Systemic toxicity of levobupivacaine, bupivacaine, and ropivacaine during continuous intravenous infusion to nonpregnant and pregnant ewes

Serum Levels of Bupivacaine After Bilateral Ultrasound-Guided Deep Parasternal Intercostal Plane Block in Cardiac Surgery with Median Sternotomy

OBJECTIVE

To evaluate systemic levels of bupivacaine after bilateral ultrasound-guided deep parasternal intercostal plan (PIP) block in cardiac surgical patients undergoing median sternotomy.

DESIGN

Prospective, observational study SETTING: Single institution; academic university hospital PARTICIPANTS: Twenty-eight adult patients undergoing cardiac surgery with median sternotomy received a PIP block with 2.5 mg/kg bupivacaine with or without dexamethasone and dexmedetomidine.

MEASUREMENTS

Arterial blood samples were analyzed for total serum bupivacaine concentration at 5, 15, 30, 45, 60, 90, 120, and 150 minutes after placement of PIP. Local anesthetic volume, local anesthetic adjuncts, time to extubation, postoperative pain scores, and opioid consumption were recorded.

MAIN RESULTS

The mean peak bupivacaine concentration was 0.60 ± 0.62 µg/mL, and the mean time to maximum concentration (Tmax) was 16.92 ± 12.97 minutes. Two patients (7.1%) had a concentration >2.0 µg/mL within 15 minutes of block placement. The mean Tmax of bupivacaine was significantly greater in patients who did not receive additives compared to those patients who did (22.86 ± 14.77 minutes v 10.0 ± 5.22 minutes; p = .004). The times to extubation and postoperative pain were not improved with additives.

CONCLUSIONS

Bilateral PIP placed at the end of cardiac surgery resulted in low systemic bupivacaine levels. The inclusion of additives shortened Tmax without improving outcome.

The Implementation and Optimization of Neonatal Epidural Analgesia in a Tertiary Care Hospital: A Technical Report

Effective analgesic therapy in neonates continues to be fundamental for improving quality of life and decreasing the need for further medical intervention. When pain is not well controlled in the neonatal intensive care setting, we see an increased use of sedation pharmaceuticals, mechanical ventilation, and altered somatosensory development, among other complications. Currently, there is no standardized protocol addressing effective pain management while decreasing the need for further sedation. In this article, we seek to demonstrate how our institution standardized and implemented the utilization of epidural analgesia in neonates as the preferred method of pain management for open thoracic and abdominal surgeries.

Intravenous lipid emulsion for local anaesthetic systemic toxicity in pregnant women: a scoping review

BACKGROUND

Local anaesthetic systemic toxicity (LAST) is a rare but life-threatening complication that can occur after local anaesthetic administration. Various clinical guidelines recommend an intravenous lipid emulsion as a treatment for local anaesthetic-induced cardiac arrest. However, its therapeutic application in pregnant patients has not yet been established. This scoping review aims to systematically identify and map the evidence on the efficacy and safety of intravenous lipid emulsion for treating LAST during pregnancy.

METHOD

We searched electronic databases (Medline, Embase and Cochrane Central Register Controlled Trials) and a clinical registry (lipidrescue.org) from inception to Sep 30, 2022. No restriction was placed on the year of publication or the language. We included any study design containing primary data on obstetric patients with signs and symptoms of LAST.

RESULTS

After eliminating duplicates, we screened 8,370 titles and abstracts, retrieving 41 full-text articles. We identified 22 women who developed LAST during pregnancy and childbirth, all presented as case reports or series. The most frequent causes of LAST were drug overdose and intravascular migration of the epidural catheter followed by wrong-route drug errors (i.e. intravenous anaesthetic administration). Of the 15 women who received lipid emulsions, all survived and none sustained lasting neurological or cardiovascular damage related to LAST. No adverse events or side effects following intravenous lipid emulsion administration were reported in mothers or neonates. Five of the seven women who did not receive lipid emulsions survived; however, the other two died.

CONCLUSION

Studies on the efficacy and safety of lipids in pregnancy are scarce. Further studies with appropriate comparison groups are needed to provide more robust evidence. It will also be necessary to accumulate data-including adverse events-to enable clinicians to conduct risk-benefit analyses of lipids and to facilitate evidence-based decision-making for clinical practice.

Ultrasound-Guided Bilateral Erector Spinae Plane Block vs. Ultrasound-Guided Bilateral Posterior Quadratus Lumborum Block for Postoperative Analgesia after Caesarean Section: An Observational Closed Mixed Cohort Study

ESP block (ESPB) and posterior Quadratus Lumborum Block (pQLB) have been proposed as opioid-sparing techniques for the management of pain after abdominal surgery. Between December 2021 and October 2022, we conducted a retrospective comparative study at the delivery suite of Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Rome, Italy, to compare the efficacy of ESPB and pQLB in preventing postoperative pain after an elective caesarean section (CS). The primary outcome was total morphine consumption in the first 24 h. Secondary outcomes were time to first opioid request; Numerical Pain Rating Scale (NPRS) at 0, 2, 6, 12 and 24 h; vital signs; adverse events. Fifty-two women were included. The total cumulative dose of morphine was not significantly different between the two groups of patients (p = 0.897). Time to first dose of morphine, NPRS values and haemodynamic parameters were not statistically different between the two groups. NPRS values significantly increased (p < 0.001) at the different time intervals considered. The need for rescue doses of morphine was lower in the ESPB group compared to the pQLB group (hazard ratio of 0.51, 95% CI (0.27 to 0.95), p = 0.030). No adverse event was reported. ESPB seems to be as effective as pQLB in providing analgesia after CS.

Intralipid fails to rescue bupivacaine-induced cardiotoxicity in late-pregnant rats

Background

Females routinely receive bupivacaine for obstetric and regional anesthesia. An accidental overdose of bupivacaine can result in cardiotoxicity and cardiac arrest. Intralipid (ILP) rescues bupivacaine-induced cardiotoxicity in male rats. However, bupivacaine cardiotoxicity and ILP rescue have not been studied in non-pregnant and late-pregnant female rats. Here, we tested the hypothesis that an appropriate dose of ILP would rescue non-pregnant and late-pregnant rats from bupivacaine-induced cardiotoxicity.

Methods

Non-pregnant (n = 6) and late-pregnant (n = 7) female rats received intravenous bupivacaine (10-mg/kg bolus) to induce asystole. Resuscitation with 20% ILP (5-ml/kg actual body weight, single bolus, and 0.5-ml/kg/min maintenance) and chest compressions were continued for 10-min. Serial heart rate (HR), left ventricular ejection-fraction (LVEF%), and LV-fractional shortening (LVFS%) were recorded at baseline and 10-min after bupivacaine-induced cardiac arrest. Data are mean ± SD followed by 95% CI. P-values < 0.05 were considered statistically significant.

