Quiz 1 - Endocrine and Thermoregulation Flashcards
What is a hormone?
substance which is created by one type of cell that signals a response from another type of cell.
What are some different types of hormones?
- Peptides and protein hormones
- Thyroid hormones
- Catecholemines
- Steroid hormones
Can hormones act on any cell?
No, they need to have the correct receptor
Where are cell receptors for hormones located?
Can be on the surface or within the cell
What regulates the number of hormone receptors on a cell?
the cell’s response to a hormone is what regulates the number of receptors on a cell.
What feedback mechanism controls most hormone activity? Positive or Negative feedback?
Negative feedback
What does homeothermic indicate?
temperature range between 36.5 - 37.3 degrees celsius
When monitoring temperature - in relation to core temperature, how much does the skin temp vary from the core?
May be 3-4 degrees C cooler
How does the Axillary temp vary from core temp?
axillary temp may be 1 degree C cooler
What are some sites for core temp measuring?
- rectum
- esophagus
- Nasopharynx (can create epistaxis)
- External auditory meatus (risk of TM rupture)
- Bladder cath
- Pulm Art Cath
What is considered hypothermic?
core temp less than 36 degrees C
What is considered hyperthermic?
core temp more than 38 degrees C
What is considered normothermic?
37 degress C +/- 1 degree C
Where is temperature regulated in the brain?
Hypothalamus and preoptic nuclei
What are some of the vascular effects of hypothermia?
Vasoconstriction, hypoperfusion, difficult pulse ox readings
What are some of the cardiac effects of hypothermia?
Shivering can increase oxygen consumption by up to 300%
Also causes increased incidence of MI, arrhythmias and cardiac morbidity. VF occurs around 22-23 degrees C
What are some of the pulmonary effects of hypothermia?
PVR increases, decreased ventilatory drive, decreased CO2 in blood
Effects of hypothermia on renal
Cold diuresis –> decreased plasma volume
effects of hypothermia on hepatic
decreased hepatic blood flow
effects of hypothermia on CNS
- CMO2 consumption decreases 7% for each 1 degree C decrease. MAC decreases 5-7% for each 1 degree C change, drowsiness, confusion
effects of hypothermia on hematologic
Impaired platelet function, decreased platelet count, decreased activity of coagulation factors
effects of hypothermia on metabolism
reduced by 50% at 30 degrees C, slows drug metabolism, prolong NM blockade, delayed emergence, prolonged elimination of inhalation agents, increased concentrations in plasma of propofol and fentanyl
effects of hypothermia on healing
- increased healing time leads to increased incidence of wound infection.
- vasoconstriction leads to poor tissue perfusion.
- less penetration of antibiotics to sites.
- Decreased phagocytic activity.
For body temp, what are the 2 compartments and what is the fraction of body temp in both compartments?
- Peripheral compartment (1/3 of heat): Skin, limbs, sub Q tissues
- Core compartment (2/3 of heat): major thoracic and abdominal organs and brain
How are the temperature differences between the core and peripheral compartments maintained?
through vasoconstriction
How much heat production would you created if you were completely insulated from heat loss?
1-2 degrees Celsius per hour
How much can shivering increase heat production?
by 300%
T/F Under normal conditions, body heat is preserved by tonic peripheral vasoconstriction
True
What is the major means of heat loss?
Radiation - accounts for 60% heat loss
T/F: Convection can account for 25% of heat loss in OR’s with forced airflow.
True
T/F: Normal respiration of inspired gases can account for evaporative losses.
True
How much does conduction contribute to heat loss?
< 5%
How is core body temperature regulated?
Peripheral vasoconstriction
T/F: Can general and regional anesthesia inhibit peripheral vasoconstriction
True
How much does the core body temperature decrease after the 1st hour?
1 to 1.5 Celsius
How much can one unit of refrigerated blood or one liter of room temperature crystalloid decrease core body temperature?
0.25 Celsius
How much does basal metabolic rate decrease each year beyond the age of 30?
1 %
As to which age group has the greatest increases surface to mass resulting in rapid heat loss to environment?
Neonate
T/F: Minor shivering in patient in preop is acceptable to warm the patient.
FALSE
Shivering is induced by ________ of the preoptic region of the _____________ which causes the involuntary oscillatory muscular activity.
cooling, hypothalamus
Why is Meperidine most commonly used for post operative shivering?
- Effective
- Partially mediated by kappa opioid receptors
- Decreases shivering threshold twice as much as vasoconstriction threshold
What are some causes of hyperthermia?
- malignant hyperthermia
- sepsis/infection
- thyrotoxicosis
- pheochromocytoma
- hypothalamic lesion,trauma, anoxia
- Neuroleptic malignant syndrome
- transfusion reaction
- medication
What is occurring with a patient that manifests with hypercatabolic state with tachycardia, hypercapnia, muscle rigidity, tachyarrythmias, metabolic acidosis.
