Troublesome Topics

Mishmash of things I struggle with.

What shifts the oxyhemoglobin curve to the right?

Think of veins: acidosis hyperthermia S high 2, 3-dpg, and ↑paoz

Which lung volumes comprise the vital capacity?

IRV + TV + ERV

What lung volumes comprise the FRC?

ERV + RV

Or if atelectatic, ERV* which is the volume that is forcefully exhaled when conditions promote early airway closure & atelectasis. Therefore it would be ERV* + CC + RV

Which lung volumes comprise IC?

IRV + TV

What is a type I error?

Rejecting the null hypothesis when there is no difference.

What is a type II error?

Accepting the null hypothesis when there is a difference.

Transfusion goals in DIC

Hb > 7 g/dL

INR < 1.5

Fibrinogen > 300 mg/dL

Plts > 50,000/uL

Which EKG leads correspond to the circumflex artery?

I, aVL, V5-6

Which EKG leads correspond to the left anterior descending artery?

V1-4, ± V5-6

Which EKG leads correspond to the right coronary artery?

II, III, aVF

What is the myocardial distribution of the RCA?

Anterior wall of RV, inferior and inferoseptal aspects of the LV, SAN +/- AVN

What is the myocardial territory of the circumflex artery?

Lateral wall of the LV

What is the myocardial territory of the LAD?

anterior and anteroseptal walls of the LV

What vasoactive substances are not metabolized by the lungs?

Histamine and epinephrine

What does angiotensin converting enzyme do? Where does it live?

Converts angiotensin I to angiotensin II and lives in the lungs.

What is normal mixed venous oxygen saturation?

70-75%

The carotid body chemoreceptors are most stimulated by what?

Arterial PO2

What is the half life of albumin?

20 days

What is the half life of factor VII?

4 hours

What is the half life of fibrinogen?

4 days

What is the final layer crossed by the needle in both the median and paramedian approaches to the epidural?

Ligamentum flavum

What is the order of layers from superficial to deep that the needle crosses in a paramedian epidural?

Skin, subcutaneous fat, ligamentum flavum, dura, subdural space, arachnoid mater, subarachnoid space.

Where do you deposit the local when performing an obturator nerve block?

between adductors longus & brevis, then between adductors brevis and magnus

What congenital cardiac lesions require a patent ductus arteriosus?

Hypoplastic left heart syndrome, pulmonary atresia, and transposition of the great vessels.

What conditions will maintain a PDA?

Hypothermia, hypoxia, & hypercarbia

What is the only vocal cord tensor?

Cricothyroid

What nerve innervates the cricothyroid muscle?

Superior laryngeal n. the external branch

What muscles do the recurrent laryngeal nerves innervate?

All of the intrinsic muscles, except for the cricothyroid.

What determines the speed of onset of a local anesthetic?

pKa

What influences the potency of a local anesthetic?

Lipid solubility

What are some ductal dependent lesions which are due to impaired pulmonary blood flow?

Tetralogy of Fallot

Pulmonary atresia

Severe pulmonary stenosis

Transposition of the great arteries

Severe subpulmonic stenosis with VSD

What are some ductal dependent lesions which are due to impaired systemic flow?

Critical aortic stenosis

Aortic atresia

Aortic coarctation

Interrupted aortic arch

Hypoplastic Left Heart Syndrome

Which type of decels are unrelated to maternal contractions?

Variables

What is the cause of a variable decel?

Cord compression (nuchal cord, between head and cervix…)

What does pharmacokinetics study?

The study of how a drug is distributed, circulated, & eliminated

Things such as administration route, bioavailability, protein binding, metabolism, & lipophilicity

What is pharmacodynamics?

The study of how a drug interacts with a receptor and the downstream effects.

Eg. dose-response relationships, effect duration, type of effect (agonist vs antagonist, etc)

Which amino acids are only ketogenic?

Leucine & Lysine

Which amino acids are both ketogenic & glucogenic?

phenylalanine, isoleucine, threonine, tryptophan, & tyrosine

What enzyme is the rate limiting step in cholesterol synthesis?

