Want to watch this video? Sign up for the course here. Or enter your email below to watch one free video.

Unlock This Video Now for FREE

This video is normally available to paying customers.
You may unlock this video for FREE. Enter your email address for instant access AND to receive ongoing updates and special discounts related to this topic.

As mentioned, the reversible causes of cardiac arrest are listed as 4 Hs and 4 Ts. We will go through them now individually to see how we may be able to identify the cause and reverse the cause of the cardiac arrest. Looking at the Hs. Hypoxia, often a cause of a cardiac arrest. And particularly in the younger patient, in the child, the cardiac arrest is secondary to hypoxia. And we can see by delivering good quality of ventilations in our management regime that that hypoxia can be reversed.

Hypovolemia either caused by trauma or by anaphylaxis or by pump failure, IE, cardiogenic shock, can be reversed by initiating a fluid regime as part of our cardiac arrest management. Important to know with a penetrating traumatic hypovolemic arrest that this cannot be called unseen and the patients must be transported into a hospital setting where the surgeons can investigate the cause of the bleed. Common causes of hypovolemia leading into a cardiac arrest are things like gunshot and shrapnel wounds. Often these can be managed on the scene, very effectively with the application of atonic care or a hemostatic dressing to arrest the hemorrhage. In the pre-hospital setting, paramedics would also use zoledronic acid to arrest the bleeding, particularly with internal bleeding where we cannot apply direct pressure.

Continuing with the Hs, hypothermia. In the UK, our coastal waters and inland waters rarely get above a temperature of 10 degrees and with only a few minutes immersion, a patient's car temperature can drop so that become hypothermic. The hypothermic patient often has an undetectable pulse and we must monitor this patient's ECG. In terms of managing the hypothermic patient, CPR must be continued until the patient is normothermic. We often use a phrase, "They are not dead until they are warm and dead." As a precaution in the hypothermic patient, we should take extra care when we are moving them. In particular, they are at risk of ventricular fibrillation. Should the patient go into to ventricular fibrillation, we should limit our shocks to three. We should also limit our dose of adrenaline to one milligram IV, during the arrest scenario. By far, the most effective way of having a successful outcome for this patient is to continue CPR and ventilation to the hospital. This is another case where the patient cannot be declared dead on the scene.

Our final H is the metabolic imbalances, the Hyperions. For example, hyperkalemia or hypokalemia. In a pre-hospital setting, it's impossible to determine that this is the case. We can suspect it in an acidotic patient. In a hospital, blood gases can be taken and the results used to establish the cause of the arrest and appropriate management regimes.