Basic Exam Flashcards
the National Institute for Occupational Safety and Health (NIOSH) recommended exposure limits for anesthetic gases of 2 ppm when only halogenated anesthetic gases are used, 25 ppm when only nitrous oxide is used and 0.5 ppm for halogenated anesthetics in combination with nitrous oxide
Calcium, sodium, and potassium are all responsible for generating an action potential in the sinoatrial node. An influx of calcium is responsible for the actual depolarization of the cell, while an efflux of potassium repolarizes the cell after depolarization. After repolarization, funny sodium channels cause spontaneous depolarization, augmented by the opening of calcium channels that speed the spontaneous depolarization during phase 4 of the action potential.
Diffusion hypoxia is a well-known phenomenon that can occur following administration of nitrous oxide as part of general anesthesia. The low blood solubility of nitrous oxide, coupled by relatively low potency leads to large amounts of nitrous oxide being eliminated into the alveoli over a short period of time following cessation of anesthesia. This leads to displacement of oxygen and carbon dioxide in the alveoli. Supplemental oxygen should be provided to mitigate this effect.
When the α1 receptor is activated, it increases IP3,leading to vasoconstriction.
When the β1 receptor is activated, it increases cAMP, leading to an increase in heart rate.
Activation of the β2-adrenergic receptor results in the activation of adenylyl cyclase, increasing cAMP leading to bronchodilation
In normal-weight adult males and females, total body water makes up approximately 60% and 50% of total body weight, respectively. Approximately 2/3 of total body water is intracellular while 1/3 is extracellular. About 75% of extracellular fluid is interstitial fluid and 25% is plasma. Obese individuals have a proportionally smaller TBW compared to their weight.
Neonates and infants have a proportionately higher total body water than adults which causes them to require higher doses of water-soluble drugs (succinylcholine, midazolam) to achieve the same effect.
The axillary block is an upper extremity nerve block with an axillary approach but does not involve the axillary nerve. The block provides anesthesia to the median, radial, and ulnar nerves at the level of the branches. To provide more anesthetic coverage of the lateral forearm, the clinician gives supplementation to the musculocutaneous nerve. To provide more coverage of the medial upper arm, the clinician gives supplementation to the intercostobrachial nerve.
A supraclavicular block is performed at the level of the distal trunks and proximal divisions of the brachial plexus. Major structures involved at this level include the brachial plexus, subclavian artery, first rib, and pleura. The brachial plexus lies superficial and lateral to the subclavian artery, and the subclavian artery lies superficial to the first rib.
Restrictive transfusion strategies are preferred and wait for lower hemoglobin levels to reduce the number of transfusions performed. Red blood cells should be administered unit-by-unit, when possible, with interval reevaluation.
It has been found that patients rarely require a transfusion when hemoglobin is > 10 g/dL, they will likely require a transfusion with acute blood loss lowering hemoglobin to less than 7 g/dL, and chronic anemia of 6-7 g/dL can usually be tolerated.
The opening of voltage-dependent Ca2+ channels leads to induction of phosphorylation of synapsins and fusion of presynaptic acetylcholine vesicles to the presynaptic membrane. This causes a release of acetylcholine through exocytosis at the synaptic cleft.
Acetylcholine is then degraded by cholinesterase into acetate and choline, and the choline is taken back up into the neuron by the Na+/choline transporter.
Cryoprecipitate contains approximately 200 mg/unit of fibrinogen. Cryoprecipitate is indicated as factor replacement in hypofibrinogenemia, von Willebrand disease, and hemophilia A. Cryoprecipitate is high in factors 8 and 13 as well as fibrinogen and von Willebrand factor (vWF).
Stages of Anesthesia
Stage 1- Conscious but decreased perception of pain
Slow, regular breathing
Stage 2- Unconscious with irregular breathing, breath-holding, hyperreflexia, and excitation
Hypertensive, tachycardic, and loss of eyelash reflex but laryngeal reflexes remain intact
Higher risk of laryngospasm
Stage 3- Surgical depth of anesthesia, diaphragm paralysis, loss of laryngeal reflexes
Stage 4- Anesthesia overdose, Cardiovascular and respiratory depression
The TOF ratio is the ratio of the height of the fourth twitch to the height of the first twitch, and is used in evaluating reversal of neuromuscular blockade. The gold standard TOF ratio indicating appropriate reversal is 0.9
Double burst stimulation is a series of two short tetanic stimulations (two impulses at 50 Hz, separated by 750 ms) which correlates well to the TOF ratio up to a ratio of 0.6. Tetanus is a sustained stimulus of 50 to 100 Hz for five to ten seconds and can be useful in confirming adequate reversal of neuromuscular blockade
The likelihood of infection or ischemia is low in brachial artery catheterization. In the cardiac surgery population, brachial artery catheterization is more reliable than radial artery catheterization, especially after cardiopulmonary bypass. Brachial artery lacks collateral blood flow.
Cisatracurium undergoes nonenzymatic Hofmann elimination in plasma. The reaction speed is increased with higher pH and higher temperature. As the drug undergoes minimal renal or hepatic metabolism, it is safe to use in patients with significant kidney or liver disease.
Infusion of a 20% intravenous lipid emulsion (ILE) is the treatment for systemic toxicity from local anesthetics, and particularly for cardiac arrest that is refractory to standard therapy. ASRA guidelines recommend consideration of lipid emulsion therapy at the earliest signs of systemic toxicity from local anesthetics.
The lipid infusion extracts the lipid-soluble molecules of the local anesthetic from the plasma. An initial bolus of 1.5 mL/kg is administered over several minutes followed by an infusion at a rate of 0.25 mL/kg/min for 30-60 minutes or until hemodynamic stability is achieved.