Results

All rats developed cardiac arrest within a few seconds after bupivacaine. All non-pregnant rats were successfully rescued by ILP, with a HR of 280 ± 32 bpm at baseline vs. 212 ± 18 bpm at 10-min post ILP (p < 0.01), LVEF of 70 ± 6% vs. 68 ± 5% (p = ns), and LVFS of 41 ± 5% vs. 39 ± 4% (p = ns). Interestingly, 6 out of 7 late-pregnant rats did not recover with ILP. Baseline HR, LVEF and LVFS for late-pregnant rats were 330 ± 40 bpm, 66 ± 5% and 38 ± 4%, respectively. At 10-min post ILP, the HR, LVEF, and LVFS were 39 ± 102 bpm (p < 0.0001), 8 ± 22% (p < 0.0001), and 5 ± 12% (p < 0.001), respectively.

Conclusions

ILP successfully rescued bupivacaine-induced cardiac arrest in non-pregnant rats, but failed to rescue late-pregnant rats.

Ultrasound-guided epidural anesthesia and sedation for open transvesical Cohen ureteric reimplantation surgery in 20 consecutive children: a prospective case series and proof-of-concept study

BACKGROUND

Epidural anesthesia is usually combined with general anesthesia (GA) for children undergoing sub-umbilical surgery and GA in children is associated with a potential for respiratory events. Aiming to reduce airway manipulation and the use of GA drugs, we designed a study of transvesical Cohen ureteteric reimplantion under epidural anesthesia in sedated, spontaneously breathing children.

METHODS

We enrolled 20 children (3-83 months, 6.3-25.0 kg) scheduled for open transvesical abdominal surgery with Pfannenstiel incision. Sedation was followed by ultrasound-guided epidural anesthesia. Increases in heart rate by > 15% and or patient movements upon skin incision were rated as block deficiencies. Intubation equipment for advanced airway management was kept on standby. The primary study endpoint was successful blockade, meaning that no sequential airway management was required for the spontaneous breathing patients during surgery. Secondary endpoints included any use of fentanyl/propofol intraoperatively and of postoperative analgesics in the recovery room.

RESULTS

All 20 blocks were successful, with no block deficiencies upon skin incision, no need for sequential airway management, and stable SpO2 levels (97-100%). Surgery took a median of 120.5 minutes (IQR: 89.3-136.5) and included one bolus of fentanyl in one patient 120 minutes into a protracted operation. No more systemic analgesia had to be provided in the recovery room.

CONCLUSIONS

Sedation and epidural anesthesia emerged as a useful alternative to GA from our consecutive case series.

Emergency Resources in Obstetrics

Utilization of emergency resources in obstetrics can help to optimize health care providers' care to pregnant and postpartum patients. There is a vast array of resources with various accessibility modalities that can be used before, during, and/or after an obstetric emergency. These resources can also be included as teaching material to increase knowledge and awareness with the aim to reduce maternal morbidity and mortality and improve patient outcomes.

Anesthetic Management of the Pregnant Patient: Part 2

Part 2 of "Anesthetic Management of the Pregnant Patient" reviews fetal development and maternal physiologic changes of interest to the dental practitioner. Part 2 of this review focuses on pharmacologic considerations, particularly the potential impact on the developing fetus. Along with a brief overview involving pharmacokinetics and pharmacodynamics of selected drugs, the following discussion focuses on currently accepted therapies and commonly used agents for pain control, sedation, and general anesthesia in the pregnant patient planned for or undergoing dental treatment.

Analgesic effect of intercostal nerve block given preventively or at the end of operation in video-assisted thoracic surgery: a randomized clinical trial

OBJECTIVE

To compare the analgesic effect of intercostal nerve block (INB) with ropivacaine when given preventively or at the end of the operation in patients undergoing video-assisted thoracic surgery (VATS).

METHODS

A total of 50 patients undergoing VATS were randomly divided into two groups. The patients in the preventive analgesia group (PR group) were given INB with ropivacaine before the intrathoracic manipulation combined with patient-controlled analgesia (PCA). The patients in the post-procedural block group (PO group) were administered INB with ropivacaine at the end of the operation combined with PCA. To evaluate the analgesic effect, postoperative pain was assessed with the visual analogue scale (VAS) at rest and Prince Henry Pain Scale (PHPS) scale at 6, 12, 24, 48, and 72 hours after surgery.

RESULTS

At 6 h and 12 h post-surgery, the VAS at rest and PHPS scores in the PR group were significantly lower than those in the PO group. There were no significant differences in pain scores between two groups at 24, 48, and 72 hours post-surgery.

CONCLUSION

In patients undergoing VATS, preventive INB with ropivacaine provided a significantly better analgesic effect in the early postoperative period (at least through 12 h post-surgery) than did INB given at the end of surgery.

Comparison of ropivacaine plasma concentration after posterior Quadratus Lumborum Block in Cesarean Section with ropivacaine with epinephrine vs plane

BACKGROUND

The posterior Quadratus Lumborum Block (pQLB) has been used in postoperative pain management after Cesarean Section (CS). However, clinicians have no data about pQLB safety in pregnants, at increased risk of local anesthetic systemic toxicity (LAST). The purpose of the present study was to explore the efficacy and the safety of adding epinephrine to ropivacaine for bilateral pQLB vs. bilateral pQLB performed with ropivacaine alone in CS.

METHODS

in this prospective trial 52 pregnants, ASA 2 physiological status, were consecutively allocated to one of 2 groups, e-pQLB and pQLB; e-pQLB group received 0.375% ropivacaine+100 mcg epinephrine, 20 ml each side; pQLB received 0.375% ropivacaine alone, 20 ml each side. The primary and secondary outcomes were to evaluate if the adjunct of epinephrine to ropivacaine increases efficacy and safety of pQLB, respectively.

RESULTS

Authors found in e-pQLB group vs. p-QLB group: a total mean morphine consumption statistically lower during the first 24 postoperative hours (5.08±3.12, vs 9.11±4.67 SD mg, p=0.0002); NRS values statistically lower at 6 hours from block, both at rest (1,73±1,88 SD vs. 2,88±2,53, p=0.03) and with movement (3,03±1,98 SD vs. 4,23±2,87, p=0.04); a longer time between block and the first opioid request (5.92±2.48 vs 3.78±2.68 SD hrs, p< 0.003); venous ropivacaine concentrations significantly lower at any time of samples but at 120 minutes.

CONCLUSIONS

Adding epinephrine to ropivacaine increases efficacy and duration of pQLB. Moreover it increases block safety, reducing peak and mean venous ropivacaine concentration.

A review of peripheral nerve blocks for cesarean delivery analgesia

Peripheral nerve blocks have a unique role in postcesarean delivery multimodal analgesia regimens. In this review article, options for peripheral nerve blocks for cesarean delivery analgesia will be reviewed, specifically paravertebral, transversus abdominis plane, quadratus lumborum, iliohypogastric and ilioinguinal, erector spinae, and continuous wound infiltration blocks. Anatomy, existing literature evidence, and specific areas in need of future research will be assessed. Considerations for local anesthetic toxicity, and for informed consent for these modalities in the context of emergency cesarean deliveries, will be presented.

