Antiarrhythmic Mechanisms of Epidural Blockade After Myocardial Infarction.

BACKGROUND: Thoracic epidural anesthesia (TEA) has been shown to reduce the burden of ventricular tachycardia in small case series of patients with refractory ventricular tachyarrhythmias and cardiomyopathy. However, its electrophysiological and autonomic effects in diseased hearts remain unclear, and its use after myocardial infarction is limited by concerns for potential right ventricular dysfunction. METHODS: Myocardial infarction was created in Yorkshire pigs (N=22) by left anterior descending coronary artery occlusion. Approximately, six weeks after myocardial infarction, an epidural catheter was placed at the C7-T1 vertebral level for injection of 2% lidocaine. Right and left ventricular hemodynamics were recorded using Millar pressure-conductance catheters, and ventricular activation recovery intervals (ARIs), a surrogate of action potential durations, by a 56-electrode sock and 64-electrode basket catheter. Hemodynamics and ARIs, baroreflex sensitivity and intrinsic cardiac neural activity, and ventricular effective refractory periods and slope of restitution (Smax) were assessed before and after TEA. Ventricular tachyarrhythmia inducibility was assessed by programmed electrical stimulation. RESULTS: TEA reduced inducibility of ventricular tachyarrhythmias by 70%. TEA did not affect right ventricular-systolic pressure or contractility, although left ventricular-systolic pressure and contractility decreased modestly. Global and regional ventricular ARIs increased, including in scar and border zone regions post-TEA. TEA reduced ARI dispersion specifically in border zone regions. Ventricular effective refractory periods prolonged significantly at critical sites of arrhythmogenesis, and Smax was reduced. Interestingly, TEA significantly improved cardiac vagal function, as measured by both baroreflex sensitivity and intrinsic cardiac neural activity. CONCLUSIONS: TEA does not compromise right ventricular function in infarcted hearts. Its antiarrhythmic mechanisms are mediated by increases in ventricular effective refractory period and ARIs, decreases in Smax, and reductions in border zone electrophysiological heterogeneities. TEA improves parasympathetic function, which may independently underlie some of its observed antiarrhythmic mechanisms. This study provides novel insights into the antiarrhythmic mechanisms of TEA while highlighting its applicability to the clinical setting.

Evaluation of a modified ultrasound-assisted technique for mid-thoracic epidural placement: a prospective observational study.

BACKGROUND: Although mid-thoracic epidural analgesia benefits patients undergoing major surgery, technical difficulties often discourage its use. Improvements in technology are warranted to improve the success rate on first pass and patient comfort. The previously reported ultrasound-assisted technique using a generic needle insertion site failed to demonstrate superiority over conventional landmark techniques. A stratified needle insertion site based on sonoanatomic features may improve the technique. METHODS: Patients who presented for elective abdominal or thoracic surgery requesting thoracic epidural analgesia for postoperative pain control were included in this observational study. A modified ultrasound-assisted technique using a stratified needle insertion site based on ultrasound images was adopted. The number of needle passes, needle skin punctures, procedure time, overall success rate, and incidence of procedure complications were recorded. RESULTS: One hundred and twenty-eight subjects were included. The first-pass success and overall success rates were 75% (96/128) and 98% (126/128), respectively. In 95% (122/128) of patients, only one needle skin puncture was needed to access the epidural space. The median [IQR] time needed from needle insertion to access the epidural space was 59 [47-122] seconds. No complications were observed during the procedure. CONCLUSIONS: This modified ultrasound-assisted mid-thoracic epidural technique has the potential to improve success rates and reduce the needling time. The data shown in our study may be a feasible basis for a prospective study comparing our ultrasound-assisted epidural placements to conventional landmark-based techniques.

A prospective observational study on the feasibility of subumbilical laparoscopic procedures under epidural anesthesia in sedated spontaneously breathing infants with a natural airway.