Plavix inhibits the P2Y12 receptor. It is a prodrug. 40% people don’t have a response. Irreversible. Is associated with thrombotic thrombocytopenic purpura.
Cangrelor is an IV version of the active form of Plavix. Return of platelet function in 60-90min
Five important risk factors for difficult bag mask ventilation are the presence of a beard, BMI > 26, edentulous, age > 55 years, and a history of snoring. Other risk factors include Mallampati class III or IV, severely limited mandibular protrusion, and mouth opening < 3 cm. Finally, a thyromental distance < 6 cm has been shown to be an independent risk factor for difficult bag mask ventilation.
A bobbin flowmeter is structured with a weighted bobbin within a tapered cylindrical tube. As the flow and pressure beneath the bobbin increases, it will rise until reaching equilibrium. Due to the shape of the cylinder, as the bobbin rises the cross-sectional area around it will increase as well.
treatment for hyperkalemia includes calcium & insulin to stabilize the myocardium in the setting of ECG changes, shifting potassium intracellularly, and elimination of potassium from the body
Atelectasis develops in about 90% of patients in the postoperative period. Atelectasis is caused by a combination of changing the patient from an upright to a supine position, loss of muscle tone during induction, a subsequent decrease in FRC, loss of surfactant, and compression of lung tissue.
In patients with end-stage renal disease, baseline electrolytes should be obtained.
A CBC is indicated for patients with a history of increased bleeding, hematologic disorders, recent chemotherapy, steroid or anticoagulant therapy, poor nutritional status, and surgical procedures with a high predicted blood loss.
A grade II includes the visualization of only the posterior aspects of the glottic aperture.
Grade III is when the epiglottis is only visible.
Finally, a grade IV view is the visualization of only the soft palate
Systolic blood pressure is the most overestimated and least accurate measurement comparing to direct invasive monitoring.
The alpha-2 agonist drugs clonidine and dexmedetomidine help to reduce the risk of postoperative shivering.
Ondansetron, ketamine, and tramadol may also prevent shivering.
Dexmedetomidine is extensively metabolized in the liver before being excreted in urine and feces.
High-frequency oscillatory ventilation uses high mean airway pressures to stent the airways open while small and frequent tidal volumes actively drive air in and out of the lungs providing ventilation. This mode has been used to good effect in premature neonates with respiratory distress syndrome but not adults
Both high-frequency jet ventilation (HFJV) & high-frequency percussive ventilation (HFPV) allow for passive exhalation throughout the respiratory cycle, however, in HFOV exhalation is actively driven by the device.
Glucagon, catecholamines, and cortisol are counter-regulatory hormones because they oppose the effects of insulin and synergistically act to increase hepatic glucose production. These hormones act to stimulate hepatic glycogenolysis and gluconeogenesis. Insulin opposes the action of gluconeogenesis.
Delayed hemolytic transfusion reaction is a result of recipient antibodies targeting donor minor red blood cell antigens to which the recipient has previously been exposed, leading to hemolysis of the donated red blood cells. Hemolysis occurs within days to weeks after the transfusion, and symptoms are generally mild or absent.
Donor antibodies activating recipient neutrophils are the cause of transfusion-related acute lung injury (TRALI). These neutrophils result in damage to the pulmonary vascular capillary bed, leading to pulmonary edema.
TRALI is typically present during or within 6 hours of the blood transfusion with fever, hypotension, hypoxia, pink frothy airway secretions, and transient leukopenia. Chest radiographs will reveal bilateral infiltrates similar to transfusion-associated circulatory overload.
Train-of-four fade and tetanic fade are due to blockade of α3β2 prejunctional receptors.
Aα fibers transmit motor and proprioception.
Aβ fibers transmit sensation of touch and pressure from stretch receptors.
Aγ(GAMMA) fibers transmit motor efferent signals to the muscle spindle.
Aδ (DELTA) fibers transmit pain impulses, temperature, and sensation of touch.
The intervillous space has the lowest intravascular pressures within the uteroplacental and fetoplacental circulation. This low pressure allows for large volumes of blood to be moved through this space to allow adequate maternofetal nutrient and oxygen transfer. It also prevents the collapse of umbilical veins as they return to this space
Uteroplacental circulation is not fully established until the beginning of the second trimester
adductor canal block, a variant of a saphenous block, is often used as an analgesic adjunct for knee surgery. pain relief provided by adductor canal block is noninferior to that of femoral nerve block. Adductor canal blocks were also found to have less risk for falls. Although the saphenous nerve is purely sensory, an adductor canal block often affects the nerve to the vastus medialis because of its location within the adductor canal. Motor weakness may occur, and patients should be closely monitored as they begin to ambulate.
The saphenous nerve is a terminal branch of the femoral nerve providing sensory innervation to the medial aspect of the leg and foot. It originates from the L2 through L4 nerve roots and descends through the femoral triangle, Then, it traverses the adductor canal with the femoral artery and courses superficially in the anteromedial leg alongside the saphenous vein.
Metoclopramide’s GI promotility properties result in increased lower esophageal sphincter (LES) pressure, increased speed of gastric emptying, and decreased pyloric pressure.
Long-term use of metoclopramide (> 12 weeks) increases the risk for extrapyramidal side effects, including tardive dyskinesia, and it has the potential to prolong the QT interval
Agents which decrease both cerebral metabolic rate and also have vasodilatory effects (e.g. propofol, dexmedetomidine, inhaled halogenated anesthetics <0.5 MAC) will tend to cause a decreased cerebral blood flow and volume
Any agent that causes cerebral vasodilation without also decreasing cerebral metabolic rate will result in an increase in cerebral blood flow and cerebral blood volume. This can be seen when direct-acting vasodilators (e.g. nicardipine, hydralazine, nitroglycerin) are administered.
