Clinical Guidelines (Nursing)

Therapeutic hypothermia in the neonate

  • Note: This guideline is currently under review. 

    Introduction

    Neonatal asphyxia is a major health issue globally. In developed countries asphyxia affects 3-5 per 1000 live births. Subsequent development of moderate to severe hypoxic-ischaemic encephalopathy (HIE) occurs in 0.5- 1 per 1000 live births., with up to 60% of these babies dying during the neonatal period and 25% of survivors having major long term neurodevelopmental problems.

    Many experimental animal models and systematic reviews of randomised controlled trials have shown that both whole-body hypothermia and selective head cooling has a neuroprotective effect. It modifies the cells programmed for apoptosis leading to their survival.
    Hypothermia may also protect neurons by reducing cerebral metabolic rate, attenuating the release of excitatory amino acids (glutamate, dopamine) improve the ischaemic impaired uptake of glutamate and lowering production of toxic nitric oxide and free radicals

    Therapeutic hypothermia aims to lower the temperature of the vulnerable deep brain structures to 33-34°C.

     

    Definition of terms

    Hypoxic-ischaemic Encephalopathy: Lack of sufficient oxygen to the brain and a diminished amount of blood perfusing the brain. This results in suppression of electrical activity and cortical depression.

    Primary Neuronal Death: immediate death if the insult is severe. This is related to cellular hypoxia leading to primary energy failure and cellular depolorisation.

    Secondary Neuronal Death: after a latent period (6-100 hrs) neuronal death may be initiated by a cascade of pathologic processes and is associated with marked encephalopathy. This involves cytotoxic oedema, mitochondrial failure, accumulation of excitotoxins, active cell death, nitric oxide synthesis and cytotoxic actions of activated microglia. Seizure activity is increased during this phase

    Encephalopathy: Brain disease, damage or malfunction. In general encephalopathy is manifested by an altered mental state that may be accompanied by physical manifestations e.g abnormal limb movements.

    Apoptosis: Programmed cell death. Cells die in response to a variety of stimuli and during apoptosis they do so in a controlled, regulated manner. Apoptosis is a process in which cells play an active role in their own death and is often referred to as cell suicide.

    Medi-Therm III hyper/hypothermia system: Provides a means for regulating patient temperature by supplying temperature controlled water via a blanket placed under the patient.

     

    Assessment

    Eligibility/criteria for therapeutic hypothermia

    1. ≥ 35 weeks gestational age
    2. < 6hrs post birth
    3.  Evidence of asphyxia as defined by the presence of at least two of the following four criteria:
      1.  Apgar <6 at 10 min or continued need for resuscitation with positive pressure ventilation +/- chest compressions at 10 min age
      2.  Any acute Perinatal event the may result in HIE (i.e. Abruption placenta, cord prolapse, severe foetal heart rate abnormality.).
      3.  Cord pH <7.0 or base deficit of 12 or more
      4.  If cord pH is not available, arterial pH <7.0 or BE >12 mmol/L within 60 mins of birth (if available).
    4. Clinically defined moderate or severe HIE (stage 2 or 3 based on modified Sanart Classification). The presence of moderate/severe HIE is defined as seizures OR presence of signs in at least three of the six categories below:
      Moderate encephalopathy Severe encephalopathy
    Level of consciousness Lethargic Stupor/coma
    Spontaneous activity Decreased activity No activity
    Posture Distal flexion, full extension Decerebrise
    Tone Hypotonia Flaccid
    Primitive reflexes Weak suck, incomplete Moro Absent suck, absent Moro

    Autonomic system

    Pupil

    Heart rate

    respirations

    Constricted
    Bradycardia
    Periodic breathing


    Dilated/non-reactive
    Variable heart rate
    apnoea

             5. Moderate to severely abnormal background activity on amplitude-integrated EEG (.i.e. discontinuous, burst suppression or low voltage +/- seizure activity

             6. At the neonatal consultant’s discretion to commence therapeutic cooling

    The aim of cooling is to achieve the target temperature within 1 hour (rectal temperature between 33.0°C – 34.0°C)

    The total period of cooling and rewarming is for 84 hrs, consists of 2 phases
    Active cooling- for 72 hours from the initiation of cooling
    Rewarming- 12 hours of active gradual rewarming time after completion of 72hrs of cooling. Increase temperature by 0.5ºC every 2 hours as documented on care plan/treatment orders.

     

    Management

    Collect equipment:

    • Medi-Therm III hyper/hypothermia system
    • Rectal temperature probe


    Set up and use of Medi-Therm III hyper/hypothermia system as per How to use Medi-Therm III hyper/hypothermia system.

