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OCT
10

Podcast 85 - Thoughts On Roc Dosing #TwoVariables

A few days ago I put up a thought experiment blog on generalizing the dose of rocuronium to 100 mg for anyone over the age of 18 years old. You can find that post here.

 

 

Here are my thoughts: 

 

1. Based off height not weight. 

 

2. Some the dosing range of Roc is very wide 0.9 to 2 mg/kg. 100mg would give 1.2 mg/kg for any male up to 6ft 2inches and 2mg/kg for some a male at 5 ft. Both of these are within acceptable dosing recommendations. Only variable is length of paralysis.

 

3. The argument of commonplace and laziness I can sympathize with- yet I don’t buy it. If anyone has ever watched an anesthesiologist dose medications it is anything but a perfect science. Why? Knowing how the drugs work opens up some freedom. Not recommending free lance dosing-but in some situations we are being pedantic over things that don’t matter.

 

4.Shock dosed higher? Yes I say double it. 

 

5.We will lose our math skills- this is the caveman fire argument that we saw with direct vs video laryngoscopy. Psh

 

 

 

My wicked smart friend Joey Loehner had some fiery angst built up!

I asked him to channel it into a blog for a view from the "this is a stupid idea" vantage point.

 

Rebuttal to The Fixed Dose Paralytics Thought Experiment

 

While I rarely disagree with FOAMed’s power couple- the post this morning hits on something

that I am very passionate about.

 

To clarify

I am not against fixed-dose Paralytics; I am against Fixed-Dose Medicine. We are the

professionals in the world of Prehospital Medicine, and the continual dumbing down of what we

do is the biggest danger to our profession and our patients.

 

*The obvious caveat to weight-based dosing are meds such as ASA, Nitro, etc., that only come

in one preparation*

 

Reasoning

The rationale for always dosing based on weight is many-pronged. First, it is the

most accurate dose for the actual patient in front of you. Second, it keeps your med math skills

strong. Third, it narrows the difference between the Ped/Neo population and the Adult

population. Now let’s break down each point!

 

Most Accurate

Medications should always be dosed based on the way they are designed to

be dosed- which is weight! It is important to note that some medications are dosed based on

Ideal Body Weight (IBW) and some are dosed based on Actual Body Weight (ABW). It is

important to know the difference. Meds dosed based on IBW will have a theoretical Max Dose

(i.e. 99% of the population isn’t over 7’, so having a max dose that may cut off the 7’6”

Basketball player is a pretty minimal risk), whereas meds that are dosed based on ABW will

have no realistic Max Dose. We have all seen “My 600lb Life”. Giving our patients the correct

dose of the medication ensures the safety of the pt and the effectiveness of the medication

given. We are caring for the patient in front of us, not the hypothetical patient that Fixed-Dose

Guidelines assume is running around everywhere. This seems like a no-brainer.

 

Math Skills

Let’s all be honest for a moment- we suck at estimating ABW. We suck even more

at med math. For systems that run off of a Fixed-Dose premise (i.e. 2mg for this, 5mg for this,

100mg for this, etc..), there is little math in day to day patient care. This inevitably leads to the

reduction in skill at performing needed calculations under pressure. Additionally, the chances of

a med error will be significantly increased when different concentrations of a particular

medication are introduced to the system (due to shortage, cost, availability, etc.). This also

leads to another HUGE problem for a lot of clinicians- Rounding! This is a slight tangent, but

something that really grinds my gears. I cannot count how many times I have been proctoring a

scenario and the clinician comes up with a number (say 160mg of Ketamine for the RSI of an

80kg pt), and immediately rounds that up to an easier number to remember (like 200mg). That

is a dosing difference of 20%!! We should give the right dose of the right drug to the right patient

via the right route at the right time- every time. It is a simple concept!

 

Narrowing the Gap

Now, for the culmination of why I believe this is so important! One of the

areas that most clinicians struggle with is Pediatric medication dosing. This is a perceptual

problem that results from the way most clinicians are taught to treat kids. Kids are not small

 

adults, adults are large kids! The dosing for almost every drug that covers both peds and adults

is the exact same--at the weight-based dose. If we lay a stronger foundation when introducing

concepts to student paramedics, then we could help to reduce the med errors, stress, and

confusion that often result during pediatric calls for service.

The Solution- We begin by teaching a single Weight-Based Dose for every applicable

medication in the drug box. This dose will hold true for all ages of patients! This allows for

comfort and repetition with med math and the dosing of medications for all patient populations. I

also strongly believe that it will reduce the frequency of med errors, as med math will become a

much more frequently used skill. Frequency and practice increase the competency of a clinician

with a specified skill.

 

Barriers

I believe that the two biggest barriers to this becoming commonplace are the “The

Safety Net” concept, and the general Laziness/Unwillingness to change of some clinicians. I

don’t believe that the latter really needs to be expounded upon, so I will explain the concept of

the Safety Net. Many Clinical Managers and Medical Director’s worry about med errors, and

having a Safety Net for providers on difficult/task saturating calls is their solution for preventing

errors. I recognize this idea and believe that it is a very valid concern. I believe that the idea

behind most Fixed-Dose drug dosages is to help cognitively offload the provider, and minimize

the odds of that provider freezing-up or making an error on the scene.

 

This is undoubtedly a good thing to have, and helps to protect both the provider and the patient. Common Safety Net

systems such as Handtevy and Broselow are a great fallback to prevent the provider from

making a substantial error. However, these should never be the “go-to” for the clinician.

It is important to have adequate safety nets in place to help prevent medication errors, clinician

stress, and organizational liability. However, these Safety Nets should never become the

primary method of providing patient care. We should always make every effort to give the exact

dose for the exact patient in front of us, not for some hypothetical 100kg person.

