAP), heart rate (HR), End-tidal carbon dioxide (EtCO2), Paw airway pressure (Paw), BIS, SpO2, plasma concentration of propofol and the concentration of End-tidal sevoflurane (Etsevo).③In TLV1, OLV1, OLV2, OLV3 and TLV2, arterial and central venous blood gas analysis was done:Record pH, Hb, HCO3-, PaO2, PaCO2, arterial oxygen saturation (SaO2), venous Oxygen pressure (PvO2), venous oxygen saturation (SvO2), and calculate pulmonary shunt fraction (Qs/Qt).④Record the time of anesthesia, surgery, extubation and recovery.⑤Record the dosage of propofol, sevoflurane, sufentanil, rocuronium, atropine and epHedrine.Results:4 patients in 40 patients were excluded:3 because of two consecutive mean BIS values outside fixed limits(2 in Group s and 1 in Group P) and 1 because of difficulty of lung exclusion.①Preoperative pulmonary function and blood gas showed no significant difference between the two groups (P> 0.05).②Hemodynamics, EtCO2, Paw:HR at each time point and MAP during TLV1,OLV1,TLV2 were no statistical difference (P> 0.05), but during OLV2 and OLV3, MAP3 and MAP4 were significant difference between the two groups (P <0.01). MAP3 (mmHg):Group S 89±12, Group P 106±13; MAP4 (mmHg): Group S 92±16, Group P 108±12. It was significantly higher in Group P than in Group S. EtCO2 and Paw were no significant differences at each time point. ③BIS and SpO2:Average BIS values were similar throughout the studied period in each group and between the two groups(P>0.05). No patients in the two groups had a SpO2 below 90%. And SpO2 was no significant difference between the two groups at each time point (P> 0.05).④PaO2:The lowest PaO2(mmHg) was 143.11±66.49 in Group S during OLV2;and 207.67±100.66 in group P during OLV3. From TLV to OLV,PaO2 decreased significantly (P<0.05) in the two groups; PaO2 was similar in at the same time point (P> 0.05).⑤Pulmonary shunt fraction:Average shunt fraction increases during OLV1,OLV2 and OLV3 were significantl in the two groups(P<0.01),and those were higher in Group S than in the Group P at these three time points(P<0.01). OLV1 shunt (%):Group S 46.3±12.2, Group P 35.3±9.8; OLV2 shunt (%)t:Group S 22.9±4.9, Group P 17.7±5.5; OLV3 shunt (%):Group S 22.7±5.9, Group P 17.8±6.0. Pulmonary shunt increased than 31.2%,29.3%,27.5%more in Group S than those in Group P respectively at the three time points. It increased largest between the two groups during OLV1.⑥Blood gas analysis:pH, Hb, HCO3-,, PaCO2, SaO2, PvO2and SvO2 were no significant differences at each time point (P> 0.05).⑦Time and dosage:The time of anesthesia, surgery, extubation, recovery were similar (P> 0.05). The dosage of sufentanil, rocuronium, atropine and epHedrine were similar (P> 0.05).Conclusion:pulmonary shunt fraction increased less by propofol than by sevoflurane. We infer that inhibition of hypoxic pulmonary vasoconstriction was less by propofol during OLV.