The brain perceives pain through the nociception system, which prompts increased activity in the autonomic nervous system (ANS). In turn, the ANS activates the sympathetic nervous system (SNS), creating a stress response in the body that includes increased respiration, blood pressure and heart rate. In sick patients, a strong stress response can cause serious injury. Anesthesiologists try to minimize the stress response during surgery by giving patients drugs that block nociception. Finding the appropriate balance can be challenging — too much anesthesia can make the patient very ill, while too little anesthesia increases the stress response. Anesthesiologists currently rely on a patient's vital signs — pulse rate, blood pressure, temperature, and respiratory rate — to estimate the level of ANS activation and determine appropriate drug dosage. Unfortunately, these vital signs alone are not enough to estimate ANS activity, because they are often affected by other factors. Christopher Brouse is developing a nociception monitor that automatically determines the level of activation of a patient's ANS. It will use computer algorithms that analyze very small, fast changes in the patient's heart rate, called heart rate variability (HRV). Previous research has shown that HRV responds to ANS activation much more predictably than other vital signs do; therefore, HRV can provide a better estimate. With the data gathered from his first pilot pain study, Brouse is now developing and fine tuning a pain index that correlates with ANS activity. By accurately monitoring subtle vital signs, the nociception monitor has the potential to increase patient safety during and after surgery and reduce recovery times. It could also be used for patients recovering from surgery to gauge their pain and respond with the appropriate amount of drugs.