The Circulation, Motion, Sensation (CMS) assessment is a rapid, non-invasive evaluation used in medical settings to determine the neurological and vascular health of a patient’s extremity. This neurovascular check is performed primarily on the limbs, assessing if blood flow and nerve function are intact, particularly in the fingers and toes. The CMS test provides healthcare professionals with a quick snapshot of the peripheral perfusion and nerve status distal to a potential injury or surgical site. It serves as a fundamental screening tool in acute care and trauma situations.
The Core Purpose of the CMS Assessment
The primary reason for performing a CMS assessment is to monitor for neurovascular compromise, which occurs when blood vessels or nerves are damaged or compressed. This assessment is often conducted repeatedly following trauma, such as a major fracture, or after orthopedic procedures like the application of a cast or surgical fixation. Its repeatability makes it an effective early warning system for developing complications.
The test is used to screen for compartment syndrome, where swelling within a closed muscle compartment cuts off blood supply and nerve function. Since the fascia surrounding muscle groups does not stretch easily, increased pressure from internal swelling can rapidly compromise circulation and nerve viability. Prompt detection of changes in circulation, motion, or sensation is necessary for saving the function of the limb.
The CMS assessment is a standard part of the secondary evaluation for any patient presenting with a limb injury or who has undergone a procedure that may impact blood flow. Clinicians establish a baseline reading for the injured limb and compare it to the unaffected side to quickly identify subtle deteriorations. This systematic comparison ensures that any loss of function is recognized immediately, guiding the need for urgent intervention to restore perfusion and nerve integrity.
Step-by-Step: Checking Circulation, Motion, and Sensation
Circulation
The circulation component of the CMS check focuses on assessing the arterial blood supply to the extremity, evaluating color, temperature, and capillary refill time. The skin and nail bed color should be pink or consistent with the patient’s normal tone and is compared to the unaffected limb. Pallor (paleness) or cyanosis (a bluish tint) suggests poor oxygenation or reduced blood flow.
Temperature is evaluated by gently touching the affected limb and comparing its warmth to the opposite extremity. A cool limb may indicate compromised circulation, while a significantly warmer limb could suggest inflammation or infection. The most specific test for peripheral circulation is the capillary refill time, which measures the speed at which blood returns to the tiny vessels under the nail bed.
To perform the capillary refill test, the assessor applies firm pressure to a fingernail or toenail until the area blanches, or turns white. Upon releasing the pressure, the area should return to its normal pink color within three seconds or less. A prolonged refill time suggests a delay in the arterial flow to the distal tissues. Peripheral pulses, such as the radial or dorsalis pedis pulse, are also checked and graded for strength and symmetry between the two limbs.
Motion
The motion assessment evaluates the motor function of the nerves supplying the muscles in the extremity. The assessor first asks the patient to perform active movements, such as wiggling their fingers or toes or making a fist. The ability to voluntarily move the distal digits demonstrates intact nerve pathways and muscle function.
If active movement is painful or impossible, the assessor may attempt passive movement, gently moving the patient’s fingers or toes to check for joint stiffness or pain. Resistance testing is also performed, where the patient is asked to push or pull against the assessor’s hand, such as pushing down with the foot. Any weakness or inability to move the digits is documented as a deficit in the motor component.
Sensation
The sensation check determines the integrity of the sensory nerves, which convey feelings like touch, pain, and temperature. The assessor asks the patient to close their eyes and identify which finger or toe is being touched to check for light touch discrimination. This ensures the patient is actually feeling the touch, not just seeing it.
A more detailed check involves testing the patient’s ability to distinguish between sharp and dull sensations using a tool like a safety pin or a cotton swab. The assessor touches the patient in various areas of the extremity and asks them to describe what they feel. The patient is also asked directly if they are experiencing abnormal sensations, such as numbness, tingling, or a pins-and-needles feeling (paresthesia).
Interpreting Abnormal Results
An abnormal CMS assessment is a serious finding that signals a developing medical emergency requiring immediate action. If circulation is compromised, findings include a pale or dusky skin color, a cool temperature compared to the unaffected limb, and a significantly delayed capillary refill time. The absence or marked weakness of a distal pulse is a late sign of severe arterial flow obstruction.
Abnormal motion findings include an inability to actively move the fingers or toes (paralysis) or extreme pain upon movement. This loss of motor function suggests significant nerve compression or damage. An inability to feel light touch or differentiate between sharp and dull stimuli indicates sensory nerve dysfunction.
Any deviation from the patient’s baseline CMS status must be promptly escalated to the treating physician or surgeon. For instance, severe, disproportionate pain not relieved by standard medication, coupled with an abnormal CMS check, strongly suggests compartment syndrome. Immediate intervention involves notifying the medical team, removing or loosening restrictive dressings or casts, and elevating the limb no higher than the heart. Failure to quickly address severe neurovascular compromise can lead to permanent nerve damage, muscle death, and potentially limb amputation.