Endocrine Flashcards
Where is the pituitary gland located?
Sella turcica of the sphenoid bone
The posterior pituitary (neurohypophysis) releases ADH and oxytocin in response to what?
Neural impulses arising from the hypothalamus
*ADH is synthesized in the supraoptic and paraventricular nuclei of the hypothalamus
Is the posterior pituitary inside or outside the BBB?
List the 4 structures not protected by the BBB.
Outside
- Posterior pituitary
- Pineal gland (secretes melatonin)
- Median eminence of the hypothalamus (connection to pituitary)
- Area postrema (senses toxins, N/V)
What may trigger the release of ADH?
Serum osmolality Pain Stress Hypoxia Anxiety Hyperthermia PPV Beta stimulants Histamine
What is the principle mechanism of anterior pituitary hormonal control?
Is the anterior pituitary connected to the hypothalamus?
Negative feedback
The hypothalamus is connected to the anterior pituitary (and the posterior pituitary) by blood vessels (hypothalamic-hypophyseal portal system)
List the 6 hormones released by the anterior pituitary.
- ACTH
- TSH
- GH
- Prolactin
- LH
- FSH
What inhibits the release of ACTH?
Serum cortisol inhibits by negative feedback the release of CRF from the hypothalamus + ACTH from the anterior pituitary
Diabetes Insipidus
Nephrogenic vs. Central
What would you give to differentiate?
Central - failure to release ADH
Nephrogenic - renal tubules fail to respond to ADH
*Administer DDAVP - if the urine becomes concentrated = central
What are the 2 cardinal features of DI?
- Hypernatremia - hyperosmolality > 300 mOsm/kg
2. Polyuria - large amount of dilute urine (2-15 L/day) - < 200 mOsm/kg
Cause of DI?
Cause of SIADH?
DI - pituitary procedures, transphenoidal hypophysectomy
SIADH - intracranial disease (tumors), carcinoma of the lung, myxedema, porphyria
Which is released in greater quantities…thyroxine (T4) or triiodothyronine (T3)?
T4 (97%)
Most of the T4 is then converted to T3 in the tissues
*T3 is 4x more potent than T4
What is the best initial test of thyroid function?
TSH
The parathyroid gland regulates what 2 electrolytes?
- Ca - increases
2. Phosphate - decreases
What is the role of calcitonin?
Released from thyroid gland
Weak role in calcium homeostasis
Decreases plasma concentration of Ca
Decreases activity of osteoclasts (bone breakdown)
Increases activity of osteoblasts (bone deposition)
*Opposite effects of PTH
What is the classic triad of Grave’s disease?
Goiter +
- Hyperthyroidism
- Exophthalmos
- Dermopathy
When in the perioperative period is thyroid storm most likely to occur?
First 6-18 hours post-op
Tx: cold fluids, digitalis, sodium iodide, cortisol, propranolol, PTU
*May look like MH
Hypothyroidism causes _____ in the infant or child and _______ in the adult.
Cretinism *Large tongue
Myxedema *Cold intolerance
Does hypothyroidism alter MAC?
NO, however recovery from anesthesia may be delayed due to hypothermia, respiratory depression, and slowed drug biotransformation
What is the bone disorder caused by hyperparathyroidism?
Osteitis fibrosa cystica
Ca leaks OUT of the bone
Broken, brittle bone disease
(The patient with hyperparathyroidism has hypercalcemia)
What gland is both endocrine and excretory?
Pancreas
Pancreatic duct + common bile duct =
Sphincter of Oddi
Empties into the duodenum
What 2 hormones are secreted by the islets of Langerhans?
- Insulin *beta cells
2. Glucagon *alpha cells
What hormone does the pancreatic islet delta cells produce?
Somatostatin
Inhibits GI motility and secretions (HCL)
What 2 tissues do NOT need insulin to utilize glucose?
- CNS
2. RBCs
What is the expected pattern during and after resection of an insulinoma?
Hypoglycemia during resection
Hyperglycemia after resection
What are the 3 ketones produced in the patient with DM?
