The Short Answer: A core temperature drop of just 2°C during surgery can triple the risk of surgical site infection. Hypothermia impairs immune function, alters drug metabolism, and increases blood loss.

Two degrees Celsius. That is all it takes. A core temperature drop most people would not even notice on a monitor can triple the rate of surgical site infection. It is one of the most striking — and preventable — findings in perioperative medicine.

The Landmark NEJM Study

In 1996, the New England Journal of Medicine published a randomised controlled trial involving 200 colorectal surgery patients. One group was actively warmed to maintain normothermia. The other was allowed to become mildly hypothermic — a core temperature drop of roughly 2°C.

Why Cold Tissue Cannot Fight Infection

When core temperature drops, the body responds with peripheral vasoconstriction. Blood is shunted away from skin and subcutaneous tissues to protect vital organs. The surgical wound, sitting in those peripheral tissues, is starved of oxygen.

Neutrophils — the white blood cells responsible for killing bacteria at the wound site — depend heavily on oxygen to function. Their oxidative burst, the mechanism that destroys invading organisms, requires adequate tissue oxygen tension. In cold, vasoconstricted tissue, they simply cannot mount an effective immune response.

The scale is enormous. Hypothermia affects up to 70% of patients during prolonged surgery. It is one of the most common yet preventable risk factors for post-operative complications.

The Theatre Temperature Paradox

Here is the dilemma that plays out in operating rooms every day. The patient needs warmth — warming blankets, heated IV fluids, elevated room temperature. But the surgeon is gowned, gloved, standing under hot theatre lights, and concentrating intensely for hours. They are overheating.

The natural instinct is to crank the air conditioning down. When the person who controls the room temperature is also the person who is uncomfortably hot, the patient's thermal needs often lose.

This is where surgical attire becomes a clinical variable, not a comfort preference. When scrubs and scrub caps are made from breathable, moisture-wicking fabric, the surgeon stays cooler without needing to refrigerate the room. The patient stays warm. The infection risk stays low.

A breathable scrub cap is part of how you manage the temperature conflict. It keeps heat from building at the scalp — one of the body's primary thermoregulation sites — without touching the thermostat.

The Bottom Line

Surgeon comfort and patient safety are not competing priorities. They are connected. Two degrees is a small number with enormous consequences, and what you wear in theatre is part of the equation.

Source: Kurz A, Sessler DI, Lenhardt R, NEJM, 1996;334(19):1209–1215 (PMID 8606715).