Authors’ contributions
DB, GB, GL, FC, LM, LG, AS, CB and LV significantly contributed to patient enrollment in the clinical study, to the actual clinical application of the protocol and data collection in the operating theatre and neurosurgical ward. DB made PCA pumps and ultrasounds available in the theatre. DB, GB, ER and DPS conceived the study protocol and prepared the ethical committee. ER performed the statistical analysis. DB, GB and GL interpreted the data and extrapolated/discussed the key messages from this work. GB drafted the article. AT, LT and VA reviewed the article and substantively revised it. All authors read and approved the final manuscript.