Ultrasound-Guided Regional Anaesthesia for Abdominal Surgery

INTRODUCTION Abdominal surgery has seen lots of advances in recent times. The focus of abdominal surgeries has shifted now towards enhanced recovery of the patient after the surgery. Post-operative analgesia is an essential component of most enhanced recovery after surgery (ERAS) pathways. Their effective implementation contribute towards improving patient outcomes.[1] The application of ultrasound in regional anaesthesia has led to the introduction of newer blocks to be performed more easily and accurately with better reproducibility. The innovations in regional anaesthesia have helped in providing better analgesia and post-operative recovery to the patient. ADVANTAGES OF USING REGIONAL ANAESTHESIA Regional anaesthesia provides better pain relief as compared to opioids.[2] Better pain control helps in avoiding negative physiological effects due to inadequate analgesia. The advantages of regional anaesthesia are summarised in Table 1.[3]Table 1: Advantages of regional anaesthesiaA recent meta-analysis by Smith et al. suggested that the use of regional anaesthesia reduces the possibility of intensive care unit admission which is probably related to the decrease in pulmonary complications. Regional anaesthesia also helps in reducing the length of stay and unanticipated admission after day care surgery.[4] All these factors ultimately lead to decrease in healthcare cost. Regional anaesthesia plays a pivotal role during abdominal surgery. ANATOMY OF ABDOMINAL CAVITY The abdomen extends from the ribs above to the pelvis below. The main function of the abdominal wall is to protect the abdominal viscera from the external environment. The abdominal wall is divided into two parts: the anterolateral and the posterior abdominal wall. The anterolateral abdominal wall is made up of nine layers. From superficial to deep, they are the skin, the membranous layer of superficial fascia (Scarpas fascia), the fatty layer of superficial fascia (Campers fascia), external oblique muscle, internal oblique muscle, transversus abdominis muscle, transversalis fascia, extra peritoneal fascia and the parietal peritoneum[5] [Figure 1].Figure 1: Various layers of anterior abdominal wall. IOM: Internal oblique muscleThe ventral rami of thoracic nerves T7–T12 pass inferomedially and give lateral cutaneous branch before they reach the mid axillary line.[6] The intercostal nerves then continue forward passing deep to the costal cartilage and enter in the plane between transversus abdominis and internal oblique muscles. At the lateral edge of the rectus sheath, they pass behind the rectus abdominis muscle. As they approach midline, they give anterior cutaneous branch which pierces the rectus abdominis muscle and the anterior wall of the rectus sheath to provide cutaneous innervation [Figure 2].Figure 2: Nerve supply of the anterior abdominal wallThe spinal nerves T7–T12 and L1 supply the skin, muscles and the parietal peritoneum of the anterior abdominal wall in a segmental distribution (T7–T9 xiphoid process to umbilicus, T10 around the umbilicus, T11–L1 from umbilicus to pubic region). The ventral rami of thoracic nerves T5 and T6 in addition supply the external oblique muscle in the upper part. The cutaneous area over the xiphoid is supplied by the T6 ventral rami. The ilioinguinal nerve and the iliohypogastric nerve which are the branches of the lumbar plexus also pass through the plane between the internal oblique and the transversus abdominis muscle. The ilioinguinal nerve in addition supplies the anterior surface of the scrotum and the labia majora. It also gives small cutaneous branches to the anterior aspect of the thigh.[5] The parietal peritoneum receives innervation from the somatic afferents carried by the associated spinal nerves. The visceral peritoneum receives visceral afferents that accompany the autonomic nerves back to the central nervous system. Visceral nerve supply of the abdomen Visceral innervation to the abdomen is through the prevertebral plexus that is present around the aorta and is continuous onto its major branches. These include the celiac plexus, the aortic plexus, the superior hypogastric plexus, and the inferior hypogastric plexus. These plexuses receive pre-ganglionic sympathetic and visceral afferents fibres from the thoracic and lumbar splanchnic nerves; pre-ganglionic parasympathetic and visceral afferents from the vagus nerve; and pre-ganglionic parasympathetic fibres from the pelvic splanchnic nerves.[5] Visceral sensory fibres generally parallel the motor pathway [Figure 3].Figure 3: Visceral nerve supply of the abdomenThe posterior abdominal wall has two fasciae: the thoracolumbar fascia (TLF) and the psoas fascia. The TLF has three layers: anterior, middle and the posterior layers. The anterior layer attaches to the transverse process of lumbar vertebrae – superiorly it forms the medial and the lateral arcuate ligament of the diaphragm – and is continuous with the endothoracic fascia, inferiorly it is attached to the iliac crest.