Malignant hyperthermia
What would be given preoperative to control hyperthermia?
Acetominophen
What would be done to control hyperthermia intraoperative.
- Cooling the OR
- Forced air cooling
- cooled IV fluids
- Field irrigation with cold fluids
- NG, Bladder irrigation with cooled fluids
What occurs with infection/sepsis to result in hypothermia?
During bacteremia, pyogens cause release of INTERLEUKIN ONE, increasing the set point for temperature in the hypothalamus.
What are some facts about post op shivering?
- Occurs in 40% of unwarmed patient after general anesthesia
- Causes dramatic increases in oxygen consumption and catecholamine release
- 3 times increase in myocardial events.
What are the 4 divisions of the pituitary called?
- Adenohypophysis (anterior)
2 Pars Intermedius (gone after fetal develops)
3 Pars tubularis (vascular but no hormones)
4 Neurohypophysis (posterior)
Where does the pituitary gland rest?
in the Sella Tursica in the sphenoid bone
What does the anterior pituitary (adenohypophyis) regulate?
Thyroid, adrenals, mammary glands, growth hormone, gonads and melanocytes
What are the cells in the anterior pituitary that secrete growth hormones?
Somatotropes (most abundant)
What are the cells called that secrete adenocorticotropic Hormone (ACTH)
Corticotropes
What do the gonadotropes in the anterior pituitary secrete?
Luteinizing Hormone (LH) Follicular Stimulating Hormone (FSH)
What are the cells in the anterior pituitary that secrete ProLactin (PL)?
Lactotropes
What are the two hormones that are secreted by the posterior pituitary (neurohypophysis)?
Oxytocin and vasopressin
Where are hormones synthesized? Where are they secreted?
Hormones are synthesized in the HYPOTHALAMUS and transported intracellularly for secretion from the PITUITARY
What is the dominant site for vasopressin (ADH) synthesis?
Supraoptic nucleus
There are two receptors for vasopressin (V1 and V2). What are their effects when stimulated?
V1 - pressor effect
V2 - ADH effect
What stimulates the release of vasopressin?
plasma osm > 290
What are some signs of SIADH?
Water retention yields a low serum Na, dilute plasma and concentrated urine
What are some causes of SIADH?
CNS disorders, cold stress, trauma, drug induced, squamous cell lung CA
How should you treat SIADH?
find the cause, LIMIT FLUID INTAKE
At what level of Na would you expect to start seeing symptoms of hyponatremia?
125 meq/L - serious symptoms below 120 meq/L
What are some mild, mod, and severe hyponatremia problems?
Mild - anorexia, nausea, weakness
Mod - lethargy, confusion
Severe - Seizures, coma, death
A sodium at what level would be considered safe for surgery and unsafe for surgery?
Above 130 - SAFE
Below 130 - may lead to cerebral edema
Should you correct hyponatremia quickly or slowly? Why?
SLOWLY - rapid correction could lead to CENTRAL PONTINE MYLINOLYSIS
What is Diabetes Insipidus (DI)?
Inability to release ADH (central) or inability to respond to ADH (renal).
Central is most common
What are some signs/symptoms of DI?
Polydipsia and Polyuria without hyperglycemia. H2O intake keeps these pts from severe dehydration.
How is DI treated?
Central - ADH nasal spray (desmopressin)
Renal - demeclocycline
Anesthetic implications for DI
- Increased MAC due to decreased uptake of inhalation agents from decreased CO.
- Hypovolemia requires large doses of IV agents
- postpone elective surgery for Na > 150
Should you correct hypernatremia quickly or slowly?
SLOWLY - rapid correction results in seizures, brain edema, permanent neuro damage and death
Where in the posterior pituitary is oxytocin produced?
Supraoptic Nucleus
How do you mix oxytocin?
20 units to 1 liter crystalloid and titrate to uterine contractions
What is a common sign of pituitary tumor?
Loss of peripheral vision due to compression of optic chiasm.
Can also manifest as systemic effects due to hormonal changes.
What are some anesthesia complications due to pre-existing hormonal disorders?
Acromegaly (GH) - difficult airway
Hyperthyroid (TSH) - tachycardia, weight loss
Cushing disease (ACTH) - difficult airway and access (?)
Panhypopituitaryism - hormone replacement with cortisol, levothyroxine, DDAVP
Pt’s having a transsphenoidal resection of the pituitary may develop DI what are some implications with this?
- Could be temporary or permanent
- May be evident intraop or postop
- Suspect with high urine output
- Confirmed with spec gravity < 1.005
- *Treat with DDAVP 0.5 -1mcg IV or SQ plus volume replacement