Table 1. Description of independent variables selected for regression analysis.

Therapy aspect	Independent variable	Units of variable measure	Variable description
Patient demographics	Age	years	Patients' age on admission to hospital
	Gender	male vs female	Patients' gender
Patient neurological status on admission to hospital	GCS	points	Glasgow Coma Scale (GCS)
	Markwalder	points	Markwalder scale
	ND	YES vs. NOT	Presence of neurological deficit
Laboratory tests on admission to hospital	Na	mmol/l	Level of Natrium in serum
	Hct	Percents (%)	Value of Hematocrit in blood
	ACP	YES vs. NOT	Abnormal coagulation profile
Hematoma characteristic	HT	millimetres	Thickness of hematoma
	BLH	YES vs. NOT	Bilateral hematoma
Treatment characteristic	Competence	(S vs T)	The level of surgeon competence (specialist or on-training). However all surgeries were supervised by attending neurosurgeons.
	IFA	days	The number of days after surgery when fluids were administered intravenously