Airwaybreathing

Observing the patient's level of consciousness, chest movement, respiratory rate and noise of breathing will all yield important information. This will be of even greater significance in association with recordings of, for example, blood pressure and heart rate.

Following a cardiac arrest, patients can be sufficiently alert to adequately maintain their own airway. Alternatively some may have been intubated during resuscitation and will require the endotracheal tube to remain in place for a short period during the post-resuscitation phase.

Assisted ventilation may be required in the period after the arrest for the following reasons:

• spontaneous breathing inadequate, breaths are too slow or shallow;

• oxygen and carbon dioxide levels require alteration and optimisation;

• patient unable to maintain required work of breathing;

• stabilise the patient's cardiopulmonary status.

The process of respiration enables oxygen uptake and the removal of carbon dioxide. It is obviously essential to deliver adequate levels of oxygen in order to prevent tissue hypoxia, which can increase the risk of further arrest and also deprive the brain of vital oxygen supplies.

In certain circumstances excessive assisted ventilation or hyperventilation by the patient can lead to a fall in carbon dioxide (CO2) levels (hypocarbia). This can lead to a reduction in blood flow to the brain (Resuscitation Council UK 2000).

Table 12.1 Basic rules of monitoring.

Machines are fallible; always check the patient

Using machines to monitor patients does not replace basic clinical skills and close observation

The readings and their significance must be understood by the nurse recording them

Trends are more important than one-off measurement in determining whether patient is improving or deteriorating

• Poor contact of monitoring electrodes may cause a picture of asystole to appear on the monitor

• Changes in patient's mental status, skin colour and skin temperature will not be detected by cardiac monitoring and recording blood pressure

• Those caring for patients on cardiac monitors must have skills to recognise changes in rhythm and respond appropriately

• A heart rate of 60 beats per minute is likely to be entirely normal; however, it would be hugely significant if it had been 120 one hour earlier

Oxygen saturation

Arterial oxygen saturation (SaO2) describes the percentage of haemoglobin that is saturated with oxygen and is a useful measure of oxygen delivery. An SaO2 of 97% indicates 97% of the total haemoglobin in the blood contains molecules of oxygen (Moore 2004). However, the patient with a low haemoglobin may have a very high oxygen saturation, even though the oxygen-carrying capacity of the blood is greatly reduced. Oxygen saturation monitors do not measure CO2 levels nor do they offer any guidance on respiratory performance. The saturation sensor is usually placed on an area that is well perfused, such as the tip of the finger or ear lobe. If perfusion to that extremity is reduced the probe will not pick up a trace and will alarm for this reason and not because the saturation has necessarily dropped (Howell 2002). Other factors that can affect the trace include:

• patient movement, restlessness;

• dark skin pigmentation, jaundice and high serum bilirubin levels;

• blood, dirt or (blue or black) nail polish between sensor and finger;

• dysrhythmias;

• anaemia or abnormal haemoglobin. Circulation

Inadequate circulation can be the cause or the consequence of cardiac arrest. It is essential to regularly assess blood pressure, pulse and respiration in order to recognise cardiac dysfunction and rhythm instability, which may follow an arrest and will require support until adequate perfusion has been reestablished. It is worth noting that a rising respiratory rate is one of the earliest signs of circulatory failure.

Cardiac monitoring

Chapter 8 explained that the electrocardiogram (ECG) trace may be entirely normal in the presence of a cardiac arrest. This reinforces the point that the patient should be the focus of attention, not the monitor. Alterations in the rate and rhythm may be of cardiac origin or may reflect dysfunction in other systems, for example in the lungs or in electrolytes. Changes in the cardiac rhythm may be very dramatic and sudden, such as the onset of ventricular fibrillation (VF), or may be more subtle, such as a gradual rise in heart rate due to bleeding. The monitor will usefully detect changes, as seen in Table 12.2.

Central venous pressure monitoring

Central venous pressure (CVP) is the pressure in the central veins (caused by blood volume) as it enters the right atrium of the heart. It provides a measure of the circulating volume in the body. Measurement of the CVP assists the nurse in optimising pressures in the right and left sides of the heart. In right heart failure fluids may be needed to stretch the right ventricle to make the heart work more efficiently. Alternatively, in left heart failure diuretics and nitrates may be required to reduce the workload of the left ventricle, resulting in a predicted fall in CVP.

Table 12.2 Monitoring ECG changes.

Rhythm disturbance

Examples of possible cause

Irregular heart rhythm

• Hypoxia

• Myocardial ischaemia

• Heart block

• Atrial fibrillation (AF)

• Malfunctioning artificial pacemaker

Widening QRS complexes

• Rhythm originating in the ventricles

• Bundle branch block

• Electrolyte imbalance

• Poisoning

• Hypothermia

Lengthening PR interval

• Deterioration of AV node function

P waves independent from QRS

• Absence of conduction across AV

complexes

node (complete heart block)

It is essential that all CVP measurements be taken from the same place, either the sternal angle or from the mid-axillae, where the fourth intercostal space and mid-axillary line intersect (Woodrow 2004). However, changes in patient position, hyperinflation of the lungs, over-hydration and dehydration may also alter CVP readings.

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