Biomechanical investigation of lumbar hybrid stabilization in two-level posterior instrumentation.

PURPOSE: Hybrid stabilization with a dynamic implant has been suggested to avoid adjacent segment disease by creating a smoother transition zone from the instrumented segments to the untreated levels above. This study aims to characterize the transition zones of two-level posterior instrumentation strategies for elucidating biomechanical differences between rigid fixation and the hybrid stabilization approach with a pedicle screw-based dynamic implant. METHODS: Eight human lumbar spines (L1-5) were loaded in a spine tester with pure moments of 7.5 Nm and with a hybrid loading protocol. The range of motion (ROM) of all segments for both loading protocols was evaluated and normalized to the native ROM. RESULTS: For pure moment loading, ROM of the segments cranial to both instrumentations were not affected by the type of instrumentation (p > 0.5). The dynamic instrumentation in L3-4 reduced the ROM compared to intact (p < 0.05) but allowed more motion than the rigid fixation of the same segment (p < 0.05). Under hybrid loading testing, the cranial segments (L1-2, L2-3) had a significant higher ROM for both instrumentations compared to the intact (p < 0.05). Comparing the two instrumentations with each other, the rigid fixation resulted in a higher increased ROM of L1-2 and L2-3 than hybrid stabilization. CONCLUSIONS: Regardless of the implant, two-level posterior instrumentation was accompanied by a considerable amount of compensatory movement in the cranial untreated segments under the hybrid protocol. Hybrid stabilization, however, showed a significant reduction of this compensatory movement in comparison to rigid fixation. These results could support the surgical strategy of hybrid stabilization, whereas the concept of topping-off, including a healthy segment, is discouraged.

The significance of direct transportation to a trauma center on survival for severe traumatic brain injury.

INTRODUCTION: While timely specialized care can contribute to improved outcomes following traumatic brain injury (TBI), this condition remains the most common cause of post-injury death worldwide. The purpose of this study was to investigate the difference in mortality between regional trauma centers in Sweden (which provide neurosurgical services round the clock) and non-trauma centers, hypothesizing that 1-day and 30-day mortality will be lower at regional trauma centers. PATIENTS AND METHODS: This retrospective cohort study used data extracted from the Swedish national trauma registry and included adults admitted with severe TBI between January 2014 and December 2018. The cohort was divided into two subgroups based on whether they were treated at a trauma center or non-trauma center. Severe TBI was defined as a head injury with an AIS score of 3 or higher. Poisson regression analyses with both univariate and multivariate models were performed to determine the difference in mortality risk [Incidence Rate Ratio (IRR)] between the subgroups. As a sensitivity analysis, the inverse probability of treatment weighting (IPTW) method was used to adjust for the effects of confounding. RESULTS: A total of 3039 patients were included. Patients admitted to a trauma center had a lower crude 30-day mortality rate (21.7 vs. 26.4% days, p = 0.006). After adjusting for confounding variables, patients treated at regional trauma center had a 28% [adj. IRR (95% CI): 0.72 (0.55-0.94), p = 0.015] decreased risk of 1-day mortality and an 18% [adj. IRR (95% CI): 0.82 (0.69-0.98)] reduction in 30-day mortality, compared to patients treated at a non-trauma center. After adjusting for covariates in the Poisson regression analysis performed after IPTW, admission and treatment at a trauma center were associated with a 27% and 17% reduction in 1-day and 30-day mortality, respectively. CONCLUSION: For patients suffering a severe TBI, treatment at a regional trauma center confers a statistically significant 1-day and 30-day survival advantage over treatment at a non-trauma center.

Mortality risk stratification in isolated severe traumatic brain injury using the revised cardiac risk index.

