A 66-year-old hospitalized man is evaluated after an episode of generalized tonic-clonic seizure. The patient has no previous history of seizure. He underwent right hemicolectomy for cecal adenocarcinoma the previous day. Postoperatively, the patient had hypotensive episodes, which responded to fluid resuscitation. He has been receiving intravenous infusion of 5% dextrose with 0.45% saline. He is also receiving morphine via a patient-controlled device. On physical examination, he is postictal. Temperature is 36.7 C (98 F), blood pressure is 112/60 mm Hg, pulse is 68/min, and respirations are 12/min. Pulse oximetry shows 96% on room air. Laboratory results are as follows: Which of the following is the most appropriate next step in management of this patient?

Question

A 66-year-old hospitalized man is evaluated after an episode of generalized tonic-clonic seizure.  The patient has no previous history of seizure.  He underwent right hemicolectomy for cecal adenocarcinoma the previous day.  Postoperatively, the patient had hypotensive episodes, which responded to fluid resuscitation.  He has been receiving intravenous infusion of 5% dextrose with 0.45% saline.  He is also receiving morphine via a patient-controlled device.  On physical examination, he is postictal.  Temperature is 36.7 C (98 F), blood pressure is 112/60 mm Hg, pulse is 68/min, and respirations are 12/min.  Pulse oximetry shows 96% on room air.  Laboratory results are as follows:  Which of the following is the most appropriate next step in management of this patient?

Quizplus · Accepted Answer

Explanation: 11ec2b69_c096_2b47_8f63_53ae6c536d87_MD0005_00 This patient has developed severe hyponatremia, most likely due to the syndrome of inappropriate antidiuretic hormone secretion (SIADH). Postoperative SIADH is common due to prominent nonosmotic stimuli for ADH secretion (eg, pain, nausea, physical and emotional stress). The resulting hyponatremia can be worsened by postoperative administration of intravenous fluids (eg, 5% dextrose with 0.45% saline), which, in the setting of SIADH, can lead to further water retention. nonosmotic stimuli The symptoms of SIADH depend on the degree of hyponatremia and the rate at which it occurred. Patients with serum sodium of 130-135 mEq/L are usually asymptomatic, and those with slowly developing hyponatremia with serum sodium of 120-130 mEq/L may be asymptomatic or display only mild symptoms (eg, lethargy, forgetfulness). However, rapid decreases (within <48 hours) in serum sodium concentration can lead to large fluid shifts and severe symptoms (eg, profound confusion, seizures, coma). The tonic-clonic seizure in this patient with severe hyponatremia (eg, serum sodium <120 mEq/L) suggests the development of cerebral edema and an associated risk of brainstem herniation. Such patients require an urgent increase in their serum sodium concentration, which is best accomplished with the administration of hypertonic (3%) saline. (Choice A) Fluid restriction is appropriate management in asymptomatic patients with SIADH or those with only mild symptoms. However, this patient with severe symptoms (eg, seizure) is at risk for rapid neurologic deterioration and death, and should be treated with hypertonic saline to correct the hyponatremia. (Choices C and E) Both lactated Ringer solution and normal saline are forms of isotonic fluid. Infusion of isotonic fluid is appropriate for patients who are hypovolemic with hyponatremia; however, it can result in net free water retention and worsening hyponatremia in those with SIADH (who are characteristically euvolemic). (Choice D) Naloxone is an opiate receptor antagonist used to reverse the effects of opiate overdose (eg, morphine). Patients with opiate (or opioid) overdose typically present with somnolence and depressed respiratory rate, but seizures are not typical. Educational objective: Patients with the syndrome of inappropriate antidiuretic hormone secretion who are asymptomatic or have mild symptoms usually respond to fluid restriction. Patients with severe symptoms are at high risk of rapid neurologic deterioration and death and require treatment with hypertonic (3%) saline. References: The treatment of hyponatremia. (http://www.ncbi.nlm.nih.gov/pubmed/19523575) Diagnosing and treating the syndrome of inappropriate antidiuretic hormone secretion. (http://www.ncbi.nlm.nih.gov/pubmed/26584969)

A 66-Year-Old Hospitalized Man Is Evaluated After an Episode of Generalized