Effect of Transient Moderate Hyperventilation on Dynamic Cerebral Autoregulation after Severe Head Injury

Newell, David W.; Weber, Jonas; Watson, R. Scott; Aaslid, Rune; Winn, H. Richard

doi:10.1097/00006123-199607000-00008

Cited by 100 publications

(46 citation statements)

References 40 publications

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“…We found that increased ambient PCO 2 levels were associated with increased odds of autoregulatory failure in the early postoperative period. Previous studies in experimental models and in adult humans have shown similar effects of PCO 2 on CPA (35)(36)(37)(38)(39)(40). Because PCO 2 is vasoactive in the pulmonary vasculature, changes in PCO 2 are used in certain circumstances to adjust pulmonary vascular resistance in infants after cardiac surgery.…”

Section: Postoperative Cerebral Autoregulationmentioning

confidence: 83%

Identification of Pressure Passive Cerebral Perfusion and Its Mediators after Infant Cardiac Surgery

et al. 2005

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Cerebrovascular pressure autoregulation (CPA) regulates cerebral blood flow (CBF) in relation to changes in mean arterial blood pressure (MAP). Identification of a pressure-passive cerebral perfusion and the potentially modifiable physiologic factors underlying it has been difficult to achieve in sick infants. We previously validated the near-infrared spectroscopy-derived hemoglobin difference (HbD) signal (cerebral oxyhemoglobin Ϫ deoxyhemoglobin) as a reliable measure of changes in CBF in animal models. We now sought to determine whether continuous measurements of ⌬HbD would correlate to middle cerebral artery flow velocity (CBFV), allow identification and quantification of pressure-passive state, and help to delineate potentially modifiable factors. We enrolled 43 infants (2 d to 7 mo old) who were undergoing open cardiac surgery and cardiopulmonary bypass. At 6 and 20 h after surgery, we measured changes in HbD, CBFV (by transcranial Doppler), and MAP at different end-tidal CO 2 levels. We assigned a pressure-passive index (PPI) to each study on the basis of the relative duration of significant coherence between ⌬MAP and ⌬HbD. We found a significant relationship between ⌬HbD and ⌬CBFV at both time points. At 6 h after surgery, we showed high concordance (coherence Ͼ0.5; PPI Ն41%) between ⌬MAP and ⌬HbD, consistent with disturbed CPA in 13% of infants. End-tidal CO 2 values Ն40 mm Hg and higher MAP variability both were associated with increased odds (p Ͻ 0.001) of autoregulatory failure. This approach provides a means to identify and quantify disturbances of CPA. High Recent advances in infant cardiac surgery and critical care medicine have translated into high survival rates for infants with congenital heart disease. As mortality has decreased, the clinical focus has shifted to the prevention of perioperative neurologic injury (1). Previous studies have focused primarily on intraoperative cerebral hypoxia-ischemia as a key mechanism for neurologic dysfunction. However, recently it has become clear that multiple potential mechanisms, operating at different times, may be implicated in the pathogenesis of neurologic dysfunction after infant cardiac surgery (2). In the current research, we focused on the early postoperative period because of its high risk for hemodynamic instability and therefore potential for brain injury.

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Section: Postoperative Cerebral Autoregulationmentioning

confidence: 83%

Identification of Pressure Passive Cerebral Perfusion and Its Mediators after Infant Cardiac Surgery

et al. 2005

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“…Decreasing the PCO 2 values from a baseline of 37 to 28 mm Hg results in an improvement in the dynamic ARI. 38 The mechanism of improvement in autoregulation induced by hyperventilation is not clear. Possible mechanisms to account for this improvement may include an improved CPP, alterations in the pH value of the CSF, and increased vascular tone.…”

Section: Hyperventilationmentioning

confidence: 99%

“…38 If an improvement in autoregulation is the result of enhanced vascular tone induced by hypocapnia, then this improvement can be lost if the vascular tone returns to baseline. Moreover, a recent prospective randomized trial of chronic hyperventilation for 5 days in severely head-injured patients did not show a benefit from this treatment.…”

