Anaesthesia and endocrine disease Flashcards
Classify and define the different types of diabetes mellitus
- Type 1: absolute insulin deficiency ( 5%)
1A - Autoimmune destruction of beta cells
1B - Idiopathic destruction of beta cells - Type 2: Spectrum of relative insulin deficiency and insulin resistance (90%)
3. Other causes (<5%) A - Genetic defects beta cells B - Genetic defects insulin action C - Diseases of the pancreas D - Endocrinopathies E - Drug/Chemical induced F - Infections G - Uncommon forms of immune mediated diabetes H - Other genetic syndromes ass. with diabetes
- Gestational diabetes: Relative insulin deficiency in the face of insulin resistance induced by placental hormones (oestrogen/prolactin/cortisol/progesterone)
- < 5% of pregnant woman
- Also: increased food intake
What is the estimated % of South Africans with type 2 DM remain undiagnosed
45%
What are the two most common UNDERLYING causes of death in South Africans
- TB
2. DM
What is normal fasting glucose range
4.5 - 6.0 mmol/L
What is the normal random glucose range
4.5 - 7.7 mmol/L
what is the definition of impaired fasting glucose
6.1 - 6.9 mmol/l
what is the definition of impaired glucose tolerance
7.8 - 11.0 mmol/l
what is the definition of hypoglycaemia in an awake diabetic patient
< 4.0 mmol/l
what is the definition of hypoglycaemia in an anaesthetised diabetic patient
< 6.0 mmol/l
What are the criteria used for the diagnosis of diabetes
Requires 1 of 4 of the following criteria
- Random glucose > 11.1 mmol/l
- Fasting glucose > 7.0 mmol/l
- Oral glucose tolerance test > 11.1 mmol/l
- HbA1C > 6.5%
Classify the complications of diabetes with reference to anaesthesia
Macrovascular
- CVA
- CAD
- PVD
Microvascular
- Retinopathy
- Nephropathy
- Neuropathy (ANS instability/gastroparesis)
Musculoskeletal
- Limited joint mobility (Chiroarthropathy) - Mouth opening and neck extension
Immunodeficiency
- Hyperglycaemia impairs neutrophils
Diabetic foot disease
- Neuropathy + PVD + Impaired immunity
Which complication of diabetes is directly related to the anaesthetic
- Cardiac autonomic neuropathy
- Intra-operative ANS instability - Gastroparesis diabeticorum
- Aspiration risk
What is perioperative hyperglycaemia in the absence of diabetes called, how often does it occur and what determines its occurence
Stress hyperglycaemia
Overall prevalence 33%
Prevalence depends on degree of surgical stress (80% for cardiac surgery)
Do patients who develop stress hyperglycaemia develop diabetes
The majority of these patients will go on to develop DM by 1 year after surgery
How does blood sugar inform with regard to prognosis
Poor HbA1C
Severity of hyperglycaemia on admission
Hyperglycaemia during hospital stay
—> All associated with increased perioperative complications and increased perioperative mortality
Insulin dependent DM: doubles the risk of in hospital mortality
Describe the pathophysiology of perioperative/stress hyperglycaemia
Stressors
- Tissue trauma at surgery
- Fasting
- Perioperative hypothermia
- Pain and anxiety
- Sleep deprivation
- Absence of regional anaesthesia
Stressors –> endocrine response (counter-regulatory hormones)
- Cortisol
- Growth Hormone
- Glucagon
- Catecholamines
Counter-regulatory hormones –> metabolic effects
- Increase gluconeogenesis
- Decrease insulin production
- Increase lipolysis –> ffa’s
- Protein catabolism
Counterregulatory hormones –> immune effects
- TNF-alpha
- IL 1 and IL 6
- –> proinflammatory mediators that impair immune response and alter insulin action increasing insulin resistance.
How long does the stress response to surgery continue in the postoperative period?
