Relationship between labour analgesia modalities and types of anaesthetic techniques in categories 2 and 3 intrapartum caesarean deliveries.

General anesthesia (GA) is typically recommended for category 1 emergency cesarean delivery (CD). For categories 2­4 emergencies, either regional or GA can be used. The factors influencing the choice of anesthetic technique in these categories remain poorly understood. We analyzed the association between the type of labor analgesia and subsequent anesthetic techniques employed for intrapartum categories 2 and 3 CD. In a prospective longitudinal cohort study, 300 women were consequently enrolled and categorized according to Lucas's classification of CD urgency. The techniques of anesthesia (GA, spinal, and epidural anesthesia [EA]) employed for CD were analyzed with respect to labor analgesia methods (remifentanil patient-controlled analgesia [remifentanil-PCA], EA, and nitrous oxide [N2O]). EA was the most frequent analgesic option (43.8%), followed by remifentanil-PCA (20.7%) and N2O (5.1%), while 30.4% of parturient women received no analgesia. All anesthetic methods showed a significant relationship with analgesic modalities (P < 0.001). Remifentanil-PCA was associated with a higher incidence of GA. Contraindication to EA was the primary factor related to the transition from remifentanil-PCA to GA. Most parturients who received EA were successfully converted to EA. Spinal anesthesia was the most common technique in women using N2O and those without labor analgesia. GA was associated with lower 5-min Apgar scores. The method of labor analgesia was associated with the anesthesia technique employed for categories 2 and 3 CD. This finding may guide patient counseling and intrapartum anesthetic planning. However, the analysis should be cautiously interpreted as the selection of anesthesia is a complex decision influenced by several clinical considerations.

Intrapartum Cesarean Section and Perinatal Outcomes after Epidural Analgesia or Remifentanil-PCA in Breech and Twin Deliveries.

Comparative data on the potential impact of various forms of labor analgesia on the mode of delivery and neonatal complications in vaginal deliveries of singleton breech and twin fetuses are lacking. The present study aimed to determine the associations between type of labor analgesia (epidural analgesia (EA) vs. remifentanil patient-controlled analgesia (PCA)) and intrapartum cesarean sections (CS), and maternal and neonatal adverse outcomes in breech and twin vaginal births. A retrospective analysis of planned vaginal breech and twin deliveries at the Department of Perinatology, University Medical Centre Ljubljana, was performed for the period 2013-2021, using data obtained from the Slovenian National Perinatal Information System. The pre-specified outcomes studied were the rates of CS in labor, postpartum hemorrhage, obstetric anal sphincter injury (OASI), an Apgar score of <7 at 5 min after birth, birth asphyxia, and neonatal intensive care admission. A total of 371 deliveries were analyzed, including 127 term breech and 244 twin births. There were no statistically significant nor clinically relevant differences between the EA and remifentanil-PCA groups in any of the outcomes studied. Our findings suggest that both EA and remifentanil-PCA are safe and comparable in terms of labor outcomes in singleton breech and twin deliveries.

Videolaryngoscopy as a primary intubation modality in obstetrics: A narrative review of current evidence.

Pregnancy-related physiologic and anatomic changes affect oxygenation and airway management, and it is widely believed that airway difficulty may be more common in obstetric patients as a result. In addition, most obstetric intubations are performed under emergency conditions, and preoperative airway assessment poorly predicts airway management outcomes. These considerations necessitate special protocols for airway care in the obstetric population, and the evolution of the videolaryngoscope represents one of the most important milestones in recent decades. However, recommendations for the use of videolaryngoscopy in obstetrics remain unclear. A considerable body of evidence affirms that videolaryngoscopy improves laryngeal visualisation, increases first-attempt and overall intubation success rates, shortens intubation time, and facilitates team communication and education. In contrast, a significant number of studies have also reported conflicting results regarding comparative clinical outcomes and have highlighted other limitations regarding the adoption of videolaryngoscopy in routine obstetric care. Nevertheless, considering the peculiarities of obstetric intubation, the Macintosh-style videolaryngoscope can be suggested as the primary intubation device as it offers the benefits of both videolaryngoscopy and direct laryngoscopy. However, more rigorous evidence is needed to clarify the current blind spots and controversies regarding the role of videolaryngoscopy in obstetrics.

