Anesthesiology

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WHAT WE ALREADY KNOW ABOUT THIS TOPIC: Crystalloid solutions leave the circulation quickly, whereas colloids remain for hours, thus promoting hemodynamic stability. However, colloids are expensive and promote renal toxicity in critical care patients. Whether goal-directed intraoperative tetrastarch colloid administration reduces complications or promotes renal injury remains unknown. WHAT THIS ARTICLE TELLS US THAT IS NEW: In a large randomized trial comparing intraoperative goal-directed 6% hydroxyethyl starch with goal-directed lactated Ringer's solution in patients having major abdominal surgery, 6% hydroxyethyl starch reduced neither a composite of serious complications nor the duration of hospitalization...

WHAT WE ALREADY KNOW ABOUT THIS TOPIC: Airway closure has been described in chronic obstructive pulmonary disease, acute respiratory distress syndrome, and cardiac arrest patientsThis phenomenon makes tidal inflation start only after a critical airway opening pressure is overcomeAlthough previously reported during general anesthesia, airway closure was partially misinterpreted WHAT THIS ARTICLE TELLS US THAT IS NEW: Airway closure affects a relevant proportion of obese patients undergoing general anesthesia in supine position, with a variable degree of airway opening pressureWith Trendelenburg pneumoperitoneum, airway opening pressure increases consistently with esophageal pressure and pneumoperitoneum insufflation pressure: consequently, transalveolar pressure, lung volumes, and alveolar recruitment do not varyAirway closure yields bedside misinterpretation of respiratory mechanics and underestimation of actual alveolar pressure in the intraoperative settingIt is an occult phenomenon that generates an airway pressure threshold, whereby inspiratory gas does not inflate the lung unless the airway opening pressure is exceeded BACKGROUND:: Airway closure causes lack of communication between proximal airways and alveoli, making tidal inflation start only after a critical airway opening pressure is overcome...

WHAT WE ALREADY KNOW ABOUT THIS TOPIC: Dental procedures under sedation can cause hypoxic events and even death. However, the mechanism of such hypoxic events is not well understood. WHAT THIS ARTICLE TELLS US THAT IS NEW: Apnea and hypopnea occur frequently during dental procedures under sedation. The majority of the events are not detectable with pulse oximetry. Insertion of a nasal tube with small diameter does not reduce the incidence of apnea/hypopnea. BACKGROUND: Intravenous sedation is effective in patients undergoing dental procedures, but fatal hypoxemic events have been documented...

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WHAT WE ALREADY KNOW ABOUT THIS TOPIC: High tidal volumes and pressures may worsen acute lung injury, sometimes resulting in a trade-off between inflicted damage versus inadequate ventilation WHAT THIS ARTICLE TELLS US THAT IS NEW: In a rat model of experimental lung injury, gradually increasing tidal volume to a known injurious level may result in less (or in some circumstances, more) damage BACKGROUND:: This study hypothesized that, in experimental mild acute respiratory distress syndrome, lung damage caused by high tidal volume (VT) could be attenuated if VT increased slowly enough to progressively reduce mechanical heterogeneity and to allow the epithelial and endothelial cells, as well as the extracellular matrix of the lung to adapt...

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WHAT WE ALREADY KNOW ABOUT THIS TOPIC: Preclinical and clinical studies suggest that lidocaine might be neuroprotective, which could benefit surgical patients at risk of neurologic compromise WHAT THIS ARTICLE TELLS US THAT IS NEW: This multicenter trial of intravenous lidocaine administered during and after cardiac surgery did not show an effect on cognition at 6 weeks postoperatively BACKGROUND:: Cognitive decline after cardiac surgery occurs frequently and persists in a significant proportion of patients...

WHAT WE ALREADY KNOW ABOUT THIS TOPIC: Mesenchymal stromal cells are multipotent adult stem cells with the capacity to differentiate into multiple cell types and have immunomodulatory properties that have been shown to have substantial therapeutic promise in preclinical acute lung injury modelsMesenchymal stromal cells release extracellular vesicles, which are small, spherical membrane fragments comprising distinct populations including both exosomes and microvesicles, which have therapeutic effects in several disease modelsMesenchymal stromal cells are activated or primed by the injury microenvironment, which may be replicated by prior activation of the mesenchymal stromal cells WHAT THIS ARTICLE TELLS US THAT IS NEW: In a rat model of Escherichia coli-induced pneumonia, extracellular vesicles derived from human umbilical cord mesenchymal stromal cells primed with interferon-γ more effectively attenuated E...

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WHAT WE ALREADY KNOW ABOUT THIS TOPIC: Perioperative hypotension is associated with cardiovascular events in patients having noncardiac surgery, but it is unknown if the severity of preexisting coronary artery disease determines susceptibility to the cardiovascular risks of perioperative hypotension WHAT THIS ARTICLE TELLS US THAT IS NEW: In patients who had risk factors for, or known, coronary artery disease and were having noncardiac surgery, perioperative hypotension and degree of coronary artery disease on preoperative coronary computed tomographic angiography were independently associated with perioperative cardiovascular death and myocardial infarctionPerioperative hypotension was associated with cardiovascular events regardless of the degree of coronary artery disease on preoperative coronary computed tomographic angiography BACKGROUND:: Perioperative hypotension is associated with cardiovascular events in patients having noncardiac surgery...

WHAT WE ALREADY KNOW ABOUT THIS TOPIC: Children with obstructive sleep apnea are at greater risk for postoperative hypoxia and other respiratory events as compared with children without this disorderThere is some reason to believe that children with obstructive sleep apnea may be at greater risk for opioid-induced respiratory depression due to increased sensitivity to the drugs WHAT THIS ARTICLE TELLS US THAT IS NEW: The authors hypothesized that children with obstructive sleep apnea would be more sensitive to the effects of an opioid (remifentanil) on pupil size-a very good indicator of opioid effectsWhile remifentanil did reduce pupil size in the expected dose-related fashion, there were no differences between children with obstructive sleep apnea and those withoutWhile the authors did not observe any differences in the effect of remifentanil on respiration, the study was not designed to examine this factor in detail BACKGROUND:: Opioids are a mainstay of perioperative analgesia...

WHAT WE ALREADY KNOW ABOUT THIS TOPIC: 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...

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WHAT WE ALREADY KNOW ABOUT THIS TOPIC: Debriefing after an actual critical event is an established good practice in medicine, but a gap exists between principle and implementation. WHAT THIS ARTICLE TELLS US THAT IS NEW: 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. BACKGROUND: Debriefing after an actual critical event is an established good practice in medicine, but a gap exists between principle and implementation...

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This fourth and last installment of my history of basic airway management discusses the current (i.e., "modern") era of anesthesia and resuscitation, from 1960 to the present. These years were notable for the implementation of intermittent positive pressure ventilation inside and outside the operating room. Basic airway management in cardiopulmonary resuscitation (i.e., expired air ventilation) was de-emphasized, as the "A-B-C" (airway-breathing-circulation) protocol was replaced with the "C-A-B" (circulation-airway-breathing) intervention sequence...

WHAT WE ALREADY KNOW ABOUT THIS TOPIC: 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)...