UC UC SF SF Disclosures Vascular Assessment of the Diabetic Foot What are the best predictors of wound healing? None Shant Vartanian MD Assistant Professor of Vascular Surgery UCSF Vascular Symposium April 20, 2013 VASCULAR SURGERY • UC SAN FRANCISCO VASCULAR SURGERY • UC SAN FRANCISCO UC UC SF SF Non-Invasive Vascular Studies Non-Invasive Vascular Studies • Adds objectivity to clinical history and physical exam • Physiologic or Hemodynamic - Ankle brachial index - Toe brachial index • Location and severity of PAD - Pulse volume recordings - Exercise treadmill testing • Potential for primary healing of a wound or surgical • Anatomic imaging incision - Duplex ultrasound • Tissue perfusion • Planning of surgical intervention or amputation level - TcPO2 - SPP (plethysmography, laser doppler) - Spectral imaging (Indocyanine green angiography) VASCULAR SURGERY • UC SAN FRANCISCO VASCULAR SURGERY • UC SAN FRANCISCO 1
UC UC SF SF Ankle Brachial Index VASCULAR SURGERY • UC SAN FRANCISCO VASCULAR SURGERY • UC SAN FRANCISCO Andersen CA J Vasc Surg 2010; 52:Suppl S http://www.nhlbi.nih.gov/health/dci/Diseases/pad/ UC UC SF SF Ankle Brachial Index Ankle Brachial Index • Ankle pressure > 60 mm Hg is required to heal ulceration in non-diabetics • Ankle pressure of > 80 mm Hg for reliable healing in diabetics • More accurate if normalizing to brachial pressure • High rates of healing if ABI > 0.8 Ballard et al • - 66 limbs with diabetic wounds - 89% healed if ABI > 0.6 • ABI < 0.6 associated with need for revascularization • Poor wound healing if ABI < 0.4 VASCULAR SURGERY • UC SAN FRANCISCO VASCULAR SURGERY • UC SAN FRANCISCO 2
UC UC SF SF Ankle Brachial Index Ankle Brachial Index • Common errors - Oversized cuffs - Not measured in supine position • Limitations - Wide distribution of measurements for any given outcome - Falsely elevated in calcified, non-compressible vessels – Diabetes – Renal failure - Ankle pressures may not accurately represent pedal/digit circulation J Vasc Surg 1995 vol. 22 (4) pp. 485-90 VASCULAR SURGERY • UC SAN FRANCISCO VASCULAR SURGERY • UC SAN FRANCISCO UC UC SF SF Toe Brachial Index Toe Brachial Index • Digit pressures - Photoplethysmography – Light emitting diode on distal toe pad – Photocell recieves back-scattered infrared light – Detects increase in flow as cuff is deflated - Continuous wave Doppler – Detects increase in flow as cuff is deflated • Absolute toe pressures < 30 mm Hg - Predicts failure to heal - Increased risk of amputation VASCULAR SURGERY • UC SAN FRANCISCO VASCULAR SURGERY • UC SAN FRANCISCO http://www.nhlbi.nih.gov/health/dci/Diseases/pad/ 3
UC UC SF SF Toe Brachial Index • Meta analysis to calculate sensitivity and specificity of ABI and TBI to predict ulcer healing • Included 220 limbs from 3 studies - 50% were diabetics • Best performance of each test by maximizing ROC - Ankle pressure > 80 mm Hg - Toe pressure > 30 mm Hg • Limitations - Body/room temperature can effect results - Can not discern between fixed obstruction and vasospasm VASA 1998 Nov;27(4):224-8. VASCULAR SURGERY • UC SAN FRANCISCO VASCULAR SURGERY • UC SAN FRANCISCO UC UC SF SF Transcutaneous Oxygen Tension Transcutaneous Oxygen Tension • Measures metabolic state of the skin • Systematic review and meta-analysis • Electrode with heating element placed on skin • 31 studies with 1824 patients and 1960 amputations • Measures oxygen diffusion from skin O 2 reduced at cathode to produce current proportional to TcPO 2 < 40 results in 24% increase in risk of healing - • the partial pressure of oxygen (PO 2 ) complications • Insensitive to mild or moderate PAD Increases further as TcPO 2 decreases - When low, TcPO 2 is not linearly related to flow • • Advantages - Ideal for assessing severe ischemia – Determining amputation level - Can be applied to any area – Patients with previous toe or midfoot amputations - Not affected by arterial calcification VASA 1998 Nov;27(4):224-8. Eur J Vasc Endovasc Surg 2012 vol. 43 (3) pp. 329-36 VASCULAR SURGERY • UC SAN FRANCISCO VASCULAR SURGERY • UC SAN FRANCISCO 4
