Gate control theory/pain gate mechanism According to the gate control theory, sensations such as pain that are perceived by the receptors have to be traversed through a control system, or gate, so all the sensations do not reach the brain – only the selected ones. This gate is located in the dorsal horn of the spinal cord. The fibers carrying pain (small fibers) and non-painful stimuli (large fibers) synapse either in the substantia gelatinosa or in the dorsal column, which are the specified areas
in the dorsal horn working as the pain gate. [13][14] The gate opens and permits the sensations transmitted by the small fibers (A δ and C fibers); whereas it inhibits the afferents by the large fibers (A β fibers). When the gate is opened, the transmission cells convey the sensory information to the higher centers of brain, which is when an individual experiences pain. This theory has solved many issues when treating pain in patients, especially when introducing drugs to manage pain. Visual Analog Scale (VAS) The Visual Analog Scale is a 100 mm line. The left end is marked as 0, which indicates “No pain,” and the right end is marked as 10, which denotes “Severe pain”. Refer to Figure 3 for more clari- fication in marking the VAS. The patient is asked to mark the level of pain he/she perceives on the straight line [15] . This scale is useful for adolescents and adults. Figure 3: The Visual Analog Scale Note. Image adapted from: http://www.health.gov.au/internet/main/ publishing.nsf/Content/387970CE723E2BD8CA257BF0001DC49F/$F ile/Triage%20Quick%20Reference%20Guide.pdf Abbey Pain Scale The Abbey Pain Scale can be used for the patients who cannot speak and/or comprehend. The healthcare professional has to ob- serve the person and fill in the boxes appropriately (as shown in Figure 4) [15] . On completion of the questions, Total Pain Score has to be obtained by adding the scores of all six questions. The scoring system is: 0 - 2 No pain 8 - 13 Moderate
MEASURING PAIN
As pain is an emotional sensation, it is hard to measure. But, there are scales to measure the severity and intensity of pain perceived by patients such as self-reported pain scales, which are more com- mon than observational (behavioral), or physiological pain scales, which are easy to comprehend and administer. There are specific pain scales for newborns, infants, children, and adults. See Figure 2 for some of the pain scales that are frequently used. Wong Baker FACES Wong Baker FACES Pain Rating Scale is ideal for children (older than 3 years) and adolescents as it consists of graphical illustra- tions of faces. Each facial expression demonstrates the severity of the pain. The scoring system ranges from 0 (no pain at all) to 5 (most severe pain )[15] . Figure 2: Wong Baker FACES Pain Rating Scale
Note . Image adapted from: http://www.health.gov.au/internet/main/ publishing.nsf/Content/387970CE723E2BD8CA257BF0001DC49F/$F ile/Triage%20Quick%20Reference%20Guide.pdf
3 - 7 Mild
14+ Severe
Figure 4: Abbey Pain Scale How to Use Scale: While observing the patient, score questions 1 to 6. Q1. VOCALISATION eg: whimpering, groaning, crying Absent 0 Mild 1
Q1 Q2
Moderate 2
Severe 3
Q2. FACIAL EXPRESSION eg: looking tense, frowning grimacing, looking frightened Q3. CHANGE IN BODY LANGUAGE eg: fidgeting, rocking, guarding part of body, withdrawn Q4. BEHAVIORAL CHANGE eg: increased confusion, refusing to eat, alteration in unusual patterns Q5. PHYSIOLOGICAL CHANGE eg: temperature, pulse or blood pressure outside of normal limits, perspiring Q6. PHYSICAL CHANGES eg: skin tears, pressure areas, arthritis, contractures, previous injuries
Absent 0 Mild 1
Moderate 2
Severe 3
Q3
Absent 0 Mild 1
Moderate 2
Severe 3
Q4
Absent 0 Mild 1
Moderate 2
Severe 3
Q5
Absent 0 Mild 1
Moderate 2
Severe 3
Q6
Absent 0 Mild 1
Moderate 2
Severe 3
Add scores for 1 - 6 and record here Total Pain Score Note. Image adapted from: http://www.health.gov.au/internet/main/publishing.nsf/Content/387970CE723E2BD8CA257BF0001DC49F/$File/ Triage%20Quick%20Reference%20Guide.pdf Face, Legs, Activity, Cry, Consolability (FLACC) Scale
The scoring system for this behavioral scale is: 0 Relaxed and comfortable 4-6
The FLACC Scale (see Figure 5) can be used for infants 2 months or more. It is also considered to be a gold standard of measuring pain in intubated patients in intensive care units. The healthcare professional should observe the patient with legs and body ad- equately exposed for about 2 to 5 minutes or more, then ask the patient to perform a movement if he/she is awake (or else reposi- tion the patient)to assess the apprehension (i.e., tenseness) and tone of the body [15] . Consoling interventions can be started after this test if the patient is compliant.
Moderate pain
1-3 Mild discomfort
7-10 Severe discomfort/pain
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