Critical Care Nursing

104 flashcards by MentisLibrary

ICU practice for new and aspiring critical care nurses: hemodynamic monitoring, mechanical ventilation, shock and sepsis, ACLS rhythms, neurocritical care, sedation and delirium, blood gases, and line safety.

How is mean arterial pressure calculated and why does it matter?
It is roughly the systolic pressure plus twice the diastolic, divided by three, and it estimates the pressure actually perfusing the organs.
What does central venous pressure reflect?
The filling pressure on the right side of the heart, used as one rough indicator of volume status and right heart function.
What does the pulmonary artery wedge pressure estimate?
Left atrial pressure, and therefore left ventricular preload.
What are normal cardiac output and cardiac index?
Cardiac output is the volume the heart ejects per minute, and cardiac index is that output adjusted for body surface area.
What does systemic vascular resistance tell you about the type of shock?
It is high in cardiogenic and hypovolemic shock as the body compensates by vasoconstricting, and low in distributive shock such as sepsis and anaphylaxis.
Define preload, afterload and contractility.
Preload is the stretch on the ventricle at the end of filling, afterload is the resistance the ventricle must overcome to eject, and contractility is the intrinsic force of the squeeze.
Where is an arterial line transducer leveled and zeroed?
At the phlebostatic axis, the fourth intercostal space at the midaxillary line, with the system zeroed to atmospheric pressure.
What causes a damped arterial waveform?
A clot or air bubble in the tubing, a kinked catheter, the tip resting against the vessel wall, loose connections, or a low pressure bag.
Why is collateral circulation checked before radial artery cannulation?
To confirm the ulnar artery can perfuse the hand if the radial artery becomes occluded by the catheter.
How does a passive leg raise assess fluid responsiveness?
Raising the legs shifts venous blood centrally as a reversible internal fluid bolus; a rise in stroke volume or cardiac output suggests the patient will respond to fluid.
What does a low central venous oxygen saturation indicate?
That tissues are extracting more oxygen than usual, which points to inadequate delivery from low cardiac output, low hemoglobin, low arterial saturation, or high demand.
Which vasopressor is generally first line in septic shock?
Norepinephrine, because it raises vascular tone with less tachycardia than other agents.
What is the first action if a vasopressor extravasates?
Stop the infusion, leave the catheter in place to aspirate, notify the provider, and follow the protocol for phentolamine infiltration to reverse the vasoconstriction.
Dobutamine vs norepinephrine
Dobutamine is an inotrope that increases contractility and can lower blood pressure through vasodilation; norepinephrine is a vasopressor that raises pressure through vasoconstriction.
Assist control vs synchronized intermittent mandatory ventilation vs pressure support
Assist control delivers a full set breath for every effort, SIMV delivers set breaths and allows unsupported spontaneous breaths between them, and pressure support assists only the patient's own breaths with no set rate.
What tidal volume is used for lung protective ventilation?
About 6 milliliters per kilogram of predicted body weight, calculated from height and sex rather than actual weight.
What is the target plateau pressure and why?
Plateau pressure reflects alveolar pressure, and keeping it low reduces overdistension injury.
What does positive end expiratory pressure accomplish, and what are its risks?
It holds alveoli open at the end of exhalation to improve oxygenation and reduce repeated collapse injury; high levels can reduce venous return and cause barotrauma.
What causes a high pressure ventilator alarm?
Increased resistance or decreased compliance: secretions, biting or a kinked tube, bronchospasm, pneumothorax, pulmonary edema, or the patient coughing or fighting the ventilator.
What causes a low pressure or low volume ventilator alarm?
A leak or a disconnection: circuit tubing off, a cuff leak or a ruptured cuff, or an extubation.
What does the DOPE mnemonic cover for sudden deterioration on a ventilator?
Displacement of the tube, Obstruction by secretions or biting, Pneumothorax, and Equipment failure.
Which measures prevent ventilator associated pneumonia?
Elevate the head of the bed, provide regular oral care, interrupt sedation and assess readiness to wean daily, use subglottic secretion drainage when available, and prevent circuit contamination.
How is readiness to wean from mechanical ventilation judged?
The underlying cause is improving, oxygenation is adequate on modest support, the patient is hemodynamically stable, awake enough to protect the airway, and able to pass a spontaneous breathing trial.
What is post-extubation stridor and how is it managed?
High pitched inspiratory sound from laryngeal edema after extubation, managed with humidified oxygen, ordered corticosteroids or nebulized epinephrine, and preparation for reintubation.
Why is prone positioning used in severe acute respiratory distress syndrome?
It improves ventilation and perfusion matching and recruits dorsal lung, improving oxygenation and survival in moderate to severe cases.
What is auto-PEEP or breath stacking?
Air trapped at the end of exhalation because the next breath begins before exhalation is complete, which raises intrathoracic pressure and can drop blood pressure.
What is the most reliable confirmation of endotracheal tube placement?
Waveform capnography showing sustained exhaled carbon dioxide, together with bilateral breath sounds, chest rise and a confirming chest film for depth.
Why does end tidal carbon dioxide fall abruptly during resuscitation or ventilation?
Because pulmonary blood flow has dropped, from cardiac arrest, a pulmonary embolism, severe hypotension, or a disconnected circuit.
How is oxygenation failure quantified in acute respiratory distress syndrome?
By the ratio of arterial oxygen tension to the fraction of inspired oxygen, measured with a minimum level of positive end expiratory pressure.
Name the four broad categories of shock.
Hypovolemic from volume loss, cardiogenic from pump failure, distributive from vasodilation such as septic, anaphylactic and neurogenic shock, and obstructive from a mechanical block to flow.