Discussion
Taxus baccata has long been known for its lethal side effects
(1). Folklore reports that Boudica, the Celtic queen of ancient Britain
attempted suicide by ingesting the tree’s evergreen leaves, distraught
by her defeat to the Romans (7). In modern times, the tree has gained
traction amongst patients with strong suicidal intent as a readily
available toxic substance, which in overdose, has no known antidote (8).
Its lethality derives from the alkaloid toxin taxine B, which
predisposes to malignant arrhythmia by disrupting myocyte voltage gated
calcium and sodium channels (1,7,8). The malignant electrophysiological
traces seen in this case demonstrate the effect of extreme membrane
channel blockade on cardiac rhythm – agonal sinusoidal rhythms
alternating with recurrent bouts of ventricular tachycardia followed by
junctional escape rhythms.
A literature search reveals several dozen case reports of Taxus
baccata poisoning over the past two decades. Recognised treatment
options include intravenous sodium bicarbonate to correct profound
metabolic acidosis and encourage intracellular sodium transport (9);
early gastric decontamination either by emergency endoscopy or activated
charcoal; administration of intravenous Digibind as digoxin specific Fab
fragments have been found to bind taxines (10); and administration of
lipid emulsion therapy as taxine B is believed to be lipophilic (9).
In recent decades, the anti-mitotic effects of Taxus baccata have
been harnessed as chemotherapy agents – giving rise to the taxane class
of cancer treatments including medications such as paclitaxel and
docetaxel (11). Strategies for mitigating taxane-class toxicity can also
be trialled in intentional Taxus baccata poisoning (12). For
example, in this case, we also used intravenous hydrocortisone.
Other case reports have shown transient stabilising effects of varying
interventions - for example Farag et al. demonstrating conversion
of asystole to a broad complex tachycardia with administration of
Digibind (10). In our patient, we trialled all these treatments in
tandem – Digibind, lipid emulsion therapy, intravenous sodium
bicarbonate and hydrocortisone, and gastric decontamination. It is
difficult to identify a direct benefit from any one single intervention
we made. Instead, our case indicates that these treatments may form part
of a best supportive care bundle that can act as a bridge until VA-ECMO
can be commenced (2,9). It also serves as a reminder that an excellent
outcome is possible in what may seem like an unsalvageable presenting
clinical state, both biochemically and haemodynamically.
This case highlights that complete neurological and cardiovascular
recovery is possible with extensive rapid multi-specialty input and
early institution of VA-ECMO. It also supports the use of several
medications as potential temporising measures until VA-ECMO can be
established.