HMG-CoA reductase

What is the mechanism of contact dermatitis from latex?

Delayed T cell mediated, type IV hypersensitivity reaction

What coagulation factors are not made in the liver at all?

III, Tissue factor - made in vascular endothelium

IV, Calcium - comes from bones, diet, & platelets

Which coagulation factors have multiple sites of synthesis, which include the liver?

V, Proaccelerin - also made in platelets

VIII, Antihemophillic factor A - made in vascular endothelium

XIII - made in platelets

What does ST depression indicate?

Subendocardial ischemia

What does a a Q wave on EKG indicate?

Transmural ischemia, may be remnant of old infarct.

What does ST elevation on EKG indicate?

Transmural injury & ischemia

What are the main determinants of myocardial O2 demand?

HR, contractility, & wall stress

What law governs wall stress?

Law of LaPlace

What are the main determinants of myocardial oxygen supply?

Coronary blood flow, arterial oxygen content, & myocardial ability to extract the oxygen.

What percentage of the spinal cords blood supply is provided by the anterior spinal artery?

75%

What are you most likely to see on EEG in patient having generalized tonic clonic seizures?

Spike and slow wave patterns.

When are K complexes seen on EEG?

Usually during stage 2 non-REM sleep. Usually found with sleep spindles.

What two common drugs in anesthesia are metabolized by nonspecific tissue esterases, so therefore would be unaffected by a pseudocholinesterase deficiency?

Remifentanil and Esmolol

Most likely cause of hydrocephalus in a newborn is?

Renal agenesis

What nondepolarizing neuromuscular blocking agent can activate the sympathetic nervous system in a pt with hyperthyroidism?

Pancuronium

What do the gray rami communicantes do?

they carry postganglionic sympathetic fibers from the sympathetic ganglia to the spinal nerves

What do the autoantibodies target in myasthenia gravis?

The acetylcholine receptor

What do the autoantibodies target in Lambert-Eaton syndrome?

Presynaptic voltage-gated calcium channels

What do the autoantibodies target in Graves disease?

Thyrotropin receptor

What do the autoantibodies target in Hashimoto’s disease?

Thyroid peroxidase

What is the treatment for a stable SVT?

Adenosine

Can lead to a pause for a few seconds with some ventricular escape beats. Works via blockage of AV node. Should restore sinus rhythm. If it does not, try CCB

Absolute contraindications to TEE?

Zenker’s (esophageal) diverticulum

Perforated esophageal injury

Active UGIB

Esophageal stricture

Esophageal tumor

Relative contraindications for TEE

Esophageal varices

H/o radiation to neck/mediastinum

Recent UGIB

H/o dysphagia

Symptomatic hiatal hernia

Coagulopathy

According to ASRA guidelines, in pts on longterm heparin therapy, what should you do prior to neuraxial procedure?

Check a platelet count.

Should also wait 4-6hrs after last dose before doing procedure.

If used alone, is aspirin therapy a contraindication to neuraxial?

No

How long should you wait after heparin to remove an epidural?

4-6hrs. Can be restarted immediately after.

How long after doing neuraxial should you wait before restarting prophylactic dose SQH?

Can restart immediately.

What commonly prescribed opioid can lower the seizure threshold?

Tramadol

What less commonly used class of antidepressants, that is also used for neuropathic pain, can lower the seizure threshold?

TCAs.

What is the cause of a febrile, non-hemolytic transfusion reaction?

Recipient’s antibodies bind to HLA antigens on donor leukocytes.

What nerve innervates the first web space of the foot?

Deep peroneal

How would you block the deep peroneal nerve using anatomic landmarks?

Palpate the dorsalis pedis artery, then inject laterally.

If you cannot find the artery, then ask them to extend their big toe. This accentuates the extensor hallicus longus tendon, and the local is injected laterally to that.

What is the most significant risk factor for relapse in an anesthesiologist returning to practice after being treated for substance use disorder?

Remaining in anesthesiology.

this is so sad.