Linoleic Acid Attenuates the Toxic Dose of Bupivacaine-Mediated Reduction of Vasodilation Evoked by the Activation of Adenosine Triphosphate-Sensitive Potassium Channels

The goal of this study was to investigate the effect of lipid emulsion on a toxic dose of local anesthetic-mediated reduction of vasodilation evoked by the ATP-sensitive potassium (K_ATP) channel agonist levcromakalim. The effect of lipid emulsion (LE) and linoleic acid on the local anesthetic-mediated reduction of vasodilation and membrane hyperpolarization evoked by levcromakalim was assessed in isolated endothelium-denuded vessels (rat aorta and mesenteric artery) and aortic vascular smooth muscle cells. The effect of LE and linoleic acid on K_ATP channel activity in transfected HEK-293 cells was investigated, as was the effect of LE on bupivacaine concentration. The efficacy of LE in attenuating the local anesthetic-mediated reduction of vasodilation evoked by levcromakalim was correlated with the lipid solubility of the local anesthetic. Linoleic acid attenuated the bupivacaine-mediated reduction of vasodilation evoked by levcromakalim. LE decreased the bupivacaine-mediated reduction of membrane hyperpolarization evoked by levcromakalim but did not significantly alter the mepivacaine-mediated reduction. LE and linoleic acid both reversed the bupivacaine-mediated decrease of K_ATP activity and enhanced K_ATP activity. LE decreased the bupivacaine concentration. Linoleic acid may be the major contributor to LE-induced attenuation of bupivacaine-mediated reduction of vasodilation evoked by levcromakalim via the direct activation of K_ATP channels and indirect effects.

Role of ultrasound guided transversus abdominis plane block as a component of multimodal analgesic regimen for lower segment caesarean section: a randomized double blind clinical study

Background

While opioids are the mainstay for post-operative analgesia after lower segment caesarean section, they are associated with various untoward effects. Ultrasound guided transversus abdominis plane (TAP) block has been postulated to provide effective analgesia for caesarean section. We evaluated the analgesic efficacy of this block for post caesarean analgesia in a randomised controlled trial.

Methods

One hundred thirty-nine mothers undergoing caesarean delivery were randomised to receive TAP block with either 20 ml 0.375% ropivacaine or 20 ml saline after obtaining informed consent. All the subjects received a standard spinal anaesthetic and diclofenac was administered for post-operative pain. Breakthrough pain was treated with tramadol. Post-operatively, all the subjects were assessed at 0, 2, 4, 6, 8, 10, 12, 18 & 24 h. The primary outcome was the time to first analgesic request. The secondary measures of outcome were pain, nausea, sedation, number of doses of tramadol administered and satisfaction with the pain management.

Results

The median (interquartile range) time to first analgesic request was prolonged in the TAP group compared to the control group (p < 0.0001); 11 h (8,12) and 4 h (2.5,6) respectively. The median (interquartile range) number of doses of tramadol consumed in the TAP group was 0 (0,1) compared to 2 (1,2) in the control group (p < 0.0001). At all points in the study, pain scores both at rest and on movement were lower in the study group (p < 0.0001). Maternal satisfaction with pain relief was also higher in the study group (p 0.0002). One subject in the TAP group had convulsions following injection of local anaesthetic solution. She was managed conservatively with supportive treatment following which she recovered.

Conclusion

TAP block reduces pain, prolongs the duration of analgesia and decreases supplemental opioid consumption when used for multimodal analgesia for pain relief after caesarean section. However, the risk of local anaesthetic systemic toxicity remains unknown with this block. Hence larger safety trials and measures to limit this complication need to be ascertained.

Trial registration

The trial was registered with the Clinical Trial Registry of India (CTRI/2017/03/008194) on 23/03/2017 (trial registered retrospectively).

Recovery From Ropivacaine-Induced or Levobupivacaine-Induced Cardiac Arrest in Rats: Comparison of Lipid Emulsion Effects

BACKGROUND

Lipid emulsion treatment appears to have application in the treatment of local anesthetic-induced cardiac arrest. To examine whether the efficacy of lipid resuscitation in the treatment of local anesthetic-induced cardiac arrest is affected by lipophilicity, the effects of lipid infusions were compared between levobupivacaine-induced (high lipophilicity) and ropivacaine-induced (lower lipophilicity) rat cardiac arrest model.

METHODS

A total of 28 female Sprague-Dawley rats were anesthetized using sevoflurane, which subsequently underwent tracheostomy, followed by femoral artery and vein cannulation. Two hours after the discontinuation of sevoflurane, either levobupivacaine 0.2% (n = 14) or ropivacaine 0.2% (n = 14) was administered at a rate of 2 mg/kg/min to the awake rats. When the pulse pressure decreased to 0, the infusion of local anesthetic was discontinued, and treatment with chest compressions and ventilation with 100% oxygen were immediately initiated. The total doses of local anesthetics needed to trigger the first seizure and pulse pressure of 0 mm Hg were calculated. The 2 groups were each subdivided into a lipid emulsion group (n = 7) and a control group (n = 7). In the lipid emulsion group, 20% lipid emulsion was administered intravenously (5 mL/kg bolus plus continuous infusion of 0.5 mL/kg/min), while in the control group, the same volume of normal saline was administered. Chest compressions were discontinued when the rate-pressure product had increased by more than 20% of baseline.

RESULTS

The cumulative doses of levobupivacaine and ropivacaine that produced seizures and 0 pulse pressure showed no significant difference. Mean arterial blood pressure (MAP) values were higher in the levobupivacaine group than in the ropivacaine group after resuscitation was initiated (P < .05). In levobupivacaine-induced cardiac arrest, heart rate and MAP values were higher in the lipid group than in the control group after starting resuscitation (P < .05); all rats in the lipid group achieved spontaneous circulation (rate-pressure product >20% baseline), while only 2 of 7 rats in the control group achieved spontaneous circulation at 10 minutes. In ropivacaine-induced cardiac arrest, there were no significant differences in heart rate and MAP between the lipid and control groups from the start of resuscitation to 10 minutes; spontaneous circulation returned in 6 of 7 lipid group rats, but in only 2 of 7 control group rats at 10 minutes.

CONCLUSIONS

Lipid emulsion treatment was more effective for levobupivacaine-induced cardiac arrest than for ropivacaine-induced cardiac arrest. Although lipid therapy is also effective for ropivacaine-induced cardiac arrest, it takes more time than in levobupivacaine-induced cardiac arrest. This suggests that the lipophilicity of local anesthetics influences the efficacy of lipid infusion when treating cardiac arrest caused by these drugs.

