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Cardiorespiratory emergency in general practice

Judith M Fisher
MB BS FRCGP FFAEM FIMC(Ed)
Medical Director Essex Ambulance Service
E:drjmfisher@msn.com

About 350,000 people die from myocardial infarction (MI) per annum in the UK, and 60,000 of these have a cardiac arrest,(1) approximately 5% of which are in the presence of a GP. Around 10% of the adult population have asthma, of which 10% have severe asthma. About 10% of hospital emergency admissions with asthma require mechanical ventilation, with deaths occurring in this group from respiratory arrest.(2)

For all acute medical emergencies the principles are the same - rapid assessment using a generic approach, best remembered in the alphabetical sequence of ABCD: Airway (with cervical spine control if there is a history of trauma); Breathing; Circulation; Disability.

Airway and breathing
Primary assessment should always include looking, listening and feeling for signs of breathing, confirming respiration and a patent airway. Is there stridor or wheeze, suggesting upper or lower airway narrowing, or is there normal speech, confirming neither?

A patent airway does not ensure adequate ventilation. You need to ensure the effectiveness of breathing - check the respiratory rate, accessory muscle use and added sounds. Is the breathing effective? Are the breath sounds normal? Is there normal chest expansion? If there is incomplete airway control, control it using simple airway maintenance techniques (jaw thrust and chin lift or simple airway adjuncts). Inadequate respiration can lead to alterations in heart rate, skin colour and mental status.

Inadequate ventilation must be supported. Ideally, oxygen should be given via a nonrebreathing mask with a reservoir bag for all patients with respiratory difficulty.

The aim of resuscitation is to restore oxygenation at a cellular level so most emergency conditions respond to oxygen (it is used for all emergencies in the first hour). Inspired air contains around 21%, whereas simple airway devices with entrained oxygen can achieve levels of 40%. A valve mask device with an oxygen reservoir bag can deliver even higher concentrations. Patients with chronic airways disease and a poor respiratory drive can be given oxygen unless they carry a hospital card asking medical staff to refrain from this, as anoxia may be detrimental.

In respiratory emergencies with poor air entry, oxygen will improve the quality of inspired air, whereas with cardiac conditions, inspired air enriched with oxygen will improve oxygen delivery, even when the circulation is impaired. Finally, with any anaemia, where oxygen-carrying capacity is impaired, improvements can be obtained with higher concentrations of inspired oxygen. The only situation where oxygen is contraindicated is in paraquat poisoning, where it enhances the toxicity.(3)

Once it has been established that there is a pulse present, assess the heart rate, pulse volume and capillary refill. (If there is no pulse, move to the cardiac arrest protocol.) To confirm there is effective circulation, check skin appearance, temperature and mental status. Oxygen is the first intervention of choice when there is inadequate circulation, followed by intravenous access (for later medication or infusion). Subsequent interventions are dependent on diagnosis, but if there is loss of circulating volume, intravenous saline 0.9% is appropriate.

Do not assume that a decreased level of consciousness is because of a primary neurological problem. After checking the ABCs, undertake a simple neurological assessment known as AVPU: Alert; Verbal (responds to voice); Pain (responds only to pain); Unresponsive. Also check for convulsive movements and levels of blood sugar. The more complex Glasgow Coma Score is used later (usually in hospital) for a more indepth assessment.

Again, oxygen is the treatment of choice with specific interventions dependent upon the diagnosis - glucose 500ml of 10% IV for hypoglycaemia, diazepam or lorazepam for uncontrolled fitting.

Specific cardiorespiratory emergencies

Cardiac arrest
Advanced life support protocols from the Resuscitation Council should be available in the practice premises.(4) Defibrillators - especially the cheaper and simple automated external defibrillators (AED) - are suitable for use by GPs, practice nurses and even the lay public. Defibrillation is most effective if given as soon as possible after a cardiac arrest with ventricular fibrillation (the most common cause of arrest). Remember to call an ambulance as soon as the arrest is diagnosed, as paramedics will be equipped with defibrillators and appropriate drugs, as well as providing transport.

