Clinical Study On Monitoring And Efficacy Of Volume Therapy In Neurosurgery

Optimized fluid therapy plays an important role during perioperative period. Reasonable fluid management can maintain effective circulatory blood volume and stable hemodynamics, ensure sufficient organ perfusion, and improve the recovery of patients from surgery.The monitoring of circulatory blood volume is a premise for optimizing fluid therapy. In the clinic, the hemodynamic monitoring techniques with monitoring routine blood dynamics are most commonly used to evaluate the circulatory blood volume, including static cardiac filling pressure (central venous pressure and pulmonary artery wedge pressure) and volumetric indices(Right/left ventricular end-diastolic volume, Right/left ventricular end-diastolic area, intra-thoracic blood volume and global end-diastolic volume). Functional(dynamic) circulatory indices have been recently introduced into clinical practice and validated to predict fluid responsiveness for individualized fluid therapy. But it is poorly understood how about the accuracy of common monitoring parameters in different techniques to predict fluid responsiveness and the clinical application in different types of surgery.The debate on perioperative fluid management arised in the past few years, including the type(colloid versus crystalloid) and the amount (liberal versus restricted) of fluids. Studies comparing "drier" and "wetter" strategies of fluid administration are hard to interpret among different types of surgery with discrepant results. Neurosurgical patients in the perioperative period are often subjected to rapid changes in intravascular volume mainly caused by prolonged operations, haemorrhage, diuretics, fluid restriction, anaesthesia and the onset of diabetes insipidus etc. Thus, supplementary fluid infusion is demanded to maintain sufficient circulatory blood volume and perfusion pressure. However, liberal fluid management may have adverse effects on intracranial pressure, cerebral perfusion and clinical outcome. There was limited data concerning the influences of various fluid strategies on physiological status in neurosurgical patients. Further studies addressing this issue are needed to evaluate the safety and efficiency of different fluid therapies through monitoring of dynamic cardiovascular indices, intracranial pressure and cerebral oxygen supply-demand balance.Objective:To assess the ability of different hemodynamic parameters, including heart rate, mean arterial pressure, central venous pressure and stroke volume variation to predict fluid responsiveness in neurosurgical patients.Methods:Twenty five patients undergoing craniotomy were enrolled in this study. Fluid boluses of 250 ml 6% hydroxyethyl starch 130/0.4 were administered in 10min after induction of anesthesia. Haemodynamic variables were recorded before and after fluid bolus application. Fluid responsiveness was defined as an increase in stroke volume index no less than 10%. The ability to predict fluid responsiveness was assessed by calculation of the area under the receiver operating characteristic (ROC) curve.Results: SW[(13.1±2.7)% vs (7.0±2.0)%, P<0.001] and SVRI[ (2243.7±559.7) dyn·s-1·cm-5·m-2 vs (1864.3±334.6) dyn·s-1·cm-5·m-2, P = 0.002] decreased significantly after volume expansion, whereas CVP[(6.0±1.9) mmHg vs (10.4±2.3)mmHg, P<0.001] and SVI[(39.6±10.1) mL·beat·m-2 vs (47.1±9.3) mL·beat·m-2, P=0.003] increased significantly. Seventeen patients were responders to volume expansion(VE). Responders and nonresponders differed in their pre-VE values of SVV (14.3±2.0 vs 10.6±1.8, P<0.001), but not in heart rate, mean arterial pressure, central venous pressure and systemic vascular resistance index. By using receiver operating characteristic analysis, the area under the curve (±SE) for SVV (0.939±0.040) was statistically larger than those for central venous pressure(0.585±0.105), heart rate (0.683±0.096), mean blood pressure (0.573±0.116) and systemic vascular resistance index(0.505±0.109). A threshold SVV value of 12.5% allowed discrimination of responders to VE with a sensitivity of 80% and a specificity of 100%。