Grand Rounds Recap 10.16.19
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Taming the SRU - Interventions for the Crashing Asthma Patient WITH Dr. Mand
Asthma is a common disease process that we see and treat in the ED on a daily basis. Most of the time the exacerbation is mild enough that with treatment a patient may be discharged, or perhaps brought in for an ED-based protocolized treatment pathway. However, there are patients who present in extremis, such as the case presented this week by Dr. Mand. We know that placing a crashing asthmatic patient on a ventilator is a terrifying last resort, so what are the tools that we can deploy to prevent reaching that point?
Give Magnesium Sulfate
This compound has both smooth muscle relaxant and anti-inflammatory properties, although the mechanisms behind these effects is poorly understood. It has been shown to reduce hospitalization rates with a number needed to treat of only 14 and improves pulmonary function. Dosing is 2g given over 15-20 minutes.
Consider Heliox
Heliox is a mixture of helium and oxygen in variable ratios. In an acute asthma exacerbation constriction of smaller airways increases turbulent flow and impedes the flow of air and consequently gas exchange in the alveoli. Helium has a much lower density than room air and so increases laminar flow of gas through the airways. This has no direct bronchodilatory or antiinflammatory effects, but does provide a more efficient vehicle by which to deliver other medications that do have those effects into the bronchioles. However, there is a price - this requires at least a 60% concentration of helium in the gas mixture and so by simple arithmetic you won’t be able to deliver higher than a 40% concentration of oxygen. Heliox has been shown to reduce rates of hospitalization and improve lung function, especially in patients with severe exacerbations.
Reach for Epi
Epinephrine is a familiar tool in the ED with a broad spectrum of applications. In the context of severe asthma exacerbations it functions primarily through beta-adrenergic receptor agonism to dilate bronchioles and reduce airway resistance. Despite the relative ubiquity of this medication there is actually no high quality data supporting its use as the best studies currently in existence are still from the 1980s and all involve a relatively small number of patients. However, there have been a number of higher quality studies looking for harm, and when all is said and done it appears that epinephrine is generally safe to use even if efficacy is questionable. At most there is an increase in ectopy, tachycardia, and hypertension, but none of these adverse effects were clinically significant in the studies where they were examined.
What about Ketamine?
Ketamine has similar beta-adrenergic bronchodilatory properties as other medications used to treat asthma, but also offers some anticholinergic action as well. In addition, it inhibits norepinephrine re-uptake and so increases a patient’s own endogenous catecholamines. The data on ketamine for asthma exacerbations is mixed: some studies have shown improvement in peak expiratory flow rate (PEFR) in mild to moderate exacerbations with a dose-dependent response. However, other studies have noted no improvement and an increase in rate of hospitalizations. There is certainly more territory to be explored before we can include ketamine in our standard armamentarium for asthma.
R4 Capstone - ESRD and Dialysis WITH Dr. Scanlon
End-stage renal disease is a familiar entity to emergency providers. We provide care for patients along the entire spectrum of disease from the predisposing condition, to the complications that come with the condition, and to the emergencies that may ultimately lead to a final common pathway of mortality. It therefore behooves us to understand the history, the biomechanical processes, and the physiologic consequences of ESRD and dialysis. Dr. Scanlon takes us through an excellent survey of these very topics this week.
Dialysis a term that is derived from Greek that essentially means to separate two things that are intertwined, hinting at the principle of separating metabolites and toxins from the serum into which they are incorporated. The first experiments that would lead to modern dialysis were conducted by Thomas Graham at the University of Glasgow in 1854 when he placed an ox bladder full of urine into a vessel of distilled water and was then able to isolate compounds from the urine that had crossed through the bladder membrane into the water. John Jacob Ables applied the concept in canine studies in 1913, Bjorn Haas had the first human dialysis patients in 1928 (although all three of them died), and then Willem Johan Kolff was the first to successfully treat a human being in the 1940s.
