Serial Assessment of Hemodynamic and Cerebrovascular Changes After Administration of Mannitol in Postoperative Neurosurgical Patients in the Intensive Care Unit: A Combined Transthoracic and Transcranial Color Doppler Study

TL;DR

This study examines how mannitol affects blood flow and heart function in neurosurgery patients after surgery, finding temporary improvements in brain blood flow without major heart issues.

Contribution

The study provides new insights into the transient cerebrovascular effects of mannitol in postoperative neurosurgical patients.

Findings

Mannitol caused immediate increases in cerebral blood flow on the first postoperative day.

These effects were temporary, with no significant changes observed on the second day.

Cardiovascular parameters like stroke volume and cardiac output remained stable.

Abstract

Introduction: Mannitol is widely used in neurosurgical units to mitigate raised intracranial pressure and cerebral edema, crucial in postoperative management. Its hyperosmolar properties reduce brain extracellular fluid, thereby altering cerebral perfusion and cardiac dynamics. However, the temporal and combined effects of mannitol on cardiovascular and cerebrovascular parameters remain inadequately explored in postoperative settings.

Methods: This prospective observational study enrolled 20 adult patients who underwent elective craniotomies for tumor excision. Mannitol was administered to the patients at a dose of 0.5 mg/kg/dose as a bolus dose over 20 to 30 minutes. The time interval was eight hours between the doses (scheduled dosing). Patients received their first dose of mannitol in the ICU after eight hours of intraoperative dose. The patients were given mannitol for two postoperative days and followed up for two days in the postoperative period. Transthoracic echocardiography and transcranial color Doppler were used to assess cardiovascular and cerebrovascular parameters at multiple intervals post-mannitol administration.

Results: Significant increases in mean flow velocities were observed bilaterally immediately post-mannitol administration on the first postoperative day, indicative of improved cerebral blood flow. However, these changes were transient, with no significant variations noted on the second postoperative day. Cerebrovascular resistance, as measured by the pulsatility index, showed non-significant changes bilaterally across both days. Cardiovascular parameters, including stroke volume and cardiac output, remained stable throughout the study period.

Conclusion: Mannitol administration at 0.5 g/kg in postoperative neurosurgical patients transiently improves cerebral perfusion without causing significant hemodynamic instability. This study underscores the importance of monitoring both cerebrovascular and cardiovascular parameters post-mannitol administration to optimize patient management and outcomes.

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