The prehospital setting

There is continuing evidence supporting the importance of the chain working as a single unit rather than as separate entities. Researchers have clearly demonstrated that survival is severely diminished if a single link fails (Cummins et al. 1991).

Table 4.2 Effects of minimal delay.

Collapse to CPR

Collapse to defibrillation

<10mins

>10 mins

<5 mins

37% survival

7% survival

>5mins

20% survival

0% survival

How the chain may break

• Access - this may be delayed if the casualty is in an unsafe environment, is not found or if bystanders are either unwilling or lacking confidence to get involved.

• CPR - a lay person finding a casualty may phone for help very rapidly but then fail to provide effective CPR. Survival to discharge from out-of-hospital arrest doubles if CPR is started within four minutes (Larsen et al. 1993). Effective CPR is associated with a greater incidence of the first recorded rhythm being VF (Dowie et al. 2003).

• Defibrillation - even if a rapid phone call for help and bystander CPR do occur immediately, defibrillation may be delayed by a number of factors such as traffic and distance.

The success of the chain in the pre-hospital setting is demonstrated in examples where limited equipment is available, such as on aeroplanes (Page et al. 2000), railway stations (Davies 2002), in GP surgeries (Colquhoun 2002) and in Las Vegas casinos (Valenzuela et al. 2000). In all these settings the time from collapse to being found was short (early access), CPR was started promptly (early CPR) and they are all settings where shock advisory defibrillators were provided (early defibrillation).

Compared to the first three links, the introduction of drugs has had only limited impact (Mitchell et al. 2000).

Table 4.2 illustrates that where either early CPR or early defi-brillation occurs, the survival is considerably less than if both occur with minimal delay (Cummins et al. 1985). The ideal provision for out-of-hospital arrests includes:

• large percentage of the population know how to summon emergency help;

• high proportion of the public trained to recognise and respond to cardiac arrest;

• public access defibrillators and first responder schemes in place;

• rapid response from emergency medical services. The in-hospital setting

When an inpatient has a cardiac arrest, their chances of surviving to discharge from hospital are approximately 1 in 7 (Gwinnutt et al. 2000).

In the hospital environment early access and early CPR should be achieved by appropriate staff training. In addition to this, many nurses and doctors will be available to defibrillate the casualty and provide ALS. At first glance, the Chain of Survival looks very strong so it is of concern that the overall inhospital survival is only 17%.

Underlying factors for this survival rate might include the following.

• The degree of illness (co-morbidity) present in the inhospital population. Compared to the general population, this group is more likely to be suffering from chronic disease. It has been shown that the greater the degree of chronic disease, the lower the chances of survival from cardiac arrest (Ambury et al. 2000).

• The first presenting cardiac rhythm, which is likely to be non-shockable. These cardiac arrest rhythms have lower survival rates than VF/VT arrests and are the presenting rhythm in two-thirds of in-hospital arrests (Gwinnutt et al. 2000).

• The patient is very likely to deteriorate either gradually or dramatically over a period of time. At the end of this period of inadequate ventilation or circulatory failure, the patient will be suffering some degree of hypoxia and multiorgan failure. Cardiac arrest in this instance will be more difficult to reverse.

The concept of the Chain of Survival has demonstrated that each link on its own has limited benefit unless all the links in the chain are present. When dealing with the sick or deteriorating in-hospital patient, it could be considered that there is a

'Chain of Responsibility'. When a critical incident occurs it is rarely found to be the fault of one individual but is more commonly proved to be a failure in the system (DoH 1998). Evidence of the failure of a system includes such examples as:

• deteriorating clinical signs not recorded;

• signs recorded but their importance not understood;

• signs recorded and understood but not reported;

• signs reported but not acted upon with necessary haste;

• acted on with sufficient haste but by insufficiently experienced personnel.

It is worth considering which of the examples above are the responsibility of the nurse looking after the patient. The first four examples are the nurse's direct responsibility, not that of the attending medical staff. It is certainly possible for the nurse to influence, if not ensure that expert help of the required seniority is summoned to the deteriorating patient.

Systems are now being routinely used in hospital settings to more rigorously monitor high-risk patients to recognise signs of deterioration and to increase speed of response from expert help, with the aim of preventing unnecessary cardiac arrests occurring (see Chapter 2).

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