Table 1.

Patient demographics and general surgical information

Characteristic	Value
Total no. of patients	962
Age (yr)	71.1±0.55
>75	505 (52.5)
Gender
Male	450 (46.8)
Female	512 (53.2)
ASA class (n=933)
1	73 (7.8)
2	394 (42.2)
3	423 (45.3)
4	43 (4.6)
Previous spine surgery	332 (34.5)
Operated levels	3.24±0.07
>3	464 (48.2)
>5	186 (19.4)
CSF leaks	42 (4.4)

Values are presented as number, mean±standard error of the mean, or number (%). ASA class was available for 933 patients.

ASA, American Society of Anesthesiologists; CSF, cerebrospinal fluid.