ALS assumes that basic life support (bag-mask administration of oxygen and chest compressions) are administered.
The main algorithm of ALS, which is invoked when actual cardiac arrest has been established, relies on the monitoring of the electrical activity of the heart on a cardiac monitor. Depending on the type of cardiac arrhythmia, defibrillation is applied, and medication is administered. Oxygen is administered and endotracheal intubation may be attempted to secure the airway. At regular intervals, the effect of the treatment on the heart rhythm, as well as the presence of cardiac output, is assessed.
Medication that may be administered may include adrenaline (epinephrine), amiodarone, atropine, bicarbonate, calcium, potassium and magnesium. Saline or colloids may be administered to increase the circulating volume.
While CPR is given (either manually, or through automated equipment such as AutoPulse), members of the team consider eight forms of potentially reversible causes for cardiac arrest, commonly abbreviated as “6Hs & 5Ts” according to 2005/2010 AHA Advanced Cardiac Life Support (ACLS). Note these reversible causes are usually taught and remembered as 4Hs and 4Ts – including hypoglycaemia and acidosis with hyper/hypokalaemia and ‘metabolic causes’ and omitting trauma from the T’s as this is redundant with hypovolaemia – this simplification aids recall during resuscitation.
- Hypoxia : low oxygen levels in the blood
- Hypovolemia : low amount of circulating blood, either absolutely due to blood loss or relatively due to vasodilation
- Hyperkalemia or hypokalemia : disturbances in the level of potassium in the blood, and related disturbances of calcium or magnesium levels.
- Hypothermia/Hyperthermia : body temperature not maintained
- Hydrogen ions (Acidosis)
- Hypoglycemia : Low blood glucose levels
- Tension pneumothorax: increased pressure in the thoracic cavity, leading to decreased venous return to the heart.
- Tamponade: fluid or blood in the pericardium, compressing the heart
- Toxic and/or therapeutic: chemicals, whether medication or poisoning
- Thromboembolism and related mechanical obstruction (blockage of the blood vessels to the lungs or the heart by a blood clot or other material)
As of December 2005, Advanced Cardiac Life Support guidelines have changed significantly. A major new worldwide consensus has been sought based upon the best available scientific evidence. The ratio of compressions to ventilations is now recommended as 30:2 for adults, to produce higher coronary and cerebral perfusion pressures. Defibrillation is now administered as a single shock, each followed immediately by two minutes of CPR before rhythm is re-assessed (five cycles of CPR).
ALS also covers various conditions related to cardiac arrest, such as cardiac arrhythmias (atrial fibrillation, ventricular tachycardia), poisoning and effectively all conditions that may lead to cardiac arrest if untreated, apart from the truly surgical emergencies (which are covered by Advanced Trauma Life Support).
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