[7] It covers the anterior surface of the quadratus lumborum (QL) and the psoas major muscles. The middle layer attaches to the transverse process of the lumbar vertebrae and the intertransverse ligament, superiorly it is attached to the 12th rib while inferiorly it is attached to the iliac crest. It covers the posterior layer of the QL muscle.[7] The posterior layer of the TLF covers the posterior surface of the erector spinae (ES) muscle. It is attached to the tip of the spinous process and the supraspinous ligament medially. The posterior layer of the TLF extends all the way up to the neck. The posterior and middle layers of the fascia join at the lateral border of the ES muscle to form the lateral raphe.[7] This layer is in turn joined by the anterior layer of the TLF at the lateral end of QL muscle to form the aponeurotic origin of the transversus abdominis muscle [Figure 4]. Lateral interfascial triangle (LIFT) is formed between the ES and the QL muscle.[8] The base of this triangle is formed by the lateral border of ES muscle, the posterior and middle layers of TLF form the sides of this triangle while the apex is formed by the lateral raphe.[6] The ilioinguinal, iliohypogastric and the subcostal nerves pass between the QL and the transversalis fascia before entering the transversus abdominis plane (TAP).[6]Figure 4: Thoracolumbar fascia and the adjoining structures. EOM: External oblique muscle, IOM: Internal oblique muscle, TLF: Thoracolumbar fascia, LIFT: Lateral interfascial triangle, ESP: Erector spinae muscleABDOMINAL1 INCISIONS Various types of abdominal incisions have been described in the literature for performing laparotomy. An ideal incision should be able to provide sufficient space to the surgeon to perform the procedure, it should allow the surgeon to extend the incision if required and should not interfere with the strength and function of the abdominal wall.[9] More than 10 types of incisions have been described in the literature.[10] The most commonly performed incisions are depicted in Figure 5.Figure 5: Abdominal incisionsREGIONAL ANAESTHESIA TECHNIQUES Transversus abdominis plane block As discussed in the anatomy section, the thoracic spinal nerves that supply the skin of the abdomen and the parietal peritoneum travel through the plane between the internal oblique and the transversus abdominis muscle. These nerves communicate with each other to form the upper and the lower TAP plexus. So by depositing local anaesthetic in the plane between these two muscles, one can block the sensations carried by these nerves. As these are interfascial plane blocks, one needs to deposit at least 15–20 mL of local anaesthetic (LA) to achieve the desired effect. Various approaches to give TAP block have been described in the literature. Subcostal transversus abdominis plane block Herein a linear high-frequency transducer is placed just below the lower margin of the lower rib in a direction that is parallel to the ribs. The probe is placed as high and as medially as possible. The rectus abdominis, the posterior rectus sheath and the transverse abdominis muscles are identified. The needle is then advanced in a medial to lateral direction to target the plane between the rectus sheath and the transverse abdominis muscle [Figures 6 and 7a, b]. This approach usually blocks the sensations carried by the intercostal nerves T6–T9.[6,7] It is mostly used for providing analgesia for surgeries above the umbilicus. The analgesia provided by this block is usually restricted to the medial part of the abdomen and there can be sparing of the lateral wall of the abdomen.[11]Figure 6: Ultrasound position for subcostal TAP block. TAP: Transversus abdominis planeFigure 7: (a) Ultrasound image showing various structures encountered during subcostal TAP block (b) Various positions of transducer for giving (1) Subcostal TAP block, (2) Lateral TAP block, (3) Posterior TAP block. Red line with arrow indicates direction of needle insertion. TA: Transversus abdominis, IO: Internal oblique, EO: External oblique. TAP: Transversus abdominis planeOblique subcostal transversus abdominis plane block This is a modified subcostal approach, wherein the needle is first introduced as in subcostal approach; the TAP plane is identified and this plane is hydro-dissected along the subcostal line from the xiphoid process towards the iliac crest. This technique was described by Hebbard et al. and has the advantage that through the single needle insertion, T6–L1 spinal segments can be blocked.