Predicting successful lumbar plexus block using blood flow index measured by laser speckle contrast imaging

Abstract Background: Laser speckle contrast imaging (LSCI) is a powerful optical imaging technique for real-time and dynamic measurement of regional blood flow. The objective of this prospective observational study was to investigate blood flow after changes blockade of lumbar plexus or its three major branches respectively, with LSCI technique.Methods: This study included 47 adult patients scheduled for elective lower limb surgery. For the selective blockade of lumbar plexus, femoral nerve, obturator nerve, and lateral femoral cutaneous nerve, blood flow images and pinprick sensory scores of the blocked lower limb were recorded 5 min pre block and every 5 min for 30 min post block. Blood flow index (BFI) values of toes were calculated by LSCI software.Results: In this study, we have 21 cases of successful lumbar plexus blocks, 2 cases of failed lumbar plexus block, 8 cases of successful femoral nerve blocks, 8 cases of successful obturator nerve blocks, and 8 cases of successful lateral femoral cutaneous nerve blocks. The BFI values of all five toes were significantly increased as early as 5 min after successful lumbar plexus block, whereas no signiﬁcant difference was found in BFI values after failed lumbar plexus block. BFI changes after successful selective blockade of femoral nerve, obturator nerve, or lateral femoral cutaneous nerve were negligible. BFI value of the big toe at 5 min after the successful lumbar plexus block was increased by 2.57 fold compared with the baseline value, which represented the highest increase among five tested toes. BFI value of the big toe at 10 min after lumbar plexus block showed great power to predict block outcome with a sensitivity of 100% and a speciﬁcity of 100%. The optimal cut-off value given by ROC analysis was 22.11 PU.Conclusions: Increased blood flow index measured by laser speckle contrast imaging is a reliable indicator of successful lumbar plexus block, but cannot indicate successful selective blocks of three major branches of the lumbar plexus. BFI value of the big toe at 10 min after lumbar plexus block could well predict block outcome with the cut-off value of 22.11 PU.Trial registration: NCT03169517 (Date of registration: May 25, 2017).

Download Full-text

Predicting successful lumbar plexus block using blood flow index measured by laser speckle contrast imaging

10.21203/rs.2.14429/v2 ◽

2020 ◽

Author(s):

Xi Wu ◽

Pengcheng Li ◽

Xiaohu Liu ◽

Liangwei Meng ◽

Dan Wang ◽

...

Keyword(s):

Blood Flow ◽

Femoral Nerve ◽

Laser Speckle ◽

Lateral Femoral Cutaneous Nerve ◽

Lumbar Plexus ◽

Flow Index ◽

Contrast Imaging ◽

Laser Speckle Contrast Imaging ◽

Lumbar Plexus Block ◽

Plexus Block

Abstract Background: Laser speckle contrast imaging (LSCI) is a powerful optical imaging technique for real-time and dynamic measurement of regional blood flow. The objective of this prospective observational study was to investigate blood flow changes after blockade of lumbar plexus or its three major branches respectively, with LSCI technique. Methods: This study included 47 adult patients scheduled for elective lower limb surgery. For the selective blockade of lumbar plexus, femoral nerve, obturator nerve, and lateral femoral cutaneous nerve, blood flow images and pinprick sensory scores of the blocked lower limb were recorded 5 min pre block and every 5 min for 30 min post block. Blood flow index (BFI) values of toes were calculated by LSCI software. Results: In this study, we have 21 cases of successful lumbar plexus blocks, 2 cases of failed lumbar plexus block, 8 cases of successful femoral nerve blocks, 8 cases of successful obturator nerve blocks, and 8 cases of successful lateral femoral cutaneous nerve blocks. The BFI values of all five toes were significantly increased as early as 5 min after successful lumbar plexus block, whereas no signiﬁcant difference was found in BFI values after failed lumbar plexus block. BFI changes after successful selective blockade of femoral nerve, obturator nerve, or lateral femoral cutaneous nerve were negligible. BFI value of the big toe at 5 min after the successful lumbar plexus block was increased by 2.57 fold compared with the baseline value, which represented the highest increase among five tested toes. BFI value of the big toe at 10 min after lumbar plexus block showed great power to predict block outcome with a sensitivity of 100% and a speciﬁcity of 100%. The optimal cut-off value given by ROC analysis was 22.11 PU. Conclusions: Increased blood flow index measured by laser speckle contrast imaging is a reliable indicator of successful lumbar plexus block, but cannot indicate successful selective blocks of three major branches of the lumbar plexus. BFI value of the big toe at 10 min after lumbar plexus block could well predict block outcome with the cut-off value of 22.11 PU.

