The Kendrick Extrication Device (KED) is described as an ‘emergency patient handling device designed to aid in the immobilisation and short transfer movement of patients with suspected spinal/cervical injuries (Ferno-Washington, 2001). The device that evolved in the late 1970s was originally intended to assist with the immobilisation and extrication of racing drivers from their cockpit (American Academy of Orthopaedic Surgeons et al, 2012; Trafford et al, 2014). Since then it has become adopted by many ambulance services as a tool intended to assist in the immobilisation and extrication of patients, particularly from road traffic collisions (RTC) and is a recognised piece of equipment among paramedics. However, its assimilation into the pre- hospital environment and overall appropriateness in patient care should be viewed with caution. This article offers practical comment on the potential adverse risks associated around delayed extrication, the impact on respiratory function and the potential for increased movement of the casualty. Additionally, it highlights the current lack of evidence to support using the KED.
Background
Essentially the KED is a flexible mini back board that, when in position on the casualty, extends from their lower back to above their head. It also extends laterally to encompass the flanks and head, leaving the arms free to move. Used in conjunction with a cervical collar, three torso straps, two leg straps, a forehead and chin strap hold the patient into the device. Three lifting handles facilitate moving and handling (Ferno-Washington, 2001) (Figures 1 and 2).
Context
Most paramedics will be familiar with broadly described vehicle occupant extrication types summarised below (Calland, 2005; Association of Ambulance Chief Executives (AACE), 2013). Indeed, they can be useful in offering clarity in prioritising treatment and establishing timeframes relative to the clinical findings or likelihood of injury.
Summarily
With regard to these classifications and the patient conditions they highlight, it is not unreasonable to identify areas where KED use may conflict with the needs of certain patients.
Author's observations
Delay in extrication due to application
The KED takes time to apply and will likely cause a delay in the extrication of the casualty to definitive care (hospital). Teaching excellence, repeated practice and tight governance helps make efficient and safe practitioners. However, the KED is likely to be a device that is rarely used (let alone under experienced supervision) and the risk therefore is that it will not be applied in an expert and timely fashion. Within the context of extrication classifications, the KED should probably not be used for patients who have immediate or rapid needs. It is widely recognised that patients who have airway, breathing, circulatory or disability problems swing the risk/benefit equation in favour of ‘priority’ needs over a potential spinal issue (Calland, 2005; AACE, 2013). It can also be useful to think about whether the patient requires a hospital pre-alert. If so, should time be spent applying an additional immobilisation device and/or removing a car roof if there is another extrication option that balances the patient's overall needs better?
Even for those patients who appear stable but have central neck pain, consideration should be given to the potential for extensive occult bleeding which may not have manifested clinically or with the traditional signs of blood loss (Little et al, 1995). If the patient is to succumb to shock and deteriorate suddenly, it is far better for them to be out of the vehicle and in an ambulance, or ideally, already in hospital. Furthermore, in cold environments particularly, extra time on scene can lead to increased exposure to the elements, with an associated risk of coagulopathy (Wafaisade et al, 2010).
Impact on respiratory function
There is acknowledgement within the KED Users' Manual that the device can restrict respiratory function. The correct method of application involves fastening the top torso (chest strap) last to maximise the time the patient can ‘breathe more freely’ (Ferno-Washington, 2001). However, it could be argued that the middle and lower straps that lay over the lower chest/abdomen may also (by way of splinting lower chest and diaphragmatic movement) restrict tidal volumes. All of this could well be true of physiologically normal patients let alone in those patients whose oxygen demand is higher and/or an injury exists. Practitioners need to consider whether the potential for impeding ‘B’ (breathing) should weigh higher than using the KED over other methods of spinal care/extrication (for example, extricating a patient on a rescue board and then placing them onto an orthopaedic stretcher/vacuum mattress). Regardless of the clinical urgency of the situation, it is difficult to ever justify increasing the respiratory effort required of a patient.
Paradoxically greater movement of the casualty
The application of the KED involves sliding/pushing the device between the casualty and the car seat either at an angle of 45° through the door, or (more realistically allowing for manoeuvring space and avoiding the ‘B pillar’) from above with the roof removed (as demonstrated in the KED Users' Manual). There will inevitably be casualty movement while placing the device, applying and tightening the straps, moving the casualty via the carry handles (which may often require other emergency service personnel not trained in the use of the KED) and in the subsequent supine packaging of the patient suitable for easy transfer from the ambulance trolley onto the emergency department trolley. During these involved manoeuvres and adjustments any potential chest or back pain may be exacerbated with an associated rise in sympathetic drive.
