Critical Care 1 Flashcards
Arterial blood pressure is the product of _________ and ________
Cardiac output and resistance to flow
Cardiac output consists of _______ and _______
Stroke volume and heart rate
Stroke volume is determined by ______, _______, and _______
Preload, afterload, and contractility
MAP = [ _____ + (2 x _____)]/3
SBP ; DBP
Normal MAP is?
70 to 100 mmHg
MAP required for adequate cerebral perfusion?
60 mmHg
What is preload?
Preload can be defined as ventricular end diastolic volume.
Signs of hypoperfusion?
Cold extremities, AMS, decrease in urine output
Why is lactic acid formed during hypoperfusion?
During periods of hypoperfusion, tissue receives less oxygen, and in turn uses anaerobic metabolism. Lactic acid is a byproduct of anaerobic metabolism.
Normal SBP
90 - 140 mmHg
Normal DBP
60 - 90 mmHg
Normal Heart Rate
60 to 80 beats per minute
Normal lactic acid levels
< 1 mmol/L
Normal central venous oxygen saturation (ScvO2)
70% to 75%
Normal oxygen extraction from the blood is about 25% to 30%
How do you determine cardiac output?
Heart Rate x Stroke Volume
What is normal cardiac output?
4 to 7 L/minute
How would you determine a patient’s Cardiac Index?
Cardiac Index is:
Cardiac output / BSA
The four types of shock
1) Distributive or vasodilator
2) Hypovolemic
3) Obstructive (tamponade or PE)
4) Cardiogenic (heart failure)
Indicators of distributive or vasodilatory shock
High cardiac Index early, but shifts to low.
Low central venous pressure (or PCWP) early but then increases to normal or high
Low SVR (systemic vascular resistance)
Patients with distributive shock are generally hyper dynamic (high CI) with vasodilation (low SVR) and increased vascular permeability (“leaky capillaries”), which causes fluid to shift into the interstitial spaces.
Cardiac indicators of hypovolemic shock
Low cardiac Index
Low CVP/PCWP
High SVR (to maintain perfusion)
Cardiac indicators of obstructive shock
Low cardiac Index
Low CVP/PCWP if impaired ejection, or high is it is impaired filling (for example tamponade)
High SVR
Cardiac indicators of cardiogenic shock
Low cardiac Index
High CVP/PCWP
High SVR
Patients with cardiogenic shock have acute heart failure, which causes reflex vasoconstriction secondary to reduced tissue perfusion. This increases blood flow to vital organs but worsens heart function due to increased afterload and decreased excretion of Na+ and water.
Treatment of hypovolemic shock
Basics of treatment include restoring intravascular volume and oxygen carrying capacity (I.e. Volume resuscitation with crystalloids or colloids or using blood products if indicated).
Packed red blood cells can be used if hemoglobin is < 7 g/dL or if they are actively bleeding.
Vasopressor use in hypovolemic shock
Which vasopressors can be helpful, the first concern is volume resuscitation. In fact the adverse effects of vasopressors (I.e. Arrhythmias and ischemia) are greater if patients have not received adequate fluid resuscitation.
I would guess because the doses required to achieve adequate results would be higher due to the continuation of the hypovolemic state.
Treatment of obstructive shock
First and foremost, treatment of the actual obstruction is #1. Fluids and vasopressors can help, but won’t necessarily improve outcomes.
What four measures should be completed within 3 hours of a patient presenting with sepsis or septic shock?
1) Measure lactate level
2) Obtain blood cultures prior to administering antibiotics
3) administer broad spectrum antibiotics
4) administer 30 mL/kg crystalloid for hypotension or lactate 4 mmol/L or greater
A side note: when administering large volumes of crystalloids, it’s better to use solutions closer to extracellular fluid, such as LR or plasmalyte. Chloride rich solutions such as NS or 5% albumin can lead to AKI and metabolic acidosis
What measure should be completed within 6 hours of a patient presenting with sepsis or septic shock with persistent hypotension unresolved with fluids?
Administration of vasopressors to maintain a MAP of 65 mmHg or greater.
Norepinephrine is the initial vasopressor of choice
Generally, vasopressor hierarchy would go:
- Norepinephrine
- Vasopressin (1.8 units/hour)
- Epinephrine
- Dopamine could be used at any time as well, but does have a higher risk of arrhythmias.
- Phenylephrine can also be used at any time, and is preferred in patients with a high risk of cardiogenic side effects due to its reduced risk of arrhythmias and hypotension.
Vasopressor administration (line preference and extravasation management)
Central line preferred due to decreased risk of extravasation and subsequent ischemia.
- If extravasation does occur, phentolamine (a-receptor antagonist) can be used to reduce tissue necrosis.
- Other extravasation management options include nitroglycerin 2% ointment applied q6 hours to the area around the site, or terbutaline subQ to the site
Norepinephrine
- Dose: 0.05 - 1 mcg/kg/min (Legacy dosing)
- Receptor affinity: highest for alpha-1 and beta-1, with no beta-2 or dopamine activity.
- Decreases renal perfusion, increases SVR and BP.
- Can induce tachyarrhythmias and myocardial ischemia.
