Unintentional perioperative hypothermia as a risk factor for various complications — including infections

lek. Maciej Szmy­dt

mgr Karoli­na Motyssek

Skamex Sp. z o.o. Sp.k.

Summary

Unin­ten­tion­al peri­op­er­a­tive hypother­mia rep­re­sents a sig­nif­i­cant clin­i­cal prob­lem affect­ing over half of oper­at­ed patients. Com­pli­ca­tions asso­ci­at­ed with it pro­long hos­pi­tal stay and increase treat­ment costs. Inter­na­tion­al guide­lines empha­size the impor­tance of active­ly warm­ing patients. The use of flu­id warm­ing sys­tems in peri­op­er­a­tive care sig­nif­i­cant­ly reduces the risk of peri­op­er­a­tive hypother­mia com­pli­ca­tions, includ­ing infec­tions.

Summary in English:

Inad­ver­tent peri­op­er­a­tive hypother­mia pose a seri­ous clin­i­cal prob­lem that apply to over half of all patients under sur­gi­cal treat­ment. Any med­ical com­pli­ca­tions asso­ci­at­ed to this phe­nom­e­non extend the hos­pi­tal length of stay and at the same time increase costs of treat­ment. Inter­na­tion­al guide­lines empha­sise the sig­nif­i­cance of active patients’ warm­ing. Usage of flu­ids warm­ing sys­tems, in case of peri­op­er­a­tive care, sub­stan­tial­ly decreas­es the risk of peri­op­er­a­tive hypother­mia com­pli­ca­tions includ­ing infec­tions.

Key­words:

hypother­mia ➧ inad­ver­tent peri­op­er­a­tive hypother­mia ➧ infec­tions ➧ sur­gi­cal site infec­tion (SSI) ➧ flu­id warm­ing device ➧ guide­lines hypother­mia ➧ inad­ver­tent peri­op­er­a­tive hypother­mia ➧ infec­tions ➧ sur­gi­cal site infec­tion (SSI) ➧ flu­id warm­ing device, guide­lines ➧ enFLow®

Inadvertent perioperative hypothermia

For sev­er­al decades, dis­cus­sions have been ongo­ing regard­ing peri­op­er­a­tive hypother­mia. These aim to define its main caus­es and to devel­op guide­lines for hos­pi­tal cen­ters due to the poten­tial com­pli­ca­tions and eco­nom­ic con­se­quences asso­ci­at­ed with this phe­nom­e­non.

Peri­op­er­a­tive hypother­mia, defined as a cen­tral body tem­per­a­ture below 36°C, is a com­mon com­pli­ca­tion asso­ci­at­ed with anes­the­sia and sur­gi­cal pro­ce­dures. It is esti­mat­ed that 50–90% of oper­at­ed patients expe­ri­ence inad­ver­tent hypother­mia [1, 2]. The sig­nif­i­cance of this issue is main­ly deter­mined by com­pli­ca­tions occur­ring both dur­ing and after surgery. These include res­pi­ra­to­ry, car­dio­vas­cu­lar, coag­u­la­tion, and elec­trolyte dis­tur­bances, increased sus­cep­ti­bil­i­ty to infec­tions, impaired wound heal­ing, and altered drug metab­o­lism [1, 3, 4]. The caus­es of such com­pli­ca­tions are diverse. The fre­quen­cy and sever­i­ty of peri­op­er­a­tive hypother­mia are influ­enced by con­di­tions in the oper­at­ing room (ambi­ent tem­per­a­ture), main­te­nance of gen­er­al and/or region­al anes­the­sia, the patien­t’s phys­i­o­log­i­cal sta­tus, heat loss from the sur­gi­cal site, and the dura­tion of the pro­ce­dure [3]. Peri­op­er­a­tive hypother­mia is influ­enced by sev­er­al fac­tors. Cur­rent­ly, pas­sive and active patient warm­ing meth­ods are used to main­tain nor­moth­er­mia, includ­ing admin­is­ter­ing warmed intra­venous flu­ids, using ther­mal mat­tress­es or forced-air warm­ing mat­tress­es, and con­trol­ling room tem­per­a­ture [1].

