Anesthesia Induction and Emergence Medications

It was my first real day on Anesthesiology. The hours are a little longer than my last rotation, so I am unsure if I will be able to post every day. I learned a lot today but what I really want to retain in my brain is the the procedure of and anesthetic agents used for induction and emergence.  

Anesthesia Induction 

The first part of induction of anesthesia should be pre-oxygenation with 100% oxygen delivered via a face mask. I placed the face mask on my patient and told them to take deep breaths in and out for about 1 min. We watched the pt's O2 sats climb up to 100% and then prepared to intubate the patient. The purpose of the pre-oxygenation step is to maximize the amount of time that can pass after a patient has been anesthetized and before a proper airway is secured because pts may become apneic once they are anesthetized. 

Before you intubate the pt, you need to anesthetize. The most common choices used for IV induction in order of frequency are Propofol, Thiopental, Etomidate, and Ketamine. We used propofol in all of my cases today. How do you know if the patient is properly anesthetized? We check the corneal reflex (CN V1 afferent and CN VII efferent). If the patient didn't have the corneal reflex, we knew that they were properly anesthetized and that we could proceed with the paralytic agent. 

To induced paralysis, administer a neuromuscular blocking agent such as succinylcholine (depolarizing agent) or vecuronium (non depolarizing agent). A twitch monitor is usually used to assess the depth of relaxation, and when the twitch has sufficiently diminished, intubation can be attempted. The resident told me that you will normally have four twitches. 3 twitches mean that 75-80% of the NMJ is blocked, 2 twitches means that 80-85% is blocked, 1 twitch means that 90-95% is blocked and 0 twitches is 100% blocked. I got varying answers on this question, but all of the residents I asked said they like to keep the twitches down to 1-2 and others wanted no twitches at all before they intubated. 

Once the pt is properly paralyzed, you are ready to intubate! I won't write the steps down since it is somewhat technical but I will say that my attending told me that you usually advance (sound?) the tube about 20-22 cm. 

Emergence

The patient's neuromuscular blockade may have slighlty/completely worn off during the procedure or not at all. Acetylcholinesterase inhibitors (neostigmine is the most commonly used) are used to reverse the effects of the blocking agents. They allow more acetylcholine to be available to overcome the neuromuscular blocker effect, but also causing muscarinic stimulation (because, remember that the muscarinic receptors use acetycholine as well). When the muscarinic receptors are activated, the pt will get side effects: bradycardia, diarrhea, lacrimation, salivation and bronchospasm. Thus, you need to administer an antimuscarinic agent as well such as Atropine or Glycopyrrolate (does not cross the BBB) to prevent these unwanted side effects. We used Glycopyrrolate in all of my patients today because it does not cross the BBB and thus, it will not cause as much drowsiness as Atropine. 

Not my most organized post thus far. It was more of a frantic brain dump of information but it will have to do because my day now starts at 4am! Here is to tomorrow and maybe I will get to intubate by myself!