The latest medical research on Anesthesiology

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Extrafasicular and Intraperineural, but No Endoneural, Spread after Deliberate Intraneural Injections in a Cadaveric Study.


The intraneural injection of local anesthetics is an accepted cause of nerve injury related to regional anesthesiaThe intrafascicular versus extrafascicular spread of local anesthetics is hypothesized to be necessary for nerve damage to occur WHAT THIS ARTICLE TELLS US THAT IS NEW: Using the ultrasound-guided injection of heparinized blood into the nerves of cadavers, the extrafascicular spread of injectate was observedIntrafascicular spread of injectate was rarely observed, making this an unlikely route of nerve damage after accidental intraneural injection BACKGROUND:: There is confusion regarding the spread of intraneurally injected local anesthetic agents during regional anesthesia. The aim of this research was to deliberately inject a marker that does not leave the neural compartment into which it is injected, and then to study the longitudinal and circumferential spread and possible pathways of intraneural spread.

After institutional review board approval, we intraneurally injected 20 and 5 ml of heparinized blood solution under ultrasound guidance into 12 sciatic nerves in the popliteal fossa and 10 median nerves, respectively, of eight fresh, unembalmed cadavers using standard 22-gauge "D" needles, mimicking the blocks in clinical conditions. Ultrasound evidence of nerve swelling confirmed intraneural injection. Samples of the nerves were then examined under light and scanning electron microscopy.

Extrafascicular spread was observed in all the adipocyte-containing neural compartments of the 664 cross-section samples we examined, but intrafascicular spread was seen in only 6 cross-sections of two nerves. None of the epineurium, perineurium, or neural components were disrupted in any of the samples. Spread between the layers of the perineurium was a route of spread that included the perineurium surrounding the fascicles and the perineurium that formed incomplete septa in the fascicles. Similar to the endoneurium proper, subepineural compartments that did not contain any fat cells did not reveal any spread of heparinized blood solution cells. No "perineural" spaces were observed within the endoneurium. We also did not observe any true intrafascicular spread.

After deliberate intraneural injection, longitudinal and circumferential extrafascicular spread occurred in all instances in the neural compartments that contained adipocytes, but not in the relatively solid endoneurium of the fascicles.

Lung Recruitment in Obese Patients with Acute Respiratory Distress Syndrome.


Obesity increases the propensity to atelectasis in acute respiratory distress syndrome, but the optimal approach to reversing this atelectasis is uncertain WHAT THIS ARTICLE TELLS US THAT IS NEW: A clinical crossover study comparing three approaches to titrate positive end-expiratory pressure (PEEP; according to a fixed table, according to end-expiratory esophageal pressure, and targeting the best compliance during a decremental PEEP trial) found that a recruitment maneuver followed by decremental PEEP minimized atelectasis and overdistension, and best restored compliance and oxygenation without causing hemodynamic impairment BACKGROUND:: Obese patients are characterized by normal chest-wall elastance and high pleural pressure and have been excluded from trials assessing best strategies to set positive end-expiratory pressure (PEEP) in acute respiratory distress syndrome (ARDS). The authors hypothesized that severely obese patients with ARDS present with a high degree of lung collapse, reversible by titrated PEEP preceded by a lung recruitment maneuver.

Severely obese ARDS patients were enrolled in a physiologic crossover study evaluating the effects of three PEEP titration strategies applied in the following order: (1) PEEPARDSNET: the low PEEP/FIO2 ARDSnet table; (2) PEEPINCREMENTAL: PEEP levels set to determine a positive end-expiratory transpulmonary pressure; and (3) PEEPDECREMENTAL: PEEP levels set to determine the lowest respiratory system elastance during a decremental PEEP trial following a recruitment maneuver on respiratory mechanics, regional lung collapse, and overdistension according to electrical impedance tomography and gas exchange.

