Rescue oxygenation success by cannula or scalpel-bougie emergency front-of-neck access in an anaesthetised porcine model.

In the obese, the evidence for the choice of the optimal emergency front-of-neck access technique is very limited and conflicting. We compared cannula and scalpel-bougie emergency front-of-neck access techniques in an anaesthetised porcine model with thick pretracheal tissue. Cannula and scalpel-bougie cricothyroidotomy techniques were performed in 11 and 12 anaesthetised pigs, respectively. Following successful tracheal access, oxygenation was commenced and continued for 5 min using Rapid-O2 device for cannula and circle breathing system for scalpel-bougie study groups. The primary outcome was a successful rescue oxygenation determined by maintenance of arterial oxygen saturation >90% 5 min after the beginning of oxygenation. Secondary outcomes included success rate of airway device placement, time to successful airway device placement, and trauma to the neck and airway. The success rate of rescue oxygenation was 18% after cannula, and 83% after scalpel-bougie technique (P = 0.003). The success rate of airway device placement was 73% with cannula and 92% with scalpel-bougie technique (P = 0.317). Median (inter-quartile-range) times to successful airway device placement were 108 (30-256) and 90 (63-188) seconds (P = 0.762) for cannula and scalpel-bougie emergency front-of-neck access, respectively. Proportion of animals with iatrogenic trauma additional to the procedure itself was 27% for cannula and 75% for scalpel-bougie technique (P = 0.039). Thus, in the porcine model of obesity, the scalpel-bougie technique was more successful in establishing and maintaining rescue oxygenation than cannula-based technique; however, it was associated with a higher risk of severe trauma.

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.

Neurotoxicity of intraneural injection of bupivacaine liposome injectable suspension versus bupivacaine hydrochloride in a porcine model.

OBJECTIVE: To test whether neurotoxic effects of a bupivacaine liposome injectable suspension differ from those of a standard formulation of bupivacaine hydrochloride (HCl) after intraneural injection into the sciatic nerves in pigs. STUDY DESIGN: Prospective, randomized study. ANIMALS: Fifteen pigs, hybrids of Landrace and Large White. METHODS: After the National Ethics Committee approval, 15 pigs were randomly allocated to three groups (n = 5/group) to receive intraneural injections of 4 mL of 1.33% bupivacaine liposome injectable suspension, 0.5% bupivacaine HCl or normal saline. Serial neurologic examinations were conducted to detect sensory and motor response to noxious stimuli using a modified Thalhammer's scale at 2 hour intervals for the first 12 hours after injection and daily thereafter for 2 weeks. Fiber characteristics (density) of the harvested sciatic nerves were measured during histomorphometric analysis. Inflammatory response was studied using immunohistochemical analysis. Data were tested using analyses of variance; p values for paired comparisons were Bonferroni adjusted. RESULTS: Compared with bupivacaine HCl, bupivacaine liposome injectable suspension provided longer sensory (11.2 ± 1.8 hours versus 3.2 ± 1.1 hours, respectively, p < 0.0001) and motor (10.0 ± 2.0 hours versus 4.0 ± 1.4 hours respectively, p < 0.0001) blockade. Histomorphometric parameters were similar among the groups. No changes in axonal density or myelin structure indicative of injury to the sciatic nerves were observed in any of the groups. Number of immunopositive cells did not differ between the bupivacaine liposome injectable suspension (23 ± 6 cells per mm2) and the bupivacaine HCl groups (21 ± 4 cells per mm2), p > 0.90. CONCLUSIONS AND CLINICAL RELEVANCE: Intraneural injections of bupivacaine liposome injectable suspension or bupivacaine HCl in our porcine model did not result in evidence of neurotoxicity.

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.