The Safety And Efficiency Of Low Central Venous Pressure In Patients During Spine Surgery

Objective:To investigate the effects of low central venous pressure (LCVP) on hemodynamics, oxygen metabolism and bleeding volume of patients undergoing spine surgery. To analysis the safety and efficiency of LCVP applied in spine surgery.Methods:36patients scheduled for spine surgery were randomized divided into LCVP group (n=18) and control group (n=18).The CVP of LCVP group was maintained in2～4cmH2O by restrict fluid infusion and nitroglycerin injection.CVP was returned to normal range after hemostasis. While control group was performed routinely with normal CVP between5～12cmH2O. Hemodynamic and oxygen metabolism parameters were recorded after induction of anesthesia (T0,supine position),before LCVP (T1, prone position),30min after LCVP (T2),60min after LCVP(T3),90min after LCVP(T4) and immediately after surgery(T5). Hemoglobin, hematocrit, blood loss and transfusion of each group were measured. Analyze the correlation between CVP/MAP and blood loss of every patients during LCVP.Results:CVP of both group increased when changing from supine position (T0) to prone position (T1) after induction of anesthesia (p<0.05). During the period of LCVP(T2、T3、T4), systemic vascular resistance index (SVRI) of LCVP group were significantly higher than control group (p<0.05), while intrathoracic blood volume index(ITBVI)of LCVP group were lower than control group(p<0.05). No significant changes were found in extravascular lung water index (EVLWI) and pulmonary vascular permeability index (PVPI) in comparison between and within two groups(p>0.05). The volume of blood loss and blood transfusion in LCVP group were significantly less than that of control group (p<0.01).Hb and Hct of both group decreased after surgry (p<0.05), and LCVP group were slightly lower than control group (p<0.05).There were positive correlation between CVP and blood loss, and between MAP and blood loss during LCVP (respectively r=0.634and r=0.664)(p<0.001). The percentage of blood transfusion of LCVP group is higher than control group (p<0.01) during T4-T5, while the percentage of blood transfusion of control group is higher than LCVP group in others periods (p<0.01).Conclusion:1. When CVP maintained in2～4cmH2O, ITBVI of patients decreased significantly, SVRI rised as neural-humoral regulation to maintain MAP. EVLWI and PVPI of patients have not change during the rehydration, indicating that quick volume resuscitation will not increase the risk of pulmonary edema in patients. 2. Patients maintained the state of physiologic oxygen dependencies during LCVP, compensated DO2I reduce by improving ERO2, which maintained the balance of oxygen suppliment and demand.3. LCVP could not only reduce the blood loss in patients undergoing spine surgery, but also impact the timing of blood transfusion and reduce the waste of blood products.