WBR1127

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Author [[PageAuthor::Pratik Bahekar, MBBS [1]]]
Exam Type ExamType::USMLE Step 2 CK
Main Category
Sub Category
Prompt [[Prompt::62-year-old man has been hearing voices from 2 weeks. The voices have instructed him to rob a bank and send money to Queen Elizabeth of England,as she is getting old. He believes that he was a British soldier in a past life. He was diagnosed with schizophrenia and admitted to a hospital. Because of agitation, nursing staff decided to have a 24 hour sitter. Several weeks after the patient's admission, he developed polyuria, vomiting, diarrhea, and restlessness but his temperature is normal. His medication includes haloperidol, zolpidem PRN, Olanzepine at bedtime, and B complex vitamins. What is the most likely reason behind his recent changes in the health condition?]]
Answer A AnswerA::Dilutional hyponatremia
Answer A Explanation [[AnswerAExp::Antipsychotics can cause SIADH, which is commonly observed in schizophrenic patients. SIADH results in dilutional hyponatremia. There appears to be no correlation with dose of antipsychotics and it can occur in the absence of polydipsia. Antipsychotics can cause non-osmolar stimuli for ADH release. Long term use of antipsychotic drug results in increased sensitivity of D2 receptors secondary to their prolonged blockade which causes an increase in ADH levels. In some patients antipsychotics enhance the ADH action on the kidney. Dilutional hyponatremia manifests as:

Most patients with chronic water intoxication are asymptomatic, but may have symptom related to the underlying cause. Severe hyponatremia may cause osmotic shift of water from the plasma into the brain cell. Typical symptoms include nausea, vomiting, headache and malaise. As the hyponatremia worsens, confusion, diminished reflex, convulsion, stupor or coma may occur. Since nausea is, itself, a stimulus for the release of ADH, which promotes the retention of water, a positive feedback loop may be created and the potential for a vicious circle of hyponatremia and its symptoms exists.]]

Answer B AnswerB::Anxiety disoder
Answer B Explanation AnswerBExp::The patient does not show signs of anxiety disorder.
Answer C AnswerC::Malignant hyperthermia
Answer C Explanation [[AnswerCExp::The patient does not have an elevated temperature. 1994 consensus conference led to the formulation of a set of diagnostic criteria. The higher the score (above 6), the more likely a reaction constituted MH:
  • Respiratory acidosis (end-tidal CO2 above 55 mmHg or arterial pCO2 above 60 mgHg)
  • Heart involvement (unexplained sinus tachycardia, ventricular tachycardia or ventricular fibrillation)
  • Metabolic acidosis (base excess lower than -8, pH<7.25)
  • Muscle rigidity (generalized rigidity including severe masseter muscle rigidity)
  • Muscle breakdown (CK >20,000/L units, cola colored urine or excess myoglobin in urine or serum, potassium above 6 mmol/l)
  • Temperature increase (rapidly increasing temperature, T >38.8°C)
  • Other (rapid reversal of MH signs with dantrolene, elevated resting serum CK levels)
  • Family history (autosomal dominant pattern)]]
Answer D AnswerD::Serotonin syndrome
Answer D Explanation [[AnswerDExp::Haloperidol, Zolpidem, and Olanzepine do not cause serotonin syndrome when given togther. The symptoms of serotonin syndrome are often described as a clinical triad of abnormalities:
Answer E AnswerE::Depression
Answer E Explanation [[AnswerEExp::This patient is not showing any sign of depression. Clinical depression can present with a variety of symptoms, but almost all patients display a marked change in mood, a deep feeling of sadness, and anhedonia. Other symptoms include:
  • Persistent sad, anxious or "empty" mood
  • Loss of appetite and/or weight loss or conversely overeating and weight gain
  • Insomnia, early morning awakening, or oversleeping
  • Restlessness or irritability
  • Psychomotor agitation or psychomotor retardation
  • Feelings of worthlessness, inappropriate guilt, helplessness
  • Feelings of hopelessness, pessimism
  • Difficulty thinking, concentrating, remembering or making decisions
  • Thoughts of death or suicide or attempts at suicide
  • Loss of interest or pleasure in hobbies and activities that were once enjoyed
  • Withdrawal from social situations, family and friends
  • Decreased energy, fatigue, feeling "slowed down" or sluggish
  • Persistent physical symptoms that do not respond to treatment, such as headaches, digestive problems, and chronic pain]]
Right Answer RightAnswer::A
Explanation [[Explanation::Antipsychotics can cause SIADH resulting in the dilutional hyponatremia.

Educational Objective: Antipsychotics can cause SIADH, which is commonly observed in schizophrenic patients. SIADH results in dilutional hyponatremia.
References: http://www.ncbi.nlm.nih.gov/pubmed/20082537 http://www.wikidoc.org/index.php/Clinical_depression_history_and_symptoms http://www.wikidoc.org/index.php/Serotonin_syndrome http://www.wikidoc.org/index.php/Hyponatremia_history_and_symptoms http://www.wikidoc.org/index.php/Malignant_hyperthermia]]

Approved Approved::No
Keyword WBRKeyword::SIADH, WBRKeyword::Antipsychotic
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