Examining Peripheral Nerve Blocks for Analgesia During Caesarean Birth
Vineet Mishra and Smit B Solanki*
Department of Obstetrics and Gynecology, Institute of Kidney Diseases and Research Center & Dr. H L Trivedi Institute of Transplantation Sciences, Civil Hospital Campus, India
Submission: September 21, 2023;Published: October 03, 2023
*Corresponding author: Smit B Solanki, Department of Obstetrics and Gynecology, Institute of Kidney Diseases and Research Center & Dr H L Trivedi Institute of Transplantation Sciences, Civil Hospital Campus, India
How to cite this article: Vineet M, Smit B S. Examining Peripheral Nerve Blocks for Analgesia During Caesarean Birth. J Gynecol Women’s Health 2023: 26(1): 556178. DOI: 10.19080/JGWH.2023.26.556178
Abstract
In multimodal analgesia regimens for postcesarean delivery, peripheral nerve blocks play a special role. These peripheral nerve blocks, including transversus abdominis plane, quadratus lumborum, iliohypogastric and ilioinguinal, erector spinae, continuous wound infiltration and paravertebral blocks will be discussed in this review paper. Anatomy, data from the literature, and particular areas that require more study will all be evaluated. In the context of emergency caesarean births, considerations for local anaesthetic toxicity and informed consent for these modalities will be highlighted.
Keywords: Peripheral nerve blocks; Analgesia; Obstetrics
Introduction
Currently, neuraxial anaesthesia with intrathecal or epidural morphine, scheduled giving of opioid-free analgesics (acetaminophen and non-steroidal anti-inflammatory drugs) and strategic use of opioids for severe breakthrough pain are all used for routine multimodal caesarean delivery analgesia [1,2]. Peripheral nerve blocks are employed in non-obstetric surgical circumstances as a component of multimodal analgesia regimens. These procedures are associated with decreased opioid usage, improved recovery quality, and lessened hospital resource use [3-6]. Peripheral nerve blocks, albeit not frequently used, are important for caesarean birth analgesia.
Options for peripheral nerve blocks during caesarean birth will be discussed in this review paper. Paravertebral, transversus abdominis plane (TAP), quadratus lumborum (QL), iliohypogastric (IH) and ilioinguinal (II), and wound infiltration (CWI) blocks will receive special consideration. Anatomy, current data, and particular study topics will all be evaluated. In an emergency caesarean birth under general anaesthesia, factors such local anaesthetic toxicity, liposomal bupivacaine, and informed permission will be taken into account.
Methods
With the help of a health sciences librarian, we searched the electronic databases PubMed and MEDLINE for information on peripheral nerve blocks in caesarean birth for this narrative review study. The only articles accepted were those written in English and released between January 1, 1980, and December 31, 2022. From these findings, the papers that were most pertinent to the stated goals of assessing anatomy, gathering data for use in clinical practise, and identifying particular research gaps were chosen. A small number of items from before 1980 were included for historical perspective.
Lumbar Paravertebral Block
Dermatomes Anatomy
The term “paravertebral lumbar sympathetic block” (also known as “paravertebral nerve block”) refers to a nerve root level block that is implanted outside the dura mater [7]. They can be carried out with the use of ultrasonography or landmark guidance methods. Dermatomal coverage is unilateral and is influenced by the amount of local anaesthetic administered, t number of injections administered, and the level of coverage chosen [8]. Four dermatomal levels are typically the maximum dermatomal spread for a single-level block with a 5mL injection volume [9]. The lower thoracoabdominal nerves (T6–T12), which innervate the abdominal wall, are covered by paravertebral nerve blocks during the majority of abdominal procedures [10]. For the Pfannenstiel incision often used for caesarean deliveries (L1), those dermatomes might not always be enough.
Approach
Bilateral paravertebral lumbar block at T12-L1 is recommended for the Pfannensteil skin incision, which is frequently utilised for caesarean birth [11]. The T10–L2 vertebral levels, which correspond to the innervation of the uterus by the preganglionic and postganglionic sympathetic fibres of the superior and inferior hypogastric plexi (branches of the hypogastric nerve), can also be used to add additional paravertebral sympathetic blockade for the visceral pain connected to caesarean delivery [12]. Because the neural foramen is reached perpendicularly, a parasagittal in-plane approach is linked with a lower risk for epidural dissemination than a transverse in-plane approach [13-17]. A location 2-2.5cm lateral to the spinous process tip is located and identified using this method. The pleura, costo-transverse ligament, and transverse process are recognised. The ultrasound probe’s cephalic tip is used to implant a 21-18-gauge needle, which is then moved towards the costo-transverse ligament and seen as it does so. A tactile “pop” is felt when this ligament is crossed. 2-7mL of the preferred local anaesthetic, such as ropivacaine 0.5%–0.75% along with or without epinephrine, are then administered after a negative aspiration. The distribution of local anaesthetic can be seen in a multilayered (two or more) spreading linked to anterior pleura displacement.
Benefits and Drawbacks
The main benefit of paravertebral nerve blockades is that analgesia may be given to individuals for whom neuraxial analgesia may be challenging, such as those who had instrumented spine surgery or neuraxial anatomical anomalies [18]. The paravertebral block of the sympathetic chain ganglion has distinct benefits over conventional abdominal wall blocks that exclusively target cutaneous nerves for non-incisional (visceral) discomfort during caesarean birth. If catheter-based procedures are not employed, a repeat surgery may be required because to the normal analgesic duration of 9 to 12 hours [18]. Although a meta-analysis in thoracotomy patients was unable to draw definitive conclusions on variations in side effects between epidural and paravertebral blockade, patients with paravertebral blocks may be ambulatory and have fewer adverse reactions (urinary retention and hypotension) than those with epidural analgesia [19,20]. It takes some ability to conduct a paravertebral block, and accidental epidural or intrathecal drug injections have been known to occur. These factors, together with greater clinical comfort in administering neuraxial blockade to obstetric patients may account for the small number of studies that have been conducted thus far in caesarean birth patients.
