RCA ICU Management

TTM: The Back Story

Following publication of 2 randomised controlled trials in 2002, by the Bernard et al and the HACA group the use of therapeutic hypothermia protocols targeting T32-34C became widespread.

These studies had flaws but concluded that therapeutic hypothermia, cooling to 33 degrees post VF/VT arrest resulted in better neurological outcomes

The TTM study was published in 2013. This was a larger and more methodologically sound study comparing targeted temperature management of 33 verses 36 degrees post OOHCA. It showed no difference between the two temperature targets in mortality or neurological outcomes.

TTM2 was published in 2021:

This showed:

> Avoiding fever is the key

> TTM is still important in post resuscitation care of the unconscious cardiac arrest patient

> No benefit to hypothermia as there was a similar outcome whether 33ºC or <37.8ºC was selected as the target temperature.

> Hypothermia group were more likely to:

• Develop arrhythmias causing haemodynamic instability
• Spent more time mechanically ventilated (3.8 days vs 2.9 days)
• Need neuromuscular blockers (66% vs 45%)

Note: this only included OOHCA from presumed cardiac cause; does not necessarily apply to <18 yo’s, pregnant women, non-cardiac causes of arrest, or in-hospital CA.

TTM2

So what Temp to go for?

Primo non nocere

A targeted temperature of <37.8 for 72 hours after ROSC

Key aspects of TTM

“High quality” TTM is essential

> A targeted temperature of <37.8^oC should be the aim and be maintained for 72 hours after ROSC.

> A trigger temperature of 37.5^oC can be used to commence active cooling using a surface cooling device.

> If a patient has an initial temperature < 33°C, cover with a warm blanket and allow passive warming, until the core temperature reaches 35^oC.

> If the patient has a temperature of 35-37.5^oC they do not have to have any active temperature intervention.

> Sedation should be continued for 40 hours to ensure ease of temperature control.

> Short acting agents such as propofol, remifentanil or fentanyl in the lowest doses necessary to tolerate temperature management and prevent shivering should be used.

> Extubation should be attempted at the earliest possible time during this phase, if appropriate, according to standard practice.

Temperature Management

> All patients to have a bladder temperature probe

> All patients to be prescribed regular paracetamol (enteral or intravenous)

> Once committed to this pathway, patients should be sedated for at least 40 hours

> If temperature reaches 37.5^oC this is the trigger to commence temperature management

Expose patient

Use tepid sponges, NG iced water (200ml of H₂O, medical order on ERIC)

> If temperature reaches 37.8 ^oC this is the trigger to commence surface cooling

Apply cooling blanket

> Use bladder temperature IDC/probe to titrate cooling

SHIVERING

Shivering makes achievement of the temperature target harder. It needs treating.

Treat preemptively and aggressively to avoid having to use heavier sedation and paralysis that delays waking and prognostication

Tier 1: Before it starts

• Paracetamol 1g q6h regular not PRN
• Magnesium to achieve > 0.8 mmol/L
• Consider buspirone 30 mg q8h nia NGT if available

Tier 2: If shivering starts

• Wrap hands and feet with warm towels
• Dexmedetomidine infusion or clonidine (never both)
• Propofol infusion if Dexmed contraindicated
• Then remifentanil infusion
• Then ketamine infusion
• Magnesium for target 1.2-1.6 mmol/L

Tier 3: Only if everything else fails as interferes with prognostication

• Fentanyl boluses (avoid infusion if possible)
• Paralysis as last resort, rarely needed

NORMOXIA

Aim Sats 94-96% / PaO2 75-100 mmHg

> Both hypoxemia and hyperoxia seem to be harmful.

> Target oxygen saturation of 94-98% or PaO2 of 75-100 mmHg REF

> Most common mistake is leaving the ventilation set to 100% FiO2 for hours.

> FiO2 is usually 100% immediately after intubation, but this should be down-titrated as rapidly as possible.

> You don’t need a blood gas to titrate the FiO2, use pulse ox sats

REF

AVOID HYPOCAPNOEA

PaCO2 35-45 mmHg

> Hypocapnia may cause cerebral vasoconstriction and ischaemia

> Trials are investigating the benefits of permissive hypercapnia

> For now, aim for normocapnoea

Essentials

> Arterial line

> CVC usually required

> Transthoracic echocardiogram

> Aim MAP > 65 mmHg

> Aim UO > 0.5 ml/kg/h

> Aim normal or decreasing lactate

> Achieve euvolaemia with crystalloid fluid

> Vasopressor of choice is noradrenaline

> Maintain normal potassium levels to avoid arrhythmias

Optionals

> If haemodynamically unstable, use cardiac output monitoring

> If inotropy needed consider dobutamine (especially if bradycardic) or milrinone

> Steroids not recommended as routine REF

Long acting sedatives and analgesic agents affect the neurological exam and prevent accurate prognostication

> Avoid midazolam and fentanyl infusions

> Paralytic agent infusions cause weakness that may also affect the exam; avoid unless absolutely necessary

AN APPROACH

> Tier 1 anti-shivering measures

> If sedation required use either propofol or dexmedetomidine

> Remifentanil is the most appropriate opiate infusion if one is required REF

> Use a proton pump inhibitor for ulcer prophylaxis

Start enteral feeding

REF

Aim euglycaemia using an infusion of insulin if required

Avoid hypoglycaemia (<4.0 mmol/L )

Target BGL 6-10 mol/L is pragmatic and widely used

Some advocate target BGL 7.8 – 10 mmol/L
REF

> Prophylactic anti-seizure medications are not recommended

> If there appears to be generalised seizure activity terminate the seizure with propofol (if intubated) and load with levetiracetam (or valproate)

Get an EEG ASAP if seizures suspected

An EEG may differentiate status myoclonus from status epilepticus.

In comatose patients post cardiac arrest there is a high incidence of non-convulsive status epilepticus (12%)

Whether treatment of NCSE improves clinical outcomes is uncertain

If continuous EEG is available, it is often used in this situation

Default is enoxaparin 40 mg daily

Consider screening lower limb doppler USS if immobile for a week