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Anaesthetic complications Flashcards

1
Q

What should the pressure of the ETT cuff be

A

20 - 30 cm H20
Use cuff manometer
Inflated just enough to prevent leak

Complications
Acute - postoperative stridor
Chronic - tracheal stenosis

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2
Q

What is the smallest ETT with a cuff and is this safe to use in kids

A

ETT 3.5 mm internal diameter

Safe to use if correctly used

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3
Q

What causes permanent postoperative visual loss (POVL) following non-ocular surgery

A
  1. Retinal artery occlusion
  2. Ischaemic optic neuropathy
  3. Cerebral vision loss

Blurring to blindness can occur

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4
Q

What can happen if the eyes are not taped during GA

A

Corneal abrasion ± vision loss
Check eyes are protected when lateral and prone
Pad eyes before taping before head and neck surgery

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5
Q

What anaesthetic complications can arise from improper positioning

A

Nerve injury

  • Radial nerve (Saturday night palsy)
  • Ulnar nerve
  • Brachial plexus (hyperextend > 90 deg)
  • lateral popliteal nerve (Lithotomy)
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6
Q

What are the complications of neuraxial anaesthesia

A
  1. Neural injury
  2. Epidural hematoma
  3. Epidural abscess
  4. Meningitis
  5. Post dural puncture headache (PDPH)
    - use 25G Whitacre or Sprotte (PPNs) instead of 22G Quincke (cutting needle)
  6. Sympathectomy, hypotension
  7. High/complete spinal: Low HR, Low BP, Apnoea
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7
Q

Classify and describe the complications of central venous cannulation

A 
EARLY
Technical
 - Pneumothorax
 - Haemothorax
 - Nerve damage

Dysrhythmias (guidewire)

Air embolism (put patient head down)

LATE
Infection
- Sepsis
- Endocarditis

Thrombosis

Tamponade

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8
Q

Classify and describe the risk factors for postoperative nausea and vomiting

A

PATIENT

  • Children
  • Females
  • Hx motion sickness
  • Previous PONV / Chemo NV
  • Obesity
  • Non - Smokers

ANAESTHETIC

  • Prolonged pre-op starvation
  • Hypotension with neuraxial anaesthesia
  • Emetic drugs: Opioids, etomidate, ketamine, N2O, VA
  • Longer duration anaesthesia

SURGICAL

  • Ear and Eye surgery (esp. strabismus surgery)
  • Intra-abdominal surgery
  • Laparoscopic surgery
  • Gynaecological / Orchidopexy

POST-OP

  • Pain
  • Opiates
  • Hypotension
  • Forcing oral fluids to soon
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9
Q

What are the patient factors associated with PONV

A
  1. Children
  2. Females
  3. Hx PONV / Hx chemo NV
  4. Non-smoker
  5. Hx motion sickness
  6. Obesity
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10
Q

What are the anaesthetic factors associated with PONV

A
  1. Prolonged preop starvation
  2. Hypotension with spinals/epidurals
  3. Emetic drugs: Opioids/Etomidate/Ketamine/N2O/VAs
  4. Prolonged duration of anaesthesia
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11
Q

What are the surgical factors associated with PONV

A
  1. Ear and eye surgery (esp. strabismus)
  2. Intra-abdominal surgery
  3. Laparoscopic surgery
  4. Gynae surgery / orchidopexy
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12
Q

What are the post-op factors associated with PONV

A
  1. Pain
  2. Opioids
  3. Hypotension
  4. Forcing oral fluids
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13
Q

Describe Risk Scores for PONV for Adults and Kids

A

Adults - Apfel’s simplified risk score

Female
Non-smoker
PONV before
Expected Opioids

0, 1, 2, 3, 4, of the above associated with 10, 20, 40,60,80 % risk respectively

Kids

Age > 3
Duration > 30 mins
POV before / relative with PONV /POV
Strabismus surgery

1,2,3,4 of these associated with 10,30,50,70 % risk respectively

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14
Q

Describe the approach to prevention of PONV in patients with different PONV risk

A

HIGH RISK for PONV

  1. Multimodal pain Rx
  2. Minimise opioids
  3. Regional instead of GA
  4. TIVA with propofol instead of VAs
  5. Antiemetics
    - Dexamethasone 4 - 8 mg after induction
    - Ondansetron (5HT3 antagonist) 4 - 8 mg end of surgery
  6. Rescue antiemetics (in different class to the above)
    - Prochlorperazine (Stemetil) 12.5 IM stat 10 PO TDS
    - Droperidol (Inapsin) 2.5mg STAT IV/IM then 1.25mg prn
    - Metoclopramide (Maxalon) 10mg IV/IM/PO 8hrly
  7. Non-pharmacological
    - IV fluids - maintain hydration
    - Complementary/alternative therapies (acupuncture/bracelets/ginger)

