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Featured researches published by Erhard W. Lang.


Critical Care Medicine | 2001

Cerebral autoregulation testing after aneurysmal subarachnoid hemorrhage: the phase relationship between arterial blood pressure and cerebral blood flow velocity.

Erhard W. Lang; Rolf R. Diehl; H. Maximilian Mehdorn

ObjectiveImpairment of cerebral autoregulation (CA) appears to be an important cause for secondary ischemia after subarachnoid hemorrhage (SAH). It has been shown that graded CA impairment is predictive of outcome. Little is known about whether such impairment is present, what causes CA impairment, whether it precedes vasospasm, and whether it is predictive of outcome in patients with severe aneurysmal SAH. DesignProspective, controlled study. SettingNeurosurgical intensive care unit. PatientsTwelve patients after aneurysmal subarachnoid hemorrhage, 40 controls. InterventionsRecording of cerebral blood flow velocities and continuous measurement of arterial blood pressure at a controlled ventilatory frequency of six per minute to standardize the influence of intrathoracic pressure changes on blood pressure. Measurements and Main Results We calculated the phase shift angles (&Dgr;&phgr;°) between slow (0.1 Hz) arterial blood pressure and cerebral blood flow velocity waves measured by transcranial Doppler ultrasound in the middle cerebral artery during a) posthemorrhage days (PHD) 1–6 (early or prevasospasm phase), and b) during PHD 7–13 (late or vasospasm phase) using a 6/min ventilation protocol, and in 40 controls spontaneously ventilating at the same rate. &Dgr;&phgr; <30° indicated lost CA. Mean flow velocities >100 cm/sec were considered vasospasm. We combined early and late measurements to assess the CA relationship with low cerebral perfusion pressure (CPP) and/or vasospasm. We assessed the Glasgow Outcome Scale (GOS) score at discharge (1 = worst, 5 = best).The admission Hunt and Hess score was 3.6 ± 0.7. GOS scores were n = 3 (GOS 1), n = 2 (GOS 2), n = 5 (GOS 3), n = 1 (GOS 4), and n = 1 (GOS 5). In the early phase, &Dgr;&phgr; was 40.4 ± 19.8° (left), and 40.4 ± 19.2° (right). CPP was 69.4 ± 10.9, intracranial pressure (ICP) was 6.7 ± 2.8 mm Hg. In the late phase, &Dgr;&phgr; worsened in six patients and none improved: 32.1 ± 21° (left), and 26.9 ± 17.2° (right); CPP was 68.1 ± 12.1, ICP was 7.5 ± 3.7 mm Hg. CA was significantly impaired in both phases when compared with normal subjects (&Dgr;&phgr;: 65.7 ± 24.5°;p < .01 for early, p < .001 for late phase). In the early phase, seven of eight patients in whom autoregulation was intact had a GOS >2 at discharge and disturbed CA on at least one side was predictive of either vegetative condition at discharge or death (p < .01). In the late phase, &Dgr;&phgr; was no longer predictive of outcome. Spasm was present in 8 of 17 vessels (47%) in which CA was lost; no spasm was found in 25 of 28 vessels (89%) in which CA was intact (p < .01). A low CPP was present in 6 of 17 vessels (35%) in which CA was lost; a normal CPP was found in 21 of 27 vessels (78%) in which CA was intact (p > .05, NS). However, 14 of 17 vessels (82%) with lost CA showed spasm and/or low CPP while only 8 of 27 cases (30%) with intact CA had either spasm or low CPP (p < .001). ConclusionsCA can be assessed in a graded fashion in SAH patients. CA impairment precedes vasospasm; ongoing vasospasm worsens CA. CA assessment early after subarachnoid hemorrhage, within PHD 1–6, is predictive of outcome whereas late assessment is not. CA impairment is associated with cerebral vasospasm and low CPP.


Journal of Neurology, Neurosurgery, and Psychiatry | 2003

Cerebral vasomotor reactivity testing in head injury: the link between pressure and flow

Erhard W. Lang; Jim Lagopoulos; Jane Griffith; Kwok Yip; A Yam; Yugan Mudaliar; H M Mehdorn; Nicholas W. C. Dorsch

