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What causes the pseudohypertrophy in Duchenne’s MD?
Muscle necrosis that is then replaced by fatty fibrotic infiltrates.
Does Duchenne’s only affect skeletal muscle?
No, it also affects cardiac muscle and will result in a dilated cardiomyopathy involving the posterobasal and LV lateral wall.
What is the correlation between the degree of skeletal muscle disease in Duchenne’s and the dysfunction of cardiac muscle.
There is no correlation between severity of the skeletal muscle disease and the cardiac muscle disease.
What is the prevalence of cardiac disease in patient’s with Duchenne’s muscular dystrophy?
As much as 90%, although most of these patients have subclinical manifestations. Only 10% of those patients presenting for surgery have clinically significant cardiac disease however ECG and Echocardiography are part of the regular preop work up.
What induction agent is the gold standard for ECT and why?
Methohexital.
It does not affect seizure duration.
Is better tolerated than etomidate secondary to ability to blunt hemodynamic response and better than propofol and thiopental because it does not decrease seizure duration.
What induction agent used in ECT increases seizure duration?
Etomidate
What is the utility of opioids in anesthesia for ECT?
They help blunt the hemodynamic response to the seizure and can be thought of as “propofol-sparing”. Which means that you can use less propofol and thus lessen propofol’s blunting of seizure activity.
What is the relevance of PaCO2 levels and anesthesia for ECT?
Hypocarbia (hyperventilating the patient) will INCREASE the duration of the seizure.
Compare and contrast thiopental and methohexital for use during anesthesia for ECT?
The most important difference is that methohexital does not affect seizure duration while thiopental (like propofol) decreases seizure duration. They both blunt hemodynamic responses (as does propofol) where as etomidate does not.
What is an adequate seizure duration for ECT?
At least 30 seconds.
What level of ICP is associated with worsened outcome?
ICP > 20 mmHg
What value of cerebral perfusion pressure is the threshold for impaired brain tissue oxygenation and metabolism?
CPP < 50 mm Hg
Preganglionic neurons of the sympathetic system use what neurotransmitter?
Acetylcholine at nicotinic receptors
Postganglionic sympathetic neurons use what neurotransmitter?
Norepinephrine, except for sweat gland innervation which uses ACh to act on the sweat gland muscarinic receptor. The other exception involves the adrenal medulla where preganglionic sympathetic nerves synapse directly on the excretory cells and cause them to release catecholamines systemically.
What is the minimum PaCO2 for patients with TBI?
In TBI, PaCO2 levels lower than 35 mm Hg are considered to result in worse outcomes.
List ways in which an AICD may malfunction.
Battery failure
Sensing problems
Lead migration
May inappropriately fire during atrial tachyarrhythmias
May fail to fire during ventricular arrhythmias if the rate of the arrhythmia is too slow due to rate-controlling medications
What pharmacological therapies are useful for HD stable atrial flutter?
Initial treatment targets rate-control. Thus, 1st line agents are: beta-blockers and calcium channel blockers,
For chemical cardioversion: ibutilide (Class III antiarrhythmic but can cause torsades), amiodarone
What drugs are effective prophylactics to prevent afib/aflutter development after cardiac or thoracic surgery?
beta-blockers, calcium-channel blockers
What are the risk factors of the revised cardiac index?
history of ischemia or heart disease CHF CVA Cr > 2.0 IDDM high risk surgery
What is the risk stratification for cardiac complications using the revised cardiac risk index?
#of risk factors = % risk 0 = 0.4% 1 = 0.9% 2 = 7% 3 = 11%
What is the difference between alpha-stat versus pH stat management during CPB with regards to neurological outcomes?
Multiple independent, prospective randomized trials have shown that α-stat during moderate hypothermia produces better neurologic outcomes than using pH-stat in adults. In children, pH stat may be better.
What is the appropriate glucose goal level during CPB?
< 200. More aggressive treatment of hyperglycemia in cardiac surgery patients does not improve mortality and in fact increases the incidence of stroke, and possibly death.
What agent is used for acute treatment of long-QT?
IV magnesium
(as well as replacement of potassium and calcium if those levels are low)
Amiodarone is contraindicated in these patients.
What medication class is used for long-term treatment of long QT?
Beta-blockers (although LQT3 which is Na+ related, often needs a PPM)
If an ASA VI (six) class patient develops bradycardia, what is the medication of choice to treat it?
Isoproterenol. Consider other direct acting agents like dobutamine, milrinone, dopamine, epinephrine, etc….
Atropine may not work because there may not be any vagal activity present.
What is the major concern with pH-stat management?
Because of the decoupling of CBF and CMRO2, the increased CBF in pH-stat increases the cerebral embolic load risk to the patient.
What is the relationship between CBF and CMRO2 in pH-stat versus alpha-stat management?
pH-stat uncouples CBF from CMRO2 and CBF is pressure dependent.
Alpha-stat preserves the coupling and CBF is CMRO2 dependent.
The goal of alpha-stat management is?
Maintain the ionization state of histidine
How does hyperbaric oxygen help carbon monoxide poisoning?
It reduces the half-life of CO-Hgb to 15 - 30 minutes at 3 atm. However, the real benefit of HBO may be in regeneration of cytochrome oxidase and inhibition of leukocyte adherence to the microvascular endothelium which reduces ischemic reperfusion injury.
When should hyperbaric oxygen therapy begin in order to benefit patients with carbon monoxide therapy?
Within 6 hours.
What should initial treatment of carbon monoxide therapy involve?
