Traumatic brain injury (TBI) is often complicated by acute subdural hemorrhage (ASDH) with a high mortality rate. The pathophysiological mechanisms behind such an injury type and the contribution of blood to the extent of an injury remain poorly understood. Therefore, the goals of this study were to establish a porcine ASDH model in order to investigate pathomechanisms of ASDH and to compare effects induced by blood or sheer volume. Thus, we infused 2, 5, and 9 mL of blood (up to 15% of intracranial volume), and we compared a 5-mL blood and paraffin oil volume to separate out effects of extravasated blood on brain tissue. An extended neuromonitoring was applied that lasted up to 12 h after injury and included intracranial pressure (ICP), cerebral perfusion pressure (CPP), tissue oxygen concentration (ptiO(2)), biochemical markers (glutamate, lactate), somatosensory evoked potentials (SEP), brain water content, and histological assessment (Lesion Index [LI]). Volume-dependent changes were detected mainly during the first hours after injury. ICP increased to significant levels (p < 0.05) of 36.89 +/- 1.59, 15.52 +/- 0.48, and 11.25 +/- 0.35 mm Hg after 9, 5, and 2 mL of subdural blood, respectively (sham, 4.85 +/- 0.06 mm Hg). The ptiO(2) dropped drastically after 9 mL of subdural blood without recovery in both hemispheres to below 20% of baseline, but was affected little after 2 and 5 mL in the acute monitoring period (maximal drop to 71% of baseline). Later, 5 mL of blood led to a significant increase of ptiO(2) compared to 2 mL ipsilaterally (p < 0.05). Glutamate and lactate showed a comparable pattern with a long-lasting increase after 9 mL of blood and short-lasting changes after 2 and 5 mL. The two smaller volumes caused an increased brain swelling (2 mL, 80.60 +/- 0.34%; 5 mL, 81.20 +/- 0.66%; p < 0.05 vs. sham), a significant LI (sham, 6.4 +/- 1.4; 2 mL, 30.0 +/- 0.95; 5 mL, 32.1 +/- 1.2; p < 0.05 vs. sham), and a reduced SEP amplitude (5 mL, p < 0.05 vs. baseline) at the end of the experiment. A 9-mL led to herniation during the experiment causing dramatical brain swelling and acute histological damage. Comparison of blood volume with paraffin oil showed no significance, indicating that volume alone determines the acute pathophysiological processes leading to a rapidly developing histological damage. Additional effects due to blood contact with brain tissue (e.g., inflammation) may be detected only at later time points (>12 h).
SummaryBackground. Oxygen tension sensors have been used to monitor tissue oxygenation in human brain for several years. The working principals of the most frequently used sensors, the Licox (LX) and Neurotrend (NT), are different, and they have never been validated independently for correct measurement in vitro. Therefore, we tried to clarify if the two currently available sensors provide sufficient accuracy and stability.Method. 12 LX oxygen tension sensors and NT sensors were placed into a liquid-filled tonometer chamber. The solution was kept at 37 AE 0.2 C and equilibrated with five calibration gases containing different O 2 -and CO 2 -concentrations. After equilibration, readings were taken for each gas concentration (accuracy test). Afterwards, the sensors were left in 3% O 2 and 9% CO 2 and readings were taken after 24, 48, 72, 96 and 120 hours (drift test). Thereafter, a 90% response time test was performed transferring sensors from 1% to 5% oxygen concentration and back, using pre-equilibrated tonometers.Findings. All Licox oxygen probes [12] were used for this study. Two of 14 Neurotrend sensors did not calibrate, revealing a failure rate of 14% for NT. Oxygen tension during the accuracy test was measured as follows: 1% O 2 (7.1 mmHg): LX 6.5 AE 0.4, NT 5.3 AE 2.3 mmHg, 2% O 2 (14.2 mmHg): LX 12.9 AE 0.6, NT 12.1 AE 2.2 mmHg, 3% O 2 (21.4 mmHg): LX 19.8 AE 0.7, NT 19.4 AE 2.4 mmHg, 5% O 2 (35.8 mmHg): LX 33.4 AE 1.0 mmHg, NT 33.5 AE 2.9 mmHg, 8% O 2 (57.0 mmHg): 53.8 AE 1.5, NT 53.6 AE 3.3 mmHg. After 120 hours in 3% O 2 (21 mmHg), LX measured 19.8 AE 1.9 mmHg, NT 17.9 AE 4.7 mmHg. 90% response time from 1% to 5%=5% to 1% oxygen concentration was 129 AE 27=174 AE 26 sec for LX, 55 AE 19=98 AE 39 sec for NT.Conclusions. Both systems are measuring oxygen tension sufficiently, but more accurately with LX probes. NT sensors read significantly lower pO 2 in 1% O 2 and show an increasing deviation with higher oxygen concentrations which was due to two of twelve probes. A slight drift towards lower oxygen tension readings for both sensors but more pronounced for the NT does not impair long-term use. NT measures pCO 2 and pH very accurately.
The translaminar approach is an effective and minimally invasive technique in both canalicular and cranio-dorsolateral disc herniations. It gives an additional possibility to avoid partial removal of the facet joints, can be performed in all lumbar segments and preserves structures important for segmental spinal stability. The approach allows access to the extruded disc fragment and intervertebral disc space comparable to classical approaches and is a frequently used operative technique in our department.
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