Potentially toxic concentrations in blood of total ropivacaine after bilateral transversus abdominis plane blocks; a pharmacokinetic study

CONTEXT

Elevated blood levels of lidocaine and ropivacaine have been described after transversus abdominis plane (TAP) block.

OBJECTIVE

To investigate the pharmacokinetic profile of ropivacaine after bilateral TAP blocks.

DESIGN

Prospective observational pharmacokinetic study.

SETTING

University teaching hospital in Copenhagen, Denmark.

PATIENTS

Twenty-one adult patients presenting for abdominopelvic surgery with bilateral TAP blocks were enrolled.

PROCEDURES

Ultrasound-guided TAP blocks with bilateral injections of 20 ml ropivacaine 0.5% w/v (total dose 200 mg). Blood was sampled at 0, 10, 30 and 60 min after TAP blocks.

MEASURES

Total and free peak blood concentrations (Cmax) of ropivacaine.

RESULTS

Data were analysed from N = 18 patients. The median dose of ropivacaine was 2.7 mg kg(-1) (range: 1.9-4.2 mg kg(-1)). Median total ropivacaine concentrations were 1.0, 1.6 and 1.7 μg ml(-1) at 10, 30 and 60 min, respectively. Six patients (33%) had Cmax values above 2.2 μg ml(-1) and the highest concentration measured was 5.1 μg ml(-1). One patient had a 33% drop in mean arterial blood pressure.

CONCLUSION

TAP blocks with bilateral injections of 20 ml ropivacaine 0.5% w/v gave rise to potentially toxic peak blood concentrations of total ropivacaine in one-third of the patients.

Neurolytic transversus abdominis plane block in the palliative treatment of intractable abdominal wall pain

A 45 year old man with metastatic colon cancer presented with uncontrollable abdominal wall pain. Transversus abdominis plane (TAP) block with ropivacaine and methylprednisolone was performed with excellent pain relief, which allowed a significant weaning of the patient's opioid requirements. A second TAP block was performed with a 33% ethanol solution (ethanol and ropivacaine) with excellent pain relief. The neurolytic block appeared to offer better pain control for more than 5 days after placement until the patient finally succumbed to his illness.

The role of regional anaesthesia techniques in the management of acute pain

Regional anaesthesia and analgesia techniques are used to effectively manage acute pain after a variety of surgeries. With the rapid growth of ultrasound-guided procedures, anaesthetists are re-examining regional anaesthesia and analgesia and their roles in pain management. In this evolving field previous published data may not reflect current practice. Therefore, a narrative review of recent literature was undertaken to establish the current utility and efficacy of regional anaesthesia and analgesia for the management of acute pain following surgery. Only prospective randomised controlled trials published between March 2009 and March 2011 with outcome measures of analgesia efficacy were included. Sixty-five randomised controlled trials were identified involving 4841 patients. Regional techniques for the management of knee (26%), abdominal (26%) and shoulder (14%) surgery were most frequently studied. The review provides further evidence that regional anaesthesia and analgesia can offer excellent analgesia with acceptable side-effects for the management of postsurgical pain. In addition, the results of this review support the use of ultrasound guidance when performing regional techniques and continuous catheter techniques to prolong analgesia.

Weight-based volume of injection influences cranial to caudal spread of local anesthetic solution in ultrasound-guided transversus abdominis plane blocks in canine cadavers

OBJECTIVE

To determine if the volume of injected local anesthetic solution affects cranial to caudal spread when performing ultrasound-guided transversus abdominis plane (TAP) blocks in dogs.

STUDY DESIGN

Prospective experimental study.

ANIMALS

Adult Beagle cadavers (n = 20)

METHODS

Bilateral TAP blocks using ultrasound guidance was performed in 20 Beagle cadavers (mean ± SD weight, 9.3 ± 1.4 kg) using a 1:1 solution of methylene blue/bupivacaine injected at volumes of 0.25, 0.5, 0.75, and 1.0 mL/kg. Cadavers were dissected to determine injectate spread within the transversus abdominis fascial plane.

