Anaesthesia in Special Conditions

Diabetes leads to increased surgical morbidity, mortality and length of hospital stay. Perioperative  Hyperglycemia is associated with increased risk of infection, medical complications and death. The  following shall be considered:   

• Ideally, the elective patient should have a preoperative glycated haemoglobin less than 9% or blood glucose fasting 10 mmol/l of random 13 mmol/l.   
• Screen for nephropathy, cardiac disease, retinopathy and neuropathy and inform surgical team. 
• If on oral hypoglycemic therapy and well controlled and surgery is minor, omit therapy on morning of surgery and resume therapy when eating normally.  
• If  on  insulin  adjust  depending  on  the  type  of  surgery  and  expected  fasting  period  as follows:  
  • Minor surgery (duration < 3hours)   
    • Insulin: in the morning intermediate–acting insulin, 1/2 to 2/3 of total daily dose.   
    • If blood glucose is above 20 mmol/l, give a small dose short–acting insulin.  
    • In the evening give intermediate–acting insulin, 1/3 of daily dose.   
    • Fluid: 5% dextrose (IV), volume according to age. 
    • Blood glucose monitoring: every 1–2 hours’ values between 10–14 mmol/l. 
  • Major surgery (duration > 3hours) Involve a general anesthesia and therefore a period of fasting.   
    • Insulin  and  fluid:  infusion  solution  containing  5%  glucose  and  20  mmol/l  potassium chloride (maintenance volume)   
    • Insulin infusion 0.05 IU/kg/hour. 
    • Blood  glucose  monitoring:  every  1–2  hours;  values  between  6–14  mmol/l,  if  <  5 mmol/l reduce infusion rate, continue infusion therapy intraoperatively.   
    • Post operatively: give 5–10% dextrose (IV) 1 Litre + 20ml potassium chloride + 2/3 of total daily dose of insulin over 8hours and repeat to maintain infusion therapy until  food intake is re–established. 

• Monitor BP, scan monitors for HR, ECG rhythm, EtCO2, temperature
• Provided the patient is adequately oxygenated & ventilated, deepen anesthetic
• Examine patient:
  • Pupils (high ICP)
  • Diaphoresis & flushing (carcinoid, pheochromocytoma, hyperthyroidism)
  • Rigidity (malignant hyperthermia, serotonin syndrome)
  • Bladder distension
  • Hot (thyroid storm, malignant hyperthermia, serotonin syndrome)
• Examine drugs & equipment:
  
  • Potential drug error
  • Possible TIVA or circuit disconnect (awareness)
  • Tourniquet (pain)
  • Equipment error (falsely high reading)

Give:

C: hydralazine (IV) 5-20mg (max 30mg) slow IV push every 20minutes

OR

C: labetalol (IV) 5-20mg every10min (max total 300mg)

OR

S: esmolol (IV) 0.5mg/kg over 1minute; start infusion at 50mcg/kg/min

OR

S: nitroglycerin (IV) 50-100mcg; start infusion at 10mcg/min

Treat underlying cause i.e., pain.

Considerations 

• Risk of perioperative respiratory complications: 
  • Bronchospasm, mucous plugging, pneumothorax, atelectasis, pneumonia 
• Possible pulmonary hypertension & RV failure  
• Need for preoperative optimization: 
  • Treatment of bronchospasm, infection, atelectasis 
• Avoidance of triggers & exacerbating factors: 
  • Avoid general anesthesia, endotracheal intubation, histamine releasing medications, light anesthesia 
• Medication management: 
  • Continue usual inhalers pre-operatively 
    • Stress dose steroids (STEROID COVER) if recent high dose steroid use  

Severe Asthma Exacerbation Treatment Options   

Refer to asthma section. 

Anesthetics 

B: ketamine (briochodilator effect) 
                  OR 

D: propofol(bronchodilator effect) 

Volatiles all are bronchodilators but sevoflurane is likely best choice  

• Always consider noninvasive PPV as rescue before intubation  
• If intubation & ventilation: 
  • Use permissive hypercapnia 
  • Use  low  respiratory  rates:  start  at  10-12  breaths/minute  but  may  need lower 
  • rates  
  • Use prolonged expiratory time (e.g. I: E ratios 1:3, 1:4, or even 1:5)  
  • Tidal volume 6-8cc/kg  
  • FiO₂ to achieve PaO₂>60mm Hg

• Avoid precipitants of sickle cell crisis: 
  • Hypoxia 
  • Vascular stasis 
  • Hypothermia 
  • Hypovolemia/hypotension 
  • Acidosis 
• Optimize perioperative pain control  
• Monitor for: 
  • Vaso-occlusive crisis 
  • Acute chest syndrome 
  • Aplastic crisis 
  • Splenic sequestration syndrome 
  • Right upper quadrant syndrome  

Optimization (in consultation with hematology)   

Risk factors for acute pain crises: 

• Age,  frequency  of  hospitalizations  &/or  transfusions  for  episodes  of  crisis,  evidence  of  organ damage   (e.g., low baseline oxygen saturation, elevated  creatinine, cardiac  dysfunction), history of central nervous system events, concurrent infection 
• Procedural risk for complications: 
  • Low: minor surgery (e.g., inguinal hernia & extremity surgery) 
  • Intermediate: intra-abdominal operations (e.g., cholecystectomy) 
  • High: intracranial & intrathoracic procedures, hip surgery 
• Hematology consult, optimize treatment: 
  • Hydroxyurea to ↑ fetal hemoglobin production 
  • Cancel non-emergent cases if patient experiencing a crisis 
  • IV fluid to avoid dehydration while NPO 
• Preoperative transfusion therapy: 
  • Controversial without good evidence 
  • Purpose is to correct pre-existing anemia, ↓ hemoglobin S concentration & ↑ adult hemoglobin 
  • Consider target hemoglobin 6 -10 for surgery & always have blood available for any surgery 
  • Exchange transfusions are not routinely recommended 
• Treatment of Pain:  
  • Rest, warmth, reassurance, analgesia, fluid replacement: 
  • Oral analgesics may be sufficient for minor attacks 
  • Opioids (IM, SC, IV, PO) 
  • PCA opioids with baseline analgesia provided by background infusion or fentanyl patch 
  • Paracetamol & NSAIDs 
  • NSAIDS particularly good for bone pain 
  • Ketamine as adjunct 
  • Regional blocks as appropriate, epidural use has been reported