PATIENT WARMING


falls below 36.0˚C, they should be warmed using forced-air warming.


Warming devices


While these warming measures are not applied often enough, there is no shortage of devices available on the market – from forced air warming devices to resistive heating mattresses. There has been a significant focus on the use of active warming technologies, in recent years – NICE guidance on hypothermia specifically recommends the use of forced air warming (such as the Bair Hugger), or the Inditherm patient warming mattress (based on conductive polymer technology), to help prevent hypothermia. However, there is a plethora of other technologies available on the market which use a variety of different approaches – from a single-use, self-warming blanket, designed to reduce the risk of infection (Barrier EasyWarm); a mattress which uses radiant fabric technology, simultaneously warming above and below the patient (Hot Dog); to a pressure relieving OR table pad, which features conductive heating (PerfecTemp). As with all healthcare technologies, Trusts will need to weigh up the supporting evidence and cost benefits of these solutions.


Infusion and insufflation


While these solutions can help tackle inadvertent perioperative hypothermia, heat loss through the infusion of fluids and gases is also a significant factor that must be addressed.


NICE states that: “intravenous fluids (500 ml or more) and blood products should be warmed to 37˚C using a fluid warming device”.2


This is backed up by a recent systematic review and meta-analysis, by Steelman et al 3 which examined the evidence for the warming of irrigation fluids for prevention of perioperative hypothermia. The authors found that the warming of irrigation fluids for shoulder or hip arthroscopy significantly decreased the risk of hypothermia (odds ratio, 0.15; 95% confidence interval [CI], 0.06-0.40; P = .0001), increased the lowest mean temperature (mean difference, 0.46°C; 95% CI, 0.11°C-0.81°C; P = .01), decreased the maximum temperature drop (mean difference, -0.64°C; 95% CI, -0.94°C to -0.35°C; P < .0001), and decreased the risk of shivering (odds ratio, 0.25; 95% CI, 0.07-0.86; P = .03).


The authors concluded that, when irrigation fluids are warmed for shoulder and hip arthroscopy, the risk of hypothermia is


less, the drop in intraoperative temperature is less, the lowest body temperature is higher, and the risk of postoperative shivering is reduced.


It is not just cold fluids that contribute to hypothermia during surgery. The use of carbon dioxide (CO2


) to fill the peritoneal


cavity, during laparoscopic abdominal surgery, can also contribute to heat loss. With an absence of any recommendations on the warming of insufflation gas in the NICE guidance on hypothermia, this is an area that requires further guidance and research. The publication of MTG 31 (NICE Medical Technology Guidance) has gone some way to addressing this, by providing further insight into a technology that shows ‘promise’ in tackling the issue.4


Why use warm, humidified CO2 ?


A suggested approach to minimising heat loss is to deliver warm, humidified CO2


to


thereby reducing the risk of postoperative complications and their associated costs.9-13


reduce cellular desiccation and evaporative cooling,5-8


Fisher and Paykel, the


manufacturer of the HumiGard device (featured in the NICE MTG 31 guidance), explains that the condition of the CO2


traditionally used during laparoscopic


surgery and the ambient air during open surgery is vastly different to the conditions of the human body, directly drawing heat and moisture from an already compromised patient. Desiccation of the peritoneum occurs


There are some new approaches on the horizon and, if proven, these could add to our understanding of how to optimise the patient’s temperature during surgery


62 I WWW.CLINICALSERVICESJOURNAL.COM


swiftly after exposure resulting in cellular damage and exposure of the basement membrane. Desiccation and associated cooling can manifest in significant post- operative complications including surgical site infections (SSI), cancer metastases and adhesions.13-15


Pain and analgesia use may


also be reduced by the humidification and warming of insufflation gases, according to recent studies. These studies were reviewed by a NICE committee, for the purposes of the MTG.


The evidence-base


The evidence reviewed by NICE included a double-blind randomised controlled trial by Hermann and De Wilde16 which compared HumiGard with unwarmed, dry CO2


gas in


patients having gynaecological laparoscopic surgery.


A cohort of 52 patients received warm


(35±2°C), humidified (98% humidity) CO2 and 52 patients received standard room temperature, dry (0% humidity) CO2


. The


primary outcome was post-operative pain, while secondary outcome measures were morphine consumption and demand and post-operative, patient-controlled analgesia, temperature change during surgery, length of time spent in the recovery room and length of inpatient stay.


The results showed a significant difference in total shoulder tip pain (p=0.037). Temperature change during operation, length of time in recovery room, and inpatient stay in hospital did not differ between groups.


NICE also reviewed a study by Manwaring et al17


which reported on a


randomised controlled trial comparing HumiGard with unwarmed, dry CO2


gas in


women having gynaecologic laparoscopic surgery. Randomisation led to 30 patients receiving warmed, humidified CO2


with SEPTEMBER 2018


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