Thursday, November 19, 2009

What to do when you need to give a drug, you don't know the dose, and don't have time to look it up

This happened to me the other night. A patient had dangerously high blood pressure, and legitimately had reasons she could not take most of your first line blood pressure drugs.

The blood pressure needed to come down, and fast, so I decided to give nitroglycerin under the tongue. Unfortunately, the particular department only stocked a type that I was unfamiliar with, and didn't know the dose.

Here's what you do: ask the nurse to show you the available pills. If you want to look like you know what you are doing, pretend like you want to see because you are weighing your options, or like you doubt that this department will really have what you want.

In this case, there were 3 different dose pills of the drug. The highest dose pill was 6 times that of the low dose one, hinting at a wide therapeutic window.

Then, use one pill of the very lowest dose there is. Unless it is a strange drug, a drug that requires a very slow titration to full dose, or a drug like digoxin, you will rarely go wrong. Since I saw that my lowest dose was 1/6 of the highest one, I figured that even if the one pill didn't work, I could easily add another. She was naive to this drug.

Sure enough, a few minutes after sublingual administration, her blood pressure was reasonable - not great, but she wasn't going to have a massive stroke because I didn't know what to do.

Remember, as scary as it is to mess with a drug you don't quite know about, if it's common, the lowest dose pill is probably taken by millions of people every day.


Carey said...

Can I try to reassure you?

The situation you describe doesn't actually exist. Realize that apart from a very few emergency situations, you will always have time to look up the dose. Or, alternatively, you need to be doing something else besides giving meds.

Cardiac arrest, coma, seizure... those are about the only times you'll want a fast drug. But even here, the drugs are usually secondary. Instead, think Airway, Breathing, Circulation. You have time to look up the drug, or you have time to tell someone else to look it up while you are compressing the chest or bagging the patient or holding pressure over a massively bleeding wound. If I only had to memorize one emergency dose, it would be: "one amp of D50."

Many nurses (and doctors!) don't understand that high blood pressure is almost never an emergency. End organ damage from hypertension can be, but don't ever just treat a number. Ask if the patient is encephalopathic (they acting goofy?); if their kidneys are failing; if they're in pulmonary edema or if their aorta is dissecting. No? Not an emergency.

Milk and Two Sugars said...

Nevertheless, there is an expectation that if the blood pressue is "too high", we will deal with it. To be able to do so calmly, safely and conservatively is a skill. I'll be using this one, Sara.

Rose said...

I'm a JHO - I agree with Carey. The only time you won't be able to take the time to look up a dose of a medication is in a medical emergency, in which case your priorities are ABC and there will (hopefully!) soon be more senior doctors arriving to help you.

Although sometimes as a junior doctor you can feel pressured to quickly make decisions, it's always worth taking to time to look up the dose, interactions and contraindications of a drug. My advice is don't mess about with drugs you're completely unfamiliar with. There are so many medications that we deal with it's always worth checking and double-checking to minimise any possible danger to the patient. Also, in the time it might take the nurse to find the pills you could jump online and took at therapeutic guidelines or mims anyway. With so many easily available resources around you wouldn't forgive yourself if harm came to a patient from an educated guess rather than self-education.

Kelly said...

I was always taught to never make educated guesses when it comes to drug doses, especially with drugs you are unfamiliar with. If in doubt, always take a couple of minutes to check in the BNF or your country's equivalent. We almost always have a hard copy lying around on the ward but, on the rare occasion I can't find one, I take 2 minutes to check the online version. Better to be safe than sorry and it takes no more time than looking at the actual pills.

medstudentitis said...

I carry tarascon's pharmacopoeia in my pocket and the "emergency drugs" I have in the front i.e. status epilepticus algorithm and my ACLS and PALS cards. I find that has served me well.

DHS said...

There is the ampoule theory of drug administration: that one ampoule of any drug is the correct dose. This is, of course, only in adult patients; paediatrics may use much less than an ampoule.

You should not be commencing any medication you do not know well enough to cite the doses off the top of your head, as a new house officer. This, of course, means a lot of frantic phone calls to your registrar in the first few days, but eventually you become quite familiar with most of the drugs you use day to day.

There is no situation where you do not have the time to look up the dose or ask someone more senior. Any situation that urgent, you call an arrest, and presto, there is someone more senior.

Dr Michael Anderson said...

Sara, I agree with some of the commentors above, I'm pushed to think of an occasion when you don't have time to look up the correct dose of a drug.

In the situation you describe, the extra two or three minutes you spend looking up the dose isn't actually going to make a whole lot of difference to the patient's outcome and besides in the time it takes for you to "ask the nurse to show you the available pills. If you want to look like you know what you are doing, pretend like you want to see because you are weighing your options, or like you doubt that this department will really have what you want," surely you could have opened a BNF or looked online for the dosage info?

Judy said...

A few months ago, my 8 pound patient went into symptomatic SVT. I have 30+ years of NICU experience, the other nurses in the NICU that night had over 100 years of combined experience. The nurse practitioner has been doing this for over 20 years.

SVT, not hypertension.

She took the time to look up the medication dose AND to call the neonatologist at home at 3am.

Never let anyone pressure you into acting more quickly than you should. Codes, of course, are different, but by now you're probably on autopilot for those and there will be a crowd around you to offer advice and get in your way.