The Influence of Diabetic Peripheral Neuropathy on the Duration of Sciatic Nerve Block with 1.3% Liposomal Bupivacaine and 0.25% Bupivacaine Hydrochloride in a Mouse Model.

Little is known regarding the pharmacological properties of extended-release local anesthetics in the setting of diabetic peripheral neuropathy. We investigated and compared the duration of sciatic nerve block following administration of clinically relevant concentrations of liposomal bupivacaine (LB) and bupivacaine hydrochloride (BH) in diabetic mice with peripheral neuropathy. In this prospective, randomized, and double-blind study, twenty-four female C57BL/6J-OlaHsd mice were assigned to a streptozotocin-induced type 1 diabetes group and a control group without diabetes. The presence of peripheral neuropathy was established by assessing the duration of thermal latency of the plantar and tail-flick tests, following which both groups were subdivided into two subgroups in which 35 mg/kg of 1.31% LB and 7 mg/kg of 0.25% BH were respectively administered for sciatic nerve block. The average sensory block duration with BH was 106 min and 117.1 min in the control and diabetic groups, respectively. With LB, the average sensory block duration was 118 min in the control mice, while in mice with diabetic peripheral neuropathy, the average block duration was significantly longer and above the 270 min limit set in our study. Accordingly, sensory block duration was longer with LB compared to BH, and diabetic peripheral neuropathy significantly increased sciatic nerve block duration with LB.

Delivery mode and neonatal morbidity after remifentanil-PCA or epidural analgesia using the Ten Groups Classification System: A 5-year single-centre analysis of more than 10 000 deliveries.

OBJECTIVE: This study aimed to explore the potential association between remifentanil patient-controlled analgesia (RPCA) or epidural analgesia (EA), and caesarean section (CS) rate, operative vaginal delivery rate (OVD), operative delivery (OD) rate (CS or OVD) with pathological cardiotocography (CTG) tracing, Apgar score < 7 at 5 min after birth, incidence of perinatal asphyxia and neonatal intensive care unit (NICU) admission within four groups of the Ten Groups Classification System (TGCS) labour types; group 1: nulliparous, singleton cephalic, ≥37 weeks, spontaneous onset of labour; group 2a: nulliparous, singleton cephalic, ≥37 weeks, induction of labour; group 3: multiparous, singleton cephalic, ≥37 weeks, spontaneous onset of labour; group 4a: multipara, singleton cephalic, ≥37 weeks, induction of labour). We hypothesized that labour and delivery outcomes between RPCA and EA would differ within the different TGCS labour types. STUDY DESIGN: 10,561 deliveries (4876 with RPCA, 5685 with EA) at the University Clinical Centre Ljubljana, Slovenia, from 2015 through 2019 were analysed using the Slovenian National Perinatal Information System data. RESULTS: Compared to EA, RPCA was associated with lower CS and OVD rates in nulliparous women with spontaneous onset of labour (group 1) (CS: 9.9 % vs14.3 %; P < 0.001) (OVD: 5.1 % vs 8.4 %; P < 0.001), in nulliparous women with induced labour (group 2a) (CS: 14.8 % vs 24.2 %; P < 0.001) (OVD: 6.5 % vs 8.9 %; P = 0.036) and in multiparous women with spontaneous onset of labour (group 3) (CS: 1.1 % vs 2.4 %; P = 0.021) (OVD: 0.1 % vs 0.8 %; P = 0.007), respectively. RPCA was associated with a lower incidence of OD with pathologic CTG in all four studied groups (groups 1, 2a, 3, 4a). No differences in APGAR < 7 at 5 min, neonatal asphyxia, and NICU admission were recorded between the two analgesic techniques within any of the TGCS groups. CONCLUSION: Compared to EA, RPCA was not associated with worse delivery and neonatal outcomes within any of the four studied TGCS groups. RPCA could be used for labour analgesia routinely if strict adherence to protocols is ensured and regular staff training is provided.

Transurethral catheterization of female domestic pigs with a Foley catheter.

This report describes transurethral catheterization with a Foley catheter in 19 anaesthetized, laterally recumbent female pigs with a chest circumference of 72.1 ± 4.2 cm and weighing approximately 40 kg. Catheterization within five minutes was successful in 78.9% of the pigs. Catheterization depth, measured as the distance between the bladder neck and the mucocutaneous junction of the vulva, was 14.5 ± 1.3 cm and correlated with chest circumference but not body length. Measurement of catheterization depth aids in optimal positioning and may prevent inflation of the Foley catheter in the urethra.

