Dr. Gentile responded to a few listener questions below:
HOW DIPHENHYDRAMINE ENTERED PROTOCOL
when i first started using “high” dose opiates for the most severe patients about one third of them experienced nausea and or vomiting. Sometimes the guy in bed 2 vomits, then after /during mop up the girl in bed 3 vomits, the woman in 5 is here for asthma she is offended by the smell and she vomits too. i was not popular with housekeeping but i was much appreciated by those who received the opiates. i asked some of the worst vomiters if the vomiting was worse than the pain. Every single one said the vomiting was no problem ,and they felt better vomiting than they did in pain. Some even vomited while they were answering the question.
The next leap was giving IV antiemetic prophylactically, with the first dose of morphine. i initially felt some trepidation giving anti-emetic when 2/3 of patients probably would not benefit from the drug. Then i remembered demerol and phenergan had been given together for ages. i felt validated by this precedent and forged ahead. it worked great and the vomiting/mopping cycle stopped. Housekeepers stopped giving me the stink-eye.
My favorite anti-emetic was compazine. There were a few dystonic reactions and some akisthesia but overall it was a success.
Compazine was unavailable for a few years and i switched to droperidol. The droperidol gave a lot less dystonia and less akisthesia, so that too was progress. Hundreds of happy doses of droperidol and no problems. It was a useful adjunct for analgesia,
Droperidol was great for nausea and vomiting without pain. Many of the vomiting patients reaped the benefit of central dopamine antagonism as well [Some people with abdominal pain are crazy ]. What a great drug. Droperidol got black boxed. Once again the interests of the suffering masses were sacrificed to the interests of big pharm. The instrument of destruction was our FDA, an organization that is supposed to protect people from big pharm. I started looking for other options.
A haldol overdose came in one day and i was reading about butyrophenone overdose and discovered the butyrophenones [haldol, droperidol] have antihistamine side effects. That’s when i had the insight that histamine was the real culprit causing the the vomiting.
Histamine causes an itchy feeling when the opiate goes into the vein, histamine causes hypotension, histamine causes nausea and vomiting. Do all anti-emetic drugs have anti histamine “side-effects”. Compazine yes reglan yes droperidol yes tigan yes phenergan yes. Zofran [i'm not sure]. I would call this more than an interesting coincidence. The antihistamine side effect of anti-emetic drugs might be the mechanism of action, not really a side -effect at all.
Have you seen an orthopedic injury that hurts so bad the patient vomits? Do endogenous opiates cause histamine release?
Many ER patients have abdominal pain and vomiting; most of the time the pain protocol gets rid of both the pain and the vomiting. Not true with small bowel obstructions but most of the time additional “anti-emetic” is not needed.
so diphenhydramine went into the protocol; and life is very good. i got a little sad that patients receiving state of the art acute analgesia were getting admitted to the hospital and taking the elevator to 1960. i thought it might be nice if admitted pain protocol patients got a PCA pump automatically. i started reading about PCA pump protocols and most of them use diphenhydramine and morphine. The PCA literature validates what i “discovered”. The anesthesiologist/oncologists that developed PCA have known that diphenhydramine is useful for a long time.
Diphenhydramine at .5 mg/kg does not make old or young people too sleepy. Some people on the protocol go to sleep. Some of the patients are tired. If i was awake at home for three days with a broken hip, i would go to sleep the moment someone took the edge off my pain. Some of the patients are bored to sleep. If i was in the ER gurney without a book what are my options [read "patient rights and responsibilities" again, watch my heart rhythm, or sleep.] Sleep is not a little dead. Sleep is good.
i do not have references to support my statements about hypotension. Only my subjective observations that there have been a lot less of this conversation at work since we started using diphenhydramine.
aren’t you tired of this conversation.
nurse———–“the blood pressure is down in clinic 7 bed”
doctor—–“give em 500 normal saline stat”
10 minutes later
nurse——“the pressure is back up”
was the patient in bed 7 sick? did they get better? was their life saved or even subtly improved by a transient change in a measurement they can not feel?
i agree that a blood pressure of zero is usually bad, but if my blood pressure drops 10% i am not 10% dead. The culture around blood pressure measurements and reactions/over reactions in the E.R. is irrational.
The less time spent on this futile ritual the better. i am sure there has been less of this since diphenhydramine was included. i did not count it or study it. i just noticed it like i notice the weather is usually sunny on my way to work. It’s true. if you like sun move to southern california.