PURPOSE: Traumatic brain injury (TBI) continues to be a significant cause of mortality and morbidity worldwide. As cardiovascular events are among the most common extracranial causes of death after a severe TBI, the Revised Cardiac Risk Index (RCRI) could potentially aid in the risk stratification of this patient population. This investigation aimed to determine the association between the RCRI and in-hospital deaths among isolated severe TBI patients. METHODS: All adult patients registered in the TQIP database between 2013 and 2017 who suffered an isolated severe TBI, defined as a head AIS ≥ 3 with an AIS ≤ 1 in all other body regions, were included. Patients were excluded if they had a head AIS of 6. The association between different RCRI scores (0, 1, 2, 3, ≥ 4) and in-hospital mortality was analyzed using a Poisson regression model with robust standard errors while adjusting for potential confounders, with RCRI 0 as the reference. RESULTS: 259,399 patients met the study's inclusion criteria. RCRI 2 was associated with a 6% increase in mortality risk [adjusted IRR (95% CI) 1.06 (1.01-1.12), p = 0.027], RCRI 3 was associated with a 17% increased risk of mortality [adjusted IRR (95% CI) 1.17 (1.05-1.31), p = 0.004], and RCRI ≥ 4 was associated with a 46% increased risk of in-hospital mortality [adjusted IRR(95% CI) 1.46 (1.11-1.90), p = 0.006], compared to RCRI 0. CONCLUSION: An elevated RCRI ≥ 2 is significantly associated with an increased risk of in-hospital mortality among patients with an isolated severe traumatic brain injury. The simplicity and bedside applicability of the index makes it an attractive choice for risk stratification in this patient population.

Preserved cognition after deep brain stimulation (DBS) in the subthalamic area for Parkinson's disease: a case report.

At present, subthalamic nucleus (STN) stimulation is the preferred procedure for the amelioration of motor symptoms in medication refractory Parkinson's disease. Results are however impaired by negative impacts on mood, cognition, incentive, and social judgment. Alternative targets are therefore explored. We describe a case with stimulation of subthalamic fibre tracts that showed clear improvement of cognitive and social abilities. Avoiding the STN may be advantageous in progressive Parkinson's disease to avoid non-motor complications and enhance quality of life.

Persistent Iliosacral Joint Syndrome following Instrumentation to the Sacropelvis in Patients with Adult Spinal Deformity.

BACKGROUND AND OBJECTIVE: Persistent sacroiliac joint syndrome (PSIJS) may complicate adult spinal deformity surgery (ASDS). This study assesses the relationship between clinical/morphometric parameters and PSIJS following ASDS including pelvic fixation and the therapeutic efficacy of secondary iliosacral fusion (ISF). METHODS: Perioperative health-related quality of life (HRQOL) outcomes (Oswestry Disability Index, Short Form 12-item health survey, version 2 scores) at 6, 12, and 24 months, and radiographic studies were analyzed retrospectively in a cohort of 71 consecutive patients undergoing ASDS. PSIJS was confirmed in nine individuals (12.7%) by placebo-controlled dual sacroiliac joint (SIJ) blocks. The relationships between global and regional spinopelvic morphometry, PSIJS, and HRQOL outcomes were assessed by logistic regression and receiver operating characteristic curve (ROC) analysis. RESULTS: PSIJS, independently causing significantly reduced improvement in HRQOL scores (p < 0.001) 6 months postoperatively, warranted secondary ISF in nine patients (12.7%) within 12 months of index surgery, without evidence of progressive SIJ arthrosis, pseudarthrosis, or hardware issues. Eight of nine patients undergoing secondary ISF reported≥ 70% pain reduction at 24 months. Logistic regression/ROC analysis revealed a close association between PSIJS and nonharmonious postoperative L4-S1 fractional lordosis (p < 0.0001), pelvic incidence angle > 53 degrees, hip arthrosis, and preexistent advanced SIJ arthrosis (p < 0.01). CONCLUSION: PSIJS may negatively impact the clinical outcome of ASDS. Recurrent preoperative SIJ syndrome requiring interventional treatment, preexisting hip and SIJ arthrosis, insufficient restoration of L4-S1 fractional lordosis, and high pelvic incidence predispose to PSIJS. PSIJS may potentially be avoided by restoring physiologic lumbosacral geometry and S2 sacral alar-iliac screw fixation during index surgery. Secondary ISF appears to be effective in reducing pain and physical impairment due to PSIJS.

Malpractice claims in spine surgery in Germany: a 5-year analysis.

