title: Lumbar microdiscectomy with spinal anesthesia: comparison of prone and knee-chest positions in means of hemodynamic and respiratory function.
abstract: METHODS
  Prospective clinical study to compare the physiologic changes in lumbar disc surgery regarding to positions.
  
  
  OBJECTIVE
  To compare the perioperative hemodynamic and respiratory functions between prone and knee-chest positions for lumbar disc surgery under spinal anesthesia.
  
  
  BACKGROUND
  Spinal anesthesia is a safe but rarely used alternative to general anesthesia for lumbar disc surgery. It reduces blood loss, avoid pressure necrosis, and nerve injuries, and it provides a more comfortable postoperative period. Prone and knee-chest positions are mostly used positions in lumbar discectomy; hemodynamic and respiratory effects of spinal anesthesia and the differences between these 2 positions in spinal anesthesia were evaluated in this study, which only been evaluated in general anesthesia.
  
  
  METHODS
  Forty-five patients were randomized for lumbar microdiscectomy with spinal anesthesia under either prone position (group 1 n = 22) or knee-chest position (group 2 n = 23). All patients were classified as physical status 1 or 2 according to the American Association of Anesthesiology. Spinal anesthesia was performed with hyperbaric bupivacaine. Perioperative continuous hemodynamics and respiratory function test results were recorded after the spinal anesthesia was performed.
  
  
  RESULTS
  Immediately after the spinal anesthesia was performed, both the systolic and diastolic arterial blood pressure values were significantly decreased and heart rates were significantly increased in both groups. Both positions showed significant decrease in forced vital capacity (P = 0.002) and forced expiratory volume in 1 second (P = 0.0015) during the surgery respect to preoperative values. The decrease in peak expiratory flow (P = 0.011) and forced expiratory flow at the 25% of the pulmonary volume (P = 0.011) was significant in knee-chest position respect to prone position.
  
  
  CONCLUSIONS
  In conclusion, spinal anesthesia is appropriate for lumbar disc surgery with respect to the hemodynamic parameters in both prone and knee-chest positions, however, in terms of pulmonary functions, the knee-chest position can cause a restrictive effect. Therefore this position should be used cautiously in higher-risk patients.
authors.affiliation: Department of Neurosurgery, Baskent University Istanbul Hospital, Oymaci Sok No: 7, Altunizade, Istanbul.
authors.forename: Cem
authors.initials: C
authors.lastname: Yilmaz
authors.forename: Selma Ozgur
authors.initials: SO
authors.lastname: Buyrukcu
authors.forename: Tufan
authors.initials: T
authors.lastname: Cansever
authors.forename: Salih
authors.initials: S
authors.lastname: Gulsen
authors.forename: Nur
authors.initials: N
authors.lastname: Altinors
authors.forename: Hakan
authors.initials: H
authors.lastname: Caner
mesh_terms: D000328:Adult; D000775:Anesthesia, Spinal / Q000379:methods*; D000779:Anesthetics, Local / Q000627:therapeutic use; D001794:Blood Pressure / Q000187:drug effects; D002045:Bupivacaine / Q000627:therapeutic use; D016009:Chi-Square Distribution; D017586:Diskectomy / Q000379:methods*; D005260:Female; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D055959:Intervertebral Disc Degeneration / Q000601:surgery*; D056446:Knee-Chest Position; D008159:Lumbar Vertebrae / Q000601:surgery*; D008297:Male; D016343:Monitoring, Intraoperative; D056888:Patient Positioning / Q000379:methods*; D016684:Prone Position; D011446:Prospective Studies; D012129:Respiratory Function Tests
chemical_list: D000779:Anesthetics, Local; D002045:Bupivacaine