MOD RISK PONV

  1. Multimodal pain Rx
  2. Minimise opioids
  3. Then choose to modify anaesthetic technique or antiemetics or non-pharmacological

LOW RISK PONV
Patient/anaesthetist preference
- Ondansetron at the end of surgery

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15
Q

What are the mechanisms of action of: dexamethasone, ondansetron, prochlorperazine, droperidol, metoclopramide and promethazine

A

DEXAMETHASONE

  • Incompletely understood
  • Decreased prostaglandins –> decreased endogenous opioids

ONDANSETRON
- 5HT3 (serotonin 3) receptor antagonist in the chemoreceptor trigger zone and in the vagus nerve

PROCHLORPERAZINE
- D1 and D2 postsynaptic receptor antagonist in the chemoreceptor trigger zone

DROPERIDOL
- Blockade of dopamine stimulation in the chemoreceptor trigger zone

METOCLOPRAMIDE

  • Prokinetic (enhances peristaltic response to Ach)
  • Blocks D and 5HT receptors in CTZ
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16
Q

Define awareness and describe the different types and how common the different types are

A

Awareness under anaesthesia is the ability to recall events occurring during general anaesthesia

1: 10 000 - awareness with pain
1: 1000 - some awareness without pain

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17
Q

What is the definition of hypothermia

A

Core Temperature < 25 deg C

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18
Q

When should the temperature be monitored

A

Any case longer than 15 minutes

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19
Q

What are the five mechanisms of heat loss during surgery and state the approximate contribution of each to heat loss by the patient in the operating theatre

A
  1. Radiation - 40%
  2. Convection - 30%
  3. Evaporation - 20%
  4. Respiration - 10% (8% evaporation, 2% heating of air)
  5. Conduction - (very low contribution)
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20
Q

What is the incidence of death in first world and third world hospitals attributable to anaesthesia

A

1st world - 1:40 000

Rural areas with poorly trained anaesthetists: 1 : 280

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21
Q

What is the eponymous name for chemical pneumonitis caused by peri-operative aspiration of gastric contents

A

Mendelson’s syndrome

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22
Q

Describe a system to determine which patients are at risk for Mendelson’s syndorme

A
  1. Full stomach
  2. Trauma
  3. Obesity
  4. Ileus
  5. Gastric outlet obstruction
  6. Intra-abdominal pathology (acute abdomen)
  7. Pregnancy
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23
Q

What three strategies can reduce the risk of aspiration

A
  1. Reduce gastric pH
    - Sodium citrate 30 ml within 30 mins
    - Ranitidine 300mg (Zantac)
    - Omeprazole 40mg (Losec)
  2. Increase gastric emptying and LES tone with
    - Metoclopramide 10 mg (Maxalon)
  3. Reduce gastric volume via suction with NGT
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24
Q

Give 5 causes of laryngospasm

A
  1. ETT/LMA/OPA during light anaesthesia
  2. Irritating volatile agents (iso/des/enf)
  3. Secretions on the vocal cords
  4. Surgical stimulus (dilation of Cx or anal sphincter)
  5. Surgical stimulus during light anaesthesia
25
Q

Describe the management of laryngospasm

A
  1. Avoid manipulation of the airway whilst in light plane of anaesthesia
  2. Stop causative stimulus
  3. FiO2 1 + PPV
  4. Propofol: 10 - 50 mg
  5. If there’s time - Spray cords: 2% lidocaine
  6. If no time - Sux 1 mg/kg and intubate.

If laryngospasm occur during emergence - then give 1/4 of the usual dose of sux and support the airway or intubate if not able.

