General Anesthesia Flashcards
What treatments have been proven to be effective in preventing contrast nephropathy?
- Continuous hemofiltration
- Oral N-acetylcysteine
- Bicarbonate Infusion
How many colony-forming units (CFU) are required from a quantitative bronchoalveolar lavage to make the diagnosis of pneumonia?
10,000 CFU/mL
- For endotracheal aspirates the cutoff is 1,000,000 CFU/mL
- For protected brush specimen the cutoff is 1,000 CFU/mL
What nerves need to be blocked for an awake intubation?
Superior laryngeal nerve (vagus nerve) which supplies sensation to the hypo pharynx (internal branches): epiglottis, base of tongue, supraglottic mucosa, thyroepiglottic joint and the cricothyroid joint.
Glossopharyngeal nerve (IX) which innervates the roof of the pharynx, tonsils, and undersurface of the soft palate.
What is the most common initial manifestation of malignant hyperthermia (MH)?
Increased PetCO2
The initial reduction in core temperature during general anesthesia is cause by?
Redistribution of heat from the core to the periphery
All burn patients should receive 100% oxygen until CoHgb is at what percentage?
Until COHgb is less than 7%.
What are the innervations (afferent and efferent) for the oculocardiac reflex?
Afferent: trigeminal nerve
Efferent: vagus nerve
What coagulation factors are produced outside of the liver?
Factor VIII and von Willebrand are “endothelium-derived procoagulant factors” and are increased in cirrhosis
An extrahepatic source of factor VII has also been identified
What area of the brain is effected by Parkinson’s disease? What are the symptoms?
The fundamental lesion in Parkinson’s is in the basal ganglia.
Classic symptoms:
drawn face
fixed expressions
lead pipe rigidity
nonintentional tremor which diminishes with activity
initiation of movement is difficult as is termination
What are the signs and symptoms of carcinoid syndrome and how is it diagnosed?
Carcinoid tumors release vasoactive peptides into the systemic circulation causing symptoms when the tumor metastasizes from its site of origin (usually the appendix or ileum) to the liver or when its venous drainage returns to the heart bypassing the liver.
Hormones released include: SEROTONIN, histamine, and kinins
Symptoms include: cutaneous flushing (sweating), bronchoconstriction, hypotension, diarrhea
Signs: urinary 5-HIAA levels (a metabolite of serotonin)
right sided heart failure, tricuspid regurgitation (common) or stenosis, pulmonary regurgitation/stenosis (right-sided fibrotic endocardial lesions)I
What is the treatment for carcinoid syndrome?
Octreotide (a somatostatin analogue) is the mainstay of peri-op tx. It binds to SSTR subtypes 2 & 5 inhibiting secretion of various peptide hormones (i.e. serotonin) (t 1/2 1-3 minutes)
Subcutaneous administration with max plasma concentration after 30 mins. Elimination half-life of 1.5-2 hours.
Elimination in 2 phases with half-lives of 10 and 90 minutes respectively
Cyproheptadine is a serotonin antagonist used in serotonin syndrome.
What are the criteria for diagnosing pre-renal acute renal injury (ARI)?
Urine osmolality > 500 mOsm/kg Bland (hyaline casts) sediment Urine Na+ < 10 mEq/L (due to activation of the renin angiotensin aldosterone system (RAAS) FENa < 1% No to minimal amount of protein in urine
How is total lung capacity(TLC) affected in patients with obstructive lung disease? FVC? FEV1/FVC ratio? FEF 25% to 75%?
TLC is normal or increased due to air trapping and increased residual volume (RV)
Forced vital capacity (FVC) is also increased or normal
FEV1/FVC ratio is decreased (since FEV1 is decreased)
FEF 25% - 75% is decreased due to airway resistance
How does restrictive lung disease effect TLC? FVC? FEV1/FVC ratio?
Restrictive disease is a proportional decrease in ALL lung volumes, which results in a normal FEV1/FVC ratio
Decreases in TLC, FVC, FEV1, and FRC
What are the increased anesthetic risks associated with patients with Down syndrome? What disease(s) are usually associated with these patients?