Fourteen patients underwent the study procedures. At PEEPARDSNET (13 ± 1 cm H2O) end-expiratory transpulmonary pressure was negative (-5 ± 5 cm H2O), lung elastance was 27 ± 12 cm H2O/L, and PaO2/FIO2 was 194 ± 111 mmHg. Compared to PEEPARDSNET, at PEEPINCREMENTAL level (22 ± 3 cm H2O) lung volume increased (977 ± 708 ml), lung elastance decreased (23 ± 7 cm H2O/l), lung collapse decreased (18 ± 10%), and ventilation homogeneity increased thus rising oxygenation (251 ± 105 mmHg), despite higher overdistension levels (16 ± 12%), all values P < 0.05 versus PEEPARDSnet. Setting PEEP according to a PEEPDECREMENTAL trial after a recruitment maneuver (21 ± 4 cm H2O, P = 0.99 vs. PEEPINCREMENTAL) further lowered lung elastance (19 ± 6 cm H2O/l) and increased oxygenation (329 ± 82 mmHg) while reducing lung collapse (9 ± 2%) and overdistension (11 ± 2%), all values P < 0.05 versus PEEPARDSnet and PEEPINCREMENTAL. All patients were maintained on titrated PEEP levels up to 24 h without hemodynamic or ventilation related complications.

Among the PEEP titration strategies tested, setting PEEP according to a PEEPDECREMENTAL trial preceded by a recruitment maneuver obtained the best lung function by decreasing lung overdistension and collapse, restoring lung elastance, and oxygenation suggesting lung tissue recruitment.

Failure to Rescue as a Surgical Quality Indicator: Current Concepts and Future Directions for Improving Surgical Outcomes.


Over the past decade, failure to rescue-defined as the death of a patient after one or more potentially treatable complications-has received increa...

Perioperatively Acquired Weakness.

Anesthesia and Analgesia

Skeletal muscle failure in critical illness (intensive care unit-acquired weakness) is a well-known complication developing early during intensive care unit stay. However, muscle weakness during the perioperative setting has not yet been investigated.

We performed a subgroup investigation of a prospective observational trial to investigate perioperative muscle weakness. Eighty-nine patients aged 65 years or older were assessed for handgrip strength preoperatively, on the first postoperative day, at intensive care unit discharge, at hospital discharge, and at 3-month follow-up. Functional status was evaluated perioperatively via Barthel index, instrumental activities of daily living, Timed Up and Go test, and functional independence measure. After exclusion of patients with intensive care unit-acquired weakness or intensive care unit stay of ≥72 hours, 59 patients were included into our analyses. Of these, 14 patients had additional pulmonary function tests preoperatively and on postoperative day 1. Blood glucose was measured intraoperatively every 20 minutes.

Handgrip strength significantly decreased after surgery on postoperative day 1 by 16.4% (P < .001). Postoperative pulmonary function significantly decreased by 13.1% for vital capacity (P = .022) and 12.6% for forced expiratory volume in 1 second (P = .001) on postoperative day 1. Handgrip strength remained significantly reduced at hospital discharge (P = .016) and at the 3-month follow-up (P = .012). Perioperative glucose levels showed no statistically significant impact on muscle weakness. Instrumental activities of daily living (P < .001) and functional independence measure (P < .001) were decreased at hospital discharge, while instrumental activities of daily living remained decreased at the 3-month follow-up (P = .026) compared to preoperative assessments.

Perioperatively acquired weakness occurred, indicated by a postoperatively decreased handgrip strength, decreased respiratory muscle function, and impaired functional status, which partly remained up to 3 months.

Improving Access to Safe Anesthetic Care in Rural and Remote Communities in Affluent Countries.

Anesthesia and Analgesia

Inadequate access to anesthesia and surgical services is often considered to be a problem of low- and middle-income countries. However, affluent na...

Late fracture of Groshong ports: A report of the three cases.

J Vasc Access

Totally implantable venous access devices are valuable tools for total parenteral nutrition, chemotherapy, and long-term intravenous therapy. However, late catheter fracture is a well-known complication of totally implantable venous access device, particularly in Groshong silicone catheter. Recently, a specific type of totally implantable venous access device made with Groshong silicone has been introduced to facilitate power injection of contrast medium for enhanced computed tomography.

