Unexpected death after occipital condylar fracture

We present a rare fatal complication of an occipital condylar fracture. The patient was initially neurologically intact, but showed secondary clinical deterioration. Imaging revealed extensive extra-axial hemorrhage at the craniocervical junction and an acute obstructive hydrocephalus. MR imaging demonstrated a T2 hyperintens signal in both the lower brainstem and upper cervical spinal cord, likely caused by the extra-axial hemorrhage. As prognosis was estimated infaust, supportive treatment was discontinued and the patient died soon thereafter. This case report illustrates a rare, delayed complication and unexpected death in a patient having sustained an occipital condylar fracture.

Protocol for intraoperative assessment of the human cerebrovascular glycocalyx

INTRODUCTION

Adequate functioning of the blood-brain barrier (BBB) is important for brain homoeostasis and normal neuronal function. Disruption of the BBB has been described in several neurological diseases. Recent reports suggest that an increased permeability of the BBB also contributes to increased seizure susceptibility in patients with epilepsy. The endothelial glycocalyx is coating the luminal side of the endothelium and can be considered as the first barrier of the BBB. We hypothesise that an altered glycocalyx thickness plays a role in the aetiology of temporal lobe epilepsy (TLE), the most common type of epilepsy. Here, we propose a protocol that allows intraoperative assessment of the cerebrovascular glycocalyx thickness in patients with TLE and assess whether its thickness is decreased in patients with TLE when compared with controls.

METHODS AND ANALYSIS

This protocol is designed as a prospective observational case-control study in patients who undergo resective brain surgery as treatment for TLE. Control subjects are patients without a history of epileptic seizures, who undergo a craniotomy or burr hole surgery for other indications. Intraoperative glycocalyx thickness measurements of sublingual, cortical and hippocampal microcirculation are performed by video microscopy using sidestream dark-field imaging. Demographic details, seizure characteristics, epilepsy risk factors, intraoperative haemodynamic parameters and histopathological evaluation are additionally recorded.

ETHICS AND DISSEMINATION

This protocol has been ethically approved by the local medical ethical committee (ID: NL51594.068.14) and complies with the Declaration of Helsinki and principles of Good Clinical Practice. Informed consent is obtained before study enrolment and only coded data will be stored in a secured database, enabling an audit trail. Results will be submitted to international peer-reviewed journals and presented at international conferences.

TRIAL REGISTRATION NUMBER

NTR5568.

Influence of cerebral oxygenation following severe head injury on neuropsychological testing

Despite recent advances in the management of severe head injury the mortality and morbidity remains high. Intracranial pressure (ICP) and cerebral perfusion pressure (CPP) are crucial parameters for the correct management at the intensive care unit, due to their therapeutic and prognostic importance. In addition, regional brain tissue oxygenation (ptiO2) seems to be of importance. While different studies demonstrated the impact of cerebral hypoxia on outcome (mortality), no data are available focusing on morbidity (neuropsychological deficits). Therefore, our study is carried out to demonstrate a possible relationship between amount of cerebral oxygenation during acute stage after severe head injury and neuropsychological outcome. Besides ICP and CPP, ptiO2 was monitored in 40 severely head injured patients during the ICU stay from the day of admission until day 10. Monitoring data were stored and amount of hypoxic episodes were calculated. Besides outcome using the Glasgow Outcome Scale neuropsychological testing was performed 2-3 years after injury. Analysing the quality of brain tissue oxygenation, a relationship to the performance in neuropsychological tests could be found. Patients with low brain tissue oxygenation had a worse outcome in neuropsychological testing, especially concerning intelligence and memory. Associated with these deficits patients showed a reduced performance in their profession. Our data suggest a possible predictive value of brain tissue oxygen on morbidity analysing neurocognitive function after head injury. This may implicate monitoring and treatment of cerebral hypoxia.

Brain tissue oxygen guided treatment supplementing ICP/CPP therapy after traumatic brain injury

OBJECTIVE

To evaluate the effects of a brain tissue oxygen (P(ti)O(2)) guided treatment in patients with traumatic brain injury.