Evidence Now Available and Upcoming Research Directions
It is difficult to compare the effectiveness of paravertebral nerve blocks with epidural analgesia for caesarean birth analgesia in randomised control studies. Paravertebral nerve blocks for labour analgesia have been the subject of published literature, which can shed some light on their potential use for analgesia during caesarean delivery. The available literature only includes case studies of certain patients for whom standard epidural analgesia was not recommended. In one instance, a patient with spina bifida occulta, a tethered cord, and nonpalpable spinous processes received paravertebral nerve block with 0.375% bupivacaine and a pudendal nerve block for labour analgesia. This procedure was successful in providing the patient with appropriate analgesia [21]. A patient with Harrington rods and a non-palpable spinous process who had previously experienced multiple unsuccessful epidural attempts got a pudendal block and bilateral paravertebral nerve block with 15mL of 0.375% with 1:400 000 epinephrine and reported adequate labour analgesia [21].
Transversus Abdominis Plane Block
Dermatomes Anatomy
The TAP block is a block that affects the thoracolumbar nerves, that run in the fascial plane between the muscle of the internal oblique and the transverse abdominis muscles (maximum dermatomal coverage, T6-L1; frequently mentioned, T10-T12) [22,23]. The transversus abdominis and internal oblique muscles are crossed by the anterior primary rami, which then divide onto the anterior and lateral cutaneous nerves at around the midaxillary line.
Approach
There are mainly two TAP strategies. The landmark-guided approach determines the location and depth of the needle insertion using the “double pop” technique through the Petit triangle. The latissimus dorsi edge, external oblique muscle and the iliac crest all abut this anatomic region on its anterior, posterior, and inferior sides, respectively [23,24]. The phrase “double pop” describes the sensation of the needle penetrating the external oblique muscle’s fascia and then the internal oblique muscle’s fascia [23]. In the ultrasound-guided lateral approach, the internal oblique, external oblique and transversus abdominis muscles are identified (from superficial to deep) by positioning the transducer perpendicular to the midaxillary line between the costal border and the iliac crest. The tip of the needle and injection should preferably enter the TAP near the midaxillary line when using an in-plane technique. Nonpregnant women may have distinct ultrasonographic pictures of the fascial planes between the internal oblique muscles and the transverse abdominus for TAP and those who have had caesarean deliveries.
Benefits and Drawbacks
When a woman is not getting neuraxial morphine for any reason, TAP during caesarean birth is helpful [1]. Even after a caesarean birth, the ultrasonographic anatomical to do the block is often recognisable. TAP’s primary drawback is that it doesn’t offer visceral anaesthesia. This oversight most likely explains why several studies have been unable to demonstrate TAP’s advantage over traditional multimodal analgesia with intrathecal opiates.
Evidence Now Available and Upcoming Research Directions
Studies comparing post-cesarean TAP to a placebo or no treatment demonstrate benefit. With landmark-based TAP, McDonnell et al showed a considerable decrease in opioid needs [24]. TAP reduced morphine consumption across a 48-hour period, with the biggest reductions occurring in first 12 hours (33mg vs 6mg). The pain scores (on a visual analogue scale) did not decrease consistently lower with time for both resting and moving, though. Similar to this, several studies have discovered longer times between the initial request for analgesics [24-27]. and lower mean threshold pain medication (opioid and tramadol) requirements; however, pain reduction was not constant across studies. With TAP vs no TAP, there was no change in pain levels at rest or 24 hours after surgery, according to two meta-analyses [28,29]. However, one meta-analysis revealed a decrease in opioid usage as well as a decrease in pain ratings after 24 hours [28]. Another meta-analysis found that postcesarean TAP was linked with decreased pain levels at rest (6 and 12 hours) and with mobility (6 and 12 hours) [29]. Overall, according to the research, TAP reduces the need for opioids and may even reduce pain levels in first 12 hours following caesarean birth.
Can TAP replace or strengthen intrathecal morphine for postc- section analgesia? Studies that compared TAP to control (14 studies), TAP to intrathecal morphine (two studies), and TAP + intrathecal morphine vs intrathecal morphine alone (four trials) were all reviewed in a 2016 meta analysis by Champaneria et al. TAP was less efficient than intrathecal morphine for pain when at rest but more effective than the control for early pain. During the first 24 hours, adding TAP to ITM had no further pain alleviation effects. TAP was once more more effective than control when the authors assessed pain with mobility in the first 24 hours, while intrathecal morphine was once more beneficial at 6 and 24 hours postoperative. TAP was added to ITM, which decreased discomfort at 6 hours after surgery but not after 24. A comparison of TAP to intrathecal morphine demonstrated decreased opioids requirement for the intrathecal morphine patients, however only at select time periods, whereas the evaluation of opioid requirements showed that TAP lowered morphine intake efficiently for up to 24 hours. In the only experiment that assessed this parameter, the inclusion of TAP to intrathecal morphine had no extra impact on opioid use [28]. When intrathecal morphine is not feasible or desirable, such as when general anaesthesia is necessary for a caesarean birth, the best available data shows that TAP is useful for postoperative analgesia. Given that local anaesthetic plasma levels have been seen to surpass lethal levels following TAP [30,31], the optimal dosage for post cesarean TAP has been called into doubt. Three intervention groups were used in Singh et al.’s comparison of two local anaesthetic doses: Intrathecal morphine with a placebo, intrathecal morphine with TAP with high-dose ropivacaine (3mg/ kg, maximum 300mg), and intrathecal morphine with TAP using low-dose ropivacaine (1.5mg/kg, maximum 150mg) (32). Notably, the injectate quantities were the same (60mL) for both the high and low dosage ropivacaine groups. There was no difference among the high-dosage and low-dosage groups in the pain ratings at rest at 24 hours, with movement at 24 hours, or in the need for breakthrough pain medication [32]. At 6 and 12 hours, the highdose group had decreased pain levels with mobility. Numerous reports of cases and cohort studies demonstrating neurological symptoms associated with local anaesthetic use have been reported. Following TAP for a caesarean birth, there was systemic toxicity [30, 33-35]. In a meta-analysis, Ng et al. compared studies that compared the effectiveness of high- and low-dose local anaesthetics. The authors divided dosages into high- and lowdose categories using bupivacaine equivalents, defining a highdose as more than 50mg per block each side. According to the findings (opioid intake, time to first request, and pain ratings at 24 hours), low-dose and high-dose groups experienced comparable levels of analgesia following surgery and opioid-sparing effects [34]. Therefore, at a certain dosage threshold, local anaesthetic benefits might not grow, and low-dose methods for post cesarean TAP might lower the risk of local anaesthetic toxicity without sacrificing analgesic efficacy.
