Exam 3: Lecture 23 - Anesthetic Complications Flashcards
When do we automatically associate a death with anesthesia after surgery?
-Death that occurs within 48 hours in small animals, or up to 7 days in horses
In dogs, cats, & rabbits, about ___ % of postoperative deaths occur within 3 hours of the end of anesthesia
50%
In horses, ___% of complications occur in recovery and are neuromuscular or respiratory in nature
92%
What complications can occur days to weeks after anesthesia?
-Decreased renal or hepatic function
What are common complications that can occur during the peri-anesthetic period?
-The 4 H’s!
1. hypoventilation
2. Hypotension
3. Hypothermia
4. Hypoxemia
-CV
-Respiratory
-CNS
-Anesthetic depth
-Temperature regulation
-Dysphoric recovery
-Gastroesophageal Regurgitation (GER) & possible aspiration
What are uncommon side effects that can occur during the peri-anesthetic period?
-Metabolic
-Neuromuscular
-Post-anesthesia cortical blindness
___ is a common CV complication due to drugs, physical status of patient, other causes of vasodilation (e.g. anaphylaxis)
Hypotension (MAP < 60 mmHg or < 90 mmHg on Doppler)
How do we treat the CV complications that can occur during anesthesia?
-Decrease depth, consider fluid therapy, and vasopressor and/or positive inotrope
With hypotension, a severe decrease in ___ leads to decreased perfusion of optic nerve and kidneys
BP
How is hypertension defined?
MAP > 150 mmHg
What are CV complications associated with anesthesia?
-Hypotension
-Hypertension
-Hypovolemia due to hemorrhage
-Cardiac arrest
-Arrhythmias (consider treatment if BP is affected. Look for underlying cause)
How is hypoventilation defined?
-ETCO2 > 55 mmHg
-Most common complication, usually caused by anesthetic drugs and/or excessive anesthetic depth.
-Could be due to pre-existing co-morbidities (always check equipment!)
-Can lead to respiratory acidosis, hypoxemia, and increased intracranial pressure
What is the treatment for hypoventilation?
-Check depth and adjust if appropriate
-Provide IPPV
-Change position of patient if possible
-Check equipment
When would we see hypoxemia in anesthetized patient?
-Unlikely if intubated and on 100% O2, but can quickly become life-threatening
-SpO2 of 95% = PaO2 of 80 mmHg
-SpO2 of 90% = PaO2 of 60 mmHg
-Patient can be hypoxemic and not show cyanosis!
What is the treatment for hypoxemia?
-Check O2 flow rate for adequacy
-Check placement of ETT
-Check anesthesia machine & SpO2 probe
-Give IPPV
-Consider adding PEEP (stert w/ 2.5 cmH2O)
-Assess perfusion and support cardiac output
-Change position to sternal & discontinue anesthesia if no improvement with other interventions
What are the 5 causes of hypoxemia?
- Hypoventilation
- V/Q mismatch
- Decreased FiO2
- Right to left shunt
- Diffusion impairment
When does GER (gastro-esophageal reflux) occur during general anesthesia?
-When gastric contents pass into esophagus
-Can look like clear or brown fluid coming from nose or mouth
Up to ____ % of dogs may experience GER during general anesthesia, but not often noticed
50-60%
Can you see GER in cats?
-Yes, up to 33% incidence reported
What can GER lead to?
-Esophagitis, esophageal stricture formation, or aspiration pneumonia
What are risk factors for GER?
-Pregnancy (later stage)
-Anesthetic drug protocol (e.g. morphine)
-Abdominal & orthopedic sx
-Breed (brachycephalic, large, or deep-chested dogs)
-Expected complication of endoscopy
-Pre-existing conditions (GI disease, megaesophagus, dysphagia, regurgitation)
-Length of preop fasting time & type of food (small meal of canned food 3 hrs prior may reduce incidence of GER)
-Prolonged duration of anesthesia
-Recumbency & changes in body position during anesthesia
-Older dogs
How do we treat GER?
-Be sure ETT cuff has good seal, use pH strip to measure pH - treat if acidic or basic
-Esophagus suctioned & lavaged w/ warm water & bicarb using urinary catheter or double-lumen suction catheter, after regurgitation occurs & before patient recovers
-Sucralfate & H2-receptor antagonist can be considered
-Admin. metoclopramide by bolus & CRI at higher doses than commonly used reduced incidence
-Oral omeprazole 4 hours prior may reduce GER
-Maropitant (Cerenia_ does NOT prevent GER
What are some metabolic complications of anesthesia?