Although the details of the biomechanics can be intricate, they can be distilled to basic principles. The basic concept is that blood leaves the human body, is scrubbed through a filter where urea and nitrogenous wastes are removed, and then is returned to the body. Small molecules are removed from the blood by diffusion - a countercurrent flow between blood and dialysate provides a chemical gradient for this exchange. By the same principle, desirable compounds can be introduced into the blood by increasing their relative concentration in the dialysate solution. Larger molecules are removed by a process called ultrafiltration - where components of blood are forced across a semipermeable membrane by pressurization.
There are two basic types of processes: intermittent hemodialysis, in which larger volumes of blood are filtered over a short span of time, and continuous renal replacement therapy (CRRT) whereby smaller volumes are filtered over longer times and at lower flow rates. CRRT is an umbrella term that comprises a host of different subtypes, but at the most basic level of understanding are used for patients who may not tolerate large, rapid shifts in volume status well.
Why is it important for emergency physicians to care about the physiologic processes and complications surrounding dialysis and ESRD? Simply stated, these patients present to the ED frequently, are at higher risk for a myriad of different pathology, and have a five-year survival rate of only 35% after starting dialysis.
AV fistulas are a common type of vascular access used for dialysis. However, they alter the fundamental physiologic principles of the human circulatory system by forming a direct connection between the resistance type arterial system and the capacitance type venous system. This leads to an increase in blood return to the right atrium and ventricle, producing higher pulmonary arterial pressures, resulting in the development of pulmonary hypertension, and then on to left sided heart failure. There is an increased mortality in the first 120 days following AV fistula creation.
Intradialytic hypotension is another common problem that occurs in approximately 30% of all patients undergoing dialysis. Aside from rapid changes in volume status there is also thought to be a component of autonomic dysfunction that drives this resulting from damage to autonomic nerves due to chronic uremia. There is an increase in mortality and prolonged hospitalization in patients following intermittent hemodialysis sessions.
Sepsis is also 50 times more common in dialysis patients than the general population, affecting 145.4 patients per 1000 and carries a 100-fold increase in annual mortality. Intermittent hemodialysis is an independent risk factor for mortality in sepsis for several reasons. Regular percutaneous access increases their risk for introduction of bacteria into the blood. Beyond this we are likely bad at judging volume status in ESRD patients due to their inherent dysautonomia and atypical response to fluid shifts. Finally, they also suffer an accelerated rate of granulocyte senescence and dysfunction.
In-hospital cardiac arrest and mortality are also twice as likely as in the general population. ESRD patients have a 3 to 4-fold increase in mortality after PCI and their mortality after myocardial infarction is 59 and 73% at one and two years, also much higher than the general population. Chronically elevated troponin is a common lab abnormality that we encounter with ESRD patients. We have a tendency to disregard this when the elevation is low-level and stable over the course of weeks to months and tend to think of it as the patient’s baseline. There may be truth to the idea that this elevation is chronic and a baseline finding, but it is also an independent risk factor for mortality even in patients that are not being seen for ACS. This observed increase in troponin confers an increase in the hazard ratio for all-cause mortality of 2.4 to 4.0.
Finally, hyperkalemia is very common in ESRD patients. There is some evidence that chronic hyperkalemia produced by slow rises may be better tolerated, but this data is not good quality. It has been shown that there is increased mortality from hyperkalemia from levels greater than 5.7 with linear increases up to 6.0.
In summation, hemodialysis places unique stressors on human physiology and puts patients at increased risk of morbidity and mortality as compared to the general population. It is incumbent upon us to respect theses stressors and the risks so that we can provide the best treatment possible to our patients.
R1 Clinical Diagnostics - Shoulder and Elbow Xrays WITH Drs. Crawford and Scanlon
For background see the full post here
Anterior Shoulder Dislocations
Anterior shoulder dislocation commonly occurs from a fall onto an outstretched arm and presents often with visible deformity and internal rotation/adduction of the arm. Plain films are a standard diagnostic modality and can clearly show the characteristic misalignment of the humeral head with the glenoid fossa.
