Pain point system scale (PPSS): a method for postoperative pain estimation in retrospective studies

Figures & data

Table 1 Scoring algorithm of pain point system scale based on administered drugs in the early postoperative period

Drug	PPSS score (points/dose)
Paracetamol (acetaminophen) 600 mg	1
Paracetamol 500 mg + codeine 10 mg	3
NSAIDs	3
Diclofenac 75 mg
Parecoxib 40 mg
Lornoxicam 8 mg
Opioids	7
Tramadol 50 mg
Dextropropoxyphene hydrochloride 75 mg
Pethidine hydrochloride 50 mg

Abbreviations: NSAIDs, nonsteroidal antiinflammatory drugs; PPSS, pain point system scale.

Table 2 Demographic and baseline characteristics of the patient groups

	First group: local infiltration anesthesia	Second group: spinal anesthesia	Third group: general anesthesia
Patient data
Number	12	70	42
Sex
Male	12	52	34
Female	0	18	8
Age (years)
Mean ± SD	59.25 ± 5.3	65.0 ± 12.1	54.89 ± 17.9
Median (range)	54 (22–84)	66 (19–86)	56 (18–81)
BMI (kg/m^2)
Mean ± SD	27.58 ± 3.8	26.18 ± 3.7	25.17 ± 3.8
Education level, n (%)
Elementary school	5 (41.66)	36 (51.43)	12 (28.57)
High school	5 (41.66)	25 (35.71)	23 (54.76)
University	2 (16.66)	9 (12.86)	7 (16.66)
Perioperative data
Operation (n)	Circumcision (7)	TUR-P (24)	Varicocelectomy (13)
	Hydrocelectomy (5)	TUR-BT (16)	Radical prostatectomy (13)
		URS (16)	Radical nephrectomy (12)
		Open prostatectomy (10) MUS (4)	Radical cystectomy and bricker diversion (4)
Mean operation time ± SD (minutes)	32.58 ± 7.3	44.37 ± 19.9	116.63 ± 62.4
Range (minutes)	19–43	11–110	26–290
Estimation of blood loss (g/dL)a
Mean ± SD	0.93 ± 0.65	2.75 ± 1.4	2.8 ± 1.85
Range	0.2–2.5	0.1–6.7	0.2–6.9

Note:

a Difference in hemoglobin level pre- and postoperatively.

Abbreviations: BMI, body mass index; MUS, midurethral sling; SD, standard deviation; TUR-BT, transurethral excision of bladder tumor; TUR-P, transurethral prostatectomy; URS, ureteroscopic lithotripsy.

Figure 1 The artificial neural network schema shows the factors affecting the decision for specific drug administration.

Notes: The first column shows all the factors (predictive covariates) that influence drug administration (input nodes). Output A nodes represent the three major analgesic categories according to the World Health Organization’s “analgesic ladder.” Output B represents the final decision (developed using MATLAB R2009B; The MathWorks, Inc, Natick, MA).
Abbreviations: NRS, numerical rating scale; VAS, visual analog scale; VRS, visual rating scale.

Figure 2 Cattell scree plot for factor determination and evaluation of the proper scoring system.

Table 3 Comparison of the treatment efficacy after intravenous administration of analgesics across the three pain scales

	First group: local infiltration anesthesia	Second group: spinal anesthesia	Third group: general anesthesia
Total pain episodes	22	138	102
Pain episodes per patient	1.92	1.98	2.43
Visual analog scale
Mean pretreatment value per patient	138.34	126.57	208.07
Mean posttreatment value per patient	24.9	36.2	40.2
Treatment efficacy	82.0%	71.4%	80.7%
	Mean treatment efficacy value 78.03%
Numerical rating scale
Mean pretreatment value per patient	11.36	12.75	20.38
Mean posttreatment value per patient	1.77	6.29	5.92
Treatment efficacy	84.4%	50.7%	70.9%
	Mean treatment efficacy value 68.67%
Verbal rating scale
Mean pretreatment value per patient	3.67	3.78	5.98
Mean posttreatment value per patient	0.98	1.54	2.59
Treatment efficacy	73.3%	59.3%	56.6%
	Mean treatment efficacy value 63.07%

Figure 3 The relationship between the visual analog scale and the proposed pain point system scale, showing linear and strong correlation.

Table 4 Multiple regression analysis for sex, age, body mass index, educational level, operation duration, and reduction in hemoglobin level

VAS	NRS	PPSS	Sex	Age	BMI	Education level	Operation duration	Hemoglobin reduction
1	0.851**	0.631**	0.005	0.051	0.221**	0.052	0.398**	0.342**
P-value	0.000	0.000	0.937	0.415	0.000	0.403	0.000	0.000

Notes:

** No significance; VAS pain scale used as the independent variable.

Abbreviations: BMI, body mass index; NRS, numerical rating scale; PPSS, pain point system scale; VAS, visual analog scale.

Table 5 Pearson’s and Spearman’s rho correlations in the three studied groups

	First group: local infiltration anesthesia			Second group: spinal anesthesia			Third group: general anesthesia
	VAS	NRS	PPSS	VAS	NRS	PPSS	VAS	NRS	PPSS
Pearson’s correlation to VAS	1.000	0.971	0.847	1.000	0.628	0.620	1.000	0.702	0.502
Significance (2-tailed)	–	0.001	0.001	–	0.001	0.001	–	0.001	0.001
n	22	22	22	138	138	138	102	102	102
Spearman’s rho correlation to VAS	1.000	0.960	0.828	1.000	0.564	0.602	1.000	0.792	0.634
Significance (2-tailed)	–	0.001	0.001	–	0.001	0.001	–	0.001	0.001
n	22	22	22	138	138	138	102	102	102

Abbreviations: NRS, numerical rating scale; PPSS, pain point system scale; VAS, visual analog scale.