Section: Hyperventilationmentioning

confidence: 99%

Cerebral pressure autoregulation in traumatic brain injury

Rangel-Castilla

Gasco

Nauta

et al. 2008

FOC

183

104

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An understanding of normal cerebral autoregulation and its response to pathological derangements is helpful in the diagnosis, monitoring, management, and prognosis of severe traumatic brain injury (TBI). Pressure autoregulation is the most common approach in testing the effects of mean arterial blood pressure on cerebral blood flow. A gold standard for measuring cerebral pressure autoregulation is not available, and the literature shows considerable disparity in methods. This fact is not surprising given that cerebral autoregulation is more a concept than a physically measurable entity. Alterations in cerebral autoregulation can vary from patient to patient and over time and are critical during the first 4–5 days after injury. An assessment of cerebral autoregulation as part of bedside neuromonitoring in the neurointensive care unit can allow the individualized treatment of secondary injury in a patient with severe TBI. The assessment of cerebral autoregulation is best achieved with dynamic autoregulation methods. Hyperventilation, hyperoxia, nitric oxide and its derivates, and erythropoietin are some of the therapies that can be helpful in managing cerebral autoregulation. In this review the authors summarize the most important points related to cerebral pressure autoregulation in TBI as applied in clinical practice, based on the literature as well as their own experience.

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“…9,[11][12][13]15 In Tiecks' original publication, 9 it is implied that a least-squares method was used to find the best fit in each case. The drawback with this approach is that it depends on another model parameter, namely, the critical closing pressure, that Tiecks et al assumed to be fixed at 12 mm Hg.…”

Section: Years)mentioning

confidence: 99%

“…Clinical applications of the thigh cuff technique have included patients with orthostatic hypotension, 10 carotid artery disease, 11 head injury, [12][13][14] and studies of the effects of anesthetic agents on cerebral autoregulation. 15,16 Despite its increasing use in cerebrovascular research, several aspects of the thigh cuff method have not been described.…”

mentioning

confidence: 99%

Assessment of the Thigh Cuff Technique for Measurement of Dynamic Cerebral Autoregulation

Mahony

Panerai

Deverson

et al. 2000

Stroke

108

113

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Background and Purpose-Dynamic methods of measuring cerebral autoregulation have become an accepted alternative to static evaluation. This article aims to describe a set of data collected from healthy volunteers by a dynamic method, the purpose being to qualify and quantify expected results for those who may be designing a study using this technique. Methods-Cerebral blood flow velocity (CBFV) (measured by transcranial Doppler) and arterial blood pressure (Finapres) were recorded in 16 normal subjects before, during, and after the induction of a blood pressure drop (release of bilateral thigh cuffs). This procedure was repeated 6 times for each subject. A mathematical model was applied to the data to generate an autoregulatory index (ARI) with values between 0 and 9. Results-The ARI values for this sample population follow a normal distribution, with a meanϮSD of 4.98Ϯ1.06 (nϭ15).Analysis of the cumulative mean ARI values of all subjects showed an exponential-type convergence of ARI toward the sample mean as the number of test iterations increased. The population average blood pressure drop on thigh cuff release was 26.4Ϯ7.1 mm Hg (nϭ16), occurring in 4.6Ϯ1.7 seconds. The corresponding population average drop for CBFV was 15.6Ϯ5.8 cm/s, taking 2.5Ϯ1.0 seconds. No significant trend was noted in the measurements as the number of test iterations increased. The correlation between the predicted and actual CBFV, having a mean value of 0.76Ϯ0.19, showed evidence of a nonlinear relationship to ARI values. Significant correlation was also found between ARI and (1) arterial blood pressure before cuff release and (2)

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Effect of Transient Moderate Hyperventilation on Dynamic Cerebral Autoregulation after Severe Head Injury

Abstract: These results confirm the finding that dynamic autoregulation is disturbed in severe head injury and that moderate transient hyperventilation can temporarily improve the efficiency of the autoregulatory response, probably as a result of a transient increase in vascular tone.

Cited by 100 publications

References 40 publications

Identification of Pressure Passive Cerebral Perfusion and Its Mediators after Infant Cardiac Surgery

Identification of Pressure Passive Cerebral Perfusion and Its Mediators after Infant Cardiac Surgery

Cerebral pressure autoregulation in traumatic brain injury

Assessment of the Thigh Cuff Technique for Measurement of Dynamic Cerebral Autoregulation

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