PATIENT CARE
9.15%, while the incidence of hypothermia was 13.25%. However, the mortality of patients with hypothermia was 29.9% with a threefold independent risk of death. Independent determinants for
hypothermia were pre-hospital intubation, Injury Severity Score (ISS), Arrival Systolic Blood Pressure (ASBP) <100 mm Hg: 3.04, and winter time. The authors concluded that seriously
injured patients with accidental hypothermia have a higher mortality independent of measured risk factors. For patients with multiple injuries a coordinated effort by paramedics, nurses and doctors is therefore required to focus efforts toward early resolution of hypothermia – aiming to achieve a temperature >35˚C.
Surgery Temperature management in the hospital setting is also vital. In 1994, Blackburn suggested that as many as 70% of all patients undergoing surgical procedures develop inadvertent hypothermia.3
‘Debate over the pros and cons of convective vs conductive technologies is likely to continue – Trusts will have to consider the available evidence and make their own evaluations.’
with significantly increased morbidity and mortality rates – 12% of the hypothermic patients died, compared to 1% of the normothermic patients.5 Similarly, in a study of 562 patients by
Studies
undertaken by Flores-Maldonado et al, in 2001, also showed that 40% to 60% of patients suffer from pre-operative hypothermia.4 Factors contributing to inadvertent
hypothermia include patients lying on cold operating theatre tables, heat loss from open body cavities, exposure to cold ambient temperatures in the preoperative and surgical suites, a reduction in metabolic heat production (i.e. no muscle activity), room-temperature antimicrobial skin preparations and IV fluids, various forms of anaesthesia (vasodilation) and various pharmacological agents. To combat these factors, numerous
clinical studies have evidenced that patients benefit from being actively warmed prior to, during and after surgery. It is now widely acknowledged that perioperative hypothermia is associated with poorer patient outcomes – including increased risks of surgical site infection, cardiac complications, and bleeding; as well as an associated increase in treatment costs, prolonged hospitalisation and mortality. Following a study of 262 patients
having aortic aneurysm surgery, Bush et al found that hypothermia is associated
Mahoney, 6% of hypothermic patients died, compared with almost 3% of normothermic patients. Hypothermia can also increase the risk of the patient suffering a myocardial infarction (MI). After surgery, when the body temperature begins to return to normal, the metabolic rate increases with shivering and vasoconstriction occurs, which increases arterial blood pressure, putting extra demands on the heart. The Bush and Mahoney studies prove this point – 7.5% of hypothermic patients in the Bush study had an MI compared to 4% of normothermic patients. In the Mahoney study, 4% of hypothermic patients had an MI compared to 2% of normothermic patients.6 Studies undertaken by Bush, Mahoney and Kurtz7 all demonstrate that
hypothermic patients take longer to recover – spending an average of 10 days longer in hospital. At the Infection Prevention Society’s
recent annual conference (2012) Judith Tanner, professor of clinical nursing research, De Montford University, also reported that patient warming was found to be one of the most significant factors in reducing surgical site infection, following an initiative to reduce infections at her Trust. Judith Tanner and colleagues at Leicester found that patients who had no pre-op warming had a superficial SSI rate of 22%. For patients that were pre-op warmed, the superficial SSI rate was 0%. Hypothermia also appears to have a
significant effect on patient satisfaction, anxiety and pain management. A recent study highlighted the fact that active warming leads to a reduced requirement for pain relief after surgery. Benson et al conducted a prospective, randomised controlled trial to determine the efficacy of
The air-free full body blanket and torso blanket formpart of the Hot Dog range fromNordic Surgical.
a patient-controlled active warming gown in optimising patients’ perioperative body temperature and in diminishing postoperative pain after total knee arthrosplasty (TKA).8 Thirty patients who would be
undergoing TKA received either a standard hospital gown and prewarmed standard cotton blanket (n=15) or a patient-controlled, forced-air warming gown (n=15). Although pain scores were not
significantly different in the two groups (P=0.08), patients who received warming gowns had higher temperatures (P<0.001) in the post-anaesthesia care unit, used less opioid (P=0.05) after surgery, and reported more satisfaction (P=0.004) with their thermal comfort than patients who received standard blankets. The authors concluded that patient-
controlled, forced-air warming gowns can enhance perioperative body temperature and improve patient satisfaction. Patients who use warming gowns may also need less opioid to manage their postoperative pain. They recommended that nurses should ensure that effective patient warming methods are employed in all patients, particularly in patients with compromised thermoregulatory systems (such as older adults), and in surgeries considered to be exceptionally painful (such as TKA).
Patient warming approaches Strategies for maintenance of perioperative normothermia include passive insulation and active warming. Various studies have indicated that active methods are more efficient than passive insulation in maintaining perioperative normothermia – this may include convective, conductive and fluid warming approaches. Blood/fluid warming: Research by
Sessler et al has shown that each litre of intravenous fluids infused into adult surgical patients at ambient temperature, or each unit of blood infused at 4˚C, decreases the mean body temperature approximately 0.25˚C.9
Blood/fluid
warming devices can help overcome this problem and maintain normothermia when used in conjunction with other patient warming technologies. There are numerous devices available – one such device is the enFlow IV fluid and blood warmer from GE.
56 THE CLINICAL SERVICES JOURNAL NOVEMBER 2012
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