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Death After Lower Limb Amputation

May 12, 2018
 

Study answers questions of risk difference based on demographics.

The objectives of this article are to describe postoperative mortality after lower-limb amputation in a large cohort of patients with diabetes and then to investigate whether postoperative mortality differs by 1) population demographic factors, 2) health system factors, and 3) patient-level factors related to comorbidity.

Although the exception rather than the norm, death in the days and weeks immediately after a surgical procedure is not uncommon.  In a U.S. study of 360,000 patients who underwent procedures between 2005 and 2007, a 30-day mortality rate of 1.75%, or 6,395 deaths, was observed. Nearly one-quarter of all postoperative deaths occur after the patient has been discharged from the hospital. When examining postoperative mortality, a threshold of 30 days after surgery is a valid and meaningful measure for two key reasons. First, a 30-day threshold is less influenced by events that take place during or immediately after surgery and will include the impact of postoperative care in the weeks after the procedure. Second, because postoperative infections typically occur within 28 days of surgery, a 30-day threshold allows for the life course of these infections.

A national prevalent cohort of 302,339 individuals diagnosed with diabetes between 2005 and 2014 were followed until the end of 2014 for major and minor lower-limb amputation and subsequent postoperative mortality by using national health data collections.

A total of 6,352 lower-limb amputations occurred over the study period (2,570 major amputations, 3,782 minor amputations). More than 11% of patients who underwent major amputation died within 30 days, whereas nearly 18% died within 90 days. Death was most common among older patients. Sex, deprivation, rurality, hospital volume, admission type, and patient comorbidity were not consistently or substantially independently associated with risk of postoperative mortality.

They observed that 1 of every 10 patients (11%) who underwent a major amputation died within 30 days of their procedure, and 1 in 6 (18%) died within 90 days. Death was less frequent among those who underwent a minor amputation but not insubstantially, with 3% having died within 30 days and 6% within 90 days. Although this rate of postoperative mortality is substantial, it is consistent with other diabetes literature, including a systematic review of mortality after lower-limb amputation.

Although male patients were more likely to require an amputation in the first place, little difference existed between the sexes in terms of adjusted risk of postoperative mortality, consistent with other research. This finding suggests that female patients who undergo amputation are similar to their male counterparts in terms of underlying risk factors for postoperative mortality. Patients in the oldest age-group were at the greatest risk of death for both amputation types and, in relative terms, were at particularly high risk of mortality after a minor amputation. Those 75 years of age (and older?) had four times the risk of dying within 30 days following a minor amputation than those 50–64 years of age. This finding is consistent with other diabetes studies that observed differences in post-amputation mortality outcomes between younger and older patients, indicating that risk of postoperative mortality is the greatest among the elderly. Amputation procedures undertaken in older patients of 75 or older group must be well justified on the basis of health need or potential benefit and accompanied by high-quality postoperative care.

Step-by-step adjustment revealed that ethnicity had the greatest impact on explaining differences in post-amputation mortality between these age groups. Although the crude model showed that patients 75 years of age (and older) were at 34% greater risk of mortality within 30 days of a major amputation than those 50–64 years of age (and after adjustment for sex, had no impact [still 33%]), adjusting for ethnicity caused this disparity to increase to 62%.

From the results, it was concluded that In a national prevalent cohort of patients with diabetes, there was high risk of postoperative mortality as well as a differential risk of postoperative mortality by demographic subgroup. Further work is required to investigate the drivers of postoperative mortality among patients with diabetes who undergo amputation.

Practice Pearls:

  • Amputation procedures undertaken in patients in the 75-years-of-age-or-older group must be well justified on the basis of health need or potential benefit and accompanied by high-quality postoperative care.
  • More than 11% of patients who underwent major amputation died within 30 days, whereas nearly 18% died within 90 days.
  • Lower limb amputation is one of the most serious surgical procedures performed in patients with diabetes.

Diabetes Care 2018 Apr; dc172557. https://doi.org/10.2337/dc17-2557