Ultrasonography in the preoperative difficult airway assessment.

To evaluate the utility of ultrasound for detection of the difficult intubation in a preoperative setting. PubMed, Ovid, CINAHL Plus Full Text, and Google Scholar searches using ["difficult airway" OR "difficult intubation" OR "difficult laryngoscopy" OR "difficult ventilation"] AND [ultrasonography OR sonography OR ultrasound] without date limitations. Abstracts without publications, case reports, letters, textbooks, unrelated topics, or foreign language articles were excluded. Ancestry references were included from the reviewed articles. Two reviewers independently performed the query. Each study was reviewed using the STARD checklist to assess blinding, incomplete data reporting, subject attrition, and selection of appropriate statistical tests. Ten studies were included. All used convenience sampling of adult subjects requiring direct laryngoscopy in elective surgical settings. One study is retrospective and nine are prospective observational. Populations included non-obese, obese, pregnant, and thyroidectomy patients in the United States, Turkey, Israel, Canada, Portugal, and China. Airway locations scanned are variable using different protocols and patient positioning. The outcome variable is uniformly the Cormack-Lehane Grade. 114 of the 681 total subjects had difficult laryngoscopies. Significance for sonographic prediction of difficult laryngoscopy occurred at three locations: hyomental distance [52.6 ± 5.8 mm (p < 0.01)], anterior tissue at the hyoid bone [16.9 mm (95 % CI 11.9-21.9) and 15.9 ± 2.7 mm (p < 0.0001)], and the thyrohyoid membrane [34.7 mm (95 % CI 28.8-40.7) and 23.9 ± 3.4 mm (p < 0.0001) and 28.25 ± 4.43 mm (p < 0.001)]. The vocal cords and sternal notch levels have conflicting significance. Limitations include the heterogeneous populations and lack of standard scanning protocols.

Effects of Intraosseous Tibial vs. Intravenous Vasopressin in a Hypovolemic Cardiac Arrest Model.

INTRODUCTION: This study compared the effects of vasopressin via tibial intraosseous (IO) and intravenous (IV) routes on maximum plasma concentration (Cmax), the time to maximum concentration (Tmax), return of spontaneous circulation (ROSC), and time to ROSC in a hypovolemic cardiac arrest model. METHODS: This study was a randomized prospective, between-subjects experimental design. A computer program randomly assigned 28 Yorkshire swine to one of four groups: IV (n=7), IO tibia (n=7), cardiopulmonary resuscitation (CPR) + defibrillation (n=7), and a control group that received just CPR (n=7). Ventricular fibrillation was induced, and subjects remained in arrest for two minutes. CPR was initiated and 40 units of vasopressin were administered via IO or IV routes. Blood samples were collected at 0.5, 1, 1.5, 2, 2.5, 3, and 4 minutes. CPR and defibrillation were initiated for 20 minutes or until ROSC was achieved. We measured vasopressin concentrations using high-performance liquid chromatography. RESULTS: There was no significant difference between the IO and IV groups relative to achieving ROSC (p=1.0) but a significant difference between the IV compared to the CPR+ defibrillation group (p=0.031) and IV compared to the CPR-only group (p=0.001). There was a significant difference between the IO group compared to the CPR+ defibrillation group (p=0.031) and IO compared to the CPR-only group (p=0.001). There was no significant difference between the CPR + defibrillation group and the CPR group (p=0.127). There was no significant difference in Cmax between the IO and IV groups (p=0.079). The mean ± standard deviation of Cmax of the IO group was 58,709±25, 463 pg/mL compared to the IV group, which was 106,198±62, 135 pg/mL. There was no significant difference in mean Tmax between the groups (p=0.084). There were no significant differences in odds of ROSC between the tibial IO and IV groups. CONCLUSION: Prompt access to the vascular system using the IO route can circumvent the interruption in treatment observed with attempting conventional IV access. The IO route is an effective modality for the treatment of hypovolemic cardiac arrest and may be considered first line for rapid vascular access.