ICU vs. OR: The Same Drugs, Different World!

If you’re an ICU nurse eyeing the OR (hello future CRNA!), you’ve probably already seen some of the most common drugs we give on a daily basis. Vasopressors, sedatives, antibiotics, even good ol’ rocuronium for your crumping ICU patient who needs an airway STAT. But here’s the twist: the same drugs act completely differently when you’re the one holding the syringe instead of titrating a drip order. Let’s break it down.

How Do Push-Dose Vasopressors Differ from ICU Drips?

In the ICU, you hang your norepi drip, chart your MAP goals, and call pharmacy if the bag looks like it’s getting empty, right? Well, in the OR, you are pharmacy. You’ll be giving your own push-dose pressors (phenylephrine, ephedrine, sometimes even epi), calculating concentrations to mix your own drip bags, and drawing them up before the patient even rolls in.

Push-dose: Short bursts for quick BP correction during induction or blood loss.

Infusions: Same vasopressors, but usually patient-specific and temporary. You might start a norepi or phenyl gtt, but these are often bridged, not titrated for hours/days like in the ICU.

There’s a time and place for when to give ‘what’: This all depends on the patient presentation, co-morbidities, and other hemodynamics. Here’s a few quick intros to the drugs we often push in times of need (aka HOTN).

1. Ephedrine
   • Push 5–10 mg at a time
   • Not used in the ICU, but it’s an OR favorite
   • Watch out for refractory tachycardia!
2. Phenylephrine:
   • Push 50–200 mcg at a time
   • Quicker onset than ephedrine
   • Watch out for refractory bradycardia!
3. Vasopressin
   • 0.5–2 units bolus at a time
   • Works great when phenylephrine and ephedrine just aren’t cutting it, usually when a patient is on some kind of ACE-I or ARB at home to treat their pre-existing HTN.
   • Doesn’t rely on adrenergic receptors, the perfect backup plan.
4. More rarely, push dose epi and norepi can be given, but they’re not typically the first “go-to’s”

• Know your concentrations. There’s no “pharmacy verified” here, it’s all you.

How Do Sedatives Vary Between ICU and OR Settings?

Yes, propofol, midazolam, and dexmedetomidine still exist, but the context changes drastically. In the ICU, your sedation goal might be RASS -2 to -3. In the OR? It’s lights out, baby.

• Propofol gtts run way higher during anesthesia than what you’d ever see in the ICU.
• You’ll also use propofol for non-intubated patients (crazy, right?) Think MAC cases, endoscopy, or cardioversion. You can use propofol without an ETT, because you’re continuously monitoring the airway and can intervene if needed (with devices other than just an ET tube).
• Versed and Precedex may still make an appearance, but usually as a pre-induction relaxer, not a long-term sedative. Precedex can also be given for things like helping prevent post-op delirium and even shivering in PACU. A lot of our drugs have multiple uses, and you’ll learn alllll about the pharmacology in school.

What Are the Key Considerations for Choosing Induction Agents?

As an ICU nurse, you probably see induction meds during codes or intubations, but in the OR, induction is something we do every day. You might know the saying “you have to (se)date, before you can sux” which is a helpful reminder of which medications come first on induction.

Sedate:

1. Etomidate, propofol, or ketamine , each has its moment:
   • Etomidate: stable for the hemodynamically fragile.
   • Propofol: smooth as silk but can tank your pressure.
   • Ketamine: dissociative magic, especially for hypotensive or asthmatic patients.
   • Every choice depends on your patient’s comorbidities, ex: heart failure, sepsis, trauma, etc. School goes deep into the mechanism behind each of these drugs, as well as which populations they are best suited for, and which to avoid them in at all costs.

Sux (aka paralyze!)

1. Rocuronium (roc) and succinylcholine (sux) are the usual neuromuscular blocker (NMB) suspects. Which one have you seen more commonly?
   Without getting too into the weeds of pharmacology, just know that rocuronium wins most days in the OR for routine, elective surgeries. Succinylcholine has its chance to shine in rapid sequence intubations with patients with full stomachs, as well as some trauma cases.
   Some other NMBs you might not have seen in the ICU are vecuronium (Nimbex – most commonly hung as a gtt), pancuronium, atracirium, cisatracurium, and mivacurium. See a pattern? The drugs ending in -ronium are steroidal neuromuscular blockers, and those ending in -curium are benzoquinone neuromuscular blockers. Both of these classes are non-depolarizing neuromuscular blockers, and succinylcholine is the odd man out as the only depolarizing NMB. (Google the difference if you’re so inclined! But don’t say I didn’t warn ya!)

How Is Paralysis Reversed in the OR?

Unlike the ICU, where you might paralyze, intubate, and move on, in the OR you reverse what you give. Before extubation after the surgery is done, you’ll check the train-of-four (TOF) on your handy dandy neuromonitoring device and give sugammadex (for roc – if you’re so lucky to have it available at your institution) or neostigmine/glycopyrrolate combos to bring those muscles back online before you drop the patient off in PACU. Note: sux does *not* require reversal!

What Are the Differences in Antibiotic Administration Between ICU and OR?

In the ICU, pharmacy handles timing and compatibility. In the OR, you’re timing the antibiotics yourself, typically within 30–60 minutes of incision, and making sure it’s in before the surgeon says “scalpel.” Sometimes you’ll give them as a push dose (ex: 2g Ancef in 10mL NS), sometimes as a free gtt (ex: you still need to run Vano in slowly). Either way, you’re in charge of ensuring proper timing and dosing, there’s no “MAR reminders” here.

Why Do CRNAs Make All the Calls in the OR?

In the OR, there’s no “can I get an order for…” moment. You’re the one making real-time pharmacologic decisions for all of the dosing, titration, reversal, and management. You’re assessing the hemodynamics in seconds, not minutes. You’re the pharmacist, the intensivist, the airway expert, and the advocate all in one.

Will I Actually Learn All This in CRNA School?

Here’s the part no one tells you: You will learn all of this in school. The doses, the mechanisms, the “why” behind every push. One day, you’ll just know what to grab for each situation and it’ll feel natural. You’ll walk into a room, see a BP trend, and know instinctively whether it’s a phenylephrine or ephedrine kind of moment. That confidence comes from time, repetition, and trusting your gut. But also, let’s be real, it’s okay to check your notes or ask a classmate. Every CRNA, no matter how seasoned, has looked something up mid-shift. Competence doesn’t mean knowing everything. It means knowing when to verify, double-check, or phone a friend.

What Should ICU Nurses Take Away from This?

The ICU teaches you to manage long-term physiology with the help of your lovely intensivist, pharmacists, and respiratory therapists. The OR teaches you to control it instantly, precisely, and safely. If you’re an ICU nurse heading toward CRNA school, start thinking beyond “orders” and start thinking like anesthesia:

1. Why am I giving this drug?
2. What’s the expected physiologic response, and the backup plan if it doesn’t happen?

Because soon, YOU will be the one writing the plan, and executing it in real time.

Resources like The CRNA Club can help you bridge the gap between ICU knowledge and OR readiness.

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