Tex. Health and Safety Code § 166.160

(a) An agent is not subject to criminal or civil liability for a health care decision if the decision is made in good faith under the terms of the medical power of attorney and the provisions of this subchapter.

(b) An attending physician, health or residential care provider, or a person acting as an agent for or under the physician's or provider's control is not subject to criminal or civil liability and has not engaged in unprofessional conduct for an act or omission if the act or omission:

(1) is done in good faith under the terms of the medical power of attorney, the directives of the agent, and the provisions of this subchapter; and

(2) does not constitute a failure to exercise reasonable care in the provision of health care services.

(c) The standard of care that the attending physician, health or residential care provider, or person acting as an agent for or under the physician's or provider's control shall exercise under Subsection (b) is that degree of care that an attending physician, health or residential care provider, or person acting as an agent for or under the physician's or provider's control, as applicable, of ordinary prudence and skill would have exercised under the same or similar circumstances in the same or similar community.

(d) An attending physician, health or residential care provider, or person acting as an agent for or under the physician's or provider's control has not engaged in unprofessional conduct for:

(1) failure to act as required by the directive of an agent or a medical power of attorney if the physician, provider, or person was not provided with a copy of the medical power of attorney or had no knowledge of a directive; or

(2) acting as required by an agent's directive if the medical power of attorney has expired or been revoked but the physician, provider, or person does not have knowledge of the expiration or revocation.