Undetectable Hypotension Episodes in Cesarean Section
Condition: Pregnancy Related; Anesthesia; Blood Pressure
MeSH terms: Hypotension
Study type: Observational

Summary: 
      In order to evaluate the efficacy and necessity of continuous non-invasive arterial pressure
      (CNAP) by comparing it with non-invasive blood pressure (NIBP) in order to understand whether
      it has advantages over oscillometric technique for detection of hypotensive episodes in
      healthy pregnant women who underwent cesarean section (C/S) under neuraxial anesthesia. This
      prospective study will evaluate healthy pregnant women at term, who were scheduled for
      elective C/S under spinal anesthesia. Subjects were randomly assigned into 2 groups to
      receive either CNAP and NIBP or only NIBP. A thirty percent decrease in systolic blood
      pressure from either baseline or the measured values in the first two minutes, or if the
      systolic blood pressure was less than 90mmHg, is considered hypotension. Pre-, peri- and
      post-operative specifications, newborn characteristics, and complications were recorded and
      compared.
    

Detailed description: 
      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.
    

Intervention name(s): Continuous non-invasive arterial pressure (Infinity® CNAPTM, Dräger)
Intervention type(s): Device
Intervention description(s): The basic working principle of CNAP is to keep the blood volume of the finger arteries constant by applying an exterior pressure to the vessel wall, that is done by an electronic system controlling the pressure inside a cuff around the finger. The pressure in the cuff, which is needed to keep the volume constant during arterial pulsation, corresponds to the AP.
Observational model: Other
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        The study group consisted of pregnant women at term, who were scheduled for the elective
        (planned) C/S under spinal anesthesia in an academic tertiary care unit. Subjects were
        randomly assigned into 2 groups to receive either CNAP and NIBP or only NIBP.
      
Keywords: Anesthesia; Obstetrical; Cesarean section; Arterial pressure; Blood pressure; Newborn