Determine the Correlation Coefficient between the Plethysmographic Variability Index and Pulse Pressure Variation as a Marker for Intravascular Volume Status in Non Laparoscopic Abdominal Surgery: A Cross-sectional Study

Introduction: Precise evaluations of intravascular fluid status are crucial for managing haemodynamically unstable patients and for perioperative treatment. Assessing a patient’s response to fluid resuscitation is a vital and challenging aspect of intraoperative care. Aim: To study the correlation of the Plethysmographic Variability Index (PVI) and Pulse Pressure Variation (PPV) for prediction of fluid responsiveness in non laparoscopic abdominal surgery patients. Materials and Methods: This was a cross-sectional observational study conducted at Base Hospital Delhi Cantt, India after obtaining approval from the ethical committee and written informed consent. A total of 55 American Society of Anaesthesiologists (ASA) I/II patients of any gender, aged between 18-60 years, who were undergoing major surgery requiring invasive arterial pressure monitoring, were included in the study. The surgery was carried out using standard general endotracheal anaesthesia along with muscle relaxation and intermittent positive pressure ventilation. The PPV and PVI were measured using the Masimo Rainbow set pulse co-oximetry. Measurements were taken five minutes before a fluid bolus and then at five-minute intervals after the fluid bolus, up to 30 minutes. The Pearson correlation coefficient, Bland-Altman plot, independent sample Student’s t-test and Chi-square test were used to test statistical significance. A p-value of <0.05 was considered statistically significant. Results: In the group of 55 patients, there were 31 females and 24 males, with age (Mean±SD) of 42.62±13.25 years for fluid responders and 47.07±13.12 years for non responders. Among them, 13 were identified as fluid responders based on a PPV >13, and 22 were identified based on a PVI >12.5. There were no significant variations in mean Heart Rate (HR) and Mean Arterial Pressure (MAP) between fluid responders and non responders (p-value >0.05). Age, gender and Haemoglobin (Hb) levels were comparable in fluid responders and non responders (p-value >0.05). A statistically significant positive correlation was observed between PPV and PVI at 0, 5 and 15 minutes. The difference in PPV between fluid responders and non responders was significant at all time points (p-value <0.001). The area under the Receiver Operating Characteristics (ROC) curve for fluid responsiveness by PVI was 0.625 (95% CI: 0.453-0.797). The sensitivity and specificity of PVI were 53.85% and 64.29%, respectively. Conclusion: Fluid responders and non responders showed a positive correlation between PPV and PVI. The PVI is a highly effective tool for guiding perioperative fluid management.