RESULTS

The transversus abdominis fascial plane was adequately identified by ultrasonography, injected, and dissected in 38 beagle hemi-abdominal walls; injectate was not identified in 2 hemi-abdominal walls. Dermatomal spread (number of ventral nerve roots saturated by injected solution) was volume dependent (P = .026, Kruskal Wallis): 2.9 ± 0.74 nerve roots for 0.25 mL/kg; 3.4 ± 1.1 for 0.5 mL/kg; 4.0 ± 0.67 for 0.75 mL/kg; and 4.2 ± 1.2 for 1 mL/kg.

CONCLUSION

In Beagle cadavers, the volume of injected local anesthetic solution significantly affects cranial to caudal spread within the TAP during ultrasound-guided TAP blocks. The volume of local anesthetic injected could potentially be used to augment the spread of analgesic coverage for a given surgical procedure in dogs.

Clinical implications of the transversus abdominis plane block in adults

The transversus abdominis plane (TAP) block is a relatively new regional anesthesia technique that provides analgesia to the parietal peritoneum as well as the skin and muscles of the anterior abdominal wall. It has a high margin of safety and is technically simple to perform, especially under ultrasound guidance. A growing body of evidence supports the use of TAP blocks for a variety of abdominal procedures, yet, widespread adoption of this therapeutic adjunct has been slow. In part, this may be related to the limited sources for anesthesiologists to develop an appreciation for its sound anatomical basis and the versatility of its clinical application. As such, we provide a brief historical perspective on the TAP block, describe relevant anatomy, review current techniques, discuss pharmacologic considerations, and summarize the existing literature regarding its clinical utility with an emphasis on recently published studies that have not been included in other systematic reviews or meta-analyses.

Overview of anesthetic considerations for Cesarean delivery

INTRODUCTION

Physiologic changes of pregnancy uniquely influence anesthesia for Cesarean delivery. Included is a review of current obstetrical anesthesia considerations for Cesarean delivery and recent changes improving maternal care and outcome.

SOURCES OF DATA

A literature review was conducted using Pubmed and the Cochrane database.

AREAS OF AGREEMENT AND CONTROVERSY

Increased use of neuraxial techniques instead of general anesthesia for Cesarean delivery has improved maternal safety. Recent changes in the prevention of gastric aspiration, hypotension from neuraxial techniques, venous thrombosis and a team approach have improved maternal care. Elective Cesarean deliveries and management of urgent deliveries are areas of discussion.

AREAS TIMELY FOR DEVELOPING RESEARCH

Obstetric anesthesia advances have improved maternal outcomes. Current areas of needed obstetric anesthesia research include improved obese patient care, the impact of anticoagulation on neuraxial techniques in pregnancy, long-term neurocognitive effects of neonatal exposure to anesthesia and postoperative pain management.

Preemptive analgesic efficacy of ultrasound-guided transversus abdominis plane block in patients undergoing gynecologic surgery via a transverse lower abdominal skin incision

Background

The transversus abdominis plane block is recently described peripheral block to providing analgesia to the anterior abdominal wall. The goal of this study is to evaluate the analgesic efficacy of the ultrasound-guided transversus abdominis plane block (US-TAP block) in patients undergoing gynecologic surgery via a transverse lower abdominal skin incision.

Methods

Thirty-two patients undergoing gynecologic surgery were randomized to undergo standard care such as PCA, or to receive additional US-TAP block with standard care. After general anesthesia induction, a bilateral US-TAP block was performed using 0.375% ropivacaine 20 ml on each side. Postoperative demand of rescue analgesics in PACU and ward were recorded. Each patient was assessed postoperatively by a blinded investigator in the postanesthesia care unit (PACU) and at 2, 6, 10, 24, 48 hr postoperatively to investigate pain, drowsiness, nausea and itch.

Results

The US-TAP block reduced pain intensity compared to standard care in the PACU (5.2 ± 3.1 vs 8.4 ± 1.3) and at 2, 24 postoperative hours (3.0 ± 2.4 vs 5.2 ± 2.4, 0.9 ± 1.5 vs 2.2 ± 1.9). Fentanyl requirements in PACU was reduced (20.3 ± 20.9 vs 62.5 ± 35.4 µg, P < 0.05). In ward, pethidine requirements was reduced (21.9 ± 28.7 vs 56.3 ± 34.8 mg, P < 0.05).

Conclusions

The US-TAP block with standard care provide more effective analgesia after gynecologic surgery via a transverse lower abdominal skin incision.

