The scenario you describe is discussed in the Medicare Carrier's Manual, Chapter 12, Section 30.6.12.E.4. on page 63 at
http://www.cms.gov/manuals/downloads/clm104c12.pdf
4. Family Counseling/Discussions
Critical care CPT codes 99291 and 99292 include pre and post service work. Routine daily updates or reports to family members and or surrogates are considered part of this service. However, time involved with family members or other surrogate decision makers, whether to obtain a history or to discuss treatment options (as described in CPT), may be counted toward critical care time when these specific criteria are met:
a) The patient is unable or incompetent to participate in giving a history and/or making treatment decisions, and
b) The discussion is necessary for determining treatment decisions.
For family discussions, the physician should document:
a. The patient is unable or incompetent to participate in giving history and/or making treatment decisions
b. The necessity to have the discussion (e.g., "no other source was available to obtain a history" or "because the patient was deteriorating so rapidly I needed to immediately discuss treatment options with the family",
c. Medically necessary treatment decisions for which the discussion was needed, and
d. A summary in the medical record that supports the medical necessity of the discussion
All other family discussions, no matter how lengthy, may not be additionally counted towards critical care. Telephone calls to family members and or surrogate decision-makers may be counted towards critical care time, but only if they meet the same criteria as described in the aforementioned paragraph.