questions 6

Hyponatremia vs. Hypernatremia

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Topic updated on 02/23/17 2:27pm

HYPOnatremia HYPERnatremia
  • A 17-year-old schizophrenic patient presents with new onset of seizures. He has a history of psychogenic polydipsia.
  • A 32-year-old woman with Cushings disease presents with mental status changes and lethargy.
Introduction
  • Serum sodium < 135 mEq/L 
  • Causes include
    • copious bladder irrigation
    • TURP - transurethral resection of the prostate
    • high output ileostomy
    • adrenal insufficiency
    • psychogenic polydipsia 
      • associated with schizophrenia
    • volume depletion 
  • Serusodium > 145 mEq/L
  • Causes include
    • fluid loss
    • steroid use
    • hypertonic fluids
Presentation
  • Symptoms
    • asymptomatic
    • nausea
    • vomiting
    • confusion
    • muscle cramps
    • lethargy
  • Can progress to (Na < 115 mEq/L)
    • seizures
    • status epilepticus
    • coma
  • Symptoms
    • lethargy
    • weakness
    • irritability
  • Can progress to
    • seizures
    • coma
Treatment
  • Mild hyponatremia
    • water restriction
  • Moderate/severe hyponatremia
    • hypertonic saline IV
    • loop diuretics + normal saline
    • ADH blockers (conivaptan, tolvaptan)
  • Chronic SIADH
    • demeclocycline
      • can induce nephrogenic diabetes insipidus
    • ADH blockers
  • Normal saline IV 
  • Correct half deficit in first 24 hrs
  • Correct second half of deficit over next 2-3 days
  • Switch to 0.45% (half-normal) saline after volume deficit is corrected 
  • Nephrogenic diabetes insipidus
    • no response to DDAVP administration
    • treat with correction of underlying cause + thiazides
  • Central diabetes insipidus
    • treat with DDAVP
Prognosis, Prevention, and Complications
  • Central pontine myelinolysis
    • occurs if replace sodium to fast
    • raise serum levels < 12-15 mEq/day
    • characterized by:
      • paraparesis
      • quadraparesis
      • dysarthia
      • dysphagia
      • coma
  •  Seizures
    • in response to hypernatremia, brain makes idiopathic osmolytes to maintain fluid balance
    • this equalizes the osmotic pull keeping the volume of cells constant
    • sudden correction of hypernatremia causes cerebral edema and swelling → seizures


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Qbank (6 Questions)

TAG
(M3.RL.75) A 92-year-old female with CAD, hypertension, atrial fibrillation, hyperlipidemia, and type II diabetes is brought to the emergency room from her nursing home due to altered mental status. The patient had been confused and lethargic for one day prior to her arrival in the hospital. While being examined by the emergency room physician, the patient has a seizure. Physical examination reveals decreased deep tendon reflexes symmetrically. Jugular venous pressure is normal, mucous membranes are moist, and no edema is present in the patient’s extremities. CT scan of the head is shown in Figure A. Laboratory studies reveal the following:

Sodium: 115 mEq/L
Potassium: 4.5 mEq/L
Chloride: 86 mEq/L
Bicarbonate: 16 mEq/L
BUN: 41 mg/dL
Creatinine: 2.09 mg/dL
Glucose: 213 mg/dL

Urine studies show:
Urine sodium: <10 mEq/dL
Urine osmolality: 75mOsm/kg
Urine creatinine: 14 mg/dL

Which of the following is the most likely cause of the patient’s neurological symptoms?
Topic Review Topic
FIGURES: A          

1. Poor solute intake
2. Syndrome of inappropriate anti-diuretic hormone secretion (SIADH)
3. Cerebrovascular accident
4. Congestive heart failure
5. Intrinsic renal azotemia

PREFERRED RESPONSE ▶
TAG
(M3.RL.76) A 68-year-old woman is brought to the emergency room by her husband following confusion and lethargy of a week’s duration. Two weeks ago she was diagnosed with small cell cancer of the lung but has not yet begun any chemotherapy regimens. She has a 30-pack year history of smoking. She does not take medications. Physical examination reveals decreased deep tendon reflexes symmetrically. Jugular venous pressure is normal, mucous membranes are moist, and no edema is present in the patient’s extremities. CT scan of the brain reveals no abnormalities. Laboratory studies reveal the following:

Sodium: 112 mEq/L
Potassium: 4.0 mEq/L
Chloride: 95 mEq/L
Bicarbonate: 24 mEq/L
BUN: 6 mg/dL
Creatinine: 0.65 mg/dL

Serum osmolality is 220 mOsm/kg and urine osmolality is 400 mOsm/kg. Which of the following is the most appropriate next step in management of this patient:
Topic Review Topic

1. Volume repletion with normal saline
2. Administer demeclocycline
3. Administer hypertonic saline
4. Administer desmopressin (dDAVP)
5. Administer 5% dextrose in water (D5W) and furosemide