[12] Lateral transversus abdominis plane block In this approach, a linear high frequency transducer is placed in the mid axillary line between the costal margin and the iliac crest. The plane between the internal oblique and transversus abdominis muscle is identified and the needle is directed so that the tip of the needle reaches the plane between the two muscles. Local anaesthetic is then deposited in this interfacial plane. This block anaesthetises the area supplied by the intercostal nerves T10–T11 and the subcostal nerve T12. The L1 spinal nerves are not blocked using this approach. They have to be separately blocked using anterior TAP block [Figures 7b, 8 and 9a].Figure 8: Ultrasound position for lateral TAP block. TAP: Transversus abdominis planeFigure 9: (a) Ultrasound image of the various structures encountered during Lateral TAP block. (b) Transducer position for giving Rectus Sheath block and Anterior TAP block. Red line indicates direction of needle insertion. TA: Transversus abdominis, IO: Internal oblique, EO: External oblique, TAP Plane: Transversus abdominis planeAnterior transversus abdominis plane block While giving this block, a linear high-frequency transducer is placed medial to the anterior superior iliac spine. The transducer is slightly tilted towards the opposite rib cage, the plane between the internal oblique and the transversus abdominis muscle is identified. The tip of the needle is targeted towards this plane. Once the needle reaches this plane, local anaesthetic is deposited [Figure 9b]. Posterior transversus abdominis plane block Since the lateral cutaneous branches of the spinal nerves leave the TAP before the posterior axillary line, it was postulated that giving the TAP block more posteriorly will provide better analgesia to the lateral wall.[6] In this approach, a linear transducer is first placed in the mid axillary line between the costal margin and the iliac crest. The transducer is then moved posteriorly till the most posterior limit of transversus abdominis muscle is reached. The needle is then introduced to target the TAP plane at its most posterior end [Figures 7b, 10 and 11].Figure 10: Ultrasound position for posterior TAP block. TAP: Transversus abdominis planeFigure 11: Ultrasound image of the various structures encountered during Posterior TAP block. TA: Transversus abdominis, IO: Internal oblique, EO: External oblique, TAP Plane: Transversus abdominis plane, POS TAP plane: Site for insertion of needle through posterior approach for Posterior TAP blockThe disadvantage of TAP block is that since it blocks only the somatic nerves, it does not provide analgesia in abdominal surgeries where there is dissection of the viscera. QUADRATUS LUMBORUM BLOCK Lateral quadratus lumborum block (quadratus lumborum 1 block) The patient is placed laterally with the side to be blocked lying superiorly. A linear transducer is placed horizontally in the mid axillary line between the costal margins and the iliac crest. The transducer is then gradually moved posteriorly till the posterior aponeurosis of transverses abdominis muscle is seen. The tip of the needle is then inserted to target the space between the posterior aponeurosis and the transversalis fascia just lateral to the QL muscle. This approach consistently blocks the lateral cutaneous branches of the ilioinguinal, iliohypogastric and the subcostal nerves.[8] This block is mainly used for surgeries below the umbilicus.[8] Posterior quadratus lumborum block (quadratus lumborum 2 block) In this block, a linear transducer is placed in the same manner as in QL1 block. The transducer is again moved posteriorly till LIFT is visualised. The needle is then directed towards the middle layer of TLF close to the LIFT. Local anaesthetic is injected in the middle layer of TLF between the ES and the quadratus lumborum muscle. This block provides analgesia for abdominal surgeries both above and below the umbilicus. The mechanism of action of QL2 block is not clear but usually dermatomes from T4 to L1 are covered by this block.[8] This block provides faster analgesia with almost equal distribution of anesthesia as compared to the transmuscular QL block. Anterior quadratus lumborum block (transmuscular quadratus lumborum block) A curvilinear low frequency or a linear high-frequency probe (depending on the patient’s build) is placed horizontally in the patients flank just cephalad to the iliac crest. The acoustic image seen forms a ‘shamrock sign’ wherein the transverse process of the L4 vertebra forms the stem, while the psoas major anteriorly, the QL in the middle and the ES posteriorly form the leaves of the shamrock. The needle is inserted in plane from posterior to anterior direction to target the plane between the QL and the psoas. This block again provides analgesia for abdominal surgeries both above and below the umbilicus. The dermatomal spread seen with this block can extend from T4 to L1 [Figures 12, 13 and 14a, b].Figure 12: Ultrasound position for quadratus lumborum blockFigure 13: Ultrasound image of the various structures encountered during the QL block using shamrock approach. QL: Quadratus lumborum, TP: Transverse process, ESP: Erector spinae muscleFigure 14: (a) Plane of deposition of LA in various types of QL block. (b) Position of transducer for giving QL