We reported three cases of catheter fracture in power-injectable Groshong silicone totally implantable venous access device. From May 2012 to August 2014, 66 patients underwent power-injectable Groshong silicone totally implantable venous access device implantation at our institution, with a median follow-up of 20.1 (range 0.2-58.1) months. The catheters in all patients were inserted into the internal jugular vein under ultrasound guidance and were connected to the port implanted in the upper chest through the subcutaneous tunnel. Chemotherapy was administered using these routes. Fractures of all three cases specifically showed a torn catheter section: smooth surface on one side, and a rough edge on the other side of the catheter, suggesting that long-term repeated stretch force may be related with the mechanism of fracture.

Totally implantable venous access devices with Groshong silicone catheters, if inserted via the internal jugular vein, have a potential risk for late catheter fracture.

Bedside tests for predicting difficult airways: an abridged Cochrane diagnostic test accuracy systematic review.


Although bedside screening tests are routinely used to identify people at high risk of having a difficult airway, their clinical utility is unclear...

Meta-analysis of intracavitary electrocardiogram guidance for peripherally inserted central catheter placement.

J Vasc Access

Recently, intracavitary electrocardiogram technology has been applied to peripherally inserted central catheter placement and demonstrates many potential advantages. However, the tip positioning accuracy of intracavitary electrocardiogram technology compared to conventional X-ray method is unknown.

We did a meta-analysis to compare the tip positioning accuracy between intracavitary electrocardiogram technology and conventional X-ray method.

We searched several databases, including Cochrane Library, PubMed, Web of science, and Embase. Additional studies were identified through hand searches of bibliographies and Internet searches. All human studies published in full text, abstract, or poster form were eligible for inclusion. Search terms included peripherally inserted central catheter, PICC, intracavitary electrocardiogram, IC-ECG, EKG, ECG, and catheter tip location.

Only randomized controlled trials of using intracavitary electrocardiogram technology versus X-ray method for peripherally inserted central catheter placement were included. All studies included adult patients aged at least 18 years.

Independent extraction of articles by two authors using predefined data fields, including study quality indicators. Of the 178 citations identified, 5 studies that included 1672 patients met the eligibility criteria. It was found that statistical heterogeneity existed among the various studies (I2 = 16%, p < 0.00001); therefore, the fixed effect model was used in the meta-analysis (p < 0.05). The meta-analysis compared the tip positioning accuracy between intracavitary electrocardiogram technology and X-ray method and showed that intracavitary electrocardiogram technology had a better positioning accuracy (odds ratio: 2.88, 95% confidence interval: 2.15-3.87, p < 0.0001).

Only five randomized trial met inclusion criteria, and the lack of an incomplete search led to the publication bias seen in these results.

The intracavitary electrocardiogram method had a more favorable positioning accuracy versus traditional X-ray method for peripherally inserted central catheter placement in adult patients. The intracavitary electrocardiogram can be a promising technique to guide tip positioning of peripherally inserted central catheter.

α2δ-1-Bound N-Methyl-D-aspartate Receptors Mediate Morphine-induced Hyperalgesia and Analgesic Tolerance by Potentiating Glutamatergic Input in Rodents.


Presynaptic N-methyl-D-aspartate receptors contribute to opioid tolerance and hyperalgesia as well as neuropathic painThe α2δ-1 protein subunit enhances presynaptic N-methyl-D-aspartate receptor activity WHAT THIS ARTICLE TELLS US THAT IS NEW: Using mouse and rat models, it was demonstrated that α2δ-1 is essential for the increase in presynaptic N-methyl-D-aspartate receptor activity seen during chronic morphine exposureInhibiting α2δ-1 activity using gabapentin or genetically deleting the gene coding for α2δ-1 results in diminished opioid tolerance and hyperalgesia BACKGROUND:: Chronic use of μ-opioid receptor agonists paradoxically causes both hyperalgesia and the loss of analgesic efficacy. Opioid treatment increases presynaptic N-methyl-D-aspartate receptor activity to potentiate nociceptive input to spinal dorsal horn neurons. However, the mechanism responsible for this opioid-induced activation of presynaptic N-methyl-D-aspartate receptors remains unclear. α2δ-1, formerly known as a calcium channel subunit, interacts with N-methyl-D-aspartate receptors and is primarily expressed at presynaptic terminals. This study tested the hypothesis that α2δ-1-bound N-methyl-D-aspartate receptors contribute to presynaptic N-methyl-D-aspartate receptor hyperactivity associated with opioid-induced hyperalgesia and analgesic tolerance.

