Hidden blood loss and its possible risk factors in cervical open-door laminoplasty

OBJECTIVES: To evaluate hidden blood loss (HBL) and its possible risk factors among patients following expansive open-door laminoplasty (EOLP) for multilevel, cervical spondylotic myelopathy. METHODS: This was a retrospective analysis of data from patients over 18 years of age who underwent posterior cervical EOLP (from C3-C6) in our department from January 2017 to July 2018. HBL was calculated by deducting the observed perioperative blood loss from the calculated total blood loss (TBL) based on the fall in haematocrit level. RESULTS: 45 patients (35 men and 10 women) were identified. Mean ± SD HBL was 337.2 ± 187.8 ml, which was 46.8% of the total perioperative blood loss (705.2 ± 269.6 ml). Twenty-three patients developed postoperative anaemia. Posterior cervical soft tissue was positively correlated with both TBL and hidden blood loss (HBL) and hypertension was positively correlated with TBL. CONCLUSIONS: HBL following cervical EOLP was significant and should be recognised as a detrimental factor to patient safety during the perioperative period, especially in patients with thick posterior cervical soft tissue.