Prediction of Postoperative Pain and Opioid Consumption Using Intraoperative Surgical Pleth Index After Surgical Incision: An Observational Study

Figures & data

Figure 1 Flow diagram of patient selection and study protocol.

Table 1 Demographic and Surgical Characteristics

	Group L (n=17)	Group H (n=29)	P value
Age, yr	64 (8)	59 (11)	0.095
Gender, female	5 (29%)	9 (31%)	0.418
Height, cm	163.6 (6.6)	163.6 (7.3)	0.970
Weight, kg	67.2 (8.2)	68.0 (12.4)	0.834
Diabetes mellitus	7 (41%)	6 (21%)	0.136
Hypertension	8 (47%)	11 (38%)	0.322
BMI, kg/m^2	25.0 (2.3)	24.3 (3.8)	0.778
Surgery Total gastrectomy Subtotal gastrectomy	5 (31%) 11 (69%)	11 (37%) 19 (63%)	0.475
Duration of surgery	113 [103, 125]	131 [104, 148]	0.247
Fentanyl use during surgery	1 (6%)	1 (3%)	0.608
Atropine/Ephedrine during surgery	7 (41%)	14 (48%)	0.641
Hydromorphone during closure	0.6 [0.5, 0.7]	0.6 [0.6, 0.7]	0.914
Questionnaires Expected pain (Above average) Preoperative anxiety (Above average) Expected analgesics (Above average) Preoperative pain (Yes)	6 (26%) 6 (26%) 1 (4%) 4 (17%)	4 (17%) 4 (17%) 6 (26%) 1 (4%)	0.722 0.722 0.096 0.346

Note: Data are expressed as number (%), median [IQR], or mean (SD).

Figure 2 The trend for SPI values throughout the perioperative period in both groups. (Time 1: Pre-induction, 2: Pre-incision, 3: Post-incision, 4: 1 h after incision, 5: before arousal, Bispectral index < 60).

Table 2 Pre-Induction, Pre-Incision and Post-Incisional Surgical Pleth Index, Blood Pressure, Heart Rate, and Bispectral Index

Pre-Induction	Group L (n=17)	Group H (n=29)	P value
Surgical pleth index	51 (20)	56 (16)	0.326
Systolic blood pressure, mmHg	151 (25)	144 (21)	0.283
Diastolic blood pressure, mmHg	80 (16)	80 (14)	0.913
Mean blood pressure, mmHg	95 (14)	96 (12)	0.984
Heart rate, beats/min	73 (16)	72 (11)	0.897
Pre-Incision	Group L (n=17)	Group H (n=29)	P value
Surgical pleth index	29 (7)	36 (10)	0.008
Bispectral index	37 (8)	39 (5)	0.442
Systolic blood pressure, mmHg	109 (15)	105 (18)	0.438
Diastolic blood pressure, mmHg	71 (12)	69 (12)	0.234
Mean blood pressure, mmHg	81 (11)	77 (12)	0.262
Heart rate, beats/min	70 (11)	71 (14)	0.767
Post-Incision	Group L (n=17)	Group H (n=29)	P value
Surgical pleth index	45 (7)	63 (8)	<0.001
Bispectral index	37 (7)	38 (7)	0.500
Systolic blood pressure, mmHg	142 (19)	142 (21)	0.761
Diastolic blood pressure, mmHg	90 (19)	93 (14)	0.299
Mean blood pressure, mmHg	103 (16)	105 (14)	0.604
Heart rate, beats/min	92 (20)	96 (17)	0.534

Note: Data are expressed as mean (SD).

Figure 3 Receiver operating characteristics for SPI during surgery to distinguish different states of postoperative fentanyl consumption (≥1000 μg, 25% quantile of high opioid consumption).

Table 3 The Brief Interview for Assessing Preoperative Anxiety and Psychological Status

Expected Pain	Above Average (n=10)	Below Average (n=36)	P value
SPI, awake	49 (23)	55 (17)	0.384
SPI, post-incision	52 (7)	58(13)	0.185
∆SPI, during incision	25 (10)	24 (13)	0.786
Preoperative Anxiety	Above Average (n=10)	Below Average (n=36)	P value
SPI, awake	44 (16)	56 (17)	0.058
SPI, post-incision	56 (12)	56(12)	0.994
∆SPI, during incision	26 (11)	24 (11)	0.619
Expected Analgesics	Above Average (n=7)	Below Average (n=39)	P value
SPI, awake	56 (18)	53 (18)	0.994
SPI, post-incision	65(11)	55 (11)	0.029
∆SPI, during incision	30 (9)	23 (12)	0.122
Preoperative pain	Yes (n=5)	No (n=41)	P value
SPI, awake	68 (10)	52 (17)	0.038
SPI, post-incision	52 (6)	57 (12)	0.185
∆SPI, during incision	26 (10)	24 (12)	0.698

Note: Data are expressed as mean (SD).

Abbreviations: SPI, surgical pleth index; ∆SPI, the change of pre-incision and post-incision SPI value to surgical incision.