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You are in Home >> Exams >> Mitchell Anaesthetic Notes


Anaesthesia for Miscellaneous surgery

Created: 29/8/2006
Updated: 8/1/2007
 

Outline management of a 20 year old man who is intoxicated for ORIF # mandible 

  • Issues
    • Semiurgent surgery in an intoxicated and non-fasted patient
    • Trauma patient with possible associated injuries and airway compromise
    • Shared airway surgery with likely bleeding
    • Possibility of wiring the jaw closed with associated airway access compromised
  • Assessment
    • Routine anaesthetic assessment, plus
    • History of trauma, associated injuries
      • Jaw mobility, limited by pain or mechanical obstruction
    • Intoxication
      • Drugs used, BAC measurement
      • Competence to consent
      • Complications of drugs
        • Full stomach, specific effects of other drugs: narcotics, amphetamines
      • Difficulty of detecting altered conscious state from head injury
      • Legal concerns if a driver: BAC sample handling dictated by law
    • Examination
      • Mouth opening, careful airway assessment
    • Investigations
      • Trauma X-rays
      • Jaw X-rays or OPG
      • Routine bloods, G&H
    • Decision on timing of surgery
      • Often not necessary to proceed before patient is sober and fasted
    • Plan for anaesthesia
      • Rapid sequence or awake nasal FOB if not fasted and surgery cannot be deferred
      • Otherwise plan for GA with nasal intubation when fasted
    • Premedication
      • Routine antacid and/or anxiolytic
    • Consent
      • Discussion of plan with patient, especially if awake FOB planned
  • Intraoperative
    • Preparation
      • Routine equipment check, suction
      • Availability of difficult intubation equipment
    • Access and monitoring
      • Routine: ECG, SpO2, NIBP etc.
      • IV access
    • Induction
      • Good jaw mobility: conventional induction, nasal Rae
      • Potentially difficult: awake nasal FOB
      • Nasal lidocaine, phenylephrine
      • Topical lignocaine to airway for awake FOB
      • Throat pack insertion
    • Maintenance
      • Conventional balanced technique
      • Remember to remove throat pack if jaw if to be left wired
      • Analgesia supplemented with local infiltration or nerve block
      • Prophylactic antiemetic
    • Emergence
      • Usually mandible plated and mobile
        • Remove throat pack, suction, inspect larynx for blood
        • Awake extubation in lateral position
        • Consider suctioning of ETT tube in nasopharynx and nose
      • Jaw wired
        • Fully awake extubation required
        • Equipment on hand to cut wiring
        • Drugs and equipment for emergency reintubation
        • Pull tube through cords and leave as nasopharyngeal airway
  • Postoperative
    • Analgesia
      • Usually PCA or intermittent narcotic plus oral adjuvant analgesics
    • Level of care
      • PACU and normal surgical ward


Outline management of anaesthesia for cataract extraction


Elective surgery with minimal physiological impact is usually performed on elderly patients.

  • Issues
    • Population with high incidence of concurrent disease
    • Commonly a brief operation with high turnover
  • Preoperative
    • Assessment
      • Routine, plus
      • Cataract
        • Nature of surgery (intracapsular vs extracapsular)
        • Previous cataract surgery
        • Primary disease, e.g. diabetes
      • Retrobulbar or peribulbar blockade
        • Axial length
        • Assessment of orbit and ease of access to retrobulbar space
      • Coexistent disease
        • Particularly cardiac disease, respiratory disease
          • Persistent cough, tremor, claustrophobia may make regional unfeasible
    • Premedication
      • Minimal as sudden waking may be associated with movement
  • Intraoperative
    • Monitoring and access
      • IV access
      • Routine monitoring: HR and SpO2 required during block
        • ECG, NIBP, SpO2, ETCO2 on Hudson mask
    • Block
      • Deep intraconal (“retrobulbar”) vs peribulbar vs topical plus infiltration
      • My practice
        • Topical oxybuprocaine (benoxinate)
        • Sterile solution 2% lidocaine, 0.4% bupivacaine, 15 U/ml Hyalase
        • Aseptic technique
          • Medial canthus direct posteriorly 30 g 12 mm 2.5 ml full depth
          • Inferotemporal percutaneous 27 g 32 mm 3.5 ml hub at level of limbus
          • Slow injection with periodic aspiration
        • Gentle massage, assessment of IOP and orbital pressure
        • Honan’s balloon if required by surgeon
        • Supplementation for intact movement or sensation according to distribution and surgical requirements
        • Facial nerve block usually not required
    • Issues intraoperatively
      • Maintain communication
      • Atropine available for bradycardia
      • Surgeon may supplement with sub-Tenon’s injection if required
  • Postoperative
    • Usually good analgesia from block