Determination of bupivacaine tissue concentration in human biopsy samples using high-performance liquid chromatography with mass spectrometry.

In the present study, we developed a simple and rapid analytical method for the quantification of bupivacaine hydrochloride in human biopsy samples of adipose, muscle, neural, connective and cartilage tissue using liquid chromatography-mass spectrometry. Anesthetics were extracted from the tissue samples using 0.1% formic acid in acetonitrile for protein denaturation and hexane for removal of lipophilic impurities. Analytes were separated adequately on Phenomenex Luna Omega polar C18 column using a gradient mobile phase 0.1% formic acid in water and 0.1% formic acid in acetonitrile. The lower limits of quantification were ≤ 97 ng g-1 tissue for all studied tissues. Intra-day recoveries were between 48.2% and 82.1% with relative standard deviations (RSDs) between 1.47% and 14.28%, whereas inter-day recoveries were between 52.2% and 77.6% with RSDs between 2.98% and 14.79%. The calibration curve showed a linear fit with R2 higher than 0.99 in the concentration range from 0.16 to 100 µg g-1 . Lidocaine hydrochloride was tested as internal standard because its recoveries and matrix effects were comparable to bupivacaine hydrochloride. Post-analytical corrections of measured bupivacaine tissue concentrations can accordingly be made based on recovery of lidocaine as internal standard, with recoveries between 51.2% and 86.9% and RSDs between 1.99% and 16.88%. The developed method could be used to study time-dependent spread of bupivacaine locally or to more distant locations across tissue barriers.

Posteromedial quadratus lumborum block versus wound infiltration after caesarean section: A randomised, double-blind, controlled study.

BACKGROUND: Reducing pain and minimising the use of opioids after caesarean section are crucial to enhancing maternal recovery and promoting mother-newborn interaction. Various techniques have been implemented to improve analgesia. We compared the analgesic efficacy of posteromedial quadratus lumborum block with that of wound infiltration following elective caesarean section. OBJECTIVE: We hypothesised that within a multimodal analgesia approach, posteromedial quadratus lumborum block would, due to its potential to relieve visceral pain, result in a 15% reduction in 24-h postoperative opioid consumption compared with wound infiltration. DESIGN: A double-blind, randomised, placebo-controlled clinical study. SETTING: A single-centre study between August 2019 and May 2020. PATIENTS: One hundred and sixteen women were randomly allocated into two groups. In the quadratus lumborum group, 20 ml 0.9% saline was injected into the surgical wound followed by bilateral posteromedial quadratus lumborum block using 20 ml 0.25% levobupivacaine per side. In the wound infiltration group, 20 ml of 0.25% levobupivacaine was injected into the surgical wound followed by a bilateral posteromedial quadratus lumborum injection with 20 ml 0.9% saline per side. MAIN OUTCOME MEASURES: The primary outcome was opioid (piritramide) consumption at 24 h. Secondary outcomes were piritramide consumption at 48 h, time-to-first analgesic request, pain scores at rest and with movement, surgery-to-first-ambulation time, surgery-to-breastfeeding time, sedation, pruritus and complications. RESULTS: Piritramide consumption in 24 h was significantly lower with posteromedial quadratus lumborum block (1.5 ±â€Š1.8 mg) than with wound infiltration (2.2 ±â€Š1.7 mg) (P = 0.04), mean difference of -0.7 mg, (95% CI -1.3 to -0.03). In those who required piritramide, time-to-first analgesic request was significantly longer with posteromedial quadratus lumborum block 11 [7 to 14] h, than with wound infiltration 7 [5 to 11] h (P = 0.02). Pain scores were low, with no differences recorded at rest and with movement. There were no differences in time-to-ambulation and time-to-breastfeed between the groups. CONCLUSION: As a component of multimodal post-caesarean section analgesia, posteromedial quadratus lumborum block was associated with lower 24-h opioid consumption compared with wound infiltration. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT04000308.

Analgesic efficacy of remifentanil patient-controlled analgesia versus combined spinal-epidural technique in multiparous women during labour.

