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Anaesthesia and endocrine disease Flashcards

1
Q

Classify and define the different types of diabetes mellitus

A
  1. Type 1: absolute insulin deficiency ( 5%)
    1A - Autoimmune destruction of beta cells
    1B - Idiopathic destruction of beta cells
  2. 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
  1. 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
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2
Q

What is the estimated % of South Africans with type 2 DM remain undiagnosed

A

45%

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3
Q

What are the two most common UNDERLYING causes of death in South Africans

A
  1. TB

2. DM

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4
Q

What is normal fasting glucose range

A

4.5 - 6.0 mmol/L

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5
Q

What is the normal random glucose range

A

4.5 - 7.7 mmol/L

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6
Q

what is the definition of impaired fasting glucose

A

6.1 - 6.9 mmol/l

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7
Q

what is the definition of impaired glucose tolerance

A

7.8 - 11.0 mmol/l

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8
Q

what is the definition of hypoglycaemia in an awake diabetic patient

A

< 4.0 mmol/l

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9
Q

what is the definition of hypoglycaemia in an anaesthetised diabetic patient

A

< 6.0 mmol/l

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10
Q

What are the criteria used for the diagnosis of diabetes

A

Requires 1 of 4 of the following criteria

  1. Random glucose > 11.1 mmol/l
  2. Fasting glucose > 7.0 mmol/l
  3. Oral glucose tolerance test > 11.1 mmol/l
  4. HbA1C > 6.5%
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11
Q

Classify the complications of diabetes with reference to anaesthesia

A

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

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12
Q

Which complication of diabetes is directly related to the anaesthetic

A
  1. Cardiac autonomic neuropathy
    - Intra-operative ANS instability
  2. Gastroparesis diabeticorum
    - Aspiration risk
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13
Q

What is perioperative hyperglycaemia in the absence of diabetes called, how often does it occur and what determines its occurence

A

Stress hyperglycaemia
Overall prevalence 33%
Prevalence depends on degree of surgical stress (80% for cardiac surgery)

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14
Q

Do patients who develop stress hyperglycaemia develop diabetes

A

The majority of these patients will go on to develop DM by 1 year after surgery

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15
Q

How does blood sugar inform with regard to prognosis

A

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

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16
Q

Describe the pathophysiology of perioperative/stress hyperglycaemia

A

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.
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17
Q

How long does the stress response to surgery continue in the postoperative period?

A

6 - 21 days

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18
Q

On what factors does extent of the preoperative work up depend in a diabetic patient

A
  1. Invasiveness of surgery
  2. Diabetic control (HbA1C and TOD)
  3. Physiological and functional baseline (co-morbidities)
  4. Recent workup results
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19
Q

What is the HbA1C cutoff for elective surgery

A

8.5%

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20
Q

What is the target for capillary blood glucose in the perioperative period

A

6 - 12 mmol/l (tight control is associated with hypoglycaemic events)

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21
Q

List the different groups of antidiabetic agents

A
  1. Insulin sensitisers (Increase insulin S)
  2. Secretogogues (Increase insulin secretion and S)
  3. Incretins (Increase glucose dependant insulin secrtn)
  4. Renal glucose reabsorption (decreased)
  5. GIT glucose absorption (decreased)
  6. Insulins
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22
Q

List the insulin sensitisers and key aspects of this group of drugs related to anaesthesia

A
  1. Biguanides
    - Metformin (risk of lactic acidosis in renal failure)
  2. Glitazones
    - Pioglitazone (risk of hepatotoxicity)

Cannot cause hypoglycaemia
Omit on the day of surgery

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23
Q

List the secretogogues and key aspects of this group of drugs related to anaesthesia

A
  1. Sulphonylureas
    - Glibenclamide
    - Gliclazide
    - Glimepiride
  2. Meglitanides
    - Repaglinide
    - Nateglinide

Risk of severe hypoglycaemia
Omit while fasting
Restart when tolerating meals

24
Q

List the incretins and key aspects of this group of drugs related to anaesthesia

A
  1. GLP 1 analogues
    - Exenatide
    - Liraglutide
  2. DPP-4 inhibitors / Gliptins
    - Sitagliptin
    - Saxagliptin
    - Vildagliptin

