Factors affecting perioperative body temperature

Survival at 30 days in elderly patients with hip fracture surgery who were exposed to hypothermia: Survival study

The effect of hypothermia as a mortality risk factor at 30 days in the elderly who had hip fracture (HF) surgery is still controversial because it may be due to a set of poorly identified factors. In this study, we aim to determine if exposure to intra and immediate postoperative hypothermia increases the incidence of mortality at 30 days in elderly patients who had HF surgery.Survival study in the elderly who had HF surgery with and without exposure to hypothermia. Sociodemographic, anesthetic and surgical factors were collected. The temperature of the rectum was measured at the end of the surgery and in the recovery room. The effect of hypothermia was analyzed by the incidence of mortality at 30 days. Other results were considered, such as, surgical site infection (SSI), blood transfusions, and influence of implants used in the 30-day mortality.Three hundred eighty five subjects were eligible, to include 300. Inadvertent hypothermia was 12%, the 30-day overall mortality was 9% and in subjects with hypothermia it was 25% (P = .002). Subjects with hypothermia had a higher risk of SSI (relative risk 4.2, 95% confidence interval 1.3-13.6, P = .03) and receive more transfusions (relative risk 3.6, 95% confidence interval 2.0-6.5, P < .001).Elderly subjects with HF exposed to hypothermia who undergo hip hemiarthroplasty and who receive 2 or more blood transfusions during their treatment, are at greater risk of dying after 30 days of the surgery. Hypothermia, as a possible causative factor of mortality, should continue to be studied.

Preoperative Warming Reduces Intraoperative Hypothermia in Total Joint Arthroplasty Patients

INTRODUCTION

Perioperative hypothermia (PH) is common in patients undergoing total joint arthroplasty (TJA). A previous study at our institution identified the largest drop in core body temperature between preoperative holding and induction of anesthesia. This study evaluates the effect of preoperative warming measures on PH in TJA patients.

METHODS

A retrospective review was conducted of 672 patients undergoing TJA at our institution between April 1 and October 31, 2017. Under the new normothermia protocol, patients received warmed intravenous fluids and forced-air warming gowns in the preoperative holding area. Time and temperature data for the perioperative period were collected from the electronic health record. Chi-square and paired t-tests were used to compare between total knee arthroplasty and total hip arthroplasty patients and between new and old protocols.

RESULTS

In the new protocol, 173 of 672 (26%) patients were hypothermic at incision compared with 140 of 383 (37%) patients in the previous protocol (P < 0.05). The largest drop in core body temperature occurred between preoperative holding and induction of anesthesia. The duration of time from operating room entry to incision was less for normothermic than for hypothermic patients. The duration of hypothermia was similar between new and old protocols overall, but markedly fewer total hip arthroplasty patients remained hypothermic for the entire surgery under the new protocol.

CONCLUSION

Adding forced-air warming preoperatively to our warming protocol reduced the rate of PH by approximately 30%. The time from entry into the operating room to the start of surgery should be minimized because patients are vulnerable to PH during this interval.

Hypothermia in Total Joint Arthroplasty: A Wake-Up Call

BACKGROUND

Total joint patients are particularly vulnerable to perioperative hypothermia (PH) (combined effects of anesthesia, radiation, and convective heat loss from exposed skin surfaces and cool temperatures in the operating room). There are limited studies on PH in these patients.

METHODS

In a retrospective review of 204 patients undergoing primary hip and 179 undergoing primary knee replacement surgeries, time and temperature parameters were collected from the electronic health records from preoperative and postoperative recovery room nursing assessments, intraoperative anesthesia records, and floor nursing notes. Basic patient demographic data was recorded. Chi-squared and paired t-tests were used to compare between hypothermic and normothermic groups.

