Breandan Sullivan

Isoflurane Prevents Delayed Cell Death in an Organotypic Slice Culture Model of Cerebral Ischemia

Background General anesthetics reduce neuronal death caused by focal cerebral ischemia in rodents and by in vitro ischemia in cultured neurons and brain slices. However, in intact animals, the protective effect may enhance neuronal survival for only several days after an ischemic injury, possibly because anesthetics prevent acute but not delayed cell death. To further understand the mechanisms and limitations of volatile anesthetic neuroprotection, the authors developed a rat hippocampal slice culture model of cerebral ischemia that permits assessment of death and survival of neurons for at least 2 weeks after simulated ischemia. Methods Survival of CA1, CA3, and dentate gyrus neurons in cultured hippocampal slices (organotypic slice culture) was examined 2–14 days after 45 min of combined oxygen–glucose deprivation at 37°C (OGD). Delayed cell death was serially measured in each slice by quantifying the binding of propidium iodide to DNA with fluorescence microscopy. Results Neuronal death was greatest in the CA1 region, with maximal death occurring 3–5 days after OGD. In CA1, cell death was 80 ± 18% (mean ± SD) 3 days after OGD and was 80–100% after 1 week. Death of 70 ± 16% of CA3 neurons and 48 ± 28% of dentate gyrus neurons occurred by the third day after OGD. Both isoflurane (1%) and the N-methyl-d-aspartate antagonist MK-801 (10 &mgr;m) reduced cell death to levels similar to controls (no OGD) for 14 days after the injury. Isoflurane also reduced cell death in CA1 and CA3 caused by application of 100 but not 500 &mgr;m glutamate. Cellular viability (calcein fluorescence) and morphology were preserved in isoflurane-protected neurons. Conclusions In an in vitro model of simulated ischemia, 1% isoflurane is of similar potency to 10 &mgr;m MK-801 in preventing delayed cell death. Modulation of glutamate excitotoxicity may contribute to the protective mechanism.

Effects of neuroprotective cocktails on hippocampal neuron death in an in vitro model of cerebral ischemia.

Cocktails of neuroprotectants acting at different parts of the ischemic injury cascade may have advantages over single agents. This study investigated, singly and in combination, the neuroprotective efficacy of an energy substrate (3.5 mM fructose 1,6-bisphosphate, FBP), an antagonist of NMDA receptors (1 and 10 &mgr;M MK-801), a free-radical scavenger (100 &mgr;M ascorbate), an adenosine A1 receptor agonist (10 &mgr;M 2-chloroadenosine), and an inhibitor of neurotransmission (2% isoflurane). These agents were evaluated for their ability to prevent loss and morphologic damage of CA1 neurons in rat hippocampal slices when these agents were administered during 30 minutes in vitro ischemia (combined oxygen/glucose deprivation at 37°C) followed by 5 hours of recovery. Ten &mgr;M MK-801, alone or in combination with the other compounds, prevented loss of CA1 neurons and preserved their histologic appearance. Isoflurane, which prevents glutamate receptor-dependent cell death in this model, was also protective. Protection against neuron loss was also found when a subtherapeutic concentration of MK-801 (1 &mgr;M) was combined with 2-chloroadenosine (which indirectly causes NMDA receptor suppression), but not FBP or ascorbate. The authors conclude that in this model, the strategy of antagonizing NMDA receptors appears more protective than fructose-1,6-bisphosphate, 2-chloroadenosine or ascorbate.

Transesophageal echocardiography in noncardiac thoracic surgery.

In high-risk surgeries with medically complicated patients, transesophageal echocardiography (TEE) adds an additional level of monitoring with which few can disagree. This article presents multiple applications of TEE that can assist both the anesthesiologist and the surgeon through major noncardiac thoracic surgery. It highlights how TEE can be used as an adjuvant to lung resection surgery; TEE as a monitor during lung transplantation; TEE to assess patients for extracorporeal membrane oxygenation; TEE for thoracic aortic surgery; and TEE in the assessment of patients with acute pulmonary hypertension undergoing noncardiac thoracic surgery.

