Inadvertent hypothermia in the operating theatre: an examination.
KEY WORDS Inadvertent hypothermia, Intraoperative surgery, Student operating department practitioner
Inadvertent hypothermia is one of the most commonly and frequently reported complications in surgical patients (Surkitt-Parr 1992). Research into this subject matter clearly indicated that as early as 1880 hypothermia was a major concern for patients (Surkitt-Parr 1992). Since it has been estimated that as many as 70% of surgical patients suffer some degree of hypothermia (Litwack 1995, cited in Arndt 1999), this is a subject that cannot be overlooked and attempting to lower this almost unbelievably high percentage can only lead to better patient care.
As a second year student operating department practitioner undertaking a surgery module, I chose to explore inadvertent hypothermia, because it is an aspect of patient care that is not always fully understood and managed efficiently.
The purpose of this article is therefore to explore in-depth the condition, classifications, anatomy, physiology and consequences of inadvertent hypothermia and the management of the patient's temperature while undergoing surgical procedures. Integrated throughout, the author will be highlighting the role of the perioperative practitioner in caring for patients.
Definition and classifications of hypothermia
Hypothermia is defined as a condition in which the core of the body is less than 36[degrees]C in temperature (ASPAN 2001). Of the many classifications of hypothermia, the American College of Surgeons in 1989 recognises three. These are mild: 32-35[degrees]C; moderate: 30-32[degrees]C; and severe: below 30[degrees]C (Keane 2001), with various symptoms that transpire in relation to these classes (McNeil 1997) (see Figure 1).
[FIGURE 1 OMITTED]
The normal physiology of temperature control in the body is regulated by a combination of behavioural and physiological responses. Behavioural responses include, for example, if a person is hot they will move to a cooler place and remove clothing; and the skin becoming more perfused with blood and the person sweats. Likewise if a person is cold they will move to a warmer place and don more clothing, the blood circulation to the skin is decreased and the person shivers (Kumar 1998).
Body temperature is balanced by heat loss and heat production, thus maintaining normothermia between 35.6[degrees]C to 37.8[degrees]C (Marieb 2004). Although other brain regions contribute, the hypothalamus, which consists of a heat promoting and heat loss centre, is the brain's thermoregulatory centre (Marieb 2004). The hypothalamus, upon receiving input from peripheral thermoreceptors located in the skin and central thermoreceptors sensitive to blood temperature located in the body core (the organs within the skull and the thoracic and abdominal cavities), responds like a thermostat to this input by reflexively initiating appropriate heat-promoting or heat-loss activities via autonomic pathways, allowing the hypothalamus to anticipate changes of the core temperature (Marieb 2004).
When blood temperature falls or external temperature is low, the heat-promoting centre is activated. Vasoconstriction of the arteries and arterioles occur controlling the amount of blood in the capillaries of the dermis, thus conserving heat. Brain centres controlling muscle tone are activated, increasing tone by stimulating stretch receptors: muscles involuntary contract, and shivering occurs (Marieb 2004) (see Figure 2).
[FIGURE 2 OMITTED]
Cold produces norepinephrine and thyroxin, this is released elevating the metabolic rate thus increasing heat production (Marieb 2004). Heat production is also produced from the liver and the digestive organs (Waugh & Grant 2001).
When body temperature rises the heat-loss centre is activated, vasodilation of blood vessels occurs, as blood vessels swell with warm blood, heat is lost from the skin by radiation, conduction and convection. Autonomic nerve stimulation of sweat glands produces secretion of perspiration, which vaporizes, resulting in evaporation (Marieb 2004) (see Figure 2).
Heat is lost mainly from the skin, but also from expired air, faeces and urine. Air passing over exposed parts of the body becomes heated and therefore rises, cool air then replaces it and convection currents are established. Exposed skin radiates heat away from the body and anything touching the skin, including clothes, will conduct the heat away from the body (Waugh & Grant 2001). Radiation is the largest contributor to heat loss as 60% of body heat is lost by infra-red heat waves (Radford et al 2004). Evaporation occurs through sweating and exposed tissues (Waugh & Grant 2001).
Causative factors of hypothermia
Although all patients undergoing surgery are at risk of developing perioperative hypothermia (Sessler 1997, Beattie & Christopherson et al 1992, cited in ASPAN 2001), various contributing risk factors may increase the risk of hypothermia in surgical patients (Sessler 1997, Emery & Freemantle 1989, cited in ASPAN 2001), along with other causative risk factors pertaining to the surgical patient McNeil 1997, 1998) (see Table 1). Some of these causative factors relating to prolonged fasting, premedication and insufficient clothing, can be rectified prior to surgery by an early assessment of at risk' patients on the ward, sufficient patient coverings (McNeil 1998) and minimal fasting time of six hours (Sunderland et al 1986, cited in Kumar 1998).
