Therapeutic hypothermia following cardiac arrest - Consultation Document
Interventional procedure consultation document
Therapeutic hypothermia following cardiac arrest
Reducing the risk of brain injury after a cardiac arrest by lowering the body’s temperature
People who have a cardiac arrest (when the heart suddenly stops beating) can sometimes develop neurological problems because of the lack of oxygen to the brain.
In this procedure, after resuscitation, a cooling device is used to reduce the person’s core temperature to 32–34°C to reduce the risk of brain injury and therefore neurological problems.
The National Institute for Health and Clinical Excellence (NICE) is examining therapeutic hypothermia following cardiac arrest and will publish guidance on its safety and efficacy to the NHS in England, Wales, Scotland and Northern Ireland. NICE’s Interventional Procedures Advisory Committee has considered the available evidence and the views of Specialist Advisers, who are consultants with knowledge of the procedure. The Advisory Committee has made provisional recommendations about therapeutic hypothermia following cardiac arrest.
This document summarises the procedure and sets out the provisional recommendations made by the Advisory Committee. It has been prepared for public consultation. The Advisory Committee particularly welcomes:
- comments on the provisional recommendations
- the identification of factual inaccuracies
- additional relevant evidence, with bibliographic references where possible.
Note that this document is not NICE’s formal guidance on this procedure. The recommendations are provisional and may change after consultation.
The process that NICE will follow after the consultation period ends is as follows.
- The Advisory Committee will meet again to consider the original evidence and its provisional recommendations in the light of the comments received during consultation.
- The Advisory Committee will then prepare draft guidance which will be the basis for NICE’s guidance on the use of the procedure in the NHS in England, Wales, Scotland and Northern Ireland.
For further details, see the Interventional Procedures Programme manual, which is available from the NICE website (www.nice.org.uk/ipprogrammemanual).
NICE is committed to promoting through its guidance race and disability equality and equality between men and women, and to eliminating all forms of discrimination. One of the ways we do this is by trying to involve as wide a range of people and interest groups as possible in the development of our guidance on interventional procedures. In particular, we aim to encourage people and organisations from groups in the population who might not normally comment on our guidance to do so. We also ask consultees to highlight any ways in which draft guidance fails to promote equality or tackle discrimination and give suggestions for how it might be improved. NICE reserves the right to summarise and edit comments received during consultations, or not to publish them at all, where in the reasonable opinion of NICE, the comments are voluminous, publication would be unlawful or publication would otherwise be inappropriate.
Closing date for comments: 23 November 2010
Target date for publication of guidance: February 2011
1 Provisional recommendations
1.1 Current evidence on the safety and efficacy of therapeutic hypothermia following cardiac arrest is adequate to support the use of this procedure provided that normal arrangements are in place for clinical governance, audit and consent (where applicable).
2 The procedure
2.1 Indications and current treatments
2.1.1 Cardiac arrest leads to loss of consciousness and death unless emergency resuscitation is given and the heart can be restarted. There are many possible causes of cardiac arrest, including coronary heart disease, electrocution, drowning and choking. The abnormal cardiac rhythms most commonly associated with cardiac arrest are asystole, pulseless electrical activity, ventricular fibrillation (VF) or pulseless ventricular tachycardia (VT).
2.1.2 Brain injury following cardiac arrest may be prevented by early cardiopulmonary resuscitation, including defibrillation to treat VF and pulseless VT rhythms. Drugs such as epinephrine or atropine are also commonly required.
2.2 Outline of the procedure
2.2.1 After cardiac arrest, comatose patients who have a return of spontaneous circulation (ROSC) can be cooled to a core temperature of 32–34°C with the aim of reducing brain injury and improving neurological outcome. The exact mechanism by which cooling confers cerebral protection is unknown.
2.2.2 As soon as possible after the cardiac arrest, mild hypothermia is induced by using surface techniques (for example heat exchange cooling pads, cooling blankets, ice packs), internal techniques (for example an endovascular cooling device) or a combination of cooling methods. Core body temperature is maintained at 32–34°C for 12–24 hours from the start of cooling and is monitored using a bladder temperature probe. Passive re-warming is usually carried out over an 8-hour period. In addition to cooling, patients generally receive standard critical care measures, together with intravenous sedation and muscle relaxants (to prevent shivering).