METHODS

P(ti)O(2) was monitored in 93 patients with severe traumatic brain injury. Forty patients admitted from 1993 to 1996 were treated with intracranial pressure/cerebral perfusion pressure (ICP/CPP) management alone (ICP < 20 mm Hg, CPP > 70 mm Hg). Fifty three patients admitted from 1997 to 2000 were treated using ICP/CPP management, but in this second group CPP was also increased as individually required to raise the P(ti)O(2) above 1.33 kPa (10 mm Hg) (P(ti)O(2) guided group).

RESULTS

Cerebral hypoxic phases with P(ti)O(2) values below 1.33 kPa occurred significantly less often in the P(ti)O(2) guided group. P(ti)O(2) values were higher over the whole monitoring period. No statistical differences could be observed in outcome at six months, despite a positive trend in the P(ti)O(2) guided group.

CONCLUSIONS

Cerebral hypoxic events can be reduced significantly by increasing cerebral perfusion pressure as required. To show a clear beneficial effect of P(ti)O(2) guided cerebral perfusion pressure management on outcome, a multicentre randomised trial needs to be undertaken.

Advanced neuromonitoring including cerebral tissue oxygenation and outcome after traumatic brain injury

For 51 patients suffering from traumatic brain injury (GCS < 9), we compared the prognostic value of critical parameters derived from neuromonitoring of intracranial pressure (ICP), cerebral perfusion pressure (CPP) and brain tissue oxygenation (PiO2) during different time periods after trauma (< or = 12, < or = 24, < or = 48, < or = 72 and < or = 96 h). For patients with good outcome (GOS = 4-5, n = 30) the proportion of critical ICP values (> 40 mmHg) was about 0.2% during all time periods. The corresponding proportions for patients with bad outcome (GOS = 1-3, n = 21) rose from 0.2% to 4.7% during increasing time periods. The frequency of critical ICP values was significantly related to outcome (p < 0.001) for time periods > 48 h after trauma. Differences of critical CPP (< or = 50 mmHg) and hypoxic PiO2 (< or = 5 mmHg) between both outcome groups were less pronounced and for both parameters significant relations to outcome were only obtained for the longest time period (< or = 96 h, p < or = 0.05). Higher thresholds for CPP (< or = 60 mmHg, < or = 70 mmHg) did not reveal any relation to outcome. For all neuromonitoring parameters significant relations between the frequency of critical values and outcome could be determined. Critical ICP values provide the earliest and highest prognostic power, while critical CPP and hypoxic PiO2 only showed prognostic power in later time periods.

Near-infrared spectroscopy--not useful to monitor cerebral oxygenation after severe brain injury

Since its development more than twenty years ago, non-invasive near-infrared-spectroscopy (NIRS) has been widely used to monitor cerebral oxygenation. Despite of its growing number of users, the diagnostic value of near-infrared spectroscopy still remains unclear, especially in case of acute brain injury and long-term neuromonitoring, necessary during intensive care therapy. To evaluate quality and sensitivity of NIRS measurements compared to invasive ICP-, CPP- and regional brain tissue--pO2 (p(ti)O2) monitoring, 31 patients, suffering from severe brain injury due to subarachnoid hemorrhage or severe head injury, were studied. NIRS measurements were only possible in 80% (using the INVOS oximeter) and in 46% (using the CRITIKON monitor), while good data quality was obtained in 100% from ICP, CPP and p(ti)O2. Major reasons for the failure of NIRS measurements were: (1) a wet chamber between sensor and skin, (2) galea hematoma or (3) subdural air after craniotomy. Different tests were performed to compare the sensitivity of regular oxygen saturation (NIRS) with the sensitivity of invasively determined p(ti)O2. Only induced hyperoxia (FiO2 = 1.0) revealed a significant correlation between both parameters (r = 0.67, p < 0.01). Lower or no correlation was found after changing paCO2 and administration of mannitol. The high failure rate and the limited sensitivity does not make the clinical use of near-infrared spectroscopy suitable as a part of neuromonitoring after acute brain injury at the present time.

