The Effect Of Pneumoperitoneum In The Steep Trendelenburg Position On The Balance Between Cerebral Oxygen Supply And Demand And Metabolism In The Aged

The contents of cranial cavity are composed of the brain tissue, blood and cerebrospinal fluid. The three parts of the total volume is basic fixed after cranial seam closed, about1400to1500ml. Any part of the volume change will cause the other part of the volume compensatory change. Normally, intracranial pressure can volatility in the small scope. The normal value is0.7to2.0kPa(5.3to13.5mmHg).Intracranial pressure can remain unchanged relying on their own automatic adjustment mechanism, when mean arterial pressure fluctuates from50to150mmHg, but beyond the limit, will parallel change with rising or falling of the blood pressure, Except the part of intracranial venous blood is squeezed extracrania, mainly through the generation of cerebrospinal fluid and backflow. Cerebrospinal fluid flows in a particular direction, from the sagittal sinus to superior sagittal sinus by arachnoid granulations, eventually cerebrospinal fluid flows back to the vein. The backflow of cerebrospinal fluid (or absorption) mainly depends on intracranial veins pressure and the difference of cerebrospinal fluid pressure, and the effective colloid osmotic pressure between blood brain barrier. Therefore, intravenous pressure is also produce and maintain one of the main factors of cerebrospinal fluid pressure, whether systemic venous blood pressure or intracranial veins blood pressure will influence the cerebrospinal fluid pressure. In laparoscopic surgery, the carbon dioxide (CO2) is used to set up the artificial pneumoperitoneum, to provide enough operation space. But, pneumoperitoneum cause celiac pressure (IAP) increases, the increased intra-abdominal pressure through the chest transfer will increase circumfluence resistance of internal jugular vein, thus influence backflow of intracranial veins, also can restrict the inferior vena cava, cause vertebral vein plexus pressure increases, the formation and backflow cerebrospinal fluid changes. On the other hand, the carbon dioxide absorbed into the bloodstream through the peritoneum expands blood vessel of brain, and increases blood of the brain. Arterial partial pressure carbon dioxide (PaCO2) range from25to55mmHg, cerebral blood volume can happen20ml of change. The mechanical and chemical factors are likely to cause of cerebrospinal fluid pressure changes, at the same time, trendelenburg will also increases intracranial venous resistance.In recent years, with cavity mirrors technology continues to mature and improve, the surgical treatment of the colorectal cancer in old patients more and more choices in the cavity mirrors, less bleeding, little traumatic, less complications and postoperative recovery fast. However, this technology may cause intracranial pressure increases and brain edema, and then lead to brain oxygen supply and demand imbalances and the change of energy metabolism, because of organ function degradation, reduced reparative ability, long time of Carbon Dioxide Pneumoperitoneum and trendelenburg. Therefore, there are still different views on laparoscopic techniques used for elderly patients. This study will observe the effect of pneumoperitoneum in the steep Trendelenbure position on the balance between cerebral oxygen supply and demand and metabolism in the aged during laparoscopic radical resection of rectum cancer by the change of jugular bulb venous saturation(SjvO2),the cerebral arteriovenous content oxygen difference(Da-jO2), glucose, lactate and so on.Patients and methodsFollowing approval by the Hospital Ethics Committee and written informed consent, forty-nine patients of American Society of Anesthesiologist(ASA)Ⅰ and Ⅱ aged35～80yr undergoing laparoscopic radical resection of rectum cancer.37cases were male, female12patients. Put them into two groups, one of which was35-59years old and the other was60-80years old. Patients who deviated by more than30%from their ideal weight were excluded. None of the patients had evidence of cerebrovascular, serious cardiopulmonary, renal, hepatic, or metabolic disease.All of the patients