Comparison of Neurological Assessment Tools
An assessment of the level of consciousness (LOC) should be carried out during the primary survey of all patients, using the ABCDE approach Cole (2009: 28). Any initial or subsequent reduction in the LOC of the patient may be caused by hypoxia; hypovolaemia; head injury; drug or medicine use; hypoglycaemia; hypothermia or alcohol ingestion (Cole, 2009:44). An assessment of the LOC of the patient is vital for an accurate pain assessment and the administration of analgesia, and the subsequent assessment of its efficacy (Rose, et al. 2011). Regular evaluation of a patient’s LOC helps detect the onset of hypothermia and hypovolaemia.
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Muehlberger, et al. (2010) state that the development of pre-hospital hypothermia is a directly negative prognostic factor for burns patients. The inclusion of LOC assessment for burns patients seems to be a recent development however, neither Allison & Porter (2004) nor Allison (2002) refer in any way to assessing a patient’s LOC in their work on standardising a pre-hospital approach to burns patient management. A coma scale is a defined methodology by which neurological observations can be recorded in a standardised way by clinicians (Coyne, et al. 010). Many different scales have been developed in an attempt to standardise the assessment of consciousness (Majerus, 2005). In this essay I will discuss three main coma scales and examine their strengths and weaknesses. I will also briefly discuss a number of revisions to these scales. Glasgow coma scale (GCS) and variations The GCS is the most commonly used coma scale in the acute setting (Majerus, 2005) and its use is recommended by the National Institute for Health and Clinical Excellence (NICE, 2007).
The scale was devised by Teasdale & Jennett based on their work in the neurosurgery department at the University of Glasgow. Their scale allows a clinician with minimal training to perform three basic assessments measuring the eye, verbal and motor responses against a set of criteria. The results for the three components are commonly totalled together to indicate the patient’s GCS ranging from 3 to 15, although the authors’ intent was that the three elements should be expressed separately (Teasdale, et al. 1983). However, while the GCS works well for patients who can verbalise, typically over the age of five years, it has been found to be less effective at assessing younger children and infants (Coyne, 2010). Developmental changes and choosing not to speak, versus inability to speak, led to scores that were more subjective and prone to misinterpretation (Matis, 2008). To address this the scale was modified for use with children, this revision is known as the Paediatric Glasgow Coma Scale (PGCS) (Morray, et al. 1984).
Teasdale & Jennett tested the reliability of their scale when performed by different categories of clinician. The authors were confident that all assessors with the same basic training were able to score patients with a high degree of consistency. Subsequent analysis confirmed that only inexperienced or untrained staff produced inconsistent results (Rowley & Fielding, 1991). McNarry & Goldhill (2004) however, assert that a greater degree of skill is required to achieve consistency in scoring. While Kelly, et al. 2004) questioned the reliability of interrater scoring, finding that GCS scores calculated by clinicians only agreed in only 32% of cases. A number of limitations were identified by Teasdale & Jennett themselves and relate to when elements of the scale are untestable, for example fractured or splinted limbs prevent mobilisation; a tracheotomy may prevent speech; or localised swelling or paralysis may make eye opening impossible. Thirty years later Kelly, et al. (2004) concluded that the GCS was too complex for assessing intoxicated or uncooperative patients.
They found that the verbal component was the main difficulty in determining an accurate GCS score. Alcohol intoxicated patients were often uncooperative, refused to speak, or had slurred incoherent speech. Staff assessing these patients found themselves recording GCS scores lower than what they felt was appropriate. Since the GCS became widely adopted and its use became expanded beyond the original intention of the scale, certain additional limitations have been identified (Laureys, 2005). Verbal responses become difficult or impossible to assess when patients have been sedated or intubated (Majerus, 2005).
Some clinicians feel that scoring eye opening is not sufficient to indicate brainstem arousal and a number of coma scales have been proposed that include brainstem reflexes, most of them more complex than the GCS scale (Majerus, 2005). The Glasgow Liege scale is the simplest variation proposed (Born, et al. , 1982). It combines the GCS with five brainstem reflexes, but has not been widely implemented outside Belgium, its country of origin (Laureys, 2005). Finally, the remaining weaknesses of the GCS scale relate to the assessment of comatose patients.
