Comments on: Tricyclic antidepressant toxicity http://lifeinthefastlane.com/2009/10/toxicology-conundrum-022/ Emergency Medicine education blog Sat, 11 Feb 2012 16:17:01 +0000 hourly 1 http://wordpress.org/?v= By: Chris Nicksonhttp://lifeinthefastlane.com/2009/10/toxicology-conundrum-022/#comment-1167 Chris Nickson Sat, 07 Nov 2009 12:57:27 +0000 http://sandnsurf.medbrains.net/?p=3015#comment-1167 Thanks for the comment Rogue Medic.I agree with you in highlighting the need to intervene early. In a significant TCA overdose the patient usually goes downhill rapidly. A tachycardia in itself may be a result of the anticholininergic effects in combiination with a reflex response to the alpha blocking affects of TCAs, so NaHCO3 is not strictly indicated as it primarily targets sodium channel blockade.However, a drop in GCS (e.g. to about 12 if you need to put a number on it) means the patient should be intubated for airway protection and to facilitate hyperventilation if required for impending QRS widening. A good tip is to give an NaHCO3 bolus prior to intubation, because respiratory acidosis (resulting from absent ventilation during a rapid sequence intubation) may lead to greater ionisation of the TCA and thus greater cardiotoxicity and all round badness...Quetiapine and olanzepine are our most common drug overdoses requiring intubation and ventilation. TCAs are much less common these days but have greater lethality than the antipsychotics and other anti-depressants. Calcium channel blockers (i.e. verapamil and diltiazem) are generally regarded as even more lethal than TCAs, but are even less common - and in our neck of the woods deaths have been very rare or non-existent since the more widespread use of of high-dose insulin euglycemic therapy (HIET).... But that's another story... Thanks for the comment Rogue Medic.

I agree with you in highlighting the need to intervene early. In a significant TCA overdose the patient usually goes downhill rapidly. A tachycardia in itself may be a result of the anticholininergic effects in combiination with a reflex response to the alpha blocking affects of TCAs, so NaHCO3 is not strictly indicated as it primarily targets sodium channel blockade.

However, a drop in GCS (e.g. to about 12 if you need to put a number on it) means the patient should be intubated for airway protection and to facilitate hyperventilation if required for impending QRS widening. A good tip is to give an NaHCO3 bolus prior to intubation, because respiratory acidosis (resulting from absent ventilation during a rapid sequence intubation) may lead to greater ionisation of the TCA and thus greater cardiotoxicity and all round badness…

Quetiapine and olanzepine are our most common drug overdoses requiring intubation and ventilation. TCAs are much less common these days but have greater lethality than the antipsychotics and other anti-depressants. Calcium channel blockers (i.e. verapamil and diltiazem) are generally regarded as even more lethal than TCAs, but are even less common -- and in our neck of the woods deaths have been very rare or non-existent since the more widespread use of of high-dose insulin euglycemic therapy (HIET)…. But that’s another story…

]]> By: Rogue Medichttp://lifeinthefastlane.com/2009/10/toxicology-conundrum-022/#comment-12453 Rogue Medic Fri, 06 Nov 2009 08:19:00 +0000 http://sandnsurf.medbrains.net/?p=3015#comment-12453 I am surprised that this is such a big problem in Australia. In the US, almost everybody seems to get the SSRIs or variants of them. However, when they were more commonly prescribed, they were the overdose most likely to be successful. Part of that due to the various actions of the drugs in overdose.I was taught to intervene early. At the first observation of tachycardia related to a TCA OD. Before any widening of the QRS complex, if possible. I was under the impression that the sodium helped to prevent the delay in ventricular conduction.Now that we have waveform capnography, it is easier to observe changes in the CO2 levels and respiratory drive, since these patients tend to lose their ability to protect their airways pretty quickly, once the toxic effects start to present themselves. The bicarb won't do a thing for the level of consciousness, but it is easier to manage the level of consciousness if the vital signs are not rapidly deteriorating.It has been years since I have had a patient with a TCA OD. This is a great refresher on mechanism and treatment. I am surprised that this is such a big problem in Australia. In the US, almost everybody seems to get the SSRIs or variants of them. However, when they were more commonly prescribed, they were the overdose most likely to be successful. Part of that due to the various actions of the drugs in overdose.

I was taught to intervene early. At the first observation of tachycardia related to a TCA OD. Before any widening of the QRS complex, if possible. I was under the impression that the sodium helped to prevent the delay in ventricular conduction.

Now that we have waveform capnography, it is easier to observe changes in the CO2 levels and respiratory drive, since these patients tend to lose their ability to protect their airways pretty quickly, once the toxic effects start to present themselves. The bicarb won’t do a thing for the level of consciousness, but it is easier to manage the level of consciousness if the vital signs are not rapidly deteriorating.

It has been years since I have had a patient with a TCA OD. This is a great refresher on mechanism and treatment.

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