Background: It has been suggested that a moving correlation index between mean arterial blood pressure and intracranial pressure, called PRx, can be used to monitor and quantify cerebral vasomotor reactivity in patients with head injury. Objectives: To validate this index and study its relation with cerebral blood flow velocity and cerebral autoregulation; and to identify variables associated with impairment or preservation of cerebral vasomotor reactivity. Methods: The PRx was validated in a prospective study of 40 head injured patients. A PRx value of less than 0.3 indicates intact cerebral vasomotor reactivity, and a value of more than 0.3, impaired reactivity. Arterial blood pressure, intracranial pressure, mean cerebral perfusion pressure, and cerebral blood flow velocity, measured bilaterally with transcranial Doppler ultrasound, were recorded. Dynamic cerebrovascular autoregulation was measured using a moving correlation coefficient between arterial blood pressure and cerebral blood flow velocity, the Mx, for each cerebral hemisphere. All variables were compared in patients with intact and impaired cerebral vasomotor reactivity. Results: No correlation between arterial blood pressure or cerebral perfusion pressure and cerebral blood flow velocity was seen in 19 patients with intact cerebral vasomotor reactivity. In contrast, the correlation between these variables was significant in 21 patients with impaired cerebral vasomotor reactivity, whose cerebral autoregulation was reduced. There was no correlation with intracranial pressure, arterial blood pressure, cerebral perfusion pressure, or interhemispheric cerebral autoregulation differences, but the values for these indices were largely within normal limits. Conclusions: The PRx is valid for monitoring and quantifying cerebral vasomotor reactivity in patients with head injury. This intracranial pressure based index reflects changes in cerebral blood flow and cerebral autoregulatory capacity, suggesting a close link between blood flow and intracranial pressure in head injured patients. This explains why increases in arterial blood pressure and cerebral perfusion pressure may be useful for reducing intracranial pressure in selected head injured patients (those with intact cerebral vasomotor reactivity).


Journal of Clinical Neuroscience | 2005

Cerebral autoregulation and ageing.

Alan T. Yam; Erhard W. Lang; Jim Lagopoulos; Kwok Yip; Jane Griffith; Yugan Mudaliar; Nicholas W. C. Dorsch

Little is known about the effects of ageing on cerebral autoregulation (CA). To examine the relationship between age and CA in adults, we conducted a prospective study using a non-invasive protocol without external stimuli. We studied 32 subjects, aged 23-68 years. They were assigned to a young group (28+/-5 years) and an old group (54+/-8 years). The groups were sex-matched. Transcranial Doppler ultrasonography (TCD) was used to record bilateral middle cerebral artery flow velocities (CBFV, cm/sec). Noninvasive beat-to-beat tonometric arterial blood pressure (ABP) measurement of the radial artery was used to record spontaneous blood pressure fluctuations. The Mx, an index of dynamic cerebral autoregulation (dCA), was calculated from a moving correlation between ABP and CBFV. We did not find a correlation between age and Mx. No statistically significant difference in the Mx between the groups (0.27+/-0.23, young, vs. 0.37+/-0.24, old) was demonstrated. Age does not affect dynamic cerebral autoregulation assessed by the Mx index in healthy adult subjects. This study supports findings from previous papers wherein CA was measured with protocols which require external stimuli. Further studies are needed to determine CA in subjects above 70 years of age.


Neurosurgical Review | 2007

Direct cerebral oxygenation monitoring—a systematic review of recent publications

Erhard W. Lang; Jamin M. Mulvey; Yugan Mudaliar; Nicholas W. C. Dorsch

This review has been compiled to assess publications related to the clinical application of direct cerebral tissue oxygenation (PtiO2) monitoring published in international, peer-reviewed scientific journals. Its goal was to extract relevant, i.e. positive and negative information on indications, clinical application, safety issues and impact on clinical situations as well as treatment strategies in neurosurgery, neurosurgical anaesthesiology, neurosurgical intensive care, neurology and related specialties. For completeness’ sake it also presents some related basic science research. PtiO2 monitoring technology is a safe and valuable cerebral monitoring device in neurocritical care. Although a randomized outcome study is not available its clinical utility has repeatedly been clearly confirmed because it adds a monitoring parameter, independent from established cerebral monitoring devices. It offers new insights into cerebral physiology and pathophysiology. Pathologic values have been established in peer-reviewed research, which are not only relevant to outcome but are treatable. The benefits clearly outweigh the risks, which remains unchallenged in all publications retrieved. It is particularly attractive because it offers continuous, real-time data and is available at the bedside.


Neurological Research | 2003

Cerebral edema leading to decompressive craniectomy: An assessment of the preceding clinical and neuromonitoring trends

Rainer Joachim Strege; Erhard W. Lang; Andreas M. Stark; Heike Scheffner; Michael J. Fritsch; Harald Barth; H. Maximilian Mehdorn

Abstract The aim of this study was to examine the pre-operative clinical and neuromonitoring courses in patients with a decompressive craniectomy to assess and to compare clinical and neuromonitoring signs indicating extensive cerebral edema. We conducted a retrospective analysis of the clinical signs and courses of simultaneous monitoring of intracranial pressure (ICP) and cerebral oxygenation (PtiO2) in 26 consecutive patients who were sedated and treated with a decompressive craniectomy due to extensive cerebral edema after aneurysmal subarachnoid hemorrhage (SAH) (n = 20) or severe head injury (SHI) (n = 6). Pathological monitoring trends always preceded clinical deterioration. In 18 of 26 patients extensive cerebral edema was indicated solely by increasing ICP >20 mmHg or decreasing PtiO2 < 10 mmHg or both. Anisocoria occured in only 8 of 26 patients. As opposed to SHI patients, 9 of 20 SAH patients showed decreasing PtiO2 as first warning sign clearly before neurological deterioration or ICP increase. This series shows the utility of combined ICP and PtiO2 monitoring in patients who develop extensive cerebral edema. Pathological monitoring trends indicate deterioration prior to clinical signs which offers a wider therapeutical window. PtiO2 monitoring appears to be particularly valuable after aneurysmal SAH as adjunct to ICP monitoring and CT imaging.


