OUTCOME Lasting improvement
Mr. L presents for follow-up in the psychiatric clinic 3 weeks after his emergency room visit. After his limousine was repaired, his symptoms resolved. He no longer experiences fatigue during the day with higher energy at night, palpitations, jitteriness, headache, or tingling. His concentration has improved, so he opts to stick with the 18-mg dose of methylphenidate ER rather than increase it to the initial dose. He places a CO detector in his vehicle, which proves to be a good decision when it gives him a warning that the exhaust leak had not been properly repaired.
The author’s observations
Although the correct cause of Mr. L’s symptoms was found incidentally, this case is an important reminder to always consider medical causes in the differential diagnosis. We are taught in medical school to look first for horses (more likely causes), not zebras (less likely causes), but sometimes zebras do occur. Be mindful that medical causes should be considered not only for symptoms of primary illnesses, but also for symptoms thought to be caused by adverse effects of medications. The differential diagnosis for Mr. L’s symptoms (palpitations, agitation, anxiety, irritability, weight loss, fatigue, nausea, and headache) included metabolic and endocrine abnormalities (thyroid disease, pheochromocytoma, hypoglycemia); psychiatric conditions (panic, bipolar disorder, depression); substance abuse (caffeine, cocaine, amphetamines); immune disorders; cardiac disorders; malignancy; toxic exposure; infectious sources; and nutritional deficiencies. CO poisoning can cause many of these symptoms (Table 2).1,2,8
Intentional CO poisoning should be considered in an obtunded or unconscious patient with depression. Patients may consider CO poisoning a more peaceful way to complete suicide than shooting, cutting, or hanging. As for unintentional poisoning, clinical suspicion can be increased by time of year, occupation, locale, and smoking status. Winter months increase risk because of the high use of heating devices, cars warming up in the garage, closed fireplace flues, and vehicle tailpipes blocked by snow. As in Mr. L’s case, occupation also may increase suspicion; drivers, mechanics, tollbooth operators, parking attendants, miners, and firefighters are all at increased risk for CO poisoning. Regarding locale, polluted urban environments as well as cold climates requiring heating sources cause higher risks for CO exposure. Rarely, excessive smoking can result in CO poisoning. The author once had a patient with schizophrenia who was admitted to the hospital with delirium. It was determined that he had CO poisoning from his 5-pack-a-day smoking habit.
Psychiatric patients often have the frustrating experience of their physical symptoms being attributed to psychiatric causes, which results in major medical issues being overlooked. We psychiatrists can fall into the same trap of overlooking medical illnesses, as indicated in this case, where Mr. L’s CO poisoning initially was attributed to adverse effects of his psychiatric medication.