- Acetoacetic acid
- Beta-hydroxybutyric acid
- Acetone
W/o insulin, glucose can’t get into the cells - carbs are not available, so fatty acids become available - these fatty acids are oxidized in the liver to ketones
What is the most common cause of death during treatment of ketoacidosis?
K swings
*Type 1 DM
The diabetic with autonomic neuropathy is at increased risk for perioperative morbidity and mortality. What are 6 anesthetic concerns?
- Orthostatic hypotension
- Silent MI
- Gastroparesis
- Atlanta-occipital joint immobility
- Renal insufficiency
- HTN
*The HR response to antimuscarinics and beta blockers is blunted
Hyperosmolar Hyperglycemic Nonketotic Diabetic Coma
Deficient insulin response to glucose stimulation
Severe dehydration
BS may reach 1,000 mg/dL
Needs to be slowly corrected or else cerebral edema
*Type 2 DM
What hormone is secreted by the zona glomerulosa of the adrenal cortex?
Aldosterone
*Acts on the DT and CD to increase Na reabsorption and increase K secretion
What hormone is secreted by the zona fasiculata of the adrenal cortex?
Cortisol
*ACTH controls the secretion of cortisol (anterior pituitary)
Causes increase in glucose, sodium retention, potassium excretion
The adrenal medulla secretes what 3 catecholamines?
- NE
- Epi
- Dopamine
* Under the control of the SNS - Ach release from the preganglionic cholinergic fibers
* Chromaffin cells
What is the final metabolic product of catecholamine metabolism?
Vanillylmandelic acid
Cushing’s Syndrome
aka hyperadrenocorticism
Excessive cortisol
Most cases d/t over-production of ACTH by the anterior pituitary
S/S: HYPERtension, HYPERglycemia, HYPOkalemia, skin pigmentation, weakness, moon face, buffalo hump
What is the most common cause of secondary adrenal insufficiency?
Iatrogenic administration of exogenous glucocorticoids
*Depresses ACTH release from the anterior pituitary, adrenal cortex atrophies
Addison’s Disease
aka primary adrenal insufficiency
aka hypoadrenocorticism
Autoimmune destruction of the adrenal cortex - impaired secretion of aldosterone and cortisol
S/S: HYPOtension*, HYPOnatremia, HYPOglycemia, HYPERkalemia, hemoconcentration (water follows Na secretion), skin pigmentation, weight loss, weakness (opposite of Cushing’s)
What disease is associated with hypersecretion of aldosterone by the adrenal cortex?
Conn’s syndrome
aka primary hyperaldosteronism
What drug releases catecholamines from the adrenal medulla and inhibits catecholamine uptake into chromaffin granules?
Droperidol
*Avoid with a pheo - What else should be avoided?
Histamine-releasing drugs (Histamine triggers the release of catecholamines)
Ketamine
Where are Kupffer cells found? What are their function?
Macrophages that line the sinusoids of the liver
What is the portal triad?
- Portal vein
- Hepatic artery
- Bile duct
Can the liver act as a reservoir of blood?
YES, the liver is a major reservoir for blood, storing up to 500 mL of blood
When portal vein BF decreases, hepatic arterial BF increases. What is this phenomenon called?
Arterial buffer response
Maintains hepatic O2 supply and BF
What % of hepatic BF is provided by the portal vein? Hepatic artery?
Portal vein - 70% (10 mmHg)
Hepatic artery - 30% (90-100 mmHg)
*Each provide 50% of total oxygen
What 2 vessels converge to form the hepatic portal vein?
- Splenic vein
- Superior mesenteric vein
*Hepatic artery arises from celiac artery
What are 3 likely hematologic abnormalities seen in chronic alcoholics?
- Thrombocytopenia
- Leukopenia
- Anemia - megaloblastic
When do manifestations of severe alcohol withdrawal syndrome usually appear?
24-96 hours (1-4 days) after cessation of drinking
Tx: Librium (long-acting benzo)
The patient has hepatic cirrhosis. What is the significance of this for the anesthetist?
Portal vein has decreased flow
Hepatic arterial flow is usually maintained
Avoid situations that decreased hepatic artery flow and oxygen delivery - optimize BP
Isoflurane maintains hepatic blood flow the most!
What is the most common major complication of cirrhosis?
