Pain free CABG: newer horizon of minimally invasive cardiothoracic surgery a walk through anaesthesiologist perspective

Karuppiah Ramanathan, Praveen, Murshid

Department of Cardiothoracic and Vascular Anaesthesia, Kauvery HeartCity, Trichy.

Background

Significant advances in cardiac surgery followed the introduction of cardiopulmonary bypass (CPB), which was first established in the early 1950s. Over time, refinements in surgical and anaesthetic techniques combined with improved technology and the use of intraoperative transoesophageal echocardiography (TOE) have enabled less invasive approaches using smaller surgical incisions. Several different approaches can be grouped under the umbrella term ‘Minimally Invasive Cardiac Surgery’ (MICS). Today, MICS encompasses minimally invasive direct coronary artery bypass (MIDCAB), robotic-assisted cardiac surgery, atrial fibrillation (AF) ablation surgery, and minimally invasive approaches to the mitral valve, left and right atria, and aortic valve.

Case Presentation

A 55 years old diabetic male patient, who presented with complaints of exertional angina, was evaluated and found to have coronary artery disease. The echo suggested normal ejection fraction (55%) and Coronary angiography revealed double vessel disease, not amenable for percutaneous intervention. He was hence considered for CABG – minimally invasive cardiac surgery (MICS) in view of anticipated requirements of two grafts on the left circulation territory.

Patient was prepared for surgery as per unit protocol. On the day of surgery, prior to induction, thoracic paravertebral block with catheter was secured. Soon after induction invasive lines were placed. Requirement of one lung ventilation was established using COOPDECH endobronchial blocker rather than conventional DLT because of the ease in establishing one lung ventilation with the former, and confirmed using bronchoscopy.

Surgery was performed by our surgical team using a left anterior mini thoracotomy(<5 cm) incision. The CABG, off pump, beating heart, involved using Left internal mammary artery grafted to left anterior descending, and venous graft to obtuse marginal from proximal aorta.

Rest of the procedure was uneventful. Patient was shifted to CTICU with minimal ionotropic support and weaned off ventilator over the period of 6 hours as per unit protocol. Patient got extubated with stable haemodynamics after muscle recovery with adequate tone and power, and good respiratory efforts. Pain was almost negligible (Visual analogue scale-0-1/10). Subsequently supports were weaned off, and drains removed after minimal drain output. Patient started mobilising on postoperative day one with good respiratory efforts. Patient got shifted out of ICU and transferred to ward by postoperative day 3.

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Fig. 1. Difference between conventional vs MICS.

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Fig. 2. COOPDECH endobronchial blocker insitu endotracheal tube.

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Fig. 3. Positioning of the patient after induction prior to surgery.

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Fig.4. After grafting of the vessel.

Discussion

MIDCAB surgery describes a minimally invasive approach to coronary artery bypass grafting. This is usually performed using an ‘off-pump’ technique, avoiding the use of CPB and cardioplegia solution. Access is via a left anterior minithoracotomy plus additional ports, leading to faster recovery and a shorter intensive care stay. However, it is only suitable for one or two vessel coronary grafting at present, and careful patient selection is essential.

The main principles of anaesthesia for routine full sternotomy apply to a ministernotomy approach, but the limited nature of the incision does present some specific challenges of which the anaesthetist must be aware. The surgical incision typically limits surgical access but also the anaesthetist’s view of the myocardium, especially the right ventricle (RV). The use of TOE is of additional benefit to monitor contractility in the absence of a full direct view of the heart. The intact sternum may help decrease pain levels and assist in pulmonary function after surgery. With the use of continuous catheters for thoracic paravertebral block, pain is negligible. TPV block reduced the risk of developing hypotension, pruritus, urinary retention and PONV compared with thoracic epidural analgesia but was as effective in controlling pain. If femoral access for CPB is being used in case of emergency or conversion to on-pump, TOE is essential to confirm placement of wires in the correct vessels. Should cardioversion or defibrillation be required during surgery, it may be impossible to fit internal paddles through the mini sternotomy, although it is sometimes feasible to use paediatric-sized paddles. Hence, external defibrillation pads are placed before induction. As with MICS, the mini thoracotomy incision hinders the ability to rapidly reopen the chest in the setting of a postoperative cardiac arrest, with the consequential delay in delivering internal cardiac massage. Conversion to full sternotomy is a significant setback for both the patient and surgical team, because it is associated with an increased risk of bleeding and subsequent prolonged critical care admission. MICS has fewer complications – conversion to sternotomy, postoperative bleed, peripheral cannulation and vascular injury, nerve injury, complications related to one lung ventilation. It has a very important advantage- less haemodynamic disturbance while positioning the heart during grafting (on pump beating heart) and less pain, resulting in better respiratory efforts in the postoperative period, and thereby a shorter hospital stay and ERAS.

Conclusion

In the recent times MICS has taken up a newer dimension for ERAS (early recovery after surgery) over cardiac surgery through conventional sternotomy because of the longer stay in hospital due to delayed recovery, postoperative pain and reduced respiratory efforts. Thoracic PVB is an effective analgesic technique for thoracic surgery avoiding the anticoagulation related risk in regional anaesthesia, with prolonged analgesia achievable with catheter placement and local anaesthetic infusion. Ultrasound-guided approaches improve success and may potentially reduce complication rates. Newer paraspinal blocks also show promise, but more studies are required to evaluate their effectiveness.

Acknowledgement

We would like to thank Dr. Kulasekaran, Dr. T. Senthil Kumar for their valuable support in MICS programme at Kauvery HeartCity.

References

  1. Parnell A, et al. Anaesthesia for minimally invasive cardiac surgery BJA Education. 2018;18(10):323e330.
  2. Nair S, et al. Paravertebral blocks and novel alternatives. BJA Education 2020;20(5):158e165 (2020)

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