RESULTS

At the time of incision, 60 of 179 (34%) total knee arthroplasty (TKA) patients and 80 of 204 (39%) total hip arthroplasty (THA) patients were hypothermic. In THA patients, 65% remained hypothermic for the duration of anesthesia compared to 33% of TKA patients. The largest drop in core body temperature in both THA and TKA patients occurred between preoperative holding and induction of anesthesia. In THA patients, spinal anesthesia had a significantly higher occurrence of PH. No significant patient factor was found to increase risk.

CONCLUSION

Emphasis on preoperative holding protocols, decreasing time from operating room entry to incision, and increasing ambient room temperature could reduce risk of hypothermia in total joint replacement patients.

A Systematic Review of Intraoperative Warming to Prevent Postoperative Complications

This systematic review examines whether preventing hypothermia during surgery prevents postoperative complications and thereby improves outcomes for patients. Twenty-six randomized controlled trials were identified, and data extraction and assessment of study quality were carried out by two researchers independently. The results of studies with similar patients, surgical procedures, and outcomes were pooled. Outcomes measured included postoperative pain levels, thermal comfort, and treatment costs. Postoperative complications identified were shivering, cardiac events, need for blood transfusion, wound infections, and pressure ulcers. The majority of studies favored treatment.

Minimizing perioperative adverse events in the elderly

Elderly patients still have the highest postoperative mortality and morbidity rate in the adult surgical population. Preoperative clinical assessment to detect patients at high risk of postoperative events, and specific intraoperative and postoperative anaesthesia management are important to minimize postoperative adverse events in the elderly.

Effects of warming therapy on pressure ulcers--a randomized trial

Postoperative pressure ulcers are a common and expensive problem. Intraoperative hypothermia also is a common problem and may have a connection with impaired tissue viability. Researchers in this study hypothesized that intraoperative control of hypothermia may reduce the incidence of postoperative pressure ulcers. A randomized clinical trial (n = 338) was used to test the effects of using forced air warming therapy versus standard care. Results indicated an absolute risk reduction in pressure ulcers of 4.8% (i.e., 10.4% to 5.6%) with a relative risk reduction of 46% in patients who received warming therapy. Although not reaching statistical significance, the clinical significance of almost halving the pressure ulcer rate is important. A correlation between body temperature and postoperative pressure ulcers was established.

A patient temperature audit within a theatre recovery unit

Hypothermia in the postoperative recovery phase can be a source of potential danger for patients emerging from anaesthesia. In spite of the vast amount of literature dealing with principles of care in the recovery room, information regarding the incidence of hypothermia appear very limited. This article presents a patient temperature audit to assess whether patients were being discharged from a theatre recovery unit hypothermic. In addition, patient temperatures were recorded both pre- and postoperatively, as well as on discharge from recovery, to monitor the incidence of hypothermia throughout the theatre suite. The results show that patients were being discharged with core body temperatures ranging from 34.8 to 38 degrees C with no incidence of hypothermia recorded when the operating room temperature was above 23 degrees C. In general, the coldest theatres were orthopaedic, with this group of patients showing the most incidence of hypothermia. This article aims to demonstrate the use of clinical audit to investigate and evaluate current practice.

The prevention of pressure ulcers in the operating department

An innovative approach using a multiple-study research programme that incorporated five individual projects, each of which can be interpreted independently or as an integral part of the whole

Inadvertent hypothermia prevention: the anaesthetic nurses' role

Up to 90% of patients experience hypothermia perioperatively. Inadvertent hypothermia can have a profound physiological effect on the body, varying from mild vasoconstriction and feeling cold to cardiac arrest and death. Anaesthesia, general or regional, increases the risk as the normal protective reflexes such as shivering are absent, particularly when muscle relaxants are used. The very young and the elderly are particularly vulnerable. Preoperative assessment is essential. The greatest reduction in temperature occurs in the first hour of surgery, as a result of patient exposure, skin disinfection with cold fluids, inhalation of cold volatile gases and the administration of cold intravenous fluids, as well as exposure to cool theatre temperatures. If the theatre temperature drops below 21 degrees C, all patients will develop hypothermia. Patients lose heat through radiation, convention and conduction, with conduction having the greatest effect. Forced air warmers such as the Bair Hugger are the most effective means of preventing and treating heat loss. They should be used routinely although their contribution to infection also needs to be considered. Nurses should be aware of the risks of hypothermia so that modes of prevention can be employed to minimize the risks of inadvertent hypothermia.