STUDY DESIGN: Retrospective analysis of anonymized malpractice claims. SUMMARY OF BACKGROUND DATA: Spine surgery is considered a high-risk specialty with regards to malpractice claims. However, limited data is available for Germany. We analyzed the rate, subject, and legal outcome of malpractice claims faced by spine surgeons in one of the largest Medical Council coverage areas in Germany, representing 60,000 physicians and a population of 10 million. METHODS: Analysis of all malpractice claims regarding spinal surgeries completed by the Review Board of the North Rhine Medical Council (NRMC) from 2012 to 2016. Claim merit, content, and actual treatment errors were reviewed. Severity of damage was graded from negligible (1) to death (6). RESULTS: A total of 8,381 malpractice cases were reviewed by the NRMC from 2012 to 2016. Four percent (340 cases: 181 females, 159 males) pertained to patients undergoing spinal surgery with 94.7% of patients undergoing inhospital treatment and 5.3% as outpatients. Malpractice claims most frequently involved neurosurgery (48.5%) and orthopedic surgery (37.6%). Trauma surgery was involved in 9.1% and other specialties in 4.8%. Actual treatment errors were found in 89 of 340 cases (26.2%).Of those, 81 resulted in treatment-associated health impairment. Negligible and/or temporary impairment was found in 49.3%. Negligible to moderate but permanent damage was observed in 39.5%. Nine patients suffered severe permanent damage or death (11.1%). The treated diagnosis was degenerative disc disease in 34 patients (41.9%), spinal canal stenosis in 13 (16%), vertebral body fractures in 10 (12.3%), spondylolisthesis in 6 (7.4%), and other diagnoses accounting for the remaining 18 (22.2%). Errors involved actual surgical treatment in 40.7%, surgical indication and preoperative workup in 28.4%, postoperative treatment in 25.9%, and patient consent in 4.9%. CONCLUSIONS: Spinal surgery claims account for 4% of all claims reviewed by the NRMC in the 5-year period from 2012 to 2016. Eighty-nine (26.2%) were deemed justified. The majority of treatment errors (59.3%) occurred during workup, indication and consent, or during postoperative care. Errors during actual surgery were responsible for 40.7% of all treatment-associated damages. Understanding the distribution and content of claims is key to improving patient satisfaction not only by honing surgical skills, but also by improving pre- and postoperative communication and care.

Radiological and Clinical Outcome after Multilevel Anterior Cervical Discectomy and/or Corpectomy and Fixation.

BACKGROUND: Multilevel anterior cervical decompression and fixation of four and more levels is a common surgical procedure used for several diseases. METHODS: We reviewed the radiological and clinical outcomes after anterior cervical discectomy or corpectomy and fixation of four and more levels in 85 patients (55 men and 30 women) with an average age of 59.6 years. Surgical indication was multilevel cervical degenerative myelopathy and radiculopathy in 72 (85%) patients, multilevel cervical spondylodiscitis in four (5%), complex traumatic cervical fractures in four (5%), metastatic cervical spine tumor in two (2%), and ossification of the posterior longitudinal ligament in three (3%) patients. RESULTS: There were no severe intraoperative complications such as spinal cord or vertebral artery injury or dissection. Seventy-three patients had four, 10 patients had five, and two patients had six anterior cervical level fixations. The visual analog scale (VAS) and Japanese Orthopedic Association (mJOA) scale scores improved (6.9 to 1.3 (p < 0.001) and 13.9 to 16.5 (p < 0.001), respectively). The Cobb angle increased from 5.7° to 17.6° postoperatively (p < 0.001). Secondary posterior fixation was necessary in three cases due to pseudarthrosis. CONCLUSION: The anterior approach appears to be optimal for ventral compressive pathology and lordosis restoration to the cervical spine. Limitations of multiple level decompression and fixation included increasing pseudoarthrosis rates, especially after corpectomy, and increasing fused level numbers.

Percutaneous multilevel decompressive laminectomy, foraminotomy, and instrumented fusion for cervical spondylotic radiculopathy and myelopathy: assessment of feasibility and surgical technique.