OBJECTIVES: To compare the analgesic profile of remifentanil patient-controlled analgesia (RPCA) and combined spinal-epidural analgesia technique (CSEA) in multiparous women during the entire labour. We hypothesized that CSEA would provide a better and more sustained pain reduction than RPCA. MATERIAL AND METHODS: A prospective observational trial under ID NCT02963337 at a university hospital in Slovenia 2017-2018. Analgesic efficacy, satisfaction with pain-relief, adverse effects, labour progress, and outcomes between RPCA (80) and CSEA (81) were compared. RESULTS: CSEA provided significantly lower pain scores during the entire labour. Compared to baseline, significant pain reduction was recorded in both groups after 15 min. No difference was recorded compared to baseline with RPCA and CSEA after 45 and 90 mins, respectively. CSEA provided higher satisfaction than RPCA (5 [5-5] vs 5 [4-5], p < 0.0001). More patients with CSEA opted for the same technique for the next labour [CSEA; 77 (95%) vs RPCA; 65 (81%), p = 0.003]. No crossovers were observed. RPCA was associated with desaturation (34%), bradypnea (21%) and apnoea (25%), which were transitional and easily managed. None had severe sedation. No differences were recorded in labour progress and outcomes. Apgar scores were reassuring in all neonates (> 8). None had umbilical artery pH < 7.0. CONCLUSIONS: In multiparas, CSEA provided superior analgesia and satisfaction than RPCA. Nevertheless, RPCA provided a satisfactory experience, suggesting it could be used when neuraxial analgesia is not available, preferred, or contraindicated. In that case, constant presence of midwife is mandatory for management of clinically significant hypoventilation.

The effect of vitamin C on pulmonary oedema in patients with severe preeclampsia: A single-centre, randomised, placebo-controlled, double-blind trial.

OBJECTIVE: To determine whether vitamin C in the first three days postpartum reduces pulmonary oedema (PE) assessed by lung ultrasound in patients with severe preeclampsia. DESIGN: Randomised, placebo-controlled, double-blind trial. SETTING: Tertiary perinatal centre. POPULATION: Consecutively admitted patients with singleton pregnancies complicated by severe preeclampsia. METHODS: Thirty-four patients received vitamin C (1.5 g/6 h) (n = 17) or placebo (n = 17) at days 1, 2, and 3 postdelivery. Mann-Whitney-U test was used to compare vitamin C vs placebo groups. A p ≤ 0.05 was considered statistically significant. MAIN OUTCOME MEASURES: Lung ultrasound was performed once daily in the first three days following delivery. Echo Comet Score (ECS) on day 1 postdelivery was the primary outcome studied and was obtained using the 28-rib interspaces technique. ECS on days 2 and 3 postdelivery were secondary outcomes. RESULTS: There was no significant difference in ECS on day 1 (median 23 (inter-quartile range (IQR) 21-61) vs 18 (IQR 8-35); p = 0.31). All ultrasound examinations on day 1 were performed within six hours from delivery. On days 2 and 3, ECS was significantly lower in vitamin C group compared to placebo (8 (IQR 3-14) vs 35 (IQR 15-78); p = 0.03 and 5 (IQR 3-10) vs 18 (IQR 18-44); p = 0.04, respectively). CONCLUSION: A single dose of intravenous vitamin C did not reduce PE in postpartum patients with severe preeclampsia on day 1 after delivery. Repeated doses, however, seem to have a delayed effect with a reduction in PE detected on ultrasound on days 2 and 3 following delivery. TRIAL REGISTRATION: This trial is registered at ClinicalTrials.gov: ID NCT03451266 (https://clinicaltrials.gov/ct2/show/NCT03451266?term=NCT03451266&draw=2&rank=1).

Clinical and histologic tissue responses of skin incisions closed with glycomer 631 and lactomer 9-1 using a subcuticular technique in pigs.

