Management of Lithium Intoxication

Management of Lithium Intoxication Jonathan R. Sugarman, MD Seattle, Washington Lithium toxicity is usually insidious in onset and presents with a wide spectrum of clinical symptoms. Symptoms vary from mild lethargy to seizures and coma. Although mild to moderate intoxication can be managed with intravenous saline, cases not responding or severe cases should be treated by hemodialysis. Iatrogenic fluid and electrolyte disorders often complicate therapy. Although lithium is widely acknowledged to be attentive and uncooperative, but arousable. an effective and specific therapy for bipolar affec Weight was 160 pounds (down 8.5 pounds from tive disorder (manic-depressive illness), its thera Vh weeks previously). Vital signs were normal, peutic index is notoriously low. The onset of lith without orthostatic pulse rise or hypotension. ium toxicity is often insidious, and mild clinical Pertinent findings on physical examination were symptoms can belie potentially lethal serum lith restricted to the neurological system. Neurological ium levels. The following case report describes examination revealed appropriate orientation, a typical episode of lithium intoxication and dem poor short-term recall, and inconsistent responses onstrates several pitfalls that may be encountered to spoken instructions. Bilateral dysmetria was in the management of lithium poisoning. present on the finger to nose test; gait was broad based and ataxic. The deep tendon reflexes were Case Report 4+ with ankle clonus. A mild resting tremor was A 33-year-old woman with the diagnoses of present. manic-depressive illness and borderline personal Initial laboratory examination revealed a serum ity disorder presented to the Family Medical Cen lithium level of 4.02 mEq/L (therapeutic range 0.7 ter (FMC) complaining of intermittent nausea, to 1.2 mEq/L) sodium 137 mEq/L, potassium 4.2 vomiting, and fatigue of approximately two weeks' mEq/L, chloride 104 mEq/L, CO-2 27 mEq/L, duration, with increasing vomiting and weakness blood urea nitrogen (BUN) 25 mg/dL, and creati the previous two days. She had been on lithium nine 1.5 mg/dL. Urinalysis showed moderate carbonate (LiCO:i) for two years; the dose was in ketones, 2+ protein, and a specific gravity of creased from 600 mg twice a day to 600 mg three 1.009. The electrocardiogram (ECG) revealed times a day by the consulting psychiatrist four normal sinus rhythm at a rate of 65 beats/min, with months previously. She had been seen in the FMC PR = 0.20, QRS = 0.06, and QT = 0.4. U waves twice during the preceding two weeks, at which were present. times her symptoms of increasing depression and The patient was admitted to the hospital with lassitude were attributed to recent stressful events continuous cardiac monitoring and treated initially in her life. She denied intentional overdose, and a with intravenous normal saline, 1 L at 200 mL/h pill count was consistent with medication intake as followed by normal saline at 150 mL/h. Serum lith instructed. Medical history was remarkable for re ium nine hours after admission was 3.16 mEq/L. cent musculoskeletal pain treated with zomepirac. On the second hospital day, serum sodium was 155 During the physical examination she was in- mEq/L, thought to be related to inappropriate fluid restriction and high urine output (6,950 mL in and From the Department of Family Medicine, School of Medi 7,650 mL out in the first 24 hours). Electrolytes cine, RF-30, University of Washington, Seattle, Washing ton. Requests for reprints should be addressed to Dr. and creatinine improved in response to infusion of Jonathan Sugarman, Department of Family Medicine, free water. Serum lithium was 1.9 mEq/L 24 hours RF-30, School of Medicine, University of Washington, Se attle, WA 98195. after admission. © 1984 Appleton-Century-Crofts 237 THE JOURNAL OF FAMILY PRACTICE, VOL. 18, NO. 2: 237-239, 1984 LITHIUM INTOXICATION Thirty hours after admission the patient suf Management fered a generalized tonic-clonic seizure lasting five When confronted with a patient in whom lith minutes. Serum chemistries obtained shortly after ium poisoning is suspected, the usual clinical the seizure revealed a sodium of 147 mEq/L, po strategy in toxicology applies curtail intake ot tassium of 3.1 mEq/L, BUN of 3 mg/dL, and the offending agent, and encourage elimination creatinine of 0.5 mg/dL. Urine output was 10 L in the preceding 24 hours. An electroencephalogram of the poison through the most expedient means revealed a markedly abnormal pattern with general available. After a complete history and physical examina ized spikes and waves in a multifocal distribution, consistent with metabolic encephalopathy. The tion, the initial laboratory examination should in clude a serum lithium level, serum