Assessment of Effective Hepatic Blood Flow in Critically Ill Patients by Noninvasive Pulse Dye-Densitometry

Background. Conditions of reduced perfusion are characterized by redistribution of blood flow away from the skin to more vital organs. Objectives. To assess the efficacy of a noninvasive, dermal blood flow (DBF) monitor in detecting changes in perfusion in critically ill patients. Methods. Eleven adult, critically ill patients in a general ICU were studied. DBF, finger plethysmography, and invasive mean arterial pressure (MAP) were recorded over an 8-hour period. DBF was measured using the DermaFlow DBF monitor via a skin probe placed on the anterior chest wall. Sensitivity was evaluated by visual inspection during active states, either induced, for example, fluid administration, or spontaneous, for example, altered hemodynamics, while specificity was evaluated during stable states. Data are expressed in terms of standard deviation of the difference (SDD) between the MAP and each of the tested methods. Results. The DBF detected all true changes detected by MAP while plethysmography detected fewer of these events. Based on SDD, the specificity of the DBF was found to be better than that of plethysmography and close in value to the MAP. Conclusions. This preliminary study suggests that the DBF monitor may be a useful noninvasive method for detecting changes in perfusion in critically ill patients.

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Retinal blood flow in critical illness and systemic disease: a review

Annals of Intensive Care ◽

10.1186/s13613-020-00768-3 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

E. Courtie ◽

T. Veenith ◽

A. Logan ◽

A. K. Denniston ◽

R. J. Blanch

Keyword(s):

Blood Flow ◽

Critical Illness ◽

Critically Ill ◽

Critically Ill Patients ◽

Systemic Disease ◽

Retinal Blood Flow ◽

Main Body ◽

Parallel Mechanisms ◽

Coronary Syndrome ◽

Potential Biomarker

Abstract Background Assessment and maintenance of end-organ perfusion are key to resuscitation in critical illness, although there are limited direct methods or proxy measures to assess cerebral perfusion. Novel non-invasive methods of monitoring microcirculation in critically ill patients offer the potential for real-time updates to improve patient outcomes. Main body Parallel mechanisms autoregulate retinal and cerebral microcirculation to maintain blood flow to meet metabolic demands across a range of perfusion pressures. Cerebral blood flow (CBF) is reduced and autoregulation impaired in sepsis, but current methods to image CBF do not reproducibly assess the microcirculation. Peripheral microcirculatory blood flow may be imaged in sublingual and conjunctival mucosa and is impaired in sepsis. Retinal microcirculation can be directly imaged by optical coherence tomography angiography (OCTA) during perfusion-deficit states such as sepsis, and other systemic haemodynamic disturbances such as acute coronary syndrome, and systemic inflammatory conditions such as inflammatory bowel disease. Conclusion Monitoring microcirculatory flow offers the potential to enhance monitoring in the care of critically ill patients, and imaging retinal blood flow during critical illness offers a potential biomarker for cerebral microcirculatory perfusion.

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