How does AVPU work?
Conscious state is a fundamental part of the vital sign assessment. Unlike perfusion, there are no parameters that are directly measurable in an objective way. Rather, conscious state is assessed through interpretation of what is observed of the patient. These interpretations may be relatively obvious and universal or they may be subject to misinterpretation or subjective bias. To help combat this, different systems of conscious state assessment have been devised with the goal to create a guide that is easy to use and to be able to provide similar results no matter who the operator is applying it.
Consciousness is an important guide to how well the brain is functioning. This can provide clues to help assess the quality of perfusion and blood supply to the brain, hence other organs. Similarly information where the brain itself is injured, such as stroke or traumatic brain injury might also be obtained. Changes in consciousness can be a guide to both seriousness of any problem along with providing clues to deteriorations in condition. If recognised early, these clues can provide an early warning system.
As such, being able to assess and measure consciousness is important. The key criteria for being able to assess consciousness are that the method is easy to perform, various people can use it and achieve the same result and for it to be effective across a wide variety of problems and patient types including ages. The AVPU system is one tool to achieve this.
AVPU stands for the four levels of consciousness achievable using this system. Alert spontaneously, Verbal stimuli required to achieve response, Painful stimuli required to achieve response and finally Unresponsive to stimuli. These sound straightforward enough but to properly use the tool, in a standardised manner, a little understanding is required.
A ideally is where the patient is found with eyes purposefully open and in response to questioning, their answers are oriented and they can give a thumbs up when asked.
Importantly, it must be understood that if the patient is found with their eyes closed but from then on behaves as just described in A, then they still score that A also. Disturbing a patient who happens to have their eyes close to sleep or rest should not see them score lower. Being able to have spontaneous control of the eyes, speech and motor function scores A. The Alert patient can be calm, restless and agitated or even drowsy2.
However it gets interesting at the next level. There is one broad way to be scored V. This is the patient who requires verbal commands to continually provide any response, whether that be eye, verbal or motor. The verbal command should be a standard set of stimuli including to open the eyes, move limbs or to answer questions about person, time and place. V can also be the patient who provides confused or inappropriate responses to verbal command and questioning. This will be irrespective of whether they are found with their eyes open. This level is arguably the most difficult to assess using AVPU1.
Painful response is where painful stimuli, typically applied to the sternum, is required to illicit any response of the eyes, voice or motor function. It can be attributed to the patient who has no response to voice or being shaken and only opens their eyes after painful sternum pressure is applied. Alternatively, it can be applied to a patient who has their eyes open but in a fixed, non-purposeful stare, and shows groaning or limb movement to painful sternum pressure.
Finally, unresponsive is just that. There is no response from eyes, verbal or motor to any stimuli including painful sternum pressure.
Given that AVPU is less sophisticated than the GCS scale, it can be difficult to compare one to the other. Mind you, the lack of sophistication is not entirely a disadvantage. Assessing GCS is also highly subjective. Since it has more elements, there is greater scope for variation in interpretation.
Typically an AVPU result can be equated to a GCS range. Doing this is very imprecise and is not usually done in practice. This approach is more for appreciating roughly where any patient is in the GCS system when AVPU is used. Alert usually equates to GCS15. V usually equates to 12-14, P to 7-9 and U to 3. Because this comparison is imprecise, the missing scores in between can go either way up or down on the AVPU scale3. That is, V can be down to 7, P extend between 5-13 and U even extend up to 6. This approach has also been shown to be effective for children with A equating well to GCS15, V to a median of 12(10-13), P to a median of 8(7-10) and U to GCS of 3 with the greater overlap of range in the middle area between V and U5.
Conscious state becomes even more difficult in the child patient where there is the added subjective layer of interpretation of what is an appropriate response for the age of development. The younger the child, the less developed will be the responses. In particular, verbal understanding and responses are different though this is not without its problems with some adults too.
The AVPU system offers a means of partly getting around these differences. Instead of providing a specific response to a stimulus, such as voice, AVPU only asks the child to offer a response. The ranges for comparison between AVPU and GCS applies similarly to children as with adults. Some variation may be noted such as A being between 13 -15 to allow for variation in verbal and motor response interpretation4.
What is unarguable though is that AVPU represents a quicker and effective means of assessing conscious awareness than GCS in smaller children, particularly infants and babies4,5.
Jeff Kenneally www.prehemt.com
- Brunker C, Harris R. How accurate is the AVPU scale in detecting neurological impairment when used by general ward nurses? An evaluation study using simulation and a questionnaire. Intensive and Critical Care Nursing. 2015 Apr 30;31(2):69-75
- Rajabi Kheirabadi A, Tabeshpour J, Afshari R. Comparison of Three Consciousness Assessment Scales in Poisoned Patients and Recommendation of a New Scale: AVPU Plus. Asia Pacific Journal of Medical Toxicology. 2015 Jun 20;4(2):58-63
- Kelly CA, Upex A, Bateman DN. Comparison of consciousness level assessment in the poisoned patient using the alert/verbal/painful/unresponsive scale and the Glasgow Coma Scale. Annals of emergency medicine. 2004 Aug 31;44(2):108-113
- Rao KS, Srinivas P, Swathi V. Comparison of Avpu with Glasgow Coma Scale for Assessing Level of Consciousness in Infants and Children. IOSR Journal of Dental and Medical Sciences (IOSR-JDMS).;1(14):22-29
- Hoffmann F, Schmalhofer M, Lehner M, Zimatschek S, Grote V, Reiter K. Comparison of the AVPU Scale and the Pediatric GCS in Prehospital Setting. Prehospital Emergency Care. 2016 Mar 3:1-5