A rare side effect of sedation with intramuscular ketamine is laryngospasm. If the patient has no IV, you can administer IM succinylcholine to break the laryngospasm, 4 mg/kg intramuscular dose.
Calcium channel blockers have a minor potentiation effect on nondepolarizing and depolarizing neuromuscular blockers, but it is clinically insignificant in patients taking CCBs chronically.
A shift in the Frank-Starling curve up or down is an indication of changes in contractility, with upward shifts providing evidence of positive inotropy and downward shifts providing evidence of negative inotropy.
Droperidol, a D2-antagonist, is contraindicated in patients with a suspected QT prolongation. Patients with electrolyte disturbances such as severe hypomagnesemia, are at risk for developing a prolonged QT interval
A paired t-test compares means in a single group who serve as their own control, whereas an unpaired t-test compares a mean in two different groups.
Analysis of variance (ANOVA) is used to test the means when 3 or more groups exist.
The right main bronchus should give rise to a very close right take off which is the right upper lobe that will have three take-offs which are the anterior, posterior, and superior lung segments of the right upper lobe. The left main bronchus has two take-offs which are the upper and lower lobes of the left lung.
The intercostobrachial nerve typically arises from the dorsal rami of T1-T3 and, thus, is spared in brachial plexus blocks. The intercostobrachial nerve innervates the medial upper arm. It is anesthetized by a subcutaneous field block injection starting at the deltoid prominence
ERAS protocols include allowing clear liquids until 2 hours before the start of surgery. Nutritional strategies also include intraoperative fluid optimization and early postoperative enteral nutrition with high-calorie supplements.
The administration of lactated Ringer solution is safe in patients with kidney disease and does not produce hyperkalemia.
Botulism is characterized by flaccid paralysis, blurred vision, ptosis, nausea, and respiratory difficulty. Botulinum toxin binds to pre-synaptic cholinergic nerve terminals and inhibits the release of acetylcholine by preventing vesicle fusion.
Guillain-Barre syndrome (GBS) is characterized by sudden onset of ascending motor paralysis, areflexia, and variable paresthesias. GBS is associated with antibodies against gangliosides and myelin sheath of peripheral nerves.
In simple terms shunt is defined as a portion of the lungs that is perfused but not ventilated while dead space is the opposite (portion of the lungs that is ventilated but not perfused).
High concentrations of oxygen decrease FRC through development of microatelectasis. This occurs because of alveolar collapse – when higher concentrations of oxygen are used, less nitrogen is part of the alveolar gas. Nitrogen helps keep alveoli ‘stented’ open, helping to decrease the amount of micro collapse.
The Bohr effect refers to the shift in the oxygen dissociation curve caused by changes in the concentration of carbon dioxide or the pH of the environment.
The chloride shift refers to the reaction in which bicarbonate is exchanged for a chloride ion across the red blood cell membrane.
Airway obstruction after total thyroidectomy may be caused by a postoperative hematoma, compression of the trachea, tracheomalacia, bilateral recurrent laryngeal nerve damage, or hypocalcemia resulting from inadvertent removal of the parathyroid glands. Although the airway symptoms of hypocalcemia can develop as early as 1 to 3 hours after surgery, they typically do not develop until 24 to 72 hours postoperatively.
Areas of mechanical dead space in a typical anesthesia machine circle system setup are:
1) The portion of the endotracheal tube (ETT) which extends out of the trachea
2) The breathing circuit elbow connector
3) Any connector used between the ETT and the breathing circuit
4) The Y-piece at the end of the circuit
The cricoid cartilage (C6) has a complete cartilaginous ring. Carina is at T5. The trachea contains 16 to 20 C-shaped rings of hyaline cartilage. The bronchi have complete circular cartilage rings. The lower airway loses cartilage support at the level of the bronchioles. The trachea is lined by ciliated pseudostratified columnar cells.
Compared to the central arterial waveform, the peripheral waveform will exhibit a higher systolic peak and lower diastolic nadir with a lower mean arterial pressure
Prosthetic cardiac valves, previous infective endocarditis, special cases of congenital heart disease, and valvular heart disease after cardiac transplantation are cardiac conditions that have the highest risk of adverse outcomes from Infective Endocarditis.
These patients should receive antibiotic prophylaxis if they undergo dental procedures with gingival manipulation or perforation of oral mucosa and respiratory tract procedures that involve incision or biopsy of mucosal tissue. Prophylaxis for genitourinary or gastrointestinal procedures is not recommended unless there is an active infection.
An odds ratio of > 1 indicates a positive effect, an odds ratio of 1 indicates no effect , and an odds ratio of < 1 indicates a negative effect.
Laboratory Findings Suggestive of Acute Hemolytic transfusion reactions
In the setting of DIC; **Both direct and indirect elevated, indirect > direct; **Indicative of renal damage.
Oxygen regulators are present in anesthesia machines to help ensure proper oxygen delivery and backup. The first-stage regulator will shut off the lower pressure oxygen cylinder tanks when the higher-pressure oxygen pipeline is sensed.
The pipeline system delivers pressures of 50-55 psig
Pressure through the oxygen tank is regulated to enter at 40 to 45 psig.
Pulse oximetry measures functional hemoglobin saturation.
Fractional hemoglobin saturation is measured by co-oximetry (which uses multiple wavelengths) is needed when you suspect the presence of carboxyhemoglobin or methemoglobin.
Oxyhemoglobin absorbs less red light than does deoxyhemoglobin.
Pulse oximetry is a poor monitor of ventilation, especially when patients are breathing 100% oxygen.