Quadratus Lumborum Block
Dermatomes Anatomy
Ultrasound was used to trace the transversus abdominis further posteriorly till the transversus aponeurosis appeared in order to first explain the QL block peripheral nerve block approach [36]. Understanding the layers that encircle the QL muscle will help you better comprehend the anatomy. The posterior, middle, and anterior portions of the thoracolumbar fascia wrap the QL muscle and a number of other back muscles. The thoracolumbar fascia has three layers: an anterior layer that lies next to the QL muscle, a middle layer that lies between the erector spinae and the QL muscle, and a posterior layer that encloses the erector spinae [36]. Any of these fascial planes can be affected by large volume infusions of local anaesthetic, often the long-acting amides such as ropivacaine or bupivacaine 0.125%-0.375% (15-30 mL each side, 0.2-0.4mL/kg). This affects the nearby nerve fibres, including the lateral cutaneous nerves of the trigeminal nerve. Subcostal, IH, and II nerves can extend into the paravertebral area. The sympathetic chain may be impacted by this posterior expansion into the paravertebral area, resulting in both somatic and visceral analgesia. The different ways to QL block have varying degrees of dermatological dissemination. Patients who have undergone caesarean birth versus non-pregnant patients may show distinct ultrasonographic tissue plane identifications for QL.
Approach
There are four QL block techniques that have been described so far [36]. The first method, known as QL1 or the lateral QL, involves injecting a substance deep into the transversus abdominis aponeurosis. In the second method, known as posterior QL or QL2, local anaesthetic is deposited posterior to the QL muscle after an injection deep into the erector spinae muscle. An injection is given into the plane between the psoas major muscle and the QL muscle using the transmuscular (QLT) or anterior technique. Finally, local anaesthetic is administered directly into the QL muscle for the intramuscular QL (QLI) described in the paediatric population [37]. With the various QL block techniques, dermatome spread varies slightly.
Benefits and Drawbacks
In patients undergoing caesarean delivery, QL block has been linked to decreased postoperative opioid intake and pain scores; however, these studies have been difficult to interpret due to the dearth of study groups receiving standardised multimodal pain relief with neuraxial morphine. After a caesarean delivery, Blanco et al. demonstrated that posterior approach QL (QL2) injection of 0.125% bupivacaine at 2mL/kg reduced morphine use at 6 and 12 hours, decreased morphine requests at 6, 12, 24, and 48 hours, and decreased pain scores while moving and resting (not significantly at 24 hours) [38]. There were substantial variations in morphine consumption, the delay to the first application for postoperative opioid, and the average score of the pain numeric rating scale within 48 hours postoperatively, according to one research among patients arbitrarily allocated to QL1 with ropivacaine 0.375% versus control [39]. TAP and QL block effects on caesarean birth outcomes were compared. After 12, 24, and 48 hours following birth, patients undergoing posterior access QL (QL2) required fewer morphine than patients getting TAP, but there was no apparent distinction at 4 or 6 hours. After 6, 12, 24, and 48 hours, the morphine needs of the QL group were also lower. Visual analogue scales did not significantly differ across the groups during either rest or movement [40]. Contrary to TAP, the QL area is located nearer the vertebral column; as a result, QL blocks might be loosely connected with paravertebral spread. Visceral analgesia can be increased by this paravertebral spread, but it can also provide more hemodynamic alterations. Concerning local systemic anaesthetic toxicity can arise from the QL block’s absorption in the general circulation through the highly vascularized muscle bed [37].
Evidence Now Available and Upcoming Research Directions
QL has been shown in randomised controlled studies to date [38,40] to be superior to spinal anaesthesia alone and to TAP block plus spinal anaesthesia during caesarean deliveries. With both getting 0.125% bupivacaine 0.2 mL/kg in both sides for a total of 0.4 mL/kg, Blanco et al. [40] evaluated QL and TAP blocks following caesarean delivery. At 12, 24, and 48 hours, morphine doses were lower in QL block patients than in TAP patients. Both groups saw almost the same amount of total pain alleviation when at rest and while moving. It is important to note that research have been constrained up to this point due to the lack of spinal anaesthesia comprising ITM and standardised postpartum multimodal analgesia. This restriction prevents any inferences from being drawn regarding QL’s superiority to existing clinical practise standards. To evaluate the usefulness of quality assurance as a standard component of a to determine the best method of QL block (QL1, QL2, QLT, or QLI) for caesarean birth analgesia, an integrated analgesia regimen that includes neuraxial anaesthesia with morphine is used.
Ilioinguinal-iliohypogastric Block
Dermatomes Anatomy
Transversus abdominis muscles that are superior and medial from the anterior superior iliac spine (ASIS) are penetrated by the II and IH nerves, which originate from the L1 nerve root [41]. The skin above the inguinal area receives sensory innervation from the IH nerve. The Inguinal is where the II nerve enters. The medial thigh and scrotum’s skin get sensory innervation from this canal [41]. The external oblique muscles are penetrated by the ventral branch, which also gives sensory innervation to the suprapubic region [41]. The ventral branch first penetrates the internal oblique muscle, supplying innervation to the internal and external oblique muscles. Despite the fact that the II and IH nerves are traditionally taught to originate from L1, autopsy studies reveal that the II nerve can also come from nerves stretching from T12 to L3 and the IH nerve can come from T11 to L1 [42].
Approach
On the aforementioned anatomy, the reference point approach for II-IH nerve block is predicated. The ASIS [41] is positioned 1-2cm medial and 1-2 cm superiorly when the needle is placed. Alternatively, a first “pop” sensation occurs with a penetration of the external oblique and a second “pop” is felt with a piercing of the internal oblique [41]. A “pop” is felt as the needle penetrates the opening between the internal oblique and transversus. In the internal oblique and transversus abdominis muscles, local anaesthetic is injected. To enable improved local anaesthetic dispersion, Bell et al. created a multi-injection approach [43]. In order to conduct an II-IH nerve block, ultrasound guidance can also be employed. In this procedure, a transducer is placed along the path between the ASIS and the umbilicus, and local anaesthetic is applied to the transversus abdominis muscle and internal oblique muscles.
Benefits and Drawbacks
The lateral femoral cutaneous and femoral nerve may be blocked by drugs sliding beneath the inguinal ligament, and bowel perforation is an uncommon complication of II-IH block. The technical difficulties and unpredictability of the multiple-injection “double pop” approach are drawbacks compared to the landmark or blind method.
