My opinion

By Dr. Deepak Gupta
Corresponding Author Dr. Deepak Gupta
Wayne State University, - United States of America 48201
Submitting Author Dr. Deepak Gupta

VAS, PCA, Acute Pain, Acute on Chronic Pain, Pain Management, Visual Analogue Scale, Patient-Controlled Analgesia

Gupta D. Visual Analogue Scale Specific Patient-Controlled Analgesia (VAS Guided PCA). WebmedCentral PAIN 2013;4(3):WMC004126
doi: 10.9754/journal.wmc.2013.004126

This is an open-access article distributed under the terms of the Creative Commons Attribution License(CC-BY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Submitted on: 12 Mar 2013 04:36:19 AM GMT
Published on: 12 Mar 2013 06:48:12 AM GMT

My opinion

As an anesthesia provider, we are responsible for ensuring adequate perioperative analgesia. One of the pain management modality that is frequently used in perioperative settings is patient-controlled analgesia (PCA) for the parenteral opioids [1]. Since the famous presidential address of James Campbell (1996) to the American Pain Society [2], pain has come a long way as an established fifth vital sign [3]. With aggressive policies at diagnosing, documenting and managing pain of the patients, PCA has become an important modality that is utilized more than often beyond the realms of perioperative settings. The application of PCA is no longer limited to acute perioperative pain; but it includes management of difficult-to-intractable acute pain in chronic pain patients who are admitted for inpatient management of pain-related or pain-unrelated symptoms. The most common pain assessment tool used in adult patient population is visual analogue scale (VAS) [4-6] that is available primarily in two forms: 0-100 mm scale and 0-10 Numerical Rating Scale (NRS). Their sensitivity to assess pain are approximately equal [7] and NRS is apparently more popular due to patient’s ease in reporting 0-10 VASscores.

The currently available versions of PCA deliver a-predetermined intravenous dose of opioids (as appropriately adjudged by the ordering physician) on patient’s decided dosing interval: the interval can be as low as every 6 minutes (the lockout interval). The current versions of PCA are not equipped to record the actual VAS scores because each time the patient feels pain requiring medication, irrespective of the VAS scores the patient pushes the same single-button mechanism (Figure 1) to deliver the same predetermined dose as fed in the PCA’s software. In my opinion, it is time that single-button PCA should be replaced with a 1-10 numbered-remote PCA (Figure 1). The lowest score of VAS ‘0’ in NRS scale may not be needed in this remote because VAS score ‘0’ may not prompt the patient to push the number on the remote as patient is not expecting any pain medication relief for VAS score=0. The patients will get this remote and push the number on the remote corresponding to their VAS scores. Consequently, the PCA’s software will deliverVAS-specific variable doses (including zero dose for low non-zero VAS scores) as pre-determined by the ordering and the inputting physician. To avoid inadvertent pushing of the remote's numbers, the remote will have a hard transparent plastic cover that will be lifted by the patient each time he/she will need to activate PCA for VAS-specific dose. The major advantages of this improvisation will be that

(a) In comparison to single-button PCA, the patient will have to be more alert as well as oriented to push the correct number on numbered-remote PCA for VASscores
(b) The PCA’s software database will have the VAS scores recorded over times as recording of VAS will be possible at all the time; however the demands (as recorded in current versions of PCA) will be attributed to those instances when VAS-specific dose per PCA software will not be delivered due to the lockout interval
(c) The patient will not have to worry about reporting VAS scores as well as requesting medications separately
(d) The physicians will have option to input VAS-guided doses in the PCA’s software
(e) The physicians will have option to run a 'Sham PCA' wherein the patients will be counseled to use the numbered-remote PCA only for regular recording of VAS scores; and the medications (in form of IV PUSH or oral doses) will be administered by the nursing staff.

