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Background: Propofol as an intravenous (IV) induction agent frequently causes
significant hypotension and requires monitoring and prompt intervention. The
plethysmographic waveform, obtained from a pulse oximeter, relies on two
components of light absorption-red and infrared, representing changes in blood
volume and cardiovascular status of the patient. Aims and Objectives: The
current study aimed to obtain a baseline value and positive predictive value
(PPV) of plethysmographic variability index (PVI) to predict hypotension and also
compare the PPV of PVI and perfusion index (PI) to predict hypotension induced
by propofol. Materials and Methods: Seventy patients posted for elective surgery
were first given IV crystalloids 2 h before surgery and then induced with propofol
IV. Hemodynamic parameters, PI and PVI were recorded from baseline until 3 min
post-intubation. Hypotension was defined as a fall in systolic blood pressure >30%
or mean arterial pressure (MAP) <60 mmHg. Patients were then grouped into
those who developed hypotension (Group H) and those who did not (Group NH).
Statistical analysis of MAP, PVI, and PI was done. Receiver operating characteristic
(ROC) curves were plotted and analyzed. The PPV of PVI and PI was calculated
and compared. Results: Hypotension occurred in 56 patients. The mean baseline
MAP was lower in Group H (91.3±10.54 mmHg vs. 99.93±3.36 mmHg). The
fall in MAP was highest at 3 min post-induction (Group H 59.38±7.09, Group NH
79.36±8.05). The difference in baseline PVI was not statistically significant
(Group H 15.59±3.67, Group NH 15.43±5.65). PVI peaked in Group H when
MAP was minimum (59.38±7.09 mmHg) at 3 min post-induction. The difference
in baseline PI was not significant at any time point (Group H 1.13±1.02, Group NH
0.92±0.47) Area under the ROC curve of 0.534 for PVI and 0.559 for PI were
not statistically significant hence showing no correlation between baseline PVI and
PI and propofol-induced hypotension. Conclusion: Baseline PVI and PI can serve
as screening tools and not diagnostic tools for predicting hypotension. Baseline
PVI ≥19 is more accurate to predict post-induction hypotension than the values
mentioned in previous studies.
Key words: Plethysmographic variability index; Perfusion index; Hypotension;
Propofol