Argyro Zoumprouli

Monitoring of spinal cord perfusion pressure in acute spinal cord injury: initial findings of the injured spinal cord pressure evaluation study*.

Objectives:To develop a technique for continuously monitoring intraspinal pressure at the injury site (intraspinal pressure) after traumatic spinal cord injury. Design:A pressure probe was placed subdurally at the injury site in 18 patients who had isolated severe traumatic spinal cord injury (American Spinal Injuries Association grades A–C). Intraspinal pressure monitoring started within 72 hours of the injury and continued for up to a week. In four patients, additional probes were inserted to simultaneously monitor subdural pressure below the injury and extradural pressure. Blood pressure was recorded from a radial artery catheter kept at the same horizontal level as the injured segment of the spinal cord. We determined the effect of various maneuvers on spinal cord perfusion pressure and spinal cord function and assessed using a limb motor score and motor-evoked potentials. Setting:Neurosurgery and neuro-ICU covering a 3 million population in London. Subjects:Patients with severe traumatic spinal cord injury. Control subjects without spinal cord injury (to monitor spinal cerebrospinal fluid signal and motor evoked potentials). Interventions:Insertion of subdural spinal pressure probe. Measurements and Main Results:There were no procedure-related complications. Intraspinal pressure at the injury site was higher than subdural pressure below the injury or extradural pressure. Average intraspinal pressure from the 18 patients with traumatic spinal cord injury was significantly higher than average intraspinal pressure from 12 subjects without traumatic spinal cord injury. Change in arterial PCO2, change in sevoflurane dose, and mannitol administration had no significant effect on intraspinal pressure or spinal cord perfusion pressure. Increase in inotrope dose significantly increased spinal cord perfusion pressure. Bony realignment and laminectomy did not effectively lower intraspinal pressure. Laminectomy was potentially detrimental by exposing the swollen spinal cord to compression forces applied to the skin. By intervening to increase spinal cord perfusion pressure, we could increase the amplitude of motor-evoked potentials recorded from below or just above the injury level in nine of nine patients with traumatic spinal cord injury. In two of two patients with American Spinal Injuries Association grade C traumatic spinal cord injury, higher spinal cord perfusion pressure correlated with increased limb motor score. Conclusions:Our findings provide proof-of-principle that subdural intraspinal pressure at the injury site can be measured safely after traumatic spinal cord injury.

Expansion duroplasty improves intraspinal pressure, spinal cord perfusion pressure, and vascular pressure reactivity index in patients with traumatic spinal cord injury: injured spinal cord pressure evaluation study.

Abstract We recently showed that, after traumatic spinal cord injury (TSCI), laminectomy does not improve intraspinal pressure (ISP), spinal cord perfusion pressure (SCPP), or the vascular pressure reactivity index (sPRx) at the injury site sufficiently because of dural compression. This is an open label, prospective trial comparing combined bony and dural decompression versus laminectomy. Twenty-one patients with acute severe TSCI had re-alignment of the fracture and surgical fixation; 11 had laminectomy alone (laminectomy group) and 10 had laminectomy and duroplasty (laminectomy+duroplasty group). Primary outcomes were magnetic resonance imaging evidence of spinal cord decompression (increase in intradural space, cerebrospinal fluid around the injured cord) and spinal cord physiology (ISP, SCPP, sPRx). The laminectomy and laminectomy+duroplasty groups were well matched. Compared with the laminectomy group, the laminectomy+duroplasty group had greater increase in intradural space at the injury site and more effective decompression of the injured cord. In the laminectomy+duroplasty group, ISP was lower, SCPP higher, and sPRx lower, (i.e., improved vascular pressure reactivity), compared with the laminectomy group. Laminectomy+duroplasty caused cerebrospinal fluid leak that settled with lumbar drain in one patient and pseudomeningocele that resolved completely in five patients. We conclude that, after TSCI, laminectomy+duroplasty improves spinal cord radiological and physiological parameters more effectively than laminectomy alone.

