DaiWai M. Olson, PhD, RN, CCRN*
Clinical Research Associate
Department of Medicine/Neurology
Duke University Medical Center
Durham, North Carolina, USA

Research has led to the current American Heart Association (AHA) Advanced Life Support recommendations on use of mild hypothermia (32 to 34°C) following cardiac arrest (HACA).1 Translating the scientific evidence on HACA into clinical practice is a challenge for critical care teams. The clinical application of hypothermia requires an integrated team approach, system support and patient interventions.

Paper to Practice: Team and System Issues
The critical care team needs clinician champions to lead the practice change. Ideally, the team includes intensivists, cardiologists, neurologists, emergency department (ED) physicians, advance practice nurses (APN), and nurses from the ED and intensive care unit (ICU). The team is vital to the process because they must champion the cause with their peers. It is equally imperative that ancillary and supply personnel are included, as the process requires support from multiple departments to obtain the proper equipment required for induced hypothermia. When the team has been organized, the APN collaborates with physician leaders to organize a series of meetings that explore the scientific literature, synthesize the evidence, identify resources, construct protocols, plan staff education, and implement hypothermia protocols. The team considers the impact on the hospital system and the resources needed to deploy HACA. A consensus on the inclusion/exclusion criteria is imperative, as are targeting the practice areas where HACA patients will be identified and determining when hypothermia will be initiated. Because hypothermia must begin as soon as possible to minimize neuronal injury, most HACA cases enter the system in the ED. The ED physician and nurse members of the core planning team are integral to ensuring that HACA is considered for patients who survive out-of-hospital arrest. Because the HACA protocol is detailed and requires a strict plan for induction, identifying the ICU where these patients will receive care ensures continuity. Encouraging the intensivist and staff within the ICU and ED to work as a resuscitation team facilitates movement of the patient from one department to another. The protocol includes hemodynamic and laboratory parameters, technology to monitor central temperature, and induction methods to cool the patient. These considerations require system support.

Obtaining the correct equipment to manage hypothermia is paramount. Including ancillary/supply personnel in the team brings together key personnel to facilitate the acquisition of the needed equipment. The core team decides what type of cooling method is ideal for the particular facility. The team may elect to use surface cooling with a wrap device if a physician is not available to provide access via central line. Intravascular devices are chosen if physician support is immediately available to access the central circulation. The HACA protocol outlines the needed pre-hypothermia baseline hemodynamic and laboratory values. Engaging the laboratory in the team provides insight into the frequent monitoring of key electrolytes. The ability of the intensivist to interact within the ED environment can facilitate implementation of the protocol, give assistance with securing central lines for hemodynamic monitoring, and provide access for medications/fluids in support of the patient’s blood pressure. Monitoring the patient’s central temperature is important in providing constant feedback for cooling; use of a Foley temperature probe is recommended.  The ICU nurse assists the ED team in obtaining baseline assessments, including neurologic, hemodynamic and laboratory data. Once the hospital system has been organized to implement HACA and the team is engaged in the process, priorities in patient management are detailed.

The bedside nurse is tasked with inducing, maintaining and monitoring the effects of hypothermia, anticipating the physiologic changes, and bringing the patient out of the cooled state. The nursing team must be educated about the protocol and must provide the necessary staffing to monitor the patient closely. Although these priorities center on the needs of the patient, nursing care includes attending to the needs of the patient-family dyad. Family members are kept informed of the HACA treatment plan and patient progress. It is reasonable to expect that they will be anxious as they learn a loved one has been resuscitated from cardiac death. Given that family members respond to stress differently, care should be tailored to the individual. More research is needed to determine the exact role of the family during induced hypothermia, but numerous studies have found that families’ primary need during this time is information.2,3

Preprinted brochures on HACA are helpful, but direct verbal communication from physicians, nurses and clergy is recommended throughout all phases of HACA. Some family members may opt to be involved with the patient’s care, assisting with turning, skin care or even bathing; others may elect to sit quietly in waiting rooms.

Initiating Induced Hypothermia
The first portion of the protocol focuses on inducing hypothermia. The primary goal during the induction phase is rapid reduction of the body’s core temperature. Guidelines from the AHA and the International Liaison Committee on Resuscitation support a temperature goal of 32 to 34˚C maintained for 12 to 24 hours.1 Nurses must be familiar with the use of cooling methods. During the initiation phase, the concurrent use of cold intravenous solutions has been recommended as a supplement to inducing hypothermia with surface wraps or intravascular cooling.4 Knowing that rapid cooling is an essential component of induced hypothermia, the nursing staff should initiate continuous temperature monitoring as early as possible, and it is recommended that at least two sites be used to reduce the risk of error. Hemodynamic and respiratory monitoring is essential during all phases of treatment. Central intravenous access is established early for medication access and monitoring of central pressures. Intra-arterial catheter placement provides for continuous blood pressure monitoring and facilitates blood sampling. Baseline assessment tests (e.g., laboratory values, electrocardiogram) are facilitated by physiciandriven, nurse-initiated protocols. Hypothermia produces an intracellular shift in electrolytes requiring baseline and hourly laboratory monitoring during the induction period, and so warrants vigilance by bedside clinicians. To prevent overshooting normal laboratory levels, which can occur during the rewarming phase, baseline values and cautious replacement of electrolytes are essential. The risk of coagulopathy associated with deep hypothermia requires that nurses monitor coagulation and assess the patient for signs of bleeding at invasive device and line access sites.

