Discussion
heterogenous, critically ill, cardiac and non-cardiac procedures [The gray zone, hypertensive, hypotension, hypertension
CRITICALLY ILL, CARDIOVASCULAR DISEASES, CVD, HEMODYNAMIC INSTABILITY, HYPERTENSION
The current study revealed that IVCCI > 39% before induction of GA can predict the onset of hypotension after induction of GA for noncardiac surgery in hypertensive patients not treated with ACEIs or ARBs. The gray zone existed for IVCCI between 39 and 45% and included 13.7% of the studied patients. IVCCI before induction was found to strongly correlate with the maximum percentage of SAP or MAP drop after induction of GA. The incidence of postinduction hypotension was 40.5% among the studied hypertensive patients.It was shown that even short periods of intraoperative hypotension (1–5 min) can be associated with increased perioperative morbidity in cardiac and noncardiac surgeries [IVCCI needs little echocardiographic experience to assess, in addition to being a feasible, noninvasive, and cost-effective tool for assessing intravascular volume and fluid responsiveness in critically ill patients [Similar to current findings, IVCCI > 38–50% can predict hypotension after induction of GA by different accuracies (AUC 0.648–0.959) in mixed patients’ population with or without cardiovascular diseases (CVD) undergoing either cardiac and non-cardiac procedures [The gray zone approach by Zhang and Critchley revealed an area of uncertainty of IVCCI values between 38% and 43%, including 12% of all studied patients. For patients with CVD, a wider gray zone for IVCCI was found in patients with CVD (29–43%), indicating less reliability of IVCCI in the prediction of postinduction hypotension in patients with CVD. Our findings revealed a narrower gray zone of IVCCI for the prediction of postinduction hypotension (39–44%) and hence higher reliability in hypertensive patients. Similar to the current findings, Zhang and Critchley found a significant correlation between IVCCI and the percentage of maximum drop in MAP after induction of GA (In contrast to the current finding, Zhang and associates demonstrated poor performance of IVCCI (best cutoff value 50%) before induction in predicting hypotension after induction of GA in hypertensive patients (AUC 0.523 vs. 0.908 in the current study), while they found a comparable predictivity in normotensive patients (AUC 0.896). The different findings from the current study may be due to different sample sizes (51 vs. 153 hypertensive patients in the current study), different outcome definitions (based on MAP only in Zhang’s study vs. considering both SAP and MAP in the current study) or the state of hypertension control in the included patients (heterogenous population in Zhang study vs. controlled hypertensive patients in the current study) [Agarwal and associates demonstrated poor accuracy (53%) of IVCCI (best cutoff value ≥ 63.3%) in the prediction of postinduction hypotension in the general population (AUC 0.568, sensitivity 31% and specificity 84%). The difference between Agarwal’s study and the current study may be due to different studied populations (general population versus controlled hypertensive population in the current study) or older age of patients in the current study [Mohammed and associates also showed poor accuracy of IVCCI ≥ 46% in predicting hypotension after induction of GA in a young healthy adult population (AUC 0.51) and found no correlation between IVCCI and maximum drop in MAP. The differences from current findings may be due to different studied populations, different incidences of postinduction hypotension (19.3% in the Mohammed study vs. 40.5% in the current study) or different sample sizes [Patients who developed hypotension in the current study had higher IVCCI, and they were older in age. Increasing age can be associated with increased respiratory variability of IVC [This current study was limited first, as it did not include measurement of maximum IVC diameter as another potential predictor of hypotension after induction of GA. Second, the variability of operative interventions studied. Third, patients on ACEIs or ARBs medications were excluded from the study to avoid their high vasodilatory effect as a confounder and so the results of current study cannot be applied to such patients’ population.Ultrasonographic assessment of IVCCI still can be used preoperatively as a point of care tool to predict the onset of hypotension after induction of GA especially in patients at high risk of developing hemodynamic instability. Szabó and associates succeeded in decreasing the incidence of early intraoperative hypotension by using both preoperative IVCCI and pulmonary ultrasound to guide preprocedural fluid therapy [