Journal of Neurosurgery | 2015

Short pressure reactivity index versus long pressure reactivity index in the management of traumatic brain injury.

Erhard W. Lang; Magdalena Kasprowicz; Peter Smielewski; Edgar Santos; John D. Pickard; 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 (χ(2) = 30.6, p < 0.00001), and severe disability was associated with CPP above CPPopt for PRx (χ(2) = 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.


Acta Neuropsychiatrica | 2006

Cerebrovascular autoregulation as a neuroimaging tool

Jim Lagopoulos; Gin S. Malhi; Belinda Ivanovski; Catherine Cahill; Erhard W. Lang; Yugan Mudaliar; Nick Dorsch; Alan Yam; Jane Griffith; Jamin Mulvey

Functional transcranial Doppler (fTCD) sonography provides a high temporal resolution measure of blood flow and has over the years proved to be a valuable tool in the clinical evaluation of patients with cerebrovascular disorders. More recently, due to advances in physics and computing, it has become possible to derive indices of cerebrovascular autoregulation (CA) as well as cerebrovascular pressure reactivity (CR), using non-invasive techniques. These indices provide a dynamic representation of the brains regulatory blood flow mechanisms not only in pathological states but also in health. However, whilst the temporal resolution of these regulatory indices is very good, spatially, the localization of brain regions remains very poor, thus limiting its brain mapping capacity. Functional MRI, on the contrary, is a brain-imaging technique that operates on similar blood flow principles; however, unlike fTCD, it provides high spatial resolution. Because both fTCD and fMRI determine blood flow-dependant imaging parameters, the coupling of fTCD with fMRI may provide greater insight into brain function by virtue of the combined enhanced temporal and spatial resolution that each technique affords. This review summarizes the fTCD technique with particular emphasis on the CA and CR indices and their relationship in traumatic brain injury as well as in health.


Acta neurochirurgica | 2016

Outcome, Pressure Reactivity and Optimal Cerebral Perfusion Pressure Calculation in Traumatic Brain Injury: A Comparison of Two Variants

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

This study investigates the outcome prediction and calculation of optimal cerebral perfusion pressure (CPPopt) in 307 patients after severe traumatic brain injury (TBI) based on cerebrovascular reactivity calculation of a moving correlation correlation coefficient, named PRx, between mean arterial pressure (ABP) and intracranial pressure (ICP). The correlation coefficient was calculated from simultaneously recorded data using different frequencies. PRx was calculated from oscillations between 0.008 and 0.05Hz and the longPRx (L-PRx) was calculated from oscillations between 0.0008 and 0.016 Hz. PRx was a significant mortality predictor, whereas L-PRx was not. CPPopt for pooled data was higher for L-PRx than for PRx, with no statistical difference. Mortality was associated with mean CPP below CPPopt. Severe disability was associated with CPP above CPPopt (PRx). These relationships were not statistically significant for CPPopt (L-PRx). We conclude that PRx and L-PRx cannot be used interchangeably.


Acta neurochirurgica | 2016

Plateau Waves of Intracranial Pressure and Partial Pressure of Cerebral Oxygen

Erhard W. Lang; Magdalena Kasprowicz; Peter Smielewski; John D. Pickard; Marek Czosnyka

This study investigates 55 intracranial pressure (ICP) plateau waves recorded in 20 patients after severe traumatic brain injury (TBI) with a focus on a moving correlation coefficient between mean arterial pressure (ABP) and ICP, called PRx, which serves as a marker of cerebrovascular reactivity, and a moving correlation coefficient between ABP and cerebral partial pressure of oxygen (pbtO2), called ORx, which serves as a marker for cerebral oxygen reactivity. ICP and ICPamplitude increased significantly during the plateau waves, whereas CPP and pbtO2 decreased significantly. ABP, ABP amplitude, and heart rate remained unchanged. In 73 % of plateau waves PRx increased during the wave. ORx showed an increase during and a decrease after the plateau waves, which was not statistically significant. Our data show profound cerebral vasoparalysis on top of the wave and, to a lesser extent, impairment of cerebral oxygen reactivity. The different behavior of the indices may be due to the different latencies of the cerebral blood flow and oxygen level control mechanisms. While cerebrovascular reactivity is a rapidly reacting mechanism, cerebral oxygen reactivity is slower.


Critical Care Medicine | 2003

Tissue oxygen reactivity and cerebral autoregulation after severe traumatic brain injury.

Erhard W. Lang; Marek Czosnyka; H. Maximilian Mehdorn

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Jim Lagopoulos

University of the Sunshine Coast

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Magdalena Kasprowicz

Wrocław University of Technology

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Kwok Yip

University of Sydney

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