HYDROXOCOBALAMIN (vitamin B12A), a precursor to cyanocobalamin, is United States Food and Drug Administration-approved
for treating cyanide toxicity. In published case series and small retrospective cohort
studies, it has been used off-label for refractory shock due to catecholamine-resistant
vasoplegia in various populations.
Reproduced with permission from BTG International Inc.
1
,
2
,
3
,
4
,
5
The proposed mechanism behind using hydroxocobalamin for vasoplegia is its ability
to scavenge nitric oxide and hydrogen sulfide, thereby attenuating profound vasodilation
in inflammation.
6
,7
Hydroxocobalamin is deep red in color and is known to cause interference with numerous
laboratory parameters, including those using cooximetry, clot-based coagulation methods,
and, particularly, colorimetric tests.
8
,
9
,
10
In terms of coagulation parameters, there are known effects of hydroxocobalamin on
activated partial thromboplastin time (aPTT), prothrombin time (PT) and international
normalized ratio (Table 1), but there are scarce reports of its effect on the anti-Xa assay, a chromogenic
test frequently used for unfractionated heparin infusion monitoring.
9
,11
Here, the authors report a case of undetectable anti-Xa levels in a heparinized patient
who received hydroxocobalamin for refractory shock while on mechanical circulatory
support (MCS).
Table 1Laboratory Interference Observed With In Vitro Samples of Hydroxocobalamin
| Laboratory Parameter | No Interference Observed | Artificially Increased | Artificially Decreased | Unpredictable | Duration of Interference |
|---|---|---|---|---|---|
| Clinical chemistry |
|
|
|
|
24 h with the exception of bilirubin (up to 4 d) |
| Hematology |
|
|
12-16 h | ||
| Coagulation |
|
24-48 h | |||
| Urinalysis |
|
pH (with equivalent doses of <5 g) | 48 h up to 8 d; color changes may persist up to 28 d |
NOTE. Analyzers used: ACL Futura (Instrumentation Laboratory), AxSYM/Architect (Abbott),
BM Coasys110 (Boehringer Mannheim), CellDyn 3700 (Abbott), Clinitek 500 (Bayer), Cobas
Integra 700, 400 (Roche), Gen-S Coultronics, Hitachi 917, STA Compact, Vitros 950
(Ortho Diagnostics).
Abbreviations: ALT, alanine transaminase; AST, aspartate transaminase; aPTT, activated
partial thromboplastin time; CK, creatine kinase; GGT, gamma-glutamyltransferase;
INR, international normalized ratio; LDH, lactate dehydrogenase; MCH, mean corpuscular
hemoglobin; MCHC, mean corpuscular hemoglobin content; MCV, mean corpuscular volume;
PT, prothrombin.
† ≥10% interference observed on at least 1 analyzer.
Key Words
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Publication history
Published online: February 28, 2023
Publication stage
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