OR Concepts Flashcards
Where are baroreceptors located?
- Carotid sinuses
- Aortic arch
Carotid sinus
Contains baroreceptors that adjust heart rate to maintain normal cardiac output/blood pressure
Carotid body
Cluster of cells that PRIMARILY sense hypoxia and stimulate faster respirations
Possible causes of a stroke
- Blood clot “Ischemic stroke” 2. Intracranial hemorrhage “Hemorrhagic stroke” 3. Prolonged hypotension (inadequate brain perfusion) 4. Hypertension This leads to stress on the walls of blood vessels and is associated with intracranial hemorrhage
Pulmonary embolism
If the DVT becomes dislodged from the legs, it can move to the heart and lungs (at which point it becomes defined as a pulmonary embolism), which is a life threatening emergency
Percentage of ICF?
65%
Edema
When the patient builds up excess interstitial fluid, it is referred to as “edema” (swelling)
Pulmonary edema
Pulmonary edema refers to a buildup of excess fluid in the alveolar spaces, and it is usually causes by some degree of heart failure (which causes some blood to back up into the lungs)
Preload
Preload refers to the volume of blood that is returning to the right ventricle and available for the heart to pump on the next contraction
Afterload
Afterload refers to the resistance the left ventricle has to pump against can lead to left ventricular hypertrophy Afterload refers to the amount of resistance the left ventricle has to pump against It is proportional to the level of vasoconstriction in the body Vasoconstriction = high afterload Vasodilation = low afterload
How do you measure preload?
An anesthetist can measure preload by monitoring central venous pressure (CVP) CVP is the blood pressure within the superior vena cava (normally 5-12mmHg), and this can be only be measured if an anesthetist places a central line (which is an IV catheter in a large “central” vein (internal jugular, subclavian, etc)
Transmural pressure
Transmural pressure refers to the difference in pressure between two sides of a wall or equivalent separator
Systemic vascular resistance
SVR refers to resistance that the left ventricle must pump against, and it is affected by peripheral arterial vascular tone Arterial vasoconstriction = high SVR, while arterial vasodilation = low SVR
Pulmonary vascular resistance
“PVR” refers to the resistance that the right ventricle must pump against, and is affected by the vascular tone in the pulmonary arteries Pulmonary artery vasoconstriction = high PVR, while pulmonary artery vasodilation = low PVR PVR is normally much lower than SVR, because there is less resistance in the pulmonary circulation
Cautery pen
A cautery pen (“bovie”) is a surgical cutting device that simultaneously cuts tissue and burns/coagulates blood vessels by sending electricity to the surgical area (and to the body)
Unipolar bovie
Unipolar cautery (bovie) provides superior coagulation (compared to bipolar cautery), but: 1. A grounding pad and electrical loop must be in place for it to work 2. More current flows through the body
Bipolar bovie
With bipolar cautery, current does not travel from a bovie tip to a “grounding pad”; it travels from one forceps tip to the other. This means that 1. Much less current will travel through the body 2. A grounding pad is not necessary
Implications Of Pneumoperitoneum (8)
- Intubation is required
- Atelectasis is more likely
- Hypercarbia is more likely
- A vagal response is somewhat common
- Cardiac output decreases
- Blood pressure can go up or down
- Patients can get referred pain in the shoulder
- Possibly cause a partial pneumothorax (collapsed lung)
CO2 gas embolism
Carbon dioxide embolism is a rare but potentially fatal complication of laparoscopic surgery, and can occur with accidental infusion of CO2 into an injured vein or artery It can result in blockage of the right ventricle, and carries a reported mortality rate of 28%
Subcutaneous emphysema
Subcutaneous emphysema refers to trapped air underneath the skin, and can occur during laparoscopic surgery as CO2 diffuses into the subcutaneous space
SubQ emphysema
If, at the end of surgery, EtCO2 remains elevated, and/or there appears to be airway swelling and crepitus (crackling, crinkly, or grating feeling or sound under the skin), extubation may be contraindicated until those symptoms are resolved
Purposes of OG/NG tube
- Can decompress the stomach 2. Can vent gases if patient has a bowel obstruction 3. Can deliver tube feedings directly into the stomach 4. Can empty the stomach of poison or drug overdose
Contraindications for OG tube
Gastric bypass Hx, esophageal varices from chronic liver failure or alcoholism
Anaphylaxis is caused by excess histamine release, and leads to 2 main problems
- Vasodilation (hypotension) If the vasodilation is severe enough, fluid from the vasodilated arteries begins to leak out into the interstitial space, which causes localized edema (hives) 2. Bronchoconstriction (wheezing) and respiratory distress
Anaphylaxis treatment
- Subcutaneous epinephrine
- Bronchodilators (beta 2 agonists)
- Histamine blockers
- Steroid (100mg Hydrocortisone)
Compartment syndrome
Compartment syndrome refers to a decrease in the blood flow (perfusion) to a bodily compartment due to an increase of pressure inside the compartment (which compresses blood vessels)
How can you measure preload?
An anesthetist can measure preload by monitoring central venous pressure (CVP)
Normal CVP
CVP is the blood pressure within the superior vena cava (normally 5-12mmHg), and this can be only be measured if an anesthetist places a central line (which is an IV catheter in a large “central” vein (internal jugular, subclavian, etc)
Low CVP indicates
High CVP indicates
Low CVP indicates low preload (hypovolemia)
High CVP indicates fluid overload (usually in heart failure or renal failure patients)
When can Negative Pressure Pulmonary Edema occur?
- The patient bites down on their endotracheal tube during emergence
- The patient experiences a laryngospasm
In each case, intrathoracic pressure becomes more and more negative as the patient breathes (because air from the atmosphere cannot enter the lungs)
This constant negative pressure from inside the lungs will “suck” blood into the alveoli from the pulmonary capillaries, causing pulmonary edema