Conclusion:SVV predicts fluid responsiveness with an acceptable sensitivity and specificity. Howerver, traditional parameters e.g. heart rate, mean arterial pressure, central venous pressure are poor predictors of fluid responsiveness.Objective:To evaluate the effects of different protocols of fluid therapy on intracranial pressure, cerebral oxygen supply-demand balance and cardiovascular function in neurosurgical patients.Methods:One hundred-sixty ASA grade I or II patients of either sex aged 18-60 yrs with BMI of 15-30 kg·m2 undergoing elective craniotomy were included in the study. The patients were randomly divided into 4 groups(n=40 each):Group LPla (liberal Plasma-Lyte A), Group LHes(liberal hydroxyethyl starch), Group RPla(restrictive Plasma-Lyte A) and Group RHes(restrictive hydroxyethyl starch). After induction Plasma-Lyte A solution or 6% hydroxyethyl starch solution was infused at the rate of 24 mL·kg-1·h-1 or 6 mL·kg-1·h-1 in different groups. At the four time points of TBase (before induction), To (after induction and hemodynamic stabilization), T30(after fluid infusion for 30min) and T60 (after fluid infusion for 60min), heart rate (HR), mean arterial pressure (MAP), central venous pressure (CVP), cardiac output index(CI), stroke volume index(SVI), stroke volume variation(SVV) and cerebral spinal fluid pressure(CSFP) were recorded. Blood samples from the radial artery and jugular bulb were collected for measurement and calculated for oxygen delivery index(DO2I), systemic vascular resistance index(SVRI) and cerebral oxygen uptake rate(CERO2). Urinary output and frequency of vasoactive drugs use were also recorded.Results:There was no significant difference in jugular bulb venous oxygen saturation(SjvO2) and CERO2 among groups and different points of time (P>0.05). DajvO2was significantly higher as compared to LPla, RPla and RHes (P=0.035,0.034,0.004 at T30 and P=0.047,0.046,0.022 at T60 respectively). SVI and CI significantly decreased after induction(P<0.001) and no significant difference was found among groups (P >0.05). In LHes, the value of SVI was significantly higher than that in RHes at T30 and T60(P=0.019 and 0.035 respectively). CI was significantly higher as compared to other three groups (LPla, RPla and RHes), the value of P was 0.003,<0.001,<0.001 at T30 and 0.005,<0.001,<0.001 at T60 respectively. After infusion of colloid solution for 30min, a significant increase in SVI and CI was found (P<0.001 and P=0.002). However, SVI and CI at T60 had no remarkable differences compared with that at T30(P=0.716 and P=0.101). Liberal infusion of crystalloid solution did not result in a significant increase in SVI and the value at T30 and T60 had no remarkable differences compared with that at T0(P=0.131 and 0.494 respectively). There was no significant difference in SVV between groups after induction(P>0.05). The mean value(±standard deviation) of the overall four groups was (13±3.5)%. SVV in LHes decreased significantly as compared to previous time point at T30 and T60(P<0.001 at both time points), which was lower than that in other three groups(P<0.001). No significant difference was found between RHes and LPla at T30 and T60(P=0.641 and 0.270 respectively). CSFP significantly decreased after induction (P<0.001). There was no significant difference between LPla and LHes at T30(P=0.100) while remarkable difference was observed at T60 with higher CSFP in LHes(P=0.011) which were clinically acceptable. CSFP in LHes increased gradually after infusion of colloid solution with remarkable difference between sequential time points(P<0.001). CSFP at T30 and T60 had no significant difference between LPla and RPla(P=0.815 and 0.217 respectively). Urinary output at T60 in LPla was significantly more than that in LHes(P<0.001), RHes(P<0.001) and RPla(P<0.001), while there was no significant difference among other three groups. The frequency of vasoactive drugs use was least in LHes(P<0.001).Conclusion:As for the fixed volume of fluid therapy, infusion of hydroxyethyl starch solution at the rate of 24 mL·kg-1·h-1 increases CI and SVI during the first 30min, which renders circulation condition more stable with less use of vasoactive drugs. The clinically acceptable increase of CSFP resulted from liberal colloid infusion will not deteriorate the balance of cerebral oxygen supply and demand.