Chapter 27 Provision of anaesthesia in difficult situations and the developing world
• lack of continuous electricity supply
• lack of continuous supply of oxygen and nitrous oxide
• difficulty with storage of drugs and equipment
• difficulty in transport and supply of drugs and equipment
• lack of maintenance of equipment
Where possible, on grounds of safety, patients should be transferred to medical facilities capable of providing the appropriate level of care. For example, electroconvulsive therapy for the psychiatric patient with severe aortic stenosis and depression would be better managed (from their cardiac status) in the operating suite of the main hospital rather than in a room off the psychiatric ward. Non-essential surgery should not be undertaken at the site of a major disaster or on the battlefield, and the use of local, regional or sedative techniques should be considered where appropriate.
Difficult situations within hospitals
Sites away from the operating theatres often have anaesthetic equipment that is used only occasionally. Piped oxygen and suction facilities may be absent. The equipment in such areas must be maintained and checked adequately, with basic monitoring meeting the standard recommended by the Association of Anaesthetists.1 Since January 2003, all anaesthetic machines in use in the UK must be incapable of delivering a hypoxic mixture. There must be immediate access to resuscitation equipment and drugs, and a means of summoning additional assistance (i.e. telephone or intercom). The anaesthetist and their assistant should have sufficient experience and be familiar with both the environment and the equipment.
Radiotherapy units
• Intense ionizing radiation requiring patient isolation from the medical attendants
• Closed circuit television or glass-liquid-glass window to view patient causing colour and image distortion
• Multiple frequent treatments over a few weeks
• Radiotherapy applicators may obstruct access to the patient’s head.
Magnetic resonance imaging (MRI)2
• Intense magnetic field with the ability to cause equipment made of ferromagnetic material to be attracted at projectile velocity into the scanner. There is, however, a rapid decrease in field strength with distance
• Electrical inductance – potential for thermal injury from electrical conducting leads
• Electromagnetic interference leading to equipment malfunction (e.g. in syringe drivers) or artefact (e.g. altered ST-T region on ECG, from electrical currents induced by aortic blood flow in a magnetic field, rendering ischaemia detection difficult)
• Noise from vibration of switched gradient coils makes audible alarms inappropriate and necessitates ear protection
• Theoretical risk of hypoxia if quenching of the super-conducting magnets of cryogenic gasses (usually helium) occurs. Quenching may occur as a fault condition or be initiated for emergency shutdown of the magnet, and should be safe if gasses are appropriately vented to the outside.
These factors pose risks to patients and potential occupational hazards to staff. Patients and staff must be screened before access is granted to an MRI scanner, to exclude ferromagnetic implants, such as aneurysm clips or pacemakers.2 Anaesthetic equipment taken into the vicinity of the MRI scanner must be MR-compatible.
Remote anaesthesia
• TIVA may be employed using long infusion lines on pumps which must be able to cope with the high resistance to flow caused by the increased length. This usually means setting to maximum the pressure limit for sensing an occlusion.
• Whilst sedation may be sufficient for some patients, the airway may need to be established with a supraglottic airway device or tracheal tube.
• Intermittent positive pressure ventilation through a long coaxial breathing system such as a 9.6–10 m Bain circuit and Nuffield Penlon series 200 ventilator, has been shown to provide safe anaesthesia.3 With this system, there is an increase in the static compliance in proportion to the length of the tubing. This is caused by expansion of the breathing hose and compression of the volume of gas during positive pressure ventilation and will result in a lower tidal volume being delivered than is set on the ventilator although this may be mitigated by the tidal volume supplementation from the fresh gas flow. Capnography is essential. In children, if a Newton valve is used, the ventilator becomes a pressure generator, and the increased resistance and compliance of the long system results in the pressure delivered being significantly less than that selected (23% less with a 10 kg child). This compares to a 6–11% reduction when using a long rubber Ayre’s T-piece.4
• The capnography signal is delayed due to the length of the sampling line but provides a guide for adjustment of the tidal volume.
Interhospital transfers
• Communication between transferring and receiving teams and the ambulance service is essential. It is imperative that everyone concerned knows the current condition of the patient, the indication for transfer and the exact destination. It is also the responsibility of the referring team to arrange a suitably qualified medical escort.
• Documentation must stay with the patient. This includes the notes from the whole patient episode plus any additional relevant past notes, blood results and X-rays – either as hard copies or on CD. If blood has been cross-matched, it is worth transferring with the patient if the transfer is less than 4 hours because even though the receiving hospital will want to reissue it, this will be quicker than starting a cross-match from scratch.
• The patient should be stabilized as far as possible prior to transfer. The accompanying anaesthetist is unlikely to be familiar with the ambulance or what sort of equipment is immediately available and, therefore, should plan for all potential problems. In particular they should calculate the amount of oxygen that is going to be required and whether that has been catered for, the battery life on any infusion pumps should be adequate to allow for delays in traffic, etc., and spare infusions drawn up if necessary. Similarly, basic checks of equipment, such as availability of endotracheal tubes, working laryngoscopes, self-inflating resuscitation bag and IV cannulae, should not be omitted.
Developing countries
‘District hospital’-based anaesthesia
Draw-over anaesthesia
• means of giving supplemental oxygen (T-piece, length of tubing to use as oxygen reservoir and source of oxygen – i.e. cylinder or concentrator).
Draw-over apparatus
Several draw-over vaporizers are available, including the Epstein-Macintosh-Oxford (EMO) (Fig. 27.1), Oxford miniature vaporizer (OMV, described in greater detail below) (Fig. 27.2), the now discontinued Ohmeda PAC which is still in widespread use (Fig. 27.3) and the recently introduced Diamedica vaporizer5 (Fig. 27.4). The EMO and OMV vaporizers are elucidated further in Chapter 3.