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

Anaesthesia for general surgery

Created: 21/8/2006
Updated: 26/7/2021

Thyroid surgery

  • Preoperative
    • Assessment
      • Routine, plus
      • Thyrotoxicosis symptoms
        • Anxiety, tremor, heat intolerance, fatigue, weight loss
        • TFT, Ca2+, FBE, U&E, ECG, CXR, CT if indicated
      • Complications
        • Goitre, atrial fibrillation, SVC obstruction
        • Airway compromise, stridor, tracheomalacia
        • Eye complications of Graves’ disease
      • Treatment
        • Antithyroid drugs, radioactive iodine
          • Complications of therapy: marrow suppression
        • Other therapy: β-blockers
    • Determine fitness for surgery
      • Euthyroid, little risk of thyroid storm
      • Airway and vascular compromise determined and manageable
    • Preparation, premedication, transport
      • Routine
  • Intraoperative
    • Monitoring, access
      • Routine
    • Induction
      • Routine relaxant technique
      • Tube placement commonly armoured tube with circuit over head
        • Care with positioning, secure connections, eye protection
    • Positioning
      • Supine with shoulder roll
    • Maintenance
      • Balanced technique, IPPV
      • Poor access to head and airway
    • Emergence
      • Request from surgeon to check vocal cord movement
        • Often will not change surgical management
        • Requires deep extubation when reversed and laryngoscopy
  • Postoperative
    • Airway distress
      • Upper airway obstruction due to soft tissues and reduced muscle tone
      • Laryngospasm, bilateral cord paralysis
      • Inadequate reversal
      • Wound haematoma
      • Laryngeal oedema
      • Tracheomalacia
      • Anaphylaxis
    • Hypocalcaemia due to hypoparathyroidism
      • May be early (1-3 hours), more commonly 1-3 days

Physiological response to pneumoperitoneum

Intra-abdominal pressure 10-12 cmH2O

  • CVS
    • Venous pooling in legs, IVC compression --> increased RVR, decreased venous return
    • Increased vascular resistance of intra-abdominal organs --> increased SVR
  • Respiratory
    • Decreased compliance, increased intrathoracic pressure on IPPV
  • Neuroendocrine
    • Increased ADH, catecholamines, renin, angiotensin II
    • Increased sympathetic tone
  • Net effect
    • Decreased CO, increased MAP
    • Minimized by filling, head-down position, α2-agonists
  • Regional effects
    • Venous stasis in legs --> DVT
    • PCO2 causes vasodilation if ventilation is not increased (increased ICP)
    • Arrhythmia: bradycardia due to peritoneal manipulation

Bowel resection

  • Preoperative
    • Preoperative considerations
      • Two major patient groups: young inflammatory bowel disease (IBD) and older cancer resections
      • IBD patients typically slim, otherwise well, may be on long-term corticosteroids and opioids
      • Cancer patients may have anaemia, hypercoagulability, hepatic dysfunction from metastases, electrolyte disturbance from secretory adenocarcinomas
      • Bowel preparation may cause dehydration, electrolyte disturbance
    • Physical findings
      • Signs of bowel obstruction if present
    • Work-up
      • Investigation of usual comorbidites in old patients
      • Preoperative investigations as indicated: haematology, electrolytes, liver function, coags
      • Crossmatch
    • Choice of anaesthesia
      • General anaesthesia. Rapid sequence induction indicated in obstructed patients
      • Additional epidural anaesthesia and post-operative analgesia supported by literature: less opioid use, faster wakeup, earlier return of bowel function, diminished inflammatory response, protection against DVT, better respiratory function. Contraindicated in patients with sepsis or coagulopathy. Test prior to induction.
  • Intraoperative
    • Monitors/line placement
      • Potential for substantial bleeding, third-space loss of fluids
      • Large IVs, arterial line, central line, temperature monitor indicated
      • Otherwise routine monitoring: ECG, SpO2, gas analysis
      • Surgeon will commonly request nasogastric tube
    • Intraoperative concerns
      • Positioning, particularly if in lithotomy for perineal approach
      • Fluid shifts
      • Heat loss
      • Usual concerns with stress of surgery in older patients
    • Intraoperative therapies
      • Fluid management guided by CVP, urine output, observed blood loss, duration of surgery. Fluid balance often positive, several litres on paper
      • Active warming of upper body (and legs if possible)
  • Postoperative
    • Postoperative pain
      • Epidural dilute local anaesthetic plus fentanyl by infusion usually provides good analgesia
    • Complications
      • Anastomotic leak may require reoperation
      • Respiratory, cardiac or renal complications in elderly
  • Surgical procedure
    • Indications
      • Bowel cancer
      • Inflammatory bowel disease refractory to medical management
      • Non-malignant disease causing obstruction
      • Ischaemic or non-viable bowel
    • Procedure
      • Laparotomy with resection of affected bowel and its mesentery
      • If anal canal or rectum is to be resected, perineal approach is often required as well
      • Primary anastomosis commonly performed. Two or three stage procedures with temporary or permanent stomas are sometimes required
    • Surgical concerns
      • Dissection in pelvis for low anterior resections may be difficult
    • Typical EBL
      • Highly variable

Kindly provided by Dr James Mitchell from his pharmacodynamics series

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