Anesthesia

CHAPTER 6
Anesthesia

Patty T. Liu

Test Taking Tips

• Remember to review lidocaine toxicity, especially the signs and symptoms and the maximum dose that can be given.

• Know the advantages and disadvantages of using an epidural versus a PCA for postoperative pain control.

What is the optimal distance above the carina for an endotracheal tube (ETT)?

2 cm above the carina

What are the steps of rapid sequence induction?

Oxygenation and short-acting induction agent → muscle relaxant → cricoid pressure → intubation → inhalational anesthetic

What is the most commonly used technique for induction of general anesthesia in children?

Inhalational

What are the steps that both the surgeon and anesthesiologist should take during an airway fire?

Stop all gas and oxygen flow → extinguish fire with water/saline → remove ET tube and any foreign body in airway → perform mask ventilation until patient is reintubated → perform bronchoscopy to assess extent of airway damage.

What factors affect the accuracy of pulse oximetry?

Decreased reading—intense environmental lighting, motion, methylene blue dye, hypothermia, low cardiac output, hypotension, peripheral edema, nail polish

Increased reading—bilirubin, carbon monoxide

Define minimum alveolar concentration (MAC):

The smallest concentration of gas at which 50% of patients will not move to painful stimuli such as incision

Relate lipid solubility, speed of induction, and potency for an inhalational agent with a low MAC:

Low MAC means that the agent is more lipid-soluble and more potent but slower speed of induction

What inhalational agent has the fastest speed of induction, high minimal alveolar concentration, and low potency?

Nitrous oxide (NO₂)

Name contraindications to the use of nitrous oxide:

Middle ear occlusion, pneumothorax, small bowel obstruction, and any other instance where there is an air-filled body pocket

Which inhalational agent can cause eosinophilia, fever, increased liver function tests, and jaundice and is associated with the highest degree of cardiac depression and arrhythmias?

Halothane

Which inhalational agent has a pleasant smell and is ideal for mask induction in children?

Sevoflurane

What induction agent should not be used in patients with an egg allergy?

Propofol

What induction agent is contraindicated in head injury?

Ketamine

Which induction agent can cause adrenocortical suppression with continuous infusion?

Etomidate

First muscle to be paralyzed after administration of a paralytic? Last muscle?

Face and neck muscles

Diaphragm

First muscle to recover after administration of a paralytic? Last muscle?

Diaphragm

Face and neck muscles

Triggering agents for malignant hyperthermia:

Volatile anesthetics (halothane, enflurane, isoflurane, sevoflurane, desflurane) and depolarizing paralytic succinylcholine

What is the mechanism leading to malignant hyperthermia?

Mutation of the ryanodine receptors located on the sarcoplasmic reticulum resulting in a drastic increase in intracellular calcium levels inducing an uncontrolled increase in skeletal muscle oxidative metabolism

First sign seen with malignant hyperthermia? Other signs?

Increase in end-tidal CO₂

Acidosis, fever, hyperkalemia, rigidity, tachycardia

Treatment for malignant hyperthermia:

First stop offending agent, cooling blankets, dantrolene (10 mg/kg IV), glucose, HCO₃, IV fluids, supportive care

Name the only depolarizing paralytic

Succinylcholine

Use of succinylcholine should be avoided in which patients?

Patients with extensive burns, crush injuries/extensive trauma, eye trauma or glaucoma (raises intraocular pressure), neurologic disorders/injury, spinal cord injury, acute renal failure with increased potassium

How long does succinylcholine last? Metabolized by? Antidote?

<6 minutes, hydrolyzed by plasma cholinesterase (pseudocholinesterase), time

How is cisatracurium metabolized?

Hofmann elimination

How is mivacurium metabolized?

Hydrolyzed by plasma cholinesterase

What is the most common side effect of pancuronium?

Tachycardia (vagolytic effect)

What can be used to reverse nondepolarizing paralytics?

Acetylcholinesterase inhibitors (neostigmine, edrophonium, pyridostigmine)

Mechanism of action of local anesthetics:

Blocks transmission of neural impulses by stabilizing Na channels, thus preventing propagation of action potential