If nurses work extended shifts does this compromise patient safety?

It may: Either physician or a nurse who work extended shifts there is always a possibility that patient care can be compromised. Lack of sleep, strenuous work, tiredness will result in inattention, frustration - all of these culminate in poor patient care.

Of course: The human body does need rest in order to function properly, being too tired can result in mistakes.

Potentially: Exhaustion can impair performance.