-Hypoglycemia or hyperglycemia (glycemic control important for diabetic patients, monitor BG at reg. intervals & be prepared to treat)
-Acid-base disturbance (resp. acid-base disturbance discussed in blood gas analysis lecture)
-Electrolyte imbalance
Treatment of hyperkalemia should be done
BEFORE anesthesia, even in an emergency case!
What are some neurological & musculoskeletal complications of anesthesia?
-Myopathy
-Neuropathy
-Prolonged or weak recovery
-Myoclonus
-Seizures
-Post-anesthetic cortical blindness
How is myopathy caused in anesthetized patients?
-By ischemic muscle damage due to prolonged compression or inadequate padding and/or prolonged hypotension leading to under-perfusion of muscles
How is peripheral neuropathy caused in anesthetized patients?
-Stretching, compression, ischemia, metabolic derangement, & surgical resection
What is the treatment of myopathy & neuropathy?
-Prevention is better than treatment!
-Treatment includes IVF for diuresis, analgesics, anti-inflammatory drugs, sedatives if needed, and vasodilators
-Rehabilitation therapy is also beneficial
When can blindness after anesthesia be seen in cats?
-May be seen after dental cleanings, likely due to use of mouth gags leading to cerebral ischemia (maxillary artery blood flow compromised)
-Could also happen due to severe hypotension and/or CPA
What are signs of dysphoria in recovery (aka “rough recovery”)?
-Vocalization
-Panting
-Restlessness
-Urination/defecation
-Salivation
Emergence delirium:
-Thrashing, agitation, hyperexcitable
-“Lights are on but nobody is home”
How is dysphoria treated in recovery?
- Most commonly used = dexmedetomidine (could be continued as CRI if needed)
- Commonly used = Acepromazine
- If benzodiazipine is suspected as cause of dysphoria, the flumazenil may be considered
- If severe dysphoria, consider propofol to “reset” recovery
- Consider naloxone if opioid-induced dysphoria suspected (Use butorphanol instead if continued analgesia desired)
What are some examples of human error preventable complications?
-Leaving pop off valve closed
-Intracarotid or perivascular injection
-Walking away from patient & it falls off table
-Tracheal tear from turning intubated patient attached to breathing system
What are some examples of drug preventable complications?
-Miscalculation, administration of wrong drug, incorrect dose, route, or reconstituted to incorrect concentration
-Selected wrong drug for debilitated patient
What are some examples of equipment malfunction preventable complications?
-Sodasorb expired or channeling occurs
-Oxygen tank runs out or O2 supply line disrupted
-Misassmebly of machine or breathing system
-Sticking of exhalation valves -> rebreathing CO2
-Hole in ETT cuff; kinking or obstruction of ETT
How are tracheal tears in cats caused?
-Over-inflation of ETT cuff, turning patient while connected to breathing system, stylet puncture, extubation with cuff inflated
-Often seen in cats having dentals
What are the clinical signs of a tracheal tear in cats?
-Subcutaneous emphysema, dyspnea, respiratory stridor, pneumomediastinum +/- pneumothorax
-Inspect ETT for blood at extubation
-Signs develop hours to days after anesthesia - cat may stop eating, cough, and have a fever
How are tracheal tears in cats treated?
-Medical vs. surgical
-O2 therapy, cage rest & sedatives
-SQ emphysema may resolve in 1-6 weeks
How are tracheal tears in cats prevented?
-Use 3.5-4.5 mm ETT, add 0.5 mL air at a time with 3 cc syringe until pressure holds at 15-20 cm H2O
-Disconnect patient when flipping
-Deflate cuff for extubation
What are other possible surgery or anesthesia complications?
-Swollen feet and/or joint pain from being tied too tightly on surgery table
-Corneal ulcers
-Over administration of IVF
-Epidural needle or local anesthetic being placed directly in the nerve
What should you do after an anesthetic complication?
-Hold M&M rounds afterwards to discuss complication(s)
-Development of SOP to prevent or reduce future occurrences