electrolytes, patient was treated with phenytoin. The diagnosis of nephrogenic diabetes insipidus BUN, creatinine, complete blood count, and uri was made on the basis of inappropriately low urine nalysis. In many situations, serum and urine toxi osmolality with respect to serum osmolality in the cologic screenings will be appropriate. Although setting of lithium intoxication. Urine output de there is no specific electrolyte abnormality asso creased appropriately with conservative manage ciated with lithium intoxication, Hansen and Am ment. On the 15th hospital day the patient was disen3 identified either hypernatremia or hypona discharged on phenytoin with improving polyuria, tremia in approximately one half of their patients, normal electrolytes, and return to her baseline and one fourth were hypokalemic. The value of psychological and neurological status. the serum lithium is obvious, although it must be emphasized that levels within the normal range may be associated with clinical toxicity, especially Clinical Setting of Lithium Intoxication in the acute overdose.5 In addition, response of The symptoms of lithium intoxication are di serum lithium to initial therapy is a crucial guide verse and range from mild nausea and lassitude to to appropriate management (see below). The uri convulsions and coma.1 Even authors who have nalysis should include evaluation of osmolality, as attempted to correlate specific levels of serum it provides a clue to the presence of significant lithium with an orderly progression of symptoms nephrogenic diabetes insipidus if inappropriately from mild to severe acknowledge that serum lith low compared with serum osmolality. ium may not be an accurate predictor of clinical Although cardiac morbidity is seldom clinically symptoms.2 Most workers agree that early lithium significant, most patients demonstrate abnormal intoxication is almost uniformly accompanied by electrocardiograms, primarily manifested by ST nonspecific neurological and psychological symp depression and inverted T waves. Nevertheless, toms such as weakness, tremor, restlessness, occasional case reports describe atrioventricular apathy, and muscular rigidity.3 Thus the attribu block, ventricular and supraventricular arrhyth tion of even subtle changes in mental status and mias, and, rarely, myocardial infarction, albeit central nervous system function to adverse psy usually in patients with concurrent medical ill chosocial events should be made only with great ness.6 Continuous cardiac monitoring is therefore caution in patients on lithium therapy. advisable. Hansen and Amdisen,3 in their superb literature Special attention should be directed toward dis review and report of 23 cases of lithium intoxica continuation of chronic medications that decrease tion, commented on the usual evolution of lithium lithium excretion. Hydrochlorthiazide decreases poisoning. Twenty-one of their 23 patients were on lithium clearance and is contraindicated in poison a stable lithium maintenance dose for months to ing. Similarly, prostaglandin inhibitors such as in- years; only one ingested an intentional overdose. domethacin and other nonsteroidal anti-inflamma Conditions affecting fluid and electrolyte balance, tory drugs may also inhibit maximal renal such as gastroenteritis, diuretic treatment, vomit clearance of lithium.7 The temptation to place ing from any cause, dietary intake low in sodium, hypertensive patients on a low-sodium diet should and decreased fluid intake, commonly precede in be resisted, as it is well known that such diets toxication. Other recent reviews1'3’4 provide more impair the excretion of lithium.8 detailed explication of the clinical presentation of The clinician must be prepared to accept some lithium intoxication. empiricism in the management of lithium toxicity 238 THE JOURNAL OF FAMILY PRACTICE, VOL. 18, NO. 2, 1984 LITHIUM INTOXICATION because no randomized controlled prospective after 30 hours of treatment if dialysis is to be studies to determine optimal therapy have been avoided. Regardless of which mode of therapy is performed. Therefore, what follows is a distilla chosen, scrupulous attention must be directed tion of recommendations from current workers in toward preventing iatrogenic fluid and electrolyte the field. imbalance. Over 98 percent of ingested lithium is excreted The case presented above might have been in the urine,9 and after emptying the stomach of managed differently. The prescription of zomepi- unabsorbed tablets, increasing the elimination of rac for mild musculoskeletal pain may have con lithium through the urine is the first step in ther tributed to an elevation of the serum lithium level. apy. Unfortunately, no one method consistently It is likely that

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