This VAS-specific PCA model is not a new innovation but an improvisation of old school of pain medicine and imbibing into the PCA-based analgesia regimens wherein the patient controls his/her pain reporting and consequently appropriate analgesic administration. The physicians ordering pain medication as a range of dose as well as a range of dosing interval (e.g. morphine 1-2mg IV every 2-4 hours) was a common place till recently when patient safety regulatory entities recently curtailed this practice to avoid medication error and overdosing [8-9]. However, the regulatory entities allow the medication dose range orders [10] if the corresponding pain assessment tool range is also included with clear cut instructions about withholding medications depending on patient’s status and other vital signs (e.g. morphine 1-2 mg IV every 2-4 hours; 1mg for VAS scores 4-6, 2mg for VAS scores 7-10, decide dosing interval keeping Modified Ramsay Sedation Score ≥3) [11]. These range orders have not been limited for use of intravenous medications but pain physicians have used these range orders for oral opioids with similarly clear cut directions of administration by the nursing staff.

The few cautions that will be needed for this numbered-remote PCA to succeed are that instead of wireless remotes, cables with predetermined lengths will be required so that remote-PCA by proxy can be avoided. Additionally, the wireless remotes will potentially increase the electromagnetic pollution/interference in the patient’s room. Moreover, the cables will ensure the continued safety against lost/misplaced/far-placed remotes in case the patient emergently needs to press for VAS-specific number to self-administer medication. The major incentive for patients will be that they will crowd and vouch for the hospitals that have more comprehensive pain scores databases as extracted from these VAS-specific PCA’s software. The aims of the catering hospitals will be to keep these pain scores graphs (areas under line-curve) under a minimum efficacious numbers as determined by their site-specific and general population validation studies. These target areas under curves will be different for acute pain patients, and acute on chronic pain patients. These areas under line-curve will be determined as following [12]: the ‘area’ above the average values minus the ‘area’ below the average values wherein the "area" above the average values is the sum of (valuen - average) where valuen are the values that are greater than average value and the "area" below the average values is the sum of (average - valuen) where valuen are the values that are lower than average value.

Let us consider this example based on 10 random numbered VAS score generated from  [13]. Random VAS numbers: 10, 9, 4, 7, 6, 1, 2,1,1,1. ‘Area’ above average (Average VAS for these ten numbers=4): Sum (2, 3, 5, 6)=16. ‘Area’ below average: Sum (3, 3, 3, 3, 2)=14. Thus the final ‘area’ under the line-curve is 2. Even though this example calculated average VAS based on the random ten numbers, the hospitals can decide to universally consider average and acceptable VAS=5 that can then used as a cut off to decide about the ‘area’ aboveVAS=5 and ‘area’ below VAS=5. The other method of ‘area under line-curve’ called ‘TRAPEZOID RULE’ [14] cannot be used as the time difference between the two recorded VAS in the numbered-remote PCA will not be uniformly spaced and often times VAS scores will be zero that the patient will not be inputting in the software. These discontinuities and sporadic reporting ofVAS in the PCA database will interfere with the ‘TRAPEZOID RULE’ based assessment of ‘area under line-curve’.

In summary, it is high time to have this innovation in pre-existing PCA models so that clinical trials can be initiated for the validity of this scenario because in my opinion, it is worth a transition for correct VAS scores database and corresponding medication use with patient-controlled analgesia regimens.


