There is a quiet irony in modern anaesthesia. We fight hypothermia with the discipline of a watchmaker — warmed fluids, forced-air blankets, core probes, and protocolized targets. The monitor finally shows 36.7 °C. Everyone exhales.

And yet, rarely — but undeniably — the drapes come off and a blister appears. No flames. No smoke. No alarms. Just heat, sustained and unopposed.

Heat can be a blanket… or a slow scalpel.

1) What Is a Low-Temperature Burn?

A low-temperature burn (also called a low-heat or contact thermal injury) is not caused by dramatic heat. It occurs when moderate temperature is applied for a long enough duration to injure tissue. In the operating room, this typically involves warming devices where the surface or delivered air is warm, but exposure is sustained and sometimes concentrated.

2) The Time–Temperature Relationship: Why “Not That Hot” Can Still Burn

Thermal injury behaves less like an on-off switch and more like an exponential curve. Around 43 °C, injury can occur with prolonged exposure; as temperature rises, the time to injury drops steeply. This is why “low-temperature burns” are fundamentally time-dependent.

Conceptual Time–Temperature Pattern (Not a clinical dosing chart)

43 °C  → hours (risk increases with vulnerability + pressure)
45 °C  → minutes
50 °C  → seconds

In anaesthesia, “hours” is not abstract. It is the duration of a spine case, a prolonged abdominal surgery, or an unexpectedly complex airway + resuscitation scenario. When time stretches, the risk window opens quietly.

3) Why the Anaesthetised Patient Is Uniquely Vulnerable

4) Forced-Air Warming: Safe Standard of Care — With Specific Failure Modes

Forced-air warming remains widely used and recommended for prevention of inadvertent perioperative hypothermia. In the published literature on injuries, a recurring theme is not routine correct use — but misuse or stacked risk factors.

4.1 “Hosing” — the classic preventable mechanism

“Hosing” refers to directing warmed air from the hose toward the patient without the manufacturer’s diffuser blanket attached. This concentrates heat in a small area instead of distributing it. Multiple published reports and safety advisories highlight this mechanism as a major contributor to severe burns.

4.2 Prolonged high setting: when the margin narrows

Many systems include a high setting around 43 °C. Clinical protocols may use such settings safely under defined conditions, but prolonged exposure, impaired perfusion, moisture, pressure points, or combined warming can shrink the safety margin. Published case reports describe injuries in prolonged cases where multiple risk factors converge.

In the OR, time is elastic — and tissue pays the interest.

4.3 Underbody conductive warming and pressure synergy

Underbody warming surfaces place heat and pressure on the same tissue bed. In prolonged surgery, especially in elderly or vasculopathic patients, this can increase the risk of both pressure injury and thermal injury — sometimes simultaneously.

4.4 Combined warming modalities: additive thermal load

Forced-air warming + warmed fluids + radiant heat can be clinically appropriate, but additive thermal load can be underestimated. The patient cannot report discomfort; therefore, monitoring and reassessment become the compensatory defense.

5) How Low-Temperature Burns Present Clinically

These injuries often appear after the case — in recovery, in the ward, or even the next day. Because onset can be delayed, the association may be missed unless a team actively looks for it.

6) Myth vs Fact (Quick Reset) 🧠✨

7) Risk Stratification: Who Needs Extra Vigilance?

8) Prevention Bundle: A Practical, Evidence-Consistent Checklist 🛡️

9) Flowchart: A Simple Decision Approach (Readable + Deployable)

Start
  │
  ├─► Assess patient risk (diabetes/PVD/vasopressors/age/frailty)
  │        │
  │        ├─► High risk? ─► YES ─► Moderate setting + pressure-point plan
  │        │                          + early step-down target
  │        │
  │        └─► NO  ─► Standard setting with continuous temperature monitoring
  │
  ├─► Normothermia achieved (≥ 36 °C)?
  │        │
  │        ├─► YES ─► Step down setting + reassess every 30–60 min
  │        │
  │        └─► NO  ─► Continue warming + check placement, perfusion, stacking
  │
  ├─► Prolonged case (> 3–4 h)?
  │        │
  │        ├─► YES ─► Re-check pressure points (occiput/scapulae/sacrum/heels)
  │        │
  │        └─► NO
  │
  └─► Post-op skin check in PACU/ward (especially high risk) → Document

10) The “Above 40 °C” Question: A Balanced Answer

Clinicians often hesitate above 40 °C not because the number is “evil,” but because the safety margin narrows: the time-to-injury shortens, and vulnerability factors (pressure + perfusion impairment) become more relevant.

11) Documentation and Medico-Legal Clarity 🧾

Low-temperature burns can lead to institutional review and medicolegal scrutiny. Good documentation is not defensive — it’s patient-centered clarity.

12) Final Takeaways (Fast Recall) ⚡

Warm the patient — and warm the system with vigilance. 🛡️

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