Technology update Preventing pressure ulcers occurring on the heel
PATHOPHYSIOLOGY The heel is at increased risk of ulceration due to its posterior prominence and lack of padding over the calcaneus. Gefen[9]
found that
the pressure on the fat pad of the heel when positioned at 90 degrees to the leg during bedrest is higher than when the foot is turned onto the side. Pressure can be applied to the heel during bedrest, and pressure can be higher if the heel is resting in a 'hammock' at the foot of the bed. Hammocks develop when the material of the mattress does not support the heel on the bed leaving the heel hanging in the mattress cover. This intense pressure can lead to ulceration and pain. Shear forces on the heel occur when the patient slides down in bed. The hyperaemic response to pressure
loading on the heel does not differ from other tissue. However, the heel is a unique bony prominence and with aging the number of capillaries are reduced, the amount of soft tissue padding over the calcaneus decreases and blood flow at rest to the heel is relatively low[10]
. Owing to the unique anatomy of the heel
and impaired ability to reperfuse (restoration of the blood flow to a previously ischaemic tissue or organ), the heel is a common site for deep tissue injury pressure ulcers[11,1]
. Salcido et al[3]
correlated the relative risk of deep tissue injury of the heel to the relatively small radius of the calcaneus and thin, overlying tissue. Co-morbid diseases also can impair arterial
inflow and when patients are hospitalised vasoconstriction from medications, hypovolemia or pain can further reduce arterial inflow[12]
patients at risk of pressure ulcers on the heels. The National Database of Nursing Quality Indicators (NDNQI) and a study by Walsh and Plonczynski[14]
focusing on hospital-acquired
pressure ulcers found that they predominantly occur in patients who are at low to mild risk on the Braden assessment tool. Unique intrinsic risk factors for pressure
ulcers on the heels include diseases that impair sensation in the heel (such as diabetic neuropathy, stroke, nerve block after surgery, analgesia), conditions that reduce blood flow to the leg (ie peripheral vascular disease, vasopressive medications) and lower limb weakness (such as hip fracture, total knee replacement) are the most common. Low serum albumin levels were also seen
in the patients with pressure ulcers on the heels[14]
. The calcaneus of the heel is prominent,
extending into the mattress of the bed. Some patients have sharp posterior calcanei, thin soft tissue padding and heavy feet making them at higher risk[9]
, similarly, a 0.8 ankle brachial
pressure index (ABI) provides high sensitivity and adequate specificity to predict pressure ulcer development on the heel. It is recommended that nursing staff use
. Arterial blood flow to the
heel is supplied by the lateral and medial plantar artery and the medial calcaneal branch of the posterior tibial artery [Fig 1]. Differences in blood flow to the heel were seen in patients with ankle-brachial indices lower than 0.8[13]
. Blood flow, via transcutaneous
oxygen levels to the heels, was tested in patients who underwent hip-replacement surgery and had elastic support stocking and sequential compression devices on the legs. Transcutaneous oxygen levels were lower in both heels, and more so in the operative limb during periods of pressure loading and when pressure was removed (unloading)[12]
.
IDENTIFYING HIGH RISK PATIENTS The Braden Scale for detecting pressure ulcer risk has not been shown to consistently identify
a general pressure ulcer risk assessment tool and add risk factors unique to heel ulcers, including poor blood flow to the legs, neuropathy and lower limb weakness. Poor blood flow to the leg can be identified by a history of cardiovascular or peripheral vascular diseases with claudication and/ or physical examination findings of thin, hairless legs, thick toenails, delayed capillary refill times, and/or absent pulses in the foot. Neuropathy can be assessed formally via Semmes-Weinstein monofilament testing or tested generally by asking the patient about pain in the legs or the ability to feel hot bath water, tight shoes or injury to the foot. Neuropathy develops along with the other
end-organ damage seen with diabetes, so if the patient is receiving dialysis or treatment of retinal damage, they probably have neuropathic changes in the feet. Inability to move the leg is tested by asking the patient to move his/her leg in bed — if the patient cannot or will not do so due to pain, the leg should be considered immobile.
PREVENTION METHODS Due to the risk of ulceration to the heel, the high number of cases of heel pressure ulcers and the poor chance of recovery, precautions need to be taken for all patients at bedrest.
References
6. Theiman, GS, Oderich GSC, Ashrafi A, Schneider PA. Management of ischemic heel ulceration and gangrene: An evaluation of factors associated with successful healing. J Vasc Surg 2000; 31: 1110–8.
7. Dosluoglu H, Attuwaybi B, Cherr G, Harris L, Dryjski M. The management of ischemic heel uclers and gangrene in the endovascular era. Am J Surg 2007; 194: 600–05.
8. Han P, Ezquerro R. Surgical treatment of pressure ulcers of the heel in skilled nursing facilities: a 12 year retrospective study of 57 patients. J Am Podiatr 2011; 101(2): 167–75.
9. Gefen A. The biomechanics of heel ulcers. J Tissue Viability 2010; 19(4): 124–31.
10. Abu-Own A, Sommerville K, Scurr J, Coleridge P. Effects of compression and type of bed surface on the microcirculation of the heel. Eu J Vasc Endovas Surg 1995; 9: 327–34.
11.Clegg A, Kring D, Plemmons J, Richbourg L. North Carolina Wound Nurses Examine Heel Pressure Ulcers. J Wound Ostomy Continence Nurs, 2009; 36 (6): 635–39
12.Wong V, Stotts N, Hopf H, Froelicher E, Dowling G. How heel oxygenation changes under pressure. Wound Rep Reg 2007; 15: 786–94
13.Masaki N, Sugarma J, Okuwa M, Inagaki M, Matsuo J, et al. Heel blood flow during loading and off-loading in bedridden older adults with low and normal ankle-brachial pressure index: A Quasi-experimental study. Bio Res for Nurs, 2012 [Epub ahead of print]
14. Walsh J, Plonczynski D. Elevation of a protocol for prevention of facility-acquired heel pressure ulcers. J Wound Ostomy Cont Nurs 2007; 34(2): 178–83.
15. Burdette-Taylor S, Kass J. Heel ulcers in critical care units: A major pressure problem. Critical Care Nursing Quarterly 2002; 25(2): 41–53.
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Technology and product reviews
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