The Effect of HPI to Reduce Intraoperative Hypotension in Caesarean Sections

Hypotension Prediction Index (HPI) has been shown to reduce IOH significantly in non-cardiac and major abdominal surgeries.The role of HPI beyond reducing IOH has also been a subject of research. Andrzejeska et al. demonstrated that the use of HPI in adolescent idiopathic scoliosis surgery leads to lower reductions in post-surgery haemoglobin levels, shorter duration of hypotension and shorter hospital admissions. Additionally, the intervention group had shorter timeframes from the end of surgery to extubation.

The development of a non-invasive finger blood pressure device compatible with HPI called the Acumen IQ cuff, made it possible to use HPI without inserting an arterial catheter. The arterial pressure waveform generated by a non-invasive finger cuff was reliable and in agreement with the radial artery blood pressure. A retrospective analysis was conducted by Frassanito et al. to determine the performance of HPI using arterial waveform recorded by a non-invasive finger probe to predict hypotension in patients undergoing CS under spinal anaesthesia. They have found that HPI, using this non-invasive probe, was able to predict hypotension with a sensitivity and specificity of 83% and 83% at 3 minutes, 97% and 97% at 2 minutes, and 100% and 100% at 1 minute, before it occurs.

This study aims to determine if the solution to reduce IOH lies in predicting intraoperative hypotension during lower segment ceaserean section (CS). The benefits of HPI may extend beyond reducing the incidence and severity of IOH, to bringing positive outcomes to the foetus. This study will determine whether integrating an early warning system produces benefits significant enough to justify changing our anaesthetic practice.

PROBLEM STATEMENT

Varying methods have been utilised to reduce IOH in CS. A novel software, HPI, was developed to predict hypotension, enabling clinicians to institute guided treatment before maternal hypotension occurs. The investigator need to determine if HPI has benefits in CS, thus leading to better maternal and neonatal outcomes.

RESEARCH QUESTION

Can HPI using the non-invasive continuous arterial pressure waveforms reduce the duration and severity of hypotension in patients undergoing CS under spinal anaesthesia?

OBJECTIVES

Study objective:

To determine if HPI has benefits in CS, thus leading to better maternal and neonatal outcomes compared to oNIBP.

Primary outcome:

The duration and severity of hypotensive events reported as a time-weighted average (TWA) - MAP < 65 mmHg in HPI group (intervention) versus standard oNIBP.

Secondary outcomes:

• To determine whether the use of HPI leads to better maternal outcomes (incidence of nausea and vomiting, blood loss, length of hospital stay, maternal satisfaction, incidence of surgical site infection)
• To determine whether the use of HPI leads to better foetal outcomes (Apgar scores, umbilical cord pH, length of hospital stay)
• To determine the amount of vasopressors and inotropes administered throughout CS if HPI is used versus conventional oNIBP monitoring

RESEARCH HYPOTHESIS

Additional parameters from HPI in the CS under spinal anaesthesia will reduce the duration and severity of intraoperative hypotension and provide better maternal and neonatal outcomes.

Inclusion criteria

• ≥ 37 weeks of gestation
• Elective CS
• Age between 18 - 40 years old
• Singleton pregnancy
• Planned for spinal anaesthesia

Exclusion criteria

• American Society of Anesthesiologists (ASA) III and above
• Body mass index (BMI) ≥ 40 kg/m2
• Increased risk of developing peripartum haemorrhage
• History of peripartum haemorrhage
• Placenta previa major, accrete, increta, percreta
• Gravida ≥ 5
• Presence of large uterine fibroids
• Congenital bleeding disorders such as Haemophilia A, Haemophilia B and Von Willebrand disease
• Acquired bleeding disorders such as thrombocytopenia and coagulopathy
• Contraindications to finger cuff orNIBP application, such as finger ischaemia, upper limb neurological deficit, discoloured nail
• Cardiac arrhythmias and aortic regurgitation
• Patient's refusal