The Effect Of 5 % Sodium Bicarbonate Injection On Blood Gas Of Patients Underging One-Lung Ventilation

IntroductionDuring one-lung ventilation(OLV),the blood without being oxygenated that coming from the other lung returns to left ventricle directly,which promoting ventilation perfusion(V/Q) imbalance,venous admixture,increasing intrapulmonary shunt(Qs/Qt),increasing PaCO₂ and decreasing PaO₂,so there is the inclination of respiratory acidosis and metabolic acidosis.5%sodium bicarbonate(NaHCO₃) injection has been used widely for the patients in serious acid-base disturbance or cardiopulmonary resuscitation.It's not reported that 5%NaHCO₃ injection has been used for the patients undergoing thoracic surgery with OLV and this study is to evaluate the effects of 5%NaHCO₃ injection on these patients' arterial blood gas.Materials and methodsSixty patients(44 male and 16 female),ASAâ… orâ…¡,having scheduled for thoracic surgery,age 18～65yr,weight 55～80kg,were randomly divided into three groups(n=20 respectively),contrast group(groupâ… ) and experiment groups(groupâ…¡and groupâ…¢).In groupâ…¡:5%NaHCO₃ injection 30ml.In groupâ…¢:5%NaHCO₃ injection 60ml.All patients received midazolam 3mg and atropine 0.5mg im 30min before operation.After arrival in the operation room,two cannulas were placed to infuse Ringers Lactate solution at 5～10ml/(kg·h).Radial artery was cannulated at upper arm of the operation lateral.The patients were continuously monitored BP,MAP, HR,SpO₂,ECG,CSI,P_ETCO₂ and MAC.Three groups were used the same general anesthesia(GA).All patients were induced with fentanyl 3μg/kg,propofol 1.5～2 mg/kg and succinylcholine 1.5mg/kg iv and maintained with inhalated isoflurane(1 %～2%),continuously infused remifentanil 0.1～0.2μg/(kg·min) and intermittent vecuronium 0.02～0.03mg/kg iv.During OLV,continuously infused 5%NaHCO₃ injection(groupâ…¡:1ml/min and groupâ…¢:2ml/min).The patients were mechanically ventilated after bronchial intubation(RR 12～18bpm,VT 8～10ml/kg,I:E=1:1.5 or 2), CSI was maintained at 38～60.P_ETCO₂ was maintained at 35～45mm Hg.The change of MAP was less than baseline 20%.1ml blood samples were taken from the radial artery before anesthesia(T₀),before of OLV(T₁),30min after OLV(T₂),before the end of the operation(T₃) for determination.ResultsThere were no statistical differences among the three groups in age,M/F ratio, body weight,and left/right open thoacotomy ratio et al(P＞0.05).Comparing in the same group:PaO₂,SaO₂,Qs/Qt and[CL^-]were all increased, while BE,[K⁺]and SBP,DBP were all decreased after anesthesia as compared with the base line values in the same group(P＜0.05 or P＜0.01).Comparing with the base line values(T₀) in the same group:[K⁺](T₃) and pH(T₂,T₃) were decreased in groupâ… (P＜0.05 or P＜0.01),while SpO₂(T₁,T₃) in three groups and HR(T₂) in groupâ…¢were increased(P＜0.05 or P＜0.01).Comparing among the groups:SaO₂(T₂) were higher in groupâ…¢than those in groupâ… and in groupâ…¡(P＜0.05),while BE(T₂,T₃) and DBP(T₂) were higher in groupâ…¢than those in groupâ… (P＜0.05 or P＜0.01).All patients showed recovery without delay.Comparing with in groupâ… ,the patients in groupâ…¢recovered rapidly(P＜0.05).DiscussionBlood gas analysis,as one of the monitoring items for clinical anesthesia,is essential to the patients with OLV in thoracic surgery,which is decided by the patients' changes of pathophysiology.The blood without being oxygenated of the operating lung returns to left ventricle directly,which promoting V/Q imbalance,decreasing PaO₂. Though the effect of hypoxic pulmonary vasonstriction(HPV) can reduce Qs/Qt,there was still 9 percent to 27 percent of the patients that had occurred obvious hypoxemia.There is the inclination of respiratory acidosis and metabolic acidosis because of V/Q imbalance,venous admixture,increasing PaCO₂,decreasing PaO₂,histogenous hypoxia and increasing of the metabolism without oxygen.Renal can't compensate for respiratory acidosis immediately and pulmonary with mechanical ventilation can't compoensate for metabolic acidosis,which lead to the decreasing of pH.5%NaHCO₃ injection was used during OLV in this study.Results showing as follow:1.Respiratory system being kept well:SaO₂(T₂) in groupâ…¢was higher than that in groupâ… or in groupâ…¡.Comparing with the normality,the relationship of PaO₂ to SpO₂ and SaO₂ had changed.The causes can be:â‘ There is the possibility of monitoring error of SpO₂.â‘¡Oxygemoglobin dissociation curve moves to the right which affects the relationship between SpO₂ and PaO₂.2.Slight change of acid and base:pH after anesthesia in three groups was decreased as compared with the base value,pH and BE were obviously decreased in groupâ… .But BE(T₂,T₃) were higher in groupâ…¢than those in groupâ… .pH and BE of the patients given 5%NaHCO₃ injection 60ml had slight change,which reduced the movement of oxygemoglobin dissociation curve to the right and increasing SaO₂. It's good for blood to diliver oxygen.Using 5%NaHCO₃ injection 60ml can't increase patient's PaCO₂.3.The effect on electrolyte:[K⁺]was decreased after anesthesia in three groups which can be related to hemodilution.[Na⁺]and anion gap(AG) were unchanged after anesthesia,but[Cl^-]was all increased and there was the inclination of hyperchloremia and metabolic acidosis.4.Hemodynamic stability:SBP,DBP were decreased after anesthesia in three groups as compared with the base value.DBP(T₂) was higher in groupâ…¢than that in groupâ… .HR(T₂) was higher than HR(T₀) in groupâ…¢.The causes lie in:â‘ Anesthesia by itself can decrease blood pressure and make HR slow.â‘¡The increase of [H⁺]can reduce the strength of myocardial shrinking.â‘¢The increase of[H⁺]can reduce the cardiovascular response to catecholamines.5.Others:The patients in groupâ…¢recovered rapidly and side effects were significant reduction.It's possible for the patients that 5%NaHCO₃ injection 60ml makes their physiology stability and benefits the metabolic role of drugs. ConclusionThe patients were used 5%NaHCO₃ injection 60ml during OLV in thoracic.It can keep respiration stability,reduce the change of pH and BE,reduce the movement of oxygenmoglobin dissociation curve to right and increase SaO₂ which help blood deliver oxygen.It is good for patients to keep pH 7.4 or preoperative status and maintaining normal physiological action of the organism.60ml 5%NaHCO₃ injection can't increase PaCO₂ of the patients during OLV.There isn't obviously effect on increasing Qs/Qt.