Effect of intercostal nerve block combined with general anesthesia on the stress response in patients undergoing minimally invasive mitral valve surgery

The aim of the present study was to investigate the effect of intercostal nerve block combined with general anesthesia on the stress response and postoperative recovery in patients undergoing minimally invasive mitral valve surgery (MIMVS). A total of 30 patients scheduled for MIMVS were randomly divided into two groups (n=15 each): Group A, which received intercostal nerve block combined with general anesthesia and group B, which received general anesthesia alone. Intercostal nerve block in group A was performed with 0.5% ropivacaine from T3 to T7 prior to anesthesia induction. In each group, general anesthesia was induced using midazolam, sufentanil, propofol and vecuronium. Central venous blood samples were collected to determine the concentrations of cortisol, glucose, interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) at the following time points: During central venous catheterization (T₁), 5 min prior to cardiopulmonary bypass (T₂), perioperative (T₃) and 24 h following surgery (T₄). Clinical data, including parameters of opioid (sufentanil) consumption, time of mechanical ventilation, duration of intensive care unit (ICU) stay, visual analog scale scores and any complications arising from intercostal nerve block, were recorded. Levels of cortisol, glucose, IL-6 and TNF-α in group A were significantly lower than those in group B at T₂ (all P<0.001; cortisol, P<0.05), T₃ (all P<0.001) and T₄ (all P<0.001; glucose, P<0.05), suggesting that intercostal nerve block combined with general anesthesia may inhibit the stress response to MIMVS. Additionally, intercostal nerve block combined with general anesthesia may significantly reduce sufentanil consumption (P<0.001), promote early tracheal extubation (P<0.001), shorten the duration of ICU stay (P<0.01) and attenuate postoperative pain (P<0.001), compared with general anesthesia alone. Thus, these results suggest that intercostal nerve block combined with general anesthesia conforms to the concept of rapid rehabilitation surgery and may be suitable for clinical practice.

Effects of scalp block with bupivacaine versus levobupivacaine on haemodynamic response to head pinning and comparative efficacies in postoperative analgesia: A randomized controlled trial

Objective

This study was performed to determine the effects of scalp blocks with bupivacaine versus levobupivacaine on the haemodynamic response during craniotomy and the efficacies and analgesic requirements of these drugs postoperatively.

Methods

This randomized, prospective, placebo-controlled, double-blind study included 90 patients (age, 18–85 years; American Society of Anesthesiologists physical status, I or II). The patients were randomly divided into three groups: those who received 20 mL of 0.5% bupivacaine (Group B, n = 30), 20 mL of 0.5% levobupivacaine (Group L, n = 30), or saline as a placebo (Group C, n = 30). Scalp blocks were performed 5 min before head pinning. The primary outcome was the mean arterial pressure (MAP), and the secondary outcomes were the heart rate (HR), visual analogue scale (VAS) scores, and additional intraoperative and postoperative drug use. Postoperative pain was evaluated using a 10-cm VAS.

Results

During head pinning and incision, the MAP and HR were significantly higher in Group C. The additional drug requirement for intraoperative hypertension and tachycardia was significantly higher in Group C. There were no significant differences in MAP, HR, or VAS scores between Groups B and L.

Conclusion

Both bupivacaine and levobupivacaine can be effectively and safely used for scalp blocks to control haemodynamic responses and postoperative pain.

A Lipid Emulsion Reverses Toxic-Dose Bupivacaine-Induced Vasodilation during Tyrosine Phosphorylation-Evoked Contraction in Isolated Rat Aortae

The goal of this in vitro study was to examine the effect of a lipid emulsion on toxic-dose bupivacaine-induced vasodilation in a model of tyrosine phosphatase inhibitor sodium orthovanadate-induced contraction in endothelium-denuded rat aortae and to elucidate the associated cellular mechanism. The effect of a lipid emulsion on vasodilation induced by a toxic dose of a local anesthetic during sodium orthovanadate-induced contraction was examined. In addition, the effects of various inhibitors, either bupivacaine alone or a lipid emulsion plus bupivacaine, on protein kinase phosphorylation induced by sodium orthovanadate in rat aortic vascular smooth muscle cells was examined. A lipid emulsion reversed the vasodilation induced by bupivacaine during sodium orthovanadate-induced contraction. The lipid emulsion attenuated the bupivacaine-mediated inhibition of the sodium orthovanadate-induced phosphorylation of protein tyrosine, c-Jun NH₂-terminal kinase (JNK), myosin phosphatase target subunit 1 (MYPT1), phospholipase C (PLC) γ-1 and extracellular signal-regulated kinase (ERK). These results suggest that a lipid emulsion reverses toxic-dose bupivacaine-induced vasodilation during sodium orthovanadate-induced contraction via the activation of a pathway involving either tyrosine kinase, JNK, Rho-kinase and MYPT1 or tyrosine kinase, PLC γ-1 and ERK, and this reversal is associated with the lipid solubility of the local anesthetic and the induction of calcium sensitization.

Feasibility and pharmacokinetics of caudal blockade in children and adolescents with 30-50 kg of body weight

BACKGROUND

Caudal blockade, although an important technique of pediatric regional anesthesia, is rarely used in children heavier than 30 kg. This reservation is due to anatomical concerns and lack of pharmacokinetic data. We therefore set out to evaluate, in pediatric patients weighing 30-50 kg, the feasibility of ultrasound-guided caudal blockade and the pharmacokinetics of caudally administered ropivacaine.

METHODS

Twenty consecutive children were included. General anesthesia was used to ensure a secured airway. For the caudal punctures, we applied the same clinical standards as in smaller children, administering ropivacaine 3.1 mg·ml^-1 for a volume of 1 ml·kg^-1 via ultrasound guidance. Pharmacokinetic analysis was based on total plasma ropivacaine levels and included maximum concentration (C_max ), time to C_max (t_max ), terminal elimination half-life, area under the concentration-time curve for the 4-h sampling period, apparent total body clearance, and apparent volume of distribution.

RESULTS

In all 19 cases of successful puncture, we identified the relevant anatomical structures (sacral cornua, sacral hiatus, dura mater) and verified correct administration of the local anesthetic by visualizing its cranial spread. Surgical blockade was successful in 18 of 20 cases (90%; one puncture was technically not possible and one child received intraoperatively 50 μg fentanyl). The pharmacokinetic profile of the administered ropivacaine 3.1 mg·ml^-1 indicated plasma levels within safe ranges in pediatric patients weighing 30-50 kg.

CONCLUSIONS

Based on our pharmacodynamic and pharmacokinetic results, we suggest that the body weight of 50 kg it is feasible to perform effective and safe caudal blockade in children up to 50 kg body weight.

Lipid emulsion inhibits vasodilation induced by a toxic dose of bupivacaine by suppressing bupivacaine-induced PKC and CPI-17 dephosphorylation but has no effect on vasodilation induced by a toxic dose of mepivacaine

Background

The goal of this in vitro study was to investigate the effect of lipid emulsion on vasodilation caused by toxic doses of bupivacaine and mepivacaine during contraction induced by a protein kinase C (PKC) activator, phorbol 12,13-dibutyrate (PDBu), in an isolated endothelium-denuded rat aorta.