6 - 21 days
On what factors does extent of the preoperative work up depend in a diabetic patient
- Invasiveness of surgery
- Diabetic control (HbA1C and TOD)
- Physiological and functional baseline (co-morbidities)
- Recent workup results
What is the HbA1C cutoff for elective surgery
8.5%
What is the target for capillary blood glucose in the perioperative period
6 - 12 mmol/l (tight control is associated with hypoglycaemic events)
List the different groups of antidiabetic agents
- Insulin sensitisers (Increase insulin S)
- Secretogogues (Increase insulin secretion and S)
- Incretins (Increase glucose dependant insulin secrtn)
- Renal glucose reabsorption (decreased)
- GIT glucose absorption (decreased)
- Insulins
List the insulin sensitisers and key aspects of this group of drugs related to anaesthesia
- Biguanides
- Metformin (risk of lactic acidosis in renal failure) - Glitazones
- Pioglitazone (risk of hepatotoxicity)
Cannot cause hypoglycaemia
Omit on the day of surgery
List the secretogogues and key aspects of this group of drugs related to anaesthesia
- Sulphonylureas
- Glibenclamide
- Gliclazide
- Glimepiride - Meglitanides
- Repaglinide
- Nateglinide
Risk of severe hypoglycaemia
Omit while fasting
Restart when tolerating meals
List the incretins and key aspects of this group of drugs related to anaesthesia
- GLP 1 analogues
- Exenatide
- Liraglutide - DPP-4 inhibitors / Gliptins
- Sitagliptin
- Saxagliptin
- Vildagliptin
Concern for delayed gastric emptying
May offer better perioperative glucose control
Does not cause hypoglycaemia
List the drugs that effect renal glucose reabsorption key aspects of this group of drugs related to anaesthesia
SGLT- 2 inhibitors / Gliflozins
- Empagliflozin
- Dapagliflozin
Risk of euglycaemic ketoacidosis (DKA at lower than expected blood glucose levels)
Omit on day of surgery
List the drugs that effect GIT glucose reabsorption key aspects of this group of drugs related to anaesthesia
Alpha-glucosidase inhibitors
- Acarbose
Severe flatulence/bloating/diarrhoea
Omit day of surgery
What are the best strategies for perioperative glucose control
WARD
Basal-bolus regime
- Long acting insulin PLUS rapid acting prandial and correction doses
HIGH CARE / ICU
Variable rate intravenous insulin infusion (protocol) (with 5% dex infusion)
Why is monotherapy with insulin sliding scale inadequate
It offers inadequate blood glucose control and exposes the patient to risk of insulin drug errors.
List a practical insulin classification
- Rapid acting analogue insulin (10 mins | 2 hrs)
- Aspart (Novorapid)
- Glulisine (Apidra)
- Lispro (Humalog) - Short acting regular human insulin (30 mins | 6 hrs)
- Actrapid
- Humulin-R - Intermediate acting human insulins (2 hrs | 18 hrs)
(BASAL)
- NPH (Neutral Protamine Hagedorn)
- Humulin-N (Protophane) - Long acting analogue insulins (4 hours | 24 hrs)
- Glargine (Lantus) - Pre-mixed human insulins (30 mins | 12 hrs)
(BIPHASIC)
- Actraphane (30/70 Regular/NPH)
- Humulin-N 30/70 - Pre-mixed analogue insulins (10 mins | 16 - 24 hours)
- Novomix (rapid acting + basal biphasic aspart)
- Humalog Mix25 (Biphasic Lispro)
How do beta blockers effect hypoglycaemic events
Make patients unaware of hypoglycaemic events
What are the normal features of hypoglycaemia. What is the Rx of hypoglycaemia
SNS response symptoms
- Irritability
- Anxiety
- Abnormal behaviour
- Palmer sweating
- Cool, clammy skin
- Pallor
- Tachycardia
Rx awake: Coke / Juice / Glucogel
Rx asleep: 25 g dextrose IVE repeat CBG in 30 mins
Define and describe diabetic ketoacidosis
Acute, life-threatening, HAGMA driven by formation of ketone bodies from fatty acid metabolism due to absolute or relative insulin insufficiency.
Typically evolves over 24 hours
Precipitated by a physiological stressor (infection / trauma / surgery / MI / New T1DM / Insulin withdrawal)
Polyuria / Polydipsia / Drowsiness / N, V / Abdominal pains / kussmaul respiration
Profound dehydration with severe whole body K depletion
How is a diagnosis of DKA made?
