Association Between Preoperative Shock Index and Hypotension After Spinal Anaesthesia for Non- Elective Caesarean Section
Condition: Hypotension
MeSH terms: Hypotension
Study type: Observational

Summary: 
      This is a prospective observational study done in parturient planned for non-elective
      caesarean section. Association between shock index (HR/SBP) and post-spinal hypotension in
      parturient undergoing non-elective caesarean section will be evaluated in this research.
    

Detailed description: 
      Studies have shown that early hypovolemia is insufficient to produce changes in orthostatic
      heart rate (HR) or systolic blood pressure (SBP). Studies have shown that Shock Index (SI) as
      a useful indicator for acute hypovolemia. In healthy individuals, acute blood loss less than
      450 mL rarely produces abnormal HR or SBP. As, several studies have shown that relationship
      of baseline heart rate and systolic blood pressure in predicting post spinal hypotension,
      this study aims to incorporate both the parameters and attempt to develop a single effective
      predictor for post spinal hypotension in the form of SI.

      Methodology After approval from Institutional Review committee of B.P. Koirala Institute of
      Health Sciences, parturient undergoing non-elective caesarian of ASA PS grade II and urgency
      category 2 and 3, fulfilling the inclusion criteria will be informed about the study and
      written consent will be obtained either in labour room or in obstetric emergency ward. During
      this visit patient's data that includes age, indication of caesarean section, preoperative
      anxiety (APAIS), gestational age, and duration of fasting, height, weight, BMI and
      preoperative hemoglobin concentration will be recorded.

      The study will be conducted in accordance with the ethical principles of the 1964 Declaration
      of Helsinki and STROBE (Strengthening the Reporting of Observational studies in Epidemiology)
      guidelines will be followed. Before patient is shifted to the operating room (OR), ranitidine
      50 mg and metoclopramide 10 mg will be administered intravenously via 18 G cannula. The
      patient will be shifted to operating table and standard monitors 3 lead ECG, pulse oximetry
      and noninvasive blood pressure will be attached. Baseline vital signs heart rate and
      noninvasive SBP will be recorded in operation theatre in supine position with 15° left
      lateral tilt before administering spinal anaesthesia. NIBP will be measured by using cuff
      size with width of cuff bladder covering at least 40% of arm circumference and length at
      least 80% and will be measured from EDAN elite V8 monitors. 3 measurements of SBP will be
      recorded at 1 minute interval and its mean value will be taken as baseline SBP.

      Also, shock index (HR/ SBP) will be calculated before administering spinal anaesthesia. At
      every 1 minute interval until delivery of baby, vitals parameters HR, SBP and MAP will be
      measured and shock index will be calculated in each time interval. Then, the patient will be
      placed in sitting position. Under all aseptic precautions, 2.2 ml of 0.5% hyperbaric
      bupivacaine with 10 µg fentanyl will be administered in sitting position in L4- L5 or L3- L4
      interspace after confirmation of free flow of CSF with 25 G Quincke's needle and drug will be
      injected over 20 secs. Patient will be then immediately put into supine position with a right
      hip wedge. A 1 L co-loading of Ringer's lactate will be administered rapidly within 10
      minutes via an 18 G intravenous line after administering spinal anaesthesia.
      Phenylepinephrine infusion will be started at 25 microgram/min immediately after the spinal
      injection. The sensory level of anaesthesia will be checked using loss of cold sensation with
      the use of alcohol soaked cotton swabs every minute until 20 mins. Surgery will be allowed
      once the bilateral sensory block height at T6 is achieved. Oxygen at 40% will be administered
      via nasal cannula at 2-4 L/min until delivery.

      Hemodynamic parameters will be recorded at following time intervals: baseline, immediately
      after spinal anaesthesia, every minute for the first 15 minutes after spinal injection and
      every 2.5 mins until end of surgery. Hypotension will be treated with phenylephrine 50 µg
      bolus and rapid infusion of Ringer's lactate 200 ml. If bradycardia (HR< 55/min) is
      associated with hypotension, IV ephedrine 6 mg will be administered. If these measures fail
      and bradycardia is still persistent then an IV atropine 0.5 mg will be given. Intraoperative
      hypertension (defined as SBP greater than 120% of the baseline reading) will be managed by
      stopping norepinephrine infusion. The infusion will be resumed when blood pressure returns to
      the upper limit of the target range i.e. 20% above baseline.After delivery of the baby, 3 IU
      of oxytocin will be administered IV over ≥ 30 sec followed by an infusion of 10 IU/hr
      (oxytocin 40 IU in 500 ml of Hartmann's solution).

      The total amount of intraoperative IV fluids administered and estimated blood loss will be
      measured. At the conclusion of the surgery, blood loss will be estimated by cumulative
      measurement of the following: the volume of blood in the suction canister (and subtracting
      the estimated amniotic fluid from the suction chamber); visual examination of the surgical
      sponges.

      Intraoperative use of other uterotonic agent or blood transfusion will be recorded. The
      attending pediatrician will assess neonatal Apgar scores at 1 and 5 minutes after delivery.

      Patients will be asked to report the occurrence of intraoperative nausea Incidence of
      intraoperative pruritus, shivering, and dizziness will also be recorded.

      The primary outcome measures will be incidence of post spinal hypotension defined as SBP <
      80% of baseline reading or SBP < 100 mmHg after administering of spinal anaesthesia until
      delivery of baby. The secondary outcome measures will be post-delivery hypotension is defined
      as SBP < 80% of baseline reading or SBP < 100 mmHg observed from starting oxytocin until end
      of surgery.

      Data collection Baseline data (gestational age, preoperative hemoglobin, preoperative
      anxiety, uterine incision to delivery time, hemodynamic parameters) and outcome parameters
      will be collected in the paper case record form and entered in windows Microsoft excel
      spreadsheet and will use STATA version 15.0 for analysis.
    

Observational model: Case-Only
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Patients at term undergoing emergency caesarean delivery and falling under category 2 (no
        immediate threat to life of pregnant women and fetus) and category 3 (requiring early
        delivery) according to NICE (National Institute for Clinical Excellence) guideline
        classification of urgency of emergency caesarean section and ASA (American society of
        Anaesthesiologist) PS (Physical status) grade II under spinal anesthesia will be included.
      
Keywords: cesarean section; hypotension; spinal anesthesia; shock index; post spinal hypotension; non-elective cesarean section