A Review of the Effects of Sedation on Thermoregulation: Insights for the Cardiac Catheterization Laboratory

Droperidol lowers the shivering threshold in rabbits

PURPOSE

Perioperative shivering is common and can occur as a result of hypothermia or changes in the threshold of thermoregulation. Droperidol usage for anesthesia is currently limited to its sedative and antiemetic effects. We investigated the effects of high and low doses of droperidol on the shivering threshold in rabbits.

METHODS

Forty-two male Japanese white rabbits were anesthetized with isoflurane and randomly assigned to the control, high-dose, or low-dose group. Rabbits in the high-dose group received a 5 mg/kg droperidol bolus followed by continuous infusion at 5 mg/kg/h, those in the low-dose group received a 0.5 mg/kg droperidol bolus, and those in the control group received the same volume of saline as the high-dose group. Body temperature was reduced at a rate of 2-3 °C/h, and the shivering threshold was defined as the subject's core temperature (°C) at the onset of shivering.

RESULTS

The shivering thresholds in the control, high-dose, and low-dose groups were 38.1 °C ± 1.1 °C, 36.7 °C ± 1.2 °C, and 36.9 °C ± 1.0 °C, respectively. The shivering thresholds were significantly lower in the high-dose and low-dose groups than in the control group (P < 0.01). The thresholds were comparable between the high-dose and low-dose groups.

CONCLUSIONS

Droperidol in high and low doses effectively reduced the shivering threshold in rabbits. Droperidol has been used in low doses as an antiemetic. Low doses of droperidol can reduce the incidence of shivering perioperatively and during the induction of therapeutic hypothermia.

Opioid analgesia and temperature regulation are associated with EEG background activity and MRI outcomes in neonates with mild-to-moderate hypoxic-ischemic encephalopathy undergoing therapeutic hypothermia

BACKGROUND

Therapeutic hypothermia (TH) without sedation may lead to discomfort, which may be associated with adverse consequences in neonates with hypoxic-ischemic encephalopathy (HIE). The aim of this study was to assess the association between level of exposure to opioids and temperature, with electroencephalography (EEG) background activity post-TH and magnetic resonance imaging (MRI) brain injury in neonates with HIE.

METHODS

Thirty-one neonates with mild-to-moderate HIE who underwent TH were identified. MRIs were reviewed for presence of brain injury. Quantitative EEG background features including EEG discontinuity index and spectral power densities were calculated during rewarming and post-rewarming periods. Dose of opioids administered during TH and temperatures were collected from the medical charts. Multivariable linear and logistic regression analyses were conducted to assess the associations between cumulative dose of opioids and temperature with EEG background and MRI while adjusting for markers of HIE severity.

RESULTS

Higher opioid doses (β = -0.21, p = 0.02) and reduced skin temperature (β = 0.14, p < 0.01) were associated with lower EEG discontinuity index recorded post-TH. Higher opioid doses (β = 0.75, p = 0.01) and reduced skin temperature (β = -0.39, p = 0.02) were also associated with higher EEG Delta power post-TH. MRI brain injury was observed in 14 patients (45%). In adjusted regression analyses, higher opioid doses (OR = 0.00; 95%CI: 0-0.19; p = 0.01), reduced skin temperature (OR = 41.19; 95%CI: 2.27-747.86; p = 0.01) and reduced cooling device output temperature (OR = 1.91; 95%CI: 1.05-3.48; p = 0.04) showed an association with lower odds of brain injury.

CONCLUSIONS

Higher level of exposure to opioids and reduced skin temperature during TH in mild-to-moderate HIE were associated with improved EEG background activity post-TH. Moreover, higher exposure to opioids, reduced skin temperature and reduced device output temperature were associated with lower odds of brain injury on MRI.

Using a Normothermia Bundle With Perioperative Prewarming to Reduce Patient Hypothermia

PURPOSE

To determine if implementing a normothermia bundle, which includes preoperative forced-air warming blankets, reduces incidence of inadvertent perioperative hypothermia (IPH).

DESIGN

Intervention study using retrospective chart review.

METHODS

Patients received a preoperative forced-air warming blanket and temperature management with the normothermia bundle. Temperature status data was collected from patient charts to evaluate the incidences of IPH and findings from this data analysis was used to measure improvement in perioperative temperature management.

