Undetectable Hypotension Episodes in Cesarean Section

The aim of the study was to test the hypothesis that whether continuous non-invasive arterial pressure (CNAP) is able to identify the hypotensive episodes that were not disclosed (or identified) in the non-invasive blood pressure (NIBP), or, detects earlier compared to NIBP in healthy pregnant women who underwent C/S under neuraxial anesthesia. We also evaluated the association between monitoring CNAP vs NIBP and outcomes as a secondary endpoint.

At least 40 participants were planned to be included in each arm, considering the unforeseen technical problems (in accordance with the "Power and Sample Size Program", the inclusion of at least 29 patients was necessary for both groups for a power 0.80, alpha 0.05 and a standard deviation of 0.04).

Healthy pregnant women at term, who were scheduled for the elective C/S under spinal anesthesia in an academic tertiary care unit between February 2014 and February 2015, comprised the study group. The exclusion criteria for the study were; 1) emergency C/S, 2) simultaneous gynecological interventions with C/S such as myomectomy, tubal ligation, placental abnormalities, etc., 3) if C/S was performed in failure of labor to progress, 4) the presence of any systemic disease, 5) preeclampsia or eclampsia, 6) drug hypersensitivity - for the ones that are used in the C/S -, 7) multiple pregnancies, 8) those pregnancies with any intrauterine fetal pathology, and 9) more than two missing consecutive NIBP readings.

Subjects were randomly assigned into 2 groups to receive either CNAP and NIBP or only NIBP. CNAP finger cuff (Infinity® CNAPTM, Dräger) was used for calibrate the device before the first measurement then calibration was repeated every 30 minutes.

In the CNAP group, the CNAP finger cuff and NIBP cuff were on the same arm of the patient while the intravenous catheter was on the contralateral side. In the control group, only oscillometric NIBP measurements were done in pregnant women similar to the study group without a CNAP.

After intrathecal injection, systolic, diastolic, and mean blood pressures were measured and were recorded manually at every minute on the CNAP monitor, and the oscillometric NIBP measurements were set at the frequency of 3 minutes for the first 15 minutes, and at 5-minute intervals thereafter, and were recorded manually.

Demographic and pregnancy-related characteristics (age, parity, gravidas of the pregnant women, weeks of gestation, and the type of fertilization [spontaneous or in vitro fertilization (IVF)] were recorded.

All parturients underwent C/S after 8 hours of fasting period without any pharmacological premedication. They were monitored with 5 lead electrocardiograms, and pulse oximetry in the operating theater. By providing the monitorization, a total of 1000ml of Ringer's lactate infusion was given by an intravenous line with an 18-gauge cannula as pre-load/co-load. A 12.5 mg of hyperbaric bupivacaine was administered to all pregnant women in the left lateral decubitus position with a 26-gauge atraumatic spinal needle at the L3-4 or L4-5 interval. After the spinal injection, the patients were placed in a supine position, and the uterus was directed to the left side by using a support under the right hip. Oxygen was given to all the parturients at 3 lt / min by nasal cannula.

The block-level was assessed by loss of sensitivity to cold. When it reached the T4 skin dermatome, the surgery was started. Motor block was determined and recorded using the modified Bromage scale (0 = no block, 1 = knee flexion possible, leg unable to lift, 2 = ankle flexion and finger movements possible, unable to move the knee, 3 = full motor block in the lower extremity). The sensitivity to cold was checked every 5 minutes and the maximum block level was recorded. Analgesia was evaluated using a visual analog scale scorer (0 = no pain, 10 = most severe pain). Time from intrathecal injection to delivery (block-delivery time), time from skin incision to delivery (skin-birth time), time from uterine incision to delivery (uterus-delivery time) were recorded.

After the baby was born, the mother was sedated with midazolam 0.03 mg/kg so that the Ramsay sedation score was 2, and analgesia was provided with fentanyl 0.5 μg/kg if necessary. As the umbilical cord was clamped, 2g of cephalosporin and 5 IU of oxytocin were administered intravenously, and 15 IU oxytocin in 1000 ml Ringer's lactate was infused in an hour.

Peri/Post-Operative Periods Patients with a thirty percent decrease in systolic blood pressure from either baseline or the measured values in the first two minutes, or with systolic blood pressure less than 90mmHg; which is considered as hypotension (13), were treated with a bolus of 200 ml Ringer's lactate solution. If blood pressure did not improve after 3 minutes, 5 mg intravenous ephedrine was administered.

A decrease in heart rate below 50 beats/min was considered as bradycardia, and 0.5mg intravenous atropine was administered when encountered.

The nausea-vomiting score was calculated as follows; the absence of nausea -0, nausea without vomiting -1, and vomiting -2 points.

Patient discomfort for non-invasive blood pressure cuff and CNAP cuff scored was as 0, 1, 2, and 3 for; no discomfort, mild discomfort, moderate discomfort, and severe discomfort, respectively.

The amount of administered intravenous fluids and ephedrine during anesthesia, the umbilical artery blood gas values, and APGAR scores at 1st minute, and at 5th minutes were also recorded.

Complications, ie, postoperative fever, bleeding, need a transfusion for blood and blood products, aspiration, atelectasis, and postspinal headache, were noted at the postoperative 24th and 48th hours. The length of stay hospital stay for the mother and baby, the requirement for intensive care unit, and/or mechanical ventilator were assessed, separately.