BACKGROUND: Glycomer 631 and lactomer 9-1 are absorbable suture materials indicated for soft tissue approximation in non-infected wounds. Pigs are often used as surgical models in translational research; however, reports of tissue reactions to both suture materials in pigs are limited. The aim of this study was to assess clinical and histologic responses of skin incisions closed with a subcuticular technique using glycomer 631 and lactomer 9-1 in pigs. RESULTS: Skin incisions on 17 pigs were closed with glycomer 631 and lactomer 9-1, and a clinical reactive score (CRS) including erythema, swelling, discharge and dehiscence was calculated on postoperative days 7 and 14. Subcuticular tissue reaction was assessed histologically on postoperative day 14 (the presence of extravascular neutrophils, macrophages, multinucleated giant cells, lymphocytes, fibroblasts, bacterial colonies and the overall severity of the inflammatory response to the suture material), and the cumulative score of the variables was calculated as an aggregate tissue irritation score (ATIS). Tissue samples were examined for suture extrusion and evaluated microbiologically. The clinical reactive score did not differ between the suture materials. Only one ATIS variable, namely the overall severity of the inflammatory response, was lower (p = 0.029) when glycomer 631 was used. Suture extrusion was found in 10/17 of the incisions closed by glycomer 631 and in 7/13 of the incisions closed by lactomer 9-1. Trueperella pyogenes was isolated from the skin and from the area of tissue reaction in six pigs. CONCLUSIONS: No difference in CRS between the suture materials was observed, and thus both materials may be used for the subcuticular technique in pigs. Glycomer 631 induced less tissue reaction only in terms of the overall severity of the inflammatory response. Suture extrusion was observed in more than 50% of incisions regardless of the suture material, possibly due to a large amount of suture material in the wound. Trueperella pyogenes was the only pathogen isolated from the tissue surrounding the suture material.

3D analysis of capillary network in skeletal muscle of obese insulin-resistant mice.

In obesity, the skeletal muscle capillary network regresses and the insulin-mediated capillary recruitment is impaired. However, it has been shown that in the early stage of advanced obesity, an increased functional vascular response can partially compensate for other mechanisms of insulin resistance. The present study aimed to investigate the changes in the capillary network around individual muscle fibres during the early stage of obesity and insulin resistance in mice using 3D analysis. Capillaries and muscle fibres of the gluteus maximus muscles of seven high-fat-diet-induced obese and insulin-resistant mice and seven age-matched lean healthy mice were immunofluorescently labelled in thick transverse muscle sections. Stacks of images were acquired using confocal microscope. Capillary network characteristics were estimated by methods of quantitative image analysis. Muscle fibre typing was performed by histochemical analysis of myosin heavy chain isoforms on thin serial sections of skeletal muscle. Capillary length per muscle fibre length and capillary length per muscle fibre surface were increased by 27% and 23%, respectively, around small muscle fibres in obese mice, while there were no significant comparative differences around large fibres of obese and lean mice. Furthermore, the capillarization was larger around small compared to large fibres and there was a shift toward fast type myosin heavy chain isoforms, with no significant changes in muscle fibre diameters, tortuosity and anisotropy in obese mice. Overall, the results show that obese insulin-resistant mice have selective increase in capillarization around small predominantly intermediate muscle fibres, which is most likely related to the impaired glucose metabolism characteristic of type 2 diabetes.

The ultrasound-guided retrolaminar block: volume-dependent injectate distribution.

PURPOSE: The ultrasound-guided retrolaminar block is one of the newer and simpler alternatives to the traditional, often technically challenging, paravertebral (PV) block. Its feasibility, safety, and efficacy have already been clinically demonstrated in patients with multiple rib fractures using higher volumes of local anesthetic, when compared with the traditional approach. The primary aim of this observational anatomical study was to assess the spread of local anesthetic from the retrolaminar injection point to the PV space and its volume dependence. Second, we assessed the incidence of epidural and contralateral PV spread in the both groups. METHODS: Ten fresh porcine cadavers were randomized into 2 groups (n=5 each) to receive ultrasound-guided retrolaminar injections at Th4-Th5 level with either 10 mL (low-volume group) or 30 mL (high-volume group) of 2% lidocaine and methylene blue mixture. After the procedure, the cadavers were dissected and frozen. Cross-section cuts (~1 cm thick) were performed to evaluate the injectate spread. RESULTS: In the high-volume group, injectate spread from the retrolaminar to the PV space was observed in all specimens (5 out of 5; 100%), while in the low-volume group, no apparent spread to the PV space was found (0 out of 5; 0%). No epidural or contralateral PV spread was observed in any of the specimens. CONCLUSION: Following ultrasound-guided retrolaminar injections in fresh porcine cadavers, injectate spread from the retrolaminar tissue plane to the PV space is strongly volume dependent, suggesting that, clinically, high local anesthetic volumes maybe critical for achieving regional anesthesia and analgesia consistent with traditional PV blockade.

3D reconstruction of peripheral nerves from optical projection tomography images: A method for studying fascicular interconnections and intraneural plexuses.

