When dealing with poisonings it is necessary to establish whether ingestion was accidental or deliberate.
In my experience, deliberate ingestion is usually done by people wanting to committ suicide and sometimes, unfortunately, they succeed despite medical intervention.
When investigating an ingestion, one needs to establish the drug/s or toxin/s ingested, their dose or quantity and the time at which these agents were taken e.g. at the same time or staggered over hours or days.
In the UK, most overdose patients use acetaminophen which effects can take up to 48-72 hours before signs of acute liver failure ensue. Sometimes aspirin is also ingested and some of such overdoses are done under the influence of alcohol, which can worsen matters due to the combined toxic effects of such ingestions.
Hence, it is quite usual and proper to examine blood for these above agents even if the patient denies taking them or as part of an overall drug screen in the intoxicated patient. Tricyclic agents can also be tested for, as can urinary amphetamines / cannabinoids.
It is of prime importance to check for the above agents as treatment is available to reverse the associated problems caused in the early stages of ingestion.
For example, acetaminophen ingestion can be treated with iv n-acetylcysteine or oral methionone to reduce hepatotoxicity and renal injury and forced alkaline diuresis for aspirin overdose respectively. Activated charcoal can bind the tricyclic antidepressant agents plus many other drugs which can be inactivated by this method.
One very real example I saw and eluded to yesterday in my blog was of a female patient of 30 years old that I saw in the UK who presented with an overdose of Ethylene Glycol (EG) and alcohol. She presented with a decreased conscious level and her family had found an empty bottle of the EG around her plus it was noted she had been drinking Gin.
On admission her vital signs were stable, but conscious level was GCS reduced with the patient not eye opening, confused words and withdrawal to pain (E1 V4 M4 =9/15), pupils were 4mm each but unreactive. Reflexes were generally absent except for the triceps bilaterally. Babinski sign was uninterpretable.
Chest and abdominal examinations were normal.
Blood gas showed a pH of 7.1, pCO2 14, HCO3 3.8, BE -25, pO2 98.
Anion Gap 26
BUN normal. Creatinine 1.2, Na 134, K 7.0
Corrected Calcium for Albumin = 8.6
Liver function Normal.
WCC 28.8 but other blood elements normal.
Urine analysis - normal. No blood / protein / casts
With the Anion Gap being > 25 and a profound acidosis with a very low HCO3 <8,> methanol or ethylene glycol. Hence the blood results fitted with the history. However, the severe side effects of these agents are blindness or renal failure respectively.
The patient was given rehydration and bicarbonate and therapy for hyperkalaemia (see blog of yesterday)
By morning, her GCS had improved and she was able to open her eyes on command, follow commands and answer questions appopriately (GCS 14/15).
On reviewing the patient, it appeared that left flank pain was a new problem and the renal failure was now becoming worse with a rising BUN and creatinine. The K had normalised to 3.5. Calcium was still with normal limits.
It was suggested that the patient be given the Alcohol Dehydrogenase Inhibitor Fomepizole or iv alcohol to slow down the break down of the ethylene glycol. The former drug has a much better treatment profile and is easier to control with few side effects rather than the undesired effects of alcohol.
Moreover, the patient was given mulitvitamins such as folate, Vit B1 and Vit B12.
The concern about this patients kidneys made me concerned about ensuing renal failure from the formation of Calcium oxolate and other byproducts, which is the by product of EG breakdown through binding of free calcium.
Hence, when a patient is admitted poisoning, history can be extremely helpful although with a semi-comatosed patient such history will need to be taken from family or friends. Inviting such bystanders in to obtain information can provide a wealth of information and such people will feel that they have been empowered by the medical team and feel respected, and they are less likely to complain about YOU for the fact that they have been kept appraised of the information.
Physical examination may not be very helpful in these cases.
However, basic blood tests including an ABG, drug levels of common poisonous drugs plus blood chemistry can point the physician in the right direction.
One of the best texts I have found to date is UpToDate (www.uptodate.com) which is a paid subscription service to the most up to date of medical information including poisonings.
I would highly recommend this service.
All the best!