They have an increased risk of airway problems: macroglossia, atlantoaxial instability, subglottic stenosis, and OSA.
They also have an increased risk of HYPOthyrodiism, polycythemia at birth, and diabetes mellitus.
In liver transplants, what are the possible physiologic derangement that may need to be addressed at the time of reperfusion?
1) With the removal of the portal vein clamp and reperfusion of the transplanted liver, the residual cold, potassium-rich preservative solution from the donor liver enters the vena cava and boluses directly to the recipient’s heart.
Prophylactic administration of sodium bicarbonate and calcium may ameliorate the hemodynamic consequences of hyperkalemia
2) Subsequent removal of all naval clamps results in reperfusion syndrome in 30% of recipients; hemodynamic instability with hypotension due to vasodilatation is treated with epinephrine or phenylephrine (norepinephrine, epinephrine, vasopressin infusions) and 3) pulmonary hypertension with nitric oxide or nitroglycerine
At this point, a immunosuppressant steroid is administered, usually methylprednisolone.
What is the first drug choice in treating RV failure with elevated PA pressures following reperfusion in a liver transplant?
Epinephrine is the first drug choice to improve RV contractility and increase systemic blood pressure (primary focus)
Nitric oxide would not increase the systemic blood pressure; nitroglycerin could not be the sole agent (although both are useful in decreasing PA pressure)
What surgical procedures are associated with an increased risk of PONV?
Septal nasal submucosa resection Tonisllectomy and adenoidectomy Rotator cuff repair Knee arthroscopy Laproscopic cholecystectomy Lumpectomy
What is the storage life of red blood cells preserved with CPDA-1 and ADSOL?
42 days
ADSOL (AS-1) is a preservative added to CPD-packed red blood cells which is used to increase the shelf-life of the unit
*Nutricel (AS-3) and Optisol (AS-5) are other common solutions that will preserve RBCs to 42 days.
What is the storage life of red blood cells preserved with CPD, ACD, and CP2D alone?
21 days stored at 1-6 degree Celsius
What is the storage life of red blood cells preserved with CPDA-1 alone?
CPDA-1 solution increases the shelf-life to 35 days
What is the storage life of red blood cells that are frozen?
up to 10 years
How does activated protein C aid in the treatment of septic shock?
Patients with septic shock show clinical or subclinical manifestations of intravascular disseminated coagulation with consumption coagulopathy. Recombinant activated protein C can be given to patients with septic shock to modulate sepsis-induced coagulopathy.
What is the most common transfusion-related infection in the US?
Cytomegalovirus (CMV)
The incidence of transfusion-transmitted CMV disease is dependent on the type of blood product (RBC vs. platelets) and the use of leukoreduction (CMV is latent in cells of the monocyte/macrophage lineage and it is these cells that can support CMV replication)
2.4% vs. seronegative blood components
What are the risk of acquiring West Nile virus vs. HIV vs. HTLV vs. Hepatitis C virus following blood transfusions?
West Nile Virus: 1:1 million
Hepatitis C: 1:1.2 million
HIV: 1:1.5 million to 1:3 million
HTLV: 1:3 million
Following a parathyroidectomy, when would postoperative hypocalcemia reach a nadir? What would the symptoms be?
3 to 7 days after surgery
Symptoms of hypocalcemia include: spasms cramps seizures stridor/apnea (if severe)
What are the symptoms of hypercalcemia?
Stones (renal function)
Bones (pain)
Groans (abdominal pain, nausea/vomiting)
Throans (polyuria, decreased volume status)
Psychiatric overtones (depression, anxiety, cognitive dysfunction)
What are the hallmark signs associated with fat embolism?
Petechial rash over the chest is pathognomonic for fat embolism
Decreased room air saturation
Decreased end-tidal carbon dioxide levels
Intraalveolar hemorrhage can occur in the first 24-48 hours
Diabeties Insipidus (DI) vs. Syndrome of Inappropriate ADH (SIADH); presentation, clinical signs
Both are common postoperative complications of pituitary surgery
DI usually presents as a low blood pressure with excessive urine output
- elevate serum sodium ( >146 mEq/L)
- elevated serum osmolality
- possible pre-renal picture with BUN:creatinine ratio (although serum creatinine is unaffected)
SIADH
- low serum osmolality ( < 270 mOsm/L)
- high urine osmolality (> 450 mOsm/L)
- normal to low serum sodium
How do you determine the normal PaO2 of a patient based on their age?