26
Q

List the causes of bronchospasm

A
  1. All 5 causes of laryngospasm
  2. Carinal stimulation (ETT deep)
  3. Asthmatics/COPD/Pneumonia
  4. Histamine release (Sux/Roc/Atra/Morphine/Thio)
  5. Anaphylaxis
27
Q

Describe the management of bronchospasm

A

PREVENTION

  1. Avoid elective surgery if underlying respiratory conditions are not optimised.
  2. Regional Anaesthesia in high risk patients

GENERIC Rx

  1. Stop the precipitant, declare and call for help
  2. FiO2 100%

SPECIFIC Rx

  1. Deepen with SEVO (non-irritating)
  2. SALBUTAMOL inhaled 5mg every 15 mins
  3. Salbutamol 0.25mg IVI then infuse at 5mcg/minute
  4. PROPOFOL( 10 - 50mg)
  5. MGSO4
  6. ADRENALIN 100 ug SC
  7. Adenalin 10ug boluses IVI
  8. KETAMINE 2mg/kg
  9. HYDROCORTISONE 200mg
  10. JENNY’s solution
    - 100ug adrenalin (0.1 mL) + 5mL of 2% lido to 10 mls
    - Use 1 ml per 10 kg body weight and bag it down the ETT
  11. Ventilation: High pressures + slow rate (allow exhalation)

(Aminophylline 250mg slow IVI up to 5mg/kg - not to be paired with ketamine)
- narrow therapeutic index

28
Q

What are the causes of postoperative respiratory depression and decreased ventilation

A
  1. Anaesthetic agent/opioid
  2. Muscle relaxant
  3. Partial airway obstruction
  4. Abdo surgery (pain)
  5. Abdo distension
  6. Hypoglycaemia
  7. Electrolytes
  8. High block (spinal/epidural)
  9. Central depression due to stroke/bleed
29
Q

Describe the causes of intra-operative dysrhythmia

A

Common causes

  1. Drugs
    - Halothane (sensitises cardiac conduction system to catecholamines)
  2. Electrolyte imbalance: Hyper and hypokalaemia
  3. Autonomic stimulation: Intubation / peritoneal stretching
  4. Underlying heart disease
30
Q

Classify the factors that increase the perioperative risk of myocardial infarction

A

PATIENT factors
1. Heart disease (Valvular/Ischaemic/Failure/dysrhythmia etc)

ANAESTHETIC factors

  1. Hypotension/Hypertension
  2. Tachydardia
  3. Hypoxia

SURGICAL factors

  1. Intrathoracic surgery
  2. Abdominal surgery
  3. Vascular surgery
  4. Emergency surgery
31
Q

What type of hypersensitivity reaction is anaphylaxis and describe the pathophysiology

A

Type hypersensitivity reaction
IgE Ab on the surface of mast cells and basophils bind the allergen and become cross-linked leading to degranulation of mast cells or basophils and the release of histamine and newly formed arachidonic acid metabolites

32
Q

What is the clinical presentation of anaphylaxis

A

TRIAD

Skin (wheal and flare / urticaria)
RSP (Angiodema/bronchospasm/hypoxia)
CVS (Hypotension + tachy cardia to CVS collapse and Cardiac arrest)

GIT effects of the anaphylactic reaction are not immediately apparent intraoperatively

33
Q

Which drugs used in anaesthesia are most likely to cause anaphylaxis

A
  1. Antibiotics
  2. Muscle Relaxants
    - Sux
    - Benzylisoquinolinums (ATRA/CIS/MIV)
    - Rocuronium (aminosteroid)
  3. Others
    - Opiates
    - Local anaesthetics (esters>amides)
    - Colloids (not crystalloids)
    - Blood
    - Latex
    - Rarely induction agents (thio/propofol)
34
Q

Which anaesthetic drugs do not cause anaphylaxis

A

volatile anaesthetic agents

35
Q

Describe the treatment of anaphylaxis

A
  1. Declare, call for help, stop precipitant
  2. ABCDE
  3. IV ADRENALIN 1mg in 20 ml syringe
    - titrate 1/2 to 1 ml (25 - 50 ug) to effect

IM adrenalin in patients with no iv line.

Second line:

  1. FLUID
  2. Hydrocortisone 100mg IV
  3. Salbutamol 5mg inhaled
  4. Ranitidine/Promethazine
  5. Glucagon 1mg (patients on beta blockers)

Airway oedema may be significant and might warrant prolonged ventilation
–> Consider ICU

Take blood for mast cell tryptase
Inform GP
Allergy clinic -> ? cause
Medic Alert Bracelet

36
Q

Define pharmacogenetic disease

A

Genetic diseases that are unmasked by exposure to specific drugs

37
Q

Which pharmacogenetic diseases have specific relevance to anaesthesia

A
  1. Malignant Hyperthermia
  2. Halothane Hepatitis
  3. Scoline Apnoea
  4. Porphyria
38
Q

Define malignant hyperthermia

A

A rare inherited syndrome characterised by a life-threatening hypermetabolic state triggered by exposure to a triggering agent: all volatile agents or succinylcholine.