BACKGROUND: Laparoscopic procedures are usually performed under general anesthesia with a secured airway including endotracheal intubation or supraglottic airways. AIMS: This is a prospective study of the feasibility of subumbilical laparoscopic procedures under epidural anesthesia in sedated, spontaneous breathing infants with a natural airway. METHODS: We consecutively enrolled 20 children <3 years old with nonpalpable testes scheduled for diagnostic laparoscopy with or without an ensuing orchidopexy, inguinal revision, or Fowler-Stephens maneuver. Inhalational induction for venous access was followed by sedation with propofol and ultrasound-guided single-shot epidural anesthesia via the caudal or thoracolumbar approach using 1.0 or 0.5 ml kg-1 ropivacaine 0.38%, respectively. The primary outcome measure was block success, defined as no increase in heart rate by >15% or other indicators of pain upon skin incision. RESULTS: Of the 20 children (median age: 10 months; IQR: 8.3-12), 17 (85%) were anesthetized through a caudal and 3 (15%) through a direct thoracolumbar epidural, 18 (90%) underwent a surgical procedure and 2 (10%) diagnostic laparoscopy only. Five patients (25%) received block augmentation using an intravenous bolus of fentanyl (median dose: 0.9 µg kg-1 ; IQR: 0.8-0.95) after the initial prick test and before skin incision. There was no additional need for systemic pain therapy in the operating theater or recovery room. No events of respiratory failure or aspiration were observed. CONCLUSIONS: In experienced hands, given our success rate of 100%, epidural anesthesia performed in sedated spontaneously breathing infants with a natural airway can be an alternative strategy for subumbilical laparoscopic procedures.

Epidural versus general anesthesia for open pyloromyotomy in infants: A retrospective observational study.

BACKGROUND: Thoracic epidural anesthesia for open infantile hypertrophic pyloric stenosis surgery is a controversial issue in the presence of little comparative data. AIMS: To compare this approach to general anesthesia for desaturation events (≤90% oxygen saturation) and absolute values of minimal oxygen saturation, minimal heart frequency, operating-room occupancy time, and durations of surgery in a retrospective study design. METHODS: Data were retrieved for patients with infantile hypertrophic pyloric stenosis managed by thoracic epidurals under sedation or general anesthesia with rapid sequence induction between 01/2007 and 12/2017. Oxygen saturation and heart rate were analyzed over eight 5-minutes intervals relative to the start of anesthesia / sedation (four-time intervals) and before discharge of the patient from the operating room (four-time intervals). Fisher's exact tests and mixed model two-way analysis of variance for repeated measures were employed for intergroup comparisons. RESULTS: The epidural and general anesthesia groups included 69 and 32 evaluable infants, respectively. Patients managed under epidural anesthesia had cumulatively higher minimimal mean (SD) oxygen saturation values (98.2 [2.6] % versus 96.6 [5.2] %, p < 0.001) and lower minimal mean (SD) heart rate values (127.9 [15.0] beats per minute versus 140.7 [17.2] beats per minute, p < 0.001) over time. Similarly, the frequency of desaturation events (defined as ≤90% oxygen saturation) was significantly lower for these patients during the period of 5 minutes after induction of sedation or general anesthesia (odds ratio 7.4 [2.1-25.9]; p = 0.001) and during the subsequent period of five minutes (odds ratio 6.2 [1.1-33.9]; p = 0.031). One case of prolonged respiratory weaning was observed in the general anesthesia group. The mean (SD) operating-room occupancy was 61.9 (16.6) minutes for the epidural anesthesia group versus 73.3 (22.2) minutes for the general anesthesia group (p = 0.005) as a result of shorter emergence from sedation. CONCLUSIONS: In our series, maintaining spontaneous breathing with minimal airway manipulation in patients undergoing open repair of hypertrophic pyloric stenosis under single-shot epidural anesthesia resulted in fewer desaturation events ≤90% than general anesthesia. In addition, this approach seems to result in shorter turnover times in the operating room.