The osmolality gap is the measure of the unmeasured solutes in the plasma which is the difference between the measured serum osmolality and the calculated osmolality.
2 x [Na+] + [Glucose]/18 + [BUN]/2.8. The 3 main contributors to plasma osmolality are Na+, glucose, and urea.
alcohols (ethanol, methanol, and ethylene glycol), sugars (mannitol and sorbitol), ketones, and lactate are unmeasured solutes.
Common causes of osmolality gap include ethanol ingestion and the causes of an elevated anion gap.
Bayes theorem is used to help develop preoperative testing algorithms by helping clinicians interpret testing results in light of the patient presentation and surgical procedure.
Bayes theorem describes the probability of an event, based on conditions that might be related to the event (conditional probability).
2,3-DPG is an intermediate step in the glycolytic pathway and this product of cellular metabolism is a factor in the shifting of the oxyhemoglobin dissociation curve. Given that it is indicative of cellular metabolism occurring, increases in its production shifts the curve to the right, favoring oxygen unloading at the level of the tissues.
Storage of red blood cells shifts the oxyhemoglobin dissociation curve to the left, as does hypothermia.
If the inspiratory valve is incompetent, exhaled gas will be allowed to enter a part of the inspiratory limb close to the patient
if the expiratory valve is incompetent, carbon dioxide will enter the patient (as backflow) throughout the inspiratory phase
Metformin can be continued throughout the perioperative period for **minor surgeries **but may be held starting the day before surgery for major surgeries.
The primary risk of continuing metformin is metformin-associated lactic acidosis (MALA).
Metformin is an oral antidiabetic belonging to the biguanide group. Its mechanism of action is to decrease hepatic gluconeogenesis and increase insulin sensitivity.
Metformin is contraindicated in conditions that increase the risk of renal hypoperfusion, lactate accumulation, and tissue hypoxia.
Two types of postoperative liver injuries have been reported to be associated with halogenated anesthetic administration. The first type is a mild injury characterized by nausea, lethargy, and fever. The second type, mediated by the patient’s immune system, is severe acute hepatitis with histological findings of widespread hepatic necrosis. This is rare. Isoflurane & halothane have highest incident rate.
Desflurane, as a consequence of trifluoroacetic acid (TFA) reactive intermediates, has been implicated in the formation of dangerous immunogenic compounds.
Sevoflurane metabolism has not resulted in the formation of TFA intermediates and the potential for hepatic toxicity is low. Instead, sevoflurane metabolism yields a compound hexafluoroisopropanol (HFIP), which does not accumulate and rapidly undergoes phase II biotransformation.
C7 is the most superior process that is visible, the spinous process of T1 may be the most prominent in some people. This is a useful landmark for finding the correct level to place a thoracic epidural.
Adult oxygen consumption = 3-4 mL/kg/min,
FRC of any healthy patient = 30 mL/kg.
[FRC (mL) ÷ O2 consumption (ml/min)] * %O2 in FRC = minutes until hypoxemia
Approximately 25-30% of rocuronium is renally excreted. It is cleared primarily by hepatic uptake and** hepatobiliary excretion**. 80% of pancuronium is renally excreted
Redistribution of heat from the core to the periphery is the largest contributor to the initial reduction in core temperature during general anesthesia. Prevention or reduction of this can be accomplished by pre-warming the patient’s extremities prior to the induction of general anesthesia.
The parts of the “Scotty dog”
Transverse process: nose
Pedicle: eye
Pars interarticularis: neck
Superior articular facet: ear
Inferior articular facet: front leg
In liver disease, the blood urea nitrogen (BUN) will be decreased due to decreased production of urea in the liver. If urea production is decreased, toxic ammonia will build up leading which can lead to cerebral edema, encephalopathy, nausea and vomiting, and asterixis.
Ammonia is converted to urea in liver hepatocytes
Labetalol has a half-life of six hours when it is administered intravenously and has an effect on blood pressure for ~16 to 18 hours. Onset 5min
Labetalol overall impact is antagonism of α1, β1 resulting in arteriolar vasodilation (α1) and reductions in the heart rate and myocardial contractility (β1).
Labetalol is also a partial β2 partial agonist contributing to arteriolar vasodilation.
Signs of hypokalemia on ECG include prolonged PR interval, pseudo-prolonged QT interval (actually the QU interval with hidden T wave), QRS prolongation, ST segment depression, decreased wave amplitude, inverted T waves, and U waves.
opiod receptors
The µ1 receptor produces the analgesic and physical dependence properties of most opioids
the µ2 receptor results in respiratory depression, miosis, euphoria, decreased gastrointestinal motility, and physical dependence.
The κ receptor mediates analgesia, dysphoria, sedation, miosis, but inhibits antidiuretic hormone release.
The δ receptor is responsible for analgesia, physical dependence, and perhaps antidepressant effects.
Meperidine’s beneficial effects are multimodal and center around the kappa opioid receptor. treats post op shivering. Meperidine metabolite can cause seizures
Meperidine has structural similarities to atropine. Which is why its associated with increases in heart rate
Certain spirometry features are characteristic of poor patient effort. The most common of these is a blunting of the initial expiratory burst. If a patient is engaging appropriately, all air within the large airways should be expelled rapidly until the small airways begin to collapse as pleural pressure increases, and then flow should rapidly begin to decline. This results in a sharp point at the top of the expiratory limb and is very apparent in patients with more significant small airway closure (obstructive lung disease). In patients providing a poor expiratory effort, this point will be blunted
A=Normal
B= Poor patient effort
C= asthma
D=COPD
Here are some useful anesthetic considerations regarding Parkinson disease:
- If on carbidopa-levodopa, avoid antidopaminergic medications
- Due to levodopa therapy, caution with sympathomimetics (e.g. ephedrine, ketamine) as they may precipitate severe hypertension
- Aim to minimize interruptions to levodopa therapy in the perioperative period
- Anticipate possible increased dyskinesias with propofol and possible rigidity with opioids
If recently taken an anticholinesterase inhibitor (e.g. rivastigmine, donepezil, or galantamine) anticipate prolonged action from succinylcholine and resistance to non-depolarizing relaxants.
