Introduction: There is no monitoring from the injured spinal cord to define the optimal values of physiological parameters in ICU. We present a technique for continuously monitoring intraspinal pressure (ISP) and spinal cord perfusion pressure (SCPP).
Methods: A pressure probe was placed intradurally at the injury site in 18 patients with severe (AIS A-C) traumatic spinal cord injury (TSCI) . ISP monitoring started within 72 hours of the injury and continued for up to a week. Additional probes were inserted to monitor intradural pressure below the injury and extradural pressure. We determined the effect of various manoeuvres on spinal cord perfusion pressure (SCPP = mean arterial pressure – ISP) and spinal cord function. We also quantified spinal cord vascular reactivity at the injury site (sPRx), as the running correlation coefficient between mean ISP and arterial blood pressure.
Results: There were no procedure-related complications. ISP at the injury site was higher than intradural pressure below or extradural pressure. Mean ISP from the 18 TSCI patients was higher than mean ISP from 12 subjects without TSCI (20 vs. 7 mmHg, P<0.005). Change in arterial pCO2, change in sevoflurane and mannitol administration had no significant effect on ISP or SCPP. Increase in inotropes increased SCPP by 30 mmHg (P<0.005). Laminectomy did not effectively lower ISP. Laminectomy was potentially detrimental by exposing the swollen cord to compression forces applied to the skin. There was a U-shaped relationship between sPRx and SCPP with minimum sPRx at SCPP (SCPPopt) that varied widely between patients (60 – 120 mmHg). By increasing SCPP, we could increase the amplitude of MEPs recorded from below or just above the injury level. In cervical AIS C patients, higher SCPP correlated with increased limb motor score.
Conclusions: ISP at the injury site can be measured safely after TSCI. The optimum SCPP varies amongst TSCI patients.
Patient Care: The technique described allows monitoring and optimization of intraspinal pressure and spinal cord perfusion pressure after spinal cord injury to reduce secondary injury and improve outcome.
Learning Objectives: By the conclusion of this session, participants should be able to:
1) Define intraspinal pressure (ISP), spinal cord perfusion pressure (SCPP) and spinal pressure reactivity index (sPRx) in spinal cord injury.
2) Understand the technique of monitoring ISP, SCPP and sPRx.
3) Describe the effect of different manoeuvres on ISP and SCPP.
References: 1. Werndle MC, Zoumprouli A, Sedgwick P, Papadopoulos MC. Variability in the treatment of acute spinal cord injury in the United Kingdom. J Neurotrauma 2012;29:880-8.
2. Werndle MC, Saadoun S, Phang I, Czosnyka M, Varsos GV, Czosnyka ZH, Smielewski P, Jamous A, Bell BA, Zoumprouli A, Papadopoulos MC. Monitoring of spinal cord perfusion pressure in acute spinal cord injury. Crit Care Med 2014;42:646-55.