Surgical Procedure and Anesthesia and the Risk of Perioperative Hypothermia 

As a result of the action of many anes­thet­ic agents used in gen­er­al anes­the­sia, there is impair­ment of the ther­moreg­u­la­to­ry mech­a­nism respon­si­ble for main­tain­ing nor­moth­er­mia by widen­ing the thresh­old for vas­cu­lar reac­tions. Dila­tion of pre­cap­il­lary ves­sels caus­es redis­tri­b­u­tion of heat from the cen­tral com­part­ment to periph­er­al com­part­ments of the body. Redis­tri­b­u­tion of heat between the cen­tral and periph­er­al com­part­ments is respon­si­ble for 81% of heat loss. In intra­op­er­a­tive hypother­mia, sev­er­al phas­es can be dis­tin­guished. In the redis­tri­b­u­tion phase, there is a sud­den and rapid decrease in deep body tem­per­a­ture. This tran­si­tions into a lin­ear and uni­form decline in the heat loss phase, lead­ing to a sta­bi­liza­tion phase where ther­moreg­u­la­to­ry mech­a­nisms are acti­vat­ed.

Według danych z pub­likacji tem­per­atu­ra ciała pac­jen­ta pod­danego zabiegowi oper­a­cyjne­mu w znieczu­le­niu ogól­nym może odb­ie­gać od normy nawet o 3°C [7]. W cza­sie zabiegów trwa­ją­cych około 60 min­ut tem­per­atu­ra ciała pac­jen­ta może obniżyć się gwał­town­ie nawet o 1,5°C [6].

Hipotermia podczas dłuższych zabiegów

Dur­ing longer pro­ce­dures under gen­er­al anes­the­sia, there is a slow­ing of metab­o­lism and a decrease in the activ­i­ty of skele­tal mus­cles, lead­ing to heat loss through radi­a­tion and con­vec­tion [5]. The per­cent­age of heat loss for patients is esti­mat­ed to be 60% through radi­a­tion and 10 to 15% through con­vec­tion [8]. Peri­op­er­a­tive hypother­mia is asso­ci­at­ed with pro­longed hos­pi­tal­iza­tion and the imple­men­ta­tion of addi­tion­al phar­ma­co­log­i­cal ther­a­pies, increas­ing the costs of treat­ment. Based on stud­ies con­duct­ed in the USA, it has been esti­mat­ed that a 1.5°C decrease in a patien­t’s body tem­per­a­ture dur­ing peri­op­er­a­tive care results in an addi­tion­al finan­cial bur­den rang­ing from $2500 to $7000 per patient [9].

The dura­tion of the pro­ce­dure and expo­sure of uncov­ered body sur­faces and the sur­gi­cal field increase the risk of inad­ver­tent intra­op­er­a­tive hypother­mia and may affect the post­op­er­a­tive peri­od [3]. Stud­ies by Har­zows­ka have shown that the dura­tion of the pro­ce­dure affects the decrease in the patien­t’s tem­per­a­ture in the post­op­er­a­tive peri­od [1]. More­over, the amount of flu­id trans­fu­sions increas­es. Dur­ing post­op­er­a­tive mon­i­tor­ing, it was found that the amount of non-warmed flu­ids admin­is­tered to the patient sig­nif­i­cant­ly affect­ed the decrease in their body tem­per­a­ture [1]. This con­firms the results of stud­ies con­duct­ed by Sessler in 1997. They showed that admin­is­ter­ing 1000 ml of flu­ids at 21°C (room tem­per­a­ture) can low­er the body tem­per­a­ture by 0.25°C, while admin­is­ter­ing 2000 ml of flu­ids at 4°C low­ers the body tem­per­a­ture by over 1°C [10]. It is there­fore extreme­ly impor­tant to pay atten­tion to the flu­id warm­ing pro­ce­dure because admin­is­ter­ing non-warmed flu­ids to the patient sig­nif­i­cant­ly con­tributes to tem­per­a­ture reduc­tion.

