• Mechanism of Antihypertensives

     

    Antihypertensives are a mainstay of emergency department care (whether it be for someone with a systolic blood pressure of 247 or someone who simply is on it for the long-term). Of all the antihypertensives out there, the mechanisms to reduce blood pressure are generally one of three things:

    • Reduce fluid load in the blood vessels: less fluid means less pressure in the blood system
    • Increase or decrease the amount of intracellular calcium available to subsequently cause smooth muscle contraction (and vasoconstriction) or smooth muscle relaxation (and vasodilation), respectively
    • Decrease the amount of cardiac output: less output means less pressure that’s exerted on the system

    The image above illustrates these mechanisms and how these mechanisms can be summarized by one question: does the antihypertensive work on the cardiovascular system, on the kidneys, or on the renin-angiotensin-aldosterone system (RAAS)? Continue reading this post for a table of typical examples of these classes of medications and a bit more detail on what these meds are actually doing.

    Read More…

  • 2017/11/28 - sketchrn

    ED Ventilation Primer

    ED Mechanical VentilationThis diagram illustrates the most common settings that are used with mechanical ventilation in the emergency department. By no means is this intended to be a replacement of proper ventilation training; this is provided as a quick reminder of what the different settings refer to. Note that depending on the ventilator mode, some of the settings are configured automatically (or not required at all).

    As an example, a newly intubated patient is generally placed on assist-control ventilation (see my handy-dandy quick guide to ventilator modes in the ED for more information). It’s used when you want to support every breath that a patient takes regardless of whether or not the machine generated the breath or the patient generated it. With this, there are 4 settings that need to be determined:

    FiO2: 1.0 (100%) – initially, 100% FiO2 is administered to the patient.
    RR: 12 – the respiratory rate is generally within the normal respiratory rate range
    PEEP: 5-10 cm H2O – a small amount of pressure is kept in the ventilator system to keep the alveoli open (especially in cases of acute distress or post-paralytics).
    Vt: 6-8 mL/kg – the expected tidal volume is estimated based on the calculation here.

    Given the manually-set RR and Vt, the ventilator automatically chooses the Flow and PIP to accomodate this.

  • 2017/06/23 - sketchrn

    Pediatric Assessment Triangle

    Pediatric Assessment Triangle: Airway/Appearance + Breathing + CirculationThe Pediatric Assessment Triangle (P.A.T.) is a quick and efficient way to get an overview of a pediatric patient – especially in the emergency department or out in the field. Conveniently, it follows the mantra of emergency medicine: ABCs – airway/appearance, breathing, and circulation. While there are many really good descriptors of what constitutes each side of the triangle (and for a particularly good one, I’d recommend the “Pediatric Assessment Reference Card” from the NY Emergency Medical Services page), I’m a very visual person so I created this one year after a hectic 8-hour triage shift that was predominantly kids.

    (This is what you get for working at a community emergency department).

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  • Signs of GI Bleeds: obvious gastrointestinal bleeding, vital signs indicating blood loss, and lab work indicating blood loss.Signs of Gastrointestinal or Esophageal bleeding largely depends on the source of bleeding: generally, whichever end of the GI tract is “releasing” fresh or bright red blood is closer to the source of the bleed. In the ED, signs of GI bleeding, compensating vital signs, and blood work indicating blood loss are a pretty good indicator to start treatment for GI bleeds.

    Treatments of GI/Esophageal Bleeds including endoscopic treatment, pharmacologic treatments, and use of a esophageal tamponade (or Blakemore/Minnesota tube)In ED, the treatments are largely dependent on the capabilities of a site – for example, a rural ED is unlikely to have either an endoscope or esophageal tamponade so treatment resorts to pharmacologic intervention.

    (Don’t forget to click on the pictures to enlarge).

  • Portal Circulation: blood flow that skips the heart: physiology of organ to target organPortal Circulation is usually talked about in the context of the hepatic portal system: the movement of venous blood from gastrointestinal organs (like the stomach and the small intestines – where nutrients are absorbed from the organ into the vein) into the liver where they are further processed. As with any part of the body, damage to the liver causes subsequent damage to the blood vessels leading in to it. Since the liver is heavily involved with detoxification and metabolism, it usually ends up getting the brunt of the damage caused by substances like alcohol. The damaged blood vessels causes blood to back up into other collateral systems.

    (Don’t forget to click on the pictures to enlarge)

    Esophageal Varices: pathophysiology due to portal hypertension causes backing up of blood through the portocaval anastomosis and subsequent rupture of blood vessels into the esophagus when pressures get excessively large Read More…

  • 2016/10/10 - sketchrn

    Tumour Lysis Syndrome (TLS)

    Tumour Lysis Syndrome: oncology/cancer related complication post-chemotherapy: what to look for and ED treatments

    Tumour Lysis Syndrome (TLS) is a (thankfully) uncommon complication of chemotherapy and cancer treatment. Generally, these would be cancers that are highly proliferative or bulky – think the blood-related cancers and visible organ-tumours – or with chemotherapy agents that are highly active. Since TLS is related to the actual treatment of the tumour, the chance of it occurring is greater at the peak of chemotherapy treatments, usually 7-day post start of treatment. Luckily, it’s pretty easy to diagnose and treat in the ED if the history fits.