block in the lateral position. Red line indicates the direction of needle insertion from anterior to posterior for giving lateral QL and from posterior to anterior for giving Anterior and Posterior QL blocks. QL: Quadratus lumborum, LA: Local anesthetic, TAP: Transversus abdominis planeThe probable mechanism of action of this block is by spread of the drug along the transversalis fascia to the endothoracic fascia and then to the thoracic paravertebral space. The exact mechanism of action of QL block is still not clear. As discussed in the anatomy section, the anterior layer of TLF is continuous cranially with the endothoracic fascia and laterally it merges with the transversalis fascia. One of the proposed mechanism of action of the QL block is that the drug when injected in the anterior layer of TLF traverses upwards and reaches the endothoracic fascia and blocks the somatic nerves and the thoracic sympathetic nerves at the lower thoracic vertebral levels. This has been by by et and et where they that the drug to the lower thoracic levels. et al. also the spread of the drug to the lower thoracic when posterior QL block was mechanism of action is by spread of the drug to the lumbar plexus. It has also been suggested that the drug when injected in the middle layer of the TLF that behind the QL muscle the sympathetic nerves that pass through this plane and sympathetic block, the mechanism of action of posterior QL All these probably the somatic as as visceral analgesia after QL block. One should be while giving QL block as the lower of the reaches till L4 on deep So the anterior to QL muscle with only the the transversalis fascia and the anterior layer of TLF the from the QL muscle. The lumbar on each side also pass posterior to the QL muscle between QL and ES while giving this block, one should be to not LA of before the drug can in avoiding As described QL block can be used for abdominal surgeries both above and below the umbilicus. Various surgeries where QL block can be used include iliac BLOCK This block is for surgeries around the of the it provides only somatic pain relief and does not provide visceral The spinal nerves pass through the plane between the transversus abdominis and internal oblique. They the lateral margin of rectus sheath to posterior to the rectus abdominis muscle. The nerves then travel the rectus abdominis muscle to supply the anterior wall of the A linear high frequency transducer is placed in the in a transverse just above the umbilicus to and the rectus abdominis muscle. below the rectus muscle, one can the transversalis fascia. The needle is then introduced in plane from lateral to medial direction to between the rectus abdominis muscle and posterior rectus mL of LA is then deposited in this plane on each giving the one should the on as superior and inferior can be present in this One should also be the peritoneum that just below the transversalis fascia, so the tip of the needle should be and should not the posterior aspect of the transversalis fascia. The position of the transducer and the needle insertion can be in a direction as the of the of the block at the of the incision helps in better of the dermatomes Rectus sheath block should not be below the of arcuate line as posterior rectus sheath is below the arcuate Rectus sheath can also be placed and for continuous of LA for post-operative [Figures and Ultrasound position for rectus sheath blockFigure Ultrasound image of the various structures encountered during rectus sheath BLOCK This is an interfascial plane block which was described by et al. in They described this block for pain relief in two patients with thoracic They that a single of drug at T5 analgesia to dermatomal levels. This along with the of insertion of this block lead to in this giving this block, the patient is usually placed in lateral position with the side up or in the position. A linear high frequency transducer is in a in the to the spinous of the vertebrae to be The transducer is then moved gradually in the lateral direction to the transverse process from the spinous The transverse process can be by the transducer laterally to the ribs and then it The ribs as deep and structures as compared to the transverse which as and structures on ultrasound The needle is then introduced in plane or of plane to target the surface of the transverse One to two of is injected and plane between the ES and the transverse process to It is that the between the ES and the transverse process and not the ES The other end is the linear spread of the in the and Since it is a plane block, around mL of local anaesthetic is required for has suggested to the needle in plane towards the superior aspect of the transverse process to the of the erector spinae plane block. This technique the anterior ligament in more of the drug to the paravertebral block was described and used in surgeries over the the dermatomal distribution of the of ES muscle up to the has led to of the and