Prognostic significance of advanced neuromonitoring after traumatic brain injury using neural networks

While the therapeutic impact of tissue oxygenation (PtiO2) supplementing ICP-monitoring is proven by several clinical studies, its prognostic value is not well studied. In the following study artificial neural networks (ANN) were used to analyze the accuracy of outcome prediction after traumatic brain injury (TBI) for different combinations of clinical data and parameters derived from neuromonitoring. The total group included 95 patients suffering from TBI. For all patients clinical data (age, GCS, pupillary response etc.) were recorded and outcome was classified using Glasgow outcome scale after 6 months. In a first step a subgroup of 60 patients was chosen to train a neural network to predict outcome based only on clinical data. In a second step the resting 35 patients all having continuous neuromonitoring with automatic data storage of ICP and PtiO2 were chosen. Different network models were composed using the former clinical model plus up to three additional input units for the following parameters: (a) relative number of ICP > 40 mmHg, (b) relative number of PtiO2 < 5 mmHg and (c) relative number of ICP > 30 mmHg with simultaneous PtiO2 < 10 mmHg. For each model the following time periods were analyzed: day 1-2, day 1-3 and day 1-4 after trauma and additionally day 1-4 after trauma plus last day of neuromonitoring. Pure clinical data allowed to predict outcome with 74.3% accuracy. A combination of clinical data with ICP (a) significantly increased the confidence levels of outcome prediction in all time periods (p < 0.05) with accuracy rates rising up to 82.9% for the longer time periods. The combination of clinical data and ICP & PtiO2 (c) lead to comparable results. In contrast, no significant increases were observed in the early time periods when combining clinical data with PtiO2 (b) while accuracy rates rose up to 80% for extended time periods after trauma. A combination of all parameters lead to results lying between the above results. The results indicate that prediction of outcome can be improved by combining clinical and neuromonitoring data. The prognostic value of ICP might be superior to that of PtiO2.

Clinical experience with 118 brain tissue oxygen partial pressure catheter probes

OBJECTIVE

We assessed the technical and diagnostic reliability of partial pressure of oxygen (PO2) of brain tissue (P(ti)O2) monitoring. The monitoring system and the catheter probes were tested in vitro, and clinical experiences obtained with 118 brain P(ti)O2 catheter probes, used in 101 patients, are reported.

METHODS

The polarographic (LICOX; Medical Systems Corp., Greenvale, NY) P(ti)O2 catheter probe lies 22 to 27 mm below the dura level; its PO2-sensitive surface is 7.1 mm2. For 10 patients, the adaptation time (with initially unreliable signals after insertion) was determined. For 27 patients, the probe was removed in a stepwise fashion (three increments of 5 mm) and the heterogeneity of brain P(ti)O2 levels was investigated. After removal of the catheter probes, their PO2 and zero display error values were determined and compared with probe performance data obtained in vitro with unused PO2 catheter probes.

RESULTS

Small iatrogenic hematomas were observed for two patients (1.7%). No infection occurred after 6.7 +/- 3.9 days (mean +/- standard deviation) of monitoring. The technical complication (dislocation or defect) rate was 13.6%. The mean adaptation time was 79.0 +/- 51.7 min. A flow chart is presented, which helps to rule out artifacts. The mean P(ti)O2 measured at 22 to 27 mm below the dura was 23.8 +/- 8.1 mm Hg, at 17 to 22 mm was 25.7 +/- 8.3 mm Hg, at 12 to 17 mm was 33.0 +/- 13.3 mm Hg (P < 0.01, compared with the initial value), and at 7 to 12 mm was 33.3 +/- 13.3 mm Hg (P < 0.01). Recent catheter probe versions exhibited a PO2 display error of -1.2 +/- 5.1% (mean +/- standard deviation, n = 38) and a mean zero display error of 1.1 +/- 0.9 mm Hg (n = 34). The greatest PO2 display errors were measured during the first 4 days of continuous monitoring. In the in vitro test (of 12 unused catheter probes), the maximal probe display error was 1.07 +/- 2.14%, tested at temperatures between 22 degrees C and 37 degrees C and tested at oxygen pressures of 0, 44, and 150 mm Hg. In vitro, the zero display error was -0.21 +/- 0.25 mm Hg.