UC UC SF SF Transcutaneous Oxygen Tension Transcutaneous Oxygen Tension • Limitations - Labor intensive - Time consuming - Many factors effect outcomes – Skin temperature – Room temperature – Sympathetic tone – Active infection – Venous disease – Etc. “Insufficient evidence to judge whether this tool adds important information beyond clinical data or to suggest an optimal threshold value” Eur J Vasc Endovasc Surg 2012 vol. 43 (3) pp. 329-36 VASA 1998 Nov;27(4):224-8. VASCULAR SURGERY • UC SAN FRANCISCO VASCULAR SURGERY • UC SAN FRANCISCO UC UC SF SF Skin Perfusion Pressure Skin Perfusion Pressure • Technique to assess tissue perfusion • 62 limbs in 53 patients with diabetic wounds • Controlled occlusion with cuff • Evaluated healing rate at one month • The pressure at deflation at which circulation in sub- • Stratified results by SPP > 40 dermal capillaries is restored • Circulation measured with a laser doppler • Commercial systems - SensiLase - Perimed • Advantages - Point of care testing - Relatively quick studies - Works on patients with toe amputations VASA 1998 Nov;27(4):224-8. Ann Vasc Dis 2009 vol 2 (1) pp 21-6 VASCULAR SURGERY • UC SAN FRANCISCO VASCULAR SURGERY • UC SAN FRANCISCO 5
UC UC SF SF Skin Perfusion Pressure Comparative Effectiveness Comparison of ABI, TBI, TcPO 2 and SPP in 403 limbs • Limitations • - Diabetes 50% - Sensitive to room temperature - ESRD 21% - Body temperature • SPP measured successfully in 100% - Patient position - ABI 87% (Elevated ABI) - Active infection - TBI 91% (Toe amputation, wound) - TcPO2 94% (Pain) • Healing and amputation rates • Strong correlation between SPP and TBI • For SPP threshold of 40 mm Hg - Sensitivity 72% - Specificity 88% VASA 1998 Nov;27(4):224-8. JVS 2008 vol. 47(2) pp. 318-23 VASCULAR SURGERY • UC SAN FRANCISCO VASCULAR SURGERY • UC SAN FRANCISCO UC UC SF SF JVS 2008 vol. 47(2) pp. 318-23 JVS 2008 vol. 47(2) pp. 318-23 VASCULAR SURGERY • UC SAN FRANCISCO VASCULAR SURGERY • UC SAN FRANCISCO 6
UC UC SF SF Indocyanine Green Angiography • Inert non-radioactive contrast agent administered as IV injection • Laser source to excite fluorescent molecule indocyanine green • Camera captures fluorescence with intensity proportion to the perfusion to a given area • Regional perfusion information • Unknown ability to predict wound healing JVS in press JVS 2008 vol. 47(2) pp. 318-23 VASCULAR SURGERY • UC SAN FRANCISCO VASCULAR SURGERY • UC SAN FRANCISCO UC UC SF SF Indocyanine Green Angiography JVS in press VASCULAR SURGERY • UC SAN FRANCISCO VASCULAR SURGERY • UC SAN FRANCISCO Andersen CA J Vasc Surg 2010; 52:Suppl S 7
UC SF Summary • Single threshold value for non-invasive studies does not always perfectly predict which wounds will heal - Importance of history, exam and clinical course • In diabetics and in renal failure, toe pressures correlate well with ability to heal • SPP appears to work equally as well JVS in press VASCULAR SURGERY • UC SAN FRANCISCO 8
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