    Nursing considerations


    Systemic effects

    • Neonates usually require ventilator support to maintain adequate oxygenation and ventilation. Hypothermia shifts the oxyhaemoglobin curve and can result in a decreased oxygen delivery, but the metabolic rate is also lowered which decrease oxygen consumption and carbon dioxide production. If the baby is not ventilated then the metabolic rate may be increased without an increase in oxygen delivery.
    • Peripheral perfusion is often poor- lines should be placed before commencing cooling
    • Connect to continuous cardiorespiratory monitoring
    • Monitor BP- may need filling and inotropes (correct hypovolaemia first)
    • Watch for arrhythmias- sinus bradycardia is the most common arrhythmia
    • CO2 measurement must be corrected for patient temperature

    Neurological considerations

    • Monitor for seizures – occurs in 43-56% of patients with HIE needing cooling
    • Check pupils, evaluate level of consciousness and for signs of raised intracranial pressure
    • aEEG monitoring for the duration of cooling
    • Will need formal EEG and MRI later (3-7 days after rewarming). Early MRI may be done to help with decision making in regards to palliation

    Sedation

    • Patients may require a low dose morphine infusion to help optimise comfort and efficacy of the cooling process. Inadequate sedation can result in increased metabolic rate which decreases the effectiveness of the cooling strategy

    Fluid and Electrolytes

    • At risk for multiple electrolyte imbalances- need frequent monitoring and correction based on laboratory levels (bloods normally taken on admission, prior to commencement of cooling then at 4, 8, 12, 24, and 72 hours) as documented on treatment orders.
    • Most are fluid restricted to avoid fluid overload and cerebral oedema
    • Minimise risk of cerebral oedema by keeping sodium levels at upper limits of normal
    • Magnesium kept at upper limits of normal as has neuroprotective effect

    Haematology/infection control

    • Coagulopathy may be induced by hypothermia because of decreased platelet function
    • Whilst clotting profile may be prolonged, this is not associated with an increased risk of bleeding.
    • Patients may need transfusions of FFP, platelets and cryoprecipitate
    • Hypothermia can cause immune dysfunctions so cooled infants are often covered prophylatically with IV antibiotics
    • Strict infection control
    • Daily review for evidence of infection

    Skin

    • Need frequent inspections of skin and repositioning
    • Monitor skin for colour, perfusion, skin breakdown and for signs of subcutaneous fat necrosis
    • Although rare, subcutaneous fat necrosis is characterised by induration erythemateous nodules and plaques over bony prominences such as back, arms, buttocks, thighs and chest. It is rare, thought to be because brown fat is more sensitive to hypoxia and made worse by cooling. It is self remitting, can lead to hypercalcaemia, hyperlipidaemia and thrombocytopaenia

     Therapeutic Hypothermia skin

    Family centred care

    Explain to family the reasoning for using hypothermia and the expected length of treatment. Explain to family that their baby will feel cold for the duration of the treatment and reassure them that their baby will be kept comfortable during the treatment. Encourage bonding by allowing parents to touch their baby, do nappy changes etc.

    Potential Side effects

    • Delayed intracardiac conduction with sinus Bradycardia
    • Prolonged QT interval
    • Ventricular arrhythmias
    • Reduced cardiac output
    • Hypotension
    • Reduction in surfactant production
    • Increase pulmonary vascular resistance
    • Increase oxygen consumption and oxygen requirement
    • Affects coagulation cascade and viscosity- coagulopathy that may be complicated by thrombus or haemorrhage
    • Anaemia
    • Thrombocytopaenia
    • Leukopaenia – increase risk of sepsis
    • Renal impairment
    • Metabolic and lactic acidosis
    • Hypokalaemia
    • Hypoglycaemia
    • Impaired liver function

    Notify doctor immediately if any of the above is observed, treat as per doctors orders.

    Companion documents

    How to use Medi-Therm III hyper/hypothermia system

    Links

    How to use Medi-Therm III hyper/hypothermia system

     

    Evidence table

    Click here to view the evidence table for this nursing guideline.

    Complete evidence table document available at http://www.wch.org.au/nursing/governance

    References


    1. Edwards A.D., Azzopardi D.V. (2006). Therapeutic hypothermia following Perinatal asphyxia. Arch DIS Child Fetal Neonatal ED, 91:F127-F131.
    2. Jacobs S.E., Berg M., Hunt R., Tarnow-Mordi W.O., Inder T.E., Davis P.G. (2013). Cooling for newborns with hypoxic ischemic encephalopathy. Cochrane Database SystRev, Jan 31, 1. CD003311.
    3. Nassef, S.K., Blennow, M., Jirwe, M. (2012). Experiences of Parents Whose Newborns Undergo Hypothermia Treatment Following Perinatal Asphyxia. JOGNN, 42 (1): 38-47
    4. Shah P.S., Ohlsson A., Perlman M. (2007). Hypothermia to treat neonatal hypoxic ischemia encephalopathy: Systematic Review. Archive Pediatric Adolescent Medicine, 161: 951-8
    5. Shankar an S., Laptop, A.R., Ehrenkranz R.A., Tyson J.E., McDonald S.A., Donovan E.F., Fanaroff A.A., Poole W.K., Wright L.L, Higgins R.D., Finer N.N.., Carlo W.A., Duara S., Oh W., Cotton C.M., Stevenson D.K., Stoll B.J., Lemons J.A., Guillet R., Jobe A.H. (2005). Whole-Body Hypothermia for Neonates with Hypoxic-Ischaemic Encephalopathy. N Eng J Med, Oct: 1574-1584

    Document control

    Complete document control document available at http://www.wch.org.au/nursing/governance

     

     Please remember to read the disclaimer.


    The development of this nursing guideline was coordinated by Trudy Holton, Clinical Nurse Educator, Butterfly Ward, and approved by the Nursing Clinical Effectiveness Committee. Updated September 2014.