As you may already know, healthy dogs and cats are pretty alert and responsive to their surroundings.  When they become ill, however, their responsiveness is affected to various degrees.  The less response there is, the more serious the condition.  The following is a guideline to assessing responsiveness:

Level of Consciousness               What it Means        Call the Vet?                                     

Alert & responsive to owner           Normal                  No                                       

and outside stimuli; if you 

call him for a treat, he 

responds.

Depressed; response slow          Common to             Yes, next day,                   

to sight or touch stimulation;        many illnesses        if the condition                                     

may be sleepy or reluctant                                        doesn’t resolve                                       

to move.                                                                  w/ first-aid

Disoriented; bumps                   Probably neuro-         Yes, same day           

into objects, stares blindly,        logic or inner ear    

walks w/ unsteady gait or in       involvement

circles, falls to one side.

Stupor; can be aroused             Neurologic or           Yes, immediately              

only by deep pain                      metabolic  problem;           

stimulation (i.e. pinched toes)     serious.

Comatose (unable to wake)       EMERGENCY –       Yes, immediately                         

or having seizures                     severe neurologic 

                                               damage or disruption 

                                               from injury, disease, 

                                               or toxin.

Keep in mind that with an injury, fight or flight can kick in as a first reaction and mask slowed responsiveness.  If you pay attention, though, signs of disorientation may become evident.