TABLE 2.

Study characteristics for subset of 200 studies.

Study ID	Study ID, name of pdf-file, first author, title, year of publication, journal, issue, pages, country of origin
Study design characteristics	Number of animals per group (minimum and maximum numbers of animals per group), total number of animals used, background/purpose of craniotomy/field of research
Animal model characteristics	Species, sex, breeder, strain, age at surgery, weight at surgery, housing condition, housing temperature, housing humidity, type of cage, enrichment, light schedule, handling technique
Intervention characteristics	Duration of surgery, survival surgery, how long did animals live after surgery approximately, mortality during surgery, fate of used animals, type of surgical procedure, implantation site, insult size, trepanning size, model used, general anesthesia scheme, compound name/names, route of administration, dosage (mg/kg BW) or concentration (vol.%), how many times administered, administration interval, local anesthesia administered, compound name/names, dosage (mg/kg BW), injection volume (ml/animal), route of administration, timepoint of first administration, administered how many times in total, administration interval, pharmaceutical formulation, analgesic antipyretic agents administered, compound name/names, dosage (mg/kg BW), route of administration, timepoint of first administration, administered how many times in total, administration interval, pharmaceutical formulation, opioid administered, compound name, dosage (mg/kg BW), route of administration, timepoint of first administration, administered how many times in total, administration interval, pharmaceutical formulation, other analgesics used, if so compound name, multimodal approaches used [total number of used compound groups (analgesics and local anesthetics)], other drugs (other than analgesics) used, antibiotic agent used, compound name, route of administration, specific monitoring during surgery, peri-operative care, non-pharmacological measures for pain management, refinement measures
Outcome measures	Assessment of the efficacy of pain alleviating measures, assessment of the analgesic efficacy post-surgery, parameters testing efficacy of pain/stress reducing measures post-surgery, blinding, randomization, power analysis

Study characteristics extracted from subset of 200 studies, defined in the pre-published study protocol and additional study characteristics added during the process of designing the extraction table. Written in black: characteristics specified in the study protocol. Written in gray: characteristics documented in addition to characteristics specified in the study protocol. ID, identity; mg, milligram; BW, body weight; Vol. %, volume percent.