How to Stay Warm in a Cold OR: 5 Layering Tactics

The standard OR runs between 60 and 68 degrees Fahrenheit. Surgeons set the temperature. Surgeons are gowned, masked, gloved, and lit by surgical lights — they're warm. Everyone else in the room is cold, often shivering by hour three of a long case, and there's no fixing the thermostat. The only thing you control is what you wear under your scrubs.

This guide is the five layering tactics OR nurses actually use, ranked by how much warmth they add per dollar spent and per minute of extra time getting dressed. Written from the perspective of an RN who's stood in cold ORs for full shifts and tried most of these.

Why the OR is cold (and why it stays that way)

Operating rooms run cold for three reasons: low temperature reduces bacterial growth, surgical teams in gowns and masks generate significant heat, and most patients lose body temperature during surgery and need cool ambient air to prevent overheating once warming devices are applied. The ASHRAE Standard 170 for healthcare facilities sets 68–75°F for ORs, but most hospitals run on the cold end of that range to make life easier for the surgical team. Many nurses report ORs running cooler than that spec — 60–68°F is what we hear most often on the floor.

For the circulating nurse, the scrub tech, anesthesia residents, and anyone else not in a gown, this means standing in 65°F air for hours at a time. Add the AC vents directly overhead, the surgical lights' heat sink effect drawing air, and the lack of physical movement during long cases — it's the coldest ward in the hospital.

Tactic 1: Start with a warm underscrub

The biggest single change you can make is swapping a t-shirt or short-sleeve underscrub for a long-sleeve underscrub built for warmth. Look for a fabric specifically described as "thermal," "ThermoLite," "warm," or "insulating" — not just "long sleeve." A regular long-sleeve underscrub adds maybe 1–2 degrees of perceived warmth. A purpose-built warmth-focused underscrub adds 4–6 degrees.

The construction details that matter: - Brushed inner surface that traps body heat against the skin - Higher GSM fabric (200+ GSM versus 150 for a standard underscrub) - Mockneck or higher scoop — the back of the neck is where you lose the most heat - Long enough hem that it stays tucked under your scrub waistband even when you reach overhead

Our ThermoLite Mockneck is the underscrub we built specifically for this — designed around the cold-OR use case, with a brushed interior and a mock neckline that doesn't show under most V-neck scrub tops.

Tactic 2: Layer a fitted base under your underscrub

For the coldest cases (cardiac, neuro, orthopedic — anything 4+ hours), some OR nurses double-layer: a thin compression layer against the skin, then a warmth-focused underscrub over it, then the scrub top. The compression layer wicks sweat that builds up early in a long case, while the warmth-focused underscrub traps heat against your core.

This only works if both layers are slim enough that the combined silhouette is still smooth under your scrub top. Two t-shirts equals lumpy. A fitted compression layer plus a fitted warmth underscrub equals an extra 5–8 degrees of perceived warmth with no visible bulk.

The FlexForm Compression Long-Sleeve is built to be slim enough for this double-layer use.

Tactic 3: Warm-up garments designed for the OR

Most OR nurses know the warm-up jacket — short scrub-top jacket designed to be worn over the scrub top, usually with elastic cuffs and a collar. These work, but they have downsides: they're bulky, they're often unflattering, they can violate uniform policies in stricter hospitals, and they need to come off when you scrub in or step into the sterile field.

Use a warm-up jacket strategically: between cases, during long set-up periods, or in non-sterile areas. Don't rely on it as your primary warmth layer for the case itself, because the moment you have to remove it, you're back to the cold scrub top alone.

Tactic 4: Footwear and circulation matter more than you think

You can wear the best underscrub on the market and still be miserable if your feet are cold. Cold feet trigger vasoconstriction, which makes the rest of your body feel colder. The fix:

• Thick wool or wool-blend socks — merino is the gold standard for OR use because it stays warm even when damp
• Insulated clogs or surgical shoes rather than the standard mesh sneaker
• Compression socks if you're standing for long cases — they also improve circulation and reduce fatigue

If you've already optimized your upper-body layering and you're still cold, try thicker socks and a warmer pair of clogs first. The difference is significant.

Tactic 5: Pre-warm before the case

This sounds small but it works: spend 5–10 minutes before scrubbing in moving around briskly — walking the hallway, taking the stairs, stretching with intent. The goal is to elevate your core temperature by a degree or two before you enter the cold OR. Your body holds that elevated baseline for 20–30 minutes, which gets you through the cold acclimation period without shivering.

Hot tea, hot soup, or a warm meal in the 30 minutes before a case has a similar effect — your body is in active thermoregulation when you walk in, not in resting-cold mode. Not every nurse does this; many find that just hitting the floor briskly between rooms before scrubbing in is enough.

What doesn't work

• Hand warmers in your scrub pocket. Brief relief, no systemic warmth, and they're a contamination concern in the sterile field.
• Drinking coffee right before. Caffeine causes peripheral vasoconstriction — your hands and feet get colder, not warmer.
• Layering with an oversized t-shirt under your scrubs. The bulk creates pressure points and traps sweat. Heat trapping ≠ warmth in a high-airflow environment.
• "Just dealing with it." Cold stress over a 12-hour shift causes fatigue, slower reaction time, and impaired fine motor control. It's not just discomfort.

The OR layering system that works

Here's the system we recommend for a 4+ hour case in a cold OR:

1. Wool-blend socks + insulated clogs
2. Compression long-sleeve base layer (skin-side, wicks sweat)
3. Warmth-focused underscrub (ThermoLite Mockneck or equivalent) over the compression layer
4. Standard scrub top
5. Warm-up jacket over everything between cases / during set-up
6. Pre-warm with 5 minutes of brisk walking before scrubbing in

This system handles most ORs in most hospitals. For specialty cases (cardiac, neuro, transplant) where cases run 6+ hours and the room runs colder, swap the warmth-focused underscrub for a heavier thermal piece if you can find one in a healthcare-appropriate cut.

A note on overheating

The flip side of OR cold is the cath lab and IR suite — usually warmer because of the equipment heat, and you'll overheat fast in a thermal underscrub. Match your underscrub to your specific unit, not to the broad category of "OR." If you float between units, keep two underscrubs in your locker: one warm for OR, one breathable for warmer suites.

Want to keep reading?

• Care & longevity guide — how to keep your underscrubs in great shape for years
• Our fabrics — the science behind each Ala blend
• Size & fit guide — find the underscrub that disappears under your scrub top
• Ala vs FIGS comparison — how we compare to the category leader
• Underscrubs 101: The Complete Guide — the broadest overview of the underscrub category
• The Underscrub Buying Guide — a step-by-step framework for picking the right piece
• Underscrub vs. Compression vs. Base Layer — how the categories actually differ
• Why Your Scrubs Show Through — the real cause (it's not what you think) and the fix
• Sweat, Odor, and 12-Hour Shifts — what actually works for long-shift comfort

References

1. ASHRAE Standard 170: Ventilation of Health Care Facilities — The temperature spec for operating rooms (68–75°F), referenced when discussing cold-OR shift conditions.
2. Association of periOperative Registered Nurses (AORN) — Professional standards for perioperative nursing practice referenced on OR-specific layering and apparel.