Hemodynamic changes in cervical myelopathy with prone position using non invasive cardiac output monitor

Introduction: Prone positioning under anaesthesia alters cardiovascular physiology and cervical myelopathy patients are known to have autonomic dysfunction thus putting them at higher risk of developing hemodynamic changes when proned and this can compromise spinal cord perfusion. Methods: This prospective observational study was conducted on 30 patients with cervical myelopathy who were positioned prone at NIMHANS. The non invasive cardiac output monitor (NICOM) was used to record hemodynamic parameters. The time points for recording were at baseline, post induction, post intubation, preprone position, post prone position every 5 min. The hemodynamic parameters recorded: HR - heart rate (/min), MAP - mean arterial pressure (mmHg), CO - cardiac output (l/min), SV - Stroke volume (ml/beat), SVV - stroke volume variability (%), TPR - total peripheral resistance (dynes. sec/cm⁵). Results: We found significant decrease in HR (p<0.001), MAP (p<0.001), TPR (p<0.001). SV, CO and SVV showed no significant change. This may due to impaired compensatory ability (to increase HR and TPR in response to fall in MAP, SV CO as seen in other studies) due to combined effects of anaesthesia and autonomic dysfunction. 60% patients had Hypotension in the post prone period and mephentermine requirement was high in the post prone positioning period. Conclusions: Hypotension occurs commonly after prone positioning in these patients. We conclude that the decrease in MAP is due to decrease in TPR and HR. We recommend use of vasopressors rather than inotopres to treat such hypotension in these patients.