Evidence Now Available and Upcoming Research Directions
The L1 dermatome is covered by the II nerve block, which has been investigated as a potential target for analgesia following caesarean deliveries. One of the earliest studies was written by Bunting in 1988 and it described both sides of II nerve blockages in 26 individuals undergoing general anaesthesia for caesarean births [44]. The study found that patients who underwent an II nerve block had decreased pain scores over the first 24 hours. Additionally, they demonstrated that at 24 hours, the intervention group’s opioid needs were much lower [44]. In contrast, an additional study [45] evaluating II and IH blocks performed before and following the incision for caesarean delivery found no distinction in morphine intake in the initial 24 hours between patients who received II-IH and those who did not. The rate of failure of blocks inserted before surgery was approximately 50%, whereas there were no failed blocks in blocks inserted after surgery, which put a cap on the study. For the II nerve blocks, Bunting employed a single injection procedure, whereas Bell discussed the “multilevel II-IH (II-IH) block” methodology [43]. Patients in Bell et al.’s trial received postoperative II-IH blocks with a claimed 95% success rate after neuraxial anaesthesia (without ITM). Additionally, they reported a sizable the II-IH intervention group’s use of injectable patient-controlled analgesic (PCA) morphine decreased over the course of 24 hours, but there was no difference in pain intensity or side effects such nausea and itching [43] When performing a caesarean delivery under general anaesthesia, Sakalli et al used Bell’s approach and similarly showed decreased tramadol intake in the II-IH group as well as lower pain score at resting for twentyfour hours along with activity in the first 8 hours [46]. The results showed no difference in the research groups’ levels of nausea, vomiting, pruritus, or sedation in Sakalli’s or Bell’s trials. TAP vs II-IH [47] and combined II-TAP (I-TAP) blocks [48] have been contrasted by other researchers. In one trial, TAP demonstrated lower tramadol consumption following caesarean delivery with spinal anaesthesia without ITM as compared to II-IH blocks [47]. Individuals with unsuccessful blocks were not included in this study, which strengthened the findings. The L1 dermatome is more consistently covered by the I-TAP block than by TAP alone (TAP blocking is expected to fail in providing L1 sensory block in >50% of patients) [48]. This is because the I-TAP blocked blends the area of block of TAP with the particular nerves of the II-IH block. The combination I-TAP showed lower opioid use than placebo at all time points in a prospective in nature, triple-blind, placebocontrolled randomised experiment. Additionally, in the initial 24 hours following surgery, it decreased pain levels both at rest and while moving [48]. Sedation, vomiting, nausea, or itching were not different across the groups; however, one case of femoral nerve palsy following II-IH nerve blocking was reported [48]. Availability of additional peripheral blocks in a greater degree of dermatomal circulate (and potential visceral impact) indicates that study time and effort could be better used in other areas. While more data are required prior to IH-II blocks can be suggested as an effective method for caesarean delivery analgesia, it is already clear that they are not the only option.
Continual Wound Infiltration
A catheter, often multi orifice, is inserted at the surgical site and attached to an elastomer infusion pump to administer a steady, fixed rate infusion of drugs to nearby nerves as part of the CWI analgesic approach [49]. CWI gives nerves surrounding the affected area cutaneous analgesia rather than analgesia in a dermatomal distribution catheter. Before the surgical closure, the surgeon usually positions the catheter close to the nerve innervating the surgical site and tunnels it under the skin to avoid catheters migration and infection. Catheter placement during caesarean delivery is either deep to the fascia or between the rectus membrane and subcutaneous tissue [50]. Although diclofenac and other anti-inflammatory medications have been mentioned, local anaesthetics are more frequently administered [51].
Benefits and Drawbacks
Single-shot wound infiltration might offer sufficient analgesia, but its potency is constrained by the pharmacokinetics of the chosen medication, making sustained analgesia less dependable. During after delivery for up to 4 days, CWI permits ongoing administration of local anaesthetic either alongside or without also nonsteroidal anti-inflammatory medications [52]. There is a danger for infection and catheters migration with any indwelling catheter. One significant drawback of CWI is the unresolved plasma content of local anaesthetic during continuous infusion, which theoretically might result in systemic toxicity of local anaesthetics. However, considering the low concentration and frequent infusion rates associated with CWI, this problem is improbable. Another drawback is that the surgeon may not properly put the catheter close to the afflicted nerve beds, which results in variable analgesia. Lastly, the infusion patterns and quantities used to provide analgesia frequently result in leakage within the location of the wound, which may be upsetting to both patients and healthcare professionals.
Evidence Now Available and Upcoming Research Directions
The use of fewer opioids has been linked to CWI during spinal anaesthesia for caesarean birth [51]. ITM (100mcg) in saline subfascial CWI and intrathecal saline (control) alongside ropivacaine CWI both lengthened postoperative analgesia by an average of 100 minutes contrasted with placebo (both saline ITM and CWI), but there was not a statistically significant distinction between ITM and CWI for pain or opioid consumption outcomes [53]. In a randomised control trial involving 58 women who had elective caesarean deliveries, CWI was associated with lower pain scores at rest at 2, 6, and 48 hours after delivery compared to epidural morphine, and CWI patients experienced fewer episodes of vomiting, nausea, pruritus, and urinary retention [54]. In order to lessen post-cesarean pain and lower systemic morphine needs, Lavand’homme et al. demonstrated that CWI with diclofenac was equally successful as CWI with 0.2% ropivacaine with systemic diclofenac [51]. A different study compared CWI deeper to the fascia with CWI superficially to the fascia, and the former group reported considerably less pain at rest and less overall postoperative morphine intake [55,56]. A randomised control experiment comparing ITM paired with saline CWI infusion to 48 hours of CWI utilising ropivacaine or saline (no ITM), in contrast to these studies that show the benefits of CWI. These results imply that ITM continues to provide extra analgesic benefit by treating visceral pain in addition to incisional discomfort, whereas CWI is only useful in treating incisional pain. There are still details to be clarified regarding the application of CWI for analgesia during caesarean delivery. Although research on the cost-effectiveness of CWI contrasted with other modalities for analgesia during caesarean birth, such as ITM, TAP, or QL, such as parenteral or epidural analgesia, are sparse, CWI has been proven to be costbeneficial in comparison to other open abdominal surgeries [57].
Erector Spinae Plane Block
This relatively novel procedure for a truncal block includes depositing local anaesthetic in the plane anterior of the erector spinae muscle and superficially to the transverse processes of the thoracic or lumbar vertebrae, leading to significant dissemination in both the cephalo-caudad and medial-lateral planes. While involvement of the ventral rami of neighbouring segmental neurons is more unpredictable, dissemination via the dorsal rami is guaranteed [58]. It has not been widely used to provide analgesia following caesarean deliveries. Only two case reports with promising outcomes have been published thus far [59,60], one of which mentions a possible risk for motor block.
