Invasive procedures require informed consent; however, procedures like insertion of a central line in the ICU may be covered under blanket consent.

Generally speaking, all invasive procedures require informed consent and those which are considered routine ICU procedures, e.g. central line insertion, may be covered by a blanket consent, which covers almost everything a doctor or hospital might do without mentioning anything specific. 

Blanket consent is obtained from the patient or surrogate at the time of admission in hospital ICU. It is the responsibility of the individual or institution to establish the guidelines to define where formally written informed consent will be required. (JAMA. 2003;289(15):1963-8).