Physiology Flashcards
Why do elderly people take longer to wake up.
Higher body fat –> higher Vd for lipophilic drugs
Also, decreased GFR, longer effect of drugs due to decreased elimination
Decreased liver volume, phase I metabolism, BF
Decreased albumin (increased FF of drugs)
What happens to the CV system in the geriatric population?
Stiffer arteries –> higher pulse pressure, increased afterload–> LVH –> diastolic dysfunction –> more dependent on atrial kick for filling
Decreased SV under stress due to less diastolic filling from less compliant LV
Decreased beta receptor responsiveness, increased
norepinephrine levels
What happens to the respiratory system in the elderly?
Decreased tidal volume
Increased dead space, decreased diffusion capacity
Increased closing capacity –> decrease in PaO2, increased shunt
Closing capacity > FRC
Increase in lung compliance
Decrease in chest wall compliance
Diaphragm flattening
Decreased hypoxemic and hypercapnic respiratory drive
What are the CNS effects of aging?
Brain mass decrease
Lower NT release and binding sites
Lower MAC and local anesthetic requirements
More spread of local in spinal! And longer duration of action
How do you diagnose postoperative cognitive delirium?
Neurobehavioral testing
What are the anesthetic considerations with obesity?
Decrease FRC - time to desaturation
Difficult airway - thick neck
Decreased chest wall compliance –> atelectasis
CO2 retention due to airway closure –> hypercapnic respiratory drive is altered, sensitivity to opioids?
Drug administration- large propofol doses for maintenance (based on TBW, higher Vd due to fat content
Increased fibrinogen, factor VII and VIII - procoagulant state –> DVT prophylaxis!
What are the anesthetic considerations for burn patients?
More sensitive to benzodiazepines due to decreased albumin (increased Ff of drug)
Opioid resistance due to high tolerance
Increased extrajunctional receptors within 24 H if > 10% TBSA - cannot give succinylcholine for 1 year afterward!
Insulin resistance due to massive catecholamines surge
Decreased alpha glycoproteins - need higher doses of Bb and local anesthetics
Heat loss!
Dehydration : Parkland formula- 4 ml X %TBSA X weight. Then give the first half over 8 hours, then next half over 16 hours
A patient has > 30% of TBSA, what happens with NMB?
Develop resistance at 1 week with peak resistance at 4-6 weeks
Slower onset of action, decreased duration, decreased effect because now more receptors.
NEED HIGHER AND MORE FREQUENT DOSING
What are the effects of hypothermia?
Cardiac: Decreased CO Alters cardiac conduction --> arrythmias Shivering increases myocardial oxygen demand Decreased oxygen unloading
Metabolic:
Hyperglycemia due to decreased insulin release
Decreased metabolism –> decreased drug clearance
Heme:
Decreased fibrinogen synthesis and platelet dysfunction –> bleeding risk
Decreased immune function –> PNA, wound healing!
CNS:
Decreased respiratory drive
Decreased CMRO2 and CBF –> AMS
You are doing a TURBT on an elderly patient with recent MI, what are you worried about with this case?
TURBT syndrome (from open venous sinuses) causing fluid overload --> CHF and MI from increased demand AMS due to acute brain swelling and decreased in sodium Decreased hypotonicity in plasma --> acute intravascular hemolysis
What are other complications of TURBT?
Hypothermia DIC from release of thromboplastin from prostate Dilutional TCP Prostatic capsule rupture Sepsis Bladder perf
Patient has DIC after TURBT, what do you do?
Get a TEG, CBC, coags
Start AMICAR, give bolus of 5 grams then start drip at 1 g/hour
Give heparin and clotting factors and platelets
Consult heme
Patient is getting a TURBT, what are all the possible complications?
Bladder perforation Fluid overload Water intoxication DIC Septicemia Hypothermia
What are the advantages of using regional anesthesia?
Reduces incidence of venous thromboembolism
Patient awake for mental status checks
How do you treat autonomic hyperreflexia?
Remove the stimulus
Deepen the anesthetic!
SL nifedipine
What are the anesthetic considerations for pericardial tamponade?
Fast and full
Maintain spontaneous ventilation - avoid PPV!