1. Grass JA. Patient-controlled analgesia. Anesth Analg. 2005 Nov;101(5 Suppl):S44-61.
2. American Pain Society. Principles of Analgesic Use in the Treatment of Acute Pain and Cancer Pain. 4th ed.Glenview,IL: American Pain Society; 1999.
3. Last accessed onMarch 11, 2013.
4. Carlsson AM. Assessment of chronic pain. I. Aspects of the reliability and validity of the visual analogue scale. Pain. 1983 May;16(1):87-101.
5. Price DD, McGrath PA, Rafii A, Buckingham B. The validation of visual analogue scales as ratio scale measures for chronic and experimental pain. Pain. 1983 Sep;17(1):45-56.
6. Price DD, Patel R, Robinson ME, Staud R. Characteristics of electronic visual analogue and numerical scales for ratings of experimental pain in healthy subjects and fibromyalgia patients. Pain. 2008 Nov 15;140(1):158-66.
7. Breivik EK,BjörnssonGA, Skovlund E. A comparison of pain rating scales by sampling from clinical trial data. Clin J Pain. 2000 Mar;16(1):22-8.
8. Gordon DB, Dahl J, Phillips P, Frandsen J, Cowley C, Foster RL, Fine PG, Miaskowski C, Fishman S, Finley RS; American Society for Pain Management Nursing; American Pain Society. The use of 'as-needed' range orders for opioid analgesics in the management of acute pain: a consensus statement of the American Society for Pain Management Nursing and the American Pain Society. Home Healthc Nurse. 2005 Jun;23(6):388-98.
9. Gordon DB, Dahl J, Phillips P, Frandsen J, Cowley C, Foster RL, Fine PG, Miaskowski C, Fishman S, Finley RS; American Society for Pain Management Nursing, American Pain Society. The use of "as-needed" range orders for opioid analgesics in the management of acute pain: a consensus statement of the American Society for Pain Management Nursing and the American Pain Society. Pain Manag Nurs. 2004 Jun;5(2):53-8.
10. Last accessed onMarch 11, 2013.
11. Last accessed onMarch 11, 2013.
12. Last accessed onMarch 11, 2013.
13. Last accessed onMarch 11, 2013.
14.  Last accessed onMarch 11, 2013.

Source(s) of Funding


Competing Interests



This article has been downloaded from WebmedCentral. With our unique author driven post publication peer review, contents posted on this web portal do not undergo any prepublication peer or editorial review. It is completely the responsibility of the authors to ensure not only scientific and ethical standards of the manuscript but also its grammatical accuracy. Authors must ensure that they obtain all the necessary permissions before submitting any information that requires obtaining a consent or approval from a third party. Authors should also ensure not to submit any information which they do not have the copyright of or of which they have transferred the copyrights to a third party.
Contents on WebmedCentral are purely for biomedical researchers and scientists. They are not meant to cater to the needs of an individual patient. The web portal or any content(s) therein is neither designed to support, nor replace, the relationship that exists between a patient/site visitor and his/her physician. Your use of the WebmedCentral site and its contents is entirely at your own risk. We do not take any responsibility for any harm that you may suffer or inflict on a third person by following the contents of this website.

3 reviews posted so far

Visual Analogue Scale Specific Patient-Controlled Analgesia
Posted by Dr. William J Maloney on 11 Feb 2014 04:28:15 PM GMT Reviewed by Interested Peers

2 comments posted so far

Apparently Safer and Futuristic VAS Guided PCA Posted by Dr. Deepak Gupta on 17 Mar 2013 05:16:13 PM GMT

Please use this functionality to flag objectionable, inappropriate, inaccurate, and offensive content to WebmedCentral Team and the authors.


Author Comments
0 comments posted so far


What is article Popularity?

Article popularity is calculated by considering the scores: age of the article
Popularity = (P - 1) / (T + 2)^1.5
P : points is the sum of individual scores, which includes article Views, Downloads, Reviews, Comments and their weightage

Scores   Weightage
Views Points X 1
Download Points X 2
Comment Points X 5
Review Points X 10
Points= sum(Views Points + Download Points + Comment Points + Review Points)
T : time since submission in hours.
P is subtracted by 1 to negate submitter's vote.
Age factor is (time since submission in hours plus two) to the power of 1.5.factor.

How Article Quality Works?

For each article Authors/Readers, Reviewers and WMC Editors can review/rate the articles. These ratings are used to determine Feedback Scores.

In most cases, article receive ratings in the range of 0 to 10. We calculate average of all the ratings and consider it as article quality.

Quality=Average(Authors/Readers Ratings + Reviewers Ratings + WMC Editor Ratings)