Liposomal Bupivacaine
For peripheral nerve blocks during caesarean deliveries, liposomal bupivacaine is becoming more popular. For postoperative pain relief by single-dose infiltration, the US Federal Drug Administration (FDA) has approved the prolongedrelease (as much as to 72 hours) version of bupivacaine known as liposomal bupivacaine [61]. Questions about its use in analgesia for caesarean deliveries have been raised due to the benefits of sustained analgesia without the need for a catheter. The few information that is currently available on liposomal bupivacaine in this group of people has been methodologically constrained and has produced mixed findings. Reduced postoperative opioid needs and postcesarean pain scores were demonstrated in two retrospective trials, 1 using intraincisional liposomal bupivacaine while the other on liposomal bupivacaine TAP blocks [62,63]. In contrast, Prahbu et al.’s [64] randomised control trial contrasted liposomal bupivacaine and a placebo by fascial or epidermal penetration, before fascial closure. In the first two days following surgery, there were no differences among the groups in terms of pain levels or opioid use, according to the results. Both groups’ pain levels were significantly less below institutional norms (pain scores in both groups were around 2, while institutional pain scores are normally around 5), which raises the possibility of observer bias. In conclusion, biases in the published research on liposomal bupivacaine, such as retrospectively method and observer (“Hawthorne”) effects, have been a problem. There are presently no firm recommendations about the routine application of liposomal bupivacaine for peripheral nerve blocks during caesarean deliveries based on the existing evidence. Future studies on this subject ought to take into account the following: (1) the addition of a third control arm to lessen bias among observers or a placebo impacts; (2) neither inferiority study designs; and (3) an emphasis on subgroups known to be more pain-sensitive, like those women who were unable to receive neuraxial morphine.
Conclusion
Peripheral nerve blockades for caesarean deliveries are believed to be most beneficial in situations where traditional multimodal analgesia using neuraxial morphine or non-opioid analgesics has failed, or in which neuraxial morphine cannot be administered (e.g. general anaesthesia for a caesarean birth). A monitoring period of 40 to 90 minutes following truncal wall blocks is recommended in order to minimise the risk of local anaesthetic toxicity without sacrificing analgesia. The functions using paravertebral nerve blocks or erector spinae blockers for analgesia during caesarean delivery require further study. It is best to make decisions regarding informed consent when administering peripheral nerve blocks for analgesia during emergency caesarean births.
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- Suelto MD, Shaw BD (1999) Labor analgesia with paravertebral lumbar sympathetic block. Reg Anesth Pain Med 24(2): 179-181.
- Rozen WM, Tran TMN, Ashton MW, Barrington MJ, Ivanusic JJ, et al. (2008) Refining the course of the thoracolumbar nerves: a new understanding of the innervation of the anterior abdominal wall. Clin Anat 21(4): 325-333.
- Tsai HC, Yoshida T, Chuang TY, Sheng-Feng Y, Chuen-Chau C, et al. (2017) Transversus abdominis plane block: an updated review of anatomy and techniques. Biomed Res Int 2017: 1-12.
- McDonnell JG, Curley G, Carney J, Aoife B, Joseph C, et al. (2008) The analgesic efficacy of transversus abdominis plane block after cesarean delivery: a randomized controlled trial. Anesth Analg 106(1): 186-191.
- Belavy D, Cowlishaw PJ, Howes M, Phillips F (2009) Ultrasound-Guided transversus abdominis plane block for analgesia after caesarean delivery. Br J Anaesth 103(5): 726-730.
- Eslamian L, Kabiri-Nasab M, Agha-Husseini M, Azimaraghi O, Gilda B, et al. (2016) Adding sufentanil to TAP block hyperbaric bupivacaine decreases post-cesarean delivery morphine consumption. Acta Med Iran 54(3): 185-190.
- Mankikar M, Sardesai S, Ghodki P (2016) Ultrasound-Guided transversus abdominis plane block for post-operative analgesia in patients undergoing caesarean section. Indian J Anaesth 60(4): 253-257.
- Champaneria R, Shah L, Wilson MJ, Daniels JP (2016) Clinical effectiveness of transversus abdominis plane (TAP) blocks for pain relief after caesarean section: a meta-analysis. Int J Obstet Anesth 28: 45-60.
- Mishriky BM, George RB, Habib AS (2012) Transversus abdominis plane block for analgesia after cesarean delivery: a systematic review and meta-analysis. Can J Anesth/J Can Anesth 59(8): 766-778.
- Griffiths JD, Le NV, Grant S, Bjorksten A, Hebbard P, et al. (2013) Symptomatic local anaesthetic toxicity and plasma ropivacaine concentrations after transversus abdominis plane block for caesarean section. Br J Anaesth 110(6): 996-1000.
- Trabelsi B, Charfi R, Bennasr L, MarzoukSB, Eljebari H, et al. (2017) Pharmacokinetics of bupivacaine after bilateral ultrasound-guided transversus abdominis plane block following cesarean delivery under spinal anesthesia. Int J Obstet Anesth 32: 17-20.
- Singh S, Dhir S, Marmai K, Rehou S, Silva M, et al. (2013) Efficacy of ultrasound-guided transversus abdominis plane blocks for post-cesarean delivery analgesia: a double-blind, dose-comparison, placebo-controlled randomized trial. Int J Obstet Anesth 22(3): 188-193.
- Hessian EC, Evans BE, Woods JA, Taylor DJ, Kinkel E, et al. (2013) Plasma ropivacaine concentrations during bilateral transversus abdominis plane infusions. Br J Anaesth 111(3): 488-495.
- Ng SC, Habib AS, Sodha S, Carvalho B, Sultan P, et al. (2018) High-Dose versus low-dose local anaesthetic for transversus abdominis plane block post-Caesarean delivery analgesia: a meta-analysis. Br J Anaesth 120(2): 252-263.
- Weiss E, Jolly C, Dumoulin JL, Riadh BM, Pierre B, et al. (2014) Convulsions in 2 patients after bilateral ultrasound-guided transversus abdominis plane blocks for cesarean analgesia. Reg Anesth Pain Med 39(3): 248-251.
- Ueshima H, Otake H, Lin JA (2017) Ultrasound-Guided quadratus lumborum block: an updated review of anatomy and techniques. Biomed Res Int 2017: 1-7.
