The Effect of Propofol versus Etomidate Induction on Middle Cerebral Artery Flow Velocities and its Derived Parameters Using Transcranial Doppler Ultrasonography

Background: Transcranial Doppler Ultrasonography (TCD) is a valuable noninvasive addition to comprehensive neurological monitoring. Our objective is to compare the effect of intravenous propofol vs etomidate induction on middle cerebral artery (MCA) flow velocities and its derived parameters, as measured by TCD evaluation in patients undergoing surgery for intracranial tumors. Material and Methods: Forty patients aged 15 to 70 years, with intracranial space occupying lesions (SOL) posted for craniotomy and excision of SOL were randomly selected to receive intravenous propofol or etomidate during induction of anaesthesia. A RIMED DIGI-LITE TCD system (software version 1.17.5.5) was used to insonate the MCA on the non-tumor side. Patients vitals including mean arterial pressures (MAP) and MCA flow velocities (peak systolic, diastolic and mean) were measured at pre induction and at 1 min, 3 min, 5 min, 10 min and 30 min after induction. The pulsatility (PI) and resistivity (RI) indices and transient hyperemic response ratio (THRR) were derived and the above were compared with their preinduction/awake values. Results: Within a MAP range of 50 to 120 mm Hg, propofol induced a significant fall in MCA flow velocities (21.6 ± 32%; p-value=0.001). There was no significant change in flow velocities during intubation with the use of either drug. The PI increased significantly at the time of intubation in both the groups. The mean PI was raised with propofol [1.26 ± 0.42 (p-value=0.036)] as well as with etomidate [1.41 ± 0.38 (p-value=0.006)]. There was a significant fall in estimated cerebral perfusion pressure after propofol induction but not with etomidate. No significant change in the Transient Hyperemic Response Ratio was seen in either of the two groups. Conclusion: Propofol decreases cerebral blood flow velocities and perfusion pressure. Etomidate provides stable hemodynamic parameters, flow velocities and perfusion pressures. Both drugs preserve cerebral autoregulation and provide good intubating conditions in patients with intracranial tumors.