Salicylate overdose

This patient had ingested a large quantity of aspirin resulting in the classic findings of a salicylate overdose a centrally mediated respiratory alkalosis with a concurrent anion gap metabolic acidosis. 

Sodium bicarbonate administration for cardiac arrest is controversial because there are few clinical data supporting its use, and it may have some detrimental effects. Sodium bicarbonate can be used in special circumstances (i.e., underlying metabolic acidosis, hyperkalemia, salicylate overdose, or tricyclic antidepressant overdose). The dosage should be guided by laboratory analysis if possible. 

Direct measures (e.g., treatment of pain, hypovolemia, fever, infection, or salicylate overdose) can be effective. A rebreathing device (e.g., paper bag) can help control hyperventilation. 

Previously popular but of unproved value, forced diuresis may cause volume overload and electrolyte abnormalities and is not recommended. Renal elimination of a few toxins can be enhanced by alteration of urinary pH. For example, urinary alkalinization is useful in cases of salicylate overdose. Acidification may increase the urine concentration of drugs such as phencyclidine and amphetamines but is not advised because it may worsen renal complications from rhabdomyolysis, which often accompanies the intoxication. 

Treatment. Serial measurements of plasma salicylate are necessary to monitor the course of the overdose, for the concentration may rise over the early hours after ingestion. The general management measures described in Chapter 9 apply, but the following are relevant for salicylate overdose. 

Janssen T, Boege P, Oestreicher E, Arnold W. Tinnitus and 2fl-f2 distortion product otoacoustic emissions following salicylate overdose. J Acoust Soc Am 2000 107(3) 1790-2. 

Wrathall G, Sinclair R, Moore A, et al.Three case reports ofthe use of haemodiafiltration in the treatment of salicylate overdose. Hum Exp Toxicol. 2001 20 491 -495... 

Serum concentrations The quantitation of salicylate is important in diagnosis and treatment of salicylate overdoses and in monitoring salicylate levels to ensure appropriate therapy ... 

Patients with chronic salicylism may present with symptoms clinically similar to those seen in the acute situation. However, some patients with chronic salicylate overdose may present with CNS effects as their primary complaint, and typically have a higher morbidity and mortality than patients with acute salicylate overdose. Chronic salicylism is more often associated with pronounced hyperventilation, dehydration, pulmonary edema, renal failure, coma, seizures, and acidosis. Chronic salicylism patients will have more profound clinical effects at lower serum salicylate levels compared to patients with acute overdoses. Patients have developed toxicity with chronic salicylate serum levels as low as 15mgdl . ... 

Mention of salicylate overdose is made here, even though its popularity seems to be in decline. Its treatment, presuming hemodialysis is not indicated, includes a classic type of beneficial drug interaction that is different from that of a specific antidote (cf. A -acetylcysteine, above). Furthermore, the combination of respiratory alkalosis... 

Hydration to promote diuresis is recommended in all salicylate overdoses. Urine alkalinization is generally recommended at plasma concentrations above 600 mg 1 1 salicylate, or half that in children and the elderly. Even this, however, has its limits, and hemodialysis at salicylate concentrations of >800 mg l-1 in adults (half in children and the elderly), or regardless of plasma concentration when there are signs of CNS toxicity, is the treatment of choice. 

Renal failure with sepsis Salicylate overdose... 

Pulmonary edema has occurred occasionally with salicylate overdoses. The serum salicylate concentrations are often greater than 45 mg/dL, and the patients have other signs of toxicity, although some cases have been associated with concentrations in the usual therapeutic range. ... 

In all cases of salicylate overdose the plasma paracetamol should also be measured as many proprietary analgesics contain aspirin and paracetamol. In the early stages of paracetamol poisoning, when treatment is effective, patients will not display any specific signs or symptoms. 

Certain cases of overdosage or iJoisoning. The mechanism common to all of these is the production of acid metabolites, for example in. salicylate overdose where build-up of lactate occurs, or methanol poisoning when formate accumulates, or ethylene glycol poisoning where oxalate is formed. 

Where the two acid-base conditions arc antagonistic in the way they affect the [H. one of the disorders may mimic the compensatory response. A patient may present with a metabolic acidosis and a co-existent respiratory alkalosis, as occurs commonly in salicylate overdose. The respiratory disorder may appear, at first sight, to be simply the compensatory response. 

Alkallnizatlon is commonly used for salicylate overdose, but forced diuresis (producing urine volumes of up to 1 L/h) Is generally not used because of the risk of fluid overload. 

Wrathall Q at al Three case reports of the use of haemodiafiltration in the treatment of salicylate overdose. Hum Exp Toxicol 2001 Sep 20(9) 49l 95. [PMID 11776412] (Reduction In serum levels from 8.5 to 3.5 mmol/L over 3 hours in one case, and from 6.2 to 4 mmoi/L over 4 hours in another. The third case had oniy a modest deciine from an initiai ievei of 3 mmoi/L.)... 

Screening for salicylates Overdoses of aspirin and other mild analgesics are extremely common. Salicylate is commonly detected in urine by the classical violet iron(III)-salicylate chelate formation. 

---