The Journal of ExtraCorporeal Technology No 58-1 | Page 68

62 M. Raguindin et al.: J Extra Corpor Technol 2026, 58, 57--64

Table 8. Post-group COVID-19 subgroup analysis.

circuit thrombosis in the pre-group( 89.5 % vs. 68.6 %, p = 0.027). The most common site of circuit thrombosis was the oxygenator.

COVID-19 subgroup analysis

Additional analysis was completed for select endpoints in the post-group comparing the nine COVID-19 patients to the 26 patients without COVID-19( Table 8). Renal failure was significantly more common in the COVID-19 subgroup, with all patients developing renal failure during ECMO compared to 65.4 % of those without COVID-19. The time to two consecutive aPTTs within the goal range was significantly longer in patients with COVID-19 by 18 h( 26.5 vs. 8.6 h, p = 0.018), although the median bivalirudin dose at which the therapeutic aPTT was achieved was not significantly different between groups. Additionally, there was a wide range of therapeutic bivalirudin doses for COVID-19 patients( 0.025--0.2 mg / kg / h).

Discussion

With the growing use of bivalirudin for ECMO anticoagulation and the subsequent implementation of a pharmacistdirected ECMO-specific bivalirudin protocol at our institution, this study found that the median time to two consecutive aPTTs within goal range was 8.9 h. This was not statistically different from the time of 14.2 h prior to the protocol implementation, although both studies had small sample sizes of less than 40 patients. Patients with renal failure required a median of two dose adjustments, while patients without renal failure required a median of one adjustment. Although the differences between groups were not statistically significant, a median time of around 9 h to achieve a therapeutic aPTT is clinically appropriate, and we concluded that the starting dose ranges in our current protocol are reasonable. It took less than 14.1 h to achieve our primary endpoint of time to two consecutive therapeutic aPTTs in 75 % of the patients, and only three patients without COVID-19 took greater than 24 h to achieve our primary endpoint. These findings are consistent with those of Netley and colleagues, who reported in a retrospective review of their dosing protocol that all 11 patients were within the aPTT target range within 24 h [ 10 ].

Patients in the post-group, excluding those with COVID-19, had a low rate of 9.1 % of aPTTs out of range after two initial consecutive therapeutic aPTTs. This demonstrated high consistency of aPTTs maintained within goal range and suggests that subsequent monitoring can be reduced to once daily to decrease unnecessary use of resources, including personnel time and physical supplies from phlebotomy, pharmacy, and the laboratory, due to the collection of fewer aPTTs. Rates of aPTTs out of range were reported at 14.3 % by Kaseer and colleagues and 33.7 % by Netley and colleagues, although our definition differed in that we reported the consistency of aPTTs maintained within goal range once it was initially achieved [ 8, 10 ]. Ten patients were excluded from the primary analysis due to not meeting the endpoint of two consecutive therapeutic aPTTs within the initial goal range; while this may have influenced the findings, it also reflects the clinical complexity of ECMO patients. Therapeutic bivalirudin doses in this study were similar to those used by Ranucci and colleagues, although, as noted by Sanfilippo and colleagues, differences in anticoagulation monitoring and goal ranges in studies make direct comparisons in therapeutic bivalirudin rates difficult [ 7, 9 ]. Mortality on ECMO and survival to hospital discharge were similar to rates seen with other studies [ 7, 8 ].

About one-third of patients in the post-group had a major bleed. However, this was mostly due to a decrease in hemoglobin of 2 g / dL or more as compared to requiring transfusion of PRBCs, and only two patients required surgical intervention, possibly indicating a lower bleed severity. Major bleeding rates in the post-group in this study were similar to those found by Kaseer and colleagues when considering the definition included a hemoglobin drop of at least 3 g / dL [ 8 ]. While systemic VTE occurrence was low and not different between groups, there was over 20 % less circuit thrombosis in the post-group, despite a significant portion having COVID-19, which has previously been documented as a pro-thrombotic disease [ 11 ]. When comparing aPTT goals, the pre-group had lower aPTT goal ranges, which may account for the lower incidence of circuit thrombosis in the post-group. Additionally, 40 % of patients in the postgroup were already receiving full anticoagulation prior to ECMO, which may have contributed to a reduction in circuit thrombosis in the post-group as well. Circuit thrombosis rates, although lower in our post-group than pre-group, remained higher than those reported in other studies [ 6, 8 ]. The higher rate may be due to differing definitions, as one study defined circuit thrombosis as a thrombus requiring a change in ECMO cannula, tubing, pump, and / or oxygenator. Of note, only five patients in the post-group required oxygenator change. Our assessment of circuit thrombus was also based on reports of visual thrombus from nursing notes, an endpoint which was consistent with the previously collected data from the pregroup.