anesthesiology notes

Oxygen:

Not oxygenating:

look at color of skin: cyanosis,

temperature: don't want cold, clammy

stridor - upper airway (inspiratory)

wheezing - lower partial small airway obstruction (starts expiratory can be both)

pO2 <60 begin to get tissue ischemia

CO poisoning - sat will be 100% - have to look at pH!!! pH will be acidotic

people with a history or current treatment with bleomycin should not be given 100% O2 because this can accelerate the development of pulmonary fibrosis

02 tank - E is the size of tank (basic transport tank). all tanks filled to 3000psi - full tank lasts 1000L!!

so for example 750 psi - is a quarter full, which means 250L, at a flow rate of 5L/min you have (250/5) 50 minutes of O2.

say you're in preop and patient has cardiac history, how can you assess the risk of post-op cardiac complications?

you would use the revised cardiac risk index (RCRI).

does the patient have:

1 undergoing a high risk surgery

2. ischemic heart disease

3. chf

4. history of cva

5. insulin dependent diabetes

6. creatinine >2

a point for every yes answer, then how many points?

Risk of post op cardiac complications

0 0.4%

1 0.9%

2 7%

3 or > 11%

a wide pulse pressure in patients w/hypertension has been associated w/increased perioperative adverse events

here's a little advice from an ENT attending:

"save 20% of your income every year starting from residency, you will be a wealthy man"

and more from the ENT

...at some point in your life you realize you have a determinate end, you have to start being real with people, lose the intimidation factor and talk to people irrespective of their station because we all have to meet god someday, talk to the powerful in the same way that you talk to the low.

back to anesthesiology

here are some contraindications to using succinylcholine as a muscle relaxant:

if a person has had a stroke, the death of the upper motor neuron increases the expression of extrajunctional nicotinic acetylecholine receptors at the neuromuscular junction (lower motor neuron) and because succinylcholine is a depolarizing NMJ blocker, the depolarization can cause a hyperkalemia. This hyperkalemia can be severe enough to cause cardiac arrest. If you are using succinylcholine expect the patients K to jump 0.5mEq/L. Succinylcholine also contraindicated in persons w/history of burns, trauma, malignant hyperthermia (succinylcholine is a trigger for this, as is the volatile halothane).

An observation I had about anesthesia:

Anesthesia is interesting in that there is differentiation between sedation, amnesia, anesthesia, analgesia, and paralysis. The definitions being:

Sedation: a general lack of awareness, but not necessarily loss of consciousness or loss of explicit or episodic memory memory

Amnesia: the loss of memory

Anesthesia: the loss of consciousness or feeling or awareness but NOT the loss of pain

Analgesia: the loss of pain.

Paralysis: loss of voluntary (and sometimes involuntary) muscle function

So now this is where it gets interesting, if you are brought under general anesthesia with an intravenous drug, propofol, you will loss consciousness and possibly your memory of any new stimulus the occurs while under the influence of this agent. And then if you are cut with a scalpel blade while under propofol anesthesia, although you are unconscious, your sympathetic nervous system will be greatly activated. Your heart rate and blood pressure will go up in response the destruction of your tissues. And although you are not aware of it, you body will be experiencing the pain of the scalpel. That is why in addition to anesthesia a patient is given opioids (pain-killers).

Once pain-killers are in the system the sympathetic response to the scalpel is blunted, and even though the body is subjected to the trauma, it can be said the patient feels no pain. My question is, how does the experience of pain differ if one has no episodic memory of the pain or at the very least did not consciously experience the pain? Its an interesting distinction that anesthesiologists make between anesthesia and analgesia. What complicates matters is that there exists evidence that although one is under general anesthesia there is some baseline awareness. Evidence for this conclusion comes from experiments where patients are read material while under anesthesia and then given free association exams post-operatively. The central finding is that those who were read to under under anesthesia free associate with content from the literature they were read, in one example when prompted with "Friday" the the free association was Robinson Crusoe for several patients to whom this work was read none for controls. So what is going on here with general anesthesia? Loss of consciousness does not completely erase an experience and that learning does take place. An interesting (and probably unethical) study would be to see if Pavlovian classical conditioning exist in unconscious humans. Essentially you attempt Pavlovian conditioning while under general anesthesia (probably using nociception) and then see if this effect persists when the stimulus is applied to the same person now conscious, it would provide evidence for the idea that conscious awareness is just the "tip of the iceberg" from the perspective of cognitive functioning.