Biology Reference
In-Depth Information
decision to give replacement therapy is therefore a balancing act between competing
adverse outcomes. There is no clear formula to maintain the patient (or the physi-
cian) safely on the highwire.
Replacement therapy has often included repeated blood transfusions or infusions
of PRBCs (Blaylock, 1960; Kono and Sawai, 1975; Nakayama et al., 1973;
Table
4.1
). Repeated transfusions are frequently necessary in these cases due to the marked
anemia that develops in most patients envenomed by these species because of mas-
sive and continuing intravascular hemolysis (Section 4.3;
Table 4.1
). Some of these
cases report provision of large volumes of PRBCs or blood. For example, Mather
et al. (1978) transfused 10 units each of whole blood, platelets, FFP, and 4.2 g of
fibrinogen for a patient envenomed by a
R. subminiatus
. In another case of
R. sub-
miniatus
envenoming, Cable et al. (1984) gave 11 units of PRBCs, 12 units of FFP,
and 3 units of plasma. These authors discontinued attempts to replenish clotting fac-
tors, but continued PRBCs infusions in order to maintain a normal hematocrit (Cable
et al., 1984). In a serious case of
T. capensis
envenoming, Beiran and Currie (1967)
provided 6 units of whole blood with a positive outcome. Similarly, Du Toit (1980)
gave 5 units of fresh blood and 3 units of FFP in a life-threatening case of
D. typus
envenomation. Clearly, transfusion should be dictated by clinical need, bearing
in mind the increasing recognition of the potential danger of all blood products.
24
Patients with significant anemia must be given blood and/or PRBCs sufficient to
maintain an acceptable hematocrit. The physician must remain aware of the risk of
venom-induced intravascular hemolysis and related hemoglobinuric nephropathy.
Therefore, hematocrit should be maintained just below or at the low normal range
unless a patient's individual comorbidities dictate otherwise.
FFP and Cryoprecipitate
As described previously, FFP and/or cryoprecipitate are commonly given in the man-
agement of envenomation by hazard level 1 species (
Tables 4.1 and 4.3
). The pri-
mary basis for infusion of plasma or plasma products is the restoration of clotting
factors. A secondary benefit is increasing circulating volume. Treatment of coagulo-
pathic envenoming with replacement therapy comprised of FFP, cryoprecipitate, and/
or specific clotting factors has remained controversial since the late 1980s (Burgess
and Dart, 1991; White, 2005). One limited low-powered study reported no evi-
dence of efficacy of FFP in treatment of
Pseudonaja affinis
(dugite) coagulopathic
envenomation in the canine model (Jelinek et al., 2005). Consumptive coagulopathy
induced by white-lipped pit viper,
Cryptelytrops
(
Trimeresurus
)
albolabris
enven-
omation was refractory to FFP therapy (Yang et al., 2007). However, Isbister et al.
(2009) reported that early (within 4 h postenvenomation) administration of FFP may
shorten the time to recovery from Australian elapid snakebite-induced coagulopathy,
24
Any patient receiving blood products must be counseled, and consented, about the aforementioned
risks as well as the risk of exposure to blood-borne pathogens (HIV, hepatitis B and C, etc.), leukocyte
“ghost”(disrupted leukocyte membranes)-induced febrile episodes, and Type IV hypersensitivity reac-
tions. Although the risks of blood-borne pathogens have been substantially lowered in most “First World”
countries, it remains a serious concern in countries with limited facilities for plasma screening.