39
Q

How do you recognize malignant hyperthermia

A 
Unexplained:
- tachycardia
- hypercapnoea
- hypoxia
- trismus 
- elevated core temperature (late)
Late: rhabdomyolysis, myoglobinuria, renal failure, DIC, multiorgan failure

Onset may be rapid and fulminant or slow and insidious

40
Q

What is the defect responsible for malignant hyperthermia

A

Defective ryanodine receptor on the sarcoplasmic reticulum which is a calcium channel receptor. Once exposed to the trigger agent, the receptor stays open and floods the cell with calcium with a resultant persistent contractile state.

41
Q

Differentiate malignant hyperthermia from the serotonin syndrome and neuroleptic malignant syndrome

A

Malignant Hyperthermia

  • Onset: INTRAOPERATIVE
  • Trigger: Sux | Volatiles
  • Muscle rigidity: rigor mortis like
  • Rx: Dantrolene

Serotonin syndrome

  • Onset: over 24 hours
  • Triggers: E.g. Citalopram/fluoxetine
  • Muscle rigidity: Neuromuscular hyperactivity (tremor | hypereflexia | myoclonus)
  • Rx: Benzo + cyproheptadine (serotonin antagonist)

Neuroleptic Malignant Syndrome

  • Onset: 1-3 days
  • Triggers: antipsychotics (haloperidol) and antiemetics (metoclopramide, droperidol, prochlorperazine, promethazine)
  • Muscle rigidity: sluggish neuromuscular response (rigidity and bradyreflexia)
  • Rx: Dantrolene
42
Q

What is the differential diagnosis for malignant hyperthermia

A

EQUIPMENT MALFUNCTION

  1. Expiratory valve malfunction
  2. Insufficient ventilation (circuit leak)
  3. Exhausted soda lime

HYPERMETABOLIC STATE

  1. Phaeochromocytoma
  2. Thyroid storm
  3. Sepsis

NEUROMUSCULAR ABNORMALITY

  1. Neuromuscular disease
  2. Neuroleptic malignant syndrome
43
Q

Outline the Initial Management of Malignant hyperthermia

A
  1. Declare, Help, FiO2
  2. Discontinue TRIGGER
    - Convert to TIVA (Propofol/ketamine/midazolam) boluses or infusion
  3. Rx MUSCLE contraction
    Start Dantrolene
    - Fridge
    - Reconstitute with STERILE WATER ONLY
    - Bolus 2.5 mg/kg then give 1mg/kg prn
    - Call GSH for more dantrolene –> initial dose requires 9 x 20mg vials to be administered
    - Thereafter: 1mg/kg every 4 hours or 0.25 mg/kg/hr x 24 hours
  4. Rx TEMPERATURE
    - Ice packs in groin and axillae
    - Cold IV fluids
    - Peritoneal lavage with cold fluid
    - Target Temp < 38 deg C
  5. Rx HYPERKALAEMIA
    - NaHCO3 with hyperventilation and Insulin/glucose shift
  6. Rx DYSRHYTHMIAS
    - MgSO4 or Amiodarone
    - NOT CCB (interfere with dantrolene)
  7. Rx ACIDOSIS
    - NaHCO3 8.5% 1 - 2 ml/kg with hyperventilation
  8. Rx KIDNEYS
    - Forced alkaline diuresis: UO 2ml/kg/hour with IV fluids and diuretics
  9. Admit to ICU with IABP, CVP, Urinary Catheter, oesophageal temperature probe
44
Q

Summarise the treatment of MH

A
  1. Declare, Help, FiO2
  2. Stop TRIGGER
  3. Rx ABCDE’s
  4. Rx MUSCLE TONE (DANTROLENE)
  5. Rx HYPERKALAEMIA
  6. Rx ACIDOSIS
  7. Rx DYSRHYTHMIAS (not with CCB)
  8. Rx TEMPERATURE
  9. Rx KIDNEYS
  10. ICU with invasive monitors
45
Q

Describe the actual reconstitution and administration of Dantrolene

A

Initial dose: 2.5 mg/kg
Then 1mg/kg every 4 hours

9 vials required for 70 kg adult

1 vial has 20 mg
1 vial is reconstituted with 60 ml of STERILE WATER (Not NaCL and not D5W)

