Jon-Emile S. Kenny MD [@heart_lung] The relative simplicity of extending one’s finger onto the tissue overlaying a major artery belies the complicated forces generating an arterial pulse. Descriptions and physiological elucidations have been put forth across the decades, yet even today the machinations relating cardiac contraction to a waxing and waning arterial wall are a bit [… read more]
Jon-Emile S. Kenny MD [@heart_lung] “He walked away across the room, his cowboy boots echoing like pistol shots.” -Sylvia Plath Background Implicit in resuscitation is speed. Throughout training we are zealously instructed that ‘time is tissue’ for all manners of compromised perfusion. We envision spendthrift mitochondria chewing through oxygen without regard to withering supply; as such, [… read more]
Jon-Emile S. Kenny MD [@heart_lung] When we model the circulation at the bedside, we resort to generalizations. While these mechanistic heuristics don’t completely capture the complexity of hemodynamics, they do help us think quickly when confronted by clinical urgency. For example, distilling ‘venous return’ into an upstream pressure and downstream pressure separated by a single resistance, [… read more]
Jon-Emile S. Kenny MD [@heart_lung] Pulmonary Elastic Ergotrauma There are hidden hemodynamics in respiratory mechanics, as previously discussed. Recall that these relationships are illustrated by comparing volume-pressure, or compliance curves. Trans-pulmonary pressure, which approximates pulmonary stress, is the pressure in the airway compartment less the pleural pressure [1]. In a passive, mechanically-ventilated patient, the trans-pulmonary pressure [… read more]
Beta-blockers have generally been considered safe and beneficial for patients with COPD, but a new randomized trial calls that assumption into doubt. The use of oral beta blockers without a cardiac indication appeared to double the risk of hospitalization for people experiencing a COPD exacerbation. Authors randomized 532 patients with moderate or severe COPD with [… read more]
Targeted temperature management (TTM, or therapeutic hypothermia) has become standard therapy after cardiac arrest, especially for ventricular tachycardia and fibrillation–so called shockable rhythms. A new randomized trial has shown that deep, prolonged cooling after cardiac arrest from non-shockable rhythms (PEA and asystole) improved neurologic outcomes. But how robust were the results, and should they change [… read more]
Intensive insulin therapy to maintain blood glucose in the normal range has immense intuitive appeal. Hyperglycemia is associated with bad outcomes in numerous conditions, and we have the tools at hand to rigorously control it. How could that not help people? Unfortunately, intensive insulin therapy doesn’t seem to help at all, and may harm patients. [… read more]
The FDA is advising physicians that in post-approval data, 30-day survival rates with Abiomed’s Impella RP right ventricular assist device have been only 17%, compared to 73% in the RECOVER RIGHT study leading to the device’s approval in 2017. There were only 60 patients in the post-approval study, who had significantly worse clinical status at [… read more]
Jon-Emile S. Kenny MD [@heart_lung] “I’m burnin’ through the sky, yeah Two hundred degrees, That’s why they call me Mister Fahrenheit” -Freddie Mercury Part 1 gave a brief overview of the mechanisms of atrial fibrillation [AF] as well as pertinent features of rate controlling agents and anticoagulation. In this brief second part, nuanced features of ventricular [… read more]
Jon-Emile S. Kenny MD [@heart_lung] with illustrations by Carla M Canepa MD [@_carlemd_] “The habit of writing for my eye is good practice. It loosens the ligaments.” ― Virginia Woolf Case A 28 year old woman with known severe mitral stenosis from rheumatic heart disease presents with acute onset shortness of breath. Her acute dyspnea began while [… read more]
Jon-Emile S. Kenny MD [@heart_lung] Remarkably, non-invasive cardiology did not begin with ultrasound but rather as investigations into systolic time [1]. Indeed, studies on the duration of systole began in 1875 with Garrod who showed that the left ventricular ejection time [LVET] – the time that the aortic valve is open and ejecting blood – varies [… read more]
Well-done bag-mask ventilation can produce adequate gas exchange for the vast majority of cardiac arrest patients, but does not provide a secure airway and is physically taxing. Patients in cardiac arrest undergoing CPR tend to immediately receive bag-mask ventilation, which is often interrupted to perform endotracheal intubation. To facilitate intubation, chest compressions may also be [… read more]
by Salynn Boyles, Contributing Writer, MedPage Today Cardiovascular event risk may increase in smokers who start using the cessation-assist drug varenicline (Chantix), according to findings from an observational study. The retrospective analysis of medical records for close to 57,000 new users of varenicline living in Ontario, Canada, showed a statistically significant 34% increased risk for [… read more]
Jon-Emile S Kenny MD [@heart_lung] “What is memory but a story about how we have lived?” -Mark Doty During the recent ‘Hospitalist and the Resuscitationist’ conference in Montreal, there were discussions around the hemodynamics of prone positioning as well as using venous Doppler as a hemodynamic metric. Much of this discussion was generated and driven [… read more]
Bi-level noninvasive ventilation (NIV) in patients with obesity hypoventilation syndrome (OHS) can help reverse left ventricular hypertrophy, according to a study from Spain. Patients with OHS treated with continuous positive airway pressure (CPAP) did not experience the same benefits. Bi-level NIV (commonly referred to by its most popular trade name, BiPAP) is known to improve pulmonary [… read more]
The U.S. FDA is warning physicians against prescribing the antibiotic clarithromycin to patients with coronary artery disease. In long-term follow up of a randomized controlled trial, there was an unexpectedly higher rate of death in patients who received a two-week treatment course of clarithromycin, compared to placebo. FDA has added a new warning to clarithromycin’s [… read more]
People with chronic obstructive pulmonary disease (COPD) had an increased rate of heart attacks and strokes in the first month after starting long-acting inhaled bronchodilators. That’s the conclusion of an observational study from Taiwan, published in JAMA Internal Medicine. Researchers analyzed data on 284,220 Taiwanese adults with COPD who had never used bronchodilators, and were started on [… read more]
Overview Vasopressors and inotropes are cornerstones in the management of shock syndromes. Understanding vasopressors’ receptor activity and resultant pharmacological response enables clinicians to select the ideal vasopressor(s) for a patient suffering from shock. The following table outlines common vasopressors/inotropes and their general receptor activity profiles.1,2 Drug Dose α1 ß1 ß2 DA V1 V2 cAMP Norepinephrine [… read more]
N-acetylcysteine (NAC) and sodium bicarbonate are commonly provided to patients undergoing angiographic procedures with intravenous contrast. Small randomized trials had suggested NAC or bicarbonate or both could prevent kidney injury from so-called contrast nephropathy. That practice has no benefit, based on results of a large randomized trial showing neither NAC nor bicarb improved outcomes after [… read more]
Jon-Emile S. Kenny MD [@heart_lung] “Upward, not northward.” -E. A. Abbott A pressure chamber within a pressure chamber; the heart within the thorax. These are two pumps beating in-and-out of time, varying in physiology and pathophysiology between patients and within any one patient during the arc of an illness. As such, when we inspect the [… read more]
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