 

alright now go check out the podcast! 

 

 

 

Original author: Tyler Christifulli
1
OCT
01

Podcast 84 - Cold Reads & Ventilation (Part 1)

The Dreaded Cold Read

Does anyone ever send you a cold read? A cold read is when you get a piece of information, but really no context. An example of this would be the ECG or lab panel that you get sent you with the predictable question: "What would you do?" This is a difficult question to answer, because the person is generally asking you to make a treatment decision based on only one part of the story (whatever they sent you). This really isn't the way we make informed treatment decisions in real life situations - we take the whole patient into account. When we get an ECG, we like to know if the patient has chest pain, a cardiac history, if they're diaphoretic, if there is pulmonary edema, and so on to infinity. How does this apply to the ventilator?

 

Whenever discussing ventilator strategies, I feel like the discussion is a bit of a cold read whenever the waveforms are not taken into account. The waveforms tell you what the flow, volume, and pressure are doing over time - and they're extremely helpful in managing a patient. I realize that some of you do not have waveforms on your ventilators. If you don't have waveforms on your ventilator, when you do retrievals from outlying hospitals, examining the waveforms on their ventilator will help you set up a care plan for the transport. If you do have waveforms on your ventilator, you've very fortunate - because they can help you set up a precise strategy to fine-tune your settings. 

 

Once you see a picture like this, which is a screenshot of a ventilator someone sent to me, things start to make a lot of sense. Waveforms will often give you the exact reason a vent is acting a certain way. We will return to this example in a later post. 

 

In this blog we are going to look at the basics of waveforms. We are not going to worry about the actual values just yet. Instead, we are going to look at the direction of the waveforms of a negative pressure breath, and a positive pressure breath. 

 

Paw = Airway Pressure. This is a live look at the pressures inside the airway. 

 

Flow = The speed of the the air traveling in and out of the lungs (measured in L/min).

 

Volume = The volume (either liters or millimeters) traveling in and out of the lungs)

 

Negative Pressure Breathing

Green = Inhalation

Red = Exhalation

 

Paw: Notice how the pressure drops during inhalation. This is caused by the chest expanding, which in turn creates a negative space in the chest which allows air to flow in. As the Paw reaches the most negative inflection point, this is the peak negative airway pressure. The pressure returns to baseline when the alveolar pressure reaches atmospheric pressure again (when pressures are equalized, the INflow stops). The pressure then rises as the patient exhales. This pressure compresses the volume in the chest, and as long as the airway is open, the volume will then leave the thoracic cavity. The pressure returns to baseline when the alveolar pressure reaches atmospheric pressure again (when pressures are equalized, the OUTflow stops).

 

Flow: As the patient creates the negative pressure and space in their chest, air starts to flow in. When the flow is at the fastest point (farthest away from baseline) this is the maximum inspiratory flow rate. The same is true when the patient begins to increase the pressure in the chest and compress the volume in the thoracic cavity - the flow reverses air starts to leave the chest. You will notice that the flow starts out very fast and then gets slower. This is because it is very easy for the lungs to empty the larger airways (the first to be cleared) and then it takes a little more time for the smaller airways to clear out their volume, since the resistance is higher flowing through the smaller, more distal airways (all of this assuming healthy lungs). Of all of the waveforms to watch, my opinion is that the flow waveform is usually the most helpful when troubleshooting / changing settings. 

 

Volume: You'll notice the volume waveform is a little different than our other two waveforms. This waveform usually only exists above the line. The volume waveform will rise when volume enters the lungs, and then return to baseline as the volume leaves the lungs. Some ventilators will have the ability to change the display color of the inhaled vs. exhaled volume as I have illustrated in the picture above. 

 

 

Positive Pressure Breathing

Green = Inhalation

Red = Exhalation

 

Paw: The biggest change from a spontaneous, non-ventilated patient, to a ventilator delivered breath, is the change in airway pressures during inhalation and exhalation. We start at a baseline pressure, and then the pressure increases all the way up to the peak inspiratory pressure (PIP / Ppeak). After the ventilator reaches its peak inspiratory pressure, exhalation then begins as pressure lowers all the way back down to the baseline. Notice that the baseline has moved down, since we spend almost all our time in the positive pressure range. 

 

Flow: In this illustration I have not changed the flow pattern, we will address that in subsequent blogs. Different types of breaths will appear differently on the inspiratory flow waveform (square, decelerating, accelerating, and the once pictured is sine). How you set your inspiratory time will also change how quickly the flow goes in. The appearance of the exploratory waveform cannot be directly changed with ventilation, as it is a passive function of the diaphragm and chest. Well... at least that's mostly true. There are things that impact the way the exhalation waveform look, but they are mostly things like patient position, PEEP, expiratory time, and certain disease processes. 

 

Volume: The shape of the volume waveform will reflect the the time of inhalation and exhalation, and how much pressure is exerted during these phases. The volume should also reflect the prescribed dose (volume mode) or how much volume a pressure is delivering (pressure mode). 

 

 

 

 Notice a difference? In this illustration we've added PEEP. 

 

Paw: When we add PEEP we can see that the pressure waveform baseline has moved up from neutral. 

 

Flow: Flow in this illustration has remained unchanged. 

 

Volume: The volume that the ventilator is holding has increased from baseline. This is because the expiratory reserve volume has increased since the addition of PEEP. Your ventilator may or may not read this volume in-between breaths. 

 

 

The Waveform

 

When we change settings on a ventilator, we are constantly re-writing the waveform - and so is the patient when they respond to the changes we make. You can think of the waveform as a constantly evolving storyline shared by you and the patient. As we continue in this series, we'll get into more and more specific examples of changes made on each side. 

 

Stay tuned! 

 

 

 

Original author: Sam Ireland
0
10 October 2019
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