title: Prospective controlled cohort study of Troponin I levels in patients undergoing elective spine surgery for degenerative conditions: Prone versus supine position.
abstract: Prior studies have suggested that elevated serum Troponin-I (TnI) levels immediately after non-cardiac surgical procedures (8-40%) represent subclinical cardiac stress which independently predicts increased 30-day mortality. Routine post-operative TnI monitoring has therefore been suggested as a standard of care. However, no prior studies have focussed on elective degenerative spine surgery, whilst few have measured pre-op TnI. Further, prolonged prone positioning could represent an additional, independent, cardiac stress. We planned a prospective controlled cohort study of consecutive TnI levels in routine elective spine surgery for degenerative spine conditions, incorporating 3 groups: 'prone<2h', 'prone>2h' and 'supine' positioning. TnI levels (>0.04μg/L) were recorded immediately pre-/post-surgery, and by 24h of surgery. N=120 patients were recruited. Complete results were obtained in 92 (39 supine, 53 prone). No significant between-groups differences were observed in demographic or cardiovascular risk factors. Validated TnI-elevation by 24h was not observed in any group. Spurious elevations were recorded in one 'prone<2h' and one 'prone>2h'. One non-ST segment myocardial infarction (STEMI) occurred on day 7 without TnI elevation by 24h (prone>2h). There was no 30-day mortality.
  
  
  CONCLUSIONS
  Despite a lower cut-off, no validated TnI elevation was observed in any group by 24h after surgery. One non-STEMI had not been associated with TnI-elevation by 24h. Immediately peri-operative cardiac stress therefore appeared comparatively rare in patients undergoing routine elective spine surgery. Further, prone positioning did not represent an additional, independent, risk. Routine immediately post-operative TnI monitoring in elective spine surgery therefore appears unjustified. Our study highlighted several caveats regarding consecutive TnI testing.
authors.affiliation: Department of Neurosurgery, The Townsville Hospital, Douglas, Townsville 4810, Queensland, Australia.
authors.forename: A I
authors.initials: AI
authors.lastname: Macfarlane
authors.affiliation: College of Public Health, Medical and Veterinary Sciences James Cook University, Douglas, Townsville 4810, Queensland, Australia.
authors.forename: D
authors.initials: D
authors.lastname: Rudd
authors.affiliation: Department of Neurosurgery, The Townsville Hospital, Douglas, Townsville 4810, Queensland, Australia.
authors.forename: E
authors.initials: E
authors.lastname: Knight
authors.affiliation: Department of Neurosurgery, The Townsville Hospital, Douglas, Townsville 4810, Queensland, Australia; School of Medicine and Dentistry, James Cook University, Douglas, Townsville 4810, Queensland, Australia. Electronic address: l.a.g.marshman@btinternet.com.
authors.forename: L A G
authors.initials: LA
authors.lastname: Marshman
authors.affiliation: Department of Neurosurgery, The Townsville Hospital, Douglas, Townsville 4810, Queensland, Australia; School of Medicine and Dentistry, James Cook University, Douglas, Townsville 4810, Queensland, Australia.
authors.forename: E P
authors.initials: EP
authors.lastname: Guazzo
authors.affiliation: Department of Neurosurgery, The Townsville Hospital, Douglas, Townsville 4810, Queensland, Australia.
authors.forename: D S
authors.initials: DS
authors.lastname: Anderson
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D015331:Cohort Studies; D017558:Elective Surgical Procedures / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D056888:Patient Positioning / Q000379:methods*; D011446:Prospective Studies; D012307:Risk Factors; D013122:Spinal Diseases / Q000097:blood* / Q000175:diagnosis / Q000601:surgery*; D016683:Supine Position / Q000502:physiology*; D019210:Troponin I / Q000097:blood*
chemical_list: D015415:Biomarkers; D019210:Troponin I
keywords: Prone; Spine surgery; Troponin-I