Sections 2.3 and 2.4 describe efficacy and safety outcomes from the published literature that the Committee considered as part of the evidence about this procedure. For more detailed information on the evidence, see the overview, available at www.nice.org.uk/guidance/IP/863/overview
2.3.1 A systematic review of 481 patients reported that a significantly higher proportion of patients who had therapeutic hypothermia survived to hospital discharge compared with patients in the standard care group (risk ratio [RR]: 1.35, 95% confidence interval [CI]:1.10 to 1.65, 3 studies).
2.3.2 The systematic review of 481 patients reported that a significantly higher proportion of patients in the hypothermia group had a good neurological outcome at hospital discharge compared with patients in the standard care group (RR: 1.55, 95% CI: 1.24 to 1.94, 5 studies).
2.3.3 A randomised controlled trial (RCT) of 275 patients (137 hypothermia vs 138 normothermia) reported a significantly higher proportion of patients in the hypothermia group with a favourable neurological outcome at 6 months compared with patients in the normothermia group, after adjusting for baseline variables (RR: 1.47 (95% CI: 1.09 to 1.82).
2.3.4 An RCT of 54 patients (36 hypothermia vs 18 normothermia) reported that a significantly higher proportion of patients in the hypothermia group had a good neurological outcome at 1 month compared with patients in the normothermia group (50% vs 11%, p < 0.05).
2.3.5 The Specialist Advisers listed key efficacy outcomes as survival, reduced long-term neurological disability, independent living, quality of life (SF-36, Health Utility Index 3), and reductions in length of critical care and hospital stay.
2.4.1 A case series of 986 patients reported sepsis and pneumonia rates of 4% (35/986) and 41% (407/986) respectively (6–12-month follow-up). The systematic review of 481 patients reported higher rates of pneumonia and sepsis in the hypothermia group compared with patients in the standard care group but the differences were not significant (pneumonia RR: 1.27, 95% CI: 0.90 to 1.78, 1 study; sepsis: RR: 1.93, 95% CI: 0.89 to 1.78, 1 study).
2.4.2 The systematic review of 481 patients reported numerically higher rates of hypophosphataemia in the hypothermia group compared to standard care but the differences were not significant (RR: 1.12, 95% CI: 0.65 to 2.25, 1 study).
2.4.3 An RCT of 61 patients (20 haemofiltration only vs 22 hypothermia plus haemofiltration vs 19 controls) reported similar 6-month hypokalaemia rates of 25% (5/20) in the haemofiltration only group and 23% (5/22) in the hypothermia plus haemofiltration group. The same study reported similar 6-month hypophosphataemia rates of 45% (9/20) in the haemofiltration only group and 55% (12/22) in the hypothermia plus haemofiltration group.
2.4.4 The systematic review of 481 patients reported a numerically higher rate of bleeding requiring platelet transfusion in the hypothermia group compared to standard care but the difference was not significant (RR: 5.11, 95% CI: 0.25 to 5.47, 1 study).
2.4.5 An RCT of 64 patients (34 hypothermia using gel pads with feedback control vs 30 hypothermia using blankets and ice) reported heparin-induced thrombocytopenia within 90 days in 1 patient in the gel pads with feedback control group and no patients in the blankets and ice group. The same study reported 2 patients with a gastrointestinal bleed within 90 days in the blankets and ice group and no patients in the gel pads group.
2.4.6 A case series of 986 patients reported bleeding requiring transfusion in 5% (44/986) of patients.
2.4.7 The RCT of 64 patients reported similar 90-day seizure and/or status epilepticus rates in both groups (19% [6/32] vs 17% [5/29]).
2.4.8 The systematic review of 481 patients reported a higher rate of lethal or long lasting arrhythmias in the hypothermia group compared to standard care but the differences were not significant (RR: 1.21, 95% CI: 0.88 to 1.67, 1 study).
2.4.9 The Specialist Advisers listed anecdotal adverse events as coagulation and immune modulation due to overcooling, thermal injury to skin from cooling devices, arrhythmias, secondary infections, shivering, electrolyte imbalance, pancreatitis, peripheral vasoconstriction and thrombosis related to endovascular devices. They considered theoretical adverse events to include ileus, hepatic failure and renal failure.
2.5 Other comments
2.5.1 The Committee noted that the majority of evidence was on patients with ventricular fibrillation arrest and continuing loss of consciousness. Evidence on other patients is limited.
3 Further information
3.1 For related NICE guidance see www.nice.org.uk
Chairman, Interventional Procedures Advisory Committee
Personal data will not be posted on the NICE website. In accordance with the Data Protection Act names will be anonymised, other than in circumstances where explicit permission has been given.
It is the responsibility of consultees to accurately cite academic work in order that they can be validated.
This page was last updated: 15 February 2011