Page 191 - Ultrasonography in Prehospital and Emergency Medicine - Rein Ketelaars

Increase in intracranial pressure by application of a rigid cervical collar 189
Introduction
Often, patients with head-injuries suffer from additional cervical spine injury. For decades, trauma victims have been immobilized routinely when cervical injuries could not be ruled out at the scene. Rigid cervical collars and spine boards were used during transportation in prehospital trauma care. As advocated in advanced trauma life support and prehospital trauma life support protocols, immobilization is continued until cervical spine injury is ex- cluded.1,2 To minimize secondary damage to the spinal cord, in-line immobilization will be continued during transportation and examination.3 Several devices to help immobilize the cervical spine such as the Stifneck® rigid cervical collar are commercially available.
The application of rigid cervical collars increases the intracranial pressure (ICP) of brain-in- jured patients in ICU settings.4–6 This increase in ICP is attributed to compression of the internal jugular veins.7,8 According to the Kellie Monroe doctrine, impaired venous drainage causes volume expansion inside the skull, which can increase ICP and lead to neurological deterioration.1 Besides an increased ICP, local pressure of the collar may exacerbate discom- fort and agitation in patients with mild or moderate TBI resulting in undesirable movement of the neck and an additional increase in ICP. More information on the effects of the cervical collar on the ICP is mandatory. However, outside of the ICU, it is not feasible to measure ICP directly.
Sonographic measurement of the optical nerve sheath diameter (ONSD) is a noninvasive, rapid method for indirect ICP monitoring.9–11 The meninges around the brain are in contin- uum with the optical nerve sheath and cerebrospinal fluid percolates freely from the cranial cavity into the optical nerve sheath.12,13 Previously, we showed that any change in ICP results in a simultaneous change in the ONSD in both eyes.9
In this study, the effects of the application of a rigid cervical collar on the ONSD were mea- sured in healthy volunteers. We hypothesize that a rigid cervical collar increases the ONSD (through a raised ICP) in healthy volunteers with intact cerebral autoregulation.
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