A client with bipolar disorder has been taking lithium, and today the client's serum lithium level is 2.0 mEq/L. What effects would the nurse expect to see?

Lithium carbonate is a mood-stabilizing salt with a very narrow therapeutic index of 0.6 to 1.2 mEq/L. It mimics sodium in the body, and levels reaching 2.0 mEq/L represent moderate toxicity, leading to severe systemic effects and potential neurological damage if the medication is not immediately discontinued. Rationale: A. The therapeutic range for lithium is 0.6 to 1.2 mEq/L, making 2.0 mEq/L a toxic concentration. The nurse must recognize that this level is significantly elevated, requiring urgent intervention to prevent life-threatening complications such as seizures or cardiovascular collapse. B. At levels of 1.5 to 2.0 mEq/L, clients typically exhibit gastrointestinal distress and CNS changes. Persistent emesis, coarse tremors, and profound confusion are hallmark signs that the lithium has reached dangerous levels in the blood, necessitating gastric lavage or diuresis. C. Fever and muscle rigidity are associated with neuroleptic malignant syndrome, not lithium toxicity. Although both conditions involve altered mental status, lithium toxicity is specifically characterized by ataxia, tinnitus, and polyuria rather than the lead-pipe rigidity seen with antipsychotics. D. Lithium toxicity usually causes diarrhea rather than constipation due to its osmotic effects in the gut. Hypotension can occur in late-stage toxicity due to dehydration, but the primary early indicators involve the worsening of initial side effects into overt toxic manifestations.