The general microscopic characteristics of nerves are described in several textbooks of histology, but the specific microanatomies of most nerves that can be blocked by anesthesiologists are usually less well known. Our objective was to evaluate the 3D reconstruction of nerve fascicles from optical projection tomography images (OPT) and the ability to undertake an internal navigation exploring the morphology in detail, more specifically the fascicular interconnections. Median and lingual nerve samples were obtained from five euthanized piglets. OPT images of the samples were acquired and 3D reconstruction was performed. The OPT technique revealed the inner structure of the nerves at high resolution, including large and small fascicles, perineurium, interfascicular tissue, and epineurium. The fascicles were loosely packed inside the median nerve and more densely so in the lingual nerve. Analysis of the 3D models demonstrated that the nerve fascicles can show six general spatial patterns. Fascicular interconnections were clearly identified. The 3D reconstruction of nerve fascicles from OPT images opens a new path for research into the microstructure of the inner contents of fascicular nerve groups and their spatial disposition within the nerve including their interconnections. These techniques enable 3D images of partial areas of nerves to be produced and could became an excellent tool for obtaining data concerning the 3D microanatomy of nerves, essential for better interpretation of ultrasound images in clinical practice and thus avoiding possible neurological complications. Clin. Anat. 31:424-431, 2018. © 2017 Wiley Periodicals, Inc.

Ultrasound-Guided Glossopharyngeal Nerve Block: A Cadaver and a Volunteer Sonoanatomy Study.

BACKGROUND AND OBJECTIVES: Glossopharyngeal nerve (GPN) blocks are usually performed by topical, intraoral, or peristyloid approaches, which carry significant complication risks due to the proximity of important neurovascular structures. This study presents a proof of concept for a new ultrasound (US)-guided technique, which would block the GPN distally, in the parapharyngeal space, away from the immediate vicinity of high-risk collateral structures. METHODS: Five cadaver heads were dissected, and the location of the GPN was explored bilaterally. In 40 healthy volunteers (20 men and 20 women; median age, 35.5 years [range, 24-69 years]) parapharyngeal sonograms were obtained, saved, and analyzed. To assess the technical feasibility of a distal GPN block in the parapharyngeal space, unilateral US-guided dye injections were performed in 3 fresh cadavers, followed by dissections. RESULTS: The GPN was consistently identified between the stylopharyngeal and middle pharyngeal constrictor muscles in all cadaver specimens. The median distance between the GPN and the ipsilateral greater horn of the hyoid bone was 2.4 cm (range, 2.3-2.7 cm) on the right and 2.6 cm (range, 2.3-2.9 cm) on the left. The mean skin-to pharyngeal wall distances in the volunteers were 2.03 (SD, 0.41) cm on the right and 2.02 (SD, 0.45) cm on the left. The mean hyoid bone-to-pharyngeal wall distances were 2.04 (SD, 0.35) cm (right) and 2.07 (SD, 0.35) cm (left). The fresh cadaver dissections demonstrated dye deposition adjacent to the GPN in the parapharyngeal space in all specimens. CONCLUSIONS: Based on our anatomical results in cadavers and healthy volunteers, we submit that successful and safe blockade of the distal GPN at the pharyngeal wall level is technically feasible under US guidance.

The thyrohyoid membrane as a target for ultrasonography-guided block of the internal branch of the superior laryngeal nerve.

STUDY OBJECTIVE: The objective was to present a proof of concept for a simple and consistently successful ultrasonograpy (US)-guided technique to block the internal branch of the superior laryngeal nerve (iSLN). DESIGN: This was a volunteer and cadaver anatomy study. SETTING: The setting was an anesthesiology department and an anatomy laboratory at a medical school MEASUREMENTS: H13-6 MHz US scans were performed in 40 healthy volunteers positioned supine and with extended necks. The goals were to identify the thyrohyoid membrane, measure its depth (in centimeters) using the shortest vertical distance from the skin, and record the scanning time (in seconds) needed to obtain the optimal image. Anatomical dissection was performed with an operating microscope bilaterally on 5 adult cadaver heads, fixed in formalin, to expose the point of iSLN penetration through the thyrohyoid membrane. The distance between the greater horn of the hyoid bone and the nerve entry point into the thyrohyoid membrane was measured. Ultrasonography-guided in-plane injections were performed unilaterally with 22-gauge 50-mm nerve block needles in 3 fresh cadavers with 2-mL lidocaine/methylene blue mixture deposited under direct vision just superficial to the thyrohyoid membrane to evaluate technical feasibility and injectate spread. MAIN RESULTS: Anatomically, the iSLN was identified in all formalin-preserved cadavers, with hyoid bone greater horn to nerve-membrane interface distances measuring 1.0-2.4 cm (mean, 2.0 cm; SD, 0.5). Sonographically, the iSLN was not visualized, whereas the hyoid bone and the thyrohyoid membrane were visualized in all volunteers. The mean distance from skin to thyrohyoid membrane was 1.69 cm (SD, 0.38). The mean time needed to scan was 15 seconds (SD, 2.3). After US-guided injection, the dye deposition was observed around the iSLN in all cadaver specimens. CONCLUSIONS: A simpler and consistently reproducible US-guided iSLN block is feasible using the thyrohyoid membrane as target plane for local anesthetic injection. Clinical trials are needed to determine its effectiveness and safety, needle entry point, trajectory, and local anesthetic volume.

