Anorexia nervosa

Question 1

Anorexia nervosa

Answer 1

A psychiatric eating disorder characterised by a severe restricition of energy intake due to an intense fear of gaining weight. Can be restrictive or binge eating and purging.

A low BMI is not part of the diagnosis but is commonly seen,

Question 2

Physiological considerations for patients with anorexia

Answer 2

Airway
- Poor dentition
- Pneumomediastinum from vomiting

Respiratory
- Hypoventilation
- Aspiration pneumonia

Cardiovascular
- Hypotension
- Bradycardia
- Arrhythmias
- High systemic vascular resistance

Neurological
- Neuropathies
- Seizures

Renal
- CKD
- Dehydration
- Electrolyte disturbance
- Metabolic alkalosis
- Renal stones

MSK
- Muscle wasting
- Osteoporosis

GI
- Delayed gastric emptying
- Gastric perforation
- Superior mesenteric artery syndrome

Hepatic
- Acute liver failure
- Hypoglycaemia

Haematological
- Anaemia
- Bone marrow suppression
- Clotting disorders due to reduced vit K

Question 3

Preoperative assessment of anorexia

Answer 3

Airway
- Dentition
- Consider risk of tracheal stenosis in vomiting

Cardiovascular
- ECG and ECHO
- Orthostatic hypotension

Renal
- Calculate CrCl don’t rely on the actual Cr or eGFR as it will overestimate
- Electrolyte check

• Check TFTs, blood glucose
• Generally day case is a bad idea due to refeeding risk and electrolyte abnormalities

Question 4

Intraoperative respiratory and cardiovascular considerations in patients with anorexia

Answer 4

• Consider RSI if delayed gastric emptying
• Maintain normal physiological pH, patients are often alkalotic and worsening this will cause hypokalaemia and risk arrhythmia
• Careful fluid management, these patients are peripherally vasoconstricted with a low cardiac output, too much fluid can lead to acute heart failure

Question 5

Pharmacological consequences of anorexia

Answer 5

Absorption
- Delayed orally
- Unpredictable IM or sc due to lack of fat and muscle mass

Distribution
- Lack of fat likely to mean lipophilic drug increased fraction in plasma
- Reduced protein binding
- TCI models are not accurate in very low muscle and fat mass and may lead to under or overdosing of propofol - use EEG is using

Metabolism & Excretion
- Reduced basal metabolic rate slower metabolism
- Reduced renal and liver function common

Question 6

Postoperative complications in anorexic patients

Answer 6

• Hypothermia
• Reduced consciousness and coma: electrolyte abnormalities and hypoglycaemia
• Arrhythmias
• Seizures
• Neuropathies and weakness
• Refeeding syndrome

Question 7

Refeeding syndrome

Answer 7

• Occurs when calories are reintroduced to a patient in a catabolic state
• Glucose is available in larger quantities and is rapidly converted to pyruvate (glycolysis)
• This process uses large amounts of phosphate and thiamine (vit B1)
• Insulin secretion also increases leading to large intracellular shifts in K, Mg and PO4
• This results in hypophosphatemia: weakness, arrhythmias, cardiac failure
• Lactic acidosis
• Wernicke encephalopathy

Question 8

Prevention of refeeding syndrome

Answer 8

• Thiamine supplementation
• K, Mg and PO4 monitoring and supplementation
• 10-20kcal/kg for the 1st 24hrs
• Increase by 33% every 24-48hrs
• Monitor vital signs and electrolytes (BD for the first 72hrs)