Can nutritional intervention reduce the incidence of pressure sores?

Abstract

Delivering an adequate volume of oxygen at a partial pressure sufficient for cell metabolism is critical for cells and tissues to function normally. Inadequate tissue perfusion and oxygenation has been found to be the most important determinant of wound healing and resistance to infection. 1 The most important risk factor for the development of pressure sores is immobility, which reduces local tissue perfusion. Thus, it seems logical that conditions such as dehydration and smoking, which reduce peripheral microcirculation and oxygenation, may increase risk further. Because nutritional deficiency accompanies pressure ulcers as a result of impaired microcirculation, it is hard to believe that delivery of extra nutrients would reach the local area and reduce the risk of developing pressure sores or improve healing. If, on the other hand, nutritional therapy improves a patient’s overall condition and mobility, this may reduce the pressure sore risk. Oral administration of protein- and energy-rich supplements improves nutritional intake substantially in many different patient populations.3 Among these are patients with lower limb fractures, 4 especially older patients, who are at increased risk of developing pressure sores. In these patients, nutritional therapy increases motility.5 In a thorough review published in 1995, Finucane 6 concluded that the data on the relation between malnutrition and pressure sores were incomplete and contradictory and reported that at that time no randomized trials of tube feeding in the prevention or treatment of pressure sores had been done. A search on MEDLINE (National Library of Medicine, Bethesda, MD) for studies published during the past 20 y revealed one recent randomized nutritional intervention study performed in 129 patients with fractures of the hip.7 Patients who were tube fed had substantially higher energy and protein intakes than did control subjects, but the development and severity of pressure sores were not significantly different between groups. Does the large, carefully conducted multicenter study published in the January issue of Nutrition8 finally establish that nutritional therapy reduces the risk of pressure sore development in the elderly? Unfortunately not. First, oral supplementation resulted in only minor if any improvement in nutritional intake. The intervention patients were heavier than the control patients; thus, after correction for body weight, average intakes for the whole intervention period were nearly the same in the two groups: 20 kcal and 0.8 g protein per kg body weight for the intervention group and 19 kcal and 0.8 g protein for the control group. Second, even though most high-risk patients were in the control group, only a minor difference in the incidence of pressure sores was found: 41% in the intervention group compared with 47% in the control group. This finding is well described by the authors. It is therefore surprising that the relative risk for developing pressure ulcers in the control patients was calculated to be 1.57 when a multivariate Cox proportional hazard model based on a marginal approach was used to compensate for the different risk factors in the two groups. The risk factors used in the statistical calculations are not described in the article and it is therefore hard to believe how a minor difference which was suspected to be further diminished became much bigger. It is also hard to believe that a nutritional intervention that did not improve nutritional intake would reduce the pressure sore risk. There are many good reasons for supplementary feeding in older sick persons, but there are still no studies showing clearly that nutritional intervention reduces pressure sore risk.