CONCLUSION

Brain P(ti)O2 monitoring, reflecting an area 17 to 27 mm below the dura, is a safe and reliable technique for monitoring cerebral oxygenation. Excluding the first 1 hour after insertion, data are reliable, with almost 100% good data quality.

Multimodal hemodynamic neuromonitoring--quality and consequences for therapy of severely head injured patients

Fifty-five head injured patients (GCS < 8) were studied at an average of 7.5 +/- 3.4 days on the ICU to check quality of hemodynamic monitoring and the consequences for therapy. Multimodal neuromonitoring included intracranial pressure (ICP), mean arterial pressure (MAP), cerebral perfusion pressure (CPP), endtidal CO2 (EtCO2) as well as brain tissue--pO2 (p(ti)O2), regional oxygen (rSO2) and jugular venous oxygen saturation (SjO2). Regional p(ti)O2 as well as global SjO2 were sensitive technologies to detect hemodynamic changes. However analyzing reliability and good data quality regional p(ti)O2 (up to 95%) was superior to jugular bulb oximetry (up to 50%). Longterm-measurements of rSO2 using near infrared spectroscopy reached, if possible, a restricted reliability (good data quality up to 70%) and sensitivity in comparison to p(ti)O2. Especially p(ti)O2 enabled detection of critical p(ti)O2 (< 15 mm Hg) in up to 50% frequency during the first days after trauma and a second peak after day 6 to 8 according to evidence of CPP insults. Knowledge of baseline p(ti)O2 and CO2-reactivity allowed minimizing risk of ischemia by induced hyperventilation and improvement on cerebral microcirculation after mannitol administration could be individually recognized.

Brain tissue pO2 and outcome after severe head injury

Although the use of on-line monitoring of brain ti-pO2 is increasing, so far the critical level of 10 mmHg is derived from animal experiments and clinical analyses: no hard proof on outcome basis has been given until now. The authors present an outcome analysis of 35 patients with severe head injury. Inclusion criteria were: start of ti-pO2 monitoring < or = 40 h post-injury, the probe lying in CT scan normal tissue and the GOS at 6 months being available. The good outcome group (GOS 4 + 5, n = 17) showed a 17.7+/-9.1 h delay from the injury to the monitoring compared to the bad outcome group (GOS 1-3, n = 18) with (14.2+/-9.1 h) (p < 0.05). Age and initial Glasgow Coma Score were not different. In the bad outcome group there were more patients with a diffuse injury type 3 and 4. The distribution of the ti-pO2 values show in all the examined time intervals (day 0-6, 0-72 h, 0-48 h and 0-24 h) a left shift in the bad outcome group with most pronounced difference for ti-pO2 < or = 10 mmHg. For the period from 0-48 h and even more from 0-24 h post-injury, the difference between both groups was significant (p = 0.036 and p = 0.013). In the bad outcome group 35.5% of the values from 0-24 h were < 10mmHg (compared to 10.6% in the good outcome group. ti-pO2 values > or = 50 mmHg were seen more often in the bad outcome group; this occurred mainly after 48-72 h post-injury. The authors concluded that brain ti-pO2 monitoring is able to detect the occurrence of early hypoxic insults. Brain ti-pO2 monitoring is an important parameter in the multimodality monitoring system.

