Letters to the Editor
Norwalk Precipitates Severe Lithium Toxicity
Dear Editor:
Despite 50 years of medical experience with lithium, lithium toxicity remains a significant and primarily iatrogenic health problem (1). The efficacy of lithium is marred by a narrow therapeutic index and significant potential toxicity (2). Lithium toxicity can occur by overdose (intentional or accidental) or, more commonly, from alteration in its clearance by the kidneys. We present a case of lithium toxicity in an elderly patient subsequent to a “Norwalk virus–like” infection, wherein delay in making the correct diagnosis led to unnecessary suffering and prolonged hospitalization.
Case Report
The patient is a 75-year-old woman with a long history of bipolar illness and dementia, living in a retirement home. She was brought to our outpatient clinic for her routine quarterly follow-up, but this time, she was comatose. All attempts to rouse her failed. Her lips were dry and cracking. The person who accompanied her knew nothing about her condition and had been contracted to provide transportation only. The note accompanying her indicated that she had had a “Norwalk-like virus 6 days ago for about 2 days” and that she had become lethargic since then. She had continued to receive the same dosage of lithium. Laboratory tests performed 48 hours prior to her presentation at the outpatient clinic revealed a serum lithium level of 1.85 mmol/L, an elevated white blood cell count of 29.5, absolute neutrophils of 16.8, and absolute band of 8.6. A rapid clinical assessment revealed that the patient was in a state of medical emergency. We referred her to the emergency room (ER) of the local general hospital, where further testing revealed an elevated sodium of 164 mmol/L, blood urea nitrogen of 15.7 mmol/L, and raised liver function tests. She was admitted to the hospital and treated aggressively for dehydration and lithium toxicity. Lithium was discontinued, and intravenous fluids were adminstered, along with supportive care. Her hospitalization lasted for 9 days, and she fully recovered.
Discussion
We describe this case to increase physicians’ awareness of a common cause of lithium toxicity; specifically, gastro- intestinal disturbance in which fluid intake is limited by illness. Initial concern led to the request to monitor her serum lithium level and complete blood count; it would have been prudent to withhold lithium treatment until the blood levels were obtained and her condition stabilized. The clinical deterioration of this patient, who became dehydrated and comatose, suggested an urgent need to acquire her blood chemistry, which should have led to urgent and appropriate referral. The finding of abnormal blood results should also have alerted the lab to report the results by telephone to her treating physician. We present this case to enhance physicians’ awareness of the possible effects of nausea, vomiting, and diarrhea on lithium excretion and to remind physicians to be vigilant when fluid intake is limited by supervening illness. Severe lithium toxicity can result, especially in the elderly and medically compromised patients (3). In such cases, lithium should be withheld, an urgent lithium level report obtained, rehydration with supportive care initiated, and the patient transferred to the ER if lithium level is elevated.
References
1. Oakley PW, Whyte IM, Carter GL. Lithium toxicity: an iatrogenic problem in susceptible individuals. Aust N Z J Psychiatry 2001;35:833–40.
2. Okusa MD, Crystal JJ. Clinical manifestation and management of acute lithium intoxication. Am J Med 1994;97:383–9.
3. Meltzer E, Steinlauf S. The clinical manifestation of lithium intoxication. Isr Med Assoc J 2002;4:265–7.
G Abraham, MD, FRCPC
F Voutsilakos, MD, FRCPC
Kingston, Ontario
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