Methods

The effects of lipid emulsion on the dose-response curves induced by bupivacaine or mepivacaine in an isolated aorta precontracted with PDBu were assessed. In addition, the effects of bupivacaine on the increased intracellular calcium concentration ([Ca²⁺]_i) and contraction induced by PDBu were investigated using fura-2 loaded aortic strips. Further, the effects of bupivacaine, the PKC inhibitor GF109203X and lipid emulsion, alone or in combination, on PDBu-induced PKC and phosphorylation-dependent inhibitory protein of myosin phosphatase (CPI-17) phosphorylation in rat aortic vascular smooth muscle cells (VSMCs) was examined by western blotting.

Results

Lipid emulsion attenuated the vasodilation induced by bupivacaine, whereas it had no effect on that induced by mepivacaine. Lipid emulsion had no effect on PDBu-induced contraction. The magnitude of bupivacaine-induced vasodilation was higher than that of the bupivacaine-induced decrease in [Ca²⁺]_i. PDBu promoted PKC and CPI-17 phosphorylation in aortic VSMCs. Bupivacaine and GF109203X attenuated PDBu-induced PKC and CPI-17 phosphorylation, whereas lipid emulsion attenuated bupivacaine-mediated inhibition of PDBu-induced PKC and CPI-17 phosphorylation.

Conclusions

These results suggest that lipid emulsion attenuates the vasodilation induced by a toxic dose of bupivacaine via inhibition of bupivacaine-induced PKC and CPI-17 dephosphorylation. This lipid emulsion-mediated inhibition of vasodilation may be partly associated with the lipid solubility of local anesthetics.

Effects of Acidification and Alkalinization on the Lipid Emulsion-Mediated Reversal of Toxic Dose Levobupivacaine-Induced Vasodilation in the Isolated Rat Aorta

The goal of this in vitro study was to examine the effects of pre-acidification and pre-akalinization on the lipid emulsion-mediated reversal of toxic dose levobupivacaine-induced vasodilation in isolated rat aorta. Isolated aortic rings with and without the nitric oxide synthase inhibitor N(ω)-nitro-L-arginine methyl ester (L-NAME) were exposed to four types of Krebs solution (pH 7.0, 7.2, 7.4, and 7.6), followed by the addition of 60 mM potassium chloride. When the toxic dose of levobupivacaine (3 × 10(-4) M) produced a stable and sustained vasodilation in the isolated aortic rings that were precontracted with 60 mM potassium chloride, increasing lipid emulsion concentrations (SMOFlipid(®): 0.24, 0.48, 0.95 and 1.39%) were added to generate concentration-response curves. The effects of mild pre-acidification alone and mild pre-acidification in combination with a lipid emulsion on endothelial nitric oxide synthase (eNOS) phosphorylation in human umbilical vein endothelial cells were investigated by Western blotting. Mild pre-acidification caused by the pH 7.2 Krebs solution enhanced the lipid emulsion-mediated reversal of levobupivacaine-induced vasodilation in isolated endothelium-intact aortic rings, whereas mild pre-acidification caused by the pH 7.2 Krebs solution did not significantly alter the lipid emulsion-mediated reversal of the levobupivacaine-induced vasodilation in isolated endothelium-denuded aortic rings or endothelium-intact aortic rings with L-NAME. A lipid emulsion attenuated the increased eNOS phosphorylation induced by the pH 7.2 Krebs solution. Taken together, these results suggest that mild pre-acidification enhances the lipid emulsion-mediated reversal of toxic dose levobupivacaine-induced vasodilation in the endothelium-intact aorta via the inhibition of nitric oxide.

Lipid emulsion attenuates apoptosis induced by a toxic dose of bupivacaine in H9c2 rat cardiomyoblast cells

The goal of this in vitro study was to investigate the effect of lipid emulsion on apoptosis induced by a toxic dose of bupivacaine (BPV) in H9c2 rat cardiomyoblast cell lines. The effect of lipid emulsion on the decreased cell viability and count induced by BPV or mepivacaine (MPV) in the H9c2 cells was assessed using an 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl tetrazolium bromide assay or a cell count assay. The effect of BPV or lipid emulsion combined with BPV on cleaved caspase 3, caspase 8, and Bax in H9c2 cells was investigated using Western blotting. A terminal deoxynucleotidyl transferase dUTP2'-deoxyuridine 5'-triphosphate nick end-labeling (TUNEL) assay was performed to detect apoptosis of H9c2 cells treated with BPV alone or lipid emulsion combined with BPV. The magnitude of lipid emulsion-mediated attenuation of decreased cell viability induced by BPV was higher than that of lipid emulsion-mediated attenuation of decreased cell viability induced by MPV. Lipid emulsion attenuated the increases in cleaved caspase 3, caspase 8 and Bax induced by BPV. Lipid emulsion attenuated the increases in TUNEL-positive cells induced by BPV. These results suggest that lipid emulsion attenuates a toxic dose of BPV-induced apoptosis via inhibition of the extrinsic and intrinsic apoptotic pathways. The protective effect of lipid emulsion may be partially associated with the relatively high lipid solubility of BPV.

Effectiveness of retigabine against levobupivacaine-induced central nervous system toxicity: a prospective, randomized animal study

PURPOSE

KCNQ2/3 channels play an important role in controlling neuronal excitability. Agents that decrease KCNQ2/3 current amplitudes are proconvulsant, whereas KCNQ2/3 current enhancers are anticonvulsant. Levobupivacaine is able to block the KCNQ2/3 channels and enhance neuronal excitation, whereas retigabine is able to reopen the channels and thus reduce overexcitation of neurons. In this study, we aimed to determine if retigabine is able to abolish local-anesthetic-induced seizures.

METHODS

Twenty New Zealand rabbits were randomly divided into two groups of ten. Levobupivacaine (0.5 %) was infused into conscious rabbits via the marginal ear vein at 8 ml/kg/h until the rabbits seized, and 5 mg/kg of retigabine were injected intravenously to terminate the seizure. The corresponding volume of saline was used as a control. The behavior of and the electroencephalogram (EEG) for each rabbit were continually monitored. Before levobupivacaine infusion, the rabbits were placed in a prostrate position calmly on the experimental platform, and the EEG pattern exhibited β waves. Intravenous levobupivacaine induced a typical EEG seizure characterized by multiple spike and slow wave complexes. The EEG changes were accompanied by behavioral convulsions which were characterized by clonic activity and opisthotonus.

RESULTS

Retigabine effectively terminated the electrographic and behavioral seizures. After receiving 5 mg/kg of retigabine, the animals became drowsy, and the EEG changed to δ waves.

CONCLUSIONS

We propose that KCNQ2/3 channels play an important role in levobupivacaine-induced central nervous system toxicity, and a KCNQ2/3 channel activator may be used to treat levobupivacaine-induced convulsions.

