Hjertestansen krever hjerte-lungeredning.

Hjertestansen is the definite singular form: the cardiac arrest / the heart stoppage.

• en hjertestans = a cardiac arrest
• hjertestansen = the cardiac arrest

In Norwegian, the definite article is often added as an ending to the noun instead of using a separate word like the in English.

So:

• hjertestans = the basic dictionary form
• hjertestansen = a specific or contextually understood case

Krever means requires, demands, or calls for.

The verb is å kreve = to require / to demand.

In this sentence, it means that cardiac arrest is a situation that requires CPR.

A few forms:

• å kreve = to require
• krever = requires / is requiring
• krevde = required
• har krevd = has required

Because hjerte-lungeredning is being used in a general, uncountable sense, like CPR in English.

The sentence is talking about the treatment in general, not a specific instance of it.

Compare:

• Hjertestansen krever hjerte-lungeredning.
  = The cardiac arrest requires CPR.
• Hjertestansen krever den hjerte-lungeredningen vi lærte.
  = The cardiac arrest requires the CPR technique we learned.

So no article is needed here.

Norwegian usually writes compound nouns as one unit, and hyphens are often used when two parts are joined in a coordinated way.

Here:

• hjerte = heart
• lunge = lung
• redning = rescue / resuscitation

So hjerte-lungeredning literally means something like heart-lung resuscitation.

The hyphen helps show that hjerte and lunge belong together as a pair modifying redning.

This term is the Norwegian word for CPR. You may also see the abbreviation HLR.

Yes. This is standard Norwegian main-clause word order:

Hjertestansen + krever + hjerte-lungeredning
subject + verb + object

That is very similar to basic English word order: The cardiac arrest + requires + CPR

Norwegian main clauses normally follow the verb-second rule, and here the subject comes first, so the finite verb comes right after it.

A useful learner-friendly approximation is:

YER-teh-stahn-sen

A few pronunciation notes:

• hj at the beginning is usually pronounced like y in yes
• jertet sounds roughly like yer-te
• stansen has a clear n sound before the final -en

So the beginning hjerte- is not pronounced with a strong English h sound.

Yes. Norwegian uses compound words very often.

hjertestans is made from:

• hjerte = heart
• stans = stop / stoppage

So the literal idea is heart stoppage.

This is very common in Norwegian. English often uses separate words where Norwegian prefers compounds.

Hjertestans is a common-gender noun in Bokmål, so you normally get:

• en hjertestans = a cardiac arrest
• hjertestansen = the cardiac arrest

That -en ending is the normal definite singular ending for many common-gender nouns.

Sometimes, yes, but krever is better here.

• krever = requires; sounds more formal and precise
• trenger = needs; often sounds a bit more everyday or personal

In a medical or instructional sentence, krever is very natural because it expresses necessity clearly.

So:

• Hjertestansen krever hjerte-lungeredning. = very suitable
• Hjertestansen trenger hjerte-lungeredning. = understandable, but less idiomatic in this context

Yes. A very common more general version would be:

Hjertestans krever hjerte-lungeredning.

That means Cardiac arrest requires CPR in a general sense.

The version with hjertestansen sounds more like a specific case:

• Hjertestansen krever hjerte-lungeredning. = The cardiac arrest requires CPR.
• Hjertestans krever hjerte-lungeredning. = Cardiac arrest requires CPR.

Both are grammatical; the difference is mainly specific versus general.