Invasive mechanical ventilation using a bilevel PAP ST device in a healthy swine model.

PURPOSE: The Coronavirus Disease 2019 (COVID-19) pandemic may cause an acute shortage of ventilators. Standard noninvasive bilevel positive airway pressure devices with spontaneous and timed respirations (bilevel PAP ST) could provide invasive ventilation but evidence on their effectiveness in this capacity is limited. We sought to evaluate the ability of bilevel PAP ST to effect gas exchange via invasive ventilation in a healthy swine model. METHODS: Two single limb respiratory circuits with passive filtered exhalation were constructed and evaluated. Next, two bilevel PAP ST devices, designed for sleep laboratory and home use, were tested on an intubated healthy swine model using these circuits. These devices were compared to an anesthesia ventilator. RESULTS: We evaluated respiratory mechanics, minute ventilation, oxygenation, and presence of rebreathing for all of these devices. Both bilevel PAP ST devices were able to control the measured parameters. There were noted differences in performance between the two devices. Despite these differences, both devices provided effective invasive ventilation by controlling minute ventilation and providing adequate oxygenation in the animal model. CONCLUSIONS: Commercially available bilevel PAP ST can provide invasive ventilation with a single limb respiratory circuit and in-line filters to control oxygenation and ventilation without significant rebreathing in a swine model. Further study is needed to evaluate safety and efficacy in clinical disease models. In the setting of a ventilator shortage during the COVID-19 pandemic, and in other resource-constrained situations, these devices may be considered as an effective alternative means for invasive ventilation.

Clinical Interpretation of Peripheral Pulse Oximeters Labeled "Not for Medical Use".

The purpose of our study was to clarify limitations of off-label use for low cost nonmedical use (NMU) pulse oximeters by primary care providers. These devices are widely marketed over the Internet and in drugstores but are not intended for medical use or reviewed by the Food and Drug Administration (FDA). Our study compared oxygen saturation (SpO2) in patients from 1 medical use (MU) pulse oximeter to 8 NMU pulse oximeters. Measured arterial oxygenation (SaO2) was compared with SpO2 when available. In patients who were normoxic (SpO2 ≥90%), all oximeters exhibited similar readings. This finding suggests that NMU pulse oximeters may be able to rule out hypoxemia in clinical settings.

The Effectiveness of Dexmedetomidine as a Prophylactic Treatment for Emergence Delirium Among Combat Veterans With High Anxiety: A Randomized Placebo-Controlled Trial.

INTRODUCTION: Emergence delirium (ED) is characterized by agitation, confusion, and violent physical and verbal behavior associated with awakening from general anesthesia. Combat exposure among U.S. military veterans has been identified as a risk factor for ED. Preoperative baseline anxiety was shown to be a predictor of ED, and combat veterans are known to be at high risk for anxiety as well as depression and PTSD. Dexmedetomidine is an alpha-2 receptor agonist proven to mitigate ED in several patient populations. Perioperative use of dexmedetomidine demonstrated promising benefits in pediatric ED but has not been evaluated in combat veterans. MATERIALS AND METHODS: This study was a multi-site, prospective, randomized controlled investigation of 369 patients with a history of military combat exposure who were scheduled for elective surgery with a general anesthetic as the primary means of anesthesia. The trial was funded by the Tri-Service Nursing Research Program Grant HU0001-14-TS05 (N14-PO3) and approved by the Institutional Review Boards at the Naval Medical Center San Diego, Womack Army Medical Center, Walter Reed National Military Medical Center, and the Uniformed Services University of the Health Sciences, Bethesda, MD. All subjects were administered the State-Trait Anxiety Inventory (STAI) to evaluate baseline anxiety. Those enrolled subjects with a low anxiety level (STAI < 39) (n = 215) were placed in the observational arm of the study. Those with a high anxiety level (STAI ≥ 39) were placed in the experimental arm (n = 153) and were further randomized to treatment with intraoperative dexmedetomidine infusion (1 µg/kg bolus at induction, followed by a 0.6 µg/kg/h infusion continued until emergence) (n = 75) or a placebo intraoperative infusion (n = 75). Following the delivery of the prescribed anesthetic, all subjects were observed for signs of ED using the Pediatric Anesthesia Emergence Delirium (PAED) Scale. The patient and data recorder remained blinded to the randomization results. RESULTS: The central tendencies of demographics and clinical characteristics are reported. PAED among those randomized to dexmedetomidine (median 7, interquartile interval (IQI) 5.2-9.2) tended to be less (P < .0001) than that of those randomized to control (median 12, IQI 10-13). Dexmedetomidine was found to be the most important predictor of PAED (35% relative importance), followed by Patient Health Questionnaire (14%), STAI-Trait (9%), and PTSD Checklist-Military Version (8%); the overall rankings are featured. Randomization to receipt of dexmedetomidine was associated with a 3.7-unit reduction (95% CI 2.5-4.9) in PAED (P < .001) in a linear model controlling for several variables, and the directionality of the effect persisted upon regularization in a penalized linear model. CONCLUSIONS: Dexmedetomidine was effective at reducing PAED among combat veterans who were experiencing symptoms of pre-operative anxiety (i.e., STAI-State ≥39). Although psychological morbidity is not unique to the military population, combat veterans carry some of the highest rates of anxiety, PTSD and depression compared to the general population. Dexmedetomidine can be safety employed by anesthesia providers to reduce symptoms of ED in the perioperative period. The double-blind randomized, controlled study design strengthens our analyses; however, this study did not control for the type of surgical procedure or the duration of anesthetic. Furthermore, we only enrolled patients with combat exposure experiencing symptoms of anxiety and did not investigate the role of dexmedetomidine in combat veterans with less anxiety. Further study of the relationship between psychological comorbidities, ED, and dexmedetomidine is warranted.

