Laser speckle imaging to evaluate scalp flap blood flow during closure in neurosurgical procedures

Abstract

Background: To measure the degree of relative ischemia caused by skin closure, we explored the potential utility of intraoperative surface blood flow measurement with laser speckle imaging (LSI).

Methods: Prospective observational study of eight subjects that underwent intraoperative LSI during elective cranial neurosurgical procedures at the time of skin closure.

Results: Seven 1^st time incisions, with closure techniques including sutures (n = 3), staples (n = 3), and one after galeal sutures. When compared to the control region, there was a mean 63.7% reduction in flow across all seven subjects (range 18.7-95.32%). Comparing by closure type, a higher flow reduction in the three subjects with suture closure (80.7% reduction) compared to staples (61.9% reduction, P = 0.0379). One subject had a complex wound where tightening and loosening of sutures were performed to ensure adequate perfusion. Suturing resulted in significantly more local decreased flow compared to staples (P < 0.0001).

Conclusion: These findings demonstrate the relative feasibility of using LSI for preoperative vascular flow assessment in planning complex incision closure. These data also provide preliminary support for the hypothesis that skin closure itself causes relative ischemia compared to deep approximation or cautery of the skin edge and that the relative ischemia from staples closure is generally less than from suture closure.

Keywords: Laser speckle imaging; Neurosurgical procedure; Scalp flap; Wound ischemia.

Figure 1:

Preincision perfusion study demonstrating the pulsatile flow within the branches of the superficial temporal artery (STA). Black circle with the number 1 inside represents the region of interest (ROI) used for analysis. (a) STA regional surface flow at the trough (b) STA regional surface flow at peak. The graph demonstrates the flow measurements of the scalp at ROI 1, with each pulsation corresponding with the expected heart rate at 1/s. X-axis is the time in seconds and the Y is flux units.

Figure 2:

Mean decrease in perfusion along incision compared to scalp anterior to closure. (a) Graph demonstrating the decrease in blood flow along the incision compared to the scalp anterior to the closure in subjects receiving sutures (n = 3) versus staples (n = 3) versus galea (n = 1). The mean flux within the suture region of interest (ROI) was 72 (St. Dev., 93.5) (unlabeled flux units). When compared to the control region anterior to the closure line, there was a mean 63.7% reduction in flow across all seven subjects (range 18.7–95.32%). When comparing by closure type, we found a significantly higher flow reduction in the three subjects with suture closure (80.7% reduction) compared to staple closure (61.9% reduction, P = 0.0379) (difference of means = 18.8 ± 6.155). The one subject with galeal closure only had the least reduction in flow (18.7% reduction). (b) Flux/perfusion map and corresponding (c) raw speckle image that marks out the incision with a black box ROI and the comparative anterior region in a red box ROI.

Figure 3:

Perfusion study of a complex wound analyzed longitudinally over several interventions. (a) Perfusion map and corresponding (b) raw speckle image that marks the incision with a black box (ROI 1) and the comparative anterior region in a red circle (ROI 2). (c) Graph demonstrating difference in raw flux measurements between suture interventions (loose, tightened, and released) and staple blood flow. A statistically significant difference in mean flow between each of these interventions (P < 0.0001, one-way ANOVA) was found. The mean flux included tightened sutures (126), released sutures (259.7), and staples (157.7) (d) Raw time series data demonstrating the longitudinal flux data from both ROIs over multiple interventions in panel c. These data demonstrate the lack of changes in the control (red) region. Tightening sutures resulted in 23% reduction in flow while complete release resulted in 60% increase in flow. X-axis is the time in seconds and the Y is flux units.