Feasibility of optical coherence tomography angiography to assess changes in retinal microcirculation in ovine haemorrhagic shock

Abstract

BackgroundThis study aimed to investigate the feasibility of optical coherence tomography angiography (OCT-A) for quantitative analysis of flow density to assess changes in retinal perfusion in an experimental model of haemorrhagic shock.MethodsHaemorrhagic shock was induced in five healthy, anaesthetized sheep by stepwise blood withdrawal of 3 × 10 ml∙kg− 1 body weight. OCT-A imaging of retinal perfusion was performed using an OCT device. Incident dark-field illumination microscopy videos were obtained for the evaluation of conjunctival microcirculation. Haemodynamic variables and flow density data in the OCT angiogram were analysed before and during progressive haemorrhage resulting in haemorrhagic shock as well as after fluid resuscitation with 10 ml∙kg− 1 body weight of balanced hydroxyethyl starch solution (6% HES 130/0.4). Videos of the conjunctival microcirculation were recorded at baseline, in haemorrhagic shock, and after resuscitation. Data are presented as median with interquartile range. Comparisons between time points were made using Friedman’s test and the degree of correlation between two variables was expressed as Spearman’s rank correlation coefficient.ResultsMean arterial pressure and cardiac index (CI) decreased and lactate concentration increased after induction of shock, and haemodynamics recovered after resuscitation. The flow density in the superficial retinal OCT angiogram decreased significantly after shock induction (baseline 44.7% (40.3; 50.5) vs haemorrhagic shock 34.5% (32.8; 40.4); P = 0.027) and recovered after fluid resuscitation (46.9% (41.7; 50.7) vs haemorrhagic shock; P = 0.027). The proportion of perfused vessels of the conjunctival microcirculation showed similar changes. The flow density measured using OCT-A correlated with the conjunctival microcirculation (perfused vessel density: Spearman’s rank correlation coefficient ρ = 0.750, P = 0.001) and haemodynamic parameters (CI: ρ = 0.693, P < 0.001).ConclusionsRetinal flow density, measured using OCT-A, significantly decreased in shock and recovered after fluid therapy in an experimental model of haemorrhagic shock. OCT-A is feasible to assess changes in retinal perfusion in haemorrhagic shock and fluid resuscitation.Electronic supplementary materialThe online version of this article (10.1186/s13054-018-2056-3) contains supplementary material, which is available to authorized users.

Optical coherence tomography angiography as a novel approach to contactless evaluation of sublingual microcirculation: A proof of principle study

“…In contrast, the manual determination of PVD by OCTA and PVD by IDF focused on the length of microvessels (<20 μm) in an area of interest. However, in this context it is noteworthy that in a recent study we show that automatically calculated retinal flow density showed concordant changes with conjunctival measured PVD by IDF in hemorrhagic shock and resuscitation in sheep 25 . Further studies are needed to investigate the relationship between automatically calculated flow density and manually measured parameters of microcirculatory analysis in critical illness and during interventions in patients.…”

“…As a result, the use of OCTA in ophthalmic research and clinical practice has become widespread in recent years [15][16][17][18][19][20][21][22][23] . Recent experimental studies have demonstrated the potential usefulness of OCTA for evaluating microcirculatory alternations in critical illness by investigating the microcirculatory changes in the retina during hemorrhagic shock, septic shock and resuscitation 24,25 .…”

“…For its use in critically ill patients (where abnormalities of the microcirculation are commonly present), the OCTA device would have to be modified. In this context, a OCTA device has been introduced, which enables imaging in recumbent patients (Flex-Modul for SPECTRALIS ® , Heidelberg Engineering GmbH, Heidelberg, Germany) 25 . In addition, hand-held OCTA devices have been presented 40,41 .…”

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

“…After ovine haemorrhagic shock [ 123 ], SVP flow density on OCTA decreased from 44.7% baseline to 34.5%, recovering to 46.9% after fluid resuscitation, correlating with systemic haemodynamic parameters. Conjunctival microcirculation assessed using IDF microscopy also showed a reduced proportion of perfused vessels from 100% to 72%, which returned to 98.7% after resuscitation [ 123 ].…”

Influence of mydriasis on optical coherence tomography angiography imaging in patients with age-related macular degeneration

“…Many studies have investigated factors influencing OCTA metrics such as motion artifacts and image quality [12–16], age and gender [17–22], spherical equivalent and axial length [13–25] and systemic diseases [26–31] and thereby indicated how to apply and interpret OCTA most adequately. There is very little literature on the influence of mydriasis on quantitative OCTA parameters such as flow density (FD), foveal avascular zone (FAZ), signal strength index (SSI) or motion artifact score (MAS) for image quality.…”