OBJECT: Extensive muscle dissection associated with conventional dorsal approaches to the cervical spine frequently results in local pain, muscle wasting, and temporarily painful and restricted neck movement. The utility of a percutaneous muscle-sparing access technique and specifically modified instrumentation for multilevel posterior cervical decompression and fusion were evaluated. METHODS: Eleven patients (six men, five woman; mean age 72.8 +/- 6.3 years) presenting with refractory neck pain and progressive multilevel cervical radiculopathy and/or myelopathy due to cervical spondylosis with spinal canal and neural foraminal stenosis underwent multilevel laminectomy, foraminotomy, and subsequent instrumented posterior fusion via bilateral or unilateral percutaneous muscle dilation approaches. A novel cannulated polyaxial instrumentation system was used for unilateral transpedicular/translaminar fixation. RESULTS: Significant reduction of Neck Disability Index and Nurick Scale scores and partial or complete recovery of upper extremity radicular deficits was observed during follow-up (mean 14.6 months). Mean procedural blood loss was 45.5 ml, and mean length of stay in hospital was 5.7 days. Fusion was demonstrated in 10 patients between 12 and 14 months postoperatively. Operative exposure and instrumentation were significantly facilitated by specific modifications of retractor/access port systems, surgical instruments, and implants. CONCLUSIONS: Muscle sparing posterior decompression and instrumented fusion constitutes a safe and effective surgical option in a selected subgroup of patients with multilevel cervical spondylotic radiculomyelopathy. Specific modifications in surgical technique, instrumentation, and implants are mandatory for effective achievement of the surgical goals. The use of refined image guidance technology and intraoperative imaging can further improve surgical safety and efficacy.

Clinical features, microsurgical treatment, and outcome of vestibular schwannoma with brainstem compression.

BACKGROUND: Presenting symptoms, treatment considerations, and outcome are strongly related to the extension of vestibular schwannomas (VS). The aim of the current retrospective study was to analyze the clinical features, microsurgical treatment, and outcome of VS with brainstem compression. METHODS: Forty-nine patients presented with VS (Hannover grading scale T4a or T4b) in our department. A subgroup analysis was performed among patients without (T4a) and with (T4b) compression and dislocation of the fourth ventricle. RESULTS: Patients with type T4b VS presented significantly more often with long tract signs/ataxia (P < 0.05), tonsillar herniation (P < 0.001), and preoperative hydrocephalus (P < 0.01). No significant difference was found between the groups regarding hearing loss and facial nerve, trigeminal nerve, and lower cranial nerve function. Gross total resection was achieved in 83% of the cases, near total resection was achieved in 15% of the cases, and subtotal resection was performed in 2% of the cases. One patient died after massive postoperative bleeding caused by a coagulopathy. At last follow-up, 69% of the patients had excellent facial nerve function (Grade I-II) and the remaining 31% a fair outcome. Six patients (12%) required permanent ventriculoperitoneal shunting. Hearing was preserved in two patients. Forty-six patients (94%) were independent without occasional assistance (Karnofsky scale 70-100%). CONCLUSIONS: VS with brainstem compression is frequently associated with hydrocephalus, ataxia, long tract signs, multiple cranial nerve disorders, and occasionally, signs of intracranial hypertension. Primary microsurgical resection is an appropriate management option for large VS.

Tako-tsubo cardiomyopathy: reversible heart failure with favorable outcome in patients with intracerebral hemorrhage. Case report.

In patients with intracerebal hemorrhage, cardiac dysfunction is a common phenomenon. Tako-tsubo cardiomyopathy is characterized by complete reversibility and therefore may constitute an entity with a favorable outcome. In this case report the authors describe a previously healthy 23-year-old man with no history of cardiac disease who suffered a severe fourth ventricular hemorrhage due to an angioma of the vermis cerebelli. After emergency surgery, progressive tachycardia, fibrillation, and electromechanical decoupling developed in the patient. An echocardiogram revealed left ventricular apical akinesia and basal hyperkinesis characteristic of tako-tsubo cardiomyopathy. One week after admission, cardiac function was normal. Tako-tsubo cardiomyopathy differs from common cardiac dysfunction in its reversible nature. This characteristic must be taken into consideration when treating patients with intracerebral hemorrhage to avoid misclassification of the disease.

The effects of stimulation pattern and sevoflurane concentration on intraoperative motor-evoked potentials.

