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 Non-Invasive Vascular Studies Non-Invasive Vascular Studies Adds objectivity to clinical history and physical exam Location and severity of PAD Potential for primary healing of a wound or surgical incision Planning of surgical intervention or amputation level Physiologic or Hemodynamic - Ankle brachial index - Toe brachial index - Pulse volume recordings - Exercise treadmill testing Anatomic imaging - Duplex ultrasound Tissue perfusion - TcPO2 - SPP (plethysmography, laser doppler) - Spectral imaging (Indocyanine green angiography) 1
Andersen CA J Vasc Surg 2010; 52:Suppl S http://www.nhlbi.nih.gov/health/dci/diseases/pad/ 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 2
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 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 http://www.nhlbi.nih.gov/health/dci/diseases/pad/ 3
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 Transcutaneous Oxygen Tension Transcutaneous Oxygen Tension Measures metabolic state of the skin Electrode with heating element placed on skin Measures oxygen diffusion from skin - O 2 reduced at cathode to produce current proportional to the partial pressure of oxygen (PO 2 ) Insensitive to mild or moderate PAD 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 Systematic review and meta-analysis 31 studies with 1824 patients and 1960 amputations TcPO 2 < 40 results in 24% increase in risk of healing complications - Increases further as TcPO 2 decreases Eur J Vasc Endovasc Surg 2012 vol. 43 (3) pp. 329-36 4
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 Skin Perfusion Pressure Skin Perfusion Pressure Technique to assess tissue perfusion Controlled occlusion with cuff The pressure at deflation at which circulation in subdermal 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 62 limbs in 53 patients with diabetic wounds Evaluated healing rate at one month Stratified results by SPP > 40 Ann Vasc Dis 2009 vol 2 (1) pp 21-6 5
Skin Perfusion Pressure Comparative Effectiveness Limitations - Sensitive to room temperature - Body temperature - Patient position - Active infection Comparison of ABI, TBI, TcPO 2 and SPP in 403 limbs - Diabetes 50% - ESRD 21% SPP measured successfully in 100% - ABI 87% (Elevated ABI) - 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% JVS 2008 vol. 47(2) pp. 318-23 JVS 2008 vol. 47(2) pp. 318-23 JVS 2008 vol. 47(2) pp. 318-23 6
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 2008 vol. 47(2) pp. 318-23 JVS in press Indocyanine Green Angiography JVS in press Andersen CA J Vasc Surg 2010; 52:Suppl S 7
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 8