- If on selegiline, avoid meperidine due to risk for serotonin syndrome
The basal ganglia is responsible for voluntary motor control. It is also involved in procedural learning, habit learning, eye movements, cognition, and emotion.
Norepinephrine is significantly metabolized by the lungs as is serotonin, bradykinin, and angiotensin-1.
Angiotensinogen is secreted by the liver and cleaved by renin, which is made in the kidney. Renin converts angiotensinogen to angiotensin-1. Angiotensin-1 is converted to angiotensin-2 by angiotensin converting enzyme (ACE), which is found extensively in the lungs.
Stimulation chassaignac tuberbacle of carotid sinus baroreceptors results in increased parasympathetic discharge This leads to hypotension and bradycardia, which can potentially be prevented by local anesthetic infiltration.
For patients with an INR > 5 with no signs of bleeding, warfarin can be held for 1 or 2 doses. If the INR is > 8, oral vitamin K should be administered.
If the INR is elevated and nonmajor bleeding is present, intravenous vitamin K should be administered and will correct INR within 6 to 8 hours.
For patients with major bleeding or requiring immediate surgery with INR >3, four-factor PCC should be given
The addition of bicarbonate to a local anesthetic increases the pH of the solution and increases the amount of the non-ionized free base. This, in turn, increases the rate of diffusion and hastens the onset of blockade of the local anesthetic.
The following strong ion changes result in the following SID changes:
↓ [Na+] → ↓ SID = acidosis
↑ [Na+] → ↑ SID = alkalosis
↑ [Cl−] → ↓ SID = acidosis
↑ organic acids → ↓ SID and acidosis
Afterload changes demonstrate an inverse relationship with the velocity of fiber shortening. Thus, a decreased afterload will result in increased fiber shortening, as the heart can easily pump more blood through the aorta.
Cerebral blood flow remains unchanged within the autoregulatory range of MAPs (50-150 mm Hg) and with PaO2 >50 mm Hg.
For every 1 mm Hg change in PaCO2, CBF changes by approximately 3%.
for every one °C decrease in temperature, CMRO2 decreases by approximately 6% with a proportional decrease in CBF
Mixing propofol with lidocaine has been shown to decrease the stability of propofol emulsion and may cause pulmonary embolism. The US FDA recommends against mixing propofol with any other therapeutic medications before administration.
For anesthesia providers risk factors for relapse from substance use disorder (SUD) are family history of substance abuse, abuse of a major opioid, and the presence of coexisting psychiatric disorder
Local anesthetics have the largest amount of systemic absorption when injected in the intercostal space, followed by caudal, epidural, brachial plexus, and lastly femoral/sciatic.
BICEPS: Blood, Intercostal, Caudal, Epidural, Plexus (brachial), Sciatic, Subcutaneous.
Etomidate’s actions on pulmonary vascular tone is by reducing bronchoconstrictive responses to acetylcholine and bradykinin. Etomidate & ketamine are perfect for RSI
Higher blood:gas partition coefficients (or blood solubilities) correspond with greater degrees of volatile agent uptake to the pulmonary blood and, thus, a slower onset of action.
inhaled agents with a high FA/FI ratio are associated with a low solubility, while higher blood solubility values are associated with a lower FA/FI ratio.
Transtracheal injection of local anesthetic through the cricothyroid membrane results in anesthesia of the recurrent laryngeal nerve. The patient will cough, but ultimately this reflex will be inhibited by the local anesthetic.
Epidural 2-chloroprocaine has an onset time of approximately 6-12 minutes, as a result of the high concentration of local anesthetic that is used. Concentrations are 2-3%
Risk factors of transient neurologic symptoms after spinal anesthesia include the use of lidocaine, ambulatory anesthesia, and the lithotomy position.
dabigatran is best corrected with idarucizumab, a drug developed for targeted reversal of dabigatran’s effects. PCC cant also reverse dabigatran
Andexanet alfa is an agent capable of specifically reversing the effects of apixaban and rivaroxaban.
Difference between minimal, moderate, and deep sedation
The Parkland formula was designed to approximate how much crystalloid fluid should be administered over the first 24 hours after burn injury.
albumin is not recommended in the first 12 hours after a burn injury because it can leak into the interstitial space
4 mL × weight (kg) × TBSA
First half given for the first 8 hours, and the second half given for the next 16 hours
Barbiturates undergo slow terminal elimination via hepatic metabolism, biliary conjugation, and renal excretion
Methohexital has an average elimination half life of 4 hours
The anesthetic action of barbiturates, like most IV anesthetics, are primarily terminated by redistribution. The drug redistributes from the central lipophilic tissues of the brain to the peripheral lean muscle compartments, and lastly to the fat and less well-perfused tissue compartments.
The great radicular artery (aka arteria radicularis magna or artery of Adamkiewicz) originates from the aorta between the T9 and T12. The anterior spinal cord is perfused by a single Anterior spinal artery (ASA) with collateralization from the radicular arteries. Interruption of the great radicular artery may result in ASA syndrome, which includes bilateral lower extremity paraplegia as well as bowel and bladder dysfunction.