Rats (5 mg/kg) and wild-type and α2δ-1-knockout mice (10 mg/kg) were treated intraperitoneally with morphine twice/day for 8 consecutive days, and nociceptive thresholds were examined. Presynaptic N-methyl-D-aspartate receptor activity was recorded in spinal cord slices. Coimmunoprecipitation was performed to examine protein-protein interactions.

Chronic morphine treatment in rats increased α2δ-1 protein amounts in the dorsal root ganglion and spinal cord. Chronic morphine exposure also increased the physical interaction between α2δ-1 and N-methyl-D-aspartate receptors by 1.5 ± 0.3 fold (means ± SD, P = 0.009, n = 6) and the prevalence of α2δ-1-bound N-methyl-D-aspartate receptors at spinal cord synapses. Inhibiting α2δ-1 with gabapentin or genetic knockout of α2δ-1 abolished the increase in presynaptic N-methyl-D-aspartate receptor activity in the spinal dorsal horn induced by morphine treatment. Furthermore, uncoupling the α2δ-1-N-methyl-D-aspartate receptor interaction with an α2δ-1 C terminus-interfering peptide fully reversed morphine-induced tonic activation of N-methyl-D-aspartate receptors at the central terminal of primary afferents. Finally, intraperitoneal injection of gabapentin or intrathecal injection of an α2δ-1 C terminus-interfering peptide or α2δ-1 genetic knockout abolished the mechanical and thermal hyperalgesia induced by chronic morphine exposure and largely preserved morphine's analgesic effect during 8 days of morphine treatment.

α2δ-1-Bound N-methyl-D-aspartate receptors contribute to opioid-induced hyperalgesia and tolerance by augmenting presynaptic N-methyl-D-aspartate receptor expression and activity at the spinal cord level.

Neural inertia and differences between loss of and recovery from consciousness during total intravenous anaesthesia: a narrative review.


Most anaesthetists using target-controlled infusion systems will have observed that the calculated effect-site concentration at loss of consciousne...

An Anesthesiologist's Perspective on the History of Basic Airway Management: The "Modern" Era, 1960 to Present.


This fourth and last installment of my history of basic airway management discusses the current (i.e., "modern") era of anesthesia and resuscitatio...

Failure to Debrief after Critical Events in Anesthesia Is Associated with Failures in Communication during the Event.


Debriefing after an actual critical event is an established good practice in medicine, but a gap exists between principle and implementation.

Failure to debrief after critical events is common among anesthesia trainees and likely anesthesia teams. Communication breakdowns are associated with a high rate of the failure to debrief.

Debriefing after an actual critical event is an established good practice in medicine, but a gap exists between principle and implementation. The authors' objective was to understand barriers to debriefing, characterize quantifiable patterns and qualitative themes, and learn potential solutions through a mixed-methods study of actual critical events experienced by anesthesia personnel.

At a large academic medical center, anesthesiology residents and a small number of attending anesthesiologists were audited and/or interviewed for the occurrence and patterns of debriefing after critical events during their recent shift, including operating room crises and disruptive behavior. Patterns of the events, including event locations and event types, were quantified. A comparison was done of the proportion of cases debriefed based on whether the event contained a critical communication breakdown. Qualitative analysis, using an abductive approach, was performed on the interviews to add insight to quantitative findings.

During a 1-yr period, 89 critical events were identified. The overall debriefing rate was 49% (44 of 89). Nearly half of events occurred outside the operating room. Events included crisis events (e.g., cardiac arrest, difficult airway requiring an urgent surgical airway), disruptive behavior, and critical communication breakdowns. Events containing critical communication breakdowns were strongly associated with not being debriefed (64.4% [29 of 45] not debriefed in events with a communication breakdown vs. 36.4% [16 of 44] not debriefed in cases without a communication breakdown; P = 0.008). Interview responses qualitatively demonstrated that lapses in communication were associated with enduring confusion that could inhibit or shape the content of discussions between involved providers.

Despite the value of proximal debriefing to reducing provider burnout and improving wellness and learning, failure to debrief after critical events can be common among anesthesia trainees and perhaps anesthesia teams. Modifiable interpersonal factors, such as communication breakdowns, were associated with the failure to debrief.