Anecdotally, it has been noted that if the device is well tightened then breathing can be impaired. If the device is less firmly applied, allowing the patient to ‘breathe more freely’ then there can be considerable movement (sag) of the casualty when lifting/handling. Additionally, the application can vary significantly depending upon the seat type and the position and posture of the casualty, as well as their anatomy. Indeed, it can be hard to accomplish a textbook application—often only achievable with someone of average build sitting bolt upright or leaning forward in a classroom chair while adjusting their own body position to accommodate the device and in assistance to those applying it. Notably, many of the ad-hoc instructional videos available to view on the internet demonstrate exactly this (EMS Skills Video, 2013).
Recently there has been a developing consensus of opinion and evidence questioning the need for high interventionist measures in extricating casualties, largely based around excess movement of the C-spine. In 2012, the Faculty of Pre-hospital care, Royal College of Surgeons of Edinburgh presented a consensus statement, which advocated the self-extrication of certain groups of casualties previously fully immobilised (Connor et al, 2012). Cowley (2014) has also highlighted at least three studies since 2013 that showed how self-extrication was associated with less movement of the C-spine. Ironically, it may appear that the main reason for using a KED (when C-spine stability is a priority) would in fact be the reason not to employ it, due to a paradoxical risk of greater spinal movement.
Minimal patient movement is not only a reasonable concept when considering a spinal injury, but is clearly imperative for those patients who may be bleeding. Blood loss through pelvic injury can be devastating and therefore minimising patient movement to maximise clot preservation in the early stages is essential (Clamp and Moran, 2007). It is not certain how the pressure transferred from the KED leg straps during casualty movement and lifting impact on pelvic stability. Additionally, once the patient is supine it is unclear how the optimal body position is affected from both a neurological (spinal alignment) and haemorrhagic (pelvic alignment) point of view. A well-practiced method of patient packaging once rescue has taken place with a rescue board involves the supine patient undergoing two very minimal lateral roles (to the left and right) facilitating simultaneous removal of cut clothing, insertion of a pelvic splint and the application of an orthopaedic stretcher. This ensures minimal patient movement and a packaged state that allows easy transfer onto an emergency department trolley. It further aids any rapid onward movement through to imaging and surgery without the need for subsequent log rolls and the risk of blood clot disruption or worsening pain. No official guidance was found surrounding the removal of the KED, ensuring minimal patient movement. However, one internet source advocated pulling the KED out from under the patient in a caudal direction, presumably once the patient is supine (Haworth, 2012).
Evidence
As well as reviewing product information, a literature search was undertaken using Academic Search Premier, CINAHL, Medline, Swetswise, Scopus and Cochrane Library databases to highlight evidence for the use of the KED with ‘Kendrick Extrication Device’ as the search term. No data relating to any clinical trials and the safety and efficacy of the device before it was marketed was found. Fourteen articles were found to include the KED and the main relative findings are summarised chronologically in Table 1.