A prospective, randomized, double-blinded comparison between multimodal thoracic paravertebral bupivacaine and levobupivacaine analgesia in patients undergoing lung surgery.

OBJECTIVES: To compare the effects of paravertebral analgesia with levobupivacaine or bupivacaine on intra- and postoperative pain for thoracic surgery. DESIGN: A prospective, randomized, and double-blinded study. SETTING: A university hospital. PARTICIPANTS: Forty patients undergoing thoracic surgery. INTERVENTIONS: Patients received paravertebral catheterization and a bolus (14-20 mL) of 0.5% bupivacaine (n = 20) or 0.5% levobupivacaine (n = 20) with morphine, 60 µg/kg, before the induction of general anesthesia that consisted of a propofol infusion. A paravertebral continuous infusion (0.05 mL/kg/h) of 0.25% bupivacaine or 0.25% levobupivacaine, 100 mL, with added morphine, 10 mg, and clonidine, 0.15 mg, was started at the end of surgery for 72 hours postoperatively. Postoperative rescue diclofenac analgesia was available if required. MEASUREMENTS AND MAIN RESULTS: The primary outcome was intraoperative fentanyl consumption. Static and dynamic pain scores measured by a visual analog scale were assessed regularly. Intraoperative fentanyl consumption was significantly lower in the levobupivacaine group compared with the bupivacaine group (p = 0.001). On all 3 postoperative days, static pain scores were significantly lower in the levobupivacaine group compared with the bupivacaine group (p < 0.05). Dynamic pain scores were significantly lower in the levobupivacaine group compared with the bupivacaine group during the 2 postoperative days (p < 0.05). A smaller proportion of patients in the levobupivacaine group used rescue analgesia (p < 0.005). CONCLUSIONS: Paravertebral analgesia with levobupivacaine resulted in less intraoperative fentanyl consumption, lower static (3 days) and dynamic (2 days) pain scores, and less rescue analgesia than analgesia with bupivacaine.

Electron-microscopic imaging of endothoracic fascia in the thoracic paravertebral space in rats.

BACKGROUND AND OBJECTIVES: Anesthesia and analgesia with paravertebral block are reportedly variable. Existence of an endothoracic fascia has been proposed as one of the possible mechanisms leading to variability. We undertook an electron-microscopy imaging study to investigate the endothoracic fascia in the thoracic paravertebral space (TPS) in rats. METHODS: Male Wistar rats were studied in accordance with the principles of laboratory animal care. After the rats were euthanized in a CO2 chamber, the thoracic paravertebral tissues were removed en bloc and cut into consecutive transverse sections of approximately 3 mm. Stereomicroscopy and electron-microscopy assessments were performed by 2 independent observers. RESULTS: The endothoracic fascia was consistently identified in all specimens. The fascia was located between the parietal pleura and the innermost intercostal muscles or ribs. Its thickness ranged from 15 to 27 µm (mean, 20 ± 3 µm). The endothoracic fascia divided the TPS in 2 compartments: one, extrapleural and anterolateral (EPC); another, subendothoracic and posteromedial (SETC). The spinal nerves with their ganglia were found within SETC, whereas the sympathetic ganglia were consistently located within the EPC. CONCLUSIONS: The endothoracic fascia in rats appears to divide the TPS into EPC and SETC. These anatomic characteristics may have implications in thoracic paravertebral blockade.