Final answer:
In a patient with extreme hypothermia who appears to be in cardiac arrest, the pulse should be assessed for 30 to 45 seconds.
Step-by-step explanation:
In a patient with extreme hypothermia who appears to be in cardiac arrest, you should assess the pulse for 30 to 45 seconds. When a person is experiencing extreme hypothermia, their body temperature drops significantly, which can cause their heart rate and blood flow to decrease. It is important to assess the pulse for a longer duration of time to ensure accurate assessment of the patient's condition.