The usefulness of intraoperative monitoring of motor-evoked potentials (MEPs) during inhaled anesthesia is limited by the suppressive effects of volatile anesthetics on MEP signals. We investigated the effects of different stimulation patterns and end-tidal concentrations of sevoflurane on intraoperative transcranial electrical MEPs. In 12 patients undergoing craniotomy, stimulation patterns (300-500 V, 100-1000 Hz, 1-5 stimuli) and multiples (0.5, 0.75, and 1.0) of minimum alveolar concentration (MAC) of sevoflurane were varied randomly while remifentanil was administered at a constant rate of 0.2 microg x kg(-1) x min(-1). MEPs were recorded from thenar and hypothenar muscles and analyzed without knowledge of the respective MAC. Three-way analysis of variance revealed significant main effects for increasing stimulation intensity, frequency, and number of stimuli on MEP amplitude (P < 0.05). Maximum MEP amplitudes and recording success rates were observed during 4 stimuli delivered at 1000 Hz and 300 V. A significant main effect of sevoflurane concentration (0.5 versus 0.75 and 1 MAC multiple) on MEP amplitude was observed at the thenar recording site only (P < 0.05). In conclusion, MEP characteristics varied significantly with changes in stimulation pattern and less so with changes in sevoflurane concentration. The results suggest that high frequency repetitive stimulation allows intraoperative use of MEP monitoring during up to 1 MAC multiple of sevoflurane and constant infusion of remifentanil up to 0.2 microg x kg(-1) x min(-1).

MASTERS-D Study: A Prospective, Multicenter, Pragmatic, Observational, Data-Monitored Trial of Minimally Invasive Fusion to Treat Degenerative Lumbar Disorders, One-Year Follow-Up.

UNLABELLED: The objective of the study is to assess effectiveness and safety of minimally invasive lumbar interbody fusion (MILIF) for degenerative lumbar disorders (DLD) in daily surgical practice and follow up with patients for one year after surgery. A prospective, multicenter, pragmatic, monitored, international outcome study in patients with DLD causing back/leg pain was conducted (19 centers). Two hundred fifty-two patients received standard of care available in the centers. Patients were included if they were aged >18 years, required one- or two-level lumbar fusion for DLD, and met the criteria for approved device indications. Primary endpoints: time to first ambulation (TFA) and time to surgery recovery (TSR). Secondary endpoints: patient-reported outcomes (PROs)--back and leg pain (visual analog scale), disability (Oswestry Disability Index (ODI)), health status (EQ-5D), fusion rates, reoperation rates, change in pain medication, rehabilitation, return to work, patient satisfaction, and adverse events (AEs). Experienced surgeons (≥30 surgeries pre-study) treated patients with DLD by one- or two-level MILIF and patients were evaluated for one year (NCT01143324). At one year, 92% (233/252) of patients remained in the study. PRIMARY OUTCOMES: TFA, 1.3 ±0.5 days and TSR, 3.2 ±2.0 days. SECONDARY OUTCOMES: Most patients (83.3%) received one level MILIF; one (two-level) MILIF mean surgery duration, 128 (182) min; fluoroscopy time, 115 (154) sec; blood loss, 164 (233) mL; at one year statistically significant (P<.0001) and clinically meaningful changes from baseline were reported in all PROs--reduced back pain (2.9 ±2.5 vs. 6.2 ±2.3 at intake), reduced leg pain (2.2 ±2.6 vs. 5.9 ±2.8), and ODI (22.4% ± 18.6 vs. 45.3% ± 15.3), as well as health-related quality of life (EQ-5D index: 0.71 ±0.28 vs. 0.34 ±0.32). More of the professional workers were working at one year than those prior to surgery (70.3% vs. 55.2%). Three AEs and one serious AE were considered procedure-related; there were no deep site infections or deaths. This is the first study evaluating MILIF for treatment of DLD in daily clinical practice. Clinically significant improvements were observed in all endpoints. Short-term post-surgery improvements (four weeks) were maintained through one year with minimal complications. Our results suggest that MILIF has good-to-excellent outcomes for the treatment of DLD in a broad patient population under different clinical conditions and healthcare delivery systems.

Solitary spinal artery aneurysms as a rare source of spinal subarachnoid hemorrhage: potential etiology and treatment strategy.