Epidural levobupivacaine alone or combined with different morphine doses in bitches under continuous propofol infusion

The aim of this study was to assess the cardiopulmonary, analgesic, adverse effects, serum concentration of cortisol and plasma levels of levobupivacaine and morphine in bitches undergoing propofol anesthesia and epidural analgesia with levobupivacaine alone or combined with morphine. This was a randomized 'blinded' prospective clinical study using 32 adult bitches weighing 9.8±4.1kg that were admitted for elective ovariohysterectomy. Twenty minutes after administration of acepromazine and midazolam, anesthesia was induced with propofol (4mg kg-1) and maintained by a continuous rate infusion (CRI). Each animal was randomly assigned to one of four epidural groups: GL = levobupivacaine alone (0.33mg kg-1); GLM0.1 = levobupivacaine and morphine (0.1mg kg-1); GLM0.15 = levobupivacaine and morphine (0.15mg kg-1); and GLM0.2 = levobupivacaine and morphine (0.2mg kg-1). Variables obtained during anesthesia were heart rate, respiratory rate, systolic, mean and diastolic arterial blood pressures, oxyhemoglobin saturation, inspired oxygen fraction, end-tidal carbon dioxide tension, blood gases, serum cortisol, and plasma levels of levobupivacaine and morphine. The onset and duration times of the blockade were recorded. Arterial pressures were significantly increased in all groups at the times of ovarian pedicle clamping. There was a decrease in pH, together with an increase in both PaO2and PaCO2 over time. Serum cortisol levels were increased in TESu compared to TB, T30 and TR. Limb spasticity, muscle tremors, opisthotonos and diarrhea were observed in some animals during propofol infusion and ceased with the end of CRI. Reactions happened at different moments and lasted for different periods of time in each individual. Epidural with levobupivacaine alone or combined with morphine allowed for ovariohysterectomy to be performed under low propofol infusion rates, with minimal changes in cardiovascular variables and in serum cortisol levels. Adverse effects were observed in very few animals in each group.

Lipid Emulsion Inhibits Vasodilation Induced by a Toxic Dose of Bupivacaine via Attenuated Dephosphorylation of Myosin Phosphatase Target Subunit 1 in Isolated Rat Aorta

Lipid emulsions are widely used for the treatment of systemic toxicity that arises from local anesthetics. The goal of this in vitro study was to examine the cellular mechanism associated with the lipid emulsion-mediated attenuation of vasodilation induced by a toxic dose of bupivacaine in isolated endothelium-denuded rat aorta. The effects of lipid emulsion on vasodilation induced by bupivacaine, mepivacaine, and verapamil were assessed in isolated aorta precontracted with phenylephrine, the Rho kinase stimulant NaF, and the protein kinase C activator phorbol 12,13-dibutyrate (PDBu). The effects of Rho kinase inhibitor Y-27632 on contraction induced by phenylephrine or NaF were assessed. The effects of bupivacaine on intracellular calcium concentrations ([Ca(2+)]i) and tension induced by NaF were simultaneously measured. The effects of bupivacaine alone and lipid emulsion plus bupivacaine on myosin phosphatase target subunit 1 (MYPT1) phosphorylation induced by NaF were examined in rat aortic vascular smooth muscle cells. In precontracted aorta, the lipid emulsion attenuated bupivacaine-induced vasodilation but had no effect on mepivacaine-induced vasodilation. Y-27632 attenuated contraction induced by either phenylephrine or NaF. The lipid emulsion attenuated verapamil-induced vasodilation. Compared with phenylephrine-induced precontracted aorta, bupivacaine-induced vasodilation was slightly attenuated in NaF-induced precontracted aorta. The magnitude of the bupivacaine-induced vasodilation was higher than that of a bupivacaine-induced decrease in [Ca(2+)]i. Bupivacaine attenuated NaF-induced MYPT1 phosphorylation, whereas lipid emulsion pretreatment attenuated the bupivacaine-induced inhibition of MYPT1 phosphorylation induced by NaF. Taken together, these results suggest that lipid emulsions attenuate bupivacaine-induced vasodilation via the attenuation of inhibition of MYPT1 phosphorylation evoked by NaF.

Age and bupivacaine plasma concentrations following radical cystectomy

PURPOSE

Continuous epidural analgesia with bupivacaine for postoperative analgesia can increase its plasma concentrations. Whether this effect can be aggravated with increasing age is unknown. Therefore, bupivacaine concentrations were prospectively monitored in patients undergoing radical cystectomies.

METHODS

We analyzed plasma concentrations of bupivacaine in 38 consecutive patients scheduled for radical cystectomy. All patients received general and epidural anesthesia (10 ml bupivacaine 0.5% followed by bupivacaine 0.375% every 90 min) and postoperative continuous epidural analgesia (bupivacaine 0.25% with sufentanil 0.5 μg/ml). For 4 subsequent days, bupivacaine plasma concentrations were measured and the correlation of bupivacaine plasma concentrations with the patient's age were analyzed. Data (mean ± SD) were analyzed by 2-way ANOVA with post hoc analysis or regression analysis.

RESULTS

The median age of the patients was 70 years (range 41-86). Postoperatively, bupivacaine plasma concentrations increased significantly. No correlation of plasma concentrations and age could be found. Maximal bupivacaine concentrations of the younger patients were not different from the older patients. No neurological or cardiovascular symptoms of bupivacaine intoxication were found.

CONCLUSION

In conclusion, continuous epidural administration of bupivacaine leads to increasing plasma concentrations. No age dependent differences in bupivacaine plasma concentrations could be found. Therefore, in our patients with intact liver function, we did not find a reason for an age-related restriction in the use of continuous epidural analgesia.

Comparative study related to cardiovascular safety between bupivacaine (S75-R25) and ropivacaine in brachial plexus block

BACKGROUND AND OBJECTIVES

Bupivacaine is a first choice for regional anesthesia considering its effectiveness, long duration and less motor blockade. Bupivacaine (S75-R25) is a mixture of optical isomers containing 75% levobupivacaine (S-) and 25% dextrobupivacaine (R+) created by a Brazilian pharmaceutical company. This investigation compared cardiac safety and efficacy of bupivacaine S75-R25 with vasoconstrictor and ropivacaine for brachial plexus blockade.

METHODS

Patients were randomized to receive brachial plexus anesthesia with either bupivacaine S75-R25 with epinephrine 1:200,000 (bupi) or ropivacaine (ropi), both at 0.50%, in 30 mL solution. We registered a continuous Holter ECG throughout the procedure, as well as the Lovett scale of force in addition to monitoring (heart rate, pulse oximetry and non-invasive blood pressure). The incidence of adverse events was compared with the chi-square or Fisher test.

RESULTS

We allocated forty-four patients into two groups. They did not show any difference related to age, weight or height, gender, as well as for surgical duration. Supraventricular arrhythmias were not different before or after the plexus blockade, independent of the local anesthetic chosen. Loss of sensitivity was faster for the bupivacaine group (23.1 ± 11.7 min) compared to the ropivacaine one (26.8 ± 11.5 min), though not significant (p = 0.205, Student t). There was a reduction in the cardiac rate, observed during the twenty-four-hour Holter monitoring.