Ultrasound-guided continuous transverse abdominis plane block for abdominal surgery

Introduction:

Transversus abdominis plane (TAP) block is a new regional analgesic technique for postoperative pain in abdominal surgery. Its efficacy is not clear, and thus it needs to be explored for its regular utilisation on prolonged period. The objective was to study the continuous local anaesthetic infusion effect on postoperative analgesia. Continuous use of TAP block as an analgesic technique has not been evaluated prospectively in clinical trials. This study evaluates the efficacy of ultrasound-guided TAP block in comparison with PCA fentanyl in major abdominal surgery.

Materials and Methods:

There were 20 patients in the study, allocated to TAP and control groups. The parameters measured were pain scores on a numerical rating scale (NRS) of 0-10 at various time intervals and the amount of fentanyl used as rescue analgesia. Patient satisfaction scores were recorded in the TAP block group and along with any complications related to the block.

Results:

The postoperative median pain scores on coughing on day one were 6.0 for control group and 2.0 for the TAP group (P = 0.02); on day two, the equivalent scores were 7.0 and 2.0 (P = 0.01). The fentanyl requirement at one hour was 203 μ for the control group and 78 μg for the TAP group (P = 0.03); at day one, the control and TAP requirements were 1237 μg and 664 μg respectively (P = 0.01). Three TAP patients rated their satisfaction as ‘excellent’, four as ‘satisfied, and two as ‘poor’.

Conclusion:

TAP block is a promising technique for postoperative analgesia in major abdominal surgeries. Our study demonstrated lower pain scores in the TAP group with reduced fentanyl requirement. Further, a large scale study is needed to establish the efficacy of TAP block in this setting.

What's new in obstetric anesthesia? The 2011 Gerard W. Ostheimer Lecture

The "What's New in Obstetric Anesthesia" lecture was established by the Society for Obstetric Anesthesia and Perinatology in 1975 to update members on the preceding year's medical literature. In 1995, the lecture was renamed in honor of Gerard W. Ostheimer, an obstetric anesthesiologist from Brigham and Women's Hospital who contributed significantly to the knowledge and practice of obstetric anesthesia. The Ostheimer lecturer reviews the obstetric anesthesia, obstetric, perinatology, and health services literature to identify articles that are relevant to the practice of obstetric anesthesiology. This review summarizes the most relevant publications from the 2010 literature.

An expert opinion on postoperative pain management, with special reference to new developments

IMPORTANCE OF THE FIELD

Recently, much attention has been directed towards the effect of opioid-sparing strategies on postoperative morbidity and hospitalization, and on different nociceptive mechanisms involved in various postoperative pain states and surgical procedures. This has resulted in an increased interest in secondary, or adjunct, analgesics and procedure-specific analgesic methods.

AREAS COVERED IN THIS REVIEW

The present paper aims to review and discuss recent developments within the field of various adjunct, systemic analgesics and local/regional anesthetic methods for management of postoperative pain, based on evidence from randomized, clinical trials published within the last 5 years.

WHAT THE READER WILL GAIN

The reader will gain insight into the current role of pregabalin, glucocorticoids and systemic lidocaine for the management of postoperative pain. In addition, the current status of local infiltration analgesia for hip and knee arthroplasty, transversus abdominis plane block for abdominal operations, and the analgesic effect of wound instillation of capsaicin are reviewed.

TAKE HOME MESSAGE

The evidence of a substantial analgesic effect of pregabalin on acute postoperative pain is questionable, and more convincing evidence of the role of glucocorticoids and systemic lidocaine is needed before they should be recommended as analgesics in daily clinical practice. Local infiltration analgesia after hip and knee arthroplasty, transversus abdominis plane block after abdominal operations and local application of capsaicin lend some promise, but there is still a lack of well-performed RCTs to draw any firm conclusions. Procedure-specific analgesic combinations within well-defined rehabilitation paradigms should be explored further to reduce adverse effects associated with the use of conventional analgesic treatment protocols, and to improve postoperative outcome.

Ultrasound-guided transversus abdominis plane block in the dog: an anatomical evaluation

OBJECTIVE

To describe the ultrasound-guided technique to the transversus abdominis plane (TAP) block in the dog and evaluate the spread of a local anesthetic/methylene blue solution.

STUDY DESIGN

Prospective experimental trial.

ANIMALS

Ten adult Beagle cadavers weighing 11.1 ± 1.1 kg (mean ± SD).

