A 58-year-old man with a 45-pack-year smoking history comes to the clinic due to a persistent cough. The cough started about 3 months ago and is distinctly worse than his usual smoker's cough. During this period, he had episodes of hemoptysis and lost 9.1 kg (20 lb). He has had no nausea, vomiting, fever, chills, night sweats, pruritus, seizures, or gait abnormalities. Temperature is 36.9 C (98.4 F), blood pressure is 134/85 mm Hg without an orthostatic drop, and pulse is 76/min. Temporal wasting is evident. The mucous membranes are moist, and the neck is supple without lymphadenopathy. Heart and breath sounds are normal. The abdomen is soft and nontender. No peripheral edema is present. The patient is oriented to time, place, and person. Pupils are equal and reactive, and no nystagmus is elicited. Neurologic examination, including gait, is normal. Laboratory results are as follows: Which of the following is the best initial treatment for this patient?

Question

A 58-year-old man with a 45-pack-year smoking history comes to the clinic due to a persistent cough.  The cough started about 3 months ago and is distinctly worse than his usual smoker's cough.  During this period, he had episodes of hemoptysis and lost 9.1 kg (20 lb).  He has had no nausea, vomiting, fever, chills, night sweats, pruritus, seizures, or gait abnormalities.  Temperature is 36.9 C (98.4 F), blood pressure is 134/85 mm Hg without an orthostatic drop, and pulse is 76/min.  Temporal wasting is evident.  The mucous membranes are moist, and the neck is supple without lymphadenopathy.  Heart and breath sounds are normal.  The abdomen is soft and nontender.  No peripheral edema is present.  The patient is oriented to time, place, and person.  Pupils are equal and reactive, and no nystagmus is elicited.  Neurologic examination, including gait, is normal.  Laboratory results are as follows:  Which of the following is the best initial treatment for this patient?

Quizplus · Accepted Answer

11ec25c8_d10c_8ca0_bc81_a3142f1679e4_MD0003_00 This patient, who has a history of extensive smoking, cough, hemoptysis, weight loss, and temporal wasting, likely has lung cancer. His laboratory results are remarkable for hyponatremia (serum sodium <135 mEq/L). One approach to determining the etiology of hyponatremia is an assessment of the patient's volume status. Evidence of volume overload (eg, peripheral edema, jugular venous distension) is consistent with hypervolemic hyponatremia, which occurs in heart failure, renal failure, and liver cirrhosis. Evidence of volume depletion (eg, dry mucous membranes) suggests hypovolemic hyponatremia, which occurs in patients with dehydration. This patient appears clinically euvolemic (eg, moist mucous membranes, absence of peripheral edema), which is characteristic of hyponatremia due to the syndrome of inappropriate antidiuretic hormone secretion (SIADH). Small cell lung cancer is strongly associated with smoking and is the most common cause of SIADH due to ectopic release of antidiuretic hormone. This patient requires workup for probable small cell lung cancer. In the meantime, fluid restriction (<800 mL/day) is the best initial treatment for patients with asymptomatic or mildly symptomatic (eg, lethargy, nausea, forgetfulness) hyponatremia due to SIADH. Salt tablets are sometimes given as well. (Choice A) Intravenous albumin may provide some benefit in the management of hypervolemic hyponatremia in patients with cirrhosis. However, it is not useful in the management of SIADH, even in those who are hypoalbuminemic, such as this patient. (Choice B) Demeclocycline acts at the level of the renal collecting tubule to decrease responsiveness to antidiuretic hormone. It is sometimes used in the treatment of SIADH; however, it can be nephrotoxic and should be considered only if fluid restriction and high salt intake fail to correct the hyponatremia. (Choice D) Use of hypertonic saline can be dangerous due to the risk of sodium overcorrection; it should be reserved for severe symptomatic hyponatremia (eg, seizures, coma, profound confusion) or cases of hyponatremia that are resistant to other treatment. (Choices E and G) Both lactated Ringer solution and normal saline are forms of isotonic fluid. Infusion of isotonic fluid is appropriate for hypovolemic patients; however, it often results in net free water retention and worsening of hyponatremia in those with SIADH. (Choice F) Further intervention is required as this patient's hyponatremia is likely to worsen without fluid restriction. Educational objective: Hyponatremia due to the syndrome of inappropriate antidiuretic hormone secretion is a common complication of small cell lung cancer. Fluid restriction is the initial treatment of choice in asymptomatic or mildly symptomatic patients. References: Diagnosing and treating the syndrome of inappropriate antidiuretic hormone secretion. (http://www.ncbi.nlm.nih.gov/pubmed/26584969) Paraneoplastic syndromes associated with lung cancer. (http://www.ncbi.nlm.nih.gov/pubmed/25114839)

A 58-Year-Old Man with a 45-Pack-Year Smoking History Comes to the Clinic