Intraoperative Transesophageal Echocardiography in Management of Acute Type I Aortic Dissection With Malperfusion: A Case Report.

Acute type I aortic dissection is a life-threatening emergency with potentially devastating complications, including end-organ malperfusion. Early detection of malperfusion with intraoperative imaging allows for efficient transition to appropriate interventions. We present a case of a 65-year-old male with acute type I aortic dissection who underwent emergent surgical repair of the aortic root and hemiarch followed by acutely worsening distal malperfusion. The use of intraoperative transesophageal echocardiography played a critical role in visualizing diversion of flow to the false lumen, prompting urgent vascular surgery consultation and life-saving thoracic endovascular aortic repair.

Intracardiac Heterotopic Liver Presenting as a Right Atrial Myxoma: A Case Report.

Intracardiac heterotopic liver is a very rare entity. The most unique aspect of this entity is the increased carcinogenic potential of the tissue. This condition must be considered when assessing an intracardiac mass along with more common differential diagnoses such as neoplasms, thrombi, and vegetations. In this report, we present a case of a patient who presented to cardiac surgery for elective excision of a right atrial mass that was determined to be an accessory liver lobe. We discuss the diagnostic challenges, clinical management, and surgical and anesthetic implications of this rare finding.

Ambulatory Surgery Has Minimal Impact on Sleep Parameters: A Prospective Observational Trial.

STUDY OBJECTIVES: The presence of obstructive sleep apnea (OSA) in ambulatory surgical patients causes significant perioperative concern; however, few data exist to guide clinicians' management decisions. The objective of this study was to measure changes in perioperative sleep parameters among an ambulatory surgery population. METHODS: This study is a prospective, observational study of ambulatory patients undergoing orthopedic surgery on an extremity. Study subjects completed three unattended home sleep apnea tests: baseline before surgery, the first night after surgery (N1), and third night after surgery (N3). Anesthesia and surgical teams were blinded to study participation and patients received routine perioperative care. RESULTS: Two hundred three subjects were enrolled and 166 completed the baseline home sleep test. Sixty-six (40.0%) had OSA at baseline, 35 patients received a new diagnosis, and 31 patients had a previous diagnosis of OSA. Of those with a previous diagnosis, 20 (64.5%) were compliant with continuous positive airway pressure therapy. Respiratory event index and SpO2 nadir did not significantly change postoperatively from baseline. Cumulative percentage of time oxygen saturation < 90% significantly increased N1 as compared to baseline for all patients except for those with moderate to severe OSA. CONCLUSIONS: Ambulatory surgery had minimal effect on sleep parameters and there was no increase in adverse events among patients with either treated or untreated OSA. CLINICAL TRIAL REGISTRATION: Registry: ClinicalTrials.gov; Title: Evaluation of Sleep Disordered Breathing Following Ambulatory Surgery; Identifier: NCT01851798; URL: https://clinicaltrials.gov/ct2/show/study/NCT01851798.

Tumescent technique without epinephrine for endovenous laser therapy and serum lidocaine concentration.

OBJECTIVE: Endovenous laser therapy (EVLT) requires tumescent lidocaine anesthesia. Although it is well known that the absorption of local anesthetic varies according to the injection site, little evidence exists establishing the maximum recommended safe dose for extravascular injections such as those used for EVLT. The aim of this study was to evaluate plasma concentration of lidocaine over time after administration of tumescent lidocaine during EVLT procedures in healthy volunteers. METHODS: Between January 2011 and February 2013, 10 healthy patients scheduled for an EVLT procedure performed in a hospital setting were recruited to participate in an observational study. For each subject, a total of 10 venous samples were obtained for analysis after surgical injection of the tumescent lidocaine solution (0.1% concentration). Samples were collected at baseline (before the surgical procedure start) and then every 30 minutes for the first 2 hours after the initial lidocaine injection. Thereafter, venous samples were obtained every 2 hours, with the last sample drawn 12 hours after the surgeon's initial lidocaine injection. All specimens were drawn from a dedicated intravenous catheter, immediately placed in a heparinized blood collection tube, and centrifuged for 10 minutes at 3000 rpm. Plasma was then removed with a pipette and stored at -70 °C until analyzed. Total and free plasma lidocaine concentrations were determined by immunoassay. Plasma lidocaine concentrations were normalized by peak concentration for statistical comparisons. RESULTS: Laboratory data were available for nine of the 10 volunteers. The mean total lidocaine dose administered was 6.38 (± 2.2) mg/kg (range, 3.57-10.7 mg/kg). The total lidocaine blood levels ranged from 0.48 (± 0.28) to 1.3 (± 0.49) mcg/mL. The free lidocaine blood levels ranged from nondetectable to 0.76 (± 0.43) mcg/mL. The average total time of injection for the group was 32.8 (± 10.0) minutes (range, 21-49 minutes). Among all dose ranges, both total and free lidocaine peak blood level ratios occurred at times 60 to 120 minutes (P < .05). No value considered in the statistical analysis exceeded 5 mcg/mL at any time. CONCLUSIONS: Tumescent lidocaine without epinephrine for EVLT procedures produces a peak serum concentration at 60 to 120 minutes. The peak plasma concentration as observed with the standard institutional dosing of tumescent lidocaine appeared below the threshold for human toxicity.

Myoclonus following a Peripheral Nerve Block.

Myoclonus is an extremely rare perioperative complication following neuraxial anesthesia. It has also been reported to occur due to peripheral nerve lesions. We report a case of self-limiting myoclonus following a routine peripheral nerve block in an otherwise healthy patient.