Thoracic Epidural Anesthesia Reduces Right Ventricular Systolic Function With Maintained Ventricular-Pulmonary Coupling.

BACKGROUND: Blockade of cardiac sympathetic fibers by thoracic epidural anesthesia may affect right ventricular function and interfere with the coupling between right ventricular function and right ventricular afterload. Our main objectives were to study the effects of thoracic epidural anesthesia on right ventricular function and ventricular-pulmonary coupling. METHODS: In 10 patients scheduled for lung resection, right ventricular function and its response to increased afterload, induced by temporary, unilateral clamping of the pulmonary artery, was tested before and after induction of thoracic epidural anesthesia using combined pressure-conductance catheters. RESULTS: Thoracic epidural anesthesia resulted in a significant decrease in right ventricular contractility (ΔESV25: +25.5 mL, P=0.0003; ΔEes: -0.025 mm Hg/mL, P=0.04). Stroke work, dP/dtMAX, and ejection fraction showed a similar decrease in systolic function (all P<0.05). A concomitant decrease in effective arterial elastance (ΔEa: -0.094 mm Hg/mL, P=0.004) yielded unchanged ventricular-pulmonary coupling. Cardiac output, systemic vascular resistance, and mean arterial blood pressure were unchanged. Clamping of the pulmonary artery significantly increased afterload (ΔEa: +0.226 mm Hg/mL, P<0.001). In response, right ventricular contractility increased (ΔESV25: -26.6 mL, P=0.0002; ΔEes: +0.034 mm Hg/mL, P=0.008), but ventricular-pulmonary coupling decreased (Δ(Ees/Ea) = -0.153, P<0.0001). None of the measured indices showed significant interactive effects, indicating that the effects of increased afterload were the same before and after thoracic epidural anesthesia. CONCLUSIONS: Thoracic epidural anesthesia impairs right ventricular contractility but does not inhibit the native positive inotropic response of the right ventricle to increased afterload. Right ventricular-pulmonary arterial coupling was decreased with increased afterload but not affected by the induction of thoracic epidural anesthesia. CLINICAL TRIAL REGISTRATION: URL: http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=2844. Unique identifier: NTR2844.

Chloroprocaine for epidural anesthesia in infants and children.

Continuous epidural infusions are an effective and safe method of providing anesthesia and postoperative analgesia in infants and children with multiple advantages over systemic medications, including earlier tracheal extubation, decreased perioperative stress response, earlier return of bowel function, and decreased exposure to volatile anesthetic agents with uncertain long-term neurocognitive effects. Despite these benefits, local anesthetic toxicity remains a concern in neonates and infants because of their decreased metabolic capacity for amide local anesthetics. Chloroprocaine, an ester local anesthetic agent, which is rapidly metabolized in plasma at all ages, is an attractive alternative for this special population, particularly in the presence of superimposed liver impairment or when higher infusion rates are needed for surgical incisions stretching many dermatomes. The current manuscript reviews the literature pertaining to the use of 2-chloroprocaine for regional anesthesia in infants and children. Dosing regimens are presented and the applications of 2-chloroprocaine in this population are discussed.

Epidural distribution of dye administered via an epidural catheter in a porcine model.

BACKGROUND: Local anaesthetics are commonly delivered to the epidural space by either intermittent bolus or continuous infusion. While these methods have been investigated in terms of analgesia and total dose administered, they have not been compared in terms of their effect on the spread of injectate within the epidural space. This animal study compared the spread of dye delivered to the epidural space in a porcine model by either bolus or infusion. METHODS: After ethical approval, epidural catheters were placed at three vertebral levels in seven anaesthetized pigs. Aqueous dye (1 ml) was injected into the catheter as a bolus, or as an infusion over 30 min. Animals were euthanized at the end of the study and necropsy performed immediately to quantify the extent of dye spread. RESULTS: In seven animals, 20 catheters were successfully placed in the epidural space. The mean (sd) extent of dye spread was 8.9 (2.6) cm in the infusion group compared with 15.2 (2.7) cm in the bolus group (P<0.001). Segmental spread was significantly greater in the bolus group compared with the infusion group (P<0.01). CONCLUSION: In the porcine epidural model, spread of one ml of epidural dye solution is more extensive after a single bolus compared with short term infusion.

