A 63-year-old man collapses at home after experiencing severe retrosternal chest pain. The emergency medical team finds him with no pulse, and cardiac monitoring shows ventricular fibrillation. Cardiopulmonary resuscitation is performed, and the patient regains spontaneous circulation after several minutes. On arrival at the hospital, he has stable vital signs but does not follow commands or respond to strong stimuli. Which of the following areas is most likely to be affected first by ischemic damage in this patient?

Question

A 63-year-old man collapses at home after experiencing severe retrosternal chest pain.  The emergency medical team finds him with no pulse, and cardiac monitoring shows ventricular fibrillation.  Cardiopulmonary resuscitation is performed, and the patient regains spontaneous circulation after several minutes.  On arrival at the hospital, he has stable vital signs but does not follow commands or respond to strong stimuli.  Which of the following areas is most likely to be affected first by ischemic damage in this patient?

Quizplus · Accepted Answer

This patient's cardiac arrest, secondary to ventricular fibrillation, caused rapid cessation of cerebral blood flow and global cerebral ischemia. Although cardiac function and circulation were restored after medical intervention, the patient's brain was subjected to ischemia for an unknown length of time, resulting in neurological impairment. Global ischemia lasting longer than 3-5 minutes can cause irreversible damage to neurons. The cells that are typically affected first by hypoxia are the CA1 pyramidal neurons of the hippocampus, which can be damaged by ischemia in as little as 3 minutes. The cerebellar Purkinje cells and neocortex pyramidal neurons are also highly susceptible to damage if ischemia lasts for 5-10 minutes. These neurons are likely vulnerable to ischemia because of their high metabolic demand and unique neurochemical characteristics (eg, inability to repolarize after anoxic depolarization). The hippocampus is located in the medial temporal lobe and plays an essential role in memory, spatial processing, and response inhibition. Selective damage to the hippocampus is common with transient ischemia and can result in an inability to make new memories (anterograde amnesia) and disorientation to place or time. (Choices A, C, D, and E) Although the caudate nucleus, hypothalamus, substantia nigra, and thalamic nuclei are also vulnerable to ischemia if cerebral hypoxia is sustained, they are not as susceptible to damage as the hippocampal CA1 pyramidal neurons. Educational objective: Global cerebral ischemia is typically precipitated by systemic hypotension (eg, cardiac arrest). The cells most susceptible to ischemia are the CA1 pyramidal neurons of the hippocampus. Other areas of the brain that are damaged early in the course of global cerebral ischemia include the cerebellar Purkinje cells and the pyramidal neurons of the neocortex. __________ References: Mechanisms of injury in hypoxic-ischemic encephalopathy: implications to therapy. (http://www.ncbi.nlm.nih.gov/pubmed/16969737) Mechanisms of brain injury after global cerebral ischemia. (http://www.ncbi.nlm.nih.gov/pubmed/16443127)

A 63-Year-Old Man Collapses at Home After Experiencing Severe Retrosternal