Intracranial pressure-alterations during controlled intramedullary reamingof femoral fractures: an animal study

Reaming during intramedullary nailing increases the intramedullary pressure (IMP) and can cause fat intravasation and subsequently lead to pulmonary d ysfunction, especially in polytraumatized patients with lung contusion as w ell as increases in intracranial pressure (ICP). ICP changes were measured in two groups consisting of 12 sheep each with ei ther a fractured or intact femur. The animals were exposed to haemorrhagic shock and were resuscitated by autoinfusion. Transverse midshaft fractures were created bilaterally in one group before reaming of both femoral shafts . Controlled reaming was performed at 15 and 50 mm/s driving speed (DS) and at 150 and 450 revolutions per minute (RPM) with a reaming control system using AO-Reamers. Fat intravasation was measured by transoesophageal sonogr aphy (TES) and Gurd test. ICP monitoring was performed with a piezo-electri c epidural catheter. Haemodynamic and respiratory parameters, ICP, and cere bral perfusion pressure were measured continuously. High DS and low RPM caused higher IMP and ICP increases in both groups. Sig nificantly higher microemboli were observed in TES in the fractured group a s compared to the unfractured group with the same reaming parameters (P = 0 .021). However, the existence of a femoral fracture did not show a signific ant influence on changes in ICP (P-value = 0.057). Reaming should be perfor med at a low DS and high RPM to minimize the risk of fat intravasation and the subsequent ICP increase. (C) 2001 Elsevier Science Ltd. All rights rese rved.