Management and prevention of hypothermia
Inadvertent hypothermia during surgery is alleged to be inadvertent because it develops accidentally during a period when a person's normal protective reflexes are absent (McNeil 1998). Embodied within the role of all perioperative practitioners are various strategies, when utilised, pertaining to minimising hypothermia when caring for surgical patients in the operating theatre.
Perioperative practitioners can, upon observing the operating list and liaising with other members of the multi-disciplinary theatre team, identify risk factors for unplanned hypothermia prior to and during surgery. They can initiate the provision of warming devices and warming measures to reduce the causative factors as much as possible.
Exposure of patients prior to surgery can be reduced by perioperative practitioners implementing the use of passive insulation such as warmed cotton blankets, socks and head coverings, thus ensuring that skin exposure is limited (ASPAN 2001).
Depending upon the type of surgical procedure a patient is undergoing, the use of a circulating water mattress can be initiated, connected and applied on top of the operating table (ASPAN 2001). Warming mattresses are acceptable to use as they do not interfere with the surgical field. However as more than two thirds of body's surface needs to be in contact with the mattress, they are of limited value for patients undergoing hip surgery (McNeil 1997).
Another forced-warm air device, which produces a thermal-focused environment by blowing warm air through a disposable quilt covering the patient, is deemed to be the most effective means of warming patients. Preventing heat loss via radiation and convection, this device should be used on all 'at risk' patients (Arndt 1999). Perioperative practitioners should, when this device is in use, monitor the patient's temperature to prevent overheating. Caution should be taken with patients undergoing vascular surgery, as these devices should not be used on patients with severe peripheral vascular disease (McNeil 1998). Once normothermia is reached the airflow speed and forced air temperature should be reduced or the blanket turned off (McNeil 1998).
Operating theatre temperature
The required ambient temperature in the operating theatre suite should be between 20-24[degrees]C to minimise the growth of bacteria (Rothrock 2003). However this can be detrimental to the patient when anaesthetised, as their body temperature will vary according to environmental conditions (McNeil 1997). Therefore to maintain a patient's core temperature at 36[degrees]C or above the perioperative practitioner should increase the ambient operating room temperature (ASPAN 2001) from 21[degrees]C to 24[degrees]C, thereby ensuring the comfort of staff and patients (McNeil 1998).
When preparing to start any operating list, it is the perioperative practitioner's responsibility to decide whether the temperature is at the recommended level. Surgery must not be performed if it is below 20[degrees]C, in order to minimise inadvertent hypothermia, while the temperature must not exceed 24[degrees]C in order to minimise bacterial growth (Rothrock 2003). Perioperative practitioners should monitor the air conditioning and ventilation system as when in use they promote air currents, draughts and heat loss via convection and radiation. The more efficient the air conditioning, for example laminar flow, the more the loss (McNeil 1998).
On admission to the department prior to surgery, the patient's temperature should be checked and various means of measuring the patient's temperature during surgery applied or prepared (ASPAN 2001). These could be invasive such as an oesophageal temperature probe, which measures core body temperature, or a nasopharyngeal temperature probe, which measures brain temperature. Alternatively, a non-invasive device, such as a probe attached to the toe that measures peripheral temperature, a 'stick on' thermometer, measuring skin temperature, or a tympanic thermometer could be used (Kumar 1998). By monitoring the above methods used to measure patient temperature the perioperative practitioner can evaluate and adjust some of the warming devices and systems used, thus ensuring the patient's temperature remains normothermic.
Exposure of patients
In the operating theatre minimum exposure of the patient should be addressed. Once the patient is on the operating table, the perioperative practitioner can ensure that instead of removing blankets to facilitate the application of monitoring, diathermy plate and pressure relieving aids, they remain in place by folding the blankets back then re-covering the exposed skin (McNeil 1998).
In order to prevent heat loss by exposure of the operation site, the perioperative practitioner must ensure the blankets remain in position until the surgeon is ready to prep the area. Once ready, the blankets can be folded back ensuring as much as possible of the body is covered (McNeil 1998). Consideration of warming skin preparation solutions and cleaning lotions--excluding those that are alcohol-based--prior to use should also be taken into account as cold solutions and lotions when applied cause heat loss via evaporation (Radford et al 2004). When draping the patient, the application of two layers of drapes instead of one may allow heat loss to be reduced (Radford et al 2004). The drapes should be kept as dry as possible, as heat loss through convection will occur (McNeil 1998).