  • 2016/09/29 - sketchrn

    Adult ED ECMO, ECLS, and ECPR

    ECMO Circuits: the general circuit used in ED ECMO (E-CPR)

    Adult E-CPR: insertion of a cannula, what's needed in the ED, and important ECMO points

    (Don’t forget to click on the images to see a larger version of it!)

    Of all the new ED techniques/interventions that’s been introduced in the past two decades, I’d say Adult E-CPR (or the initiation of ECMO during unmanageable cardiac arrest) is one of the more exciting interventions to come out – and not without controversy. The premise of E-CPR is simple: for those with a potentially reversible cause of cardiac arrest that has been otherwise unmanaged by traditional (e.g. ACLS) interventions, ECMO should be considered as a treatment modality to bypass the heart while potentially definitive treatment can be arranged. Generally, patients who are likely candidates for ECMO initiation include:

    -Relatively “hospital young”, usually age <60 or 70
    -Witnessed cardiac arrest (i.e. time of cardiac arrest is known)
    -Relatively short period of time from arrest to ECMO initiation, usually <75 minutes
    -No known systemic organ failure

    Some cardiac centres (like the one I work in) also include the following:

    -Cardiac arrest likely due to (a) cardiac or pulmonary ischemia, (b) known cardiac toxin, or (c) hypothermia

    ECMO is a form of respiratory or cardiac bypass that aims to support the body while waiting for or when definitive treatment is performed. First, blood is taken out of the body through a very large-bore venous cannula. The blood moves through the circuit through a pump before gas is exchanged through the oxygenator. In most E-CPR setups, the oxygenator also has an integrated heater to warm up the blood to body temperature. Blood is then returned back to the body via a large-bore arterial cannula.

    And this is just the beginning. There’s so much more to know about ECMO, ECLS, and ECPR that it can (and does) get overwhelming. Ultimately, the main goal of the ED team is keeping the patient alive – until ECMO is initiated, the ED team is responsible for continuing ACLS treatments. While it’s possible to get through an ECPR situation without knowing exactly what’s happening at the foot of the bed (since, ideally, the “code” team is at the head of the bed), understanding what the cardiac and perfusion team does can help prevent confusion in an already stressful situation.

    Before giving a list of amazing ECPR resources, I’m going to digress for a second. Opinions of whether or not ECPR is a good idea is definitely a conversation starter depending on who you talk to. One clinical educator I talked to – who was at a site that does not have an ECPR program – believed ECPR to be “a political decision”, mostly stemmed as a way to “pass off” sick patients to another service (previously, to do something like ECPR required using an operating room and this was after a significant amount of time had already passed). A physician who had just listened to a talk on ECPR described the intervention as merely being a “thrill ride” for the ED staff while not providing any “real” benefits. Talking to staff, however, at a site that does initiate ECMO in the ED shows a different side: a side that advocates and champions for ECPR. Maybe they’ve seen the moderate successes it can bring – studies have shown a varying 30-50% success rate (i.e. survival to hospital discharge) when ECPR was utilized – or maybe they enjoy the thrill of doing critical care work in the ED. Whatever the reason, when the success of current emergency treatment for cardiac arrest is a variable 10-30%, perhaps the possibility of an increase in survival through the use of ECMO is what encourages clinicians and providers on.

    Resources

    ED ECMO (http://edecmo.org/) – an amazing site and podcast about this very topic; I would check this site out first

    Intensive Blog: ECMO (http://intensiveblog.com/category/ecmo/) – another excellent resource, this blog has posts covering all aspects of ECMO. It’s run by the Alfred ICU (in Australia/New Zealand) and includes some of their ECMO protocols

     

     

     

  • 2016/07/23 - sketchrn

    Mechanism of Alcohol Withdrawal

    Mechanism of Alcohol Withdrawal: the unfortunate consequence of a feedback loop doing its job

    (Don’t forget to click on the images to see a larger version of it!) The pathophysiology of alcohol withdrawal is a good example of the body working hard to keep homeostasis – in a manner of speaking. In fact, alcohol withdrawal is probably a good example of your body doing too good of a job at regulating itself in the environment its given; it just doesn’t do a good job when things suddenly disappear.

  • 2016/07/17 - sketchrn

    4 Types of Cranial Bleeds

    Cranial Bleeds (Epidural, Subdural, Intracerebral): Usual causes, symptoms, and definitive treatment

    Cranial Bleeds (Subarachnoid Hemorrhage): Usual causes, symptoms, and definitive treatment

    (Don’t forget to click on the images to see a larger version of it!)

  • 2016/06/28 - sketchrn

    Weight-Bearing Status

    The different weight-bearing statuses that can be ordered on a patient: from full weight-bearing to feather weight-bearing to non weight-bearing.

    (Don’t forget to click on the images to see a larger version of it!)

    I know this is a month late but Happy National Physiotherapy Month (May 2016)! In commemoration of the awesome PTs who help our patients mobilize, I created this document to indicate the different types of weight-bearing statuses that could be ordered (and probably ignored in the emergency department). Just because we (as nurses) don’t know what some of these mean doesn’t mean that we shouldn’t be doing these or that it’s not our duty to know – or so says the physical therapist I work with.

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