Solitary aneurysms of spinal arteries lacking associated vascular malformations are rare. We report three patients with spinal subarachnoid hemorrhage (SAH) due to rupture of such aneurysms, which regressed spontaneously, as confirmed on conventional angiography. One patient had spinal SAH with presumed spontaneous dissection of a segmental artery. In the other two, SAH resulted from ruptured fusiform aneurysms of the artery of Adamkiewicz immediately proximal to the anterior spinal artery. Solitary aneurysms of the spinal arteries appear to be etiopathologic entities completely different from intracranial aneurysms. Spontaneous occlusion seems to be common, justifying a wait-and-see strategy rather than urgent treatment.

Clinical and radiological results after parapedicular screw fixation of the thoracic spine.

OBJECT: The proximity of thoracic pedicles to the spinal cord and neurovascular structures has prompted numerous efforts to obtain proper screw placement. The aim of this study was to evaluate the feasibility and efficacy of thoracic parapedicular (intercostovertebral) screw fixation by following anatomical landmarks and using fluoroscopy. METHODS: Thoracic parapedicular screw fixation was performed in 41 patients (328 screws). Postoperative computerized tomography scans were obtained in all cases to analyze the position of each screw with respect to the pedicle rib unit, the spinal canal, and the vertebral body (VB) according to a proposed novel grading system. Additionally, screw convergence angles were calculated for each instrumented level. There was no additional morbidity associated with parapedicular screw insertion. In a single case a screw suspected of entering the spinal canal was revised without causing neurological damage. The remaining screws were placed entirely within the pedicle rib unit and VB without breaching the neural foramina, pleura, or vascular structures. CONCLUSIONS: Thoracic and thoracolumbar instability can be treated adequately and safely by using parapedicular screw fixation guided by anatomical landmarks and fluoroscopic imaging. The use of computer-aided navigation may be beneficial but does not appear to be mandatory.

Surgical data and early postoperative outcomes after minimally invasive lumbar interbody fusion: results of a prospective, multicenter, observational data-monitored study.

UNLABELLED: Minimally invasive lumbar interbody fusion (MILIF) offers potential for reduced operative morbidity and earlier recovery compared with open procedures for patients with degenerative lumbar disorders (DLD). Firm conclusions about advantages of MILIF over open procedures cannot be made because of limited number of large studies of MILIF in a real-world setting. Clinical effectiveness of MILIF in a large, unselected real-world patient population was assessed in this Prospective, monitored, international, multicenter, observational study. OBJECTIVE: To observe and document short-term recovery after minimally invasive interbody fusion for DLD. MATERIALS AND METHODS: In a predefined 4-week analysis from this study, experienced surgeons (≥ 30 MILIF surgeries pre-study) treated patients with DLD by one- or two-level MILIF. The primary study objective was to document patients' short-term post-interventional recovery (primary objective) including back/leg pain (visual analog scale [VAS]), disability (Oswestry Disability Index [ODI]), health status (EQ-5D) and Patient satisfaction. RESULTS: At 4 weeks, 249 of 252 patients were remaining in the study; the majority received one-level MILIF (83%) and TLIF was the preferred approach (94.8%). For one-level (and two-level) procedures, surgery duration was 128 (182) min, fluoroscopy time 115 (154) sec, and blood-loss 164 (233) mL. Time to first ambulation was 1.3 days and time to study-defined surgery recovery was 3.2 days. Patients reported significantly (P < 0.0001) reduced back pain (VAS: 2.9 vs 6.2), leg pain (VAS: 2.5 vs 5.9), and disability (ODI: 34.5% vs 45.5%), and a significantly (P < 0.0001) improved health status (EQ-5D index: 0.61 vs 0.34; EQ VAS: 65.4 vs 52.9) 4 weeks postoperatively. One adverse event was classified as related to the minimally invasive surgical approach. No deep site infections or deaths were reported. CONCLUSIONS: For experienced surgeons, MILIF for DLD demonstrated early benefits (short time to first ambulation, early recovery, high patient satisfaction and improved patient-reported outcomes) and low major perioperative morbidity at 4 weeks postoperatively.

