CARDIOVASCULAR JOURNAL OF AFRICA • Volume 33, No 3, May/June 2022 104 AFRICA muscles. Tilting the probe helps to identify fascial planes. The needle is inserted in the plane, in a craniocaudal direction. The shaded area (Fig. 2) illustrates approximate interfascial LA spread between the pectoralis major and pectoralis minor muscles. The PECS II block is performed by injecting LA between the pectoralis minor muscle and SAM. PECS I and II blocks are frequently performed with a single skin puncture site by first injecting the LA in the PECS II plane, followed by needle withdrawal and injection into the PECS I plane. The site of PECS I injection affects the distribution of the block, with a more lateral injection spreading towards the axilla and blocking the intercostobrachial nerve, and a more medial injection spreading toward the midline, potentially blocking the anterior intercostal nerve branches. The PECS II blocks the long thoracic and thoracodorsal nerves and lateral cutaneous branches of the intercostal nerves, providing innervation to the SAM and lateral chest wall (Fig. 3). A recent case report discusses the use of PECS II with a continuous catheter for two patients undergoing trans-apical aortic valve implantations (TAVI).6 Randomised studies in breast surgery patients comparing PECS I/II blocks to placebo consistently demonstrate improved analgesia with the blocks. Randomised studies comparing PECS I/II blocks to the paravertebral blocks in similar patient populations show conflicting results, which differ in terms of analgesia duration and quality. This may be due to differences in the extent of surgical dissection, techniques used when performing the blocks, and the type and amount of LA injected. PECS II will block the thoracodorsal and long thoracic nerves, but spare the anterior branches of the intercostal nerves. The serratus anterior plane (SAP) block anaesthetises primarily the thoracic intercostal nerves and provides analgesia of the lateral thorax. The SAP block can be considered an extension of the PECS II block, with a more inferolateral level of injection and a wider spread. It can block the spinal nerve root at level T2 to T9, including the anterior, lateral and posterior chest wall. The efficacy is partly influenced by the volume of LA injected, as well as the injection site being deep or superficial to the SAM. Better anterior spread of the block occurs with deep injection, while the superficial injection may be preferred for a more posterior spread. Anaesthetising T1 to T8 requires a LA volume greater than 40 ml (Fig. 4). The efficacy and duration of an SAP block, PECS II block and intercostal nerve block (ICNB) for the management of postthoracotomy pain was examined in paediatric cardiac surgery patients and was found to be equally efficacious, but longest Fig. 3. Pectoral II block anatomy. Fig. 2. Pectoral I block anatomy. Fig. 4. Serratus anterior block anatomy.
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