The nursing staff should be ready to initiate paralytic, analgesic and sedation algorithms. The greatest risk of shivering occurs as the drop in core temperature (36 to 35˚C) triggers a heat-production response.5 Sedation and neuromuscular blockade (NMB) medications may be beneficial during the induction phase to help control shivering. The effect of NMB is closely monitored with a peripheral nerve stimulator. The team may elect to reduce or eliminate NMB once the patient has reached goal temperatures because shivering is reduced or eliminated. Sedatives should be initiated before NMB administration and adjusted to a set endpoint.6,7 Nurses must be cognizant that NMBs suppress motor responses, so subjective sedation tools that require a physical response may not be reliable. Additionally, it is difficult to assess the patient’s need for analgesia. Whether the choice is for intermittent or continuous analgesic administration, nurses and physicians should work cooperatively to develop a consistent approach to providing pain control and holistic care.

 Nursing Monitoring During the Maintenance Phase
After reduction of the body temperature to 32 to 33˚C, care moves into the maintenance phase of HACA. Body temperature is maintained as close to the target as possible. Standard critical care monitoring (e.g., laboratory values, fluid volume status and vital signs) continues during this phase. Monitoring serum glucose is important during all phases of hypothermia but especially in the maintenance phase. Using an intravenous insulin protocol to titrate the serum glucose between 110 and 140 mg/ dL assists with preventing complications associated with hyper- and hypoglycemia. Insulin resistance occursduring hypothermia, and serum glucose levels vary with temperatures. Maintaining hypothermia requires nursing vigilance as the patient is dependent on the nurse’s interpretation of the array of physiologic and observational data. Careful attention should be given to skin care, mouth care, mobility needs (turning and range of motion), normal body functions, balancing sedation and analgesic needs, and close titration of hemodynamic agents in collaboration with the medical team.

Controlled Rewarming
Rewarming must be purposive. Protocols include directing the nurse to continue controlling the temperature throughout this phase to avoid accidental overshoot. While the goal of cooling is to alter the temperature as quickly as possible, the rewarming phase typically lasts 12 to 24 hours. Fluids and electrolytes that shifted intracellularly during hypothermia return to their normal compartments. Nurses must be cautious when instituting electrolyte replacement protocols, as electrolyte “effluxes” with increases in body temperature. Blood pressure monitoring every 30 to 60 minutes during the rewarming phase is required due to vasodilatation and fluid shifts. Maintaining euvolemia with fluid replacement and titrating vasopressors are helpful strategies to optimize blood pressure. Maintenance of normothermia for several days following the rewarming phase is important to avoid the harmful effects of cellular derangements associated with rebound hyperthermia.

Summary
Hypothermia requires an integrated approach to patient management. The ED and ICU teams work collaboratively to facilitate rapid implementation of hypothermia. System support is an essential component of the process for securing necessary equipment, laboratory and pharmaceutical services. Patient management is facilitated by the use of an evidence-based protocol to guide treatment. The ability to integrate these elements successfully provides the foundation to optimize patient outcomes when using hypothermia following cardiac arrest.

 References 

1. 2005 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2005;112:IV1-203.

2. Maxwell KE, Stuenkel D, Saylor C. Needs of family members of critically ill patients: a comparison of nurse and family perceptions. Heart Lung. 2007;36:367-76.

3. Verhaeghe S, et al. The needs and experiences of family members of adult patients in an intensive care unit: a review of the literature. J Clin Nurs. 2005;14:501-9.

4. Bernard S, et al. Induced hypothermia using large volume, ice-cold intravenous fluid in comatose survivors of out-of-hospital cardiac arrest: a preliminary report. Resuscitation. 2003;56:9-13.

5. Mahmood MA, Zweifler RM. Progress in shivering control. J Neurol Sci. 2007;261:47-54.

6. Jacobi J, et al. Clinical practice guidelines for the sustained use of sedatives and analgesics in the critically ill adult. Crit Care Med. 2002;30:119-41.

7. Arbour RB. Continuous nervous system monitoring, EEG, the bispectral index, and neuromuscular transmission. AACN Clin Issues. 2003;14:185-207.

Disclosures

**Author has received from Medivance an educational grant that included honorarium and has received honorarium in relation to a sponsored CE event.

*Author has no disclosures to report