METHODS

Transversus abdominis plane (TAP) blocks were performed bilaterally by a single trained individual on unpreserved cadaver dogs using 10 mL of methylene blue/bupivacaine solution per site. Dissection of the abdominal wall was performed within 15-55 minutes of block to determine distribution of injectate and nerve involvement in the transversus abdominis fascial plane.

RESULTS

The transversus abdominis fascial plane was adequately visualized via ultrasound and injected in twenty hemi-abdominal walls. Segmental branches of T11, T12, T13, L1, L2, and L3 were adequately stained in 20%, 60%, 100%, 100%, 90%, and 30% of injections, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

This anatomical study suggests that the transversus abdominis plane (TAP) block would provide adequate regional anesthesia of the abdomen, potentially extending to the cranial and caudal limits of the abdomen. This supports the clinical potential of this block in veterinary medicine.

The Efficacy of Ultrasound-Guided Transversus Abdominis Plane Block in Patients Undergoing Hysterectomy

The study objective of this prospective, double-blind randomised controlled study was to evaluate the efficacy of ultrasound guided transversus abdominis plane (TAP) block and bupivacaine infiltration of the skin and subcutaneous tissue of the wound in patients undergoing hysterectomy. Patients were randomly allocated to three groups: a control group (n=18) and TAP block group (n=18) received bilateral TAP blocks with saline and bupivacaine respectively, and an infiltration group (n=19) received skin and subcutaneous wound tissue infiltration with bupivacaine at the end of surgery. After surgery patients received patient-controlled intravenous tramadol and were assessed for pain and tramadol consumption at 1, 2, 4, 6 and 24 hours.

Both the TAP and infiltration groups had lower movement and rest pain scores than the control group, with lower scores in the TAP group than the infiltration group at 6 and 24 hours. Total tramadol consumption was significantly lower in the TAP group than in the other groups at all time points. We concluded that ultrasound-guided TAP block reduced rest and movement pain after total abdominal hysterectomy and was more effective than superficial wound infiltration for postoperative pain management.

Is ultrasound guidance advantageous for interventional pain management? A review of acute pain outcomes

BACKGROUND

Ultrasound (US) guidance for peripheral nerve blockade has gained popularity worldwide. The reported benefits of real-time sonographic visualization compared with traditional nerve localization techniques generally apply to procedural and technical block-related outcomes whereas acute pain-related outcomes are featured less prominently. In this review, we evaluated the effect of US guidance compared with traditional nerve localization techniques for interventional management of acute pain and acute pain-related outcomes.

METHODS

We performed a systematic search of MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Clinical Trials (from January 1990 to January 2011) to identify randomized controlled trials evaluating the effects of US guidance on acute pain and related outcomes compared with traditional nerve localization techniques. Studies were excluded if they did not report at least one of the following acute pain outcomes: pain severity, opioid consumption, sensory block duration, and time to first analgesic request. Related outcomes were classified as follows: patient related (opioid-related adverse effects, patient satisfaction, postoperative cognitive deficit); anesthesia related (unwanted motor block, perineural catheter failure, morbidity, development of chronic pain); surgery related (hospital readmission, ability to ambulate); and hospital related (length of stay, cost). Promising novel applications of US guidance for acute pain management were also sought for discussion purposes.

RESULTS

We identified 23 randomized controlled trials, including 1674 patients, that compared US guidance with and without peripheral nerve stimulation with peripheral nerve stimulation alone or anatomical landmark techniques. Of the 16 studies that evaluated pain severity, 8 reported improvement with US guidance; however, only 1 study reported a difference between US guidance and the comparator of >1 interval on the numeric rating pain scale. Eight studies evaluated sensory block duration and 3 of these reported prolonged block duration with US guidance. Seven studies evaluated opioid consumption, of which 3 reported a reduction with US guidance. Three studies evaluated time to first analgesic request, of which 2 favored US guidance. We uncovered no significant differences between US guidance and traditional nerve localization techniques for any other related outcome. US guidance was not found to be inferior compared with traditional nerve localization techniques for any outcome. Nonrandomized data suggest that US-guided transversus abdominis plane blocks may offer analgesic benefit over standard analgesic therapy, but has not been compared with an anatomical landmark technique.

