Cardiac Effects of Oxytocin Administrated During Cesarean Section, Signs of Myocardial Ischemia
Condition: Myocardial Ischemia; Hypotension; Bloodloss
MeSH terms: Hypotension; Myocardial Ischemia; Coronary Artery Disease; Ischemia
Study type: Interventional
Phase: Phase 4

Summary: 
      Oxytocin has cardio vascular effects as hypotension, tachycardia and possibly coronary spasm.
      The uterotonic effect of the drug is used during cesarean section, to minimize blood loss.ECG
      changes suggestive of cardiac ischemia (ST depression) has been showed in previous studies of
      patients undergoing cesarean section i regional anaesthesia. The effect of oxytocin on this
      outcome has not been investigated to any extent.

      In the current study, we tested the hypothesis that there was no difference in occurrence of
      ECG changes (ST segment depression) between two doses of oxytocin. Participants were
      randomized to receive either 5 or 10 units of oxytocin in a double blinded fashion.

      Main outcome measure is occurrence of significant ST depression on ECG. Secondary outcome
      measures are mean arterial pressure, heart rate, blood loss, symptoms as chest pain,
      shortness of breath and feeling of heaviness on the chest.
    

Detailed description: 
      All healthy term participants scheduled to undergo elective caesarean section under spinal
      anaesthesia at the Department of Obstetrics and Gynecology, University Hospital, Uppsala
      Sweden and who were > 18 years old, were candidates for inclusion in the study. .

      The study was approved by the regional ethics committee and informed written consent was
      obtained from each participant.

      ECGs were recorded by continuous ambulatory ECG (Holter) monitoring (GE Medical systems
      SEER/MARS, UK) during the peroperative period utilizing leads V3, V5 and avF. As secondary
      outcomes, symptoms as chest pain, shortness of breath and feeling of heaviness on the chest
      and, Troponin I levels 12 hours postoperatively, were recorded. Also, as secondary outcomes,
      differences in blood pressure, heart rate, and blood loss were measured.

      Before induction of anaesthesia, patients received 1000 mL of lactated Ringer's solution
      intravenously. Thereafter an additional 500-1000 mL of lactated Ringer's solution or 500 mL
      Hydroxyethyl starch was infused if considered needed by the anaesthesiologist.

      Spinal anaesthesia was established in the sitting position at lumbal interspace L2/L3 or
      L3/L4. Non invasive blood pressure (systolic, diastolic and mean arterial pressure, MAP) and
      heart rate was monitored every 2 minutes, throughout surgery. Oxytocin was given as an
      intravenous bolus dose immediately after clamping of the umbilical cord. Blood loss during
      the operation was estimated and recorded. During surgery, any spontaneous complaints by the
      patients of symptoms as chest pain, shortness of breath and feeling of heaviness on the
      chest, was recorded as well as duration of symptoms. Episodes of chest pain were assessed
      with the visual analogue scale (VAS).

      Troponin I, as a marker of ischemic myocardial damage, was sampled 12 hours postoperatively.

      The incidence of ECG changes related to different doses of intravenous bolus doses of
      oxytocin (5 and 10 units) during caesarean section is unknown. In a pilot study preceding the
      present study, 5 units oxytocin were administrated and the incidence of ECG changes was 15%.
      With the assumption that ECG changes could occur in 50% of subjects receiving 10 units
      oxytocin and based on 0.8 power to detect a significant difference (P = 0.05, two-sided), 25
      patients were required for each study group. An interim analysis performed after inclusion of
      50 patients revealed that ECG-changes occured in 8 and 24 % respectively in the two groups of
      5 and 10 units of oxytocin. An additional 50 patients were allocated and a second interim
      analysis planned.

      A computer-generated randomisation list with block of four was drawn up by a statistician and
      given to the pharmacy department who performed the randomisation. The procedure ensured
      allocation concealment.

      All participants, health care providers, investigators and other persons (cardiologist) were
      blinded to treatment assignment for the duration of the study.

      The Statistical Package for Social Sciences (SPSS) for Windows, version 15.0, was used (SPSS,
      Inc., Chicago, IL, USA). To compare group distributions the chi-squared test or Fisher's
      exact test was applied and the Mann-Whitney U-test or t-test for continuous variables. A
      p-value < 0.05 was considered to indicate a significant difference
    

Intervention name(s): oxytocin; oxytocin
Intervention type(s): Drug; Drug
Intervention description(s): oxytocin 5 units diluted with normal saline to a total volume of 10 mL; oxytocin 10 units diluted with normal saline to at total volume of 10 mL.
Other intervention name(s): syntocinon; Pitcotin; Syntocinon; Pitcotin
Intervention MeSH terms: Oxytocin
Allocation: Randomized
Intervention model: Single Group Assignment
Masking: Triple (Participant, Care Provider, Investigator)
Primary purpose: Treatment
Keywords: oxytocin; ST depression; cesarean section; blood loss