A "5150" is the California code for a 72 hour psychiatric evaluation hold, but the term 5150 is often used to describe any psych patient transported by EMS.
"Section 5150 is a section of the California Welfare and Institutions Code which authorizes a qualified officer or clinician to involuntarily confine a person suspected to have a mental disorder that makes him or her a danger to themselves, a danger to others, and/or gravely disabled."
4 points and 2 points are restraint arrangements. 4 points is legs and arms restrained, 2 points are usually just arms. Many agencies that transport psychiatric patients that have the potential for violent behavior have a soft restraint system installed on the gurney.
Always know your protocols and company policy regarding restraints before using them, and be kind to psych patients. They're often treated with derision and ridicule.