Stages of Perioperative Hypothermia

Ryc. 1. Fazy hipoter­mii około­op­er­a­cyjnej pod­czas znieczu­le­nia ogól­nego na pod­staw­ie Sessler D., 2007 [6] (mody­fikac­ja włas­na).

Perioperative hypothermia and surgical site infections

Hypother­mia affects the fre­quen­cy of sur­gi­cal site infec­tions (SSI) and the rate of wound heal­ing. Sev­er­al pub­li­ca­tions have demon­strat­ed the neg­a­tive impact of decreased body tem­per­a­ture on the activ­i­ty of the immune sys­tem. Reduc­tion in core tem­per­a­ture dis­rupts leukopoiesis, neg­a­tive­ly influ­ences immunoglob­u­lin pro­duc­tion, and con­tributes to reduced blood clot­ting [4]. Hypother­mia triples the risk of sur­gi­cal site infec­tions, lead­ing to a 20% increase in hos­pi­tal­iza­tion time [10]. Research by Flo­res-Mal­don­a­da in 2001 con­firmed the find­ings of Kurz, show­ing increased sus­cep­ti­bil­i­ty to sur­gi­cal site infec­tions in patients with peri­op­er­a­tive hypother­mia com­pared to those with nor­moth­er­mia. In nor­moth­er­mic patients, the inci­dence of wound infec­tion decreased by 89% com­pared to patients with mild hypother­mia (p = 0.01) [11].

Perioperative hypothermia and infections

Hipoter­mia około­op­er­a­cyj­na jest czyn­nikiem zwięk­sza­ją­cym ryzyko zakażeń u pac­jen­tów [11, 12]. Przy­czyny tych zakażeń mają różne podłoże. Z jed­nej strony ogranic­zony dostęp tlenu do miejs­ca oper­owanego (wazokonstrykc­ja) oraz z drugiej, reakc­ja układu odpornoś­ciowego pac­jen­ta [3]. Ogranicze­nie dostępu tlenu do tkanek uniemożli­wia pro­ces syn­tezy wol­nych rod­ników przez neu­tro­file. Dodatkowa inak­tywac­ja komórek układu immuno­log­icznego, spowodowana obniżoną tem­per­aturą, prowadzi do zaburzeń fago­cy­tozy, zre­dukowanej pro­dukcji chemokin, zaburza­jąc trans­fer neu­tro­filów do miejs­ca zakaże­nia [3]. Spadek tem­per­atu­ry głębok­iej desta­bi­lizu­je gospo­darkę białek układu immuno­log­icznego, m.in. białek układu zgod­noś­ci tkankowej, czyn­ni­ka martwicy nowot­worów (TNF‑α) i immunoglob­u­lin, co powodu­je zahamowanie kole­jnego pro­ce­su obron­nego orga­niz­mu oper­owanego pac­jen­ta [3, 11, 12, 13].

Wong et al., in stud­ies con­duct­ed in 2007 on patients under­go­ing elec­tive col­orec­tal surgery, demon­strat­ed that in the group of patients warmed dur­ing the pre‑, intra‑, and post­op­er­a­tive peri­ods, the inci­dence of sur­gi­cal site infec­tion decreased by 60% com­pared to patients warmed only dur­ing the intra­op­er­a­tive peri­od [14].

In a study by Mosle­mi-Kebrii et al. in 2012, con­duct­ed on patients under­go­ing sur­gi­cal cytore­duc­tion for ovar­i­an can­cer, a 71% low­er inci­dence of infec­tions was found in the nor­moth­er­mic group com­pared to the hypother­mic group [15].