Epidural pressure changes following caudal blockade: a prospective, observational study.

PURPOSE: Recent case reports raise the question as to whether anesthetic agents injected into the epidural space could lead to a 'compartment syndrome' and neurovascular sequelae. Single-shot caudal epidural anesthesia has been established as a safe technique, but changes in pressure in the caudal epidural space have not been described. Our aim was to study pressure changes to provide preliminary information for future studies design. METHODS: We prospectively measured the pressure changes in the caudal epidural space in 31 pediatric patients. The pressures were measured at loss of resistance, immediately after the bolus dose of local anesthetic (1 ml/kg), and at 15-s intervals up to 3 min. RESULTS: The pressure at loss of resistance was 35.6 ± 27.8 mmHg. A pulsatile waveform was observed once the epidural space was accessed. The pressure after administration of the local anesthetic bolus (1 ml/kg 0.2 % ropivacaine/bupivacaine with 1:200,000 epinephrine) was 192.5 ± 93.3 mmHg. The pressure decreased to 51.5 ± 39.0 mmHg at 15 s, 26.9 ± 9.9 mmHg after 2 min, and 24.7 ± 11.7 after 3 min. The return to baseline occurred at approximately 45-60 s. CONCLUSIONS: Following the administration of the local anesthetic into the caudal epidural space, there was a marked, but transient, increase in the pressure within the epidural space. It appears unlikely that a slow epidural catheter infusion could lead to a sustained increase in epidural pressure.

Aspirin and spinal haematoma after neuraxial anaesthesia: Myth or reality?

The safety of aspirin therapy in neuraxial anaesthesia has been historically questioned, and the current recommendations are still heterogeneous. A comprehensive review of clinical evidence and a comparative analysis of European and American guidelines were performed. Low-dose aspirin produces a selective, complete and irreversible cyclooxygenase-1 blockade, and higher doses do not increase the antiplatelet effect. Additional cyclooxygenase-2 blockade by high-dose aspirin might decrease the antithrombotic efficacy by inhibiting endothelial prostacyclin synthesis. Different doses of aspirin have been shown to be safe in a broad population subjected to neuraxial anaesthesia or analgesia. In the few case reports of spinal haematoma involving aspirin therapy, additional complicating factors were present. Considering the available evidence, the majority of national scientific societies agree that the isolated use of aspirin does not increase the risk of spinal haematoma and does not represent a contraindication to neuraxial blocks. The precautions regarding higher doses do not seem to be justified. Although aspirin alone is considered to be safe in neuraxial anaesthesia, the concurrent administration of other antithrombotic drugs significantly increases the risk of spinal haematoma and the recommended safety times for each of these other drugs must be strictly followed. An individualized assessment of the risks and benefits should be performed, before performing a neuraxial technique or catheter removal in a patient receiving aspirin.

Awake caudals and epidurals should be used more frequently in neonates and infants.

The current literature provides fundamental insights regarding the neurotoxic potency of various general anesthetic drugs in neonates and small infants. Therefore, considerations to minimize the use of general anesthetic drugs in this age group are required. The use of caudal and epidural anesthesia under sedation is one possibility to minimize the use of general anesthetic drugs. A large number of surgical procedures can be managed with this anesthetic concept. Training, practical hand skills, good infrastructure, a well-defined indication, and a team approach including the entire operation room staff are the major prerequisites to implement these techniques in the daily clinical practice. This review article discusses all present aspects and possible future evolutions of caudal and epidural anesthesia under sedation.