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Erhard W. Lang, Magdalena Kasprowicz, Peter Smielewski, Edgar Santos, John Pickard and Marek Czosnyka

OBJECT

The pressure reactivity index (PRx) correlates with outcome after traumatic brain injury (TBI) and is used to calculate optimal cerebral perfusion pressure (CPPopt). The PRx is a correlation coefficient between slow, spontaneous changes (0.003–0.05 Hz) in intracranial pressure (ICP) and arterial blood pressure (ABP). A novel index—the so-called long PRx (L-PRx)—that considers ABP and ICP changes (0.0008–0.008 Hz) was proposed.

METHODS

The authors compared PRx and L-PRx for 6-month outcome prediction and CPPopt calculation in 307 patients with TBI. The PRx- and L-PRx–based CPPopt were determined and the predictive power and discriminant abilities were compared.

RESULTS

The PRx and L-PRx correlation was good (R = 0.7, p < 0.00001; Spearman test). The PRx, age, CPP, and Glasgow Coma Scale score but not L-PRx were significant fatal outcome predictors (death and persistent vegetative state). There was a significant difference between the areas under the receiver operating characteristic curves calculated for PRx and L-PRx (0.61 ± 0.04 vs 0.51 ± 0.04; z-statistic = −3.26, p = 0.011), which indicates a better ability by PRx than L-PRx to predict fatal outcome. The CPPopt was higher for L-PRx than for PRx, without a statistical difference (median CPPopt for L-PRx: 76.9 mm Hg, interquartile range [IQR] ± 10.1 mm Hg; median CPPopt for PRx: 74.7 mm Hg, IQR ± 8.2 mm Hg). Death was associated with CPP below CPPopt for PRx (χ2 = 30.6, p < 0.00001), and severe disability was associated with CPP above CPPopt for PRx (χ2 = 7.8, p = 0.005). These relationships were not statistically significant for CPPopt for L-PRx.

CONCLUSIONS

The PRx is superior to the L-PRx for TBI outcome prediction. Individual CPPopt for L-PRx and PRx are not statistically different. Deviations between CPP and CPPopt for PRx are relevant for outcome prediction; those between CPP and CPPopt for L-PRx are not. The PRx uses the entire B-wave spectrum for index calculation, whereas the L-PRX covers only one-third of it. This may explain the performance discrepancy.

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Noninvasive intracranial compliance monitoring

Technical note and clinical results

Erhard W. Lang, Klaus Paulat, Christoph Witte, Jürgen Zolondz and H. Maximilian Mehdorn

✓ Although invasive measurement of intracranial pressure (ICP) involving high-resolution waveform analysis allows assessment of intracranial compliance (ICC), it is only feasible in a few selected neurosurgical conditions. Intracranial compliance can be assessed using the high-frequency centroid (HFC), which is the power-weighted mean frequency within the 4 to 15—Hz band of the ICP waveform. The authors have systematically tested the utility, performance, and reliability of a noninvasive monitor of ICC. The underlying principle of this device is that the ICP transmission and its infrasonic waves are transmitted through the inner ear toward the tympanic membrane. If the outer ear is sealed in an airtight fashion, motions of the tympanic membrane cause air pressure fluctuations that can be recorded using a special sensor.

The authors compared the HFC calculated from an intraparenchymal ICP sensor with that obtained simultaneously from an ipsilaterally placed noninvasive device during half of a respiratory cycle (peak to baseline) as well as for three random samples of three heart cycles. They analyzed 32 sessions in 13 patients in whom mechanical ventilation had been established. In four (11%) of 36 sessions they could not demonstrate an adequate signal.

For the peak-to-baseline cycle, the mean invasively recorded HFC was 8.05 ± 0.55 Hz (range 6.7–9 Hz) whereas the mean noninvasively recorded HFC was 8.04 ± 0.49 Hz (range 7–9.3 Hz). The ICP was 8.5 ± 5 mm Hg (range 2–24 mm Hg). For the three heart cycles randomly sampled, the values were 7.73 ± 0.51 Hz (range 6.7–8.6 Hz) and 7.76 ± 0.56 mm Hg (range 6.5–8.8 mm Hg), respectively.

This device allows noninvasive assessment of ICC based on the HFC waveform analysis that is equivalent to that obtained by invasive intraparenchymal recording. The monitoring device may become a valuable tool for monitoring parameters in patients in whom placement of an intracranial sensor is not feasible but assessment of ICC as an alternative to ICP measurement is desired.

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Ali Ghahreman, Vishal Bhasin, Raymond Chaseling, Bronwyn Andrews and Erhard W. Lang

Object

The purpose of this study was to evaluate the demographics, clinical and radiological features, and clinical outcomes of nonaccidental pediatric head injury.

Methods

The authors reviewed 65 consecutive cases of nonaccidental head injury in a single pediatric neurosurgical unit during a period of 7 years. The mean patient age was 8.2 months (range 0.5–46 months). There were 39 boys and 26 girls. A history of abuse was present in 24% of families. There was a high incidence of family disruption, substance abuse, and premature birth. Fathers were the most common perpetrators. Fifteen patients had a Glasgow Coma Scale score of less than 10. Thirty-five patients had seizures on or preceding admission. Subdural hematoma was the most common finding (81.5%). Skull fractures were present in 36.9% of patients, skeletal injuries in 50% (of which 67% were subclinical), and retinal hemorrhages in 59%. The radiological finding of ischemia or edema had a significant correlation with a poor outcome. Magnetic resonance imaging revealed additional pathological findings not visible on computerized tomography scanning in 18 (49%) of 37 cases. Surgery was performed in 17 patients; recurrence of the subdural collection occurred in 46% of them. In this group, reevacuations were followed by further recurrences, and a subdural—peritoneal shunt was eventually required. Four patients died. Of the 56 surviving patients reviewed on a long-term basis, 19 made a full recovery, and epilepsy was reported in 17%.

Conclusions

Magnetic resonance imaging should be routinely used in depicting ischemia, which is associated with a poor outcome. The high incidence of subclinical skeletal injuries stresses the importance of assessment of suspected cases of nonaccidental trauma with skeletal surveys and bone scans. Recurrence of subdural collection following burr hole drainage is common and is best treated with a subdural—peritoneal shunt.