Risk factors for cardiac arrest during spine surgery have been well defined, including lumbar fusion, age over 65 years, obesity, cardiovascular disease, ethnicity and ASA status. Bradycardia and asystole have been described under general anaesthesia in combined surgical cohorts: Proposed mechanisms include unopposed parasympathetic activation, enhanced vasovagal response to decreased venous return, and psychiatric stressors. The investigators prospectively will review patients candidates for spine surgery to explore potential incidence, contributory factors and outcomes to unexpected transient intraoperative haemodynamic instability, arrhythmia, and cardiac arrest during spine surgery as these data are needed to aid risk stratification and improve decision making for spine care teams.

Inclusion Criteria:

1. Aged more than 18
2. Gender: both.
3. ASA grade I-II (American society of anesthiologists).
4. Prepared to spine surgery under general anesthesia

Exclusion Criteria:

1. Ischemic heart patients
2. Hypertensive patients
3. Patients with atrial fibrillation or any previous history of attack of arrhythmias
4. Patients on B.B ( beta-blockers)
5. Chronic use of neuropsychiatric medications
6. Renal Impairment
7. Liver Dysfunction.
8. Any complications during the procedure as massive hemorrhage
9. Surgery for traumatic spinal cord

population candidated for spine surgery