Anaesthesia Outside the Operating Theatre
ANAESTHESIA IN REMOTE HOSPITAL LOCATIONS
General Considerations and Principles
1. Appropriate personnel. Only senior experienced anaesthetists who are also familiar with the particular environment and its challenges should normally administer anaesthesia in remote locations. Additional skilled anaesthetic help may not be readily available compared with an operating theatre suite and patients are often challenging, e.g. paediatric or critically ill.
2. Equipment. The remote clinical area may not have been designed with anaesthetic requirements in mind. Anaesthetic apparatus often competes for space with bulky equipment (e.g. scanners) and, in general, conditions are less than optimal. Monitoring capabilities and anaesthetic equipment should be of the same standard as those used in the operating department. In reality, such equipment may not be readily available and the equipment used is often the oldest in the hospital. Nevertheless, the monitoring equipment should meet the minimum standards set by the Association of Anaesthetists of Great Britain and Ireland (AAGBI, 2006). The anaesthetist who is unfamiliar with the environment should spend time becoming accustomed to the layout and equipment. Compromised access to the patient and the type of monitors used during the procedure require careful consideration. Advanced planning helps to prepare for unanticipated scenarios. Clinical observation may be limited by poor lighting.
3. Patient preparation. Preparation of the patient may be inadequate because the patient is from a ward where staff are unfamiliar with preoperative protocols, or patients may be unreliable, e.g. those presenting for ECT.
4. Assistance. An anaesthetic assistant (e.g. operating department practitioner) should be present, although this person may be unfamiliar with the environment. Maintenance of anaesthetic equipment may be less than ideal. Consequently, the anaesthetist must be particularly vigilant in checking the anaesthetic machine, particularly because it may be disconnected and moved when not in use. Empty gas cylinders need to be replaced in older suites without piped gases, and also the anaesthetist must ensure the presence of drugs, spare laryngoscope and batteries, suction and other routine equipment.
5. Communication. Communication between staff of other specialities and the anaesthetist may be poor. This may lead to failure in recognizing each other’s requirements. Education programmes for non-anaesthesia personnel regarding the care of anaesthetized patients may be of benefit.
6. Recovery. Recovery facilities are often non-existent. Anaesthetists may have to recover their own patients in the suite. Consequently, they must be familiar with the location of recovery equipment including suction, supplementary oxygen and resuscitation equipment. Alternatively, patients may be transferred to the main hospital recovery area. This requires the use of routine transfer equipment which should ideally be available as a ‘pack’ kept alongside monitoring equipment and a portable oxygen supply. This avoids searching for various pieces of equipment which may delay transfer, and ensures that nothing is forgotten. The pack should be regularly checked and maintained.
Anaesthesia in the Radiology Department
Computed Tomography
General Principles: A CT scan provides a series of tomographic axial ‘slices’ of the body. It is used most frequently for intracranial imaging and for studies of the thorax and abdomen and is the investigation of choice in the evaluation of major trauma when whole body CT may be used in place of plain X-rays. Each image is produced by computer integration of the differences in the radiation absorption coefficients between different normal tissues and between normal and abnormal tissues. The image of the structure under investigation is generated by a cathode ray tube and the brightness of each area is proportional to the absorption value.
Anaesthetic Management: Computed tomography is non-invasive and painless, requiring neither sedation nor anaesthesia for most adult patients. A few patients may require conscious sedation to relieve fears or anxieties. However, patients who cannot cooperate (most frequently paediatric and head trauma patients or those who are under the influence of alcohol or drugs) or those whose airway is at risk may need general anaesthesia to prevent movement, which degrades the image. Anaesthetists may also be asked to assist in the transfer from the ICU and in the care of critically ill patients who require CT scans.
Magnetic Resonance Imaging
General Principles: Magnetic resonance imaging (MRI) is an imaging modality which depends on magnetic fields and radiofrequency pulses for the production of its images. The imaging capabilities of MRI are superior to those of CT for examining intracranial, spinal and soft tissue lesions. MRI differentiates clearly between white and grey matter in the brain, thus making possible, for example, the in vivo diagnosis of demyelination. It may display images in the sagittal, coronal, transverse or oblique planes and has the advantage that no ionizing radiation is produced.
STAFF SAFETY: Staff safety precautions are essential. The supervising MR radiographer is operationally responsible for safety in the scanner and anaesthetic staff should defer to him or her in matters of MR safety. Screening questionnaires identify those at risk and training should be given in MR safety, electrical safety, emergency procedures arising from equipment failure and evacuation of the patient. Anaesthetists should also understand the consequences of quenching the magnet and be aware of recommendations on exposure and the need for ear protection. Long-term effects of repeated exposure to MRI fields are unknown, and pregnant staff should be offered the option not to work in the scanner. All potentially hazardous articles should be removed, e.g. watches, bleeps and stethoscopes. Bank cards, credit cards and other belongings containing electromagnetic strips become demagnetized within the vicinity of the scanner and personal computers, pagers, phones and calculators may also be damaged.
PATIENT SAFETY: Metal objects within or attached to the patient pose a risk. Jewellery, hearing aids or drug patches should be removed. Absolute contraindications include implanted surgical devices, e.g. cochlear implants, intraocular metallic objects and metal vascular clips. Pacemakers remain an absolute contraindication in most settings although some patients with a pacemaker have undergone scanning under tightly controlled conditions when the benefit has been deemed to outweigh the risk. Metallic implants, e.g. intracranial vascular clips, may be dislodged from blood vessels. Programmable shunts for hydrocephalus may malfunction because the pressure setting may be changed by the magnetic field, leading to over- or underdrainage. The use of neurostimulators such as spinal cord stimulators for chronic pain is increasing. These devices may potentially fail or cause thermal injury on exposure to the magnetic field. Each must be considered individually, some may be safe if strict guidelines are adhered to. Joint prostheses, artificial heart valves and sternal wires are safe because of fibrous tissue fixation. Patients with large metal implants should be monitored for implant heating. A description of the safety of various devices is available on dedicated websites. All patients should wear ear protection because noise levels may exceed 85 dB.
EQUIPMENT: The magnetic effects of MRI impose restrictions on the selection of anaesthetic equipment. Any ferromagnetic object distorts the magnetic field sufficiently to degrade the image. It is also likely to be propelled towards the scanner and may cause a significant accident if it makes contact with the patient or with staff. Terminology regarding equipment used in the MRI scanner has now changed from ‘MR compatible’ or ‘MR incompatible’ to ‘MR conditional’, ‘MR safe’ or ‘MR unsafe’. MR conditional equipment is that which poses no hazards in a specified MR environment with specified conditions of use. The conditions in which it may be used must accompany the device and it may not be safe to use it outside these conditions, e.g. higher field strength or rate of change of the field. MR safe equipment is that which poses no safety hazard in the MR room but it may not function normally or may degrade the image quality. Consideration needs to be given to replacing equipment if a scanner is replaced by one of higher field strength.