This is a prospective observational study testing as primary outcome if CO decreases significantly after LUD removal in patients under SA for CD.
The trial was retrospectively registered on ClinicalTrials.gov with protocol number NCT05143684 on 03/12/2021.
The Internal Ethic Committee approved the study (ID 3197, protocol N 27861/20).
Data were gathered from pregnant patients who, in addition to standard monitoring (5-lead electrocardiogram, pulse oximetry, non-invasive intermittent blood pressure, urine output), underwent perioperative non-invasive monitoring by ClearSight system on the Edwards Lifesciences HemoSphere platform (Edwards Lifesciences, Irvine, CA) at delivery suite of IRCCS Policlinico Agostino Gemelli Foundation of Rome, Italy from June 1st 2020 to July 31st 2020. The ClearSight system consists of a finger cuff positioned at the middle phalanx of the third finger of the non-dominant hand of the patient, that allows for advanced hemodynamic parameters and continuous noninvasive blood pressure.14
The parameters we evaluated from the ClearSight system for the analysis were CO, MAP, SAP, DAP, SV, SVV, HR, PPV, dP/dtmax and PPV/SVV recorded at 20 seconds-intervals.
Inclusion criteria consisted in pregnant patients at term (36th to 40th week of gestation) scheduled for elective CD under SA.
Exclusion criteria were: age <18 years, American Society of Anesthesiologists score >3, cardiac arrhythmias or aortic regurgitation, pregnancy-induced hypertension, pre-eclampsia, body mass index (BMI) > 35 kg/m2, foetal complications, coagulation disorders or contraindication to neuraxial block, emergency surgery, preoperative infection, patient’s refusal.
We considered 4 timepoints. We indicated as T1 the baseline values recorded for 5 minutes, after initial stabilization of parameters, with the patient laying down on the operating table with LUD. At T2, LUD was removed and we considered for the analysis hemodynamic data of the subsequent 5 minutes. We indicated as T3 the 5 minutes following SA with a satisfactory sensory block and as T4 the subsequent 5 minutes following LUD removal. Figure 1 summarizes the timepoints of our analysis. LUD was accomplished by positioning a wooden wedge wrapped with cotton, to make it comfortable, and medical sheets with a measured angle of 15° under the right flank of the laying down patient. In all patients, after T4 the 15° wooden wedge was positioned again and surgery was performed with LUD.
Anesthesia was delivered in sitting position using a 25-G Whitacre spinal needle, at the L3-4 vertebral interspace, with hyperbaric 0.5% bupivacaine, sufentanil 5 mcg and morphine 100 mcg. The bupivacaine dose administered was standardized according to patient’s height, as usual practice in our Institution: 8 mg for women < 160 cm tall, 9 mg for women between 160 and 170 cm, and 10 mg for those >170 cm. Once the anesthetic procedure was completed, all patients received a rapid crystalloid co-load of 7ml/kg over 10 minutes. During surgery and after delivery, fluid management was left to the attending anesthesiologist.
The attending anesthesiologist was blinded to the advanced hemodynamic parameters from the ClearSight system except for the continuous BP values. We defined hypotension as an absolute value of MAP < 65 mmHg. This value was considered as trigger for the attending anesthesiologist for the administration of norepinephrine 5 mcg. Norepinephrine boluses were repeated to reach a MAP >65mmHg. Bradycardia was defined as a heart rate of <60 bpm. Atropine 0.5 mg was administered for the treatment of bradycardia combined with hypotension, or for an absolute value of heart rate <45 bpm. After delivery, Oxytocin was administered to facilitate the uterine contraction.
We also evaluated the impact of maternal blood pressure and CO on fetal outcome collecting neonatal Apgar scores at 1 and 5 minutes after birth, and umbilical cord arterial and venous pH.
- Statistical analysis
Our primary outcome was to verify if LUD had a significant impact on CO from T3 to T4, as recorded by the non-invasive continuous hemodynamic monitoring system.
Secondary outcomes included the mean differences in hemodynamic variables (SAP, DAP, SV, SVV, HR, PPV, dP/dtmax and PPV/SVV (Eadyn) at baseline and after SA.
Repeated measure analysis of variance (ANOVA) or its non-parametric alternative Friedman test for non-normally distributed variables were used to compare patients’ longitudinal hemodynamic data from baseline until ten minutes after SA was performed. Sphericity assumption was not violated and it was assessed with the Mauchly’s test (p > 0.05). Bonferroni’s adjustments for multiple comparisons was applied for pairwise comparisons among group means.
Normally distributed continuous variables were reported as mean (± standard deviation, SD), and as median and interquartile range (IQR) those not normally distributed. Categorical variables were reported as number and percentage. Shapiro-Wilk test was used to assess normality of data distribution and the equality of variances was verified with the variance ratio test. Statistical significance level was 0.05%.
We estimated the sample size based on the CO reported in a recently published randomized controlled trial comparing patients with and without LUD during CD under SA.13 The reported mean CO 7.20±1.78 L/min in patients with LUD and 6.23 ± 1.44 L/min in patients without LUD.
Considering a significance level of 0.05 and a power of the test of 0.90 (https://clincalc.com/stats/samplesize.aspx), we estimated a minimum sample size of 35 patients to detect the same variation of CO after LUD removal. We decided to include all patients whose data were recorded and complete, who did not meet any exclusion criteria, for a total of 46 patients, to account for dropouts.