Provision of anaesthesia in difficult situations and the developing world

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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.

Figure 27.1 EMO ether vaporizer. (1) Inlet port, (2) outlet port, (3) concentration control, (4) water jacket, (5) thermocompensator valve, (6) vaporizing chamber, (7) filling port for water, (8) filling port for anaesthetic, (9) anaesthetic-level indicator.

Reproduced with permission of WHO from Dobson MB. Anaesthesia at the District Hospital. Geneva: World Health Organization; 1988.

Figure 27.2 Oxford miniature vaporizer (OMV). (1) Inlet port, (2) outlet port, (3) concentration control, (4) heat sink (5) vaporizing chamber, (6) filling port for water, (7) filling port for anaesthetic, (8) anaesthetic-level indicator.

Reproduced with permission of WHO from Dobson MB. Anaesthesia at the District Hospital. Geneva: World Health Organization; 1988.

Figure 27.3 PAC (Portable Anaesthesia Complete) vaporizer (Ohmeda). (1) Concentration control, (2) filling port for ether, (3) ether-level gauge, (4) outlet and one-way valve, (5) vaporizing chamber, (6) thermocompensator valve, (7) port for oxygen enrichment.

Reproduced with permission of WHO from Dobson MB. Anaesthesia at the District Hospital. Geneva: World Health Organization; 1988.

Figure 27.4 Diamedica vaporizer. This is a 150 ml agent capacity draw-over vaporizer for isoflurane or halothane. The dial lever causes a shuttle to move against the stationary obturator, altering the size of the bypass route annulus. A calibration nut (not drawn) moves the obturator and is for factory or service technician use.

Photograph courtesy of Diamedica (UK) Ltd. Schematic redrawn from an original kindly supplied by Diamedica (UK) Ltd.

Practical equipment for safe anaesthesia can be provided by a combination of:

• the EMO vaporizer and/or the OMV (calibrated and used for halothane, isoflurane or trichloroethylene)

• a means of inflation such as a manual resuscitator or Oxford bellows

• a Ruben, Laerdal pattern or similar non-rebreathing valve (see Chapter 8)

• a facemask or endotracheal connector and tube.

The facility for giving supplementary oxygen, using a T-piece and reservoir tubing as with the Triservice apparatus (see below), is desirable.

Various arrangements of draw-over apparatus are shown in Fig. 27.5, and the working principles of the commonly available draw-over vaporizers are shown in Figs. 27.1–4.

Figure 27.5 Several arrangements of draw-over apparatus: OIB, Oxford inflating bellows (Penlon); EMO, Epstein-Macintosh-Oxford ether vaporizer (Penlon); OMV, Oxford Miniature Vaporizer (Penlon); NRV, non-rebreathing valve (e.g. Ruben); SIB, self-inflating bag (Laerdal, Ambu, etc.); PAC, Portable Anaesthesia Complete (Ohmeda).

Reproduced with permission of WHO from Dobson MB. Anaesthesia at the District Hospital. Geneva: World Health Organization; 1988.

These vaporizers, like the Triservice Apparatus, are not CE marked as the problems of poor calibration, lack of temperature compensation and inherent risk of spillage of agent into the breathing circuit are insurmountable. This causes difficulty in attempts to gain experience with the equipment in the modern hospital environment, where patients are entitled to receive the highest standard of available care. The issue of standards is in fact a significant and wide-ranging one. It is argued that the standards organizations, in being dominated by manufacturers, produce standards geared to driving sales of the latest technology to wealthy nations.⁶ Such equipment does not address the needs of developing nations and the standards inhibit ‘low technology’ developments.

There are, however, courses available to demonstrate the use of such draw-over apparatus, using highly sophisticated anaesthetic simulators.

Supplemental oxygen

Medical oxygen may be available in cylinders, but these may not follow international standards of cylinder identification, and apparently full cylinders may be found to be empty. Industrial oxygen may be available, but be aware that there may be an increased level of impurities in such supplies. Up to 95% high-quality oxygen may be obtained from an oxygen concentrator (see Chapter 1). Oxygen concentrators are relatively maintenance-free, but require a source of electrical power to run a compressor and a switching device. A concentrator the size of a small domestic fridge will produce an inexhaustible supply of oxygen at the rate of up to 10 l min⁻¹.