External rewarming and age in mildly hypothermic patients after cardiac surgery

OBJECTIVE

To compare the effects of two external rewarming methods on body core temperature and the rate of rewarming between two age groups (less than 65 years, 65 years or more) of adult, mildly hypothermic patients who have undergone cardiac surgery, during the immediate postoperative period.

DESIGN

Stratified, randomized clinical trial.

SETTING

Five-bed cardiac surgical intensive care unit in a large teaching-research institution.

SUBJECTS

Thirty-two white patients who had undergone cardiac surgery and who had mildly hypothermic body core temperatures (33 degrees to 35 degrees C) immediately after the surgery.

OUTCOME MEASURES

Body core temperature was measured with a pulmonary artery catheter thermistor at the time of external rewarming method application and at 60, 90, and 150 minutes afterward. Rate of rewarming was measured as body core temperature change in degrees Celsius per hour (at 36.6 degrees C, minus body core temperature when external rewarming method was applied, divided by total rewarming time). Temperatures were recorded six times at intervals of 15 minutes; then every 30 minutes until a value of 36.6 degrees C was obtained, at which time the blanket was removed; then hourly for 8 hours.

INTERVENTION

Either a fluid-filled circulating blanket (active-conductive external rewarming) or a reflective blanket (passive-reflective external rewarming) was applied immediately after core temperature was measured on admission to the cardiac surgical intensive care unit after surgery.

RESULTS

External rewarming methods affected body core temperature differently at different times, and there were significant differences in body core temperature across the time periods (p < 0.05). Both active and passive external rewarming methods showed a sigmoidal rewarming pattern without a downward temperature drift. The fluid-filled circulating blanket produced a quicker and steeper body core temperature change in the early rewarming phase; the reflective blanket resulted in a more gradual temperature rise. Age did not significantly affect body core temperature, nor did age or external rewarming method significantly influence the rate of rewarming, although total rewarming time was longer for those of more advanced age. Seven subjects with passive rewarming method experienced body core temperature overshoot during the 8-hour period after blanket removal.

CONCLUSIONS

In this study, conduction and reflection of radiant heat were equally effective in producing an acceptable rate of rewarming but contributed to different internal patterns in core rewarming. The average total rewarming time with the active external rewarming method was 1 hour shorter than with the passive external rewarming method.

Postoperative temperature and infection in patients undergoing general surgery

During a study concerned with postoperative hypothermia, Closs (1985) noted an association between patients' core temperatures in the immediate postoperative period and respiratory infection. In this paper, a small follow-up study is reported in which the relationship between postoperative temperature and the development of infection (respiratory, wound or urinary tract) was investigated in 41 patients who underwent general surgery. Aural and oral core temperatures were monitored at 270, 300 and 330 minutes following return to the ward postoperatively. In the week following surgery, patients were monitored daily for any sign or symptom of infection. Reference was made to the patient, nursing notes, medical notes and physiotherapist (when available). Seven of the 16 patients (44%) exhibiting an aural core temperature of greater than or equal to 37.8 degrees C between 270 and 330 minutes post-return to ward developed infection while five of the 25 patients (20%) exhibiting an aural core temperature of less than 37.8 degrees C developed infection. Oral temperature measurements (using ward mercury-in-glass thermometers) showed a very similar pattern. Overall, infection was detected in 12 of the 41 patients (29%) in the 6 days following surgery, 11 having a respiratory infection and one a wound infection.