did not use premedication, A standard anesthetic technique was used. Anesthesia was induced with i.v. midazolam(0.03mg/kg), propofol (1.5mg/kg), fentanil (3～4ug/kg) and cisatracurium besylate (0.2mg/kg). Ventilator settings were tidal volume7ml/kg, inspiratory:expiratory ratio1:2, respiratory rate14bmp/min, inspired02fraction70%with air and an inspiratory fresh gas flow of21/min. Anesthesia was maintained with1.3～1.5MAC end-tidal concentrations of sevoflurane, total of fentanil less than9ug/kg. After induction of anesthesia, a20-G radial artery catheter was inserted for continuous arterial pressure and blood sampling. The mean arterial pressure (MAP) was maintained within20%of baseline in all patients. A18-G one-lumen central venous catheter was retrorse inserted into the left internal jugular vein for monitoring central venous pressure (CVP). the depth of the tube is from puncture point to breed dash forward of the body surface distance(about10～14cm).For BIS measurement, sensors were placed bilaterally at least2cm above the eyebrow on the left sides of the forehead according to the manufacturer’s instructions before induction of anesthesia. The BIS value was continuously monitored, and maintained in45～55. After anesthesia induction, the abdominal cavity was insufflated with CO2gas pressure set to14～16mmHg first and then patients were placed in a30°～35°rendelenburg position (head down position) during surgery.Mean arterial pressure(MAP),Heart rate (HR), Jugular bulb blood pressure(JBP),Peak airway pressure(PIP), Arterial oxygen partial pressure (PaO2),Arterial partial pressure carbon dioxide(PaCO2),Arterial oxygen saturation(Sa02),Jugular bulb oxygen partial pressure(PjvO2),J ugular bulb venous saturation(Sjv02),Artery glucose level(Aglu),Jugular bulb glucose level(Jglu) were recorded immediately before pneumoperitoneum (T1;baseline),30min after pneumoperitoneum (T2),60and90min after the pneumoperitoneum(T3, T4). Hemoglobin, SjvO2, PaO2, PaCO2and so on were measured by arterial blood gas analysis at all time periods,According to formula(Fick):Da-jO2=CMRO2·CBF-1, the following index we calculated.(1)Da-jO2=CaO2(arterial oxygen content)-CjvO2(jugular bulb oxygen content).(2)CaO2=1.36×Hb(hemoglobin)×SaO2+0.003×PaO2.(3)CjvO2=1.36×Hb×SjvO2+0.003×PjvO2.(4)CPP(cerebral perfusion pressure)=MAP-CVP(central venous pressure).(5)Da-jglu(cerebra arteriovenous plasma glucose difference)=Aglu-Jglu.Statistical analysis was performed using SPSS version13.0(SPSS Inc., Chicago, IL). To calculate sample size, we used the mean and standard deviation (SD) of the first six patients. All data are expressed as mean±SD. Changes in values with time were analyzed with repeated measures analysis of variance. Differences within the group were analyzed with a paired t-test with Bonferroni correction. A value of P<0.05was considered as statistically significant. The graphs were made using office 2003.ResultsForty-nine patients were enrolled and no patient was excluded from the analysis. The Hb level were maintained constant during the study period.The increase in MAP, JBP, PaCO2,CPP and PIP was statistically significant (P <0.01, respectively). MAP, JBP, PaCO2, CPP and PIP were significantly increased at T2, T3and T4compared with that at T1in both groups.The change in A and B Da-jO2and SjvO2were statistically significant(P<0.01, respectively). Da-jO2was decreased and SjvO2was increased significantly at T2, T3and T4compared with the baseline value at T1.Both A and B Da-jglu decreased significantly at T3and T4compared with the baseline value at T1. But there were no significant differents between the two groups. Plasma lactic level acid were constant in both groupsConclusionsDuring laparoscopic radical resection of rectum cancer, the balance between cerebral oxygen supply and demand, as assessed by SjvO2, were disorganized, oxygen supply exceeded oxygen consumption in the aged, which suggests that the procedure induced cerebral hyperperfusion, the cerebral ingestion of glucose was decreased, but without impacting on the brain energy metabolism. Elderly patients with brain oxygen supply and demand more serious imbalance compared with the young.