Pulse-plethysmographic variables in hemodynamic assessment during mannitol infusion

Area of Science:

• Anesthesiology and Critical Care Medicine
• Cardiovascular Physiology
• Medical Engineering

Background:

• Plethysmographic signals from pulse oximetry offer a potential non-invasive method for assessing fluid status during surgery.
• This approach could eliminate the need for invasive arterial lines, improving patient safety and comfort.

Purpose of the Study:

• To determine if mannitol-induced intravascular volume changes in neurosurgical patients are detectable by arterial pressure and plethysmographic waveforms.
• To assess the correlation between variables derived from these waveforms.
• To evaluate the blood pressure-plethysmographic time lag as an indicator of hemodynamic changes.

Main Methods:

• Forty-one adult neurosurgical patients received mannitol infusion.
• Arterial and plethysmographic waveforms were recorded invasively and non-invasively, respectively.
• Parameters including systolic pressure variation (SPV), pulse pressure variation (PPV), plethysmographic peak variation (Pl-PV), plethysmographic amplitude variation (Pl-AV), and blood pressure-plethysmographic time lag (BP-Pleth time lag) were analyzed using MATLAB.

Main Results:

• SPV and Pl-PV significantly increased post-mannitol infusion (P < 0.01 and P < 0.05, respectively).
• PPV and Pl-AV showed significant increases at 30 minutes (P < 0.05).
• Significant correlations were found between changes in SPV and Pl-PV, PPV and Pl-AV, and SPV and BP-Pleth time lag (r = 0.3, P < 0.01).

Conclusions:

• Plethysmographic peak variation (Pl-PV) correlates well with systolic pressure variation (SPV) and can be used as a non-invasive alternative for monitoring hemodynamic changes.
• The blood pressure-plethysmographic time lag shows promise for assessing peripheral vascular resistance and warrants further investigation.