[1] Sahlgrenska Univ Hosp, Dept Clin Physiol, Gothenburg, Sweden
[2] Sahlgrens Univ Hosp, Inst Neurosci, Dept Neurosurg, Gothenburg, Sweden
[3] Sahlgrens Univ Hosp, Inst Surg Sci, Dept Anesthesia & Intens Care, Gothenburg, Sweden
[4] Univ Umea Hosp, Inst Surg & Perioperat Sci, Dept Anesthesia & Intens Care, Umea, Sweden