Clinical Study On Pulse Pressure Variation-directed Intraoperative Fluid Therapy

The evaluation of circulatory blood volume plays an important role during perioperative period. Accurate evaluation 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 central venous pressure and pulmonary artery wedge pressure, which have been proved poor indices as to reflect circulatory blood volume. PPV is one of the functional hemodynamic parameters, which turn out to be better predictors in terms of fluid responsiveness compared to routine indices(CVP, PCWP and LVEDV). Monitoring of PPV requires complex devices and considerable expenditure, which confine its broad clinical usefulness. A simple way to assess PPV on Datex Ohmeda S/5 monitor has been used to predict volume responsiveness.IDBG is a new indice to predict volume status which reflect CO directly. However, the consistency with PPV in terms of volume evaluation needs further research.Apart from the evaluation of blood volume, the result of volume therapy is also still a matter of controversies. Gastrointestinal patients in the perioperative period are often subjected to hypotension and relatively hypovolemia mainly caused by long duration of surgery, hemorrhage, third space loss, preoperative fast and bowl preparation. Fluid infusion requirement is obviously increased in order to maintain adequate circulatory volume. However, fluid overload will result in tissue edema, impaired gastrointestinal function and delayed recovery of anastomosis. Restrictive fluid therapy may have advantages, but extreme restriction may impair hymodynamic status and organ perfusion. Further investigation to evaluate the outcome of different fluid therapy is required.Part I The consistency of PPV and IDVG in assessing volume statusObjective:IDVG (Initial Volume of Distribution of Glucose) is proved to be a sensitive index in assessing volume status. PPV (pulse pressure variation) can accurately predict responsiveness of patients under mechanical ventilation to volume load. In that case, PPV can also be applied in assessing patients'volume status. Our objective is to observe whether there's a consistency between IDVG and PPV.Methods:Thirty ASA classificationⅠ-Ⅱpatients undergoing selective neurosurgery were enrolled. Patients who have diabetes, cardiac arrhythmia or BMI≥30 kg/m2 were excluded. Volume expanding is not applied before induction. Induction was performed by TIVA and mechanical ventilation was applied after tracheal intubation. Invasive artery monitoring is set up through radial artery, and central vein catheterization is performed through right jugular vein. HR, MAP, CVP and PPV were obtained from Ohmeda S/5 monitor.5g glucose (50% glucose solution 10ml) was injected through right jugular vein in 30s. Blood glucose levels in 1,3,5 mins after the injection was assayed via radial artery blood samples, and IDVG in 1,3,5min were further calculated. Blood glucose levels before and 60 mins after glucose injection were also assayed. The correlation analysis between PPV and IDVG in predicting fluid volume status was performed. The correlation analysis between PPV or IDVG and CVP was also made.Results:There's no difference in blood glucose level before and 60mins after the glucose injection (TO:5.39±0.66VS T60:5.31±0.59, P>0.1);We found a negative correlation between PPV and IDVG 3 mins after glucose injection(r=-0.65, P<0.001);CVP is irrelevant to PPV or IDVG (P>0.1).Conclusion:There's a negative correlation between PPV and IDVG in assessing fluid volume state.Part II Influence of intraoperative fluid therapy on recovery of postoperative gastrointestinal function:goal-directed fluid therapy VS restrictive fluid therapyObjective:To assess the effects of goal-directed or restrictive fluid therapy on recovery of postoperative gastrointestinal function.Methods:sixty ASA I or II patients undergoing elective gastrointestinal surgery were randomly divided into three groups(n=20 each):GD-RL group(goal-directed Ringer lactate group), GD-C(goal-directed colloid), R-RL(restricted Ringer lactate). The target parameter in GD-RL and GD-C groups was PPV with threshold of 10%. The baseline values were determined after induction during stable hemodynamic state. And then, HR, MAP, CVP and PPV were recorded every 15 mins. The GD-RL group (n =20)received 4 mL/kg per hour of RL and intermittent boluses of 250mL of RL to maintain PPV<10%. The GD-C group (n=20) received 4mL/kg per hour of RL and boluses of 250 mL of 6% hydroxyethyl starch (130/0.4) to maintain PPV<10%. The R-RL group (n=20) received 4 mL/kg per hour of RL throughout the perioperative period. Vasoactive drugs (ephedrine and phenylephrine)were used according to individual hemodynamic status and the amount and frequency of vasoactive drugs use were recorded. Duration of surgery, total fluid infusion, blood loss, urine output and the amount of drugs were recorded at the end of surgery. The values of serum albumin, creatinine and hematocrit were recorded in the first day postoperatively. Flatus time, postoperative complications and length of hospital stay were recorded.Results:Total volumes of fluid administered and urine output in GD-RL group were significantly higher than that in other groups(Total volumes of fluid administered, GD-RL:2109.50±474.25ml vs GD-C:1742.50±333.01ml VS R-RL:1260.00±269.44ml, P<0.01; urine output, GD-RL:485.00±93.33ml vs GD-C:295.00±48.40ml vs R-RL:277.50±63.82ml, P<0.01). The amount of vasoactive drugs in GD-C group was reduced when compared with other groups(phenylephrine, GD-C:76.00±38.73ug vs GD-RL:156.00±85.99ug vs R-RL:195.00±26.66ug, P<0.01; ephedrine, GD-C:7.25±3.73mg vs GD-RL:14.50±7.24mg vs R-RL:16.50±5.16mg, P<0.01). Flatus time and length of hospital stay in GD-C group was reduced as compared to GD-RL and R-RL groups(flatus time, GD-C:86.20±7.17h vs R-RL:92.10±9.72h vs GD-RL:95.40±9.14h, P<0.01; days of hospital stay, GD-C:9.10±1.37d vs R-RL:10.95±1.23d vs GD-RL:11.95±1.15d, P<0.01). No significant difference was found in Postoperative complications among three groups(P >0.05). Conclusion:In gastrointestinal surgery, PPV-directed colloid administration may improve recovery of postoperative gastrointestinal function and reduce length of hospital stay.