When performing a laparotomy and an abdominal lavage needs to be performed, the perioperative practitioner must make sure warm fluids are used to reduce the risk of the patient's core temperature decreasing. Similarly when acting as a perioperative practitioner in any surgical case requiring irrigation fluids, for example transurethral resection of tumour or intravenous infusion, again warm fluids must be used. It is the responsibility of the perioperative practitioner to ensure fluids are not removed from a warming cabinet until they are assembled and connected to the patient (McNeil 1998). If required, fluid warmers can also be initiated as the amount of heat loss is related to the rate and volume of infused fluids (Arndt 1999). When a patient is undergoing bowel surgery and some of the intestines need to be retracted out of the cavity, an intestinal bag can be used to prevent moisture and heat loss (Rothrock 2003).
Upon the release of a tourniquet there is a drop in body temperature as heat from the core is redistributed. This should be remembered by the perioperative practitioner when monitoring body temperature (Sessler 2000, cited in Radford et al 2004).
Once the operation has finished the blankets or bed linen should be placed over the patient. After being transferred onto the bed or trolley the draw sheet and any wet linen should be removed prior to transfer of the patient to recovery (McNeil 1998).
Complications of hypothermia also have a potential effect on the recovery of the patient postoperatively. These include:
* low levels of consciousness
* delayed drug reaction due to liver hypoxia
* a drop in urine output
* cardiac arrhythmia
* confusion and shivering
* exacerbating postoperative pain
* increasing demand for oxygen
* development of pressure sores
* increased susceptibility to wound infection
* venous status leading to development of deep vein thrombosis
* reduced coagulability of platelets increasing bleeding (Connor & Wren 2000).
In addition to the above mentioned variants, trauma patients can have further implications including impaired venous access and fatal fat embolism (Radford et al 2004, McNeil 1997).
I can now acknowledge that an understanding of the physiological ramifications of hypothermia is vital for proficient patient care because of the many potentially serious consequences that can result from inadvertent hypothermia. Because of these consequences, the maintenance of normothermia during the perioperative and postoperative period is important not only for patient comfort, but for the prevention of complications and beneficial to patient discharge time from hospital.
The knowledge acquired in learning to manage and prevent inadvertent hypothermia has influenced my awareness that by adopting various methods inadvertent hypothermia can be avoided. This has inspired me to deploy the knowledge gained within my department--as all perioperative staff should be aware of the hazards and how they can be prevented--to explore current guidelines and protocols, and to promote staff education on this prevalent condition.
Table 1 Contributing risk factors (ASPAN 2001) are as follows: * Extremes of age * Female sex * Ambient room temperature * Cachexia * Pre-existing conditions * Significant fluid shifts * Use of cold irrigation * Use of general anaesthesia * Use of regional anaesthesia Other causative factors McNeil (1997, 1998) are as follows: * Prolonged fasting * Premedication * Insufficient clothing * Exposure during positioning * Cold prep solutions * Trauma
Arndt K 1999 Inadvertent hypothermia in the ORAORN Journal 70 (2) 204-206
Connor E, Wren K 2000 Detrimental effects of hypothermia: a systems analysis Journal of PeriAnesthesia Nursing 15 (3) 151-155
American Society of PeriAnesthetic Nurses (ASPAN) 2001 Patient temperature: an introduction to the clinical guideline for the prevention of unplanned perioperative hypothermia Journal of PeriAnesthesia Nursing 16 (5) 303-304
Keane C 2001 Physiological responses and management of hypothermia Emergency Nurse 8 (8) 26-31
Kumar B 1998 Working in the Operating Department Edinburgh, Churchill Livingstone
Marieb E 2004 Human Anatomy and Physiology (6th edn) Boston, Benjamin Cummings
McNeil B 1997 Inadvertent hypothermia in the operating theatre Professional Nurse 12 (6) 418-421
McNeil B 1998 Addressing the problems of inadvertent hypothermia in surgical patients, Part 2: Self learning package British Journal of Theatre Nursing 8 (5) 25-33
Radford M, County B 2004 Advancing Perioperative Practice Cheltenham, Nelson Thorne
Rothrock, J 2002 Alexander's Care of the Patient in Surgery St Louis, Mosby
Surkitt-Parr 1992 Hypothermia in surgical patients British Journal of Nursing 1 (11) 539-540
Waugh A, Grant A 2001 Ross and Wilson Anatomy and Physiology in Health and Illness Edinburgh, Churchill Livingstone
Carol Bellamy Dip HE (Operating Department Practice)
Operating Department Practitioner, Princess Alexandra Hospital NHS Trust
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|Title Annotation:||CLINICAL FEATURE|
|Publication:||Journal of Perioperative Practice|
|Date:||Jan 1, 2007|
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