FINDINGS

Of 200 patients, 63 (31.5%) remained normothermic, 37 (18.5%) had at least one documented hypothermic temperature, and 100 (50%) had no documented temperature during the intraoperative phase of care. Although compliance with intraoperative temperature monitoring decreased by 13% postintervention, the incidence of documented IPH in reviewed records was decreased by 3.6-fold.

CONCLUSION

Implementing a normothermia bundle that includes a preoperative forced-air warming blanket may lower the incidences of IPH, especially in surgical cases lasting over 120 minutes.

Does thermal control improve visual satisfaction? Interactions between occupants' self-perceived control, visual, thermal, and overall satisfaction

Occupants' satisfaction had been researched independently related to thermal and visual stimuli for many decades showing among others the influence of self-perceived control. Few studies revealed interactions between thermal and visual stimuli affecting occupant satisfaction. In addition, studies including interactions between thermal and visual stimuli are lacking different control scenarios. This study focused on the effects of thermal and visual factors, their interaction, seasonal influences, and the degree of self-perceived control on overall, thermal, and visual satisfaction. A repeated-measures laboratory study with 61 participants running over two years and a total of 986 participant sessions was conducted. Mixed model analyses with overall satisfaction as outcome variable revealed that thermal satisfaction and visual satisfaction are the most important predictors for overall satisfaction with the indoor environment. Self-perceived thermal control served as moderator between thermal satisfaction and overall satisfaction. Season had slight influence on overall satisfaction. Random effects explained the highest amount of variance, indicating that intra- and interindividual differences in the ratings of satisfaction are more prevalent than study condition. Future building design and operation plans aiming at a high level of occupant satisfaction should consider personal control opportunities and take into account the moderating effect of control opportunities in multimodal interactions.

Cost-effectiveness of forced air warming during sedation in the cardiac catheterisation laboratory

AIM

The aim of this study was to determine the cost-effectiveness of forced air warming (FAW) during sedation in a cardiac catheterisation laboratory.

BACKGROUND

Forced air warming improves thermal comfort in comparison with standard care. It is not known whether the extra costs required for FAW are good value.

DESIGN

Cost-effectiveness analysis alongside a randomized controlled trial conducted in 2016-2017.

METHODS

A cost-effectiveness analysis was undertaken using Monte Carlo simulations from input distributions to estimate costs and effects associated with using FAW to reduce risk of thermal discomfort for patients receiving sedation in a cardiac catheterisation laboratory. A range of willingness to pay threshold values were tested with results plotted on a cost-effectiveness acceptability curve. Costs were calculated in Australian currency ($AUD).

RESULTS

Estimated total costs were $5.21 (SD 3.26) higher per patient for FAW in comparison to standard care. Estimated probability of success (rating of thermal comfort) was 0.16 (0.06) higher for FAW. Forced air warming becomes more likely to result in a net benefit than standard care at a willingness to pay threshold of $34.

CONCLUSION

Forced air warming could be considered cost-effective for procedures performed with sedation in a cardiac catheterisation laboratory if the extra cost of an incremental gain in thermal comfort is less than the decision maker's willingness to pay for it. Therefore, those responsible for decision-making regarding use of FAW in the cardiac catheterisation laboratory can use results of our model to decide if it represents good value for their organisation.

Forced air warming during sedation in the cardiac catheterisation laboratory: a randomised controlled trial

OBJECTIVE

Forced air warming (FAW) during general anaesthesia is a safe and effective intervention used to reduce hypothermia. The objective of this study was to determine if FAW reduces hypothermia when used for procedures performed with sedation in the cardiac catheterisation laboratory.

METHODS

A parallel-group randomised controlled trial was conducted. Adults receiving sedation in a cardiac catheterisation laboratory at two sites were randomised to receive FAW or usual care, which involved passive warming with heated cotton blankets. Hypothermia, defined as a temperature less than 36°C measured with a sublingual digital thermometer after procedures, was the primary outcome. Other outcomes were postprocedure temperature, shivering, thermal comfort and major complications.

