title: Collateral damage:  heat transfer as a possible mechanism of optic nerve injury during neurosurgical intervention.
abstract: OBJECTIVE
  To determine factors associated with increased heat transfer during neurosurgical drilling as a mechanism for optic nerve injury.
  
  
  METHODS
  On a nonembalmed cadaver, the optic canal was exposed through a standard craniotomy and optic nerve sparing exenteration. The temperature was measured with a thermocoupler during each 30-second continuous drill session using 2 types of neurosurgical drills. The location of the probe, drill site, drill power, and irrigation rate were varied.
  
  
  RESULTS
  A <1 °C change was measured in the optic canal at all test distances with the Cavitron Ultrasonic Surgical Aspirator and diamond drill. The use of manual irrigation decreased the mean change in temperature (ΔT) in the sphenoid bone from 4.7 °C without irrigation to 1.3 °C with irrigation. Increasing Cavitron Ultrasonic Surgical Aspirator power from 50% to 80% at an irrigation rate of 4 ml/minute more than doubled ΔT in sphenoid bone from 3.2 °C at 50% to 8.1 °C at 80%. Increasing irrigation from 2 to 4 ml/minute decreased mean ΔT by -1.1 °C (3.2 °C at 2 ml/minute versus 2.1 °C at 4 ml/minute) at Cavitron Ultrasonic Surgical Aspirator power of 50%, but at Cavitron Ultrasonic Surgical Aspirator power of 80%, increasing irrigation increased mean ΔT by 3.0 °C (3.7 °C at 2 ml/minute versus 6.8 °C at 4 ml/minute).
  
  
  CONCLUSIONS
  Care must be taken during neurosurgical procedures to decrease heat transfer during drilling to nearby structures. With increase in drill power, there is a noticeable increase in temperature change from baseline. These temperature changes can be mediated by irrigation, although the effect of increasing irrigation rate to suppress the raise in temperature decreases with increasing drill power.
authors: Division of Oculofacial Plastic and Orbital Surgery, Kansas University Eye, Kansas City, Kansas, USA.
authors: My Le
authors: ML
authors: Shaw
authors: Brian
authors: B
authors: Kelley
authors: Paul
authors: P
authors: Camarata
authors: Jason A
authors: JA
authors: Sokol
mesh_terms: D001831:Body Temperature; D019299:Decompression, Surgical; D005357:Fibrous Dysplasia of Bone / Q000601:surgery; D006801:Humans; D013508:Ophthalmologic Surgical Procedures / Q000295:instrumentation; D020221:Optic Nerve Injuries / Q000209:etiology*; D009915:Orbit / Q000601:surgery*; D010865:Pilot Projects; D013525:Surgical Instruments / Q000009:adverse effects*; D007507:Therapeutic Irrigation / Q000379:methods; D013817:Thermography