- Murouchi T (2016) Quadratus lumborum block intramuscular approach for pediatric surgery. Acta Anaesthesiologica Taiwanica 54(4): 135-136.
- Blanco R, Ansari T, Girgis E (2015) Quadratus lumborum block for postoperative pain after caesarean section: a randomised controlled trial. Eur J Anaesthesiol 32(): 812-8188.
- Mieszkowski MM, Mayzner-Zawadzka E, Tuyakov B, Mieszkowska M, Żukowski M, et al. (2018) Evaluation of the effectiveness of the quadratus lumborum block type I using ropivacaine in postoperative analgesia after a cesarean section - a controlled clinical study. Ginekol Pol 89(2): 89-96.
- Blanco R, Ansari T, Riad W, Shetty N (2016) Quadratus lumborum block versus Transversus abdominis plane block for postoperative pain after cesarean delivery. Reg Anesth Pain Med 41(6): 757–762.
- Abrahams M, Derby R, Horn JL (2016) Update on ultrasound for truncal blocks: a review of the evidence. Reg Anesth Pain Med 41(2): 275-288.
- Klaassen Z, Marshall E, Tubbs RS, Robert GL Jr, Wartmann CT, et al. (2011) Anatomy of the ilioinguinal and iliohypogastric nerves with observations of their spinal nerve contributions. Clin Anat 24(4): 454-461.
- Bell EA, Jones BP, Olufolabi AJ, et al. (2002) Iliohypogastric-ilioinguinal peripheral nerve block for post-cesarean delivery analgesia decreases morphine use but not opioid-related side effects. Can J Anesth/J Can Anesth 49(7): 694-700.
- Bunting P, McConachie I (1988) Ilioinguinal nerve blockade for analgesia after caesarean section. Br J Anaesth 61(6): 773–775.
- Huffnagle HJ, Norris MC, Leighton BL, Arkoosh VA (1996) Ilioinguinal iliohypogastric nerve blocks-before or after cesarean delivery under spinal anesthesia? Anesth Analg 82(1): 8-12.
- Sakalli M, Ceyhan A, Uysal HY, Yazici I, Hülya B, et al. (2010) The efficacy of ilioinguinal and iliohypogastric nerve block for postoperative pain after caesarean section. J Res Med Sci 15(1): 6-13.
- Kiran LV, Sivashanmugam T, Kumar VRH, Krishnaveni N, Parthasarathy S, et al. (2017) Relative efficacy of ultrasound-guided Ilioinguinal-iliohypogastric nerve block versus transverse abdominis plane block for postoperative analgesia following lower segment cesarean section: a prospective, randomized Observer-blinded trial. Anesth Essays Res 11(3): 713-717.
- Staker JJ, Liu D, Church R, Carlson DJ, Panahkhahi M, et al. (2018) A triple-blind, placebo-controlled randomised trial of the ilioinguinal-transversus abdominis plane (I-TAP) nerve block for elective caesarean section. Anaesthesia 73(5): 594-602.
- Dahl JB, Moiniche S, Kehlet H (1994) Wound infiltration with local anaesthetics for postoperative pain relief. Acta Anaesthesiol Scand 38(1): 7-14.
- Reinikainen M, Syvaoja S, Hara K (2014) Continuous wound infiltration with ropivacaine for analgesia after caesarean section: a randomised, placebo-controlled trial. Acta Anaesthesiol Scand 58(8): 973-979.
- Lavand’homme PM, Roelants F, Waterloos H, et al. (2007) Postoperative analgesic effects of continuous wound infiltration with diclofenac after elective cesarean delivery. Anesthesiology 106(6): 1220-1225.
- Bomberg H, Bayer I, Wagenpfeil S, Paul K, Hinnerk W, et al. (2018) Prolonged catheter use and infection in regional anesthesia: a retrospective registry analysis. Anesthesiology 128(4): 764-773.
- Lalmand M, Wilwerth M, Fils JF, Philippe VDL (2017) Continuous ropivacaine subfascial wound infusion compared with intrathecal morphine for Postcesarean analgesia: a prospective, randomized controlled, double-blind study. Anesth Analg 125: 907-912.
- O’Neill P, Duarte F, Ribeiro I, Centeno MJ, Moreira J, et al. (2012) Ropivacaine continuous wound infusion versus epidural morphine for postoperative analgesia after cesarean delivery: a randomized controlled trial. Anesth Analg 114(1): 179-185.
- Rackelboom T, Strat SL, Silvera S, Thomas S, Agnes B, et al. (2011) Improving continuous wound infusion effectiveness for postoperative analgesia after cesarean delivery. Obstetrics & Gynecology 116(4): 893-900.
- Kainu JP, Sarvela J, Halonen P, Toivonen HJ, Halmesmäki H, et al. (2012) Continuous wound infusion with ropivacaine fails to provide adequate analgesia after caesarean section. Int J Obstet Anesth 21(2): 119–124.
- Tilleul P, Aissou M, Bocquet F, Thiriat N, Grelle OL, et al. (2012) Cost-Effectiveness analysis comparing epidural, patient-controlled intravenous morphine, and continuous wound infiltration for postoperative pain management after open abdominal surgery. Br J Anaesth 108(6): 998-1005.
- Ivanusic J, Konishi Y, Barrington MJ (2018) A cadaveric study investigating the mechanism of action of erector spinae blockade. Reg Anesth Pain Med 43(6): 567–571.
- Selvi O, Tulgar S (2018) Ultrasound guided erector spinae plane block as a cause of unintended motor block. Rev Esp Anestesiol Reanim 65(10): 589-592.
- Altinpulluk YE, Garcia SD, Fajardo-Perez M (2018) Erector spinae plane block for analgesia after lower segment caesarean section: case report. Rev Esp Anestesiol Reanim 65(5): 284-286.
- Baker BW, Villadiego LG, Lake YN, Yazan A, Timmins AE, et al. (2018) Transversus abdominis plane block with liposomal bupivacaine for pain control after cesarean delivery: a retrospective chart review. J Pain Res 11: 3109-3116.
- Santos AC, DeArmas PI (2001) Systemic toxicity of levobupivacaine, bupivacaine, and ropivacaine during continuous intravenous infusion to nonpregnant and pregnant ewes. Anesthesiology 95(5): 1256-1264.
