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Correspondence |
Brigham and Women’s Hospital, Harvard Medical School, Boston, USA, E-mail: mharnett{at}partners.org
To the Editor:
A 35-yr-old parturient with factor VII deficiency presented at term with a factor VII level of less than 3%. Coagulation studies revealed a prothrombin time (PT) of 32.3 sec, international normalized ratio (INR) of 3.2, partial thromboplastin time (PTT) of 30.3 sec and hematocrit (Hct) of 37.2%. Two units of fresh frozen plasma (FFP) were transfused prior to epidural placement. A follow-up set of coagulation studies revealed a PT of 22.9 sec, INR of 2.0 and PTT of 30.3 sec. Thromboelastography® analysis revealed no difference in her coagulation status as compared to that prior to administration of FFP with the R-value remaining unchanged from 4.8 min [pre FFP: R = 4.8 min, measure of speed of clot strengthening (K) = 1.0 min, angle = 74.6°, measure of maximum strength of developed clot (MA) = 69.5 mm and post FFP: R = 4.8 min, K = 1.2 min, angle = 72.2°, MA = 67.7 mm]. Cesarean section was performed 16 hr later for failure of progression of labour at which time coagulation studies revealed an INR of 2.7 prompting administration of four units of FFP. The estimated blood loss was 1200 mL; her postoperative PT was 20.0 sec, INR 1.7 and Hct 21.2%.
One year later she had an elective repeat Cesarean section, at which time her factor VII level was less than 1%. Her preoperative coagulation studies revealed a PT of 36.2 sec, INR of 3.5, PTT of 30.4 sec and Hct of 34.4%. A 30 ·g·kg–1 dose of rFVIIa (Novo Nordisk A/S, Denmark) was administered intravenously over five minutes and a repeat set of coagulation studies 15 min later revealed a PT of 13.4 sec, INR of 1.0 and PTT of 30.3 sec. Thromboelastography® analysis at this time showed a marked reduction in the R-value from 5.6 min to 3.2 min post administration rFVIIa. (pre rFVIIa: R = 5.6 min, K = 1.4 min, angle = 71.2°, MA = 67.3 mm and post rFVIIa: R = 3.2 min, K = 0.8 min, angle = 77.9°, MA = 72.7 mm). Cesarean section was performed under spinal anesthesia; the estimated blood loss was 500 mL and postoperative Hct 24.7%.
Traditionally FFP has been used prophylactically to lessen the risk of peripartum hemorrhage in those factor VII deficient pregnant women. However, the speed of onset and administration (iv over five minutes) of rFVIIa is an obvious advantage in the setting of emergent Cesarean delivery. Since it is not derived from human plasma the risk of transmission of blood borne pathogens is eliminated. Despite these advantages there are still many unanswered questions regarding its use in the clinical setting, with thrombosis being the primary adverse effect of concern to clinicians.
In a recent editorial the authors alluded to the issue of monitoring the efficacy of rFVIIa and in particular to the prevention of thrombosis. They mentioned that though the effect on PT, PTT, and factor VII clotting activity is marked with administration of rFVIIa this does not always translate into clinically improved blood coagulation. They suggested that TEG® analysis, which measures whole blood coagulation, as a possible promising technique.1
We compared the efficacy of FFP vs rFVIIa in a parturient with congenital factor VII deficiency using TEG® analysis. We showed that a single infusion of 30 ·g·kg–1 of rFVIIa in this patient prior to Cesarean section normalized the PT and INR and decreased the R-value from 5.6 min to 3.2 min. This demonstrates that in this setting rFVIIa is effective in achieving normalization of coagulation without placing the R-value in the prothrombotic range. Further studies are required to study the dose response effect of rFVIIa on the TEG® coagulation profile, particularly the R-value. These studies may help provide information on the dose of rFVIIa required to normalize the coagulation status without inducing a detrimental prothrombotic state.
Footnotes
Accepted for publication January 5, 2006.
Reference
1 Spahn DR, Tucci MA, Makris M. Is recombinant FVIIa the magic bullet in the treatment of major bleeding? (Editorial). Br J Anaesth 2005; 94: 553–5.
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