Avoid phenylephrine due to reflex Brady
What do you want preoperatively for a mediastinal mass?
Chest X-RAYS
CT with contrast (not sensitive for obstruction)
High-resolution CT with 3 D airway reconstruction
Bronchoscopy
TEE - to assess heart function, look for tamponade/collapse, rule out for reason for fluid overload (if patient is overloaded). Do supine and standing
Flow volume loops : would show flattening of both inspired and expiratory loops
How would you proceed with anesthesia in someone with a mediastinal mass?
- Fluid bolus to increase preload and ensure filing of the right heart and ensure no cardiac collapse from external compression
- Awake FO intubation sitting up with topicalization and ketamine. ENT standing by to do rigid bronchoscope
- Then paralyze with judicious use of NMB (remember if MG - very sensitive to NMB)
What things do you want in the room for a mediastinal mass case?
Rigid bronchoscope
CPB by pass machine
Patient has a pacemaker and they are using mono polar electrocautery. The patient has an R on T phenomenon. What do you do?
Cease all electrocautery
Remove magnet from ICD - should reinstate it
Zoll pads on (just in case). Do not place directly over device
Shock as appropriate/ACLS
What is platelet transfusion threshold for major elective surgery?
< 50 K
What are the advantages of veno-veno bypass in liver transplant?
Preserves cardiac output because venous return from the lower extremities and viscera is uninterrupted
Effectively decompressed the portal system and decreases splanchnic congestion
(Cannula in IVC and portal vein to axillary vein)
What is the advantage of a piggy back OLT?
Preserves systemic blood flow through a preserved IVC
What happens during reperfusion of the liver?
Increase in potassium
Increase in preload
Increase in lactate and hydrogen ions
Get myocardial stunning, increased preload –> bradycardia
Decreased SVR
Increased fibrinolysis from tPA in the graft
What are delayed hemolytic reactions due to?
Antibodies to non-D antigens of the Rh system
What are the characteristics of a delayed hemolytic reaction?
Happens 2-21 days after transfusion
Symptoms of fever, jaundice, malaise
Dx: Direct Coomb’s
What is a febrile reaction to a transfusion due to?
Antibodies to donor WBCs or platelet
No hemolysis occurs
What is urticaria from transfusion due to?
Sensitization to plasma proteins
Give antihistamine and steroid
What is R time?
Initial clot formation (5-10 minutes)
Function of clotting factor deficiencies, heparinization, TCP
What is k time?
Coagulation rate (1-3 minutes) Function of clotting factors, platelets, fibrinogen
What is the alpha angle?
Rate of fibrin build up and cross-linking (50-70 degrees)
Function of fibrinogen
What is MA
Maximal amplitude = clot stability (50-70 mm)
Function of platelets and fibrinogen
What is LY30?
Degree of lysis (0-8 percent)
Need anti fibrinolytic therapy
What is a phase 1 block?
It is a depolarizing block due to perijunctional sodium channels that inactivate with continued depolarization and cannot reopen until the end plate repolarizes.
The end plate cannot repolarizes as long as the depolarizing muscle relaxant binds Ach receptors
What is a phase II block?
When there is conformational change in the Ach receptor
Can happen after prolonged depolarization
What is fade of train of four from?
Blocking prejunctional receptors that play a role in mobilizing Ach for sustained contraction.
Indicative of a phase II, nondepol block
Clinical recovery = no fade
What is posttetanic potentiation?
It is the ability of a tetanus stimulation (sustained stimulus of 50-100 Hz for 5 seconds) to cause Ach mobilization in the NMJ.
If no posttetanic twitches - you are fully blocked
Why is a drop in afterload detrimental in aortic stenosis?
Because these patients have a fixed cardiac output and inability to increase cardiac output.
Usually LVH due to increased afterload from stenosis valve –> at risk for sub endocardial ischemia with hypovolemia and tachycardia
Why is Afib bad in aortic stenosis?
It significantly increases myocardial oxygen demand, decreases diastolic (coronary perfusion) time in an already hypertrophic muscle, LV filling time and atrial kick contribution to LV filling which leads to significant reduction in CO
What are EKG signs of PE?
New Rbbb Peaked P waves ST changes Right axis deviation SVT arrythmias
How would you treat a PE?