CONCLUSIONS

This study showed similar efficacy between bupivacaine S75-R25 for brachial plexus blockade and ropivacaine, with similar incidences of supraventricular arrhythmias.

Comparative study related to cardiovascular safety between bupivacaine (S75-R25) and ropivacaine in brachial plexus block

BACKGROUND AND OBJECTIVES

Bupivacaine is a fi rst choice for regional anesthesia considering its effectiveness, long duration and less motor blockade. Bupivacaine (S75-R25) is a mixture of optical isomers containing 75% levobupivacaine (S-) and 25% dextrobupivacaine (R+) created by a Brazilian pharmaceutical company. This investigation compared cardiac safety and efficacy of bupivacaine S75-R25 with vasoconstrictor and ropivacaine for brachial plexus blockade.

METHODS

Patients were randomized to receive brachial plexus anesthesia with either bupivacaine S75-R25 with epinephrine 1:200,000 (bupi) or ropivacaine (ropi), both at 0.50%, in 30 mL solution.We registered a continuous Holter ECG throughout the procedure, as well as the Lovett scale of force in addition to monitoring (heart rate, pulse oximetry and non-invasive blood pressure). The incidence of adverse events was compared with the chi-square or Fisher test.

RESULTS

We allocated forty-four patients into two groups. They did not show any difference related to age, weight or height, gender, as well as for surgical duration. Supraventricular arrhythmias were not different before or after the plexus blockade, independent of the local anestheticchosen. Loss of sensitivity was faster for the bupivacaine group (23.1 ± 11.7 min) compared to the ropivacaine one (26.8 ± 11.5 min), though not significant (p = 0.205, Student t). There was a reduction in the cardiac rate, observed during the twenty-four-hour Holter monitoring.

CONCLUSIONS

This study showed similar efficacy between bupivacaine S75-R25 for brachial plexus blockade and ropivacaine, with similar incidences of supraventricular arrhythmias.

Biodegradable poly([D,L]-lactide-co-glycolide) nanofibers for the sustainable delivery of lidocaine into the epidural space after laminectomy

AIM

We developed biodegradable, lidocaine-embedded poly([D,L]-lactide-co-glycolide) nanofibers for epidural analgesia to reduce the severe pain in rats after laminectomies.

MATERIALS & METHODS

Nanofibers were prepared by an electrospinning process and were introduced into the epidural space of rats after laminectomy. The lidocaine concentration, postoperative bodyweight change and amount of food/water intake were monitored to evaluate the analgesic effectiveness of the drug-eluting nanofibers.

RESULTS

It was demonstrated that the nanofibers provided a sustained release of lidocaine for more than 2 weeks, and the local pharmaceutical concentration was much higher than the concentration in plasma. Rats that received laminectomies without nanofibers exhibited the greatest bodyweight reduction. The food/water intake and activity performance were significantly higher in rats receiving laminectomies with nanofibers than in rats without nanofibers.

CONCLUSION

The results of this study suggest that the lidocaine-loaded nanofibers can provide an easy, practical and safe means of achieving effective postlaminectomy analgesia.

The effect of magnesium added to levobupivacaine for femoral nerve block on postoperative analgesia in patients undergoing ACL reconstruction

PURPOSE

The aim of this prospective randomised double-blind study is to investigate the effect of magnesium added to local anaesthetics on postoperative VAS scores, total opioid consumption, time to first mobilisation, patient satisfaction and rescue analgesic requirements in arthroscopic ACL reconstruction surgery.

METHODS

A total of 107 American Society of Anaesthesiologists physical status grade I and II patients between 18 and 65 years of age who were scheduled to undergo elective anterior crucial ligament (ACL) reconstruction with hamstring autografts were enrolled in the study. The patients were randomly allocated to Groups L (n = 51) and LM (n = 56) using the closed-envelope method. Group LM was administered 19 ml of 0.25% levobupivacaine and 1 ml of 15% magnesium sulphate, while Group L was administered 20 ml of 0.25% levobupivacaine for femoral blockade. General anaesthesia was administered using laryngeal airway masks following neural blockade in both groups. The patients were evaluated for heart rate and mean arterial pressure, oxygen saturation, visual analogue score (VAS), verbal rating scale (VRS), rescue analgesic requirements, total opioid consumption, side effects and time to first mobilisation at the 1st, 2nd, 4th, 6th, 12th and 24th hours postoperatively.

RESULTS

There was no statistically significant difference in terms of demographic data, mean arterial pressure, heart rate or oxygen saturation between groups. The area under the curve VAS and VRS scores were lower at 4, 6, 12 and 24 h in Group LM (p = 0.001, p = 0.016, respectively). The rescue analgesic requirement and the total opioid consumption were significantly lower in Group LM (p = 0.015, p = 0.019, respectively). The time to first mobilisation and the Likert score (completely comfortable; quite comfortable; slight discomfort; painful; very painful) were higher, and the block onset time was lower in Group LM (p = 0.014 and p = 0.012, respectively). There was no difference in terms of side effects.

CONCLUSIONS

The addition of magnesium to levobupivacaine prolongs the sensory and motor block duration without increasing side effects, enhances the quality of postoperative analgesia and increases patient satisfaction; however, the addition of magnesium delays the time to first mobilisation and decreases rescue analgesic requirements.

Electrocardiographic and blood pressure alterations caused by intravenous injection of ropivacaine - a study in piglets

OBJECTIVES

Objective signs to detect inadvertent intravascular injection of local anesthetics are essential in the anesthetized pediatric patient. For early detection of intravenous bupivacaine administration, it was shown that an epinephrine containing test dose reliably provoked T-wave alterations, changes in heart rate (HR) and blood pressure, whereas intravenous injection of plain bupivacaine could not be detected until high doses were applied. This study investigates electrocardiographic and hemodynamic alterations caused by intravenous ropivacaine.

METHODS

Twenty-four piglets, anesthetized with sevoflurane, were randomized into two groups: Group R received as test dose plain ropivacaine 0.2% and group RE, ropivacaine 0.2% + epinephrine 5 μg·ml(-1) . Under stable conditions, 0.2 ml kg(-1) of the test solution was intravenously injected. Twenty minutes later, 0.4 ml kg(-1) was applied. A positive effect was defined as HR increase ≥ 10 bpm, increase in mean arterial pressure (MAP) ≥ 15 mmHg, T-wave increase ≥ 25% baseline. In another setting ropivacaine was intravenously infused until cardiac arrest.

RESULTS

After injection of 0.2 or 0.4 ml kg(-1) test solution, a positive increase in HR and MAP was found in 0% of group R and in 100% of group RE. An increase in T-wave ≥ 25% was found in 42% of group R and in 100% of group RE. During intoxication, T-elevation was seen in 83%.

