Week 3

This week I spent more time with the anesthesiologist during the neurosurgeries. It was quite impressive to learn more about how a patient is monitored and controlled during the surgery. The neurological surgeries are particularly challenging for the anesthesiologist as their usual anesthetic increases brain blood flow and they therefore try to compensate by using more of a different type in combination with a much lower concentration of the usual anesthetic (sorry, forgot to write down the name, but will update next week). Further, the patient has to be completely paralyzed right up until the end of the surgery as their head is fixed in a Mayfield head holder http://www.steel-form.sk/en/02/0103/b/images/52.htm. If the patient was woken up while the head is still in this, he/she could seriously injure themselves with just a slight cough. The paralyzing agent is given separate from the anesthesia and both have to be monitored closely. This means that if the patient were to wake up during the surgery, one would not notice this through any patient movement (every anesthesiologist’s nightmare). While the paralysis can be measured by applying a small electric shock at the wrist and seeing the extent of movement, there is no effective device yet to measure the state of alertness (i.e. how deep the patient is in anesthesia). While they have some idea of a patient’s alertness by monitoring the heart rate and blood pressure (i.e. a patient with a low blood pressure and low heart rate is fast asleep, there is still no device that effectively monitors consciousness. This device would be very helpful as every patient responds differently to the anesthetic and requires different amounts. Finding the minimally required amount is also important as too much anesthetic results in various side effects. One company has tried to create what they refer to as a BIS monitor (Bispectral index http://www.aspectmedical.com/patients/bis/default.mspx). This is attached to the forehead and analyzes a patients ECG from the forehead during the surgery. It runs this data through various algorithms and yields a number from 1-100 which is supposed to represent the patients state of awareness. According to the anesthesiologists I spoke to, it doesn’t work very well though and isn’t of much help to them and thus they don’t use it. If however, one were to develop an effective device like this, chances are the FDA would require it during every surgery. Apparently this was tried with the BIS monitor, but due to its limited effectiveness not followed through. So BME students… if you have any ideas… talk to me and lets get a patent :-).