Ventilators suitable for developing countries

Manley Multivent ventilator

This ventilator was developed by the late Roger Manley, specifically for use in developing countries (Fig. 27.6).⁷ It differs from most other gas driven ventilators, in that the volume of gas required to drive the ventilator is only one-tenth of the patient’s minute volume. Furthermore, if the driving gas is oxygen it may be automatically collected and used to supplement the inspired oxygen concentration. Used in this way, set at a minute volume of 4 l min⁻¹, an E size oxygen cylinder containing 680 L would drive the ventilator and supply 35% oxygen in air for a period of 28 h. The ventilator consists of a weighted beam, attached at one end to a fulcrum and at the other end to the top of the bellows. The beam is pushed upwards by the driving gas under a pressure of at least 140 KPa acting on a piston. When the set tidal volume is reached, the flow of driving gas is interrupted and the weight of the beam compresses the bellows, delivering the mixture of anaesthetic gasses to the patient. The economy of driving gas is achieved by the relative distances of the piston and the bellows to the fulcrum. Should the supply of pressurized gas fail completely, the bellows can be operated manually.

Figure 27.6 Manley Multivent.

Photo courtesy of Penlon Ltd, UK.

Combination anaesthetic equipment

A number of ingenious machines incorporating an oxygen concentrator, oxygen cylinders, a ventilator, and vaporizers, which can be used in either draw-over or continuous flow mode, assembled on a mobile trolley, have been produced such as the prototype ‘Fentolator’ developed by Paul Fenton in Malawi.⁸ The advantages of such equipment in principle is that it is permanently assembled and available, aiming to be seen as the complete versatile anaesthetic machine. If monitoring equipment is available, this can be incorporated as well. Two fully developed examples of such combination equipment are the ‘Glostavent’ (Fig. 27.7) developed by Roger Eltringham in Gloucester, UK.⁹ based originally on the Manley Multivent Ventilator described above, and the Universal Anaesthesia Machine.

Figure 27.7 Glostavent Anaesthetic Machine, with Glostavent AP ventilator and oxygen concentrator.

Photograph courtesy of Diamedica (UK) Ltd.

Finally, the other essential piece of equipment is suction apparatus. In areas where electricity supply may be unreliable, it is advisable to have manual or foot-operated suction apparatus.

Universal Anaesthesia Machine (UAM)

At the time of writing, the very newly produced UAM (Fig. 27.8) is starting to undergo field evaluations, and represents the only CE marked anaesthesia machine designed with the needs of developing countries in mind. Developed by Paul Fenton and manufactured by OES Medical (Abingdon, UK), production has been made possible as a result of funding by the Nick Simons Foundation: a charitable organization dedicated to providing medical care in rural Nepal.

Figure 27.8 Universal Anaesthesia Machine.

Photo courtesy of OES Medical, Abingdon, UK.

The UAM keeps the failsafe features of draw-over anaesthesia, but by removing the need for a non-rebreathing valve at the patient end of the breathing attachment allows use of modern lightweight coaxial or Y configured dual-limb breathing tubes, which also facilitate waste anaesthetic gas scavenging. The key feature in this is the balloon valve, incorporated into the machine, which occludes the expiratory limb of the breathing system through an actuator pipe that is pressurized from the breathing system to allow positive pressure ventilation (Fig. 27.9). A one way flap valve distal to the balloon occluder ensures unidirectional flow through the breathing system during spontaneous respiration.

Figure 27.9 Gas flow schematic of the UAM from a drawing by Dr Paul Fenton at www.uamachine.org. See text.

