Complications Flashcards
What is believed to be the reason for the increased teratogenicity of N2O when compared to other inhaled and intravenous anesthetics?
oxidation of vitamin B12 and inactivation of methionine synthase.
Methionine synthase - methyltetrahydrofolate and homocysteine –> tetrahydrofolate (THF) and methionine.
Without THF and methionine –>reduced thymidine synthesis - essential nucleosides for DNA synthesis, its absence damages the genome and could theoretically induce cancer.
True or false: desflurane can cause an increased risk for infertility.
False
List three risk factors for teratogenesis under anesthesia.
◾The procedure being performed.
◾The proximity of the surgical site to the uterus.
◾The underlying maternal condition that necessitated the surgery
What are the JCAHO limits for environmental exposure to volatile anesthetic agents?
less than 2 ppm for volatile anesthetic when used alone, and less than 0.5 ppm when used with N2O.
What are the two major causes of waste gas contamination in the operating room?
operator issues (e.g. poorly fitting masks, filling anesthetic vaporizers, flushing the circuit)
equipment issues (e.g. punctured hoses, circuit leaks).
During which trimester is a fetus at highest risk for death associated with anesthesia and surgery?
1st
Describe the factors that contribute to trauma associated with airway management.
management of a difficult airway –> commonly multiple attempts at laryngoscopy
insertion of adjunctive airway devices - oropharyngeal or nasopharyngeal airways
Inexperience and poor technique increase the risk of airway complications.
Name two nerves that can be injured during bag mask ventilation.
mandibular branch of the facial nerve –> transient facial palsy
mental nerves –> lower lip numbness
List three common symptoms related to airway trauma.
sore throat
cough
dysphagia and odynophagia
usually self-limited but can progress –> retropharyngeal abscess in the case of a pharyngeal laceration.
What two things should you do if a tooth becomes dislodged?
identified and retrieved
CXR if necessary ensure tooth not aspirated or swallowed
What is the most common complication of nasotracheal intubation?
Epistaxis
A patient presents with hoarseness and unilateral vocal cord paralysis after an uneventful endotracheal intubation. What is the most likely reason?
endotracheal cuff compression of the recurrent laryngeal nerve
How can you decrease the risk of recurrent laryngeal injury during endotracheal intubation?
Avoiding overinflation and inappropriate placement of the endotracheal cuff
After a difficult intubation a patient develops subcutaneous emphysema, hypotension, increased airway pressures and a mediastinal shift. What is the most likely cause?
tension pneumothorax - after airway perforation
What are some signs and symptoms of esophageal perforation?
subcutaneous emphysema, neck pain, odynophagia, dysphagia, fever, cellulitis, empyema, and mediastinitis
What is the normal intrathoracic pressure range?
-3 to -10 cm of H2O
What are the four common risk factors for Negative Pressure Pulmonary Edema stated in the chapter?
◾Airway lesions.
◾Upper airway surgery.
◾Obesity.
◾Obstructive sleep apnea
postextubation laryngospasm, foreign body, hanging, strangulation, croup, and epiglottitis
How does Post-obstructive/negative pressure pulmonary edema occur?
significant upper airway obstruction – for example, biting the endotracheal tube during emergence from anesthesia
Inspiratory effort to overcome the obstruction –> highly negative intrapleural and alveolar pressures –> large pressure gradient that causes fluid to move out of the pulmonary capillaries and into the interstitial and alveolar spaces
How many hours should a patient be NPO after a light meal? After clear fluids?
6 hours after a light meal
2 hours after clear fluids
Aspirated material is likely to contaminate which bronchus more often?
right main bronchus
What are some risk factors for regurgitation, vomiting, and aspiration?
◾Pregnancy after the first trimester.
◾Acute gastrointestinal disease (esophageal or gastric disease, small bowel obstruction, ileus).
◾GI stasis (trauma, diabetes, obesity, drugs that inhibit gastrointestinal function),
◾The head-down and lithotomy positions.
◾Neurologic conditions that impair protective reflexes (Parkinson’s disease, bulbar palsy, myotonia dystrophica, stroke).
◾Decreased level of consciousness (traumatic brain injury, alcohol intoxication, general anesthesia, and drug overdose).
With what force should cricoid pressure be applied when the patient of unconscious?
10 N (a weight of about 1 kg, which is tolerable) when the patient is awake and then increasing to 30 N (about 3 kg) when asleep
True or false: All patients presenting for surgery should have anti-reflux prophylaxis.
False
When aspiration is suspected, how should the patient be positioned?
semi-prone and tilted to a 30° head-down position
Suction –> secure airway –> NG tube
Always suction before giving PVV
Aspiration pneumonitis is likely to occur if the volume of aspirate is _____ and the pH is ___.