Ketonuria >2 + dipstix (or ketonaemia > 3 mmol/L) PLUS CBG > 11.1 mmol/L (or known DM) PLUS s-HCO3- < 18 mmol/L (or pH < 7.30)
Summarise the management of DKA
ABCDEs
Monitoring: Glucose/electrolytes/pH 2 - 4 hrly until stable
- Fluids
- Target UO 0.5 ml/kg/hr
- 1L over 1 hr then 1L over 2 hours then 1L over 4 hours etc
- If Na > 150 or Hgt < 15 then switch to D10W at 100 ml/hr - Electrolytes
- K < 3.0: add 40 mmol KCl to each liter
- K 3 - 4: add 30 mmol
- K 4 - 5: add 20 mmol
- K 5 - 5.5 add 10 mmol
- K > 5.5: no KCl
PO4 - use K2PO4 instead of KCl if PO4 low
Ca and Mg may also need replacing
- Insulin
- Delay until K is > 3.5 mmol/L
- IV 10U stat then 10 U hourly
- Target: lower glucose by 5mmol/L per hour
- Continue insulin despite glucose control if HAGMA persists but use D10W, KCl and Insulin. - Acidosis
- If pH <7.0 and K is >4 then consider NaHCO3
- 50 ml NaHCO3 8.5% + 200 ml NaCl 0.45% + KCl 10 mmol over 1 hour. - Precipitant
- Infection (remember Pyelonephritis, Cholecystitis)
- Infarction
- Ischaemia
- Ignorance
- Intoxication
- Implantation (Pregnancy)
Tabulate the differences between HHS and DKA
DKA (HHS)
- CBG > 11.1 (>33.0)
- pH < 7.30 (>7.30)
- HCO3 < 18 (>18)
- Ketones > 3.0 + prominent ketonuria (<0.6 and trace)
- Osmolarity variable (>320 mosmol/kg)
- AG raised (variable in HHS)
- CNS altered only if severe (almost alway altered in HHS)
When should glucose be measured after Rx of hypoglycaemia
- 15 - 30 mins after Rx
How frequently should blood glucose be measured in perioperative period
Intraop –> Hourly
CBG outside 6 - 10 mmol/L –> hourly
CBG within 6 - 10 mmol/L on insulin infusion –> 2 hrly
While fasting in surgical ward –> 4 hrly
–> NB before every meal as the premeal CBG is used to calculate the correction dose (per sliding scale) that should be added to the patients regular prandial dose
What are the major categories regarding the effect of thyroid disease on anaesthetics
Hormone effects
Airway management
Describe the effects of deficient thyroid hormone relevant to anaesthesia
A - Deviation/impingement/infiltration
B - Decreased spontaneous ventilation
C - Depressed myocardial function/baroreceptors
D - Cognitive/Affective/Psychotic dysfunction
E - Impaired thermoregulation
F - Reduced plasma volume, hyponatraemia
G - Hypoglycaemia / GIT - ileus - aspiration risk
H - Anaemia
I - Increased susceptibility to Infection
J - Difficult venous access
K - Low RBF, Low GFR
L - Impaired hepatic drug metabolism
M - Monitoring: sedatives ± OSA
In the case of a poorly controlled hypothyroid patient, how is the anaesthetic management affected
- Careful invasive cardiac monitoring and control of ventilation
- Drugs
- Sedative and opioid sparing anaesthesia
- Regional where possible - Rx and prevent hypothermia
- Hydrocortisone (higher incidence of adrenocortical insufficiency)
What are the features of myxoedema coma
- TSH high and T4 low in primary hypothyroidism
- Low TSH and Low T4 in 1 pituitary failure
A - ± Goitre B - hypoventilaiton C - ECG: bradycardia / low voltage complexes / T wave abnormalities / prolonged PR / Pericarial effusion D - Lethargic and disorientated E - Hypothermia F - Low plasma volume / hyponatraemia G - Hypoglycaemia / GIT - ileus H - Anaemia I - LRTI J - Difficult access K - Low RBF, Low GFR L - Decreased drug clearance M - Monitoring - ICU O - Oedema: pericardial/pleural effusions
What are the key features of Rx of myxoedema coma
SUPPORTIVE (Address ABCDE etc.) in ICU
TEMPERATURE: Aggressive rewarming may lead to vasodilation and hypotension.
