Rapid shallow megathrust afterslip from the 2021 M8.2 Chignik, Alaska earthquake revealed by seafloor geodesy.

The shallower portions of subduction zone megathrust faults host Earth's most hazardous tsunamigenic earthquakes, yet understanding how and when they slip remains elusive because of challenges making seafloor observations. We performed Global Navigation Satellite System Acoustic seafloor geodetic surveys before and ~2.5 months after the 29 July 2021 Mw (moment magnitude) 8.2 Chignik, Alaska, earthquake and determine ~1.4 meters cumulative co- and post-seismic horizontal displacement ~60 kilometers from the megathrust front. Only for the 2011 Mw 9 Tohoku event have closer subduction zone earthquake displacements been observed. We estimate ~2 to 3 meters of megathrust afterslip shallower than 20 kilometers, a portion of the megathrust on which both inter- and co-seismic slip likely had occurred previously. Our analysis demonstrates that by 2.5 months, shallower and deeper moment had effectively equilibrated on the megathrust, suggesting that its tsunamigenic potential remains no more elevated than before the earthquake.

Continuing megathrust earthquake potential in Chile after the 2014 Iquique earthquake.

The seismic gap theory identifies regions of elevated hazard based on a lack of recent seismicity in comparison with other portions of a fault. It has successfully explained past earthquakes (see, for example, ref. 2) and is useful for qualitatively describing where large earthquakes might occur. A large earthquake had been expected in the subduction zone adjacent to northern Chile, which had not ruptured in a megathrust earthquake since a M âˆ¼8.8 event in 1877. On 1 April 2014 a M 8.2 earthquake occurred within this seismic gap. Here we present an assessment of the seismotectonics of the March-April 2014 Iquique sequence, including analyses of earthquake relocations, moment tensors, finite fault models, moment deficit calculations and cumulative Coulomb stress transfer. This ensemble of information allows us to place the sequence within the context of regional seismicity and to identify areas of remaining and/or elevated hazard. Our results constrain the size and spatial extent of rupture, and indicate that this was not the earthquake that had been anticipated. Significant sections of the northern Chile subduction zone have not ruptured in almost 150 years, so it is likely that future megathrust earthquakes will occur to the south and potentially to the north of the 2014 Iquique sequence.

Hemolysis comparison between the OmniSonics OmniWave Endovascular System and the Possis AngioJet in a porcine model.

PURPOSE: To compare the degree of hemolysis generated during use of the ultrasound-based OmniSonics OmniWave Endovascular System and the Possis AngioJet connected to an Xpeedior-6 catheter. MATERIALS AND METHODS: Twelve 64-145-kg Yorkshire pigs were used as the model because their weight, blood volume, and vessel diameters are comparable to that of adult humans. Six pigs were treated with the OmniWave and six with the AngioJet; half of the pigs in each group were treated in the contralateral iliofemoral arteries and half in the ipsilateral iliofemoral veins. Devices were activated for 10 minutes in patent vessels to represent a worst-case scenario for hemolysis generation. Plasma-free hemoglobin (PfHgb) levels, red blood cell counts, white blood cell (WBC) counts, and platelet counts were measured before and after the procedure, and PfHgb levels were measured every 2 minutes during treatment. RESULTS: The OmniWave generated significantly lower PfHgb levels than the AngioJet (average, 228 vs 1,367 mg/dL; P < .001). The location of activation (arterial vs venous) had no significant effect (P = .575). Compared with OmniWave use, AngioJet use was associated with significantly greater changes from pre- to posttreatment values in WBCs (P = .002), platelets (P = .004), and creatinine (P = .002). AngioJet use was associated with a significant postprocedure decrease in the WBC count (mean, -8,000/microl; 95% confidence interval [CI]: -3,830, -12,170; P = .004) and platelet count (mean, -72,000; 95% CI: -25,000, -120,000; P = .011). With the OmniWave device there were no significant differences between pre- and posttreatment WBC count (P = .127), platelet count (P = .493), and creatinine level (P = .317). CONCLUSIONS: The OmniWave generated approximately one-sixth of the hemolysis the AngioJet created. In addition, animals treated with the AngioJet exhibited a decrease in WBC and platelet counts.

Technique, utility, and safety of awake tracheoplasty using combined laser and balloon dilation.