The results obtained in the stud­ies by Kurz, con­duct­ed on a group of patients under­go­ing col­orec­tal surgery, con­firmed the effec­tive­ness and supe­ri­or­i­ty of flu­id warm­ing over air warm­ing. In patients warmed only with air, hypother­mia occurred, while in the oth­er group, nor­moth­er­mia was achieved by adding flu­id warm­ing to air warm­ing. In the nor­moth­er­mic group, there was a 67% reduc­tion in the inci­dence of infec­tions and an 18% reduc­tion in hos­pi­tal stay com­pared to patients with hypother­mia [12].

Hipotermia okołooperacyjna – inne powikłania

Hypother­mia, espe­cial­ly in elder­ly patients, can triple the inci­dence of coro­nary events, lead­ing to acute cir­cu­la­to­ry fail­ure, numer­ous com­pli­ca­tions, or death [5, 10]. Main­tain­ing nor­moth­er­mia in these patients reduces the risk of life-threat­en­ing car­dio­vas­cu­lar events [10]. Research by Frank, con­duct­ed on a group of patients under­go­ing vas­cu­lar, tho­racic, and abdom­i­nal pro­ce­dures, showed an 80% reduc­tion in the fre­quen­cy of car­dio­vas­cu­lar inci­dents in the nor­moth­er­mic group com­pared to the group of patients with hypother­mia [16].

Anoth­er com­pli­ca­tion of hypother­mia is the dis­rupt­ed blood coag­u­la­tion cas­cade. It inhibits platelet activ­i­ty, dis­turbs the func­tion of clot­ting fac­tors, includ­ing pro­throm­bin, dis­rupts fib­ri­nol­y­sis, and dis­turbs the coag­u­la­tion enzy­mat­ic bal­ance [4, 5]. Even in patients with mild hypother­mia, clot­ting mech­a­nisms are dis­rupt­ed [4]. These process­es increase blood loss and the need for blood prod­ucts. A meta-analy­sis con­duct­ed by Suman et al., pub­lished in 2008, includ­ed the results of 24 clin­i­cal stud­ies. It showed that patients with nor­moth­er­mia had a 16% low­er need for blood and a 23% low­er risk of trans­fu­sion com­pared to patients with hypother­mia [17]. Research by Schmied, con­duct­ed on patients under­go­ing hip arthro­plas­ty, showed a 23% low­er intra­op­er­a­tive blood loss in nor­moth­er­mic patients com­pared to patients with hypother­mia [18].

Anoth­er con­se­quence of intra­op­er­a­tive hypother­mia is its impact on the patien­t’s emer­gence time, relat­ed to the dis­tur­bance of drug metab­o­lism [4]. This process pro­longs the action of intra­venous anes­thet­ics and mus­cle relax­ants. The dura­tion of action of the intra­venous anes­thet­ic propo­fol is extend­ed by 30%, and the mus­cle relax­ant atracuri­um by 60% [19, 20]. The dura­tion of action of anoth­er neu­ro­mus­cu­lar block­ing agent, vecuro­ni­um, is twice as long in patients with mild hypother­mia com­pared to the nor­moth­er­mic group [21].

Zapobieganie niezamierzonej hipotermii okołooperacyjnej – rekomendacje

The stan­dard pro­ce­dure from the prepa­ra­tion of the patient for surgery until their trans­fer to the post­op­er­a­tive care unit involves ensur­ing and mon­i­tor­ing the patien­t’s phys­i­o­log­i­cal body tem­per­a­ture.

Współczes­na kom­plek­sowa for­muła opie­ki około­op­er­a­cyjnej dla poprawy wyników leczenia ERAS (enhanced recov­ery after surgery) rekomen­du­je ogrze­wanie płynów infuzyjnych w celu utrzy­ma­nia około­op­er­a­cyjnej nor­moter­mii pac­jen­ta [22].

