A sternal rub is a technique medical professionals use to quickly assess an unresponsive patient’s level of consciousness. The procedure involves applying a localized, painful stimulus to the sternum to provoke a physical or verbal reaction. The primary goal is to determine if the patient has any neurological response when they cannot be awakened by voice or a gentle shake. This method provides immediate insight into the functionality of the central nervous system, particularly in emergency situations like overdose, trauma, or stroke assessment.
The Neurological Basis for Eliciting a Pain Response
The sternal rub is effective because it targets the highly sensitive periosteum, the dense membrane covering the outer surface of the sternum. This periosteum is richly innervated by sensory nerve fibers, including nociceptors, which detect potentially damaging stimuli. The forceful pressure and friction from the rub cause a mechanical distortion of these nerve endings, leading to the rapid transmission of an intense pain signal.
This signal travels via thinly myelinated A-delta fibers, which transmit sharp, well-localized pain, and unmyelinated C-fibers, which transmit a duller, aching pain. The signal is then relayed through the spinal cord up to the brainstem and higher cortical centers. A response, such as groaning or withdrawal, signifies that the brain’s sensory and motor pathways are still functional enough to process and react to the stimulus. The high concentration of sensory nerves in the periosteum makes it an ideal target for a central, deep pain stimulus.
Proper Technique and Clinical Context
Performing the sternal rub correctly requires a specific technique to maximize the stimulus. The procedure involves making a closed fist and using the knuckles, typically those of the middle fingers, to apply firm downward pressure to the center of the patient’s sternum. The knuckles are then rubbed vigorously against the bone in a circular or back-and-forth motion.
This technique is reserved for specific clinical settings, most commonly in pre-hospital emergency care or hospital rapid response scenarios, after less invasive measures have failed. Before resorting to a painful stimulus, a medical professional must first attempt to rouse the patient using verbal commands and a gentle physical shake. The sternal rub is used when a patient appears to be in a stupor, deeply asleep, or comatose. Focusing the pressure centrally on the sternum ensures the stimulus is strong enough to bypass superficial pain pathways in the skin.
Interpreting Results and Alternative Assessment Methods
A patient’s reaction to the sternal rub is a component of the AVPU scale, a widely used system for classifying neurological status in emergency medicine. AVPU stands for Alert, Verbal, Pain, and Unresponsive. If a patient responds to the sternal rub with a groan, movement, or eye-opening, they are classified as being responsive to “Pain” (P).
This “P” classification suggests the patient has a depressed level of consciousness but retains some brain function. Conversely, if the patient exhibits no response, they are labeled as “Unresponsive” (U), indicating severe neurological compromise. However, the sternal rub is controversial because it can cause bruising or abrasions, leading some professionals to consider it overly aggressive.
Modern medical practice often favors alternative, less invasive central painful stimuli due to these concerns. The trapezial squeeze involves pinching and twisting the trapezius muscle at the base of the neck and is a common alternative. Another technique is supraorbital pressure, which applies firm, upward pressure beneath the bony ridge of the eyebrow. These methods are preferred because they target rich nerve areas with a lower risk of leaving visible skin damage while still providing the necessary central stimulus.