CONCLUSIONS

At present, there is insufficient evidence in the contemporary literature to define the effect of US guidance on acute pain and related outcomes compared with traditional nerve localization techniques for interventional acute pain management.

Comparison of analgesic efficacy of subcostal transversus abdominis plane blocks with epidural analgesia following upper abdominal surgery

Subcostal transversus abdominis plane (TAP) catheters have been reported to be an effective method of providing analgesia after upper abdominal surgery. We compared their analgesic efficacy with that of epidural analgesia after major upper abdominal surgery in a randomised controlled trial. Adult patients undergoing elective open hepatobiliary or renal surgery were randomly allocated to receive subcostal TAP catheters (n=29) or epidural analgesia (n=33), in addition to a standard postoperative analgesic regimen comprising of regular paracetamol and tramadol as required. The TAP group patients received bilateral subcostal TAP catheters and 1 mg.kg(-1) bupivacaine 0.375% bilaterally every 8 h. The epidural group patients received an infusion of bupivacaine 0.125% with fentanyl 2 μg.ml(-1) . The primary outcome measure was visual analogue pain scores during coughing at 8, 24, 48 and 72 h after surgery. We found no significant differences in median (IQR [range]) visual analogue scores during coughing at 8 h between the TAP group (4.0 (2.3-6.0 [0-7.5])) and epidural group (4.0 (2.5-5.3) [0-8.5])) and at 72 h (2.0 (0.8-4.0 [0-5]) and 2.5 (1.0-5.0 [0-6]), respectively). Tramadol consumption was significantly greater in the TAP group (p=0.002). Subcostal TAP catheter boluses may be an effective alternative to epidural infusions for providing postoperative analgesia after upper abdominal surgery.

Cesarean delivery in the obese parturient: anesthetic considerations

Obesity is a worldwide health problem and its prevalence is reaching epidemic proportions. As obesity does not spare women of childbearing age, obstetric anesthesiologists will increasingly be exposed to the challenges of anesthesia in this population. The purpose of this article is to give the reader a thorough understanding of the anesthetic implications of obesity relating to cesarean deliveries. Obesity is associated with hypertension, diabetes, obstructive sleep apnea and other comorbidities. It increases the risk of cesarean delivery, postpartum wound infections and deep venous thromboembolism. Obese parturients are prone to anesthetic complications such as aspiration of gastric contents, difficult monitoring, positioning, airway management and challenging neuraxial techniques. A thorough precesarean delivery preparation should include an evaluation by an anesthesiologist for women with a BMI over 40 kg/m² and institution of an antacid prophylaxis protocol, thromboprophylaxis and antibiotic prophylaxis. Regional anesthesia should ideally be used in all obese parturients unless contraindicated. The goals of postpartum care include efficacious analgesia, physiotherapy and early mobilization. Monitoring and vigilance in an intensive care unit or step-down units should be considered for morbidly obese women.

Use of invasive placebos in research on local anaesthetic interventions

Placebos play a vital role in clinical research, but their invasive use in the context of local anaesthetic blocks is controversial. We assessed whether recently published randomised controlled trials of local anaesthetic blocks risked harming control group patients in contravention of the Declaration of Helsinki. We developed the 'SHAM' (Serious Harm and Morbidity) scale to assess risk: grade 0 = no risk (no intervention); grade 1 = minimal risk (for example, skin allergy to dressing); grade 2 = minor risk (for example, subcutaneous haematoma, infection); grade 3 = moderate risk (with or without placebo injection) (for example, neuropraxia); and grade 4 = major risk (such as blindness, pneumothorax, or liver laceration). Placebo interventions of the 59 included trials were given a SHAM grade. Nine hundred and nineteen patients in 31 studies, including six studies with 183 children, received an invasive placebo assessed as SHAM grade ≥ 3. A high level of agreement (78%, κ = 0.80, p < 0.001) for SHAM grades 0-4 increased to 100% following discussion between assessors. More than half of the randomised controlled study designs subjected patients in control groups to risks of serious or irreversible harm. A debate on whether it is justifiable to expose control group patients to risks of serious harm is overdue.

What's new in obstetric anesthesia?

The current article covers some of the major themes that emerged in 2009 in the fields of obstetric anesthesiology, obstetrics, and perinatology, with a special emphasis on the implications for the obstetric anesthesiologist.