 

RYZYKO POWIKŁAŃ SERCOWYCH	DURATION OF ANESTHESIA
	60 min	60 min	30 min
	Mniejsze zabie­gi chirur­giczne	Zabie­gi chirur­giczne o śred­niej rozległoś­ci	Minor sur­gi­cal pro­ce­dures
HIGH	Ogrze­wanie płynów + Mat­tress­es	Ogrze­wanie płynów + Mat­tress­es	Ogrze­wanie płynów
LOW	Ogrze­wanie płynów	Ogrze­wanie płynów + Mat­tress­es	Ogrze­wanie płynów

Tab. 1. Rekomen­dowane metody akty­wnego ogrze­wa­nia pac­jen­ta w zależnoś­ci od cza­su trwa­nia znieczu­le­nia, rodza­ju zabiegu i ryzy­ka powikłań ser­cowych (na pod­staw­ie NICE, 2008) [23].

Recomendations NICE (National Institute for Clinical Excellence)

Accord­ing to the rec­om­men­da­tions of the Nation­al Insti­tute for Clin­i­cal Excel­lence (NICE), every patient is assessed for the risk of peri­op­er­a­tive hypother­mia. If the core tem­per­a­ture in the pre­op­er­a­tive phase is below 36°C, imme­di­ate mea­sures should be tak­en to restore the patient to nor­moth­er­mia before the start of the sur­gi­cal pro­ce­dure. Active intra­op­er­a­tive patient warm­ing con­tributes to main­tain­ing phys­i­o­log­i­cal body tem­per­a­ture and pre­vents many peri­op­er­a­tive com­pli­ca­tions asso­ci­at­ed with its fluc­tu­a­tions. Guide­lines regard­ing the warm­ing of intra­venous flu­ids and blood prod­ucts are also high­ly sig­nif­i­cant. It is rec­om­mend­ed that before admin­is­tra­tion, flu­ids and blood prod­ucts should be warmed using ded­i­cat­ed devices when the vol­ume exceeds 500 ml, for all patients under­go­ing sur­gi­cal pro­ce­dures last­ing longer than 30 min­utes [23].

Accord­ing to the rec­om­men­da­tions issued by NICE regard­ing the pre­ven­tion of peri­op­er­a­tive hypother­mia, effec­tive and read­i­ly avail­able mea­sures should be employed to pre­vent its occur­rence, such as intra­venous flu­id warm­ing devices and forced-air warm­ing sys­tems [23].

The analy­sis of the effec­tive­ness of applied patient warm­ing meth­ods has shown that com­bin­ing two warm­ing meth­ods, name­ly rou­tine pro­ce­dures along with intra­venous flu­id and blood warm­ing, reduces the risk of peri­op­er­a­tive hypother­mia and relat­ed com­pli­ca­tions, includ­ing infec­tions, by over 50%. Addi­tion­al­ly, adding flu­id warm­ing to oth­er active warm­ing meth­ods such as forced-air warm­ing mat­tress­es allows for a fur­ther 26% reduc­tion in hypother­mia risk and a 29% decrease in hypother­mia-relat­ed com­pli­ca­tions, includ­ing infec­tions [23].

Warm­ing of admin­is­tered flu­ids is always rec­om­mend­ed as the opti­mal strat­e­gy for main­tain­ing nor­moth­er­mia, regard­less of the type of pro­ce­dure, risk of car­diac com­pli­ca­tions, dura­tion of anes­the­sia, or oth­er patient warm­ing meth­ods [23].

Skuteczne ogrzewanie krwi i płynów infuzyjnych

Devices used for warm­ing flu­ids in peri­op­er­a­tive care ensure patient safe­ty in main­tain­ing nor­moth­er­mia and facil­i­tate the work of med­ical staff.

Jakie cechy powinien mieć skuteczny system przepływowego podgrzewania krwi i płynów infuzyjnych?