SODIUM
- Rx severe hyponatraemia with hypertonic saline (2.7% 200 ml bolus initially)
- DO NOT increase Na by more than 12 mmol/L in a 24 hour period.
ADRENALS
- Adrenal insufficiency is common: Hydrocortisone 100mg IV 8 hrly
THYROID HORMONE
- too much –> myocardial ischaemia
- too little –> under Rx
In which population is hyperthyroidism more common and by what factor
10 x more common in woman
Describe the clinical syndrome of hyperthyroidism relevant to anaesthesia
A - Goitre - airway
B - N/A
C - AF, HF , HPT, IHD
D - Hyperactivity/Anxiety/ Psychosis/dysphoria
E - Hyperthermia / Weight loss / Tremor / Prox muscle weakness / heat intolerance
F - Excessive sweating
How long do anti-thyroid drugs take to work?
2 months
What is used for acute symptomatic treatment of hyperthyroidism
Beta blockers
How does the hypermetabolic state associated with hyperthyroidism affect the anaesthetic
Hypermetabolic state increases clearance and volume of distribution of drugs and will affect drug doses and infusion rates if TIVA technique is preferred.
What is the incidence of Thyroid storm in patients with hyperthyroidism and what is the mortality
Incidence is 1 - 2%
Mortality is 10 -20% (Delayed Rx –> 75%)
What are the principles of management of thyroid storm
- ABCDE supportive Rx in ICU
- Anti-thyroid drugs to inhibit thyroid hormone synthesis
- Drugs to counteract the peripheral effect of thyroid hormone
Which receptors do the following beta blockers work
Esmolol Labetolol Carvedilol Atenolol Metoprolol
Esmolol B1 Labetolol A1, B1, B2 Carvedilol A1, B1, B2 Atenolol B1 (B2 at high doses) Metoprolol B1
Summarise the treatment of thyroid storm
- Find and treat precipitant
- Supportive care, ABCDE, ICU
- BETA BLOCKER (Propranolol)
- THIONAMIDE (Block de novo thyroxine production)
- Propylthiouracil (PTU) (Blocks T4 –> T3 conversion)
- Methimazole (Less hepatotoxic, longer half life)
- Carbimazole - WAIT FOR 1 HOUR for THIONAMIDE TO WORK (Prevent iodine from being used for new T4 synthesis)
- IODINE (Lugol’s solution) (blocks release of T4 from thyroid)
- DEXAMETHASONE - block peripheral conversion of T4 to T3
- CHOLECYSTYRAMINE - block recycling of thyroid hormone excreted into bile
When is radioactive iodine considered in hyperthyroidism
In Graves disease to prevent recurrence of severe thyrotoxicosis.
Surgery is the alternative in patients with a very large obstructive goitre.
What is subclinical thyroid disease and how does this impact perioperative decision making?
Abnormal TSH with normal T4 and T3 and no clinical symptoms of thyroid disease.
No reason to postpone.
List the complications of retrosternal extension of a goitre
- Airway obstruction
- Positional dyspnoea
- Hoarseness / choking - Caval obstruction
- SVC syndrome / thrombosis - Arterial obstruction
- Cerebral hypoperfusion (thyrocervical steal) - GIT obstruction
- Dysphagia - Neuropathy
- Phrenic
- Recurrent laryngeal
- Horner’s syndrome
What are three important postoperative considerations following thyroid surgery
- ASSESS VC FUNCTION (DL / LMA FOS)
- Bilateral VC paralysis –> postop stridor requiring re-intubation and ultimately tracheostomy - AVOID COUGHING
- Post-op hematoma and airway compromise - VALSALVA PATIENT for 10 - 20 seconds
- allows surgeon to assess for adequate hemostasis after resection before wound closure.
Why is surgery for malignant lesions higher risk
Increased risk of injury to the recurrent laryngeal nerve
Increased risk of bleeding
What are the four types of thyroid cancer and what anaesthetic relevance does each type have
Papillary
- Spread to LNs requiring radical neck dissection
Follicular
- Spread to lungs and bone: mets may secrete thyroxine
Medullary
- associated with MEN II syndrome and phaeochromocytoma
- Spread to LNs requiring radical neck dissection
Anaplastic
