Background

Blood lactate is a strong predictor of mortality, and repeated blood lactate assays are recommended during surgery in high-risk patients. We hypothesized that the use of intravascular microdialysis incorporated in a central venous catheter would be interchangeable with the reference blood gas technique to monitor changes in blood lactate.

Methods

Microdialysis and central venous blood lactate measurements were recorded simultaneously in high-risk cardiac surgical patients. The correlation between absolute values was determined by linear regression, and the Bland–Altman test for repeated measurements was used to compare bias, precision, and limits of agreement. Changes in lactate measurements were evaluated with a four-quadrant plot and trend interchangeability method (TIM).

Results

In the 23 patients analysed, the central venous catheter was used as part of standard care, with no complications. The correlation coefficient for absolute values (n=104) was 0.96 (P<0.0001). The bias, precision, and limits of agreement were −0.19, 0.51, and −1.20 to 0.82 mmol litre⁻¹, respectively. The concordance rate for changes in blood lactate measurements (n=80) was 94% with the four-quadrant plot. In contrast, the TIM showed that 23 (29) changes in lactate measurements were not interpretable, and among the remaining 57 (71) interpretable changes, 18 (32) were interchangeable, 8 (14) were in the grey zone, and 31 (54) were not interchangeable.

Conclusions

Microdialysis with a central venous catheter appears to provide reliable absolute blood lactate values. Although changes in blood lactate measurements showed an excellent concordance rate, changes between the two methods were poorly interchangeable with the TIM.

Clinical trial registration

NCT02296593.

中文翻译：

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趋势互换性方法评估高危心脏手术中血管内微透析中乳酸浓度的变化

背景

血乳酸是死亡率的重要指标，在高危患者的手术过程中，建议重复进行血乳酸测定。我们假设在中央静脉导管中使用血管内微透析可与参考血气技术互换，以监测血液中乳酸的变化。

方法

在高危心脏外科手术患者中同时记录了微透析和乳酸中枢静脉血的测量。绝对值之间的相关性是通过线性回归确定的，重复测量的Bland–Altman检验用于比较偏差，精度和一致性极限。用四象限图和趋势互换性方法（TIM）评估乳酸测量值的变化。

结果

在分析的23例患者中，中心静脉导管用作标准护理的一部分，无并发症。绝对值（n = 104）的相关系数为0.96（P <0.0001）。偏差，精确度和一致性极限分别为-0.19、0.51和-1.20至0.82 mmol升^-1。用四象限图测得的血乳酸测量变化的一致性率为n = 80（94％）。相比之下，TIM显示乳酸测量值中的23（29）个变化是无法解释的，其余57（71）个可解释的变化中，有18（32）个是可互换的，有8（14）是在灰色区域，而31（ 54）不可互换。

结论

用中央静脉导管进行微透析似乎可提供可靠的绝对血液乳酸值。尽管血乳酸测量值的变化显示出极高的一致性率，但两种方法之间的变化与TIM的互换性很差。

临床试验注册

NCT02296593。