Sensation and proprioception are classically spared as the posterior portion of the spinal cord is supplied by two Posterior spinal arteries. Spinalcord perfusion pressure = MAP - CSF pressure. CSF pressure is measured via a lumbar spinal drain. Arterial pressure augmentation and CSF pressure reduction are therefore the best methods by which SCPP may be optimized.
The respiratory centers in the brain are located in the cerebral medulla, including both dorsal (inspiration) and ventral (expiration) respiratory groups.
The dorsal group is further controlled by two specific pontine areas; the lower pontine center (apneustic) is excitatory, while the upper pontine center (pneumotaxic) is inhibitory.
The epidural’s improved postoperative pain control improves cardiovascular outcomes, allows a more rapid return of gastrointestinal function, reduces pulmonary complications, reduces the incidence of thrombotic events, and improves participation in postsurgical rehabilitation.
Concentration-calibrated variable bypass vaporizers adjust the ratio of fresh gas flow between the bypass flow path and the vaporizing chamber flow path to achieve the desired percentage of volatile anesthetic delivered to a patient. The ratio of flows between the two paths is called the splitting ratio.
Infants are more likely than adults to have bradycardia during laryngoscopy and intubation due to a predominance of the parasympathetic nervous system.
The onset of action after an intubation dose of rocuronium (0.6 mg/kg) is approximately one to two minutes.
Dexamethasone’s antiemetic activity is likely mediated via central inhibition of the nucleus tractus solitarii. 8-10mg can help reduce pain, sore throat post op. Can cause perianal burning if given while awake
MRI is the best imaging modality for patients with possible neuraxial pathology.
Neuraxial anesthesia for a suspected epidural hematoma are acute motor weakness, progressive sensory loss, fever, incontinence. Rarely happens
The gag reflex arc (pharyngeal reflex) is controlled by the glossopharyngeal nerve (afferent limb) and the vagus nerve (efferent limb).
An esophageal balloon is useful in determining the transpulmonary pressure. Transpulmonary pressure can guide PEEP titration to improve the patient’s respiratory mechanics.
A bronchopleural fistula is a connection between the bronchi and the pleural space. This communication between the airways and the pleural space increases the risk of airway infections and makes mechanical ventilation difficult. Will have an airleak if chest tube is present
Vasopressin is associated with increased platelet aggregation, which results in a pseudothrombocytopenia
Low-dose vasopressin infusions have been shown to increase nitric oxide levels at the endothelial level; this may be the cause of cerebral, renal, and pulmonary vasodilation while mesenteric and peripheral vascular beds become constricted.
According to the Haldane effect, deoxygenated hemoglobin has a higher affinity for CO2. After the deoxygenated hemoglobin reaches the lungs, the high O2 concentration decreases this affinity, and the CO2 is released.
An emergency exists when life or limb is threatened if the patient is not in the operating room within six hours
An urgent procedure is required when life or limb is threatened if the patient is not in the operating room within 24 hours
A time sensitive procedure can be delayed one to six weeks for evaluation if it will change management
An elective procedure can be delayed up until one year
Norepinephrine has an affinity for the following: α1 > α2 > β1. Because of its affinities, administration of norepinephrine results in intense vasoconstriction (with reflex bradycardia) and increased myocardial contractility. As a result, norepinephrine elevates arterial blood pressure without significantly affecting cardiac output.
Isoproterenol is a nonselective β-agonist; its use leads to an increase in heart rate and cardiac output via β1 and a decrease in blood pressure via β2.
The oxygen analyzer will be the first device to detect a hypoxic mixture in the event of a pipeline crossover or mix-up where oxygen is replaced. A key step in the management of a pipeline supply issue is disconnecting the pipeline supply gases.
The hypoxic guard, or proportioning system, is the system that links oxygen flow to nitrous oxide flow to prevent a hypoxic mixture. These systems are pressure and flow based, thus a crossover will still cause a hypoxic mixture.
The nasopharynx provides an accurate measure of cerebral temperature, particularly during hypothermic cardiopulmonary bypass.
Pulmonary artery temperature is considered the gold standard for determining core body temperature. It is not used during cardiopulmonary bypass.
Postop ulnar nerve injury occurs more commonly in males and very thin or obese patients.
Nerve conduction studies are beneficial in evaluating both motor and sensory deficits.
Electromyography can help determine the timing & location of the nerve injury.
E-sized cylinders
In order to activate the nicotinic acetylcholine receptor (nAChR), either 2 acetylcholine (ACh) molecules or 1 succinylcholine molecule must bind.
The postjunctional nicotinic acetylcholine receptor are composed of 5 subunits (2 alpha, 1 beta, 1 delta, and 1 epsilon).
Due to transection of the cardiac autonomic plexus during transplantation, the donor heart will not exhibit reflex responses such as reflex bradycardia with the administration of phenylephrine nor will it respond to hypovolemia or exercise. With the loss of parasympathetic tone, the resting heart rate is usually 90 to 110 bpm, and there is no heart rate response to anticholinergics.
Leads II and V5 is the preferred lead combination because it allows for rhythm monitoring and is sensitive for detecting myocardial ischemia. When it is used alone, V5 has the highest sensitivity for myocardial ischemia.
Caution should be taken with anticholinergics in the elderly because the elderly have a decrease in acetylcholine-induced transmission in the central nervous system and an increase in the permeability in the blood-brain barrier allowing for increased central effects.
Contraindications for scopolamine are acute angle-closure glaucoma and allergy to belladonna alkaloids.
Anticholinergics, including scopolamine, should be avoided in patients with preeclampsia because they can promote seizures (eclampsia).
Nitroglycerin is converted to nitric oxide, sildenafil inhibits its breakdown by phosphodiesterases, and inhaled nitric oxide convert GTP into cyclic guanosine monophosphate (GMP).
