A 2-year-old boy was hospitalized 24 hours ago after a swimming pool drowning. The patient had no pulse when he was removed from the pool. Cardiopulmonary resuscitation was initiated at the scene and continued for 20 minutes before spontaneous circulation was restored. The patient is intubated and receiving mechanical ventilation. Over the past 2 hours, he has had persistently elevated blood pressure and bradycardia. Temperature is 37 C (98.6 F), blood pressure is 145/84 mm Hg, pulse is 59/min, and respirations are 16/min. Oxygen saturation is 96% on 70% oxygen, with the ventilator rate set at 16/min. The patient is not receiving any sedating or analgesic medications and exhibits no eye or extremity movement in response to stimulation. Jugular venous pressure is normal. The lungs have bilateral crackles. There is no peripheral edema. What is the most likely explanation for this patient's hemodynamic abnormalities?

Question

A 2-year-old boy was hospitalized 24 hours ago after a swimming pool drowning.  The patient had no pulse when he was removed from the pool.  Cardiopulmonary resuscitation was initiated at the scene and continued for 20 minutes before spontaneous circulation was restored.  The patient is intubated and receiving mechanical ventilation.  Over the past 2 hours, he has had persistently elevated blood pressure and bradycardia.  Temperature is 37 C (98.6 F), blood pressure is 145/84 mm Hg, pulse is 59/min, and respirations are 16/min.  Oxygen saturation is 96% on 70% oxygen, with the ventilator rate set at 16/min.  The patient is not receiving any sedating or analgesic medications and exhibits no eye or extremity movement in response to stimulation.  Jugular venous pressure is normal.  The lungs have bilateral crackles.  There is no peripheral edema.  What is the most likely explanation for this patient's hemodynamic abnormalities?

Quizplus · Accepted Answer

Explanation: This patient who drowned has evidence of hypoxic-ischemic brain injury (eg, no response to painful stimuli in the absence of sedation) accompanied by hypertension and bradycardia. This presentation is concerning for severely increased intracranial pressure (ICP). Hypoxic-ischemic brain injury (as occurs with drowning and cardiac arrest) can cause neuronal cell death within minutes. Widespread neuronal necrosis then leads to cerebral edema, which increases ICP and compresses small arterioles, decreasing cerebral blood flow. The classic hemodynamic response to acutely increased ICP (ie, Cushing reflex) attempts to restore cerebral perfusion and consists of the following: Hypertension: the sympathetic nervous system is activated to increase systemic blood pressure to maintain cerebral perfusion pressure (mean arterial pressure − ICP = cerebral perfusion pressure). Bradycardia: hypertension may stimulate baroreceptors in the carotid artery and aortic arch, triggering a parasympathetic response that induces bradycardia. When accompanied by irregular respirations, which occur due to impaired brainstem function and may be masked in mechanically ventilated patients, this is called the Cushing triad. Cushing triad is a poor prognostic sign and often indicates cerebral herniation is imminent. (Choice A) Neurogenic shock can occur with cervical spinal cord injury. However, patients have bradycardia with hypotension (vs hypertension) due to injury of descending sympathetic pathways, resulting in decreased sympathetic tone. (Choice C) Isolated pontine infarction can cause locked-in syndrome in which patients have complete quadriplegia and cannot speak; however, they typically retain consciousness, eye opening, and vertical eye movements (not present in this patient). In addition, drowning and prolonged cardiac arrest are more likely to cause diffuse hypoxic-ischemic brain injury than an isolated infarction. (Choice D) Sinus node dysfunction (ie, sick sinus syndrome) occurs when the sinoatrial node cannot produce a sufficient heart rate to meet physiologic needs. It may cause bradycardia but more commonly leads to intermittent low blood pressure (eg, causing syncope) than hypertension. In addition, it primarily occurs in elderly adults. (Choice E) Stress-induced (takotsubo) cardiomyopathy, a reversible cardiomyopathy likely caused by toxicity from surging catecholamines, can occur after severe physical stress. However, it most commonly occurs in postmenopausal women (vs children) and has not been associated with drowning. In addition, it usually presents with chest pain, ECG findings of ischemia, and/or elevated serum troponins (not present in this patient). (Choice F) Uncontrolled pain can cause hypertension in an intubated patient; however, tachycardia (not bradycardia) and increased motor activity (vs lack of response to painful stimuli) would be expected. Educational objective: Hypoxic-ischemic brain injury (eg, drowning) can lead to widespread neuronal cell death, cerebral edema, and increased intracranial pressure (ICP). Severely increased ICP can cause Cushing triad, characterized by hypertension, bradycardia, and irregular respirations. References: Drowning. (http://www.ncbi.nlm.nih.gov/pubmed/22646632)

A 2-Year-Old Boy Was Hospitalized 24 Hours Ago After a Swimming