RESULTS

A total of 140 participants were randomised. Fewer participants who received FAW were hypothermic (39/70, 56% vs 48/69, 70%, difference 14%; adjusted RR 0.75, 95% CI=0.60 to 0.94), and body temperature was 0.3°C higher (95% CI=0.1 to 0.5, p=0.004). FAW increased thermal comfort (63/70, 90% vs51/69, 74% difference 16%, RR 1.21, 95% CI=1.04 to 1.42). The incidence of shivering was similar (3/69, 4% vs 0/71 0%, difference 4%, 95% CI=-1.1 to 9.8). One patient in the control group required reintervention for bleeding. No other major complications occurred.

CONCLUSION

FAW reduced hypothermia and improved thermal comfort. The difference in temperature between groups was modest and less than that observed in previous studies where use of FAW decreased risk of surgical complications. Therefore, it should not be considered clinically significant.

TRIAL REGISTRATION NUMBER

ACTRN12616000013460.

Forced air warming to maintain normoTHERMIa during SEDation in the cardiac catheterization laboratory: protocol for the THERMISED pilot randomized controlled trial

AIM

To determine whether applying forced air warming attenuates the impact of sedation-induced impairment of thermoregulation on body temperature of patients who are sedated during interventional procedures in the cardiac catheterization laboratory.

BACKGROUND

A moderate proportion of sedated patients who undergo procedures in the cardiac catheterization laboratory with only passive warming become hypothermic. Hypothermia in the surgical population is associated with increased risk of adverse cardiac events, infections, thrombotic and haemorrhagic complications and prolonged hospital stay. For this reason, investigation of the clinical benefits of preventing hypothermia in sedated patients using active warming is required.

DESIGN

Randomized controlled trial.

METHODS

A total of 140 participants undergoing elective interventional procedures with sedation in a cardiac catheterization laboratory will be recruited from two hospitals in Australia. Participants will be randomized to receive forced air warming (active warming) or usual care (passive warming with heated cotton blankets) throughout procedures. The primary outcome is hypothermia (defined as temperature less than 36°C) at the conclusion of the procedure. Secondary outcomes are postprocedure temperature, postprocedural shivering, thermal discomfort, major complications, disability-free survival to 30 days postprocedure, cost-effectiveness and feasibility of conducting a larger clinical trial.

DISCUSSION

The results from this study will provide high-level evidence for practice in an area where there is currently no guidance. Findings will be easily translatable into clinical practice because most hospitals already have forced air warming equipment available for use during general anaesthesia.

REGISTRATION NUMBER

ACTRN12616000013460.

Inadvertent Hypothermia After Procedural Sedation and Analgesia in a Cardiac Catheterization Laboratory: A Prospective Observational Study

OBJECTIVES

To identify the prevalence of and risk factors for inadvertent hypothermia after procedures performed with procedural sedation and analgesia in a cardiac catheterization laboratory.

DESIGN

A single-center, prospective observational study.

SETTING

A tertiary-care private hospital in Australia.

PARTICIPANTS

399 patients undergoing elective procedures with procedural sedation and analgesia were included. Propofol infusions were used when an anesthesiologist was present. Otherwise, bolus doses of either midazolam or fentanyl or a combination of these medications was used.

INTERVENTIONS

None

MEASUREMENTS AND MAIN RESULTS

Hypothermia was defined as a temperature<36.0°C. Multivariate logistic regression was used to identify risk factors. Hypothermia was present after 23.3% (n = 93; 95% confidence interval [CI] 19.2%-27.4%) of 399 procedures. Sedative regimens with the highest prevalence of hypothermia were any regimen that included propofol (n = 35; 40.2%; 95% CI 29.9%-50.5%) and the use of fentanyl combined with midazolam (n = 23; 20.3%; 95% CI 12.9%-27.7%). Difference in mean temperature from pre-procedure to post-procedure was -0.27°C (standard deviation 0.45). Receiving propofol (odds ratio [OR] 4.6 95% CI 2.5-8.6), percutaneous coronary intervention (OR 3.2; 95% CI 1.7-5.9), body mass index<25 (OR 2.5; 95% CI 1.4-4.4) and being hypothermic prior to the procedure (OR 4.9; 95% CI 2.3-10.8) were independent predictors of post-procedural hypothermia.

CONCLUSIONS

A moderate prevalence of hypothermia was observed. The small absolute change in temperature observed may not be a clinically important amount. More research is needed to increase confidence in the authors' estimates of hypothermia in sedated patients and its impact on clinical outcomes.