[1] Univ Hosp No Sweden, Dept Anesthesiol & Intens Care, S-90185 Umea, Sweden
[2] Sahlgrens Univ Hosp, Inst Clin Neurosci, Dept Neurosurg, S-41345 Goteborg, Sweden
[3] Sahlgrens Univ Hosp, Inst Clin Neurosci, Dept Anesthesiol & Intens Care, S-41345 Goteborg, Sweden