Increases in intracellular cyclic GMP will result in smooth muscle relaxation, but can also exert a potent anti-inflammatory effect and inhibit platelet aggregation.
In newborns, the dural sac typically ends at S3 and the conus medullaris at L3. In adults, the dural sac typically ends at S2 and the conus medullaris at L1-L2
With a complete unilateral injury to the recurrent laryngeal nerve, both the abductor and the adductor fibers would be involved causing the affected vocal cord to remain in a paramedian position.
A partial injury affecting abductor fibers primarily, however, would place the vocal cords in a midline position making a bilateral partial injury a potential airway emergency.
Hagen–Poiseuille equation
radius is most impactful
Equation can be rephrased as
Resistance = 8ηl / πr^4
The figure shows the time it takes for isoflurane, sevoflurane, and desflurane concentrations to decrease by 90%
Muscle weakness from high magnesium concentrations results from inhibition of calcium influx, leading to reduced acetylcholine release.
A rapid bolus of Mannitol can transiently increase ICP. Prolonged infusions of mannitol have been shown to reverse the osmotic gradient and increase ICP.
CBF decreases 1 to 2 mL/100 g/min for each 1 mmHg decrease in PaCO2.
High PaCO2 leads to low CSF pH, which in turn causes release of vasodilator prostaglandins and nitric oxide.
Propofol infusion syndrome, or propofol toxicity, occurs in patients receiving prolonged infusions of propofol and manifests with profound bradycardia coupled with metabolic acidosis, lipemia, rhabdomyolysis, and hepatic dysfunction.
A serum lipemia will often occur prior to the onset of other symptoms, which leads to impairment of hepatic lipid regulation in early propofol toxicity. regularly serum triglyceride levels should be checked
Immature extrajunctional acetylcholine receptors are unique because of the γ (gamma) subunit type they contain. Both mature and immature receptors contain α1 (alpha 1), β1 (beta 1), and δ (delta) subunit types.
Coronary perfusion pressure of the left ventricle = aortic diastolic pressure − left ventricular end-diastolic pressure (LVEDP)
Clevidipine is an IV, dihydropyridine calcium channel blocker that is rapidly metabolized by plasma/red cell esterases providing its short duration of action.
Pulmonary edema can be seen with naloxone administration, especially in larger bolus doses.
The muscles of forced exhalation
Diaphragm,
external/internal oblique muscles, rectus abdominis,
transversus abdominis
Inhalational accessory muscles
scalene
External intercostal muscles
sternocleidomastoid muscles, pectoralis major, pectoralis minor, serratus anterior, latissimus dorsi
Levator labii superioris alaeque nasi muscle
quadratus lumborum.
The interscalene block (ISB) is used to anesthetize the shoulder and proximal upper extremity. The ISB primarily anesthetizes the ventral rami of C5-C7. The C5-C6 nerve roots are identified in the interscalene groove between the middle and anterior scalene muscles. When it is performed properly, the ISB will almost always also block the ipsilateral phrenic nerve, causing hemidiaphragmatic paralysis. The ISB is not recommended for procedures of the forearm and hand because the ulnar nerve (C8-T1) is usually spared.
AS, anterior scalene muscle, MS, middle scalene muscle; SCM, sternocleidomastoid muscle.
When opioids are used for neuraxial anesthesia, hydrophilic opioids spread more extensively and persist longer within the cerebrospinal fluid or epidural space.
Typically, the tourniquet can be used safely for 2 hours. To increase the duration of the tourniquet use, a perfusion break can occur by deflating the tourniquet
An increase in plateau pressure (Pplat) reflects decreased respiratory system compliance (CRS), which is composed of lung and chest wall compliance. Therefore, conditions that decrease CRS such as pulmonary edema, acute respiratory distress syndrome, transfusion-related acute lung injury,pleural effusion
Sugammadex does affect the efficacy of oral contraception. It is recommended to use alternative means of birth control for 1 week after sugammadex administration because sugammadex can bind to progesterone.
Cormack-Lehane system
Pulmonary vascular resistance (PVR) is affected by lung volumes. It is lowest at functional residual capacity (FRC), while increasing or decreasing lung volumes beyond FRC results in an increase in PVR.
Magnesium & Dextromorthophan have NMDA antagonist properties
SSRI may inhibits the Cytochrome P450 system and may prolong the actions of different anesthetic drugs
The modified Mallampati score is inadequate as a stand-alone test to predict difficult tracheal intubation with a sensitivity of 35% in predicting difficult intubation or laryngoscopy
Receptor Sites
α2 (postsynaptic)
Coronary constriction
Inhibition of insulin release
Decreased bowel motility
Analgesia
α2 (presynaptic)
Inhibit norepinephrine release in vascular smooth muscle
Inhibition of CNS activity
Glasgow-Coma Scale (GCS)
CO2 response curve
Cushing Syndrome can cause Hypokalemic metabolic alkalosis as a result of excess cortisol mimicking the action of aldosterone.
Reynolds number
(R)= velocity * density * diameter / viscosity
When R < 2000, laminar flow is present. When R > 4000, turbulent flow is more likely.
The halothane-caffeine contracture test is considered the gold standard for malignant hyperthermia diagnostic testing.
mixed venous oxygen tension/saturation
Postoperative cerebral hyperperfusion syndrome is an abrupt increase in cerebral blood flow with the loss of autoregulation in the surgically reperfused brain. This syndrome is manifested as headache, seizure, neurological deficits, brain edema, and hypertension. Typically, this syndrome does not occur until several days after a CEA.
RCRI
The modified Aldrete scoring system is used to determine when a postoperative patient may be discharged from phase I postanesthesia care unit (PACU) or whether a patient may bypass phase I PACU and go directly to phase II from the operating room.
