The Relationship Between Perfusion Index and Pleth Variability Index and Hemodynamics in Spinal Anesthesia

In recent years, the trend towards noninvasive monitoring methods has increased instead of invasive monitoring methods. Plet Variability Index (PVI), perfusion index (PI) are non-invasive, easily applicable and easily interpretable new monitoring methods. It has been shown that intraoperative hypotension and fluid requirement can be predicted, especially with Plet Variability Index (PVI) monitoring. Hypotension is the most common complication of spinal anesthesia. If no precautions are taken, it is seen in 80-90% of cases. associated with a decrease in peripheral vascular resistance. Recent studies have shown that cardiac output does not decrease, but slightly increases or does not change, and venous return does not change with spinal anesthesia. Aortocaval compression may exacerbate hypotension due to neuraxial anesthesia. The PI is obtained by calculating the ratio of pulsatile blood flow to nonpulsatile blood flow in peripheral tissues by pulse oximetry. This ratio reflects changes in peripheral vascular resistance. For example, a low PI indicates peripheral vasoconstriction. PVI represents changes in PI that occur during one or more complete respiratory cycles. Provides evaluation of intravascular volume; and a higher PVI is associated with greater responsiveness to fluid volumes. In some studies, it is stated that PI and PVI values obtained from pulse oximetry are predictive for SA-induced hypotension in cesarean deliveries; There are also studies in the literature showing the opposite. In this study, the researchers aimed to test the hypothesis that hypotension can be predicted by using PVI representing cardiac preload and PI representing vascular tone in pregnant women after spinal anesthesia and to examine the superiority of these values.

OBJECTIVE: Today, spinal anesthesia (SA); Since it is less risky for maternal and new born health compared to general anesthesia, it is a more preferred method in elective cesareansection operations. Hypotension due to spinal anesthesia, which is the most common side effect of spinal anesthesia, is frequently seen in patients. Due to the negative consequences of hypotension on the mother and newborn; It is important to take the necessary precautions against this hemodynamic deterioration. Perfusion index (PI) and pleth variability index (PVI) are parameters that can be measured noninvasively by pulseoximetry. In our study; By examining the lower extremity PI and PVI values in patients who will undergo elective cesareansection with SA; We investigated the usability and superiority of these values over each other in predicting hemodynamic deterioration.

METHODS: This research; It was conducted as a prospective observational study and 113 pregnant women aged 18-40 years who were ASA1-2 who were going to undergo lower segment cesarean section were included in our study. Demographic data of the patients (age, gender, weight, height, BMI) and routine hemogram values (hemoglobin, hematocrit, platelet, wbc) taken for preoperative evaluation were recorded. After the patients were placed on the operating table, PI and PVI values in the supine and sitting positions, PI and PVI values at the 1st, 2nd, 3rd, and 4th minutes after spinal anesthesia was applied to the patient, and finally, the postpartum PI, PVI values were recorded. In addition, in order to follow up the hemodynamic changes in all patients in thes tudy, Standard monitoring including electrocardiography, non-invasive blood pressure measurements and pulse measurement was performed, and changes in systolic pressure, diastolic pressure and heart rate were recorded before and after spinal anesthesia.

In our study, in which we examined PI and PVI values in predicting hypotension due to spinal anesthesia in elective C/S operations, we have reached the following results.

Unlike other studies in the literature; In our study, in which we followed the PI and PVI values in the lower extremities together and examined the diagnostic superiority of these values to each other and the relationship between the hemogram and hematocrit values of the patients, we did not find a statistically significant difference in the increase in the lower extremity basal PI and PVI values in the patient groups with and without hypotension. We interpreted this situation as lower extremity basal PI and PVI values were not effective in predicting hypotension due to spinal anesthesia.

We observed that there was no change in PI and PVI values in 5 patients who were not included in the study in whom spinal anesthesia failed, and that there was an increase in successful procedures independent of the development of significant hemodynamic instability. As a result, our study supported previous studies that PI and PVI values could be used to evaluate the success of spinal block.

In addition, we found that hgb and hct values were significantly lower in the hypotension-developing group in our study, but we found that this did not cause a significant difference in basal PI and PVI values. We think that the surgical HGB limit should be reconsidered in patients who will undergo elective surgery, due to the increased risk of hypotension if the patients have low hemogram values, and we believe that it would be beneficial to conduct more comprehensive multicenter studies in both cases.