Understanding the drugs used during a cardiac arrest

The first drug given in all cardiac arrests. Adrenaline concentrates all the blood around al the vital organs including the heart and the brain by peripheral vasoconstruction.

These are the organs that must continue to recieve blood to increase the chances of survivial following the cardiac arrest. 

Adrenaline strengthens the cardiac contractions and stimulates the cardiac muscle. Adrenaline can be given repeatedly until the patients conditions imporves (repeat every 3-5 minutes)

Adrenaline can be given through a centeral line, reaches the cardiac tissue

Cannula if the centeral line is not available 

If the patient is intubated adrenaline can be given via the endotracheal tube directly into the lungs.

It can be injected straight into the heart.

Once organised rhythm has been established the use of adrenaline must be reassessed as excessed amounts can percipitate ventricular fibrillation.

Used to treat cardiac arrythmia, mainly ventrilcular fibrillation and ventricular tachycardia.

The first treatment should only be given in three shocks are unsuccessful.

Amiodarone's main effect is to slow down the metabolism of the cardiac tissue, the drug blocks the action of hormones that speed up the heart rate.

There should be an interval between bolus doses of 15 minutes, this can be continued over 24 hours. 

Amiodrone is not compatible with sodium chloride and must be diluted with 5% of dextrose.

The route should be through a cannula in peripheral vein but localised irritation and discomfort is usual and can occur due to continuous infusion. 

A side effect of this drug is severe bradycardia. A reduced heart rate can be reversed by atropine.

Given to treat specific cardiac arrythmia mainly ventricular fibrillation and ventricular tachycardia (similar to Amiodarone).

Lidocaine can only be given in situations where Amiodarone is not availabe, 

It is reccomended the IV Lidocaine is given as a bolus of 2-4 minutes with a 5 minute interval between subsequent dose and there will also be a recommended a maxium dose of over an hour.

Bolus IVs have a short duration of action (15-20 minutes), so if the patients condition demands it a repeat bolus should be given within this time period and then a continuous infusion.

The side effects of this drug is bradycardia together with hypotension and continual cardiac monitoring.

Used to block the effect of the vagus nerve on the heart, this nerve normally slows the heart rate and during cardiac arrests it is a common cause of asytole.

Atropine also acts on the conduction system of the heart and accelerates the transmission of electrical impulses through cardiac tissue. In cardiac arrests it is used to revrse asystole and severe bradycardia. 

The resus council reccomends that atropine be given for pulseless electrical activity within a rate of >60bpm or in complete asyotole.

This drug can be administered intravenously and the dose depends on the heart rhythm. For bradycardia a dose of 0.5mg should be given and given every 5 minutes until a satisfactory heart rate  is achieved. In asystole a single dose of 3mg should be given and this should not be repeated unless the cardiac rhythm changes to bradycardia or pulseless electrical activity.

If IV access cannot be obtained then atropine can be given by an endotracheal tube at a dose 2-3 times as high as that given intravenously (1-1.5mg)

Calcium is essential for the contraction of muscualr tissue throughout the body and is important for the strength of contraction of cardiac tissue after mtabolic changes haved caused instability and arrythmias (Hollander-Rodriguez and Calvert, 2006).

Calcium can imporve weak myocardial contractions when adrenaline has failed.

Calcium can be used to protect against metabolic conditions that cause pulseless electrical activity, including raised blood pottasium levels, lowered blood calcium levels and overdose of magnesium or calcium blocking drugs.

Calcium chloride needs to be given intravenously and must not be injected into tissue due to the high risk tissue necrosis.

There are two main side effects, repeated injections can increase blood acidity and should be used with caution in patients who have lowered blood PH. Frequent monitoring of arterial blood PH is advised. IV CaCl can cuase hypotension due to peripheral vasodilation, bradycardia and cardiac arrythmias

Magnesium is an important electrolyte involved in the contraction of muscular tissue, including cardiac muscles. A reduction of this can cause cardiac arrythmias, leading to cardiac arrest.

Common causes of excessive magnesium loss are: 

• Long term use of pottasium losing diuretics
• Alcohol misuse
• Diarrhoea

Magnesium chloride must be given intravenously close monitoring of blood pressure, urine output and respiratory rate.

They are drugs used to treat specific medical conditions that may have caused the arrest ie. An acute asthmatic attack.

They are used to treat complications frequently associated with cardiac arrests such as fluid overload due to heart failure.