Brain tissue pO2-monitoring: catheterstability and complications

The authors report on the stability and complications of 73 LICOX brain ti-pO2-microcatheters in 70 patients. Mean monitoring time was 7.5 +/- 4.0 days. Patients prone to cerebral hypoxia (after severe head injury (GCS < 9) or a subarachnoid hemorrhage) had a ti-pO2-microcatheter inserted next to the ICP-probe in the typical frontal position. After the first 15 insertions, instead of the 3-way-screw (needing a 6 mm burrhole), a 1-way-screw (needing a 2.7 mm burrhole) was used for fixation in the bone; by doing so, the procedure can be performed in the ICU and takes only 15 min. Whenever possible a calibration at room air (to determine the sensitivity-drift) and in oxygen free solution (to determine the zero-drift) was performed after removal of the catheters. Ideally the expected pO2 at room air was around 154 mmHg (temperature dependent) and at zero calibration 0 mmHg. Mean sensitivity-drift for 54 catheters was -8.5 +/- 15.4%. Dividing the catheters into groups, depending on the duration of monitoring (1-4, 5-8 and 9-16 days), revealed that the greatest part of the (negative) sensitivity-drift occurred during day 1-4 after insertion. After 1 week of monitoring sometimes a positive drift occurred (being far less than the negative drift during the first 4 days). Compared to the old catheters (-10.3 +/- 17.3%) (on the first half of the patients) the new ones showed a lower sensitivity-drift (-6.8 +/- 13.4%). The zero-drift of 56 catheters was low with mean drift after 7.5 +/- 4.0 days of 1.5 +/- 1.5 mmHg. Here also the highest drift occurred on day 1-4 after insertion. No infection was seen and 2 times (2.7%) a small hematoma, not needing evacuation occurred. As the ti-pO2-catheter (having a smaller diameter) and the ICP-catheter were inserted at the same time, one cannot distinguish which catheter caused the hematoma. A possible explanation for the occurrence of the two hematomas is the insertion of the catheters too close to the midline. The authors conclude that LICOX ti-pO2-monitoring is a safe and reliable method. Further decrease of the complication rate and increase of the catheter-stability may be expected.

Influence of body position on tissue-pO2, cerebral perfusion pressure and intracranial pressure in patients with acute brain injury

It is a common practice to position head-injured patients in bed with the head elevated above the level of the heart in order to reduce intracranial pressure (ICP). This practice has been in vivid discussion since some authors argue a horizontal body position will increase the cerebral perfusion pressure (CPP) and therefore improve cerebral blood flow (CBF). However, ICP is generally significantly higher in the horizontal position. The aim of this study was to evaluate changes in regional microcirculation using tissue pO2 (ti-pO2), as well as changes in cerebral perfusion pressure (CPP) and intracranial pressure induced by changes in body position in patients with head injury. The effect of 0 degree and 30 degrees head elevation on ti-pO2. CPP, ICP and arterial blood pressure (MABP) was studied in 22 head injured patients during day 0-12 after trauma. The mean ICP was significantly lower at 30 degrees head elevation than at 0 degree (14.1 + 8.6 vs. 19.9 + 8.3 mmHg). While MABP was unaffected by head elevation, CPP was slightly higher at 30 degrees than at 0 degree (76.5 + 13.5 vs. 71.5 + 13.2 mmHg). However, regional ti-pO2 was unaffected by body position (30 degrees vs. 0 degree: 24.9 + 13.1 vs. 24.7 + 12.9 mmHg). In addition, there was no change in the time course after trauma concerning these findings in the individual patients. The data indicate that a moderate head elevation of 30 degrees reduces ICP without jeopardizing regional cerebral microcirculation as monitored using a polarographic ti-pO2 microcatheter.

Brain tissue pO2 in relation to cerebral perfusion pressure, TCD findings and TCD-CO2-reactivity after severe head injury