Shake until the solution is clear and ensure there is no precipitation present

Protect: from direct light
Use: within 6 hours of reconstitution
Store: at room temperature
Do not transfer into glass bottles
Do transfer into empty sterile plastic vacoliter bags if necessary
46
Q

List 5 specific practical requirements after dantrolene has been reconstituted

A
  1. Protect from direct light
  2. Use within 6 hours
  3. Store at room temperature
  4. Do not transfer into glass container
  5. Do transfer into sterile plastic vacoliter bags if necessary
47
Q

List 5 specific important aspects related to the reconstitution of dantrolene

A
  1. Reconstitute with sterile water NOT NaCl or D5W
  2. Each 20 mg amp reconstituted with 60 mL STERILE WATER to achieve a pH of ± 9.5
  3. Call GSH for more amps as it is likely more will be needed
  4. Add each reconstituted amp to a sterile plastic vacoliter and administer 2.5 mg/kg
  5. 3000mg of mannitol and NaOH present within the amp permit the pH of 9.5 when reconstituted with 60 mL sterile water.
48
Q

How can a definitive diagnosis of MH be made?

A

IN VITRO CONTRACTURE TEST (IVCT)

  • Muscle biopsy must be taken
  • Performed rarely –> now done at the MH Center in Pretoria

Genetic testing
- Complex and a negative test cannot rule out MH susceptibility

So…
NO IVCT and positive Fam Hx / adverse reaction to GA suggestive of MH –> presumed diagnosis and MH safe anaesthetic is performed.

49
Q

Describe an MH safe anaesthetic

A
  1. Avoid GA entirely: regional
  2. If GA required
    - First on the list
    - Remove vaporizers from machine
  3. Flush machine with high flow O2 for 20 minutes prior to anaesthetic: to reduce vapour concentration in the FGF to less than 5 ppm
  4. Maintain FGF of 10 L/minute throughout anaesthetic even after lengthy purging
  5. Use Activated Carbon Filters (ACFs)
  6. TIVA with propofol
  7. Muscle relaxation: NDMR are safe (No sux)
  8. Know where the Dantrolene is kept (usually locked up)
50
Q

Summarise an approach to an MH safe anaesthetic

A
  1. RA
  2. If GA then TIVA and NDMR
  3. Purge machine (20 mins) < 5 ppm + Replace breathing circuit.
  4. FGF > 10 L/minute throughout anaesthetic
  5. Activated Carbon Filters
  6. Know where dantrolene is kept.
51
Q

What is the incidence of halothane hepatitis

A

1: 35 000 anaesthetics

52
Q

What is the pathophysiology of halothane hepatitis

A

Metabolites of halothane (20% metabolized in the liver) –> type 2 hypersensitivity reaction in the liver –>fatal fulminant hepatitis

53
Q

Under what circumstances is halothane hepatitis more likely to occur?

A

Repeat exposure to halothane within 6 months of initial halothane exposure

Existing liver disease
Fat, middle aged females

(Isoflurane and desflurane have been implicated with causing fulminant hepatitis but much less frequently - significantly lower liver metabolism)

54
Q

What is scoline apnoea

A

Susceptible individuals have an abnormal or absent pseudocholinesterase (buturylcholinesterase) enzyme resulting in prolonged paralysis after a single dose of succinylcholine.

Homozygous patients for the condition
Rx - prolonged sedation and ventilation after sux
–> FFP does contain the enzyme but is associated with all the risks associated with blood transfusion.
–> Risk vs benefit (? ventilation facility available)

55
Q

Why should recovery from succinylcholine be checked before administration of NDMR?

A

Return of breathing on vent or 4 strong twitches on PNS should be demonstrated.
If patient does not recover after the anaesthetic you will not know if it is due to sux or NDMR.

56
Q

Define porphyria

A

A pharmacogenetic disease involving porphyrin metabolism in which certain drugs such as barbiturates (thiopentone) can precipitate an acute attack resulting in:

  1. Paralysis
  2. Acute abdominal pain
  3. Death
57
Q

In which population in RSA does porphyria have a higher incidence

A

Dutch descent/Afrikaners

58
Q

What should be done if a patient reports a history of porphyria

A

Consult one of the safe/use with caution/unsafe drug lists for porphyria and plan accordingly

DA (50 decks)

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