During CPR we should consider and correct reversible causes of cardiac arrest these factors are typically remembered as the Hs and Ts.
A variety of disease processes can lead to a cardiac arrest; however, they usually boil down to one or more of the “Hs and Ts”;
- Hypoxia (give oxygen).
- Hypovolaemia (correct with IV fluids).
- Hypothermia (especially consider in cases of drowning – check with a low-reading thermometer).
- Hyperkalaemia (or hypokalaemia, hypocalcaemia, acidaemia, or other metabolic disorder). ECG may be characteristic of hyperkalaemia. Give IV calcium chloride for hyperkalaemia, hypocalcaemia and calcium-channel blocking drug overdose.
- Hydrogen Ions* (acidosis).
- Tension pneumothorax (consider if trauma or previous attempts to insert a central venous catheter).
- Tamponade (cardiac) – particularly in cases of trauma.
- Toxins or Tablets – consider reversal agents. See toxbase or the BNF.
- Thromboembolism (coronary or pulmonary) – consider thrombolytic drugs but these may take up to 90 minutes to work.
*Hydrogen Ions and Trauma are recent additions to the advanced life support guidelines on reversible causes. Consideration should also be made to hypoglycemic cardiac arrest.