Analytic role in clinical toxicology--impact on the diagnosis and treatment of a poisoned patient

Abstract

The measurement of plasma or urine levels of drugs or toxins at an appropriate time after ingestion and assessment of the clinical status can have a significant impact in the clinical management of a poisoned patient. Qualitative screening of blood and urine is helpful in identifying ingested toxins, whereas quantitative analyses are useful in determining appropriate therapy with selected toxins (e.g., salicylate, paraquat, and acetaminophen). The common analgesic acetaminophen, which is available without prescription, is a potential hepatotoxin on overdose. The most widely accepted approach to determine the risk of hepatotoxicity following acute, single ingestion is to plot the plasma acetaminophen concentration on the Rumack-Matthew nomogram. This nomogram is based on a series of patients with and without hepatotoxicity and their corresponding blood levels. Antidotal treatment should be administered to any patient with a plasma level in the potentially toxic range. As an aid in the diagnosis and treatment of toxic incidents, as well as in monitoring the effectiveness of treatment regimens, an analytical approach is useful to clearly identify the nature of the toxic exposure and measure the amount of the toxic substance which has been absorbed. A cardinal rule in the treatment of poisoning cases is to remove any unabsorbed material, limit the absorption of additional poison, and hasten its elimination. The laboratory serves an additional purpose in the treatment phase by monitoring the amount of toxic agent remaining in circulation or measuring that excreted.