Concern for delayed gastric emptying
May offer better perioperative glucose control
Does not cause hypoglycaemia

25
Q

List the drugs that effect renal glucose reabsorption key aspects of this group of drugs related to anaesthesia

A

SGLT- 2 inhibitors / Gliflozins

  • Empagliflozin
  • Dapagliflozin

Risk of euglycaemic ketoacidosis (DKA at lower than expected blood glucose levels)
Omit on day of surgery

26
Q

List the drugs that effect GIT glucose reabsorption key aspects of this group of drugs related to anaesthesia

A

Alpha-glucosidase inhibitors
- Acarbose

Severe flatulence/bloating/diarrhoea
Omit day of surgery

27
Q

What are the best strategies for perioperative glucose control

A

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)

28
Q

Why is monotherapy with insulin sliding scale inadequate

A

It offers inadequate blood glucose control and exposes the patient to risk of insulin drug errors.

29
Q

List a practical insulin classification

A
  1. Rapid acting analogue insulin (10 mins | 2 hrs)
    - Aspart (Novorapid)
    - Glulisine (Apidra)
    - Lispro (Humalog)
  2. Short acting regular human insulin (30 mins | 6 hrs)
    - Actrapid
    - Humulin-R
  3. Intermediate acting human insulins (2 hrs | 18 hrs)
    (BASAL)
    - NPH (Neutral Protamine Hagedorn)
    - Humulin-N (Protophane)
  4. Long acting analogue insulins (4 hours | 24 hrs)
    - Glargine (Lantus)
  5. Pre-mixed human insulins (30 mins | 12 hrs)
    (BIPHASIC)
    - Actraphane (30/70 Regular/NPH)
    - Humulin-N 30/70
  6. Pre-mixed analogue insulins (10 mins | 16 - 24 hours)
    - Novomix (rapid acting + basal biphasic aspart)
    - Humalog Mix25 (Biphasic Lispro)
30
Q

How do beta blockers effect hypoglycaemic events

A

Make patients unaware of hypoglycaemic events

31
Q

What are the normal features of hypoglycaemia. What is the Rx of hypoglycaemia

A

SNS response symptoms

  1. Irritability
  2. Anxiety
  3. Abnormal behaviour
  4. Palmer sweating
  5. Cool, clammy skin
  6. Pallor
  7. Tachycardia

Rx awake: Coke / Juice / Glucogel
Rx asleep: 25 g dextrose IVE repeat CBG in 30 mins

32
Q

Define and describe diabetic ketoacidosis

A

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

33
Q

How is a diagnosis of DKA made?

A 
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)
34
Q

Summarise the management of DKA

A

ABCDEs
Monitoring: Glucose/electrolytes/pH 2 - 4 hrly until stable

  1. 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
  2. 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

  1. 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.
  2. 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.
  3. Precipitant
    - Infection (remember Pyelonephritis, Cholecystitis)
    - Infarction
    - Ischaemia
    - Ignorance
    - Intoxication
    - Implantation (Pregnancy)
35
Q

Tabulate the differences between HHS and DKA

A

DKA (HHS)

  1. CBG > 11.1 (>33.0)
  2. pH < 7.30 (>7.30)
  3. HCO3 < 18 (>18)
  4. Ketones > 3.0 + prominent ketonuria (<0.6 and trace)
  5. Osmolarity variable (>320 mosmol/kg)
  6. AG raised (variable in HHS)
  7. CNS altered only if severe (almost alway altered in HHS)
36
Q

When should glucose be measured after Rx of hypoglycaemia

A
  1. 15 - 30 mins after Rx
37
Q

How frequently should blood glucose be measured in perioperative period

A

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

38
Q

What are the major categories regarding the effect of thyroid disease on anaesthetics

A

Hormone effects

Airway management

39
Q

Describe the effects of deficient thyroid hormone relevant to anaesthesia

A

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

40
Q

In the case of a poorly controlled hypothyroid patient, how is the anaesthetic management affected

