Ambulance deceleration causes increased intra cranial pressure in supine position: a prospective observational prove of principle study.

BACKGROUND: Ambulance drivers in the Netherlands are trained to drive as fluent as possible when transporting a head injured patient to the hospital. Acceleration and deceleration have the potential to create pressure changes in the head that may worsen outcome. Although the idea of fluid shift during braking causing intra cranial pressure (ICP) to rise is widely accepted, it lacks any scientific evidence. In this study we evaluated the effects of driving and deceleration during ambulance transportation on the intra cranial pressure in supine position and 30° upright position. METHODS: Participants were placed on the ambulance gurney in supine position. During driving and braking the optical nerve sheath diameter (ONSD) was measured with ultrasound. Because cerebro spinal fluid percolates in the optical nerve sheath when ICP rises, the diameter of this sheath will distend if ICP rises during braking of the ambulance. The same measurements were taken with the headrest in 30° upright position. RESULTS: Mean ONSD in 20 subjects in supine position increased from 4.80 (IQR 4.80-5.00) mm during normal transportation to 6.00 (IQR 5.75-6.40) mm (p < 0.001) during braking. ONSD's increased in all subjects in supine position. After raising the headrest of the gurney 30° mean ONSD increased from 4.80 (IQR 4.67-5.02) mm during normal transportation to 4.90 (IQR 4.80-5.02) mm (p = 0.022) during braking. In 15 subjects (75%) there was no change in ONSD at all. CONCLUSIONS: ONSD and thereby ICP increases during deceleration of a transporting vehicle in participants in supine position. Raising the headrest of the gurney to 30 degrees reduces the effect of breaking on ICP.

Increase in intracranial pressure by application of a rigid cervical collar: a pilot study in healthy volunteers.

OBJECTIVES: Rigid cervical collars are known to increase intracranial pressure (ICP) in severe traumatic brain injury (TBI). Cerebral blood flow might decrease according to the Kellie Monroe doctrine. For this reason, the use of the collar in patients with severe TBI has been abandoned from several trauma protocols in the Netherlands. There is no evidence on the effect of a rigid collar on ICP in patients with mild or moderate TBI or indeed patients with no TBI. As a first step we tested the effect in healthy volunteers with normal ICPs and intact autoregulation of the brain. METHODS: In this prospective blinded cross-over study, we evaluated the effect of application of a rigid cervical collar in 45 healthy volunteers by measuring their optical nerve sheath diameter (ONSD) by transocular sonography. Sonographic measurement of the ONSD behind the eye is an indirect noninvasive method to estimate ICP and pressure changes. RESULTS: We included 22 male and 23 female volunteers. In total 360 ONSD measurements were performed in these 45 volunteers. Application of a collar resulted in a significant increase in ONSD in both the left (ß=0.06, 95% confidence interval: 0.05-0.07, P<0.001) and the right eye (ß=0.01, 95% confidence interval: 0.00-0.02, P=0.027) CONCLUSION: Application of a rigid cervical collar significantly increases the ONSD in healthy volunteers with intact cerebral autoregulation. This suggests that ICP may increase after application of a collar. In healthy volunteers, this seems to be of minor importance. On the basis of our findings the effect of a collar on ONSD and ICP in patients with mild and moderate TBI needs to be determined.