The GCS becomes unreliable in ongoing care for monitoring coma and recovery through vegetative or minimally conscious states, before returning to consciousness (Laureys, 2005). The main advantage of the GCS is its simplicity, allowing it to be utilised by the full range of clinicians, with a minimal amount of training (Matis, 2008). Rapid Assessment Tools (AVPU and ACDU) More recently, early warning systems have been developed in an effort to recognise the at-risk patient who may be deteriorating while in hospital care.
This effort has in turn driven the development of a number of rapid assessment tools (Palmer & Knight, 2006). One such rapid assessment tool is the AVPU scale, which consists of four basic categories: A for Alert; V for a patient who responds only to voice; P for a patient who responds only to pain; or U for a patient that is unresponsive to all stimuli (Palmer & Knight, 2006). During time-critical incidents the AVPU scale may be more appropriate to use as an alternative to the GCS as it allows for an immediate and rapid assessment of a patient’s neurological state (Coyne, 2010).
Although no relationship between GCS and AVPU scores has been defined, McNarry & Goldhill (2004) suggest that a GCS of 13 is the dividing point between alert and responsive to voice, while a GCS of 9 was the dividing point between responsive to voice and responsive to pain. They also point out that, while AVPU appears simpler to use, in practice it may not be able to identify subtle changes in consciousness. Kelly, et al. (2004) agreed that nursing staff found the AVPU scale easier to use than GCS for rapid assessments, but still found a degree of difficulty assessing alcohol-intoxicated patients.
The authors also felt that, due to the lack of guidance provided to clinicians on exactly how to use the AVPU tool, it was still difficult to achieve a high level of consistency in recording. McNarry & Goldhill (2004) suggest an alternative tool: the alert, confused, drowsy, unresponsive (ACDU) scale as a variation to the AVPU scale. Their research found that nurses preferred to use AVPU when the GCS was lower, while ACDU was preferred when the GCS was higher.
McNarry & Goldhill concluded that the ‘Confused’ and ‘Drowsy’ categories in the ACDU scale provided an improved distinction in the midrange of GCS assessments than the ‘responds to Voice’ and ‘responds to Pain’ categories offered by AVPU. The authors felt that the ACDU tool was better suited to rapid simple ward assessment of seriously ill patients than AVPU, and fitted better into early warning systems. However, the authors were clear to point out that none of the rapid assessment scores should replace GCS for the formal evaluation of a critically ill patient and that a GCS assessment should be performed secondary to AVPU or ACDU.
Full Outline of Unresponsiveness (FOUR) score The need to incorporate an assessment of brainstem reflexes into a coma scale, particularly for patients in a comatose state, led Wiejdicks et al. (2005) to propose the FOUR score. This scoring system includes four components (eye, motor, brainstem and respiratory functions) each rated with a maximum score of four. The voice component of GCS has been removed and the eye component modified to include an assessment of eye movement, which the authors claim, will facilitate the early detection of locked-in syndrome.
The brainstem and respiratory components facilitate the detection of changes in comatose and intubated patients, such as the transition from a vegetative to a minimally conscious one (Laureys, 2005). An analysis of the scores calculated by clinicians using the FOUR scale in an intensive care environment by Iyer, et al. (2009) found greatly improved consistency in contrast to the GCS, and confirmed that all components of the FOUR score can be rated even when patients have been intubated.
When compared to the Glasgow Liege scale researchers confirmed that the FOUR score was an improvement as it could be performed on intubated patients and was able to identify nonverbal signs of consciousness by assessing eye movement (Bruno, et al. 2011). Since it’s publication in 2005, most of the validation of the FOUR tool has been done by one institute. Some are cautious about single-centre trials and further assessment is required before the FOUR score can be more widely endorsed and utilised (Kornbluth & Bhardwaj, 2011). Conclusion
In the assessment of the patients in this specific case study it would be appropriate to use a rapid assessment tool such as AVPU initially, so that other assessments and therapeutic interventions are not delayed, and then complete a GCS assessment at the earliest possible opportunity, as described by Rawlins (2011). Utilisation of the PGCS scale would be appropriate for the child, as recommended by Wilson & McCormack (2012) In the past 30 years, many coma scales have been proposed as an alternative to the Glasgow coma scale, but none with success (Laureys, 2005).
Coma scales such as the FOUR score address the shortcomings of the GCS in specific environments, such as the care and monitoring of comatose patients in intensive care units, but their usefulness seems limited in the acute setting and without specific training (Majerus, 2005). Whichever scale is chosen, it should be used at regular intervals and in a consistent way by all clinicians to detect changes in consciousness (Ward, 1996).