Discussion
Postoperative pain can interfere adversely on respiratory function inducing an alteration of patient’s respiratory dynamics and, consequently, increasing the risk of respiratory complications especially in severe chronic obstructive pulmonary disease patients (COPD) and late extubation (2).
Although there is evidence to support a multimodal and safe approach based on regional nerve blocks (3,4), confirmations of the efficacy of PIRS block are still lacking. Cibelli et al(5) first described the effectiveness of PIRS block in intubated patient undergoing coronary artery bypass grafting, providing analgesia for sternotomy and surgical sites of chest drains, by effectively covering the T1-T10 dermatomes. The same authors, in a short letter to the editor, described the use of continuous PIRS plane block through catheters running from the epigastrium to the sternal notch bilaterally (6) in an intubated patient during surgery.
Jones et al (7) reported the combined use of continuous PIFB and RSB for a nail gun injury requiring a pericardial window followed by a full sternotomy. In this case continuous PIFB was performed prior to surgery and, after extubation in the operating room, RSB was continued in the trauma intensive care unit to better manage the uncontrolled pain coming from the inferior border of the surgical incision. Block catheters were removed on the fourth postoperative day at hospital discharge.
An interesting variation of the technique was described by Yamamoto et al (8), proposing a preoperative combination of Transversus Thoracic Plane block (TTPB) and RSB for postoperative pain relief after cardiac surgery with sternotomy in paediatric patients.
To our knowledge, PIRS block has never been used for procedures in awake cardiac surgery. However, we believe that, following the path of thoracic surgery that is increasingly evolving towards a minimally invasive approach often involving non-intubated and awake procedures(9), cardiac surgery should also take the same direction. This is especially true in surgical procedures not requiring full median sternotomies and in frail patients where orotracheal intubation poses a risk to patients.
Both PIFB and TTPB have been shown to be effective in providing analgesia of the area along the sternum blocking the anterior branches of the intercostal nerves at T2-T6 dermatomes(10). PIFB requires 3 needle punctures on each side and being more superficial, it appears to be associated with fewer risks compared with TTPB, since Transversus Thoracic Muscle it’s located closer to the pleura resulting in a greater risk of pneumothorax(11). TTPB requires a single bilateral injection on the 4th/5th intercostal space spreading to the perivascular sympathetic plexus around the internal thorax artery.
It follows that PIFB, in which the target is localized into the fascial plane between the Pectoralis Major and Intercostal muscles, seems safer than TTPB and this would be even more true in the present case. In fact, considering the surgical subxiphoid approach, a single caudo-cranial injection at T6 level provided analgesia blocking T4-T6 dermatomes, maintaining the effectiveness of the technique by reducing the number of injections needed.
RSB has also been proposed for pain management deriving from subxiphoid drainage tube in cardiac surgery: their positioning often led to continuous irritation between adjacent tissue and the tube, with consequently direct injury to the rectus abdominis muscles(2). Due to its potential to provide analgesia to dermatomes from T6 to T11, RSB has also been described in cardiac surgery for treatment of pain resulting from the Left Ventricular Assist Device (LVAD) implantation (12).
In our experience, PIRS has proven to be a safe and valid alternative analgesic strategy to general anaesthesia, avoiding the need of intubation, mechanical ventilation and high-dose opioids and their complications, such as respiratory depression, prolonged weaning and the risk of ventilator-associated infections.