The main cri­te­ri­on set for man­u­fac­tur­ers of sys­tems for flow heat­ing of flu­ids is their effec­tive­ness. This encom­pass­es sev­er­al fea­tures that such a sys­tem should have. It should ensure main­tain­ing the patien­t’s prop­er tem­per­a­ture by pro­vid­ing a wide range of heat­ing tem­per­a­tures. The ini­ti­a­tion of flu­id heat­ing should be as rapid as pos­si­ble. The sys­tem should allow for high flow rates while main­tain­ing the desired tem­per­a­ture. For blood trans­fu­sions, the sys­tem should have a safe­ty cer­ti­fi­ca­tion issued by inde­pen­dent insti­tu­tions. An essen­tial ele­ment is sim­ple, intu­itive oper­a­tion, and quick device prepa­ra­tion for work. The func­tion­al­i­ty of such a sys­tem also depends on the small vol­ume of ini­tial fill­ing of the car­tridge and the lack of fre­quent ser­vic­ing require­ments. An extreme­ly impor­tant fea­ture is the abil­i­ty to use the device with­out age restric­tions on the patient. An addi­tion­al advan­tage of the heat­ing sys­tem should be the ease of trans­port­ing the device togeth­er with the patient.

Is there a medical device available on the market for flow heating of blood and infusion fluids that exhibits the aforementioned features?

Among the med­ical devices cur­rent­ly avail­able on the mar­ket for flow heat­ing of infu­sion flu­ids and blood, the enFlow® sys­tem (man­u­fac­tured by Care­Fu­sion) deserves atten­tion as it meets all the afore­men­tioned cri­te­ria. The device ini­ti­ates heat­ing of the flow­ing flu­id just 18 sec­onds after con­nec­tion to the patient. Auto­mat­ic set­tings enable reach­ing a tem­per­a­ture of 40°C, aid­ing in main­tain­ing nor­moth­er­mia in the patient. The sys­tem can main­tain a tem­per­a­ture of 40°C even at high flow rates of up to 200 ml/min (12 liters of fluid/hour). The safe­ty of main­tain­ing the qual­i­ty para­me­ters of blood prod­ucts has been con­firmed by the Pol­ish Insti­tute of Hema­tol­ogy and Trans­fu­sion Med­i­cine. The eval­u­a­tion con­duct­ed by the Insti­tute unequiv­o­cal­ly deter­mines that the enFlow® warmer is safe for trans­fused red blood cell con­cen­trates. With a small ini­tial fill­ing vol­ume of the car­tridge (4 ml) and sim­ple, intu­itive oper­a­tion, the sys­tem can be quick­ly pre­pared for use. The device can be used with­out age lim­its. The mobil­i­ty of the enFlow sys­tem, achieved by using a small, portable car­tridge, allows for the main­te­nance of nor­moth­er­mia in patients prac­ti­cal­ly any­where ther­a­py and care are pro­vid­ed. The device is ser­viced every 5 years.

Summary

Numer­ous pub­li­ca­tions indi­cate that main­tain­ing a patient in a state of nor­moth­er­mia through­out the peri­op­er­a­tive peri­od pre­vents com­pli­ca­tions. There­fore, if there are no clin­i­cal indi­ca­tions for induc­ing hypother­mia in a patient, every effort should be made to main­tain nor­moth­er­mia, adher­ing to exist­ing rec­om­men­da­tions. Inad­ver­tent peri­op­er­a­tive hypother­mia occurs very fre­quent­ly and is a cause of many com­pli­ca­tions, includ­ing infec­tions. It can eas­i­ly be avoid­ed by using flu­id warm­ing. Flu­id warm­ing should be applied when infus­ing vol­umes ≥ 500 ml of flu­ids and dur­ing pro­ce­dures last­ing ≥ 30 min­utes. Flu­id warm­ing should always be used, regard­less of oth­er meth­ods of patient warm­ing.

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