Provision of anaesthesia in difficult situations and the developing world

Published on 27/02/2015 by admin

Last modified 27/02/2015

Print this page

This article have been viewed 2011 times

Chapter 27 Provision of anaesthesia in difficult situations and the developing world

The provision of anaesthesia in modern well-equipped operating theatres is dependent on sophisticated electronic equipment that requires an uninterrupted supply of both electricity and compressed gasses. Such equipment is not readily transportable, although it may be moved within a hospital facility. There are many locations throughout the world where anaesthesia is administered to facilitate surgery, investigations or other forms of treatment outside this generally accepted ‘safe’ environment.

The following are examples of locations and situations away from hospital operating theatres where anaesthesia may be required, and where simpler or alternative means of providing anaesthesia may need to be employed:

Domiciliary anaesthesia – as in kitchen table appendicectomy and obstetric flying squad interventions – has long been abandoned on safety grounds and, more recently, so has anaesthesia in dental surgeries in the UK.

All of these situations are remote from the relatively safe, comfortable and familiar operating theatre anaesthetic environment, and the following problems may be encountered to a greater or lesser degree:

• 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

• lack of skilled assistance

• lack of control of environment

• financial restrictions.

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.

The overriding principle in providing anaesthesia under any of these conditions should be to use a simple, safe technique familiar to the practitioner. To reduce complexity and avoid the potential administration of a hypoxic gas mixture as well as reducing the need for scavenging (and for many other well-documented reasons), there is a case for avoiding the use of nitrous oxide entirely. Training and practice in such techniques is invaluable for the time when they may be required. Even within a modern operating theatre environment, a ‘difficult situation’ may arise due to failure of a sophisticated electronic anaesthetic workstation, a major power cut with failure of back-up generators or a disruption to piped gas supply. The use of total intravenous anaesthesia (TIVA) together with a self-inflating bag and a free-standing oxygen cylinder, combined with practical clinical monitoring, will allow adequate and safe anaesthesia in such a situation. Under such circumstances a hands-free torch or headlight may be the most essential item of additional equipment.

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.

Some specific problems with regard to patients, medical attendants and equipment within particular areas are listed below.

Radiology departments

• Ionizing radiation risk

• Long procedures – e.g. coiling of intracerebral aneurysms

• Low levels of lighting

• Restricted access to patient or patient’s head

• A possible requirement to stop ventilation briefly to avoid image blurring.

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

Anaesthesia for MRI, radiotherapy and some radiological procedures may necessitate the anaesthetist and the bulk of the anaesthetic equipment being remote from the patient. This may be either to ensure all ferromagnetic equipment is outside the magnetic field, or to remove anaesthetic personnel from ionizing radiation:

• 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

It is sometimes necessary to transfer anaesthetized patients to another hospital, particularly if they require specialist services which are not available on site. Often these patients will be critically ill and the keys to their successful transfer are communication, documentation and anticipation of possible problems. All hospitals should have a checklist for 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

There are two extremes of conditions that may be met in providing anaesthesia in developing countries. The anaesthetist may be totally dependent on the equipment, drugs and personnel provided within the healthcare system of that country, or they may be part of a visiting team that is totally self-contained. Visiting teams may be very operation specific (e.g. Project Orbis, Operation Smile and other eye or cleft palate teams), or they may have a much wider remit. Operation specific teams usually have rigid pre-assessment protocols, ensuring that standardized procedures are carried out on fit patients, enabling the greatest good to be done for the largest number of people. Some visiting teams may bring all facilities needed to perform a certain number of specified operations and anaesthetics. The devices in use can then range from those seen in modern developed economies through to equipment similar to that used for battlefield anaesthesia (see below). Others opt to mainly use local equipment, adding only their own disposable equipment.

‘District hospital’-based anaesthesia

Many small hospitals in developing countries rely on non-medically qualified assistants to deliver anaesthesia under the supervision of the doctor who will also be performing the surgery. Under these conditions, anaesthetized patients are more likely to be intubated to ensure a secure airway. Most anaesthetists in developing countries work in larger hospitals, but even here they may be responsible for the training and supervision of medical assistants giving anaesthesia. Many such hospitals, large and small, will have storerooms which have become graveyards of anaesthetic machines and other equipment donated by well-meaning organizations or countries, without consideration for the spare parts or expertise needed for their maintenance. There will often be continuous flow (Boyle’s) machines, discarded as the necessary compressed medical gas supply is absent or erratic. In addition, such machines may not have anti-hypoxia devices and vaporizers may be outdated, unserviceable or grossly inaccurate.

For all these reasons, local anaesthetic techniques (nerve blocks, spinals and epidurals) should be used where appropriate.

Draw-over anaesthesia

Pressurized gas delivered in cylinders is expensive and prone to interruption of the supply chain. The case for draw-over anaesthesia is even more compelling given intermittent electrical supplies. Implicit in this is the use of air (with supplemental oxygen when available) and draw-over type vaporizers.

Draw-over anaesthesia can be employed for both spontaneous and controlled ventilation, is not dependent on compressed gasses and requires only light portable equipment (vi The battlefield). The basic equipment required comprises:

• self-inflating bag

• non-rebreathing valve

• low-resistance vaporizer

• 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.