- Tsen LC, Tarshis J, Denson DD, Osathanondh R, Datta S, et al. (19999) Measurements of maternal protein binding of bupivacaine throughout pregnancy. Anesth Analg 89(4): 965-968.
- Prabhu M, Clapp MA, McQuaid-Hanson E, Samsiya O, OʼDonnell T, et al. (2018) Liposomal bupivacaine block at the time of cesarean delivery to decrease postoperative pain. Obstetrics & Gynecology 132(1): 70-78.
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- El-Boghdadly K, Madjdpour C, Chin KJ (2016) Thoracic paravertebral blocks in abdominal surgery - a systematic review of randomized controlled trials. Br J Anaesth 117(3): 297-308.
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- Lönnqvist PA, MacKenzie J, Soni AK, Conacher ID (1995) Paravertebral blockade. failure rate and complications. Anaesthesia 50(9): 813-815.
- Luyet C, Eichenberger U, Greif R, Vogt A, Szücs ZF, et al. (2009) Ultrasound-Guided paravertebral puncture and placement of catheters in human cadavers: an imaging study. Br J Anaesth 102: 534-539.
- Naja Z, Lonnqvist PA (2001) Somatic paravertebral nerve blockade incidence of failed block and complications. Anaesthesia 56(12): 1181-1201.
- Purcell-Jones G, Pither CE, Justins DM (1989) Paravertebral somatic nerve block: a clinical, radiographic, and computed tomographic study in chronic pain patients. Anesth Analg 68(1): 32-39.
- Nair V, Henry R (2001) Bilateral paravertebral block: a satisfactory alternative for labour analgesia. Can J Anesth/J Can Anesth 48(2): 179-184.
- Kosinski S, Fryzlewicz E, Wilkojc M, Adam Ć, Marcin Z, et al. (2016) Comparison of continuous epidural block and continuous paravertebral block in postoperative analgaesia after video-assisted thoracoscopic surgery lobectomy: a randomised, non-inferiority trial. Anaesthesiol Intensive Ther 48(5): 280-287.
- Yeung JHY, Gates S, Naidu BV, Matthew JAW, Smith FG, et al. (2016) Paravertebral block versus thoracic epidural for patients undergoing thoracotomy. Cochrane Database Syst Rev 2(2): CD009121.
- Suelto MD, Shaw BD (1999) Labor analgesia with paravertebral lumbar sympathetic block. Reg Anesth Pain Med 24(2): 179-181.
- Rozen WM, Tran TMN, Ashton MW, Barrington MJ, Ivanusic JJ, et al. (2008) Refining the course of the thoracolumbar nerves: a new understanding of the innervation of the anterior abdominal wall. Clin Anat 21(4): 325-333.
- Tsai HC, Yoshida T, Chuang TY, Sheng-Feng Y, Chuen-Chau C, et al. (2017) Transversus abdominis plane block: an updated review of anatomy and techniques. Biomed Res Int 2017: 1-12.
- McDonnell JG, Curley G, Carney J, Aoife B, Joseph C, et al. (2008) The analgesic efficacy of transversus abdominis plane block after cesarean delivery: a randomized controlled trial. Anesth Analg 106(1): 186-191.
- Belavy D, Cowlishaw PJ, Howes M, Phillips F (2009) Ultrasound-Guided transversus abdominis plane block for analgesia after caesarean delivery. Br J Anaesth 103(5): 726-730.
- Eslamian L, Kabiri-Nasab M, Agha-Husseini M, Azimaraghi O, Gilda B, et al. (2016) Adding sufentanil to TAP block hyperbaric bupivacaine decreases post-cesarean delivery morphine consumption. Acta Med Iran 54(3): 185-190.
- Mankikar M, Sardesai S, Ghodki P (2016) Ultrasound-Guided transversus abdominis plane block for post-operative analgesia in patients undergoing caesarean section. Indian J Anaesth 60(4): 253-257.
- Champaneria R, Shah L, Wilson MJ, Daniels JP (2016) Clinical effectiveness of transversus abdominis plane (TAP) blocks for pain relief after caesarean section: a meta-analysis. Int J Obstet Anesth 28: 45-60.
- Mishriky BM, George RB, Habib AS (2012) Transversus abdominis plane block for analgesia after cesarean delivery: a systematic review and meta-analysis. Can J Anesth/J Can Anesth 59(8): 766-778.
- Griffiths JD, Le NV, Grant S, Bjorksten A, Hebbard P, et al. (2013) Symptomatic local anaesthetic toxicity and plasma ropivacaine concentrations after transversus abdominis plane block for caesarean section. Br J Anaesth 110(6): 996-1000.
- Trabelsi B, Charfi R, Bennasr L, MarzoukSB, Eljebari H, et al. (2017) Pharmacokinetics of bupivacaine after bilateral ultrasound-guided transversus abdominis plane block following cesarean delivery under spinal anesthesia. Int J Obstet Anesth 32: 17-20.
- Singh S, Dhir S, Marmai K, Rehou S, Silva M, et al. (2013) Efficacy of ultrasound-guided transversus abdominis plane blocks for post-cesarean delivery analgesia: a double-blind, dose-comparison, placebo-controlled randomized trial. Int J Obstet Anesth 22(3): 188-193.
- Hessian EC, Evans BE, Woods JA, Taylor DJ, Kinkel E, et al. (2013) Plasma ropivacaine concentrations during bilateral transversus abdominis plane infusions. Br J Anaesth 111(3): 488-495.
- Ng SC, Habib AS, Sodha S, Carvalho B, Sultan P, et al. (2018) High-Dose versus low-dose local anaesthetic for transversus abdominis plane block post-Caesarean delivery analgesia: a meta-analysis. Br J Anaesth 120(2): 252-263.
- Weiss E, Jolly C, Dumoulin JL, Riadh BM, Pierre B, et al. (2014) Convulsions in 2 patients after bilateral ultrasound-guided transversus abdominis plane blocks for cesarean analgesia. Reg Anesth Pain Med 39(3): 248-251.
- Ueshima H, Otake H, Lin JA (2017) Ultrasound-Guided quadratus lumborum block: an updated review of anatomy and techniques. Biomed Res Int 2017: 1-7.
- Murouchi T (2016) Quadratus lumborum block intramuscular approach for pediatric surgery. Acta Anaesthesiologica Taiwanica 54(4): 135-136.
- Blanco R, Ansari T, Girgis E (2015) Quadratus lumborum block for postoperative pain after caesarean section: a randomised controlled trial. Eur J Anaesthesiol 32(): 812-8188.