Reducing this dislocation may require procedural sedation, but often it can be accomplished with some combination of systemic analgesia and local or regional anesthesia. Common techniques for local and regional anesthesia include intra-articular local anesthetic injection and interscalene and suprascapular nerve blocks. These latter two in particular should be performed with ultrasound guidance.
Techniques for reduction include traction-countertraction (pulling the arm until the shoulder relocates), the Stimson technique (prone patient with arm over the edge of the bed, add weight suspended from wrist and increase every 5-10 minutes until spontaneous reduction), the Leidelmeyer technique (supine patient, adduct elbow to chest wall, externally rotate the flexed arm), and the Cooper/Milch technique (arm held overhead with axial traction and external rotation with or without scapular manipulation).
Be on the alert for common associated complicating injuries. The Hill-Sachs lesion is a cortical compression fracture of the posterolateral humeral head and the Bankart lesion is an avulsion fracture of the antero-inferior glenoid labrum.
Proximal Humerus Fractures
Falling onto an outstretched arm may also result in a proximal humerus fracture. This is also easily diagnosed with x-ray and may be characterized by the Neer classification system (a grading system that accounts for the number of fracture fragments and the degree of displacement; this system may be useful to know when discussing the injury with orthopedic colleagues).
Be on the lookout for axillary nerve injuries with proximal humerus fractures. This nerve is responsible for sensation over the deltoid as well as motor function of the deltoid muscle. Test sensation and be sure your patient can abduct the arm above 90 degrees to assess for injury. Also be sure to dutifully assess for subtle arterial injuries.
Fractures with only a single break and no associated neurovascular injuries may be managed in the ED with sling and follow up, but fractures into two or more parts or with neurovascular compromise will require more urgent surgical intervention.
Radial Head Fractures
Finally, falling onto an outstretched hand can produce radial head fractures. These fractures can be subtle on x-ray and are at times only hinted at by the displacement of the periarticular fat pads
Associated injuries with radial head fractures include damage to the radial nerve, which may manifest as wrist drop or decreased sensation over the dorsum of the hand. Ulnar nerve injuries can present with loss of function in the intrinsic muscles of the hand (finger apposition, abduction, and adduction), or loss of sensation in the fourth and fifth digits. Finally, the median nerve may also be injured by a radial head fracture and present with an inability to adduct or oppose the thumb, pronate the forearm, or with loss of sensation through the first through third digits. There are multiple ways to assess nerve function in the hand, and one such is to have your patient play “paper-rock-scissors.” Finally, radial head fractures can be complicated by disruption of the radio-ulnar syndesmosis (the interosseous membrane) and dislocation of the distal radio-ulnar joint, known eponimously as the Essex-Lopresti injury.
When the fracture is subtle and only noted by displacement of the fat pads they can be placed in a sling alone, but displaced fractures require immobilization and often surgical intervention.
R2 CPC - Intussusception WITH Drs. Hunt and Bryant
Intussusception is the term used to describe the condition of a segment of bowel “telescoping” into another segment. It is far less common in adults than in children, and when encountered in an adult population is most often due to underlying malignancy. The segments involved can be entero-enteric in which 30% are associated with malignancy; colo-colic, in which 66% are associated with malignancy; or ileo-colic, in which association with malignancy is actually rare. Aside from cancer, examples of other causes in an adult population include adhesions, appendicitis, pancreatitis, inflammatory bowel disease, and scleroderma.
Aside from being rare, adult intussusception can also be difficult to diagnose because it most commonly presents with vague symptoms of chronic, nonspecific abdominal pain. Diagnosis is typically based on a variety of imaging modalities from plain films, upper GI series, barium enemas, ultrasound and CT. CT is the most sensitive of all, however a negative scan cannot rule out the diagnosis because it may happen that the segments are not telescoped at the time of the scan. CT may also help to identify the lead point that provided the nidus for intussusception to happen. Endoscopy can also be used to diagnose, but surgery can offer definitive treatment in addition to diagnosis. Air enemas are typically not used in adults because of the much higher association with malignancy - it can cause intraluminal seeding of tumor cells and perforation of edematous, friable bowel tissue.