Variability in the Treatment of Acute Spinal Cord Injury in the United Kingdom: Results of a National Survey

The aim of this study was to examine how traumatic spinal cord injury is managed in the United Kingdom via a questionnaire survey of all neurosurgical units. We contacted consultant neurosurgeons and neuroanesthetists in all neurosurgical centers that manage patients with acute spinal cord injury. Two clinical scenarios-of complete and incomplete cervical spinal cord injuries-were given to determine local treatment policies. There were 175 responders from the 33 centers (36% response rate). We ascertained neurosurgical views on urgency of transfer, timing of surgery, nature and aim of surgery, as well as neuroanesthetic views on type of anesthetic, essential intraoperative monitoring, drug treatment, and intensive care management. Approximately 70% of neurosurgeons will admit patients with incomplete spinal cord injury immediately, but only 40% will admit patients with complete spinal cord injury immediately. There is no consensus on the timing or even the role of surgery for incomplete or complete injuries. Most (96%) neuroanesthetists avoid anesthetics known to elevate intracranial pressure. What was deemed essential intraoperative monitoring, however, varied widely. Many (22%) neuroanesthetists do not routinely measure arterial blood pressure invasively, central venous pressure (85%), or cardiac output (94%) during surgery. There is no consensus among neuroanesthetists on the optimal levels of arterial blood pressure, or oxygen and carbon dioxide partial arterial pressure. We report wide variability among U.K. neurosurgeons and neuroanesthetists in their treatment of acute traumatic spinal cord injury. Our findings reflect the lack of Class 1 evidence that early surgical decompression and intensive medical management of patients with spinal cord injury improves neurological outcome.

Microdialysis to optimize cord perfusion and drug delivery in spinal cord injury

There is lack of monitoring from the injury site to guide management of patients with acute traumatic spinal cord injury. Here, we describe a bedside microdialysis monitoring technique for optimizing spinal cord perfusion and drug delivery at the injury site.

Intraspinal pressure and spinal cord perfusion pressure after spinal cord injury: an observational study

OBJECT In contrast to intracranial pressure (ICP) in traumatic brain injury (TBI), intraspinal pressure (ISP) after traumatic spinal cord injury (TSCI) has not received the same attention in terms of waveform analysis. Based on a recently introduced technique for continuous monitoring of ISP, here the morphological characteristics of ISP are observationally described. It was hypothesized that the waveform analysis method used to assess ICP could be similarly applied to ISP. METHODS Data included continuous recordings of ISP and arterial blood pressure (ABP) in 18 patients with severe TSCI. RESULTS The morphology of the ISP pulse waveform resembled the ICP waveform shape and was composed of 3 peaks representing percussion, tidal, and dicrotic waves. Spectral analysis demonstrated the presence of slow, respiratory, and pulse waves at different frequencies. The pulse amplitude of ISP was proportional to the mean ISP, suggesting a similar exponential pressure-volume relationship as in the intracerebral space. The interaction between the slow waves of ISP and ABP is capable of characterizing the spinal autoregulatory capacity. CONCLUSIONS This preliminary observational study confirms morphological and spectral similarities between ISP in TSCI and ICP. Therefore, the known methods used for ICP waveform analysis could be transferred to ISP analysis and, upon verification, potentially used for monitoring TSCI patients.

Metabolic profile of injured human spinal cord determined using surface microdialysis.

The management of patients having traumatic spinal cord injury would benefit from understanding and monitoring of spinal cord metabolic states. We hypothesized that the metabolism of the injured spinal cord could be visualized using Kohonen self‐organizing maps. Sixteen patients with acute, severe spinal cord injuries were studied. Starting within 72 h of the injury, and for up to a week, we monitored the injury site hourly for tissue glucose, lactate, pyruvate, glutamate, and glycerol using microdialysis as well as intraspinal pressure and spinal cord perfusion pressure. A Kohonen map, which is an unsupervised, self‐organizing topology‐preserving neural network, was used to analyze 3366 h of monitoring data. We first visualized the different spinal cord metabolic states. Our data show that the injured cord assumes one or more of four metabolic states. On the basis of their metabolite profiles, we termed these states near‐normal, ischemic, hypermetabolic, and distal. We then visualized how patients’ intraspinal pressure and spinal cord perfusion pressure affect spinal cord metabolism. This revealed that for more than 60% of the time, spinal cord metabolism is patient‐specific; periods of high intraspinal pressure or low perfusion pressure are not associated with specific spinal cord metabolic patterns. Finally, we determined relationships between spinal cord metabolism and neurological status. Patients with complete deficits have shorter periods of near‐normal spinal cord metabolic states (7 ± 4% vs. 58 ± 12%, p < 0.01, mean ± standard error) and more variable injury site metabolic responses (metabolism spread in 70 ± 11 vs. 40 ± 6 hexagons, p < 0.05), compared with patients who have incomplete neurological deficits. We conclude that Kohonen maps allow us to visualize the metabolic responses of the injured spinal cord and may thus aid us in treating patients with acute spinal cord injuries.