Components of the modified Aldrete scoring system are activity, breathing, blood pressure, consciousness, and oxygen saturation.
ASRA Guidelines for Neuraxial Procedures and Anticoagulation (Heparins)
Phases of Emergence From General Anesthesia
Regular insulin 10 units IV should be administered with 25 grams of IV dextrose and the blood glucose level should be monitored. If the patient has a blood glucose > 250 mg/dL, then the administration of dextrose can be withheld. A dose of 10 units lowers serum potassium by approximately 1 mEq/L.
An opioid with a pKa less than physiologic pH (~7.4) will have a much greater nonionized fraction whereas an opioid with a pKa >7.4 will have a greater ionized fraction.
The glycocalyx forms a protein-poor subglycocalyceal layer and is freely permeable to water and electrolytes, although it excludes large molecules such as proteins. When constant capillary pressures are assumed, the primary determinant of transcapillary flow is the plasma-to-subglycocalyceal layer colloid oncotic pressure gradient and not the plasma-to-interstitial fluid colloid osmotic pressure gradient, as has been traditionally taught. Damage to this layer results in increased vascular permeability, which causes interstitial edema and diminished vascular responses to shear stresses.
In periods of acutely decreased hydrostatic pressures (capillary hypotension), an autotransfusion of up to 500 mL may occur from the subglycocalyceal layer into the plasma circulation as the hydrostatic pressure gradient between the subglycocalyceal layer and plasma decreases. Colloid infusion in this situation increases plasma volume, while crystalloid increases total intravascular volume, both plasma and subglycocalyceal layer.
It is important to note that atrioventricular (AV) nodal blockers (eg, adenosine, diltiazem, verapamil, beta-blockers) are contraindicated in Wolff-Parkinson-White (WPW) syndrome and must be ruled out before administration of any AV blocking drug.
In WPW, AV nodal blockers prevent normal physiologic conduction through the AV node, leading to preferential conduction down the accessory or preexcitation pathway that can lead to a fatal arrhythmia.
Cefazolin should be redosed if there is > 1500ml of blood loss
If a tourniquet is being used, the antibiotic dose should be completed at least 5 minutes prior to tourniquet inflation
Both sympathetic and parasympathetic preganglionic neurons are cholinergic
Hypoxic Pulmonary Vasocontriction
The function of modern pacemakers is generally designated using a 3 letter code. The first letter indicates the heart chamber(s) paced, the second is the chamber(s) for which intrinsic electrical activity is sensed, and the third is response to sensing. The presence of an R as a fourth letter means the pacemaker is rate-responsive and will increase its rate, for example, when it senses exercise.
When a patient’s intrinsic heart rate is greater than the set pacemaker rate along with a pacemaker in an asynchronous mode, an R-on-T phenomenon may occur leading to ventricular tachycardia or ventricular fibrillation.
To prevent rebreathing in a semiclosed circle system,
the fresh gas inlet cannot be placed between the patient and the expiratory valve
APL valve cannot be placed between the patient and the inspiratory valve.
Left sided central line placement can cause
Thoracic duct injury
ipsilateral supraclavicular swelling or unilateral pleural effusions. The pleural effusion will most likely manifest as gradually worsening dyspnea and pleuritic chest pain.
A double-cuff tourniquet can be used to limit the discomfort caused by a tourniquet during a Bier block.
When tourniquet pain begins to occur, the distal cuff is inflated over the area that had been previously anesthetized, followed by deflation of the proximal cuff to decrease the pain over the proximal cuff.
Obstructive Sleep Apnea Criteria
The common peroneal and tibial nerves are located superficial and lateral to the popliteal artery.
The popliteal artery is the most anterior structure on ultrasound from the popliteal fossa.
The normal right ventricle is perfused throughout the cardiac cycle. Left ventricle is perfused during diastole
Sedatives and anxiolytics should be given in smaller, incremental doses in obese patients
Obesity is no longer considered a risk factor for aspiration.
Types of needles
Huber= non cutting epidural
Quincke = cutting
Whitacre=pencil cutting
Symptoms of Hypermagnesemia
Nearly all anesthetic agents have a benzene ring in their structure
PRBCs, fresh, frozen plasma, can be transfused through a fluid warmer. Platelets can be transfused through a fluid warmer
When to give steroids for chronic users of prednisone
The external iliac arteries become the common femoral artery after the groin crease. The common femoral artery branches off into the deep femoral artery (profunda femoris) and the superficial femoral artery. The deep femoral artery supplies the tissue and muscles in the thigh and proximal part of the femur. The superficial femoral artery continues down the leg and becomes the popliteal artery at the knee crease. The popliteal artery branches off into the anterior tibial artery and the tibiofibular (tibioperoneal) trunk. The tibioperoneal trunk bifurcates into the posterior tibial artery and the fibular (peroneal) artery.
The most common causes of atlantoaxial instability include trauma, achondroplasia, Down syndrome, and rheumatoid arthritis.
ASA risk factors of a Difficult Airway
Disc Herniations
Meperidine is a weak serotonin reuptake inhibitor and can therefore lead to serotonin syndrome if given to patients taking MAO inhibitors.
Epidural blood patch is performed by injecting 15 cc patient blood into the epidural space to plug off the leakage of CSF from the post dural puncture. Must be performed within 24 hours of onset of symptoms.
Maintenance of Certification in Anesthesiology, anesthesiologists
Tetanic stimulation of a nerve will result in an accumulation of calcium within the presynaptic neuron and result in a greater than normal release of acetylcholine into the synaptic cleft.
Nitrous oxide percentages and increase in bowel distention