Ascites
*Portal HTN promotes the formation of ascites
How would you dose NDMR in a patient with cirrhotic liver disease?
Greater initial loading dose, but smaller maintenance doses
Increased Vd, prolonged clearance
What is the major cause of M and M in the patient with cirrhosis?
Gastroesophageal varices
What 2 lab tests are best in evaluating liver disease?
- Serum albumin (1/2 life = 20 days - chronic)
2. Prothrombin time
Which enzyme test best assess hepatocelluar damage?
5-NT
GST
ALT
AST
What happens to the following in the patient with hepatic cirrhosis: SVR CO BV Portal blood flow Hepatic blood flow Plasma osmotic pressure
SVR - decreased CO - increased BV - increased (d/t activation by RASS) Portal blood flow - decreased Hepatic blood flow - unchanged or decreased Plasma osmotic pressure - decreased
*Hyperdynamic state
Porphyria Attack
S/S
Triggers
Metabolic disorders that affect the biosynthesis of heme
S/S: abdominal pain, N/V, autonomic disturbances, sweating, tachycardia, HTN
Triggers: barbs, possibly benzos and Ketamine
Others: etomidate, enflurane, nifedipine, sulfa, ketorolac, pentazocine, phenytoin, hydralazine, mepivacaine, lidocaine
*Regional anesthesia may be avoided to prevent confusion
DM Type 1 Patho
Autoimmune destruction of glucose transporter on islet cells
Pancreas is no longer secreting insulin
Normal insulin production is 50 units/day
Glucose Lowering Agents
Increase insulin release from the pancreas -
Sulfonylureas (Chlorpropamide)
Repaglinide
DPP-4 inhibitors (Sitagliptin)
GLP-1 agonists (Exenatide) - lowers glucagon levels
Decrease hepatic glucose release and increase insulin sensitivity-
Thiazolidinediones (Rosiglitazone)
Block starch digesting enzymes -
Alpha-glucose dash inhibitors (Acarbose)
Metformin Associated Lactic Acidosis
Triggers - stress and IV contrast
Hold for 8 hrs preop (24 hrs with extended release use)
Gestational Diabetes
More harmful for mom or baby?
Baby - polyhydramnios, macrosomia, prematurity, RDS, rebound hypoglycemia
Tx - insulin is controversial (it doesn’t cross placenta)
Drug-induced DI - causative agents?
Treatment for DI?
Lithium, amphoterocin, fluoride
ADH replacement - SE: increase in SVR
Chlorpropamide- ADH stimulator - SE: hypoglycemia
Caution with too rapid correction of sodium. Can cause…
Central pontine myelinolysis
1-2 mEq/hr max
Post-op adrenalectomy CXR due to risk of…
Pneumo 20%
Clonidine Suppression Test
Used in the diagnosis of a pheo
0.3 mg will decrease serum catecholamine levels in essential HTN, but NOT with a pheo
Acromegaly
99% from primary pituitary adenoma
Excessive GH from anterior pituitary
Careful assessment of airway
What is the most common GI endocrine tumor?
Carcinoid tumor
Systemically active with metastasis
Releases —
histamine-like substances - hypotension, bronchospasm
serotonin - HTN, hypervolemia
*Preop somatostatin analog octreotide
Innervation of Liver
Sympathetic: T7-10
Parasympathetic: Vagus and R phrenic
Why are bile salts important?
Essential for absorption of cholesterol, fatty acids, and fat soluble vitamins
Hepatic encephalopathy may be reversed by…
Flumazenil
Pulmonary characteristics of a patient with liver failure.
PaO2 50-70 mmHg
Respiratory alkalosis (decreased PaCO2) - hyperventilation
HPV is impaired
Pulmonary characteristics of a patient with liver failure.
PaO2 50-70 mmHg
Respiratory alkalosis (decreased PaCO2) - hyperventilation
HPV is impaired
*Do NOT hyperventilate this patient - NH4+ shifts to NH3 (ammonia — encephalopathy)
3 Phases of Liver Transplant
- Preanhepatic - hemorrhage, hyperglycemia
- Anhepatic - clamping vessels to reperfusion
- Neohepatic - reperfusion, greatest hemodynamic instability