In summary, intussusception in adults is rare, but often associated with cancer, presents with vague symptoms, and is best diagnosed by CT and treated with surgery.
R4 Case Follow Up - PJP Pneumonia and Methemoglobinemia WITH Dr. Gauger
This week Dr. Gauger provides a review of HIV-related infections and Pneumocystis jirovecci (PJP) pneumonia in his R4 case follow up. Recall that there is a correlation between varying degrees of CD4 lymphopenia and different opportunistic infections. Above 500 patients are at risk for zoster and community acquired pneumonia, much like the general population. Once they fall below that threshold they become at increased risk for tuberculosis, and once below 200 they are susceptible to PJP, cryptococcus, thrush and fungal pneumonias. Finally, below the level of 50, patients become at increased risk from CMV, CNS cryptococcal infection, MAC, and CNS lymphoma.
Colonization by PJP is actually quite common in the general population and is both the most common opportunistic infection in HIV+ patients and is AIDS-defining. Mortality is estimated to be 10-20% in HIV+ patients. It is actually the host immune response that produces alveolar damage, which is why the first presentation may be that of the “immune reconstitution syndrome” when patients are newly started on antiretroviral therapy, allowing their own immune cells to begin fighting the infection and producing inflammatory response.
PJP may present with nonspecific symptoms and is typically characterized by diffuse “ground-glass opacities” on chest xray or CT. The diagnosis may also be made by BAL or PCR. The mainstay of both prophylaxis and treatment is trimethoprim-sulfamethoxazole. Second line agents include pentamidine and atovaquone, and steroids are used as adjunctive therapy when the PaO2 is less than 70 or the Aa-gradient is greater than 35.
Incidentally, some HIV+ patients may be prescribed primaquine for prophylaxis against PJP. Be aware if they are because this medication may induce methemoglobinemia. This occurs when ferrous iron in hemoglobin becomes oxidized to the ferric state and causes hemoglobin no longer be able to carry oxygen. Clinically this produces hypoxia, cyanosis, and cardiac dysrhythmias and requires treatment when methemoglobin levels rise above 20%. We all know to treat this with methylene blue, but perhaps less well known is that you must also give dextrose to provide metabolic substrate for the biochemical reaction of methylene blue.
Quarterly Simulation - Gastric Lavage WITH Drs. lafollette and Li
In this round of the Quarterly Sim we discussed indications for and procedural techniques of gastric lavage in a simulated case of witnessed calcium channel blocker overdose.
Gastric lavage is a technique that aims to decontaminate the stomach of toxic substances by sequential administration and aspiration of small volumes of fluid. The procedure was more frequently used in the past, but due to the potential for complications several national-level organizations now recommend against the routine use. Despite this, there are situations where it can be a life-saving technique and therefore should be familiar to emergency physicians should there be a strong indication.
We recommend that this be done in consultation with poison control and in cases that there is a known life-threatening ingestion within one hour of presentation to the ED. Contraindications include corrosive ingestions that may cause damage to the GI tract, ingestions with unclear timing or known to be beyond one hour, or if the ingestion is not life threatening. It is important to consider that there can be damage to the mouth, esophagus, or stomach cause by the procedure itself. There is also risk of pushing the toxin beyond the pylorus into the more distal portions of the GI tract where it can be more rapidly absorbed, and furthermore it can cause complications due to aspiration, hypoxia, and hypothermia. Children are more prone to electrolyte abnormalities and water toxicity.
To perform the procedure, first make sure that the patient’s airway is secured by intubation. Place the patient in the left lateral decubitus position and the head angled slightly downwards and measure the appropriate length for a large orogastric tube, typically 36-40 french for adults. Lubricate and carefully pass this tube into the stomach and confirm placement either by aspiration or xray. Provide the first dose of activated charcoal and then give alloquots of 250cc warmed saline, aspirating back the same volume. Repeat this process of irrigation and aspiration until the stomach contents run clear and then give the second dose of activated charcoal.
For a video demonstration - check out Class of 2014 Alumnus Dr. Gillian Beauchamp’s Video