- Mieszkowski MM, Mayzner-Zawadzka E, Tuyakov B, Mieszkowska M, Żukowski M, et al. (2018) Evaluation of the effectiveness of the quadratus lumborum block type I using ropivacaine in postoperative analgesia after a cesarean section - a controlled clinical study. Ginekol Pol 89(2): 89-96.
- Blanco R, Ansari T, Riad W, Shetty N (2016) Quadratus lumborum block versus Transversus abdominis plane block for postoperative pain after cesarean delivery. Reg Anesth Pain Med 41(6): 757–762.
- Abrahams M, Derby R, Horn JL (2016) Update on ultrasound for truncal blocks: a review of the evidence. Reg Anesth Pain Med 41(2): 275-288.
- Klaassen Z, Marshall E, Tubbs RS, Robert GL Jr, Wartmann CT, et al. (2011) Anatomy of the ilioinguinal and iliohypogastric nerves with observations of their spinal nerve contributions. Clin Anat 24(4): 454-461.
- Bell EA, Jones BP, Olufolabi AJ, et al. (2002) Iliohypogastric-ilioinguinal peripheral nerve block for post-cesarean delivery analgesia decreases morphine use but not opioid-related side effects. Can J Anesth/J Can Anesth 49(7): 694-700.
- Bunting P, McConachie I (1988) Ilioinguinal nerve blockade for analgesia after caesarean section. Br J Anaesth 61(6): 773–775.
- Huffnagle HJ, Norris MC, Leighton BL, Arkoosh VA (1996) Ilioinguinal iliohypogastric nerve blocks-before or after cesarean delivery under spinal anesthesia? Anesth Analg 82(1): 8-12.
- Sakalli M, Ceyhan A, Uysal HY, Yazici I, Hülya B, et al. (2010) The efficacy of ilioinguinal and iliohypogastric nerve block for postoperative pain after caesarean section. J Res Med Sci 15(1): 6-13.
- Kiran LV, Sivashanmugam T, Kumar VRH, Krishnaveni N, Parthasarathy S, et al. (2017) Relative efficacy of ultrasound-guided Ilioinguinal-iliohypogastric nerve block versus transverse abdominis plane block for postoperative analgesia following lower segment cesarean section: a prospective, randomized Observer-blinded trial. Anesth Essays Res 11(3): 713-717.
- Staker JJ, Liu D, Church R, Carlson DJ, Panahkhahi M, et al. (2018) A triple-blind, placebo-controlled randomised trial of the ilioinguinal-transversus abdominis plane (I-TAP) nerve block for elective caesarean section. Anaesthesia 73(5): 594-602.
- Dahl JB, Moiniche S, Kehlet H (1994) Wound infiltration with local anaesthetics for postoperative pain relief. Acta Anaesthesiol Scand 38(1): 7-14.
- Reinikainen M, Syvaoja S, Hara K (2014) Continuous wound infiltration with ropivacaine for analgesia after caesarean section: a randomised, placebo-controlled trial. Acta Anaesthesiol Scand 58(8): 973-979.
- Lavand’homme PM, Roelants F, Waterloos H, et al. (2007) Postoperative analgesic effects of continuous wound infiltration with diclofenac after elective cesarean delivery. Anesthesiology 106(6): 1220-1225.
- Bomberg H, Bayer I, Wagenpfeil S, Paul K, Hinnerk W, et al. (2018) Prolonged catheter use and infection in regional anesthesia: a retrospective registry analysis. Anesthesiology 128(4): 764-773.
- Lalmand M, Wilwerth M, Fils JF, Philippe VDL (2017) Continuous ropivacaine subfascial wound infusion compared with intrathecal morphine for Postcesarean analgesia: a prospective, randomized controlled, double-blind study. Anesth Analg 125: 907-912.
- O’Neill P, Duarte F, Ribeiro I, Centeno MJ, Moreira J, et al. (2012) Ropivacaine continuous wound infusion versus epidural morphine for postoperative analgesia after cesarean delivery: a randomized controlled trial. Anesth Analg 114(1): 179-185.
- Rackelboom T, Strat SL, Silvera S, Thomas S, Agnes B, et al. (2011) Improving continuous wound infusion effectiveness for postoperative analgesia after cesarean delivery. Obstetrics & Gynecology 116(4): 893-900.
- Kainu JP, Sarvela J, Halonen P, Toivonen HJ, Halmesmäki H, et al. (2012) Continuous wound infusion with ropivacaine fails to provide adequate analgesia after caesarean section. Int J Obstet Anesth 21(2): 119–124.
- Tilleul P, Aissou M, Bocquet F, Thiriat N, Grelle OL, et al. (2012) Cost-Effectiveness analysis comparing epidural, patient-controlled intravenous morphine, and continuous wound infiltration for postoperative pain management after open abdominal surgery. Br J Anaesth 108(6): 998-1005.
- Ivanusic J, Konishi Y, Barrington MJ (2018) A cadaveric study investigating the mechanism of action of erector spinae blockade. Reg Anesth Pain Med 43(6): 567–571.
- Selvi O, Tulgar S (2018) Ultrasound guided erector spinae plane block as a cause of unintended motor block. Rev Esp Anestesiol Reanim 65(10): 589-592.
- Altinpulluk YE, Garcia SD, Fajardo-Perez M (2018) Erector spinae plane block for analgesia after lower segment caesarean section: case report. Rev Esp Anestesiol Reanim 65(5): 284-286.
- Baker BW, Villadiego LG, Lake YN, Yazan A, Timmins AE, et al. (2018) Transversus abdominis plane block with liposomal bupivacaine for pain control after cesarean delivery: a retrospective chart review. J Pain Res 11: 3109-3116.
- Santos AC, DeArmas PI (2001) Systemic toxicity of levobupivacaine, bupivacaine, and ropivacaine during continuous intravenous infusion to nonpregnant and pregnant ewes. Anesthesiology 95(5): 1256-1264.
- Tsen LC, Tarshis J, Denson DD, Osathanondh R, Datta S, et al. (19999) Measurements of maternal protein binding of bupivacaine throughout pregnancy. Anesth Analg 89(4): 965-968.
- Prabhu M, Clapp MA, McQuaid-Hanson E, Samsiya O, OʼDonnell T, et al. (2018) Liposomal bupivacaine block at the time of cesarean delivery to decrease postoperative pain. Obstetrics & Gynecology 132(1): 70-78.