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Table 1 Patient demographics

From: Analysis of risk factors for perioperative hidden blood loss in unilateral biportal endoscopic spine surgery: a retrospective multicenter study

Parameters Statistics
Total patients (n) 136
Sex (n)
 Female 55
 Male 81
Age, year 54.1 ± 8.4
BMI, kg/m2 24.5 ± 3.5
Hypertension (n)
 No 104
 Yes 32
Diabetes mellitus (n)
 No 107
 Yes 29
Smoking (n)
 No 82
 Yes 54
Drinking (n)
 No 72
 Yes 64
Length of stay, day 7.3 ± 1.7
Diseases groups
Lumbar disc herniation 64
Lumbar stenosis 45
Lumbar spondylolisthesis 27
Fusion level (n)
 L3-L4 12
 L4-L5 45
 L5-S1 47
ASA classification (n)
 I 50
 II 51
 III 32
 IV 3
Surgery time, min 168.3 ± 52.7
PBV, L 4.9 ± 0.5
TBL, ml 786.5 ± 189.3
VBL, ml 278.2 ± 85.2
HBL, ml 469.5 ± 195.3
Preoperative Hb, g/L 125.1 ± 11.6
Preoperative Hct 37.6 ± 4.6
Postoperative Hb, g/L 107.2 ± 13.5
Postoperative Hct 31.9 ± 4.1
Hb loss, g/L 17.9 ± 2.5
Hct loss 5.7 ± 1.6
Preoperative ALB, g/L 41.2 ± 3.5
PT, s 11.9 ± 1.1
APTT, s 29.1 ± 5.2
Platelet, g/L 251.8 ± 49.8
Fibrinogen, g/L 3.4 ± 0.5
  1. BMI body mass index, ASA American Society of Anesthesiologists, Hct hematocrit, Hb hemoglobin, ALB albumin, PT prothrombin time, APTT activated partial thromboplastin time, PLT platelet, TBL total blood loss, PBV patient’s blood volume, VBL visible blood loss, HBL hidden blood loss