Predicting hypotension during anesthesia: Variation in pulse oximetry plethysmography predicts propofol-induced hypotension in children

BACKGROUND

The development of hypotension on administration of intravenous propofol is common and independently associated with adverse outcomes. Identifying patients with a high risk for anesthesia-induced hypotension may help anesthesiologists prepare for such an event.

AIM

The authors hypothesized that propofol-induced hypotension is predictable by variables related to fluid responsiveness and investigated such variables to determine the factors which can predict hypotensive events.

METHODS

Patients 3-6 years of age who underwent general were included. Intravenous midazolam 0.1 mg kg^-1 was administered as premedication, and preoperative noninvasive blood pressure, heart rate, perfusion index, pleth variability index, and respiratory variation of pulse oximetry plethysmographic waveform were measured. Intravenous propofol 2.5 mg kg^-1 was given, and blood pressure was measured 5 times at 1-min intervals. Subjects with significant hypotension (mean blood pressure decrease ≥20%) were allocated to the hypotensive group; those without significant hypotension were allocated to the relatively normotensive group.

RESULTS

Of 77 patients, 50 (64.9%) developed significant hypotension. Patients in the hypotensive group exhibited significantly higher respiratory variation of pulse oximetry plethysmographic waveform (mean difference 11 [3.3] [95% confidence interval 4.9-18.1]; p = .001) and higher pleth variability index (mean difference 7.1 [2.8] [95% confidence interval 1.6-12.6]; p = .013) than the normotensive group. The areas under the receiver operating characteristic curve for respiratory variation of pulse oximetry plethysmographic waveform and pleth variability index were 0.722 and 0.649, respectively.

CONCLUSION

High preoperative respiratory variation of pulse oximetry plethysmographic waveform and pleth variability index were both independently associated with propofol-induced hypotension in children.

Assessment of pleth variability index in volume changes during ultrafiltration process

OBJECTIVES:

Pleth variability index (PVI) has been studied mostly in mechanically ventilated patients, and the role of PVI in predicting volume status and volume changes among spontaneously breathing patients is not clear in the literature. We hypothesized that hemodialysis (HD) can be a valid model for a simulation that can be evaluated the correlation of PVI with fluid changes in various volume states. The aim of this study was to investigate the utility of PVI for assessing volume changes in HD patients who are breathing spontaneously.

METHODS:

This prospective, observational study included patients aged 18 years or older who had end-stage renal failure and presented for routine HD between December 2019 and January 2020. PVI values were measured before and after HD session. Changes in PVI levels were compared according to the amount of ultrafiltration.

RESULTS:

A total of sixty patients were included. Mean PVI level before HD (20.7% ± 5%) showed a statistically significant increase to 27.7% ± 6% after HD session (P < 0.001). According to the amount of fluid removed during HD, the changes in PVI were statistically significant (P = 0.015). There was a strong correlation between ΔPVI and ultrafiltrated volume (r = 0.744, P < 0.001).

CONCLUSION:

The fluid removed by HD caused increase in PVI, and the increase was strongly correlated with the amount of volume change. Bedside monitoring of PVI may provide the clinicians with useful information for monitoring the volume status in critically ill patients with spontaneous breathing.