Table 4.

Study Results pre- and post-implementation of the SOP

	All patients n = 166	Group 1 pre-SOP n = 50	Group 2 post-SOP n = 116	SMD
Ventriculitis, n (%)	22 (13.3)	11 (22.0)	11 (9.5)	0.349
Not-confirmed ventriculitis, n (%)	7 (4.2)	3 (6.0)	4 (3.4)	0
Pathogen detection, n (%)	14 (8.4)	7 (14.0)	7 (6.0)	0.067
EVD duration, days, median (IQR)	7.0 (4.0, 11)	9.0 (5.0, 14)	6.5 (4.0, 10)	0.376
EVD duration before onset of ventriculitis, days, median (IQR)	7.0 (5.0, 10)	8.0 (4.5, 10)	6.0 (5.5, 10)	0.145
Pre-Procedural antibiotic prophylaxis, n (%)	144 (86.7)	38 (76.0)	106 (91.4)	0.426
Empirical antibiotic therapy, n (%)	29 (17.5)	14 (28.0)	15 (12.9)	0.425
Duration of antibiotic therapy among treated patients, days, median (IQR)	14 (7.0, 16.0)	16 (12.0, 18.0)	10 (6.5, 15.0)	0.796
ICU length of stay, days, median (IQR)	12 (7.0, 19.0)	15 (8.0, 22.0)	11 (7.0, 18.0)	0.268
Mortality, n (%)	44 (26.5)	13 (26.0)	31 (26.7)	0.016

Several outcome parameters showed clinically relevant SMDs between pre- and post-SOP groups. The duration of antibiotic therapy among treated patients demonstrated a large difference (SMD = 0.796), supporting a strong effect of the SOP on ABS. Difference in ventriculitis incidence (SMD = 0.349), represented a clinically meaningful reduction from 22.0 to 9.5%, though the SMD appears modest because it accounts for variability in the data. Pre-procedural antibiotic prophylaxis (SMD = 0.426) indicated a small-to-medium effect, representing improved protocol adherence (76.0% to 91.4%). Empirical antibiotic therapy (SMD = 0.425) showed a small-to-medium effect, suggesting fewer suspected infections or improved diagnostic interpretation requiring treatment (28.0% to 12.9%). ICU mortality showed no relevant difference (SMD = 0.016), indicating safety of the SOP implementation

Abbreviations: CSF cerebrospinal fluid, EVD external ventricular drainage, ICU intensive care unit, IQR interquartile range, SMD standardized mean difference, n number