Table 1 Characteristics of 987 patients

Age (years)

66 (63 to 71)

66 (63 to 72)

0.820^{^}

Gender (female)

240 (55.05%)

202 (36.66%)

<  0.001^#

2.116

1.637–2.733

BMI (kg/m²)

23 (21 to 25)

23 (21 to 25)

0.454^{^}

ASA (grade)

0.332^#

 I

30 (6.88%)

41 (7.44%)

 II

334 (76.61%)

401 (72.60%)

 III

72 (16.51%)

110 (19.96%)

Hypokalemia (at admission)

54 (12.39%)

16 (2.90%)

<  0.001^#

4.727

2.665–8.384

Hypertension

181 (41.51%)

200 (36.30%)

0.095^#

1.246

0.963–1.612

Arrhythmia

18 (4.13%)

29 (5.26%)

0.406^#

0.775

0.425–1.415

Heart failure

1 (0.23%)

0 (0%)

0.442⁺

0.998

0.993–1.002

COPD

5 (1.15%)

8 (1.45%)

0.676^#

0.787

0.256–2.424

Diabetes

62 (14.22%)

66 (11.98%)

0.298^#

1.218

0.840–1.767

Diuretics

16 (3.67%)

22 (3.99%)

 Loop diuretics

3 (0.69%)

7 (1.27%)

0.557^*

0.538

0.138–2.094

 Thiazide diuretics

9 (2.06%)

5 (0.91%)

0.127^#

2.302

0.766–6.918

 Potassium-sparing diuretics

4 (0.92%)

6 (1.09%)

> 0.999^*

0.841

0.236–2.999

 Osmotic diuretics

4 (0.92%)

7 (1.27%)

0.826^*

0.720

0.209–2.474

ACEIs or ARBs

49 (11.24%)

56 (10.16%)

0.586^#

1.119

0.746–1.679

Oral laxative (≥2 times)

138 (31.65%)

91 (16.52%)

<  0.001^#

2.341

1.730–3.167

Enemas (≥2 times)

143 (32.80%)

110 (19.96%)

< 0.001^#

1.957

1.465–2.613

Time of surgery (min)

135 (100 to 211)

142 (105 to 210)

0.309^{^}

Time of anesthesia (min)

183 (140 to 267)

192 (149 to 259)

0.278^{^}