the technique to high and lumbar [Figures and b].Figure Ultrasound position for block. ESP: Erector spinae muscleFigure (a) Ultrasound image for block at lumbar (b) Transducer position for giving block at lumbar Red line indicates direction of needle insertion from to cephalad ESP: Erector TP: Transverse has led to an in the for this block. It has been used for providing post-operative analgesia after lower abdominal surgeries after form the iliac after The of insertion of block can be to the of surgery. and have described various at which block should be as the 2: of insertion of erector spinae plane block for various types of abdominal of at lumbar be more as compared to insertion at thoracic levels. The transverse at lumbar are as compared to thoracic also the ES muscle is at lumbar levels. One have to use a low frequency curvilinear probe for better of the transverse The exact mechanism of action of block is still et al. in proposed that local anaesthesia (LA) when injected in the ES plane through the intertransverse to the paravertebral space and then blocks the ventral rami of the spinal due to the sensory seen after along with the of a on the spread of drug after have been the mechanism of action of and in a recent on the mechanism of action of block that most the drug through the posterior layer of TLF and to the paravertebral They proposed that these provide for of the drug than the of the drug which can the of action of block. They also proposed that block also blocks the branches of the rami as they pass through the ES plane. They suggested that there is spread of the drug over vertebral along the ES plane while the lateral spread to be to the lateral border of the ES muscle. It is probably the spread of the into the paravertebral space that both the somatic and the visceral analgesia after the block. Various that be associated with block include when the needle is introduced at thoracic motor when the block is at lumbar has been a of after is a of after block if the block is One should be the of LA used during block. BLOCK nerve block through approach block was described by et al. in They proposed that this block blocks both the anterior and lateral cutaneous branches of intercostal nerves as they pass between the origin of transversus abdominis and the costal The technique the patient in position. A linear high frequency transducer was then placed at the of costal cartilage in the plane. The external oblique, internal oblique and transversus abdominis muscles are identified. A needle is then introduced so as to reach the posterior aspect of the costal cartilage in a plane between the transversus abdominis and the internal oblique muscles. mL of LA is then injected in this plane. The needle is then towards the anterior aspect of the costal cartilage so as to reach a plane between the external oblique and the costal mL of LA is deposited in this plane. The suggested that this block provides analgesia from anterior axillary line to the from to The same then introduced modified wherein they only the first as in the block. The that it provided almost analgesia as was provided by the The major advantage of this block is that it provides effective analgesia for surgeries oblique incision along the costal BLOCK In et al. proposed external oblique intercostal plane They proposed that LA when injected between the external oblique and the costal cartilage at intercostal space will spread both medially as as laterally to block both the anterior and the lateral cutaneous branches from T6 to giving this block, the patient is placed in a linear high frequency transducer is placed just medial to anterior axillary line in plane. The needle is then introduced in a cephalad to direction so as to target the space between the rib and the external oblique muscle. of LA is then deposited at this so as to the external oblique from the This block is for and surgeries or surgery the subcostal as as blocks provide only somatic and not visceral analgesia [Figures and Ultrasound position for block. External oblique intercostal planeFigure Ultrasound image of the various structures encountered during block. EO: External oblique, External oblique intercostal analgesia still the for providing pain relief after the abdominal All other regional anesthesia are compared with to the analgesia. abdominal analgesia can be at lower thoracic or at the lumbar levels. The of insertion, of side effects possibility of motor and the use of have in for but effective regional anesthesia A of various nerve block the dermatomal covered by and the of analgesia provided by is in Table 3: Various nerve blocks and the covered by analgesia after abdominal surgery helps in recovery and of the patient. analgesia has an part of The of use of ultrasound in regional anaesthesia has more in an which are and as part of technique in providing pain A of and ultrasound is essential to give these blocks. As the is the of and better to the and of are of