ABCs 100% FiO2, secure airway if needed Vasopressors to support the heart and decrease PVR - milrinone ICU transfer Anticoagulation
What are your concerns with SVC syndrome?
Impairment of venous drainage causing mucosal and airway edema
Increased ICP/impaired CPP
Unreliable drug delivery in the right arm
Potential for massive hemorrhage
Fluid management - too much will lead to more engorgement
Postop respiratory complications secondary to edema and mass compression
Avoid coughing and bucking during emergence because could cause acute airway obstruction
What are you concerns with mediastinoscopy?
Right innominate artery compression (need right radial arterial line or oximeter) Venous air embolism PTX Rupture of artery Pericardial tamponade
What are the contraindications to mediastinoscopy?
Severe tracheal deviation CVA Severe cervical spine disease with limits neck extension Previous chest radiation Thoracic aortic aneurysm
What concerns you about a patient with longstanding hypertension?
They are at increased risk for blood pressure lability, cerebral ischemia secondary to rightward shifted cerebral auto regulation, intraoperative end organ ischemia, arrythmias, CHF, hypotension, HTN, stroke.
For a patient with longstanding uncontrolled hypertension, what would you do preoperatively and then intraoperatively?
I would get a thorough history focused on blood pressure medications, BP control, causes of the HTN and presence of end organ damage
Tests: EKG, BMP
Maintain within 20% of baseline or around 140/90
Who would you delay elective surgery in for hypertensive control?
SBP readings over 180
DBP over 110
End organ damage
Cardiac, carotid, or pheo resection
What are signs/symptoms of SVC syndrome?
Cough, dyspnea, JVD, headache, Orthoptera, hoarseness, papilledema, facial cyanosis, dysphagia, chest pain
How would you induce a patient with SVC syndrome?
Head up for drainage
Awake FO
How would you manage hypotension?
Check pulse and other monitors EKG for arrythmia or cardiac ischemia Ensure adequate oxygenation/ventilation Auscultation for PTX, HTX, bronchospasms, endobronchial intubation Reduce volatile Open fluids, give vasopressors Trendelenburg Send ABG If these interventions failed to resolve the problem, I would consider placing CVC, TEE, Precordial Doppler
What is base excess?
The amount of strong acid or base needed to return 1L of whole blood back to a ph of 7.4 and PaCO2 of 40.
Represents the nonrespiratory component of acid-base disturbance
Used as a marker for volume resuscitation
Negative = acidosis Positive = alkalosis
What is the Hamburger shift?
Bicarbonate anions exchange for extracellular chloride (part of the hemoglobin buffer for H+ made when CO2 combines with water and then dissociates to make bicarbonate by carbonic anyhdrase
What would you do for someone with hemolytic anemia ?
Do physical exam - look for pallor, fatigue, SOB
Check labs: CBC with reticulocyte count, LFTs, BMP, UA
Eliminate causes: hypoxia, hypothermia, acidosis, hyperglycemia, infection, drugs
Give fluids and mannitol
What is DIC?
A pathological activation of the coagulation system resulting in widespread microthrombi, consumption of coag factors, TCP, hemolytic anemia, diffuse emboli, thromboembolic events.
What are risk factors for DIC.
Amniotic fluid exposure
Hypovolemia
Vascular endothelial injury
Pre-eclampsia
What is TACO?
Large volumes of fluids causing increased pulmonary blood flow and therefore increased pulmonary capillary blood pressures
How can you tell the difference between TRALI and TACO.
TRALI:
PAOP less than 18
Normal BP, euvolemia, normal heart function
High plasma protein content of edema
TACO:
HTN, S3, peripheral edema, JVD, impaired cardiac function, higher BNP, low plasma protein content of edema
What is the pathophysiology of TRALI?
Anti-donor HLA antibodies causing neutrophil activation which leads to endothelial damage, cap leakage and ALI
What is the treatment for TACO?
Diuretics
Inotropes as needed
Ensure adequate Hct for oxygen carrying capacity and lowering pulmonary blood flow
What is the treatment for TRALI?
No diuretics or steroids (don’t confer benefit)
Stop transfusions. Supportive ventilation. Usually recover within 96 hours