OBJECTIVES: Laryngotracheostenosis (LTS) is a condition in which the airway is narrowed between the vocal cords and the carina. We seek to examine whether flexible bronchoscopy with neodymium-doped yttrium aluminum garnet (Nd:YAG) laser incision and balloon dilation tracheoplasty is a practical choice in the management of patients with subglottic or tracheal stenosis. METHODS: A retrospective chart review was performed at a tertiary care hospital. All subjects with laryngotracheostenosis treated between January 1, 2000, and April 2005 who underwent endoscopic Nd:YAG laser incision and balloon dilation tracheoplasty performed using topical anesthesia and intravenous sedation were included. RESULTS: A total of 18 patients comprised the study and 36 procedures were performed without complication. Only one procedure was required by eight subjects, while five subjects required two procedures, three subjects had three procedures, one subject had four procedures, and one subject had five procedures until an adequate stable airway was obtained. The average follow-up was 22 months (range 3-55 months). The average body mass index (BMI) was 32.0 kg/m (range = 20.8-42.2 kg/m) and 11 of the 18 subjects (61.1%) were categorized as obese or morbidly obese by BMI criteria. CONCLUSION: Combined Nd:YAG laser incision and balloon dilation in an awake, spontaneously breathing patient is a safe and effective management tool in the treatment of laryngotracheostenosis. This technique may be particularly beneficial in patients who are at increased risk for general anesthesia such as those with morbid obesity or who have had a history of airway problems during anesthesia.

Use of 3-dimensional computed tomography reconstruction studies in the preoperative assessment of patients undergoing balloon dilatation for tracheobronchial stenosis.

BACKGROUND: Balloon dilatation (BD) is a useful method of treating tracheobronchial stenosis (TBS); however, accurate preoperative identification of the lesion is difficult. Three-dimensional computed tomography (3D-CT) is an imaging method that may allow more accurate definition of the lesion(s) preoperatively. STUDY OBJECTIVE: It is the aim of this study to present our finding using 3D-CT as a part of the preoperative evaluation of patients with TBS undergoing BD. METHODS: We studied a prospective case series of 17 consecutive patients who underwent 29 BDs for TBS from a variety of benign and malignant causes at a tertiary care hospital. All patients had a preoperative spiral CT; these data were processed by a software program, VIDA, which was developed at this institution, and 3D-CT reconstruction images of the TBS were created. This enabled accurate preoperative anatomic definition of the lesion. The patients subsequently underwent BD. RESULTS: All 17 patients had lesions identified with 3D-CT. Six patients had tracheal lesions and 12 patients had main stem lesions. One patient had combined tracheal and main stem lesions and 2 other patients had bilateral main stem lesions. Nine out of 17 patients required only one BD. One patient had a failed BD. The remaining 6 patients required more than one BD for optimal results (up to a maximum of 4). The follow-up period ranged from 1 to 34 months. CONCLUSIONS: 3D-CT offers accurate definition of TBS, including anatomic location, number of lesions present and status of airway distal to lesion. In this study, all preoperative lesions were correctly identified prior to BD.

Adverse cerebrovascular effects of intraarterial CO2 injections: development of an in vitro/in vivo model for assessment of gas-based toxicity.

PURPOSE: To assess whether and how CO(2) can cause ischemic injury in the central nervous system after internal carotid artery injection. MATERIALS AND METHODS: In 14 adult pigs, both internal carotid arteries were catheterized via a transfemoral approach. One carotid artery served as control and the other was injected via a prototype gas injector with defined volumes and pressures of gas. Effects were assessed by clinical observation, repeated magnetic resonance (MR) imaging, histopathology, and vital staining. An in vitro flow circuit was used to model injection parameters. RESULTS: Single injections of CO(2) did not produce persistent clinical symptomatology. In vitro conditions were created in which bubbles adhered to the tubing of the circuit, creating functional stenoses, or coalesced into larger bubbles that became trapped, thereby reducing flow and augmenting potential embologenic effects of subsequent injections. With in vitro-derived dual injection parameters, seven pigs underwent two sequential injections of CO(2). All did well after the first injections, but all had adverse effects after the second injections, including involuntary tonic-clonic muscular movements, cardiopulmonary arrest, recurrent intractable seizure activity during recovery, hemorrhagic venous infarcts on gross and histopathologic examination, and blood-brain barrier breakdown on vital staining. MR imaging was not sensitive even after symptomatic intraarterial air injection. CONCLUSIONS: Absence of adverse effects after single bolus injections in pigs does not prove the safety of intracranial CO(2) injections in human patients. Considering the possible deleterious effects of repeat intravascular injections in the highly sensitive system of the brain, it may be prudent for clinical application at other approved sites to let time pass between boluses sufficient to permit absorption of wall-adherent and coalescent bubbles that could cause gas embolic events.