Implications of vascular endothelial growth factor, sFlt-1, and sTie-2 in plasma, serum and cerebrospinal fluid during cerebral ischemia in man.

The relation between cerebral ischemia and local release of angiogenic factors was investigated after subarachnoid hemorrhage (SAH) in humans. Time-dependent concentration-changes of vascular endothelial growth factor (VEGF), sFlt-1 and sTie-2 extracted from plasma, serum, and cerebrospinal fluid (ventricular, cisternal, and lumbar) were analyzed in 15 patients surgically treated for ruptured aneurysms of the anterior circulation (Hunt and Hess grades I-V). Data were related to brain Po2 (Pbro2) and cerebral energy metabolites (extracellular lactate, pyruvate, glutamate, and glycerin concentrations) as well as clinical and radiologic reference data. Delayed impairment of cerebral perfusion secondary to progressive microcirculatory alterations was associated with reduced local Pbro2 and energy metabolism (increased lactate-pyruvate ratio, glutamate and glycerine levels). Elevated serum/plasma and CSF concentrations of VEGF, sFlt-1, and sTie-2 matched the scale of ischemic tissue hypoxia. Excessive VEGF/sFlt-1 and sTie-2 levels were related to Pbro2 values consistently less than 5 mm Hg, glutamate concentrations greater than 300 micromol/L, lactate-pyruvate ratio greater than 300, cerebral infarction, and reduced outcome (P < 0.01). Delayed microcirculatory impairment was mirrored by distinct elevation of cisternal and arterial VEGF and sFlt-1 concentrations, suggesting local induction of angiogenesis. Arterial levels of VEGF, sFlt-1, and sTie-2 reflect both extent and time course of compensatory, yet clinically inefficient, angiogenesis in the absence of general hypoxia.

Monitoring of cerebral perfusion pressure during intracranial hypertension: a sufficient parameter of adequate cerebral perfusion and oxygenation?

OBJECTIVE: A cerebral perfusion pressure (CPP) oriented treatment is a widely accepted standard for patients with intracranial hypertension. In an animal model of controlled intracranial hypertension we investigated whether CPP is a reliable parameter of sufficient cerebral perfusion and oxygenation. Using near-infrared reflexion spectroscopy the effect of decreasing CPP due to increasing intracranial pressure (ICP) on cerebral tissue oxygenation was studied. METHODS: Ten rabbits were subjected to artificially elevated ICP using the cisterna-magna infusion technique. Regional cerebral O(2) saturation of hemoglobin (tiSO(2)), regional tissue concentration of hemoglobin (tiHb), and CPP were recorded continuously. CPP was investigated with respect to tiSO(2). Electrocortical activity was simultaneously recorded by two-channel EEG to determine the onset of ischemia. RESULTS: Reduced CPP due to increased ICP led to a continuous decrease in tiSO(2.) There was progressive suppression of EEG frequency and amplitude with decreasing CPP in all animals. Onset of EEG-silence due to elevated ICP was observed in a wide range of CPP-values between 9 and 42 mmHg. At the same time tiSO(2) varied merely between 0 and 5%. CONCLUSIONS: Regarding the EEG effects due to increased ICP (EEG silence), CPP values showed a wide interindividual variability, in contrast to tiSO(2). In our animal model the sole calculation of CPP did not reflect adequate cerebral perfusion.

Liquid 2-poly-hydroxyethyl-methacrylate embolization of experimental arteriovenous malformations: feasibility study.

