Near-infrared spectroscopy (NIRS) has been highlighted as a potentially useful non-invasive clinical tool for continuously monitoring dynamic cerebral autoregulation in sepsis, which is associated with a progressive impairment of cerebral haemodynamic function (Steiner et al, 2009). In the present study, we compared NIRS- to transcranial Doppler ultrasound (TCD)-based assessments of dynamic cerebral autoregulation in patients with severe sepsis. We included ten mechanically ventilated patients (mean age 62, SD 10; 2 females) diagnosed with severe sepsis in the study. Dynamic cerebral autoregulation was assessed by transfer function analysis of spontaneous fluctuations in invasive mean arterial blood pressure and cerebral blood flow, measured by simultaneous ipsilateral and TCD. Bland Altman plots were constructed to compare TCD- and NIRS-based transfer gain and phase estimates in the low frequency range (0.07-0.20 Hz). A total of fifteen simultaneous NIRS- and TCD-based assessments dynamic cerebral autoregulation were obtained in the patients. Bland-Altman plot showed a relative bias of 1.20 cm mmHg-1 sec-1 with limits of agreement of -0.69 to 3.09 cm mmHg-1 sec-1 for transfer gain, and a relative bias of 0.29 radians with limits of agreement of -3.59 to 4.17 radians for phase (Figure). We found a poor agreement between NIRS- and TCD-derived estimates of dynamic cerebral autoregulation in sepsis. In particular, higher TCD-based gain values, which indicate impaired dynamic cerebral autoregulation, were not reflected by correspondingly high NIRS-derived values. This may be related to contamination of the NIRS signal by extracranial tissues, particularly blood flow through the scalp vessels (Toksvang et al, 2014). Our findings thus question the applicability of NIRS for monitoring dynamic cerebral autoregulation in sepsis.
Physiology 2015 (Cardiff, UK) (2015) Proc Physiol Soc 34, C57
Oral Communications: Near-infrared spectroscopy versus transcranial doppler ultrasound for assessing dynamic cerebral autoregulation in clinical sepsis
R. M. Berg1, R. Plovsing1,2
1. Rigshospitalet, Copenhagen, Denmark. 2. Køge Hospital, Køge, Denmark.
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Where applicable, experiments conform with Society ethical requirements.