Fast-Track Anesthesia in Minimally Invasive Cardiac Surgery: Dexmedetomidine and Erector Spinae Plane Block vs Opioid-Based Anesthesia

Enhanced Recovery After Surgery (ERAS) pathways have transformed perioperative care by implementing patient-centered, evidence-based protocols that improve outcomes while reducing hospital length of stay (HLOS) and healthcare expenditure \[1\]. In cardiac surgery, ERAS has driven the transition from conventional prolonged postoperative mechanical ventilation toward fast-track extubation (FTE) strategies \[1,2\].

Traditionally, cardiac anesthesia relied on high-dose opioid techniques (e.g., fentanyl 50-100 mcg/kg) combined with overnight ventilation to suppress surgical stress responses and maintain hemodynamic stability \[2\]. Although effective for these goals, this approach is associated with respiratory depression, delayed emergence, prolonged ICU stay, postoperative nausea and vomiting (PONV), ileus, delirium, and increased healthcare costs \[1,3\].

Fast-track cardiac anesthesia (FTCA) aims to achieve extubation within 6-8 hours after surgery, promoting earlier mobilization, faster oral intake, and reduced ICU-acquired weakness \[1\]. Evidence from a 2016 Cochrane review demonstrated that low-dose opioid FTCA provides comparable mortality, reintubation, and major complication rates to traditional high-dose regimens while significantly shortening ICU stay \[2\]. Modern protocols report successful extubation within 4-6 hours in more than 60% of elective cardiac surgery patients, with mean ICU stay around 31 hours \[4\].

Successful implementation of FTE depends on three core elements: (1) appropriate patient selection (EuroSCORE II \<4%, LVEF ≥45%, absence of severe pulmonary disease), (2) optimized intraoperative management including reduced cardiopulmonary bypass (CPB) duration and careful inotrope use, and (3) structured postoperative weaning pathways \[1\].

Despite FTCA benefits, opioids remain the dominant perioperative analgesic strategy. High intraoperative opioid exposure suppresses respiratory drive, delaying extubation and increasing aspiration risk \[2\]. Postoperative opioid-related complications-including PONV (20-30% incidence), ileus, urinary retention, delirium, and pruritus-extend hospitalization and decrease patient satisfaction \[1,3\].

Additional concerns include opioid-induced immunosuppression potentially increasing infection risk after CPB and opioid-induced hyperalgesia and tolerance complicating postoperative analgesia, especially in opioid-naïve patients \[6\]. These concerns, together with the ongoing opioid epidemic, reinforce the need to minimize perioperative opioid exposure in alignment with ERAS principles \[1\].

Dexmedetomidine is a highly selective α2-adrenergic agonist (α2:α1 selectivity ratio 1620:1) providing sedation, anxiolysis, and analgesia without clinically significant respiratory depression \[3\].

In cardiac surgery, dexmedetomidine offers several advantages:

* Hemodynamic stability: attenuates sympathoadrenal responses during laryngoscopy and intubation without tachycardia; a preoperative dose of 0.5 mcg/kg effectively reduces heart rate and blood pressure surges \[3\]. * Myocardial protection: lowers myocardial oxygen consumption and may reduce postoperative troponin release compared with propofol-based anesthesia. * Delirium prevention: associated with reduced postoperative delirium incidence, particularly relevant because prolonged ventilation independently increases delirium risk. * Opioid-sparing effect: decreases perioperative opioid requirements by approximately 30-50% \[3\].

Importantly, preservation of respiratory drive makes dexmedetomidine particularly suitable for FTCA protocols where early extubation is a primary objective \[3\].

Introduced by Forero et al. in 2016 for thoracic neuropathic pain, ESPB has emerged as a simple, safe, and effective fascial plane block \[5\]. Local anesthetic injected between the transverse process and erector spinae muscle spreads craniocaudally, reaching dorsal and ventral spinal nerve rami from T1-T12 \[1\].

Compared with thoracic epidural or paravertebral approaches, ESPB provides several advantages in cardiac surgery:

* Improved safety: minimal risk of spinal hematoma in anticoagulated patients, lower pneumothorax risk, and avoidance of sympathectomy-related hypotension \[6\]. * Technical simplicity: ultrasound guidance permits real-time identification of anatomical landmarks while avoiding neural and vascular structures \[6\]. * Bilateral applicability: suitable for median sternotomy and minimally invasive cardiac surgery (MICS) requiring bilateral analgesia \[7\].

Clinical evidence supports its analgesic efficacy. A randomized study in minimally invasive coronary artery bypass grafting (MIDCAB) demonstrated a 70% reduction in intraoperative fentanyl use (0.9 mg vs. 3.0 mg; p\<0.01), reduced norepinephrine requirements, and prolonged opioid-free analgesia for 34 hours postoperatively \[8\]. Additional randomized evidence in MICS confirmed lower postoperative opioid consumption and improved pain control compared with local infiltration techniques \[9\].

Combining dexmedetomidine with local anesthetics may extend block duration through two complementary mechanisms:

1. Local vasoconstriction: reducing anesthetic washout from the injection site. 2. Direct analgesic action: activation of peripheral and dorsal root ganglion α2 receptors, suppressing nociceptive transmission \[7\].

A current randomized study (NCT06981949) is evaluating whether bilateral ESPB using dexmedetomidine (0.5 mcg/kg per side) with ropivacaine 0.375% prolongs analgesia and further reduces opioid requirements compared with ropivacaine alone \[7\].

MICS includes procedures performed through limited-access approaches such as mini-thoracotomy, mini-sternotomy, or port-access techniques instead of full median sternotomy. Compared with conventional cardiac surgery, MICS reduces tissue trauma, postoperative pain, recovery time, and hospitalization duration \[1,8\]. Nevertheless, effective analgesia remains challenging because of chest tubes, rib retraction, and pleurotomy.

Because MICS patients generally have lower operative risk (lower EuroSCORE), reduced tissue injury, and fewer contraindications to ESPB, this population represents an ideal setting to evaluate a combined dexmedetomidine-ESPB opioid-sparing fast-track extubation strategy \[9\].

• Total Intraoperative Opioid Consumption [Time frame: During surgery]
• Postoperative Opioid Consumption [Time frame: 2, 6, 12, 24, and 48 hours after extubation.]