Peak Plasma Levels of Bupivacaine After a Pecto-Intercostal Fascial Block Post-Sternotomy for Cardiac Surgery
Condition: Pharmacokinetics
Study type: Observational

Summary: 
      The primary objective of the study is to measure plasma levels of bupivacaine following a
      pecto-intercostal fascial plane block (PIFB) in patients undergoing sternotomy for cardiac
      surgery.
    

Detailed description: 
      Heart disease such as ischemic cardiomyopathy and heart failure are the second leading cause
      of death and a leading cause of hospitalization in Canada. Approximately 35,000 heart valve
      or coronary artery revascularization procedures involving median sternotomy, an important
      component in the treatment of these diseases, are performed annually. Median sternotomy is
      associated with acute pain that decreases patient satisfaction, increases the risk of
      delirium, arrhythmias and respiratory complications. It also contributes to the development
      of postoperative chronic pain that can affect up to 31% of patients in the first year after
      surgery. Multimodal analgesia, combining drug therapy and regional anesthesia, can help in
      preventing acute and perhaps chronic pain in patients undergoing sternotomy for cardiac
      surgery.

      The pecto-intercostal fascial plane block (PIFB) is a new locoregional anesthesia technique
      that has emerged to treat pain following cardiac surgery including sternotomy, breast
      surgeries and sternal fractures. It consists of injecting local anesthetics in the space
      located between the major pectoralis muscle and the intercostal muscles using ultrasound
      guidance, allowing to obtain anesthesia of the territory innervated by the anterior cutaneous
      intercostal branches, i.e. the medial aspect of the breast and the sternum.

      The dose of local anesthetic injected after a PIFB should aim to maximize analgesia while
      minimizing the chance of toxic systemic concentrations. Defining the rate of absorption of
      local anesthetics into the blood after a PIFB will therefore help anesthesiologists to
      determinate optimal analgesic doses, in terms of both safety and effectiveness.

      This observational study will determine bupivacaine pharmacokinetics after a PIFB with
      bupivacaine, to further define the right dose and duration of surveillance in post-anesthesia
      care.

      Methods: Anesthesia and cardiac surgery will be initiated as usual. The use of bupivacaine by
      the anesthesiologist or surgeon will be prohibited. Following closure of the sternum, while
      the patient remains intubated and ventilated under general anesthesia with monitoring,
      including invasive blood pressure, oxygen saturation, respiratory rate and ECG, the PIFB will
      be done before application of sternal dressing and removal of sterile fields. Using an
      ultrasound machine with a high frequency linear probe (Sonosite, HFL50 15-6MHz) placed in the
      parasagittal plane, 3cm away from the midline, the fascia between the major pectoralis muscle
      and the internal intercostal muscle will be visualized. Subsequently, four injection sites,
      defined by the space between the fascia of the pectoral and intercostal muscles at the third
      and sixth intercostal spaces on each side of the patient, will be reached with an insulated
      hyperechoic needle (50-80 mm, 22 gauge, SonoPlex STIM, Nanoline, Pajunk, Germany) inserted
      cephalically and positioned in-plane.

      Following negative aspiration, the anesthesiologist will confirm the correct position of the
      needle with the fluid spread of 1 mL of 5% dextrose. Then, he will inject bupivacaine 0.25%
      with epinephrine 5 mcg/mL in 5 ml aliquots for a total dose of 2mg/kg of ideal body weight
      (maximum of 150mg or 60 mL).

      The end of injection will be considered as T0. Collection of 4.5mL of blood will be performed
      at T10min, T20min, T30min, T45min, T60min, T90min, T120min, T180min, and T240min.

      Blood tubes will be immediately placed on ice to be ultimately sent to the laboratory for
      centrifugation and measurement of bupivacaine level using liquid chromatography-tandem mass
      spectrometry (LC-MS/MS) for each of the samples.

      After the block, the patient will be transferred to the Intensive Care Unit. At T240min, if
      the patient is extubated, the level of the sensory block will be identified by the pinprick
      test.

      The time between ICU arrival and extubation, as well as the total consumption of opioids and
      co-analgesics for the first 24 hours will be recorded for each patient.
    

Intervention name(s): Collection of blood samples
Intervention type(s): Other
Intervention description(s): Nine blood samples will be collected to determine bupivacaine pharmacokinetics at T10min, T20min, T30min, T45min, T60min, T90min, T120min, T180min, and T240min. T0 will be defined as the end of bupivacaine injection.
Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Patients requiring a pecto-intercostal fascial block following cardiac surgery