VOL: 97, ISSUE: 04, PAGE NO: 35
Phil Jevon, BSc, RN, PGCE, is resuscitation training officer, Manor Hospital, Walsall Hospitals NHS Trust
Beverley Ewens, BSc, RGN, is consultant nurse, Manor Hospital, Walsall Hospitals NHS TrustMore than 11,000 critically ill patients require inter-hospital transport each year (Mackenzie et al, 1997; Intensive Care Society, 1997).
More than 11,000 critically ill patients require inter-hospital transport each year (Mackenzie et al, 1997; Intensive Care Society, 1997).
But this number will probably rise as a result of an increasing tendency to concentrate specialist services such as plastic surgery, cardiothoracics and nephrology in regional centres.
Despite the large numbers of inter-hospital transports, the provision of equipment remains poor and potentially serious complications often occur (Intensive Care Society, 1997; Bion et al, 1988).
The quality and outcome of the transport depends on the experience of the transport team, meticulous clinical preparation and adequate monitoring facilities (Tan, 1997).
The same level of supervision and preparation is required for intrahospital transport of critically ill patients (Intensive Care Society, 1997).
Potential problems and hazards
At less than one per cent, mortality rates during transport are remarkably low (Hinds and Watson, 1996). But it is potentially hazardous to transport a critically ill patient, particularly if intensive haemodynamic and respiratory support is necessary and is provided by unqualified or inexperienced staff (Bion et al, 1988).
The transport of critically ill patients can result in physiological deterioration (Gentleman and Jennett, 1981; Waddell et al, 1975). The patient may not be able to tolerate lifting, tilting, abrupt movements, vibration and acceleration or deceleration (Lawler, 2000).
Accelerational forces and vertical movements can cause cardiovascular instability, particularly in patients who are hypovolaemic or vasodilated as a result of sepsis, drugs or sedation (Hinds and Watson, 1996). Significant changes in intracranial pressure can be induced by transport, for example, placing patients in the head-down position when loading them into an ambulance can exacerbate intracranial hypertension (Hinds and Watson, 1996).
Helicopter transfer may be less hazardous for critically ill patients, particularly if they are flown feet first as this results in a slightly head-up position during acceleration and a slightly head-down position during deceleration.This can minimise the changes in cardiovascular function and intracranial pressure often associated with transport (Kee et al, 1992).
An ambulance is probably the worst environment in which to care for a critically ill patient. Space limitations, movement, noise, power sources and lighting impose restrictions and the movement of the vehicle can make the performance of routine procedures a challenge.
Motion sickness is a common problem for both patients and staff, and noise and daylight may make monitors and alarms unreadable or inaudible. Ambulances rely on batteries for electrical power so hospital-based equipment that needs alternating current can be used only with its own battery or a converter.
Between 11-34% of all transports experience problems such as accidental extubation, battery failure, loss of intravenous access and the abrupt cessation of vasoactive or sedative agents (Evans and Winslow, 1995; Carson and Drew, 1994; Smith et al, 1990).
Hazards associated with air transport
The hazards associated with air transport depend to a degree on whether it is a helicopter or aeroplane and can be summarised as follows:
- Expansion of gas in closed cavities. Atmospheric pressure drops with increasing altitude and the volume occupied by gases rises, causing trapped gas to expand (Lawler, 2000). This will exacerbate a pneumothorax and can affect the air in a tracheal tube cuff. Nurses should gently fill the cuff with normal saline or continuously monitor its pressure;
- Fluid loss. Decreasing atmospheric pressure can cause fluid to extravasate from the intravascular to the interstitial spaces, resulting in oedema, hypotension and tachycardia. It can also exacerbate the effects of dehydration (Hinds and Watson, 1996);
- Hypoxia. Increasing altitude causes a fall in the partial pressure of oxygen which can lead to a decrease in alveolar oxygen and hypoxia;
- Temperature control. Heating can be a particular problem in helicopters. Patients may also be exposed to environmental conditions while being transferred to or from the aircraft;
- Noise. This can cause sensory deprivation and helicopter noise, in particular, can interfere with monitoring, especially audible warning devices (Kee et al, 1992);
- Vibrations. These can make monitoring difficult and interfere with gravity-dependent intravenous fluid administration;
- Visibility. This may be reduced and, combined with noise, can make monitoring difficult and obscure visual alarms;
- Unfamiliar environments.
Patient monitoring equipment
Deciding what monitoring equipment to take depends on the condition of the patient and the resources available. All equipment should be:
- Lightweight, yet durable and robust;
- Restrained, yet easily accessible;
- Regularly checked;
- Battery powered, if it is electrical.
Ideally, equipment should have both audible and visual alarms. A small, versatile, portable monitor is invaluable. Infusion pumps and appropriate medications should be available and it is important to ensure that essential infusions, such as vasoactive drugs, do not run out during transfer.
Although a mobile telephone should be available to aid communication, any possible effect on monitoring equipment should be checked.
Monitoring during transfer
Standard of care and monitoring during transport, which depend on the needs of each patient, should be maintained at the same level as on the intensive care unit. The Intensive Care Society (1997) recommends that:
- Arterial oxygenation, electrocardiogram and arterial pressure is monitored. Invasive arterial monitoring is preferable to non-invasive because of sensitivity to motion;
- Central venous pressure, pulmonary artery wedge pressure or intracranial pressure may be required in some patients, but interpretation can be difficult in a moving ambulance and treatment is therefore difficult to control;
- If the patient is mechanically ventilated, oxygen supply and airway pressure should be monitored and there should be some means to detect disconnection (Knowles et al, 1999);
- End-tidal CO2 measurements are desirable, particularly in patients with cerebral injury, but less than 50% of hospitals have the facilities to do this during transport (Knowles et al, 1999);
- Temperature should be monitored, if it is abnormal, during long journeys or cold weather;
Assessing the adequacy of ventilation is notoriously difficult in an ambulance (Knowles et al, 1999). In addition to monitoring the patient, it is important to continuously monitor the equipment, particularly alarms. Intravenous infusions should also be closely monitored to ensure the prescribed dose is being administered.
Transporting critically ill patients can be hazardous so it is important to justify any such decision. Knowledge of any potential problems associated with transport is also essential for accurate and effective monitoring, minimising morbidity and mortality.
Meticulous clinical preparation, appropriate equipment and experienced staff who are familiar with the transport environment will reduce the risks. The same level of supervision and preparation is important when critically ill patients are transferred between hospital departments.