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.