As a reliable continuous monitoring of cerebral blood flow and/or cerebral oxygen metabolism is necessary to prevent secondary ischaemic events after severe head injury (SHI) the authors introduced brain tissue pO2 (ptiO2) monitoring and compared this new parameter with TCD-findings, cerebral perfusion pressure (CPP) and CO2-reactivity over time on 17 patients with a SHI. PtiO2 reflects the balance between the oxygen offered by the cerebral blood flow and the oxygen consumption by the brain tissue. According to TCD-CO2-reactivity PtiO2-CO2-reactivity was introduced. After initially (day 0) low mean values (ptiO2 7.7 +/- 2.6 mmHg, TCD 60.5 +/- 32.0 cm/sec and CPP 64.5 +/- 16.0 mmHg/, ptiO2 increased together with an increase in blood flow velocity of the middle cerebral artery and CPP. The relative hyperaemic phase on days 3 and 4 was followed by a decrease of all three parameters. Although TCD-CO2-reactivity was except for day 0 (1.4 +/- 1.5%), sufficient, ptiO2-CO2-reactivity sometimes showed so-called paradox reactions from day 0 till day 3, meaning an increase of ptiO2 on hyperventilation. Thereafter ptiO2-CO2-reactivity increased, increasing the risk of inducing ischaemia by hyperventilation. The authors concluded that ptiO2-monitoring might become an important tool in our treatment regime for patients requiring haemodynamic monitoring.

Continuous monitoring of brain tissue PO2: a new tool to minimize the risk of ischemia caused by hyperventilation therapy

Secondary ischemic events worsen the outcome of patients with severe head injury. Such a secondary ischemic event may be caused by a forced hyperventilation. A consequence of the induced vasoconstriction is the risk of ischemia with an adverse effect on outcome. As a reliable and on-line technique, brain tissue pO2 (p(ti)O2) is used for monitoring regional microcirculation, to detect critical hypoperfusion. On 22 patients with a severe head injury 70 hyperventilation tests were performed from day 0-9 after trauma, calculating TCD-CO2-reactivity (% change of mean flow velocity per mm Hg paCO2 change). Additionally brain p(ti)O2-CO2-reactivity (% change of brain p(ti)O2 per mm Hg paCO2 change) was calculated and introduced. Group A +2 (p(ti)O2 < or = 15 mm Hg, TCD-CO2-reactivity > or = 2.5%, p(ti)O2-CO2-reactivity > 0%) and group B +2 (p(ti)O2 > 15 mm Hg, TCD-CO2-reactivity > or = 2.5%. p(ti)O2-CO2-reactivity > 0%) was formed. P(ti)O2 values in group A+2 decreased to an ischemic level or ischemia aggravated during hyperventilation. In group B+2 no ischemic events occurred. TCD-CO2-reactivity, p(ti)O2-CO2-reactivity and decrease of paCO2 were not significantly different in both groups. 6 out of 22 patients showed, from day 0-9, at least once a risk of (aggravating) ischemia by hyperventilation therapy.

Studies of tissue PO2 in normal and pathological human brain cortex

Brain cortex PO2 was measured after craniotomy and opening of the dura mater in 26 patients. We determined the brain tissue PO2 under standard narcotic conditions and after changing arterial PO2 and PCO2. Patients were divided into two groups (normal and pathological), depending on the aspect of their cortex on Ct/MRI and intraoperative appearance of the cortex. No statistical significantly difference was seen between tissue PO2 of the normal and the pathological group. A significant difference was seen only between the normal group and a subgroup with brain swelling (p = 0.0344). In the normal group no correlation was seen between tissue PO2 and arterial PO2 (r = 0.1541, p = 0.3076), whereas in the pathological group and especially in the oedema subgroup there was a highly significant correlation between tissue PO2 and PaO2 (r = 0.754, p = 0.0015 and r = 0.888, p = 0.0007). Breathing 100% oxygen changed tissue PO2 to 137.8 or 352 mmHg in the normal or the pathological group, respectively. Again, there was no correlation between tissue PO2 and PaO2 in the normal group (r = 0.1071, p = 0.392), whereas this correlation was significant in the pathological and the oedema subgroup (r = 0.6291, p = 0.0473 and r = 0.8385, p = 0.0185). This is evidence for regulatory mechanisms of tissue PO2. During hyperventilation no significant difference in tissue PO2 between the normal and the pathological group was seen. Low tissue PO2 values, however, indicate a risk for inducing ischemia.