Cardiac chest pain
This encompasses all acute coronary syndromes. Ask the patient to describe pain severity, location, duration, radiation, whether it was present before, is it relieved by anything, usual medications, and any past cardiac history? If you suspect an acute MI, call for ambulance backup immediately - nearly 50% of patients die before reaching hospital, and prompt treatment will reduce this. Treatment consists of oxygen, aspirin, GTN, opiate analgesia, antiemetics, and consider thrombolysis if electrocardiogram confirms diagnosis.

Studies have demonstrated the value of earlier thrombolysis, and with simple, single-dose bolus drugs now available, family doctors have the opportunity to improve the outcome from MI by offering prehospital thrombolysis.5 In France, where the emergency call system involves a physician-led response through the SAMU system, prehospital thrombolysis is the gold standard, and in Holland the ambulance service has offered thrombolysis for the last 12 years without raising the incidence of complications. The UK has had a cautious approach, but in Scotland there is a dual response from the ambulance service and GPs in some areas. In fact this is where the first trials of GP prehospital thrombolysis were pioneered.

Anaphylaxis
Diagnosis follows a multisystem allergic response and/or a prior history. Look for a "Medic Alert" pendant. Presentation is variable, and you should assume the worst. Give oxygen and intramuscular adrenaline (0.5ml 1:1,000, repeat in five minutes if no response) and monitor the radial pulse. Give nebulised salbutamol if there is bronchospasm. Do not be afraid of repeating the adrenaline if there is no improvement.

Asthma
Assess respiratory system (as above) - normal speech is reassuring, a silent chest is not. Beware the critically ill asthmatic who has a tension pneumothorax. Severe asthma occurs when the PEFR (peak expiratory flow rate) is 25, pulse >110bpm. Life-threatening asthma involves PEFR Asthma treatment involves ABCs and oxygen, repeated PEFR, and salbutamol 5mg in 2.5ml nebule, repeated after five minutes if needed. Drive the nebuliser with oxygen, and consider steroids and hospital transfer.

Tension pneumothorax
This should be suspected when there is no improvement in asthma, despite aggressive therapy. Look for hyper-resonance, a deviated trachea and circulatory collapse. Treatment involves insertion of a 14G/16G cannula into the second intercostal space in the midclavicular line - listen for the whoosh of air (please tell the hospital if this has been done).

Conclusion
Many acute cardiorespiratory emergencies will benefit from your intervention, even if this is undertaken in conjunction with the ambulance service. These diseases are all conditions where an ambulance should respond within eight minutes, so backup support and equipment is never far away. However, eight minutes is too long to leave patients whose airways and circulation are compromised, since brain tissue and myocardium deteriorate after three minutes reduced or absent circulation.

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References

  1. Murray C, Lopez A. Mortality by cause of eight regions of the world; Global Burden of Disease Study. Lancet 1997;349:1269-76.
  2. Turner MT, et al. Risk factors for near fatal asthma. Am J Respir Crit Care Med 1998;157:1804-9.
  3. Poisons Information Service. Available from URL: http://www.spib. axl.co.uk/toxbase/treatments/paraquat%20-%20ingestion.htm
  4. AHA/ILCOR. International guide-lines for CPR and ECC. A consensus on science. Resuscitation 2000;46:1-448.
  5. Boersma E, et al. Early thrombolytic treatment in acute myocardial infarction: reappraisal of the golden hour. Lancet 1996;348:771-5.
  6. GREAT Group. Feasibility, safety and efficacy of domiciliary thrombolysis by general practitioners. Grampian regional early anistreplase trial. BMJ 1992;305:548-53.
  7. Project team of the Resuscitation Council UK. Update on the emergency medical treatment of anaphylactic reactions for first medical responders and for community nurses. Resuscitation 2001;48:241-3.

Resources
Advanced Life Support Group
W:www.alsg.org/main_index.htm
British Heart Foundation
W:www.bhf.org.uk
Primary Care National Electronic Library for Health
W:www.nelh-pc.nhs.uk/
Resuscitation Council
W:www.resus.org.uk