From first to last, what is the order of recovery from nondepolarizing neuromuscular blockade?

diaphragm > larygneal muscles > corrugater supercilli > abdominal muscles > orbicularis oculi > geniohyoid > adductor pollicis

When is a pt who just had a SAH most likely to have vasospasm?

2-14 days after

What is the only medication that has been shown to decrease mortality from vasospasm after SAH?

Nimodipine (though not because of vasodilatory properties)

When considering inhaled anesthetics and changes in altitude, which physical properties do not change?

Vapor pressure

What does anesthetic depth depend on in terms of inhalational agents?

Partial pressure of the anesthetic.

When moving an Isoflurane vaporizer from sea level to Mt. Everest, do you need to change the dial? Why or why not?

No you do not, because the vapor pressure does not change, so therefore the partial pressure that the pt receives will not change. So their anesthetic depth will remain the same.

When moving an isoflurane vaporizer from sea level to Mt. Everest, what will change if the vaporizer is kept at 1%?

the volume percentage concentration will increase, and more gas will leave the vaporizer. But the partial pressure will not change, so the depth does not change.

Closing capacity

The volume remaining in the lungs when the alveoli BEGIN to close.

So if you decrease the FRC, while CC remains unchanged, then there will be increased atelectasis and earlier alveolar closure.

During forced exhalation, what part of the lung empties first?

The apices, which is why the lung bases is where the atelectasis will develop.

What lung volume/capacity is UNCHANGED in pregnancy?

Vital capacity (because IRV increases to compensate for decreased FRC).

RR will also remain unchanged.

What electrolyte changes can you expect in someone taking a loop diuretic?

Low Na, K, Mg, and hyperuricemia.

What is the gold standard for confirming DLT placement?

Flexible bronchoscopy to visually confirm position

What is the most likely complication for a pt undergoing a TURP?

Hypothermia 2/2 large volume of room temp irrigating fluids.

FENa <1% is suggestive of what type of AKI?

Prerenal, such as dehydration, distributive shock

Why does CVP not change in pregnancy?

Because the increase in volume is matched by an increase in blood vessel capacitance. This is the only hemodynamic parameter that DOES NOT change in pregnancy.

What is the primary neurologic effect of drowning?

Cerebral hypoxia

In a pt who drowns in saltwater, will they have hypo or hypernatremia?

Hypernatremia

However, typically those who survive drowning don’t have many electrolyte disturbances because of the small volume of aspirated liquid

Chronic pelvic pain 2/2 uterine cancer best treated by what block?

Superior hypogastric

A ganglion impar block would treat pain from what areas?

Coccyx, perineum, anus, rectum, vagina

When compared to an arterial waveform from the aorta, what are the differences between that and an arterial waveform from a more distal site (radial, dorsalis pedis, etc)?

Steeper systolic upstroke

Higher systolic peak

Blunted dicrotic notch

Lower diastolic peak

Greater pulse pressure

What will be the effects of dexmedetomidine’s alpha-2 agonism in the dorsal horn of the spinal cord?

Analgesia

Where are the alpha-2 receptors responsible for the sympathetic blunting effects of dexmedetomidine?

Hypotension and bradycardia are mediated in the vasomotor center of the brainstem.

Where are the alpha-2 receptors responsible for the sedation & anxiolytic effects of dexmedetomidine?

The locus ceruleus

What is TBW in an older person?

50% of their body weight

What is the TBW of a neonate?

80% of their body weight

How does hypophosphatemia lead to decreased oxygen delivery in the tissues?

With low Phos, there is decreased production of 2,3-BPG, which shifts the oxyhemoglobin curve to the left, which does not favor oxygen unloading in the tissues. Low phos also causes diaphragmatic weakness, and it is harder to produce ATP for metabolic processes without PO4.

Which anesthetic will increase hepatic blood flow?

Propofol

When positioning a patient who has compression of the tracheobronchial tree from an anterior mediastinal mass, what position do you prefer?

Lateral - relives compression on the tracheobronchial tree by working with gravity