Effects Of Beach-Chair Posture And Induced Hypotension On Cerebral Oxygen Saturation In Patients Undergoing Arthroscopic Shoulder Surgery

Objective：Arthrography was first used in clinic in1958.With thedevelopment of the research and the improvement of surgical techniques,arthroscopic shoulder surgery gradually become one of the chief means oftreatment of shoulder joint disease.We can observe the inside of the shoulder joint directly in Arthroscopicshoulder surgery so as to understand the situation of the joint. Meanwhile wecan handle some lesions of the shoulder joint, which can further improvediagnoses and operation accuracy, and guide the choice of the operationapproaches, which help to avoid the blind detection and unnecessary injury.Through arthroscopic shoulder surgery, we can not only maintain normalphysiology functions of the original shoulder joint, but also gain bettertreatment effects such as less trauma and faster recovery. Arthroscopicshoulder technology has become the optimal diagnosis and treatmentapproaches of many joint illnesses such as glenoid labrum tear of shoulderjoint, the impact injury, rotator cuff disease, shoulder joint instability andshoulder joint osteoarthritis. However, in order to perform an operationsmoothly, the patients usually have to take special posture. Besides, because ofthe absence of tourniquet in the shoulder joint surgery, the anesthesiologistusually induce hypotension in operation in order to avoid intra-operativehemorrhage. It has been a long debate that whether operative posture andintra-operative blood pressure and other related factors would affect the brainblood oxygen saturation or not.With the development of arthroscopic research, progress of surgerytechnology and the mounting patients, beach chairs posture are applied toclinic more than before. However, there is not much research on cerebral blood oxygen saturation which may be affected by intra-operative posture andinduced hypotension of patients. In this study, we make patients take beachchairs posture and using near infrared spectral spectrum technique to exploretheir influences on cerebral blood oxygen saturation.Methods:1Choice of subjects Screen thirty-five patients from november of2010tomarch of2013, Subjects (16males and19females from twenty to eighty yearsold (average49.0±13.5); including10left shoulder disease cases and25rightcases.2Selection criteria who required arthroscopic shoulder prospectie werestudy of diagnosis and treatment as follows:1） Patients who has surgerycontraindications such as serious lung disease, anemia, heart disease, ischemicencephalopathy, severe kidney disease, severe hepatic disease, severehypertension and uncontrolled diabetes and so on;2） patients who developedsevere disease of the nervous system.3） All of the participants in theexperiment were assessed by the simple mental state assessment method toevaluate (MMSE) one day before the operation in order to screen the patientswhose preoperative MMSE score is lower than23.3Operation methods The patients took beach chair posture and generalanesthesia, when they accept pressurized water flooding downstreamarthroscopic surgery, which were performed by the same surgeon. Afteranesthesia induction, mechanical ventilation was applied to maintain carbondioxide partial pressure between35to40mmHg. Use propofol and fentanyl tomaintain the average arterial pressure between60to65mmHg. Near infraredspectrometer sensor (INVOS5100; Somanetics, Troy, MI, USA) was appliedon2cm above of the horizon of forehead brow ridge in order to measurecerebral blood oxygen saturation.4Measurements of data of the experiment4.1The MAP and rSO2were recorded at the following time points: beforeinduction (T0), immediately after induction (T1[baseline]), after beach-chairposture (T2), immediately after induced hypotension (T3),1hour after induced hypotension (T4), and after supine posture at the end of surgery (T5).Cerebral desaturation was defined as a reduction in cerebral rSO2to less than80%of baseline value for5seconds or longer.4.2All of the subjects in the experiment were assessed by the simple mentalstate assessment method to evaluate (MMSE) one day after the operation inorder to compare with the preoperative data.Results:1One of the thirty-five patients adapted general operation instead ofarthroscopy surgery because of substantial situation. According to the resultsof continuous blood gas analysis from thirty-four patients who participated inresearch, it was indicated that no acidosis, hypoxia, hypercapnia and no lowcarbonic acid hematic disease have been found.2No significant differentiation of oxygen and carbon dioxide partialpressure have been found in all of the monitoring point indicated by blood-gasanalysis. Although the lactic acid value in T5higher than T2(P<0.05), the T5baseline levels of lactic acid was not significantly higher than T1. What’s more,postoperative hemoglobin values were lower than preoperative ones.3The mean arterial pressure decreased with the extension of theoperation time. The mean arterial pressure at T2, T3, T4were lower than theT1and T0(P<0.05). While the mean arterial pressure at T3, T4weresignificantly lower than T2. Brain blood oxygen saturation also fell during theoperation, and blood oxygen saturation at T1was3%lower than T2, while T3had no significant different with T4（67.6%±4.8%vs68.2%±4.8%）; bloodoxygen saturation at T3and T4were lower than T1and T2（P<0.05）4There were two of the subjects whose blood oxygen saturation valuereached turned to be extremely low. One was a64-year-old female, the patienthad no background diseases, which induced hypotension after the meanarterial pressure of patients to lower than60mmHg. We immediately reducedthe dosage of fentanyl, and then her mean arterial pressure rose to more than60mmHg, and blood oxygen saturation has been restored to normal. Anothercase was a53-year-old male patient who had a history of high blood pressure. His cerebral blood oxygen saturation decreased when he adapted beach-chairposture, and it disappeared immediately after we reduced the fentanyl infusionvolume, and drip into the adrenaline. His blood oxygen saturation rosed morethan80%. Assessed the patient’s cognitive ability through a simple mentalstate assessment method (MMSE) showed that all patients before and aftersurgery had no significant difference.Conclusions:1Blood-gas analysis showed that the beach-chair posture inducedhypotension were not significantly affected the oxygen and carbon dioxidepartial pressure、Lactic acid and hemoglobin content2MAP and cerebral blood oxygen saturation detection indicated that thebeach-chair posture hypotension may decrease MAP and cerebral bloodoxygen saturation and they had same variation tendency.3The two special cases indicated that cerebral blood oxygen saturationwould become extremely low when the MAP decreased to60mmHg.4The beach-chair posture induced hypotension in arthroscopic operationmay decrease the cerebral blood oxygen saturation, so we should detect thecerebral blood oxygen saturation closely.