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Table 1 Comparison of brain and spinal cord physiological parameters

From: Spinal cord injury: is monitoring from the injury site the future?

Brain parameter

Spinal cord parameter

Similarities

Differences

Reference

Intracranial pressure (ICP)

Intraspinal pressure (ISP)

ICP and ISP waveforms similar with same three peaks and similar Fourier transforms

Injury site ISP > ISP above or below, but ICP similar throughout. ICP but not ISP reduced with mannitol or hyperventilation.

[13, 17, 35, 44]

Cerebral perfusion pressure (CPP) = MAP – ICP

Spinal cord perfusion pressure (SCPP) = MAP – ISP

CPP and SCPP waveforms similar. CPP and SCPP can be increased with vasopressors

SCPP at injury site differs from SCPP above or below, but CPP similar in brain

[13, 17, 35, 44]

Optimum cerebral perfusion pressure (CPPopt)

Optimum spinal cord perfusion pressure (SCPPopt)

U-shape PRx vs CPP, sPRx vs SCPP. Minimum is CPPopt or SCPPopt. CPPopt and SCPPopt individualized

Overall CPPopt ~75 mmHg whereas overall SCPPopt ~90 mmHg

[13, 14, 17, 35, 44]

Pressure reactivity index (PRx)

Spinal Pressure reactivity index (sPRx)

Running correlation between MAP and ICP/ISP

PRx is global, but sPRx is for injury site

[13, 14, 35, 44]

Compensatory volume reserve (RAP)

Spinal compensatory volume reserve (sRAP)

Running correlation between mean ICP/ISP and ICP/ISP pulse amplitude

RAP is global, but sRAP is for injury site

[13, 14, 35, 44]