Download Full-text

Guidelines for obtaining an absolute blood flow index with laser speckle contrast imaging

10.1101/2021.04.02.438198 ◽

2021 ◽

Author(s):

Smrithi Sunil ◽

Sharvari Zilpelwar ◽

David A Boas ◽

Dmitry D Postnov

Keyword(s):

Blood Flow ◽

Speckle Pattern ◽

Quantitative Measure ◽

Laser Speckle ◽

Flow Index ◽

Scattering Media ◽

Contrast Imaging ◽

Laser Speckle Contrast Imaging ◽

Speckle Contrast ◽

Blood Flow Index

Laser speckle contrast imaging (LSCI) is a technique broadly applied in research and clinical settings for full-field characterization of tissue perfusion. It is based on the analysis of speckle pattern contrast, which can be theoretically related to the decorrelation time - a quantitative measure of dynamics. A direct contrast to decorrelation time conversion, however, requires prior knowledge of specific parameters of the optical system and scattering media and thus is often impractical. For this reason, and because of the nature of some of the most common applications, LSCI is historically used to measure relative blood flow change. Over time, the belief that the absolute blood flow index measured with LSCI is not a reliable metric and thus should not be used has become more widespread. This belief has resulted from the use of LSCI to compare perfusion in different animal models and to obtain longitudinal blood flow index observations without proper consideration given to the stability of the measurement. Here, we aim to clarify the issues that give rise to variability in the repeatability of the quantitative blood flow index and to present guidelines on how to make robust absolute blood flow index measurements with conventional single-exposure LSCI. We also explain how to calibrate contrast to compare measurements from different systems and show examples of applications that are enabled by high repeatability.

Download Full-text

Nephron blood flow dynamics measured by laser speckle contrast imaging

AJP Renal Physiology ◽

10.1152/ajprenal.00417.2010 ◽

2011 ◽

Vol 300 (2) ◽

pp. F319-F329 ◽

Cited By ~ 34

Author(s):

Niels-Henrik Holstein-Rathlou ◽

Olga V. Sosnovtseva ◽

Alexey N. Pavlov ◽

William A. Cupples ◽

Charlotte Mehlin Sorensen ◽

...

Keyword(s):

Blood Flow ◽

Signal Transmission ◽

Experimental Studies ◽

Flow Dynamics ◽

Laser Speckle ◽

Tubuloglomerular Feedback ◽

Contrast Imaging ◽

Laser Speckle Contrast Imaging ◽

Speckle Contrast ◽

Blood Flow Dynamics

Tubuloglomerular feedback (TGF) has an important role in autoregulation of renal blood flow and glomerular filtration rate (GFR). Because of the characteristics of signal transmission in the feedback loop, the TGF undergoes self-sustained oscillations in single-nephron blood flow, GFR, and tubular pressure and flow. Nephrons interact by exchanging electrical signals conducted electrotonically through cells of the vascular wall, leading to synchronization of the TGF-mediated oscillations. Experimental studies of these interactions have been limited to observations on two or at most three nephrons simultaneously. The interacting nephron fields are likely to be more extensive. We have turned to laser speckle contrast imaging to measure the blood flow dynamics of 50–100 nephrons simultaneously on the renal surface of anesthetized rats. We report the application of this method and describe analytic techniques for extracting the desired data and for examining them for evidence of nephron synchronization. Synchronized TGF oscillations were detected in pairs or triplets of nephrons. The amplitude and the frequency of the oscillations changed with time, as did the patterns of synchronization. Synchronization may take place among nephrons not immediately adjacent on the surface of the kidney.

Download Full-text