CONCLUSIONS

An epinephrine containing test dose ropivacaine reliably provoked T-wave elevations and increases in HR and MAP. A small dose plain ropivacaine caused T-elevations in a remarkable percentage, whereas higher, quite toxic doses provoked T-elevations in most of the pigs.

[Pediatric caudal anesthesia : importance and aspects of safety concerns]

Caudal block is a safe procedure commonly used for pediatric perioperative analgesia. Complications are extremely rare but nevertheless local and systemic contraindications must be excluded. Optimal safety and quality result when strict attention is paid to technical details. These are discussed in detail in this review. A local anesthetic (LA) containing epinephrine allows early detection of inadvertent intravascular LA administration; therefore an epinephrine/LA mixture is recommended at least for the test dose. In terms of safety the choice of LA itself is probably of secondary importance. Clonidine as an adjuvant has an excellent risk/benefit profile with minimal side effects. Inadvertent systemic LA intoxication is a rare but potentially fatal complication of regional anesthesia and measures for prevention and early detection are essential. Should circulatory arrest occur, immediate resuscitation following standard guidelines is to be initiated including the use of epinephrine as the first line drug. Intravenous administration of lipid solutions may be beneficial as a secondary adjunct to stabilize hemodynamics but is not an alternative to epinephrine.

[Pediatric caudal anesthesia: importance and aspects of safety concerns]

Caudal block is a safe procedure commonly used for pediatric perioperative analgesia. Complications are extremely rare but nevertheless local and systemic contraindications must be excluded. Optimal safety and quality result when strict attention is paid to technical details. A local anesthetic (LA) containing epinephrine allows early detection of inadvertent intravascular LA administration; therefore an epinephrine/LA mixture is recommended at least for the test dose. In terms of safety the choice of LA itself is probably of secondary importance. Clonidine as an adjuvant has an excellent risk/benefit profile with minimal side effects. Inadvertent systemic LA intoxication is a rare but potentially fatal complication of regional anesthesia and measures for prevention and early detection are essential. Should circulatory arrest occur, immediate resuscitation following standard guidelines is to be initiated including the use of epinephrine as the first line drug. Intravenous administration of lipid solutions may be beneficial as a secondary adjunct to stabilize hemodynamics but is not an alternative to epinephrine.

Toxicity of local anesthetic drugs: a pediatric perspective

The main mechanism of action of local anesthetics (LA) is to block sodium channels, thereby interrupting the propagation of nerve impulses. However, this action not only is localized to the sodium channels of nerve tissues involved with pain transmission but will have its effect on any tissue containing sodium channels. Thus, if there is a rapid absorption into the systemic circulation of locally injected LA or if LA inadvertently is injected into a blood vessel, then significant blockade of sodium channels in other tissues may also be blocked and serious complications may ensue. The two most important tissues associated with systemic toxicity of LA are the central nervous and the cardiovascular systems, which may lead to seizures, tachyarrhythmias, and ultimately death from apnea and cardiovascular collapse. The aim of this communication is to elucidate some issues that are associated with toxicity of LA and its treatment in the pediatric population.

Local anesthetic toxicity and lipid resuscitation in pregnancy

PURPOSE OF REVIEW

Lipid emulsion has emerged as an effective treatment of local anesthetic-induced cardiac arrest, but its therapeutic application for the obstetric patient requires definition at present. This review discusses clinical reports, relevant laboratory studies, and future directions for the development of an optimal protocol for lipid resuscitation in pregnancy.

RECENT FINDINGS

Several mechanisms have been postulated to account for the apparent enhanced sensitivity to local anesthetic systemic toxicity during pregnancy. One case report of lipid resuscitation in the pregnant patient demonstrates favorable outcomes and supports the safety of lipid therapy. Current guidelines and case reports propose that a large bolus of lipid at the earliest signs of toxicity may prevent cardiovascular collapse.

SUMMARY

As the obstetric demographic becomes older and more obese, new technologies and strategies can assist in controlling maternal death and major morbidity secondary to anesthesia complications. Lipid resuscitation appears to be an effective treatment for toxicity induced by lipophilic medications and may be useful in treating systemic toxicity in the pregnant patient. Obstetric care providers should be aware of lipid resuscitation and consider its use as described by American Society of Regional Anesthesia and Pain Medicine guidelines.

The acute toxicity of local anesthetics

IMPORTANCE OF THE FIELD

Systemic toxicity, usually from overdose or intravascular dose, is feared because it mainly affects the heart and brain, and may be acutely life-threatening.

AREAS COVERED IN THIS REVIEW

Pharmacological studies of local anesthetic toxicity have largely been reviewed primarily relating to the evaluation of ropivacaine and levobupivacaine during the past decade. This review/opinion focuses more on the principles and concepts underlying the main models used, from chemical pharmacological and pharmacokinetic perspectives.

WHAT THE READER WILL GAIN

Research models required to produce pivotal toxicity data are discussed. The potencies for neural blockade and systemic toxicity are associated across virtually all models, with some deviations through molecular stereochemistry. These models show that all local anesthetics can produce direct cardiovascular system toxicity and CNS excitotoxicity that may further affect the cardiovascular system response. Whereas the longer-acting local anesthetics are more likely to cause cardiac death by malignant arrhythmias, the shorter-acting agents are more likely to cause cardiac contraction failure. In most models, equi-anesthetic doses of ropivacaine and levobupivacaine are less likely to produce serious toxicity than bupivacaine.

TAKE HOME MESSAGE

Of the various models, this reviewer favors a whole-body large animal preparation because of the comprehensive data collection possible. The conscious sheep preparation has contributed more than any other, and may be regarded as the de facto 'standard' experimental model for concurrent study of local anesthetic toxicity ± pharmacokinetics, using experimental designs that can reproduce the toxicity seen in clinical accidents.

Progress in analgesia for labor: focus on neuraxial blocks

Neuraxial analgesia is widely accepted as the most effective and the least depressant method of providing pain relief in labor. Over the last several decades neuraxial labor analgesia techniques and medications have progressed to the point now where they provide high quality pain relief with minimal side effects to both the mother and the fetus while maximizing the maternal autonomy possible for the parturient receiving neuraxial analgesia. The introduction of the combined spinal epidural technique for labor has allowed for the rapid onset of analgesia with minimal motor blockade, therefore allowing the comfortable parturient to ambulate. Patient-controlled epidural analgesia techniques have evolved to allow for more flexible analgesia that is tailored to the individual needs of the parturient and effective throughout the different phases of labor. Computer integrated systems have been studied to provide seamless analgesia from induction of neuraxial block to delivery. New adjuvant drugs that improve the effectiveness of neuraxial labor analgesia while decreasing the side effects that may occur due to high dose of a single drug are likely to be added to future labor analgesia practice. Bupivacaine still remains a popular choice of local anesthetic for labor analgesia. New local anesthetics with less cardiotoxicity have been introduced, but their cost effectiveness in the current labor analgesia practice has been questioned.