100% O2 to reduce CO-Hgb half-life to 1 - 2 hours from 4 - 5 hours. Check and treat glucose levels since high levels are associated with worse neuronal outcomes. Get to hyperbaric oxygen therapy within 6 hours.
What preoperative VO2 predicts poor outcomes after lung resection?
VO2 < 10cc/kg/min is very high risk. 15cc/kg/min is a reasonable cutoff.
How does one calculate predicted postoperative FEV1 after lung resection?
FEV1 x (1 - %LungResected) = ppoFEV1
A value < 30% is high risk for pulmonary complications. >40% is considered safe.
What ppoFEV1 predicts poor outcomes after lung resection?
< 30%.
> 40% indicates that it’s probably safe in the absence of other poor predictors.
What DLCO predicts poor outcomes after lung resection?
DLCO < 40% predicted is high risk for complications. This is independent of ppoFEV1.
What FEV1 value is associated with poor outcomes after lung resection?
FEV1 < 2L
What MVV predicts poor outcomes after lung resection?
> 50%
How does one calculate FENa?
FENa = 100 ((Urinary sodium X Plasma creatinine)/(plasma sodium X urinary creatinine))
How can positive pressure ventilation +/- hyperventilation cause intraoperative oliguria?
Decreased cardiac output and subsequent SNS response (vasoconstriction)
Increased IVC pressure (reduced pressure gradient and renal blood flow)
What is the mechanism of renal failure causing platelet dysfunction?
Impaired platelet factor 3, platelet adhesiveness, platelet aggregation.
Treat with desmopressin.
Name three things that can artificially increase creatinine levels periooperatively.
Cephalosporins (for up to 16 hours)
Ketoacidosis
Barbiturates
What causes the diffuse hyperpigmentation seen in Addison’s disease
Addison’s is primary adrenal insufficiency. Diffuse hyperpigmentation occurs secondary to a compensatory increase in ACTH and beta-lipotropin.
Symptoms of hyperparathyroidism are?
Neuro: CONFUSION, lethargy, psychiatric abnormalities
GI: anorexia, vomiting, constipation, pancreatitis
GU: POLYURIA, POLYDIPSIA, formation of RENAL CALCULI (in approximately 60-70% of patients with hyperparathyroidism)
Other: BONE PAIN, HTN (in 33%)
What foods are associated with latex allergy?
banana, pineapple, avocado, chestnut, kiwi fruit, mango, passionfruit, strawberry, and soy, as well as potato and bell pepper
What does vanillylmandelic acid excretion indicate?
Pheochromocytoma.
It is 80% sensitive, 97% specific.
What clinical signs and symptoms are more sensitive than any blood test for pheochromocytoma?
Paroxysmal HA + sweating + HTN more sensitive than any single blood test.
What is the utility of alpha-blockade prior to surgery in pheochromocytoma?
It reduces risk of mortality from 50% to 5%!
What alpha-blockers are recommended for pheochromocytoma and when should they be started in the perioperative period?
Prazosin or phenoxybenzamine.
Recommended to start 10 - 14 days prior to surgery.
What medication should be used for hypotension intraoperatively for a patient with pheochromocytoma?
Phenylephrine, preferably because it is direct acting.
What medication should be used for hypertension intraoperatively for a patient with pheochromocytoma?
Nitroprusside
When and how does hypocalcemia present as a complication after thyroidectomy?
24 - 48 hours after surgery as stridor or airway obstruction but whose first symptoms are usually lip and finger tingling.
What is Chvostek’s sign?
A sign of hypocalcemia elicited by tapping the facial nerve in the preauricular area.
What is Trousseau’s sign?
A sign of hypocalcemia elicited by inflating a BP cuff on the arm that then results in carpal spasm.
What is the most common cause of airway obstruction within 24 hours of thyroidectomy?
Hematoma
What is the most common cause of airway obstruction after the first 24 hours of post-thyroidectomy?
Hypocalcemia
What is the incidence of febrile transfusion reaction with pRBCs? with platelets?
RBCs = 0.5% Platelets = 30%
What is cause of febrile reactions after transfusion?
Since most products are leukoreduced, the most common cause is recipient antibodies against HLA antigens on the donated cells.
However with platelets, it is likely to be donated leukocytes releasing their cytokines. Pre-treat or treat with tylenol and benadryl.
What blood type is the universal donor for plasma?
AB
What blood type is the universal acceptor for plasma?
Type O
What are the indications for FFP according to the ASA?
Recommended dose = 10-15 cc/kg
1) Urgent reversal of warfarin (only requires 5-8 cc/kg). Note, however, the prothrombin complex concentrate has been shown to be more effective
2) Correction of known coagulation factor deficiencies for which specific concentrates are unavailable
3) Correction of microvascular bleeding in the presence of INR > 1.5
4) Correction of microvascular bleeding in the presence of massive transfusion (> 1 blood volume)
What viruses are transmitted in donor leukocytes?
EBV, HTLV-1, CMV
How do changes in temperatures affect PaCO2? PaO2?
PaCO2 decreases by approximately 2 mm Hg per °C below 37°C.
PaO2 decreases by approximately 5 mm Hg per °C below 37°C.
Therefore if an ABG at 37°C showed a PaCO2 of 40 mmHg and a PaO2 of 100 mm Hg, at 27°C it would be approximately a PaCO2 of 20 mm Hg and a PaO2 of 50 mm Hg.
What is the formula for oxygen content?
Oxygen content = (1.39 x Hb x O2Sat/100) + (0.003 x PO2)