PREFERRED RESPONSE ▶
TAG
(M2.RL.6) You are the medical doctor on call at an inpatient psychiatric facility, where you are asked to see a 38-year-old woman who has been hospitalized for the past 4 days. She has a history of schizophrenia and was admitted after assaulting a passenger on the public transit service. The psychiatric team has been titrating her antipsychotics, and she has been relatively well during her stay thus far. You learn from the orderly that she has been experiencing nausea and malaise now for 24 hours. Currently, she is complaining of headache and weakness and appears confused. On exam, she appears euvolemic. While awaiting preliminary blood test results, you perform a urine dipstick which shows the following:

Specific gravity: 1.001
pH: 5.9
Protein: negative
Leukocyte esterase: negative
Nitrites: negative
Blood: negative
Ketones: negative

Her serum sodium returns at 121 mEq/L. Urine osmolality is 90 mOsm/kg. Which of the following is the most likely diagnosis? Topic Review Topic

1. Renal tubular acidosis (RTA)
2. Medication side effect
3. Psychogenic polydipsia
4. Acute renal failure
5. Central diabetes insipidus (DI)

PREFERRED RESPONSE ▶
TAG
(M2.RL.38) A 70 year-old man is brought to the emergency department by his daughter due to lethargy and change in mental status. His daughter states he was recently diagnosed with Alzheimer's disease and had to move in with her family to help with his activities of daily living. The patient has not had any fevers, chills, coughing, or changes in urination or stool. He has no other medical problems and takes no medications. Vital signs include Temp 36.9 C, BP 104/68 mmHg, HR 100/min, and RR 16/min. After standing for 10 minutes, his blood pressure is 82/58 mmHg. On physical exam, he is a frail, elderly man with dry oral mucosa. He is oriented to person only. His skin examination is shown in Figure A. Cardiac and pulmonary auscultation are within normal limits.

Laboratory results are as follows:
sodium 165 mEq/L
potassium 4.8 mEq/L
bicarbonate 30 mEq/L
chloride 124 mEq/L

The patient is started on IV 0.9% normal saline. Twenty-four hours later, his blood pressure is 120/74 mmHg sitting and 118/72 mm Hg after standing for 10 minutes. He is still rather lethargic but is now oriented to person and place. He now has moist mucous membranes and normal skin turgor.

His post-resuscitation labs are as follows:
sodium 156 mEq/L
potassium 4.2 mEq/L
bicarbonate 24 mEq/L
chloride 112 mEq/L

What is the best next step in the management of this patient? Topic Review Topic
FIGURES: A          

1. Continue IV 0.9% saline
2. Switch to IV 0.45% saline
3. Switch to oral free water
4. Switch to IV free water
5. Discharge the patient

PREFERRED RESPONSE ▶
TAG
(M2.RL.48) A 74-year-old man is brought to the emergency department from a nursing home due to decreased responsiveness. His caretaker adds that the patient has not been having fevers, chills, coughing, or changes in urination or stool. The patient's past medical history is significant for Alzheimer's disease, hypercholesterolemia, and hypertension. His medications include memantine, simvastatin, and hydrochlorothiazide. Vitals include T is 36.9 C, BP 104/68 mmHg, HR 100/min, and RR 16/min. After standing for 10 minutes, his blood pressure is 82/58 mmHg. On physical exam, he is a frail, elderly man, with dry oral mucosa. His skin examination is shown in Figure A. Cardiac exam reveals regular tachycardia and pulmonary auscultation is wiithin normal limits . Laboratory results are as follows:

Sodium 165 mEq/L, potassium 4.8 mEq/L, bicarbonate 30 mEq/L, chloride 124 mEq/L.

What is the best first step in the management of this patient? Topic Review Topic
FIGURES: A          

1. IV 0.45% saline
2. IV 5% dextrose in 0.45% saline
3. IV 0.9% saline
4. IV 5% dextrose in water (D5W)
5. Oral free water

PREFERRED RESPONSE ▶
TAG
(M2.RL.50) A 78 year-old woman is brought to the emergency department by her maid, who found her lethargic and less responsive than usual this morning. The maid had been on vacation for the last week and reports that the woman was alert and active previously. The patient has a past medical history of hypertension and early dementia, and her medications include metoprolol and memantine. Her temperature is 36.8 C, blood pressure 94/60 mmHg, heart rate 96/min, and respiratory rate 16/min. Her blood pressure decreases to 84/50 mmHg while standing. She is lethargic and oriented to person and place only. She has dry oral mucosa and decreased skin turgor. Her heart, lung, and abdominal exams are within normal limits and stool guaiac is negative. Initial labs are as follows:
Sodium 124 mEq/L, potassium 3.4 mEq/L, chloride 95 mEq/L, bicarbonate 31 mEq/L, BUN 28 mg/dL, creatinine 1.0 mg/dL, and glucose 120 mg/dL.
Which of the following best describes the levels of renin, aldosterone, and ADH in this patient's blood? Topic Review Topic

1. Decreased renin, decreased aldosterone, increased ADH
2. Decreased renin, increased aldosterone, increased ADH
3. Increased renin, increased aldosterone, decreased ADH
4. Increased renin, increased aldosterone, increased ADH
5. Increased renin, decreased aldosterone, decreased ADH

PREFERRED RESPONSE ▶

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