Diabetes and Insulin- physiology focus

Question 1

what do islet of langerhan secrete into circulation

Answer 1

insulin (beta cells), glucagon (alpha cells), somatostatin (delta cells), pancreatic polypeptide (PP cells)

Question 2

glucagon purpose

Answer 2

regulates carbohydrate, fat, protein metabolism

Question 3

insulin purpose

Answer 3

regulates carbohydrate, fat, protein metabolism

Question 4

somatostatin purpose

Answer 4

suppresses growth hormone release

Question 5

pancreatic polypeptide purpose

Answer 5

self-regulate pancreatic secretion activities (endocrine and exocrine)

Question 6

insulin daily levels, half life, metabolism, binding site

Answer 6

daily 40-50 units secreted
t1/2 5min
metabolism: liver and kidneys (80%)
binds to extracellular alpha subunits, intracellular beta subunits

Question 7

insulin MOA

Answer 7

binds to extracellular domain -> conformational change of alpha subunits -> facilitates ATP binding to beta subunits ->phosphorylation ->mediates enzyme activation, inactivation and metabolic signaling

Question 8

insulin genetic makeup

Answer 8

51 amino acid peptide hormone synthesized in beta cells of islets of langerhans as single polypeptide proinsulin, precursor molecule to insulin. proinsulin converted to insulin and c peptide.

Question 9

what reflects functional activity of pancreatic beta cells

Answer 9

plasma concentrations of insulin and c peptide

Question 10

glucagon stimulates and inhibits

Answer 10

stimulates glycogenolysis (breakdown of glucose) and gluconeogenesis (glucose formation) and inhibits glycolysis

Question 11

insulin released in response to

Answer 11

beta adrenergic stimulation or acetylcholine

Question 12

what stimulates insulin release (drugs and metabolic environments)

Answer 12

hyperglycemia, beta agonists, acetylcholine, glucagon

Question 13

what inhibits insulin release (drugs and metabolic environments)

Answer 13

hypoglycemia, beta antagonists, alpha agonists, somatostatin, diazoxide, thiazide diuretics, volatile anesthetics, insulin)

Question 14

glucagon

Answer 14

catabolic hormone that mobilizes fatty acids, amino acids into systemic circulation. principle stimulation for secretion is hypoglycemia. activates adenylate cyclase for cAMP formation. exogenous admin can lead to enhanced myocardial contractility. elimination t 1/2 3-6min

Question 15

IV Insulin t1/2, metabolism, renal considerations

Answer 15

elimination t1/2 5-10min
metabolized in kidneys and liver by proteolytic enzyme. 50% of insulin that reaches liver through portal vein is metabolized.
renal dysfx alters circulating insulin levels more than hepatic disease.
peripheral tissue (skeletal, muscle, fat) can bind to, inactivate insulin

Question 16

insulin SQ duration

Answer 16

30-60min (tightly bound to tissue receptors).

Question 17

insulin anesthetic implications

Answer 17

preoperative morbidity related to preexisting end organ damage
preop chest X-ray may show cardiac enlargement, pulmonary vascular congestion, pleural effusion
increased incidence of ST segment or T wave abnormalities
myocardial ischemia or old infarction may be found on ECG
DM + HTN = 50% likelihood of diabetic autonomic neuropathy
periop CV problems increased with use of ACEI or ARB
diabetic renal dysfx: elevated creatinine and CKD

Question 18

gastroparesis and insulin anesthetic implications

Answer 18

premedicate with nonparticulate acid and metoclopramide. risk factors, old age, DM for greater than 10 years, CAD, BB

Question 19

glycolysation implication

Answer 19

implies limited mobility of joints, ask them to perform the prayer sign. temporomandibular joint and cervical spine mobility should be assessed preoperatively in diabetic patients to assess for risk of difficult intubation

Question 20

hyperglycemia anesthetic implications

Answer 20

associated with hyperrosmolarity, infection, poor wound healing, increased mortality.

Question 21

anesthesia management of diabetic patients

Answer 21

patient takes 2/3 of nighttime insulin (NPH, regular) and 1/2 total morning insulin dose of NPH but regular insulin dose for AM should be held
pump: decrease overnight rate by 30% and keep at basal rate for DOS
if patient takes glargine and lispro/aspart daily, take 2/3 glargine dose and entire lispro/aspart night before. hold AM dosing.
add regular insulin to NS in 1 unit/ml conc and begin at .2-1units/kg/hour. target <180mg/dL

Question 22

how to calculate intraop insulin rate

Answer 22

regular insulin units/hour = plasma glucose/150

Question 23

1 unit of insulin usually lowers plasma glucose by

Answer 23

25-30mg/dL

Question 24

anesthesia management: sulfonylureas and metformin

Answer 24

have long half lives, d/c 24-48h before surgery