Modified acrylic cranioplasty for large cranial defects

OBJECTIVE To describe a novel technique for constructing polymethylmethacrylate (acrylic) cranioplasty to repair large cranial defects. METHODS A rim of bone is cut from the edge of the skull defect using a craniotome. This bony rim provides a scaffold to fashion the acrylic cement away from the patient thus avoiding thermal injury to the brain. The inner edge of the bony rim is drilled circumferencially to form a groove. Acrylic is then used to fill the defect in the bony rim with continuous manipulation of the paste from both sides to form a dome in the shape of the skull. The groove allows the edge of the acrylic dome to fit snugly with the bony rim thus avoiding sinking. The final cranioplasty, comprised of the hardened acrylic dome with the surrounding bone rim, is firmly attached to the skull with bioplates. RESULTS We used the modified acrylic cranioplasty technique in three patients. Modified acrylic cranioplasty is cheaper and immediately available, compared with ten cases of titanium cranioplasty, with similar cosmetic outcome, intraoperative blood loss and operating theatre time. CONCLUSION Our technique is quick and easy to perform, avoids thermal injury to the brain and produces a strong implant with excellent cosmesis even with large bony defects.

Spinal cord blood flow in patients with acute spinal cord injuries

The effect of traumatic spinal cord injury (TSCI) on spinal cord blood flow (SCBF) in humans is unknown. Whether intervention to achieve the recommended mean arterial pressure (MAP) guideline of 85-90 mm Hg improves SCBF is also unclear. Here, we use laser speckle contrast imaging intraoperatively to visualize blood flow at the injury site in 22 patients with acute, severe spinal cord injuries (American Spinal Injuries Association Impairment Scale, grades A-C). In 17 of 22 patients, injury-site metabolism was also monitored with a microdialysis catheter placed intradurally on the surface of the injured cord. We observed three different SCBF patterns, characterized by distinct injury-site metabolic signatures, which we term necrosis-penumbra, hyperperfusion, and patchy-perfusion. The necrosis-penumbra pattern, only observed in thoracic injuries, had a core of low blood flow (necrosis) with regions of intermediate blood flow on either side (penumbra). The hyperperfusion pattern, only observed in cervical injuries, had very high blood flow throughout the injury site. The patchy-perfusion pattern, found in cervical and thoracic injuries, had irregular regions of low, intermediate, and high blood flow. Though intervention to increase MAP by 20 mm Hg increased overall blood flow at the injury site, in 5 of 22 patients, blood flow increased in some regions, but, surprisingly, decreased in other regions. We term this phenomenon blood pressure-induced local steal. In 7 of 19 patients with MAP 85-90 mm Hg, parts of the injury site were only perfused in systole, but not in diastole, which we term diastolic ischemia. We conclude that acute, severe TSCI produces three pathological blood flow patterns at the injury site. Intervention to increase blood pressure may elicit potentially detrimental SCBF responses in some patients.

Waveform Analysis of Intraspinal Pressure After Traumatic Spinal Cord Injury: An Observational Study (O-64)

Following a traumatic brain injury (TBI), intracranial pressure (ICP) increases, often resulting in secondary brain insults. After a spinal cord injury, here the cord may be swollen, leading to a local increase in intraspinal pressure (ISP). We hypothesised that waveform analysis methodology similar to that used for ICP after TBI may be applicable for the monitoring of patients with spinal cord injury.An initial cohort of 10 patients with spinal cord injury, as presented by the first author at a meeting in Cambridge in May 2012, were included in this observational study. The whole group (18 patients) was recently presented in the context of clinically oriented findings (Werndle et al., Crit Care Med, 42(3):646-655, 2014, PMID: 24231762). Mean pressure, pulse and respiratory waveform were analysed along slow vasogenic waves.Slow, respiratory and pulse components of ISP were characterised in the time and frequency domains. Mean ISP was 22.5 ± 5.1, mean pulse amplitude 1.57 ± 0.97, mean respiratory amplitude 0.65 ± 0.45 and mean magnitude of slow waves (a 20-s to 3-min period) was 3.97 ± 3.1 (all in millimetres of mercury). With increasing mean ISP, the pulse amplitude increased in all cases. This suggests that the ISP signal is of a similar character to ICP recorded after TBI. Therefore, the methods of ICP analysis can be helpful in ISP analysis.