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Post-Cesarean Hematocrit Prediction Model Using Nonlinear Least Squares Method
Abstract Number: T3B-3
Abstract Type: Original Research
The most widely used method for estimating blood loss (EBL) is the surgeons’ visual estimation while performing cesarean deliveries (CD). Traditional calculation of volume management relies heavily on EBL, resulting in under/over estimation. The purpose of this study is to find a better fitted equation to estimate postoperative hematocrit (Hct) to guide appropriate volume therapy.
All parturients who had CD from 6/1/2015 to 12/31/2017 who received intraoperative second-line uterotonic agents were identified. Pertinent perioperative data from Partners' electronic medical records were extracted.
There were 325 patients collected. Nonlinear least squares method was used to fit the model to calculate postoperative Hct. We found that total blood volume before surgery (p<0.0001), EBL (p=0.0002), total crystalloid volume used after operation (p=0.0112), total colloid volume (p=0.0286), and total urine volume during operation process(p=0.0043) were significantly associated with post-operation Hct. Total crystalloid volume used during operation process was marginally significant (p=0.0816) and was included in the final model for better estimation. The equation was: Post-Hct% = [(0.75*TBV +0.14*TCO+0.12*TCA-0.40*EBL-0.41*TCV-1.01*TUV)* 𝑝𝑟𝑒-Hct+5.32]%. (Note: TBV: total blood volume before surgery (ml); TCO: Total crystalloid volume used during operation; TCA: total crystalloid volume used after operation; TCV: total colloid volume; TUV: total urine volume during operation process; 𝑝𝑟𝑒-Hct: preoperative Hct)
Blood volume expansion in pregnancy is commonly recognized. The blood volume at term is approximately 50% higher than that of the nonpregnant. In the situation of acute operative bleeding, volume administration is usually needed to correct hypovolemia. Crystalloids remain the volume replacement solution of first choice, especially in the peripartum period. Half-times of crystalloids range from 16-26 minutes, and it depends on the rate of fluid infusion. Our study showed that crystalloid and colloid use by anesthesiologists were correlated with blood loss, and crystalloid was mainly used as blood loss replacement. Timely blood resuscitation is important to provide life-saving benefits to patients when needed. In our study, only 9.2% (30/325) patients needed blood transfusion to compensate blood loss. Our data demonstrated that high dosage of vasopressors was used in patients with neuraxial anesthesia than those received general anesthesia. Vasopressors was not related to calculated blood loss or EBL. Instead, it was mainly used to maintain blood pressure to protect perfusion of vital organs. The model to calculate postoperative Hct was determined based on risk factors by multiple variables regression. This development could be beneficial to better safeguard the vulnerable post-CD patients.
1. Hahn RG, Acta Anaesth Scand 2016.
2. Vricella LK, Am J Obstet Gynecol 2015.