Lecture Notes
This will build on our prior lecture on shortness of breath
The first thing you need to do when you get called to a patient with shortness of breath is build a critical differential diagnosis.
Critical Differential for SOB:
- Pneumonia
- Pneumothorax
- Pulmonary Embolism
- Asthma/COPD
- CHF Exacerbation
In this case we will assume that the patient is having a CHF Exacerbation. This could have been determined by obtaining a history consisting of Dyspnea on Exertion and PND. On physical exam the patient may have had an elevated JVD, crackles in the lungs and lower extremity edema. Maybe you used your ultrasound to confirm that your patient had a poor EF and a dilated IVC.
After constructing your critical differential diagnosis, the next step is to walk over to your patient and determine what degree of respiratory distress he/she is in.
The following bits of information can be used to determine what degree of respiratory distress your patient is in:
- RR
- Sao2
- Are there signs of retractions
- How many words is your patient able to speak in a sentence
Remember that respiratory distress is a spectrum. So the patient may not fall into a hard category but may instead be in mild to moderate or moderate to severe respiratory distress.
The reason why we spend so much time talking about what degree of respiratory distress our patient is in, is because where they are on this spectrum will guide what our initial management strategy will be
So let’s go over a little bit of physiology
The Frank Starling Curve demonstrates EF as a function of preload. When the preload is optimal there will be maximal actin and myosin overlap. This will lead to maximal EF. When the preload is in excess the actin and myosin are no longer able to overlap and as a result EF will be reduced. When there is decreased EF, blood does not adequately get pumped to the kidneys. As a result the kidneys believe they are dry and activate the RAS system. This leads to further fluid retention and worsening preleoad.
To combat this downward spiral, we can start by attacking the preload. By decreasing preload we can get the patient back to the optimal point of the Frank Starling Curve. Increased EF -> Increased kidney perfusion -> deactivation of the RAS system -> increased diuresis->further preload reduction. Two medications we use to decrease preload are Lasix and Nitroglycerine. Administration of Lasix results in diuresis and elimination of excess fluid. Nitroglycerine works by causing venodilatation and in higher intravenous doses has the added benefit of being an afterload reducer.
One caveat: You would not want to use these interventions on a patient who is preload dependent. I.e pulmonary hypertension or severe aortic stenosis
Time for the fun stuff
Now that we have reviewed the physiology let's get to the actual management of these patients. The management strategy of a CHF Exacerbation patient is based on the degree of respiratory distress the patient is in.
Mild respiratory distress:
Lasix
Moderate respiratory distress:
Lasix
Nitro
Moderate to Severe Respiratory Distress:
Lasix
Nitro
Start Bipap
Severe respiratory distress:
Lasix gtt
Nitro gtt
Intubate patient
Pressor i.e norepinephrine
Again, figuring out what degree of respiratory distress your patient is in is so important because it will guide your initial management.
While you are resuscitating your patient you will want to simultaneously order labs and imaging studies.
Consider ordering the following labs
- CBC - to make sure the patient is not anemic
- BMP - to see if there are electrolyte abnormalities or acute renal injury from cardiorenal syndrome.
- EKG - to see if the patient is in an unstable rhythm or having an acute MI
- Troponin - This is important in CHF exacerbation because when elevated represents a higher mortality
- +/-D Dimer
Consider ordering the following Imaging study:
- Chest Xray to ensure that the patient does not have pneumonia or pneumothorax
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