Rafi Sheikh

Optimal Epinephrine Concentration and Time Delay to Minimize Perfusion in Eyelid Surgery: Measured by Laser-Based Methods and a Novel Form of Extended-Wavelength Diffuse Reflectance Spectroscopy

OBJECTIVE This study investigates the hypoperfusion effects of epinephrine in local anesthesia in eyelid surgery. A novel form of extended-wavelength diffuse reflectance spectroscopy was evaluated. METHODS Blood perfusion in porcine eyelid flaps was measured using laser Doppler velocimetry and laser speckle contrast imaging, whereas the tissue response was measured using diffuse reflectance spectroscopy with a broad spectrum (450-1550 nm). Epinephrine was either injected cumulatively, 0.1 (1:10,000,000), 1.0 (1:1,000,000), 10 (1:100 000), and 100 μg/ml (1:10 000), to determine the dose-response relation, or given as a single dose (10 μg/ml). Control experiments were performed with saline or lidocaine. RESULTS Increasing concentrations of epinephrine resulted in a gradual decrease in tissue perfusion, measured by laser Doppler velocimetry and laser speckle contrast imaging, approaching a minimum after the injection of 10 μg/ml. Similar tissue response was observed with diffuse reflectance spectroscopy. The time from the injection of epinephrine (10 μg/ml) to the stabilization of hypoperfusion was 75 seconds. After administration of 10 μg/ml epinephrine, about 20% of the blood perfusion remained, supporting the use of epinephrine in eyelid flaps with a narrow pedicle. CONCLUSIONS 10 μg/ml epinephrine appears to be adequate for vasoconstriction before oculoplastic surgery. Incisions need only be delayed for about 1 minute. Extended-wavelength diffuse reflectance spectroscopy appears to be a promising technique for monitoring the tissue response following changes in blood perfusion in plastic surgery reconstructions. However, more rigorous validation of the technique is required before it can be implemented in clinical practice.

A waiting time of 7 min is sufficient to reduce bleeding in oculoplastic surgery following the administration of epinephrine together with local anaesthesia

The time taken to reach maximal haemostatic effect following local anaesthesia with epinephrine is generally believed to be <10 min. This is based on clinical experience and indirect measurements of perfusion using methods such as laser Doppler flowmetry and oxygen spectroscopy. However, the only study in which bleeding has been measured quantitatively in an intra‐operative setting in humans showed that the full haemostatic effect was not achieved until 30 min after anaesthesia. The aim of this study was to determine the time taken to reach maximum haemostatic effect when using epinephrine for local anaesthesia in oculoplastic surgery.

A novel surgical technique employing donor sclera in strabismus surgery

We describe a novel surgical technique employing donor sclera as a spacer to solve the problem encountered in complicated cases of restrictive strabismus surgery when no more muscle or tendon is available for surgical extension of the eye muscle to correct the angle of deviation. This is often the case in patients who have previously undergone extensive surgery and in patients with mechanical restrictions, such as thyroid-associated orbitopathy (TAO).

Large Eyelid Defect Repair Using a Free Full-Thickness Eyelid Graft

Summary: Large eyelid full-thickness defects are traditionally repaired using flaps with a blood-supplying pedicle, for the reconstruction of the anterior or posterior lamella or both. This is a 2-stage procedure involving occlusion of vision in the affected eye for 4–8 weeks, as the flap pedicle is not divided until vascularization is deemed adequate. However, the importance of using a flap with a pedicle to ensure adequate perfusion of the graft has recently been questioned.

Hypoperfusion following the injection of epinephrine in human forearm skin can be measured by RGB analysis but not with laser speckle contrast imaging

BACKGROUND The time taken for epinephrine to achieve its optimal effect during local anesthesia has recently become the subject of debate. The time from injection to commencement of surgery is traditionally quoted to be 7 to 10 min, while recent reports claim that it may take 30 min to achieve maximum hypoperfusion, which would prolong the time required for surgical procedures. The discrepancy may be related to difficulties associated with the techniques used to measure blood perfusion. The aim of this study was to test two methods of determining the time to maximum hypoperfusion. METHODS Laser speckle contrast imaging (LSCI) and red, green, blue (RGB) analysis of images obtained with a commercial digital camera, were used to monitor the effect of infiltration with commonly used local anesthetic preparations: lidocaine (20 mg/ml) + epinephrine (12.5 μg/ml), lidocaine (10 mg/ml) + epinephrine (5 μg/ml), and lidocaine (20 mg/ml) alone, in healthy subjects. RESULTS LSCI showed a paradoxical increase in signal after the injection of local anesthetics containing epinephrine, probably due to a change in the laser penetration depth resulting from blanching of the skin. However, RGB analysis of digital photographs gave more reliable results, showing skin blanching that corresponded to the expected effect of epinephrine in local anesthetics. The time to maximum effect was found to be 7 (range 5-10) minutes for 12.5 μg/ml epinephrine, and 9 (range 7-13) minutes for 5 μg/ml epinephrine in lidocaine. CONCLUSIONS RGB analysis of digital images proved to be a valid technique for monitoring the effect of local anesthetics with epinephrine in human skin. The technique requires only a commercial digital camera and constitutes a cheap, simple method. The optimal delay between epinephrine injection and incision, to minimize bleeding, was found to be 7 to 9 min, which is in good agreement with common surgical practice.

Identification of tumor margins using diffuse reflectance spectroscopy with an extended-wavelength spectrum in a porcine model

A novel extended‐wavelength diffuse reflectance spectroscopy (EWDRS) technique is being developed for future clinical non‐invasive tumor margin delineation. In this study, the ability of EWDRS to identify the margins of pigmented skin lesions in an in vivo pig model was evaluated.

Blood perfusion in Hewes tarsoconjunctival flaps in pigs measured by laser speckle contrast imaging

Background Hewes flap is a tarsoconjunctival eyelid flap, based at the lateral canthal tendon, and rotated and stretched to repair lateral defects in the lower eyelid commonly following tumor surgery. The aim of the present study was to monitor perfusion in a Hewes flap during reconstruction, which to the best of our knowledge, has not previously been done. Methods A Hewes tarsoconjunctival eyelid flap was raised and the effects on blood perfusion of rotating the flaps by 90° and 180°, stretching the flaps with a force of 5 or 10 N, and repeated diathermic coagulation was monitored with laser speckle contrast imaging. Results Rotating the flaps by 90° did not significantly affect perfusion, while further rotation to 180° reduced blood perfusion to 75% of the baseline value. When the tarsoconjunctival flaps were both rotated 90° and stretched with 5 N, the perfusion was reduced even further, to 63%. A further reduction in perfusion, to 36%, was seen when the higher force of 10 N was applied. Diathermy decreased blood perfusion to 56% after being applied once. Successive applications led to further decreases: 43%, 31%, and 15%, after the second, third and fourth applications. Conclusions Perfusion in Hewes tarsoconjunctival flaps is affected by both rotation and stretching, but some perfusion is maintained despite these manipulations. Diathermy, however, has detrimental effects and should be avoided.