Ropivacaine Versus Bupivacaine for Spinal Anaesthesia in Patients Undergoing Unilateral Lower Limb Surgery

Inclusion Criteria: * Provision of written informed consent * Men or women, 18 years £ age £ 70 years * Patient scheduled for unilateral lower limb surgery with an estimated duration \< 2 hours under spinal anaesthesia * ASA category I \~ II * 18.5 ≤ BMI ≤ 23.9 Exclusion Criteria: * Contraindications to spinal anaesthesia, such as local infections, generalised septicaemia, platelet and clotting factor abnormalities, significant neurological disease with motor or sensory deficit, diagnosed increased intracranial pressure * A known history of allergy, sensitivity or any other form of reaction to local anaesthetics of amide type * Suspected inability to comply with the study procedures, including language difficulties or medical history and/or concomitant disease, as judged by the investigator * Psychiatric history or any other concomitant disease which may lead to unreliability in clinical assessments, as judged by the investigator * Significant alcohol, drug or medication abuse, as judged by the investigator * Women who are pregnant or lactating or women of child bearing potential who are not practising adequate contraception or have positive urine pregnancy test (a urine Human chorionic gonadotropin \[HCG\] analysis) * Involvement in the planning and conduct of the study (applies to both AstraZeneca staff or staff at the study site) * Previous enrolment in the present study * Participation in a clinical study during the last 3 months * Serious or unstable medical or psychological conditions that, in the opinion of the investigator, would compromise the subjects' safety or successful participation in the study.