Assessment of Cerebrovascular Autoregulation in Head-Injured Patients

Steiner, Luzius A.; Coles, Jonathan P.; Johnston, Andrew James; Chatfield, Doris A.; Smielewski, Peter; Fryer, Tim D.; Aigbirhio, Franklin I.; Clark, John C.; Pickard, John D.; Menon, David; Czosnyka, Marek

doi:10.1161/01.str.0000089014.59668.04

Cited by 161 publications

(79 citation statements)

References 32 publications

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“…A correlation around 0.6 may seem to be low, but in clinical brain monitoring it is not uncommon to interpret such a value as indicating a reasonable agreement (Reinhard et al, 2003;Steiner et al, 2003). In the clinical scenario, estimated values can be calculated repetitively and time-averaged, thus improving the signal-to-noise ratio.…”

Section: Discussionmentioning

confidence: 99%

Critical Closing Pressure: Comparison of Three Methods

López-Magaña

Richards

Radolovich

et al. 2009

J Cereb Blood Flow Metab

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Critical closing pressure (CCP) is an arterial pressure threshold below which small arterial vessels collapse. Our aim was to compare different methods to estimate CCP in the cerebrovascular circulation using the relationships between transcranial Doppler flow velocity (FV), laser-Doppler flux (LDF), and arterial blood pressure (ABP). A total of 116 experiments in rabbits were analyzed retrospectively. At the end of each recording, cardiac arrest (CA) was induced. Arterial blood pressure in femoral artery, basilar artery FV, cortical blood LDF, intracranial pressure (ICP) was recorded. Critical closing pressure was estimated using linear regression between decreasing mean ABP values, FV, and LDF during CA. In addition, CCP was calculated from FV waveform just before CA. The correlation between CCP evaluated using LDF and FV during CA was 0.98 (P < 0.0001). The correlation between CCP measured during CA and CCP estimated from the transcranial Doppler ultrasonography (TCD) waveform was weaker (R = 0.39; P < 0.001), with CCP calculated from waveform being significantly greater than CCP from CA (median difference 9 mm Hg; P < 0.003). Critical closing pressures obtained from FV waveform and CA correlated with mean ICP before CA (R = 0.40; P = 0.001). In conclusion strong correlation exists between CCP values obtained by means of FV and LDF during cardiac arrest. However, predictions of CCP using TCD waveform analysis show substantial differences from values of CCP recorded during cardiac arrest.

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Section: Discussionmentioning

confidence: 99%

Critical Closing Pressure: Comparison of Three Methods

López-Magaña

Richards

Radolovich

et al. 2009

J Cereb Blood Flow Metab

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“…The PRx was simultaneously compared with the global SRoR measured using PET CBF, which has shown a significant association (R 2 = 0.31, p = 0.02; 17 patients), especially for low static values. 32 After using PET to determine CMRO 2 , CMRO 2 has been shown to be negatively associated with PRx (R 2 = 0.21, p = 0.018; 22 patients). 31 The correlation between PRx and the O 2 extraction fraction was fitted into a quadratic model (R 2 = 0.55, p = 0.0001).…”

Section: Comparison Of Prx With Pet Cbf and Cmromentioning

confidence: 98%

Continuous monitoring of cerebrovascular pressure reactivity in patients with head injury

Zweifel

Lavinio

Steiner

et al. 2008

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Object Cerebrovascular pressure reactivity is the ability of cerebral vessels to respond to changes in transmural pressure. A cerebrovascular pressure reactivity index (PRx) can be determined as the moving correlation coefficient between mean intracranial pressure (ICP) and mean arterial blood pressure. Methods The authors analyzed a database consisting of 398 patients with head injuries who underwent continuous monitoring of cerebrovascular pressure reactivity. In 298 patients, the PRx was compared with a transcranial Doppler ultrasonography assessment of cerebrovascular autoregulation (the mean index [Mx]), in 17 patients with the PET–assessed static rate of autoregulation, and in 22 patients with the cerebral metabolic rate for O2. Patient outcome was assessed 6 months after injury. Results There was a positive and significant association between the PRx and Mx (R2 = 0.36, p < 0.001) and with the static rate of autoregulation (R2 = 0.31, p = 0.02). A PRx > 0.35 was associated with a high mortality rate (> 50%). The PRx showed significant deterioration in refractory intracranial hypertension, was correlated with outcome, and was able to differentiate patients with good outcome, moderate disability, severe disability, and death. The graph of PRx compared with cerebral perfusion pressure (CPP) indicated a U–shaped curve, suggesting that too low and too high CPP was associated with a disturbance in pressure reactivity. Such an optimal CPP was confirmed in individual cases and a greater difference between current and optimal CPP was associated with worse outcome (for patients who, on average, were treated below optimal CPP [R2 = 0.53, p < 0.001] and for patients whose mean CPP was above optimal CPP [R2 = −0.40, p < 0.05]). Following decompressive craniectomy, pressure reactivity initially worsened (median −0.03 [interquartile range −0.13 to 0.06] to 0.14 [interquartile range 0.12–0.22]; p < 0.01) and improved in the later postoperative course. After therapeutic hypothermia, in 17 (70.8%) of 24 patients in whom rewarming exceeded the brain temperature threshold of 37°C, ICP remained stable, but the average PRx increased to 0.32 (p < 0.0001), indicating significant derangement in cerebrovascular reactivity. Conclusions The PRx is a secondary index derived from changes in ICP and arterial blood pressure and can be used as a surrogate marker of cerebrovascular impairment. In view of an autoregulation–guided CPP therapy, a continuous determination of a PRx is feasible, but its value has to be evaluated in a prospective controlled trial.

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“…Magnetic resonance imaging (MRI) (Kassner and Roberts 2004;Kastrup et al 2001;Posse et al 1997), positron emission tomography (PET) (de Boorder et al 2006, Steiner et al 2003, and near infrared spectroscopy (NIRS) (Smielewski et al 1995) techniques have all been used to monitor changes in CBF with changes in PaCO 2 . The most common method used to assess CVR though, is transcranial Doppler ultrasonography (TCD) (Dahl et al 1994;Markwalder et al 1984;Ringelstein et al 1988;Settakis et al 2003).…”

Section: Introductionmentioning

confidence: 99%

Tissue Pulsatility Imaging of Cerebral Vasoreactivity During Hyperventilation

Kucewicz

Dunmire

Giardino

et al. 2008

Ultrasound in Medicine & Biology

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Tissue Pulsatility Imaging (TPI) is an ultrasonic technique that is being developed at the University of Washington to measure tissue displacement or strain due to blood flow over the cardiac and respiratory cycles. This technique is based in principle on plethysmography, an older non-ultrasound technology for measuring expansion of a whole limb or body part due to perfusion. TPI adapts tissue Doppler signal processing methods to measure the "plethysmographic" signal from hundreds or thousands of sample volumes in an ultrasound image plane. This paper presents a feasibility study to determine if TPI can be used to assess cerebral vasoreactivity. Ultrasound data were collected transcranially through the temporal acoustic window from four subjects before, during, and after voluntary hyperventilation. In each subject, decreases in tissue pulsatility during hyperventilation were observed that were statistically correlated with the subject's end-tidal CO 2 measurements.

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Assessment of Cerebrovascular Autoregulation in Head-Injured Patients

Cited by 161 publications

References 32 publications

Critical Closing Pressure: Comparison of Three Methods

Critical Closing Pressure: Comparison of Three Methods

Continuous monitoring of cerebrovascular pressure reactivity in patients with head injury

Tissue Pulsatility Imaging of Cerebral Vasoreactivity During Hyperventilation

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