呼气末正压对不同血容量状态猪颅高压模型颅内压和脑氧代谢影响的实验研究

目的观察不同血容量状态下颅高压的急性呼吸窘迫综合征(ARDS)猪模型,增加呼气末正压(PEEP)后,其血流动力学状态、颅内压(ICP)及脑氧分压(PtiO2)的变化。方法选取雄性14~16月龄巴马小型猪12头,随机数字表法随机分成低血容量组和正常血容量组。建立ARDS和颅高压模型。自5 cmH2O(1 cmH2O=0.098 kPa)水平逐步增加PEEP 5 cmH2O,直至25 cmH2O。采用重复测量的方差分析,并应用Sidak法进行多重比较和P值的校正。结果随着PEEP逐渐增加,正常血容量组ICP逐渐升高,而低血容量组ICP逐渐下降;当PEEP在5、10、15 cmH2O时,两组间ICP值分别为(25.83±1.47)mmHg(1 mmHg=0.133 kPa)比(27.00±1.63)mmHg、(27.33±1.75)mmHg比(27.67±2.21)mmHg、(28.83±1.72)mmHg比(27.5±2.06)mmHg,差异均无统计学意义(t=0.793、0.227、0.906,P值均>0.05);当PEEP在20、25 cmH2O时,两组间ICP值分别为(31.33±2.07)mmHg比(26.5±3.35)mmHg、(31.67±2.94)mmHg比(25.83±3.67)mmHg,差异均有统计学意义(t=3.284、3.964,P值均<0.01)。随着PEEP逐渐增加,两组PtiO2均逐渐下降,其中低血容量组下降更明显;在各PEEP水平时,两组间PtiO2值分别为(19.83±2.64)mmHg比(14.33±3.50)mmHg、(18.67±2.50)mmHg比(12.33±3.88)mmHg、(17.67±3.88)mmHg比(10.67±3.88)mmHg、(15.33±2.34)mmHg比(9.17±3.54)mmHg、(13.67±3.61)mmHg比(6.67±2.73)mmHg,差异均有统计学意义(t=2.333、3.319、3.668、3.231、3.668,P值均<0.05)。结论PEEP对血流动力学、颅内压、脑代谢作用受不同容量状态的影响。低血容量状态下,PEEP逐渐上升,其心输出量、血压和PtiO2下降更明显。

Effects of positive end-expiratory pressure on intracranial pressure and cerebral oxygen metabolism in cranial hypertension pig model with different blood volume status

Objective To study the changes of hemodynamic status,intracranial pressure and cerebral oxygen metabolism in acute respiratory distress syndrome(ARDS)pig models of cranial hypertension with different blood volume status,before and after increasing positive end-expiratory pressure(PEEP).Methods A total of 12 male adult Bama miniature pigs,which were purchased from Beijing Real Genesis Company,were randomly divided into two groups:low blood volume group and normal blood volume group.To induce ARDS,0.1 mol/L hydrochloride solution(4 ml/kg)was instilled.An intracranial water balloon was used to establish intracranial hypertension.The initial PEEP was 5 cmH2O(1 cmH2O=0.098 kPa)and was gradually increase by 5 cmH2O each time until 25 cmH2O.Repeated measures analysis of variance was used,and the Sidak method was used for multiple comparisons between different PEEP levels and correction of P values.Results With the gradual increase of PEEP,the ICP of the normal blood volume group gradually increased,and the ICP of the hypovolemia group gradually decreased.When PEEP were 5,10,15 cmH2O,the ICP of the two groups were(25.83±1.47)mmHg(1 mmHg=0.133 kPa)vs.(27.00±1.63)mmHg,(27.33±1.75)mmHg vs.(27.67±2.21)mmHg,(28.83±1.72)mmHg vs.(27.50±2.06)mmHg,with no statistical difference(t=0.793,0.227,0.906,P>0.05).When PEEP were 20 cmH2O and 25 cmH2O,the ICP of the two groups were(31.33±2.07)mmHg vs.(26.50±3.35)mmHg and(31.67±2.94)mmHg vs.(25.83±3.67)mmHg,respectively,showing statistical differences(t=3.284,3.964,P<0.01).As PEEP gradually increased,PtiO2 in both groups decreased gradually,with the hypovolemia group decreasing more significantly.At each PEEP level,the PtiO2 between the two groups were(19.83±2.64)mmHg vs.(14.33±3.50)mmHg,(18.67±2.50)mmHg vs.(12.33±3.88)mmHg,(17.67±3.88)mmHg vs.(10.67±3.88)mmHg,(15.33±2.34)mmHg vs.(9.17±3.54)mmHg,(13.67±3.61)mmHg vs.(6.67±2.73)mmHg,all with statistical difference(t=2.333,3.319,3.668,3.231,3.668,all P<0.05).Conclusion The effects of PEEP on hemodynamics,intracranial pressure,and brain metabolism are affected by different volume states.In the state of hypovolemia,as PEEP gradually increases,its cardiac output,blood pressure and PtiO2 decreased more significantly.