0.3 mL per kilogram of body weight (20-25 mL in adults) with a pH
Antibiotics should be started in a patient who has aspirated and showed signs of pneumonitis for more than ____ hours after the event
48 hours
What is the reported occurrence of corneal injury in the perioperative period?
near 0% with adequate protective precautions, and up to 44% with no protective intervention
How does general anesthesia interfere with the eye’s natural reflexes to protect the cornea?
masking of pain perception
decreased tear production
lagopthalmos (failure of eyelid to close)
abolishment of Bell’s phenomenon (the upward rotation of the eyeball normally observed during sleep to protect the cornea behind the upper eyelid)
Name six risk factors for corneal abrasion.
general anesthesia prone (and possibly lateral) positioning prolonged anesthesia/surgery lower ASA physical status advanced patient age less experienced anesthesia care providers
How does a corneal injury typically present?
foreign-body sensation
photophobia
pain with blinking or eye movement
What is the best preventive measure to avoid corneal abrasion in the perioperative period?
Taping the eyelid closed immediately after induction
Water-based methylcellulose eye ointment
Name three different mechanisms for post-operative visual loss.
retinal ischemia
anterior ischemic optic neuropathy (AION)
posterior ischemic optic neuropathy (PION) - more likely to be related to surgery than AION
cortical blindness
Describe the fundoscopic exam of central retinal artery occlusion.
normal optic disc, pale retina, and cherry-red macula.
What type of retinal ischemia most often occurs due to embolic phenomenon?
Branch retinal artery occlusion
A severe head trauma patient complains of post-operative visual loss. What will the fundoscopic exam most likely reveal?
Purtscher retinopathy (cotton wool exudates) = retinal bleeding
Also seen in:
abdominal trauma
acute pancreatitis
fat or amniotic fluid embolism
What is the prognosis of retinal ischemia visual loss?
most patients sustain permanent visual loss
Name the two types of ischemic optic neuropathy and describe the anatomic location of the vascular compromise.
Anterior ischemic optic neuropathy (AION) - at the head of the optic nerve as it passes through the lamina cribrosa to enter the globe; AION acutely affects the optic disc.
Posterior ischemic optic neuropathy (PION) - in the retrobulbar portion of the optic nerve.
List three high-risk surgeries for AION
cardiac surgery, especially CABG
bilateral radical neck procedures
spine, or other orthopedic surgeries
Other risk factors: head-down positions (prone or steep Trendelenburg) lower nadir [Hbg] (8.0 g/dL) large volumes of crystalloid lower MAP prolonged surgical time (>500 minutes) possibly, pressor support
Describe ophthalmic exam findings of AION in the immediate postoperative period.
optic disc edema
pale
NO pupillary light reflex
Describe ophthalmic exam findings of PION in the immediate postoperative period.
initially normal –> pale in following weeks to months
Most commonly in spinal fusions
List six risk factors for post-operative cortical blindness
cardiac and vascular surgeries - emboli cardiac arrest profound hypotension thrombosis vascular occlusion
normal optic disc + intact pupillary reflex
Prognosis is quite good (unlike ischemic neuropathy)
How can pressure injuries from tourniquets be prevented?
Using wider and contoured cuffs
lower inflation pressures
limiting tourniquet times
How can the brachial plexus be injured during a median sternotomy?
compressed against the clavicle during retraction
What are signs of possible intraneural injection of local anesthetic during peripheral nerve blockade?
pain on injection
low stimulation current
abnormal resistance during injection
Name the four types of heat transfer that occur in the operating room.
Evaporative - sweating and moisture losses from the airway. (~10%)
Conductive - transfer between two adjacent surfaces.
Radiation - transfer of heat from one object (the patient) to another (the room), with no contact between the objects. (MAJOR)
Convection - heat loss as a result of air currents. (#2)
What causes the initial decrease in temperature that occurs during the first hour of surgery?
general anesthesia –> vasodilation –> heat transfer from core to periphery
How can hypothermia result in wound infections?
directly impairing immune function
thermoregulatory vasoconstriction –> reduce tissue oxygen delivery = further predisposing patients to wound infection
What is the most commonly used medication to treat post-operative shivering?
Meperidine
What is the most effective means of maintaining normothermia during longer operations?
Forced-air warming
What are the mechanisms by which humans preserve body temperature in warm environments?
sweating - cools the skin through evaporation
increased respiration - eliminates heat through the excretion of warm gas from the lungs
List 4 consequences of untreated hyperthermia perioperatively.
tissue destruction –> myoglobinuria
coagulopathy - damage to hepatocytes
arrhythmias –> cardiac arrest
increases the MAC of most anesthetics
List 4 potential causes of elevated temperature in an anesthetized patient with an unknown medical history.
- Infection
- Metabolic - thyrotoxicosis, pheochromocytoma, status epilepticus, carcinoid syndrome, and malignant hyperthermia
- Traumatic brain injury
- Meds - anti-cholinergic, TCAs, MAOIs