Con Early Extubation in the Operating Room Following Cardiac Surgery

Ultra-fast-track anesthesia for cardiac surgery introduces risks to the patient that may be mitigated by transferring the patient to the intensive care unit with a secure airway. These risks include poorly controlled pain leading to catecholamine surges that result in arrhythmias, strain on fresh suture lines, and potentially myocardial ischemia. On the converse side, the patients frequently require titration of potent narcotic pain medicine that can lead to hypoxemia and hypercarbia in the immediate postoperative stage causing myocardial dysfunction. Finally, the economic benefit of ultra-fast-track anesthesia is questionable and until there is a complete cost analysis that includes operating room time, cost of ultra-fast-track medications, and compares the cost of reintubation and delayed surgical operation, it is difficult to weigh in on the cost benefit advocated in the literature.

Update on Perioperative Right Heart Assessment Using Transesophageal Echocardiography

Purpose of the review. This review aims to summarize recent findings relevant for perioperative 2- and 3-dimensional imaging of the right heart with transesophageal echocardiography. Special attention is given to developments that are likely to affect future approaches for prevention and therapy of perioperative right heart failure. Recent findings. Three-dimensional transesophageal echocardiography techniques are becoming more common for the evaluation of anatomy, volumes, and functional indices. Summary. Right heart failure continues to contribute to morbidity and mortality in the context of cardiothoracic surgery. The advent and widespread clinical use of innovative tools permitting more accurate echocardiographic assessment of the right heart will open the door to renewed interest in novel therapeutic strategies.

Insertion and Management of Temporary Pacemakers

Temporary pacemakers are used in a variety of critical care settings. These life-saving devices are reviewed in 2 major categories in this review: first, the insertion and management of epicardial pacemakers after and during cardiac surgery; and second, the insertion of transvenous temporary pacemakers for the emergent treatment of bradyarrhythmias. Temporary epicardial pacemakers are used routinely in patients recovering from cardiac surgery. Borrowing from advances in cardiac resynchronization therapy there are many theoretical and untested benefits to pacing the postoperative cardiac surgery patient. Temporary transvenous pacing is traditionally an emergency procedure to stabilize patients suffering from hemodynamically unstable bradyarrhythmia. We review the traditional and expanding use of transvenous pacemakers inside and outside the operating room.

TnT: blowing the cover from perioperative myocardial injury.

This article has been selected for the Anesthesiology CME Program. Learning objectives and disclosure and ordering information can be found in the CME section at the front of this issue.

Heated humidified high-flow nasal cannula oxygen after thoracic surgery — A randomized prospective clinical pilot trial

Background Thoracic surgery patients are at high‐risk for adverse pulmonary outcomes. Heated humidified high‐flow nasal cannula oxygen (HHFNC O2) may decrease such events. We hypothesized that patients randomized to prophylactic HHFNC O2 would develop fewer pulmonary complications compared to conventional O2 therapy. Methods and patients Fifty‐one patients were randomized to HHFNC O2 vs. conventional O2. The primary outcome was a composite of postoperative pulmonary complications. Secondary outcomes included oxygenation and length of stay. Continuous variables were compared with t‐test or Mann‐Whitney‐U test, categorical variables with Fishers Exact test. Results There were no differences in postoperative pulmonary complications based on intention to treat [two in HHFNC O2 (n = 25), two in control (n = 26), p = 0.680], and after exclusion of patients who discontinued HHFNC O2 early [one in HHFNC O2 (n = 18), two in control (n = 26), p = 0.638]. Discomfort from HHFNC O2 occurred in 11/25 (44%); 7/25 (28%) discontinued treatment. Conclusions Pulmonary complications were rare after thoracic surgery. Although HHFNC O2 did not convey significant benefits, these results need to be interpreted with caution, as our study was likely underpowered to detect a reduction in pulmonary complications. High rates of patient‐reported discomfort with HHFNC O2 need to be considered in clinical practice and future trials. HighlightsPulmonary complications were rare after thoracic surgery.Patient‐reported discomfort was more frequent with the use of HHFNC O2.This pilot study did not indicate a beneficial effect of prophylactic HHFNC O2.Larger samples are necessary to definitively ascertain benefits of HHFNC O2.

130: CLINICAL IMPACT OF AN EDUCATIONAL COURSE FOR HOSPITAL RAPID RESPONSE TEAMS

Introduction: Throughout the country, patients are increasingly likely to require critical care intervention. Numerous studies have shown that early recognition and intervention can improve outcomes in hospitalized patients. Many hospitals are utilizing rapid response teams (RRTs) to help identify a