Table 2 Factors associated with amount of opioid requirement in postanesthesia care unit as indicated by the directed acyclic graph (N = 3316)

Sex

-

Male

1

1

1

<  0.001*

Female

1.36 (1.17, 1.59)

1.00 (0.80, 1.25)

0.73 (0.58, 0.93)

Age

-

< 65 years old

1

1

1

0.09

≥ 65 years old

0.82 (0.69, 0.99)

1.00 (0.77, 1.30)

1.21 (0.92, 1.61)

Religion

0.62

 Buddhist

1

1

1

1

 Muslim

0.85 (0.67, 1.08)

0.82 (0.57,1.18)

0.96 (0.65, 1.42)

0.96 (0.65, 1.42)

 Christian

1.40 (0.38, 5.24)

1.01 (0.12, 8.68)

0.72 (0.08, 6.47)

0.72 (0.08, 6.47)

ASA

Age, BMI, smoking

ASA I

1

1

1

0.19

ASA II

1.14 (0.85, 1.54)

1.22 (0.76, 1.97)

1.07 (0.64, 1.77)

ASA III

1.27 (0.90, 1.80)

1.66 (0.97, 2.82)

1.30 (0.74, 2.29)

BMI

-

25 - < 35 kg/m²

1

1

1

<  0.001*

< 25 kg/m²

1.28 (1.09, 1.50)

1.17 (0.92, 1.48)

0.91 (0.71, 1.18)

≥ 35 kg/m²

1.88 (1.33, 2.66)

1.84 (1.13, 3.00)

0.98 (0.60, 1.61)

Status

-

In-patient

1

1

1

0.02*

Out-patient

0.57 (0.34, 0.96)

0.43 (0.17, 1.08)

0.76 (0.28, 2.05)

ABO blood group

-

O

1

1

1

0.26

A

0.90 (0.73, 1.11)

1.28 (0.96, 1.72)

1.43 (1.05, 1.95)

B

1.02 (0.84, 1.23)

1.06 (0.79, 1.41)

1.04 (0.77, 1.41)

AB

1.16 (0.85, 1.58)

0.94 (0.57, 1.54)

0.81 (0.48, 1.36)

Smoking

-

No

1

1

1

0.48

Yes

0.90 (0.75, 1.07)

0.93 (0.71, 1.22)

1.04 (0.78, 1.39)

Premedication with benzodiazepine

-

No

1

1

1

0.89

Yes

1.06 (0.84, 1.34)

1.03 (0.72, 1.45)

1.03 (0.71, 1.49)

Preoperative use of gabapentin

-

No

1

1

1

0.002*

Yes

1.50 (1.00, 2.26)

2.43 (1.48, 4.00)

1.62 (0.97, 2.70)

Preoperative use of pregabalin

-

No

1

1

1

0.33

Yes

1.07 (0.26, 4.49)

3.12 (0.74, 13.09)

2.91 (0.58, 14.49)

Preoperative anxiety score

-

0

1

1

1

0.008*

1–5

0.99 (0.83, 1.18)

1.47 (1.12, 1.92)

1.48 (1.11, 1.96)

6–10

1.02 (0.82, 1.26)

1.74 (1.26, 2.39)

1.69 (1.21, 2.37)

Preoperative pain score

Sex, age, ABO blood group, benzodiazepine, gabapentin, pregabalin

0

1

1

1

0.24

1–3

0.94 (0.74, 1.21)

1.13 (0.79, 1.62)

1.20 (0.82, 1.76)

4–6

1.12 (0.87, 1.43)

1.51 (1.08, 2.10)

1.35 (0.94, 1.92)

7–10

1.03 (0.72, 1.48)

1.51 (0.94, 2.41)

1.46 (0.88, 2.42)

Anesthetic technique

-

GA

1

1

1

<  0.001*

TCI

0.18 (0.11, 0.31)

0.10 (0.03, 0.32)

0.55 (0.16, 1.91)

Spinal block

0.09 (0.06, 0.12)

0.05 (0.02, 0.10)

0.55 (0.27, 1.14)

Nerve block

0.11 (0.05, 0.25)

0.05 (0.01, 0.38)

0.49 (0.06, 4.11)

Combined

1.35 (1.06, 1.73)

1.81 (1.32, 2.48)

1.34 (0.98, 1.82)

Others

0.16 (0.06, 0.41)

0.09 (0.01, 0.69)

0.59 (0.07, 5.08)

Amount of intraoperative opioid use (MME)

Age, ASA, BMI, anesthetic technique, duration of anesthesia, duration of surgery, type of operation, reoperation, blood loss

-

1.01 (1.00, 1.02)

1.01 (1.00, 1.03)