Ophthalmic anaesthesia

  • Anatomy
    • Layers
      • Connective tissue globe: conjunctiva, sclera
      • Retina: nerve tissue
      • Choroid: vascular
    • Humour: aqueous and vitreous
    • Size: A-scan typically 20-24 mm
      • High myopes may be >25 mm: increased risk with retrobulbar block
    • Muscles: 4 recti, 2 obliques, orbicularis oculi, levator palpebrae
    • Nerves
      • Motor: III MR, IO, IR, SR
        • IV: SO
        • VI: LR
      • Sensory: conjunctive nasociliary V1
      • Parasympathetic: short ciliary br of III
    • Sympathetic: ciliary ganglion to V and carotid plexus
    • Physiology
      • IOP: 10-15 cmH2O
        • Varies with volume of aqueous and blood in the globe and muscle tone causing extrinsic pressure
        • CVP transmitted readily to IOP
        • Rises with coughing, vomiting, head-down, IPPV
        • Suxamethonium causes a small rise
        • Induction agents: reduce IOP
        • Dizolamide, acetazolamide: reduce aqueous secretion
      • Atropine IV causes little mydriasis, little risk with closed-angle glaucoma
      • Complications of pressure changes
        • Rise: reduced perfusion pressure, exuding of contents if an open eye
        • Fall (removal of contents): potential for retinal detachment
      • Oculocardiac reflex: afferent V short ciliary n., ciliary ganglion, ophthalmic, reticular formation, efferent X
        • Bradycardia, standstill, nausea and vomiting
        • Can be elicited by other stimuli like NGT, faciomaxillary surgery
        • Classically eye traction or pressure (sometimes retrobulbar block, face mask pressure)
        • Does not require an intact eye: e.g. prosthesis fitting.
        • Management: tell surgeon to stop, deepen anaesthesia, prophylactic atropine or treatment
        • Fatigues with repeated stimulation
      • Nausea and vomiting
        • Most common with squint surgery, vitreoretinal surgery
        • Usually post-recovery, continues up to 24 hours
        • Raises IOP, delays discharge
        • Cause: visual change after squint surgery causes "motion-sickness"
          • ? Oculogastric reflex: vagal effect
        • Prevention
          • General: hydration, low nausea anaesthetic (no opiates, N2O…),
          • Antiemetics
          • Premedication with benzodiazepine (esp. lorazepam)
          • Midazolam blocks adenosine reuptake in area postrema (required for dopamine synthesis)
      • Other concerns: drug interactions, coexisting disease (esp. diabetes)
  • Vitreoretinal surgery
    • Often with poorly controlled diabetes or else ex-prem babies
    • Long cases, poor airway access
    • Immobility required
    • May have gas or oil: no N2O while gas still present
  • Open eye injury
    • Need to know
      • Degree of injury: salvageable eye? Take care with IOP.
      • Urgency: clean vs dirty injury. Clean: wait until fasted
      • Dirty: RSI required
    • Children: LA cream for IV, sedative premedication
    • Minimize IOP rise with big induction agent dose, fentanyl, topical local to airway
  • EUA for glaucoma
    • Measurements require an anaesthetic which doesn't alter IOP much
    • Halothane: reduces IOP
    • Kids usually have multiple anaesthetics
  • NLD probe
    • Simple mask anaesthetic
    • Some babies have a mucocoele: aspiration of pus
  • Sub-Tenon's block
    • Painless, fast onset, good motor block, no needle in retrobulbar space
    • Catheter passed subconjunctivally
    • Look up and out, nick conjunctival fascia, probe around globe to post attachment of Tenon's fascia

 

Outline management of anaesthesia for a penetrating eye injury

  • Issues
    • Emergency surgery, usually a trauma patient with a full stomach
    • Avoidance of rise in IOP with potential expulsion of globe contents
  • Assessment
    • Routine, plus
    • Trauma
      • Associated injuries, ABCDE, fasting status
    • Eye
      • Nature of injury, acuity
  • Preoperative
    • Premedication
      • Antacid, H2 blocker, prokinetic
  • Intraoperative
    • Monitoring and access
      • Routine: IV, ECG, SpO2, NIBP, gas analysis, disconnect etc.
    • Induction
      • Modified RSI
        • Preoxygenation
        • Predosing with lidocaine, remifentanil, β-blocker IV
        • Induction with thiopentone or propofol
        • Relaxation options
          • Suxamethonium
          • Predose with NDB followed by suxamethonium
          • High dose NDB (e.g. rocuronium)
          • Trade-off between risk of coughing and increased IOP with suxamethonium
  • Maintenance
    • Lower IOP
      • Mild hyperventilation, β-blocker, acetazolamide, mannitol, hypotension
    • Monitor muscle relaxation to prevent coughing
    • Prophylaxis: antibiotics, tetanus
  • Emergence
    • Prevention of coughing/vomiting and protection of airway are conflicting priorities
    • Extubate awake in lateral position
    • Give narcotic and antiemetic before emergence

Kindly provided by Dr James Mitchell from his pharmacodynamics series


ArticleDate:20060829
SiteSection: Article
 
   
    
                                            
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