The Journal of ExtraCorporeal Technology No 56-3 | Page 36

K . Kashiwa et al .: J Extra Corpor Technol 2024 , 56 , 108 – 113 111

Relationship between change in the UFH infusion rate and WBC count

ROC analysis determined the cutoff value of WBC count at 1 – 2 h after starting ECMO for discriminating the necessity of an increase in UFH infusion rate was 10.2 10 3 / lL ( sensitivity 90.0 %, specificity 58.8 %) with the AUC of 0.712 ( 95 % confidence interval 0.593 – 0.831 ). Discrimination of this cutoff value was confirmed as statistically significant by Fisher ’ s exact test ( p = 0.018 ).

Discussion

In the present study , we found a significant association between the patient ’ s ECMO WBC count and the necessity to increase UFH dosage during lung transplantation with V-A ECMO . Lower ACT was observed in the increased group from 1 to 2 h after starting ECMO , indicating that more UFH was required to maintain ACT in the target range of 160 – 200 s . No difference was observed in platelet count at any time points . On the other hand , WBC count was significantly higher in the increased group at 1 – 2 h after starting ECMO and WBC counts at other timings tended to be higher in the increased group all through the surgery ( Table 4 ). These results suggested that the WBC count or associated inflammatory status of the patient might be involved in the changes of ACT and response to the increase of UFH in V-A ECMO during lung transplantation .

Although no data for WBC fraction was available in the present study , neutrophils might be the main portion of the WBC count increase because it is well-known that neutrophils are increased during the acute phase of inflammation [ 13 ]. On the other hand , certain portions of WBC counts might contain eosinophils and basophils , which are considered not to be dominant in the situation of acute insults such as surgery [ 14 – 17 ]. As shown in the results , this can be also inferred from the high percentage of a fraction of neutrophils and low percentage of a fraction of eosinophils and basophils immediately after lung transplantation . In cardiac surgery using cardiopulmonary bypass , it has been reported that neutrophil elastase concentration increases during cardiopulmonary bypass [ 18 – 20 ]. There is another report showing an increase in neutrophil elastase during ECMO [ 21 ]. When neutrophil elastase and other substances were increased with neutrophil activation , they promote tissue factor- and factor VII-dependent coagulation reactions and inhibit the activity of tissue factor pathway inhibitors [ 22 ]. Taken together , it is plausible that in some patients , an increase in neutrophils during lung transplantation using VA-ECMO accompanies neutrophil elastase , influencing ACT and the requirement for UFH dosage .

In the present study , there was no difference in patients ’ preoperative characteristics and lung disease between the increased group and the non-increased group . However , it is presumed that inflammatory response had already been enhanced preoperatively in some patients because CRP and albumin in the increased group tended to be higher and lower than the non-increased group , respectively . Besides , because some of the patients were treated with long-term immunosuppression before lung transplantation , inflammatory reactions in such patients including WBC recruitment to the peripheral

Table 5 . Comparison of blood transfusion volume . PRBC ( units ) FFP ( units ) Platelets ( units ) p value

Non-increased group p value Increased group

Non-increased group p value Increased group Increased group Non-increased group

Volume of 1 unit is about 140, 120 , and 10 ml of PRBC , FFP , and Platelets , respectively in Japan .