PaO2 = 102 - age/3
How does lithium effect ADH release?
It inhibits ADH release
What percentage decrease in blood volume must occur to trigger ADH release?
5-10% drop
Increases in what plasma levels occur in the body’s response to surgical stress?
Increase in plasma levels of:
Cortisol Renin ADH Catecholamines Endorphines
(Regional anesthesia, however, may block part of the stress response probably by blockade of neural communications from the surgical site)
How much is vital capacity and FRC changed in laparoscopic surgery? How long does it take for levels to return to normal values?
Vital capacity and FRC may be reduced by 20-40% postoperatively and may not return to normal values until 2-3 days after surgery.
What are the changes in body composition (muscle and fat) associated with aging?
Loss of skeletal muscle Increase in body fat (especially visceral & intramuscular fat) Basal metabolism declines Total body water is reduced Small decrease in albumin levels
What happens to FRC in the elderly?
FRC increases due to the increase in RV (FRC = RV + expiratory reserve volume)
In which direction does the hemoglobin dissociation curve shift with carbon monoxide poisoning?
It impairs oxygen unloading to the tissues and shifts the curve to the left.
Describe the acid-base or electrolyte abnormalities found in a patient with uremic syndrome.
Clinical features
Uremic syndrome is an extreme from of chronic renal failure, which occurs when GFR decreases to less than 10% of normal.
Clinical features: nausea/vomiting, fatigue, anorexia, weight loss, muscle cramps, pruritis, and change in mental status.
Patients often present with elevated phosphate and magnesium levels as excretion of each decreases with progressive renal failure.
Hyperchloremic metabolic acidosis
Criteria necessary to declare brain death
1) Patient must be comatose with neither spontaneous movement nor response to painful stimuli
2) A lack of brain stem activity should be confirmed by assessment of the brain stem reflexes and apnea test
Describe an apnea test
An apnea test is used to confirm the lack of brain stem activity
The patient is pre oxygenated with 100% oxygen for 10 minutes, the PaCO2 is confirmed in the normal range, and the patient is administered oxygen for 10 minutes.
The patient is then disconnected from the ventilator and blow-by O2 is administered with a T-piece
After 7-10 mins, a PaCO2 is measured:
if greater than 60 mmHg, and the patient’s abdomen and chest have NOT moved, the apnea test is positive
What are examples of brainstem reflexes?
Pupillary response to light Corneal reflex Oculocephalic reflex Oculovestibular reflex Gag & Cough reflex Facial motor response
Equation for Mean Arterial Pressure (MAP)
MAP = DBP + [1/3(SBP - DBP)
In what population is FRC increased?
The elderly
FRC increases with age, but only slightly after 50 years.
What is the leading cause of death in patients with multiple sclerosis (MS)?
Bronchial pneumonia due to cranial nerve involvement causing dysphagia
What are some predictive factors of difficult mask ventilation?
Obesity Age > 60 years Mallampati III or IV view Snoring Beard
What is the hallmark finding of COPD based on PFT/Spirometry?
Decreases FEV1/FVC ratio
What is Functional Residual Capacity (FRC)?
ERV + RV
What Vital Capacity (VC)?
IRV + TV + ERV
or
IC + ERV
What PFT increases with COPD? Why?
Total lung capacity mainly due to increased Residual Volume
What is DLCO? How is it used?
DLCO is the CO Diffusion Capacity
It is an independent predictor for risk of post-op complications and reflects alveolar membrane integrity and pulmonary capillary blood flow
What is a low DLCO indicative of?
Low DLCO implies significant emphysema and reduced pulmonary capillary vascular bed
(It can be paradoxically elevated in patients with severe COPD and is indicative of RVH)