A
  1. Careful invasive cardiac monitoring and control of ventilation
  2. Drugs
    - Sedative and opioid sparing anaesthesia
    - Regional where possible
  3. Rx and prevent hypothermia
  4. Hydrocortisone (higher incidence of adrenocortical insufficiency)
41
Q

What are the features of myxoedema coma

A
  1. TSH high and T4 low in primary hypothyroidism
  2. 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
42
Q

What are the key features of Rx of myxoedema coma

A

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
43
Q

In which population is hyperthyroidism more common and by what factor

A

10 x more common in woman

44
Q

Describe the clinical syndrome of hyperthyroidism relevant to anaesthesia

A

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

45
Q

How long do anti-thyroid drugs take to work?

A

2 months

46
Q

What is used for acute symptomatic treatment of hyperthyroidism

A

Beta blockers

47
Q

How does the hypermetabolic state associated with hyperthyroidism affect the anaesthetic

A

Hypermetabolic state increases clearance and volume of distribution of drugs and will affect drug doses and infusion rates if TIVA technique is preferred.

48
Q

What is the incidence of Thyroid storm in patients with hyperthyroidism and what is the mortality

A

Incidence is 1 - 2%

Mortality is 10 -20% (Delayed Rx –> 75%)

49
Q

What are the principles of management of thyroid storm

A
  1. ABCDE supportive Rx in ICU
  2. Anti-thyroid drugs to inhibit thyroid hormone synthesis
  3. Drugs to counteract the peripheral effect of thyroid hormone
50
Q

Which receptors do the following beta blockers work

Esmolol
Labetolol
Carvedilol
Atenolol
Metoprolol
A 
Esmolol            B1
Labetolol          A1, B1, B2
Carvedilol        A1, B1, B2
Atenolol           B1 (B2 at high doses)
Metoprolol       B1
51
Q

Summarise the treatment of thyroid storm

A
  1. Find and treat precipitant
  2. Supportive care, ABCDE, ICU
  3. BETA BLOCKER (Propranolol)
  4. THIONAMIDE (Block de novo thyroxine production)
    - Propylthiouracil (PTU) (Blocks T4 –> T3 conversion)
    - Methimazole (Less hepatotoxic, longer half life)
    - Carbimazole
  5. WAIT FOR 1 HOUR for THIONAMIDE TO WORK (Prevent iodine from being used for new T4 synthesis)
  6. IODINE (Lugol’s solution) (blocks release of T4 from thyroid)
  7. DEXAMETHASONE - block peripheral conversion of T4 to T3
  8. CHOLECYSTYRAMINE - block recycling of thyroid hormone excreted into bile
52
Q

When is radioactive iodine considered in hyperthyroidism

A

In Graves disease to prevent recurrence of severe thyrotoxicosis.

Surgery is the alternative in patients with a very large obstructive goitre.

53
Q

What is subclinical thyroid disease and how does this impact perioperative decision making?

A

Abnormal TSH with normal T4 and T3 and no clinical symptoms of thyroid disease.

No reason to postpone.

54
Q

List the complications of retrosternal extension of a goitre

A
  1. Airway obstruction
    - Positional dyspnoea
    - Hoarseness / choking
  2. Caval obstruction
    - SVC syndrome / thrombosis
  3. Arterial obstruction
    - Cerebral hypoperfusion (thyrocervical steal)
  4. GIT obstruction
    - Dysphagia
  5. Neuropathy
    - Phrenic
    - Recurrent laryngeal
    - Horner’s syndrome
55
Q

What are three important postoperative considerations following thyroid surgery

A
  1. ASSESS VC FUNCTION (DL / LMA FOS)
    - Bilateral VC paralysis –> postop stridor requiring re-intubation and ultimately tracheostomy
  2. AVOID COUGHING
    - Post-op hematoma and airway compromise
  3. VALSALVA PATIENT for 10 - 20 seconds
    - allows surgeon to assess for adequate hemostasis after resection before wound closure.
56
Q

Why is surgery for malignant lesions higher risk

A

Increased risk of injury to the recurrent laryngeal nerve

Increased risk of bleeding

57
Q

What are the four types of thyroid cancer and what anaesthetic relevance does each type have

A

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

DA (50 decks)

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