BACKGROUND AND PURPOSE: We investigated the use of 2-poly-hydroxyethyl-methacrylate (2-P-HEMA) as an embolic agent in swine arteriovenous malformations (AVMs). METHODS: In seven mini swine, experimental AVMs were created surgically. The aim of treatment was complete embolization of the nidus compartment filled by the feeding artery, without brain embolization. Six animals received pure liquid 2-P-HEMA, and one, 50% 2-P-HEMA. For radiopacity, liquid 2-P-HEMA was mixed with tungsten powder. Six animals underwent angiographic follow-up within 5-8 mo (mean, 6.5 mo). Evaluation criteria were controllability, procedural reproducibility, and duration of the nidus occlusion. To detect complications, brain MR imaging and CT were performed. Histopathologic studies were performed to prove occlusion and assess histopathologic responses. RESULTS: 2-P-HEMA was easily injected through microcatheters, with a reproducible technique. Because of the radiopacity of the mixture, deep nidus penetration was controlled with fluoroscopy and confirmed with CT and histopathologic examination. In five AVMs embolized with pure 2-P-HEMA, feeder obliteration was long term. One animal had vasospasm during embolization, and complete obliteration of the main feeder was maintained for 3 mo, but partial recanalization developed 2 mo later. One animal receiving pure 2-P-HEMA had an infarction. In the animal embolized with 50% 2-P-HEMA, angiography and CT revealed embolic material in the circle of Willis; the animal died after embolization. No marked inflammatory reaction in the vessel wall or perivascular tissue was observed in the embolized AVMs. CONCLUSION: Experimental AVM embolization with pure 2-P-HEMA, made radiopaque with tungsten, is technically feasible in swine. Because of its properties, 2-P-HEMA has great potential as a therapeutic embolic agent.

Total intravenous anesthesia for intraoperative monitoring of the motor pathways: an integral view combining clinical and experimental data.

OBJECT: Monitoring of descending corticospinal pathways by using motor evoked potentials (MEPs) has proven to be useful in preventing permanent neurological deficits during cranial and spinal procedures. Difficulties in interpretation of intraoperative changes in potentials may largely be attributed to the effects of anesthesia. Development of suitable intravenous anesthesia protocols specifically tailored for MEP monitoring, including plasma level target-controlled infusion (TCI), requires precise knowledge of the specific neurophysiological properties of the various agents. METHODS: The effects of alfentanil, sufentanil, fentanyl, remifentanil, thiopental, midazolam, etomidate, ketamine, and propofol on neurogenic and myogenic MEPs were evaluated in an integral study combining clinical data obtained in 40 patients and experimental investigations conducted in 140 animals. The dose-dependent modulation of MEPs after electrical and magnetoelectrical stimulation of the motor cortex was recorded from peripheral muscles and the spinal cord. The results were as follows: opioids, propofol, and thiopental suppressed myogenic, but not neurogenic MEPs in a dose-dependent fashion; remifentanil exerted the least suppressive effects. Etomidate and midazolam did not suppress myogenic MEP, even at plasma concentrations sufficient for anesthesia. Ketamine induced moderate reduction of compound muscle action potential amplitudes only at high doses. Remifentanil and propofol administered via TCI systems allowed recording of myogenic potentials within a defined target plasma concentration range. CONCLUSIONS: Development of standardized total intravenous anesthesia/TCI protocols by using anesthetic agents such as propofol, remifentanil, ketamine, and midazolam, which have favorable pharmacokinetic and neurophysiological properties, will enhance the quality of intraoperative MEPs and promote the use of MEP monitoring as a useful tool to reduce surgery-related morbidity.

Tissue oxygenation and capacity to deliver O2 do the two go together?

Oxidative phosphorylation is the most important source of energy in mammals. Oxygen capture, convective and diffusive oxygen transport as well as the final intracellular oxygen utilization within the mitochondria represent highly refined mechanisms, supervised by a variety of physiological control systems. Any disease process interfering with the delivery of oxygen to tissue will ultimately lead to an impairment of cellular energy production. Generally, cellular hypoxia may result from either reduced oxygen uptake (hypoxic hypoxia), reduced convective and diffusive oxygen transport (circulatory and anemic hypoxia), impaired oxygen consumption (histotoxic hypoxia), or a combination of these states. To effectively treat any of these conditions, it is mandatory to recognize the underlying specific alterations of oxidative metabolism. Identification of the various types of hypoxia as well as contemporary treatment surveillance strategies depend primarily on measuring oxygen partial pressure in inspiratory gas, blood (arterial, mixed-venous) and tissue (extracellular fluid), next to monitoring of various circulatory parameters. This review focuses (a) on the diagnostic value of different techniques used to monitor blood and tissue oxygenation and (b) on the effects of impaired capacity to deliver O2 on tissue oxygen delivery and consumption. The potential value of multiparametric monitoring in guiding specific treatment measures to improve oxygen delivery to tissue is highlighted.