This here is serotonin syndrome, and it's presenting to you as a constellation of factors including mental status changes, autonomic instability, and neuromuscular hyperactivity. Serotonin syndrome is caused by the increase of CNS serotonergic activity that's caused either by increased dosage of a serotonergic drug or excessive serotonergic activity caused by different serotonergic drugs taken together. This process can occur in as little as six hours after a dosage of medication had been increased. So the onset of serotonin syndrome can occur within three to six hours after the medication was increased or after the patient started taking multiple serotonergic drugs. This will pass on its own within several days.
Causes of serotonin syndrome include SSRIs and then SSRIs in overdose. SSRIs taken perhaps in conjunction with lithium or lithium by itself. Meparidine, triptans, monoamine oxidase inhibitors, and cocaine.
An SSRI plus a monoamine oxidase inhibitor will dramatically increase the risk. The classic scenario in this particular toxidrome is the young 23-year-old female who is on a monoamine oxidase inhibitor. for her depression, was using some cocaine, and then later came to the emergency room complaining of abdominal pain. She was initially seen by some interns who prescribed for her Demerol or Meparidine for her pain, and then Compazine for her nausea.
And in this particular case scenario, the patient's neurological condition worsened. She was restrained. I think she was actually given an additional dose of Meparidine, and ultimately she went into a coma and died. What you'll see as far as the signs and symptoms of serotonin syndrome include mental status changes, which include confusion, agitation, which progresses to lethargy, then coma.
The autonomic instability includes hyperthermia, tachycardia, medriasis or dilated pupils, diaphoresis with nausea, vomiting, and diarrhea. There's going to be a high degree of... neuromuscular hyperactivity which includes hyperkinesia, hyperreflexia, trismus, myoclonus, and some cogwheel rigidity.
The hyperreflexia and clonus is going to be more prominent in the lower extremities. Hyperreflexia, cogwheel rigidity, again in the lower extremities. There might be some bruxism, grinding of the teeth, diaphoresis.
and a lot of hypermotor activity. They've come up with the mnemonic memory aid, wet dog shakes, because the patient will be shaking and trembling, very diaphoretic, much like we see if a dog comes in after swimming in a pool and starts shaking off. When a patient presents with serotonin syndrome, you're going to have to obtain a detailed history and physical exam, hopefully from the patient or from bystanders.
Because you're going to have to differentiate serotonin syndrome from anticholinergic overdose, neuroleptic malignant syndrome, and malignant hyperthermia. And in this cartoon here, I drew myself from the anticholinergic overdose cartoon, and I'm saying it has some similarities to anticholinergic overdose, however this patient has diaphoresis, nausea and vomiting, whereas I, in anticholinergic overdose, am dry as a bone. She's hot and wet. Treatment for this is going to be supportive. It's going to include discontinuation of all serotonergic agents.
You're going to have to practice the ABCs of airway, breathing, circulation, cardiac monitoring, IV fluids, benzodiazepines for anxiety, agitation, and tachycardia. If there is significant hyperthermia, you're going to need to use some cooling blankets. You might consider intubation with muscle paralysis and severe hypertension should be treated only with short-acting antihypertensives such as nitroprusside because of that fluctuation in the autonomic instability.
There is a particular treatment of cryptoheptadine which can be given in those cases not controlled by benzodiazepines and supportive measures alone.