Cardiac/Telemetry • ADVANCE EXTRA!
Cardiac arrest is a deadly situation. Hypothermia can also be life-threatening. Yet, when cardiac arrest and hypothermia are combined, something unexpected occurs: positive outcomes.
"Over 300,000 people experience an out-of-hospital cardiac arrest each year. Only 24 percent of those people survive to the hospital and only 8 percent survive to discharge," said Cathy Palleschi, BSN, RN, nursing director for the cardiac ICU of Maine Medical Center in Portland.
In 2003, the Advanced Life Support Task Force of the of the International Liaison Committee on Resuscitation recommended the use of inducing mild hypothermia in comatose survivors of out-of-hospital cardiac arrest caused by ventricular fibrillation (Circulation, American Heart Association). In spite of advance life support, many patients do not survive.
Although the return of spontaneous circulation is a step in the right direction, many potential complications abound for patients after cardiac arrest.
"Post-cardiac arrest syndrome is the result of a period of whole body ischemia. Once circulation is finally restored, the transition from no flow of blood to reperfusion can be very problematic," said Karen McQuillan, MS, RN, CNS-BC, CCRN, CNRN, FAAN, clinical nurse specialist at the University of Maryland Medical Center in Baltimore.
Both Maine Medical Center and University of Maryland Medical Center utilize therapeutic hypothermia to minimize post-cardiac arrest syndrome. This evidence-based protocol offers substantial benefits to patients.
"There were two landmark studies about therapeutic hypothermia that were published in 2002. Both studies demonstrated that patients who had return of spontaneous circulation after ventricular defibrillation cardiac arrest experienced better outcomes if therapeutic cooling had been utilized," McQuillan said.
Although research studies have shown it to be a successful strategy to mitigate neurological injury following a cardiac arrest, not every patient is a candidate. Inclusion criteria for this treatment include intubated comatose patients with treatment within 6 hours post cardiac arrest who are able to maintain their systolic BP > 90 mm Hg with or without pressor support. On the other hand, exclusion criteria include patients who awaken spontaneously, have serious or active bleeding, pre-existing sepsis, or hypokalemia. When hypokalemia is present (K+< 4.0), potassium is aggressively replaced before therapeutic hypothermia is initiated.
A Helpful Case of Brain Freeze
Following a cardiac arrest, two major organs are in jeopardy - the heart and the brain.
"Our objective is to simultaneously protect the heart and the brain; you do not want to protect one at the expense of the other," said Christine Lord, BSN, RN, unit-based educator at Maine Medical Center.
Bringing the heart and brain back to full function is a delicate process that relies heavily on many other systemic responses, as well as the patient's comorbidities.
"Brain injury is one of our primary concerns; the brain does not store oxygen and its cells are very intolerant of even brief periods of ischemia. We also have to contend with the potential for myocardial injury and other systemic responses to ischemia and reperfusion. And, of course, we cannot neglect the pathology that caused the arrest in the first place," McQuillan said.
Reperfusion can be traumatic for the ischemic brain and preventive measures must be utilized.
"Ischemia brings about many problems for the brain such as dysfunction of the mitochondria, excitatory neurotransmitter release, apoptosis, free radical production, cellular necrosis and inflammatory responses. By cooling the brain, we may be able to halt these pathological intracellular processes," McQuillan said.
Broadly speaking, a cooler brain is a less active brain. Therapeutic hypothermia utilizes this limited brain activity.
"When the body temperature is lowered, many things happen to protect the brain. Cerebral metabolic demands are decreased and there is a reduction in the inflammatory process," Lord said.
Rapid Cooling
Once a patient has been deemed a candidate for therapeutic hypothermia, timing is everything.
"When we determine that the patient will be cooled, we try to do it as quickly as possible. Initially, we employ multiple cooling methods and then back off as the patient approaches the target temperature of 32-34° C. We utilize 2L of cold saline intravenously along with an external cooling system that allows us to set a target temperature," McQuillan said.
Patients are typically brought to a temperature between 32°C and 34°C within 1-3 hours; in order for this rapid cooling to happen, multiple nurses are required.
"Our therapeutic hypothermia protocol encompasses stages: the initial 24 hours for induction and maintenance of target temperature of 33° C, followed by a 12-hour rewarming phase and then 36 hours of normothermia with a target temperature of 36.5° C, " Lord said.
Rewarming & Assessing
The patient is closely monitored. Once the target temperature has been maintained for the prescribed amount of time, gradual rewarming must begin.
"After the patient has been cooled for 24 hours, we gradually rewarm at the rate of a half degree per hour. It is well accepted in the data that a slow and gradual rewarming is crucial for optimal effectiveness of the therapeutic hypothermia," McQuillan said.
After 72 hours, the team evaluates the neurological and cardiac status of the patient. Sedation is lightened and a full neurological exam is conducted along with an assessment of the patient's EEGs.
"The hope is that the patient's neurological injury will be minimal and that the patient will be able to respond and follow simple commands," Lord said.
Although not every patient who undergoes mild therapeutic hypothermia will survive to leave the hospital, successful outcomes can and do occur.
"It is incredibly rewarding when someone who was unresponsive after cardiac arrest is finally discharged from the hospital with good neurological function," McQuillan said.
Caring for Everyone in the Room
When the family chooses to exhaust all efforts, critical care nursing staff must assist the family emotionally as they care for the patient physically. As the family undergoes an emotional journey, focus should be not only on the patient but also on the emotional needs of the family.
"The family is invited to document . what name the patient prefers to be called, the patient's favorite music and hobbies; and the family can [share] their favorite photos," Palleschi said.
Open communication is encouraged between the medical staff and the patient's family.
"We enlist the help of social services and chaplains along with continuity of nursing care to provide support to the family. The team meets daily with the family at prescheduled time frames to review the patient's current status and answer any questions they may have," Lord said.
Post-cardiac arrest care is taxing on patient and family alike. Nurses are equally affected by this intensive course of care.
"Caring for a patient who is undergoing therapeutic hypothermia is emotionally rigorous for the nursing staff. They are not always sure that the patient will wake up and have a full recovery. In order to address the emotional needs of our nursing staff, we have periodic debriefings with our chaplain and ethicist." Palleschi said.
Rewards come when healthy patients return to the hospital, grateful for the care rendered.
"We had an opportunity to host a survivor luncheon awhile back; patients who [had cardiac arrest] and later returned home were invited back to the hospital with a loved one," Lord said.
The return of a healthy patient confirms the need for evidence-based care such as that provided through therapeutic hypothermia.
"Protocols or guidelines for use of therapeutic hypothermia should be utilized in hospitals. Look into the literature and it will become evident that having a program is crucial. It really is multidisciplinary effort that requires everyone to be on board: labs, equipment exchange, pharmacy, physicians and nurses," McQuillan said.
A. Trevor Sutton is a frequent contributor to ADVANCE.