| Author(s) | Date | Summary | |
|---|---|---|---|
| 1 | Graziano AF, Scheidel EA, Cline JR, Baer LJ | 1987 | Short board technique provides less lateral bending than the KED. 45 subjects. |
| 2 | Huerta C, Griffith R, Joyce SM | 1987 | Half spine board and collar was superior to the KED and collar in paediatric patients. Mannequin study. |
| 3 | Karbi OA, Caspari DA, Tator CH | 1988 | There is a lack of current evidence for the use of the KED. |
| 4 | Howell JM, Burrow R, Dumontier C, Hillyard A | 1989 | The KED ensured less rotation of the spine versus the short board technique but no benefit over flexion, extension and lateral bending. Seven male subjects. |
| 5 | Markenson D, Foltin G, Tunik M et al | 1999 | The KED is preferable to other adult immobilisation devices in paediatrics because children are able to ‘resist less’ or ‘free themselves’ with a KED applied. No study. |
| 6 | Calland V | 2005 | Use of the KED could reduce rotational movement and assist lifting of the casualty (no evidence cited). |
| 7 | Lee C, Porter K | 2007 | Opinion—possible use for the KED (inverted) in pelvic trauma. |
| 8 | Winterberger E, Jacomet H, Zafren K et al | 2008 | An official positional statement of two alpine mountain rescue agencies concerning vertical rescue from crevasses—no evidence or study cited. |
| 9 | Shafer J, Naunheim R | 2009 | Self-extrication with a collar led to less movement of the spine than the use of other devices (including the KED). |
| 10 | Ay D, Aktas C, Yesilyurt S, Sarıkaya S, Cetin A, Ozdogan ES | 2011 | Both the KED and spinal board (with straps) reduced pulmonary function in 60 healthy volunteers but the KED had a greater adverse impact on respiratory function than the spinal board. |
| 11 | Taneja T, Berry C, Rao R | 2012 | Main focus is on the initial hospital treatment of spinal injury but cites Karbi et el (1988) in advocating the KED over a short board and collar. |
| 12 | Engsberg JR, Standeven JW, Shurtleff TL, Eggars JL, Shafer JS, Naunheim RS | 2013 | Less cervical movement noted for patients who self-extricated unassisted with a cervical collar compared to being assisted (including assisted with a KED). |
| 13 | Pasquler M, Spichiger T, Ruffinen G | 2013 | Case report of a skier rescued and subsequent avocation of a winching method to control the tilt of a casualty while placed in a KED. |
| 14 | Bouland A, Jenkins J, Levy M | 2013 | Study looking at attitudes to extrication. Found a need for education in use of KED (as well as other findings). |
Most of the evidence available (spanning nearly three decades) focused on the range of spinal movement once the KED had been applied to volunteers or mannequins. None addressed the issue of patient movement during the application of the device. Following a study using mannequins, Howell et al (1989) concluded that rotational movement only was limited versus a short board and collar. However, four studies found other methods of extrication more effective than the KED with two published within the last decade (Shafer and Naunheim, 2009; Engsberg et al, 2013). Both of these more contemporary studies looked at the benefits of self-extrication over other methods.
Other articles did not cite any specific study and merely expressed an opinion. In a paper primarily focused on in-hospital treatment, Taneja et al (2012) cited an old proposal by Karbi et al (1988) that the KED may be better for immobilising patients over a short board and collar. However, Karbi et al (1988) highlighted a lack of evidence for KED use. Calland (2005) proposed its potential for reducing rotational movement, although no evidence is cited. The focus of articles by Winterberger et al (2008) and Pasquier et al (2013) was on the use of the KED in mountain rescue, but again the articles are opinion based. Lee and Porter (2007) saw a novel application for the device by placing it upside down to address potential pelvic trauma, while Markenson et al (1999) suggested its use for paediatric patients, almost as a restraint to stop them moving. A study by Bouland et al (2013) found the need for further education around KED use but did not look at benefits of using it.
From the evidence available, it is uncertain what region of the spine and what range of movements the KED is most effective at dealing with. Also, any additional benefits the KED has over a rescue board, cervical collar and orthopaedic stretcher is equivocal. No literature was found relating to any wider effects such as movement (bleeding) or tissue pressure and discomfort. However, a fairly recent article from Turkey involving 60 volunteers does evidence additional impaired respiratory function with KED use (Ay et al, 2011). However, none of the evidence looked at real patient outcomes, thus highlighting the need for further study.
Final thoughts
For the pre-hospital care provider, the KED may be one of several pieces of equipment available to assist in the management of trauma patients. However, no equipment should ever be applied in a default manner and without appreciation of its likely impact on the patient's condition, otherwise the potential exists to do more harm. We must avoid a formulaic approach to every trauma patient where we become overzealous about a possible C-spine injury at the expense of other crucial elements of management—an A to D problem, pain, exposure to the elements, rapid transport to definitive care or scene safety. Even in the presence of a likely spinal injury we should adopt the least complex and most familiar and timely methods of extrication, and avoid techniques with doubtful efficacy and with the potential to do harm.
With the real possibility of prolonging on scene time, increasing patient movement and impairing respiratory function, careful consideration should be given by practitioners to the application of a KED onto patients involved in trauma. Finally, in line with many recent articles examining the extrication and rescue of trauma patients, further ongoing study is required into this area, particularly concerning the use of devices.
Limitations
This article is largely written from an experiential perspective gained in two systems where practitioners are tasked primarily to critical care and major trauma. Although rationale is included, views and expressions will be subjective in parts. Despite a literature search, the articles found have not undergone a full systematic review and in this regard the article largely serves to highlight the lack of evidence around the KED.