The machine houses a built-in oxygen concentrator capable of producing up to 10 L min⁻¹, but also has cylinder yokes for oxygen and nitrous oxide as well as connections for pipeline oxygen. An additional low pressure O₂ inlet is provided distal to the flowmeters. A fuel cell oxygen analyzer downstream of the calibrated vaporizer linked to an electronically operated valve shuts off the nitrous oxide supply where a minimum of 35% O₂ is not detected. Positive and negative pressure relief valves upstream of the vaporizer and reservoir bag allow entrainment of room air and hence anaesthesia delivery in the absence of power or gas supplies. A pressure transducer at this level can act as an ‘apnoea alarm’ by warning of distension of the reservoir bag, which indicates diminished patient minute volume in comparison to the fresh gas flow rate. The inflating bellows can be used to assist or take over ventilation as in other draw-over systems.

Future iterations of the UAM are planned to include an in-line electrically powered bellows ventilator within the oxygen concentrator housing and an integral circle system and absorber. The aforementioned, with high-quality production values and materials, multiple source oxygen facilities allowing continuous flow gas delivery, low maintenance requirements, the use of modern breathing systems in a draw-over configuration and CE marking; all in a restricted cost device, aim to permit use in any hospital setting.

Major accidents and disasters

These may occur in any part of the world at any time, and are by definition unexpected. All medical services should have a plan to deal with major disasters. A typical approach is to have a mobile medical team that can be rapidly deployed to the disaster site and a receiving hospital capable of dealing with the retrieved casualties. In the event of the number of casualties overwhelming the initial response, there should be a means of either escalating the number of teams or hospitals deployed. In developing countries, there may be a need to seek international assistance. Many countries have teams available for worldwide deployment at short notice. Particular problems encountered include:

• unfamiliar territory

• unfriendly environment:

extremes of hot and cold and altitude, even in normally temperate climates

dark, wet, cramped conditions

• unfamiliar injuries:

blast and crush injuries

delayed extrication

• risk to rescuers:

nuclear, biological or chemical incidents

terrorism

fire, explosion risk

continuing disaster (e.g. earthquake)

– unstable buildings.

The predominant anaesthetic contribution to a major disaster is resuscitation and stabilization prior to transfer to the receiving medical facility. Exceptionally, to aid extrication of casualties, amputation of trapped limbs may be required. This is best achieved using ketamine, either intravenously or intramuscularly. Equipment for intubation, self-inflating bag, fluid and cannulae for intravenous fluid resuscitation should be available. Oxygen and Entonox should be used cautiously in such conditions as they support and accelerate combustion of flammable materials, and whilst the latter has excellent analgesic properties, it may not be suitable in very cold conditions (see note Table 1.4) or in the presence of a head injury or pneumothorax.

The battlefield

Mobile field hospitals are deployed as close to the battlefront as safety will allow, and receive casualties who will normally have had only life-saving first-aid treatment at a regimental aid post or equivalent. In addition to military casualties from both sides of the conflict, there are frequently civilian casualties, which may include children. This poses a problem if paediatric equipment is not available. Large numbers of casualties may arrive simultaneously, and require triage on arrival. In some, immediate surgery is required as part of the resuscitation process. Some of the features of military anaesthesia are as follows:

• equipment must be air portable

• oxygen cylinders or concentrators are usually readily available

• cost constraints for drugs and equipment are minimal

• resupply is not usually a problem – unless supply lines are cut.

Electricity is required for lighting, monitoring, suction, heating and refrigeration (for blood storage and some drugs), and will usually be supplied from generators that must be of sufficient power to cope with maximum demand. Vital equipment should have an independent battery back-up. Many modern pieces of equipment have a back-up supply of only 10 min. Sensitive equipment should have surge protection to limit voltage spikes from erratic power supplies.

Triservice apparatus

The equipment in use at the moment by the British military medical services is the Triservice Anaesthetic Apparatus (Fig. 27.10).^10,¹¹ This consists of two modified OMVs connected via a self-inflating bag to a non-rebreathing valve and facemask or airway device. Supplemental oxygen may be delivered upstream of the vaporizers by a T-piece with a length of corrugated tubing acting as a reservoir. This complete apparatus, including an oxygen regulator and cylinder yoke, comes securely packed in foam within an air portable container, all weighing less than 25 kg, and can be safely dropped by parachute.