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.