1.00 (1.00, 1.01)

0.02*

Intraoperative use of paracetamol

-

No

1

1

1

0.003*

Yes

2.02 (1.18, 3.44)

2.85 (1.47, 5.51)

1.41 (0.74, 2.71)

Intraoperative use of parecoxib

-

No

1

1

1

<  0.001*

Yes

1.95 (1.45, 2.61)

2.54 (1.74, 3.72)

1.31 (0.89, 1.91)

Intraoperative use of ketamine

-

No

1

1

1

0.053

Yes

0.47 (0.22, 1.03)

0.34 (0.08, 1.43)

0.72 (0.15, 3.42)

Intraoperative use of ondansetron

-

No

1

1

1

<  0.001*

Yes

2.07 (1.78, 2.41)

1.22 (0.97, 1.53)

0.59 (0.46, 0.75)

Duration of anesthesia

Duration of surgery

-

1.00 (1.00, 1.00)

1.00 (0.99, 1.00)

1.00 (0.99, 1.00)

0.02*

Duration of surgery

-

-

1.00 (1.00, 1.01)

1.01 (1.00, 1.01)

1.00 (1.00, 1.00)

<  0.001*

Type of operation

-

General surgery

1

1

1

<  0.001*

C-section

0.06 (0.03, 0.12)

0.09 (0.03, 0.26)

1.61 (0.48, 5.44)

Otolaryngology

0.49 (0.38, 0.63)

0.19 (0.11, 0.33)

0.39 (0.22, 0.67)

Gynecology

0.79 (0.62, 1.01)

0.88 (0.62, 1.24)

1.11 (0.79, 1.58)

Neurosurgery

0.51 (0.29, 0.92)

0.17 (0.04, 0.74)

0.34 (0.08, 1.48)

Obstetrics

0.33 (0.19, 0.55)

0.30 (0.13, 0.72)

0.92 (0.36, 2.33)

Ophthalmology

0.30 (0.20, 0.46)

0.06 (0.01, 0.24)

0.19 (0.05, 0.82)

Orthopedics

0.37 (0.28, 0.48)

0.63 (0.44, 0.90)

1.71 (1.17, 2.49)

Plastic

0.73 (0.50, 1.05)

0.92 (0.56, 1.53)

1.26 (0.75, 2.12)

Thoracic

1.38 (0.48, 3.92)

9.36 (3.65, 24.02)

6.78 (2.98, 15.42)

Urological

0.28 (0.20, 0.39)

0.75 (0.51, 1.10)

2.65 (1.70, 4.12)

Vascular

0.26 (0.16, 0.42)

0.14 (0.05, 0.39)

0.54 (0.18, 1.58)

Reoperation

-

No

1

1

1

0.13

Yes

1.56 (1.00, 2.42)

1.42 (0.74, 2.72)

0.91 (0.47, 1.76)

Blood loss

Type of operation

Based on 1 ml

1.00 (1.00, 1.00)

1.00 (1.00, 1.00)

1.00 (1.00, 1.00)

<  0.001*

Based on 10 ml

1.09 (1.06, 1.12)

1.15 (1.11, 1.18)

1.05 (1.02, 1.08)

<  0.001*

Pain score upon PACU arrival (model 1)

ABO, age, anesthetic technique, benzodiazepine, blood loss, BMI, duration of anesthesia, intraoperative use of parecoxib, gabapentin, amount of intraoperative opioid use (MME), intraoperative use of ketamine, intraoperative use of paracetamol, preoperative anxiety, pregabalin, preoperative pain score, status, religious, reoperation, sex, smoking, duration of surgery, type of operation

-

2.09 (1.98, 2.21)

3.03 (2.79, 3.30)

1.45 (1.36, 1.55)

<  0.001*

Pain score upon PACU arrival (model 2)

Age, anesthetic technique, ASA, benzodiazepine, BMI, intraoperative use of parecoxib, gabapentin, amount of intraoperative opioid use (MME), intraoperative use of ketamine, intraoperative use of paracetamol, preoperative anxiety, pregabalin, preoperative pain score, religious, reoperation, sex, smoking, duration of surgery, type of operation

-

2.09 (1.98, 2.21)

3.04 (2.79, 3.30)

1.45 (1.36, 1.55)

<  0.001*

Use of paracetamol in PACU

-

No

1

1

1

<  0.001*

Yes

2.06 (1.14, 3.72)

9.41 (5.41, 16.37)

4.56 (2.68, 7.78)

Use of parecoxib in PACU

-

No

1

1

1

<  0.001*

Yes

3.76 (2.13, 6.64)

15.32 (8.79, 26.72)

4.07 (2.60, 6.38)