Postural Influence on Intracranial and Cerebral Perfusion Pressure in Ambulatory Neurosurgical Patients
Highlights
- nd therefore assumed to be negative within the ain (32). ICP depends on the volume of cerebral blood and F for which the vascular component is influenced by sysmic blood pressure, modified by cerebral autoregulation and nous outflow resistance (12), while the CSF component is scribed by Davson’s equation (13) as a balance between CSF rmation, CSF (Page 1)
- ous pressure in the ... toregulation and systemic blood pressure regulation, po (Page 1)
- During head-down tilt, ICPMidbrain increased corresponding a hydrostatic fluid pressure from a column of some 35 cm, ., with a reference just w the heart and corresponding to e location of the HIPvein (31). It therefore seems that, given (Page 3)
- system, the pressure is transmitted to the brain. nversely, the decrease in ICP during head-up tes ove 20° was attenuated and when upright, ICPMidbrain corated to a fluid column of only 12–15 cm, likely reflecting the e of internal jugular venous collapse (14, 18; Fig. 2) and rresponding to where CSF pressure is considered to be zero 4). Had the veins remained open, I (Page 3)
- pected to reach more negative values (ICPExpected; Fig. 1). In e supine position, the internal jugular veins constitute the in upright imary route of drainage from the brain, but stures these veins respond to the decreasing transmural essure and collapse thus acting as Starling resistors (20). rebral drainage thereby depends increasingly on alternative thways such as the vertebral venous system (18, 39, 43), ich is believed to remain open and thus could constitute a ntinuous hydrostatic fluid column and support rather large gative pressures (2, 5). Furthermore, in the standing positi (Page 3)
- F is displaced from the skull to the spinal compartment (25). hile both displacement of CSF and pressure of alternative nous systems is likely to play a role for ICP, we consider m the present data that overall positional ICP is governed edominantly by pressure in the venous sinus, which is in turn fluenced by pressure in the internal jugular veins. Collapse of ck veins in upright postures, i.e., the internal jugular veins, erefore, seems to counter (Page 3)
- predicted by the ight of the assumed hydrostatic gradient. During head-down t, the increase in ICP was greater than the decrease caused by ad-up tilt suggesting formation of a smaller hydrostatic adient possibly caused by collapse of major neck veins. gulation of systemic (Page 3)
- . 2. Hydrostatic pressure gradient according to ICP at different angles of tilt. ring head-up tilt, ICP corresponded to a hydrostatic gradient with reference the base of the skull, likely reflecting the site of venous collapse, while ring head-down tilt the increase in ICP corresponded to a hydrostatic ssure gradient with reference to just (Page 3)
- P is tightly regulated within a ran (Page 4)
Postural Influence on Intracranial and Cerebral Perfusion Pressure in Ambulatory Neurosurgical Patients
Highlights
- nd therefore assumed to be negative within the ain (32). ICP depends on the volume of cerebral blood and F for which the vascular component is influenced by sysmic blood pressure, modified by cerebral autoregulation and nous outflow resistance (12), while the CSF component is scribed by Davson’s equation (13) as a balance between CSF rmation, CSF (Page 1)
- ous pressure in the ... toregulation and systemic blood pressure regulation, po (Page 1)
- During head-down tilt, ICPMidbrain increased corresponding a hydrostatic fluid pressure from a column of some 35 cm, ., with a reference just w the heart and corresponding to e location of the HIPvein (31). It therefore seems that, given (Page 3)
- system, the pressure is transmitted to the brain. nversely, the decrease in ICP during head-up tes ove 20° was attenuated and when upright, ICPMidbrain corated to a fluid column of only 12–15 cm, likely reflecting the e of internal jugular venous collapse (14, 18; Fig. 2) and rresponding to where CSF pressure is considered to be zero 4). Had the veins remained open, I (Page 3)
- pected to reach more negative values (ICPExpected; Fig. 1). In e supine position, the internal jugular veins constitute the in upright imary route of drainage from the brain, but stures these veins respond to the decreasing transmural essure and collapse thus acting as Starling resistors (20). rebral drainage thereby depends increasingly on alternative thways such as the vertebral venous system (18, 39, 43), ich is believed to remain open and thus could constitute a ntinuous hydrostatic fluid column and support rather large gative pressures (2, 5). Furthermore, in the standing positi (Page 3)
- F is displaced from the skull to the spinal compartment (25). hile both displacement of CSF and pressure of alternative nous systems is likely to play a role for ICP, we consider m the present data that overall positional ICP is governed edominantly by pressure in the venous sinus, which is in turn fluenced by pressure in the internal jugular veins. Collapse of ck veins in upright postures, i.e., the internal jugular veins, erefore, seems to counter (Page 3)
- predicted by the ight of the assumed hydrostatic gradient. During head-down t, the increase in ICP was greater than the decrease caused by ad-up tilt suggesting formation of a smaller hydrostatic adient possibly caused by collapse of major neck veins. gulation of systemic (Page 3)
- . 2. Hydrostatic pressure gradient according to ICP at different angles of tilt. ring head-up tilt, ICP corresponded to a hydrostatic gradient with reference the base of the skull, likely reflecting the site of venous collapse, while ring head-down tilt the increase in ICP corresponded to a hydrostatic ssure gradient with reference to just (Page 3)
- P is tightly regulated within a ran (Page 4)