An injury to the brain can be severe enough to cause brain death, but establishing brain death requires a number of tests. One type of test is called the oculovestibular reflex test or, more commonly, the ice water caloric test. This same test can also be used to assess for damage to the nerves in the ear and is then called the caloric stimulation test. When used as a test to determine brain death, the testing is the same for adults as for children, but there is a degree of difficulty interpreting results with newborns.
Ice Water Caloric Testing
Brain death can be the result of a number of conditions or diseases, but the most common is a critical brain injury. Injuries can occur from motor vehicle accidents, suffocation, near drowning, SIDS, brain infections, and complications of other illnesses and trauma. When brain death is present, the normal eye movement in response to ice water irrigation in the ear canal is absent. Both ears are irrigated at separate time intervals and the eyes are observed for movement for one minute.
Caloric stimulation tests the auditory or acoustic nerve in the ears. Your hearing and the ability to maintain balance relies on an intact and functioning auditory nerve. The test uses cold and warm water to assess the response of the auditory nerve to changes in water temperature. Initially, the ears are checked to ensure that the eardrum is normal and to determine if the medical history includes a previous perforation. Only one ear is tested, an interval of five minutes in between, then the other is tested. If the test fails to evoke the appropriate eye movements, then ice water might be used to repeat the test.
With caloric stimulation, the test requires avoiding caffeine, certain medications and alcohol for 24 hours before the test. Consult your physician for specific restrictions. Serious dizziness and nausea can occur with the test, but vomiting is rare. No specific restrictions apply to the test when determining brain death. Both testing situations require that the ear canals be intact. The appropriate response from the eyes is to look away from the tested ear with cold water or ice water and to look toward the tested ear with warm water.
Federal and State Requirements
Generally, it is acceptable for doctors to decide brain death, but the state's legal requirements, as well as the facility's policies, procedures and guidelines, may vary. Some facilities and states might require physicians with experience in specific fields of medicine, such as neurology, to determine brain death. Federal and state laws stipulate that physicians notify institutions that specialize in organ donations immediately after brain death is decided and pronounced.
- "Critical Care Nurse"; Pediatric Care; Brain Death in Infants and Children; Stephen Ashwal and Teresa Serna-Fonseca; April 2006
- "Neurology"; Evidence-based Guideline Update: Determining Brain Death in Adults; Eelco F. M. Wijdicks, et al.: June 8, 2010
- University of Maryland Medical Center: Caloric Stimulation
- Alameda County Medical Center/Highland General Hospital: Trauma Service -- Brain Death Determination
- Medline Plus: Caloric Stimulation