chemistry

Post-cardiac arrest syndrome

Post-cardiac arrest syndrome is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Post-cardiac arrest syndrome rather than just read about it. In short: Post-cardiac arrest syndrome (PCAS) is an inflammatory state of pathophysiology that can occur after a patient is resuscitated from a cardiac arrest. While in a state of cardiac arrest, the body experiences a unique state of global ischemia.

Key takeaways

Post-cardiac arrest syndrome belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Post-cardiac arrest syndrome to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Post-cardiac arrest syndrome from memory before moving on to harder problems.

Reference excerpt

Post-cardiac arrest syndrome (PCAS) is an inflammatory state of pathophysiology that can occur after a patient is resuscitated from a cardiac arrest. While in a state of cardiac arrest, the body experiences a unique state of global ischemia. This ischemia results in the accumulation of metabolic waste which instigate the production of inflammatory mediators. If return of spontaneous circulation (ROSC) is achieved after CPR, then circulation resumes, resulting in global reperfusion and the subsequent distribution of the ischemia products throughout the body. While PCAS has a unique cause and consequences, it can ultimately be thought of as type of global ischemia-reperfusion injury. The damage, and therefore prognosis, of PCAS generally depends on the length of the patient's ischemic period; the severity of PCAS is not uniform across different patients.

Causes and mechanisms Before cardiac arrest, the body is in a state of homeostasis. Arterial blood circulates appropriately through the body, supplying oxygen to tissues while the venous blood collects metabolic waste products to be utilized elsewhere and/or eliminated from the body. However, during cardiac arrest, the body is in circulatory and pulmonary arrest. Oxygen is no longer being ventilated by the lungs, and blood ceases to circulate throughout the body. As a result, all tissues in the body start to enter a state of ischemia. In this state, metabolic waste products, such as lactic acid and carbon dioxide, begin to accumulate as there is no circulation to move these products to the appropriate organs. This state of ischemia will continue until ROSC is achieved through CPR, at which time, blood starts to be reperfused throughout the body. This reperfusion results in inflammatory injury through three overlapping mechanisms. Some complimentary combination of, first, mitochondrial damage and, second, endothelial activation, causes a release of reactive oxygen species (ROS), which initiates and/or exacerbates a pathophysiological inflammatory response. Third, reperfusion initiates an immune, inflammatory response resulting in the circulation of pro-inflammatory cytokines such as TNFα, IL-6 and IL-8 as well as complement activation (such as TCC and C3bc). Unlike other causes of ischemia-reperfusion injury, such as organ transplants, PCAS results from global ischemia-reperfusion and subsequently has global organ damage.

Signs and symptoms The severity of PCAS is highly dependent on many variables including: the underlying cause of the arrest, the length of the ischemic period, the quality of CPR received, and a patient's physiologic reserve. However, organs generally respond to an ischemic period in predictable ways and therefore PCAS has an average presentation. The symptoms of PCAS are related to the effect of ischemia-reperfusion injury on individual systems, though there is significant co-morbidity between all organs' responses.

Brain Being highly metabolic with low blood reserves, the brain is the most sensitive organ to ischemia. As a result, any amount of brain ischemia, especially when it is prolonged in cases of cardiac arrest, typically results in brain injury. Increasingly severe injury can lead to long term consequences such as cognitive dysfunction, persistent vegetative state and finally brain death. The brain sustains irreversible injury after about 20 minutes of ischemia. Even after blood flow is restored to the brain, patients can experience hours-days of hypotension, hypoxemia, impaired cerebrovascular autoregulation, brain edema, fever, hyperglycemia and/or seizures which further insult brain tissue. Diagnosis of brain injury involves neurological examination, EEG, brain imaging and/or biomarker evaluation (such as S100B and NSE). For out-of-hospital cardiac arrest, brain injury is the cause of death in most patients who undergo ROSC but ultimately die.

Heart After the brain, the heart is the second most sensitive organ to ischemia. If the cause of the cardiac arrest was fundamentally a coronary pathology, then the consequences to the heart may include myocardial infarction complications. However, if the fundamental cause was non-coronary, then the heart becomes ischemic as a consequence, not a cause, of the arrest. In this case, PCAS very frequently presents with myocardial dysfunction in the first minute-hours post-ROSC. This myocardial dysfunction may present as prolonged cardiogenic shock, highly variable blood pressures, reduced cardiac output and/or dysrhythmias. PCAS myocardial dysfunction seems to start almost immediately after ROSC. Unlike brain tissue, evidence suggests that the myocardial injury is generally transient and can mostly recover within 72 hours, though full recovery may take months.

Lungs While the lungs are generally oxygenated during the ischemic period of arrest, they are still susceptible to ischemic damage. While ischemia is not the mechanism of injury, evidence suggests that the lack of perfusion through the pulmonary vasculature during an arrest reduces the alveolar–arterial gradient which creates dead space. The oxygen accumulation in the alveoli encourages ROS production which then leads to pulmonary damage. This pulmonary-specific damage, together with the systemic inflammation, causes acute respiratory distress syndrome in about 50% of ROSC patients who survive for at least 48 hours. Lung complications, such as pulmonary contusion and pulmonary edema, may result from other aspects of PCAS such as CPR and left ventricular dysfunction, respectively. Finally, pneumonia is a common pulmonary complication due to multifactoral mechanisms including: loss of airway protection, aspiration, emergency intubation, and mechanical ventilation.

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Post-cardiac arrest syndrome

Start with the simplest possible case. Write down what Post-cardiac arrest syndrome claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Post-cardiac arrest syndrome before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Post-cardiac arrest syndrome ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Post-cardiac arrest syndrome

In research: Post-cardiac arrest syndrome appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Post-cardiac arrest syndrome in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Post-cardiac arrest syndrome is common in secondary-school and first-year university syllabi. It links to neighbouring topics Ischemia, Syndromes affecting the heart, so understanding it makes those chapters shorter.
In everyday life: Look for Post-cardiac arrest syndrome outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “Post-cardiac arrest syndrome” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Post-cardiac arrest syndrome in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Post-cardiac arrest syndrome means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Post-cardiac arrest syndrome out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Post-cardiac arrest syndrome in simple terms?

Why does Post-cardiac arrest syndrome matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Post-cardiac arrest syndrome?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Post-cardiac arrest syndrome.