Anesthesia Flashcards
Definition of hypotension/shock?
Inadequate tissue perfusion and delivery of oxygen to tissues which can result in ischemia followed by necrosis and lead to end organ damage.
Pathophysiology of hypotension/shock?
Hypotension (BP = CO (SV x HR) x SVR).
o SV decreases in cardiogenic, hypovolemic, adrenal, hypothyroidism and obstructive shock
o SVR decreases in distributive shock (septic, anaphylactic, neurogenic, hepatic)
Early signs of hypotension/shock?
^RR, ^HR, narrow pulse pressure, reduced capillary refill, cool extremities, reduced central venous pressure
Late signs of hypotension/shock?
hypotension + altered mental status, reduced urine output
Estimated SBP Based on Palpable Pulse
RADIAL (>80 SBP), FEMORAL (>70 SBP), CAROTID (>60 SBP)
Approach to shock: Step 1: How stable is the patient?
▪ Airway – Can’t protect airway – choking, stridor, purse lip breathing
▪ Breathing – O2 sats
▪ Circulation – assess skin temperature, measuring capillary refill time (CRT), feel pulses
▪ If patient isn’t stable call a code blue
Approach to shock: Step 2: Get another set of vitals
▪ 6 vitals (including glucose)
▪ Check the JVP!
High = cardiogenic or obstructive
Low = hypovolemic or distributive
Approach to shock: Step 3: OIL the patient
▪ O2
▪ IV
▪ Lines (BP cuff, sat probe, cardiac monitor, foley catheter)
Approach to shock: Step 4: Warm shock vs cold shock
Cold shock (hypovolemic, neurogenic) – Narrow PP, vasoconstricted
Warm shock (sepsis, anaphylaxis) – Wide PP, vasodilated
Investigations for cold shock?
Investigations: Blood work (Cr, lytes), serum lactate (>4 needs to go to ICU)
Investigations for warm shock?
Investigations: Blood cultures, urine cultures
Treatment for cold shock?
Tx: Fluids (20-30 ml per kg) isotonic (crystalloid)– About 1-2L
Treatment for warm shock?
Tx: empiric antibiotics, fluids
What are the causes of shock?
(SHOCKED): Septic/Spinal (neurogenic), Hypovolemic, Obstructive, Cardiogenic, Anaphylactic, Endocrine (e.g. Addisonian crisis, thyrotoxicosis/hypothyroid), Drugs
o Hypovolemic: Intravascular volume loss, hemorrhagic, fluid loss
o Cardiogenic: Arrhythmia, AMI, valvular, cardiomyopathy, pericarditis/PE
o Distributive: Vasodilatory, sepsis, anaphylaxis, neurogenic, drugs, addisons crisis
o Obstructive: Tension PTX, tamponade, PE
o Drugs: vasodilators, high spinal anesthetic interfering with sympathetic outflow
What should be done on physical exam for shock?
▪ General – ABCDE, vital signs (orthostatic VS), GCS
▪ Derm – expose entire body. Examine for signs of trauma, hives, rashes
▪ Extremities - peripheral pulses, skin temperature, capillary refill
▪ HEENT: Inspect for angioedema, central cyanosis, tracheal deviation. JVP assessment
▪ CV/RESP: Inspect for asymmetric chest movement, apnea. Percuss for hyperresonance (pneumothorax), dullness (consolidation, hemothorax). Auscultate for cardiac friction rub, breath sounds, crackles. JVP – distributive/hypovolemic vs cardiogenic/obstructive
▪ URO: urine output
▪ ABDO: Inspect for abdo distension, bruising around umbilicus or flanks. Palpate for rigid/tender abdomen, masses
▪ NEURO: Hyperreflexia, Decrease strength of limbs, lack of sensation in perianal area
Definition of obstructive shock?
Definition: Obstruction of blood into/out of the heart
S/S of obstructive shock?
Increased JVP, distended neck veins, increased systemic vascular resistance, insufficient cardiac output (CO), depending on cause, may see pulsus paradoxus, Kussmaul’s sign, or tracheal deviation. Cool extremities
Causes of obstructive shock?
Tension pneumothorax, cardiac tamponade, pulmonary embolism, other emboli, CHF
Management of obstructive shock?
o General: supplementary oxygen and IV fluids, vasopressors
o Needle Decompression: or tube thoracostomy for tension pneumothorax/hemothorax
o Pericardiocentesis: pericardial tamponade
Definition of cardiogenic shock?
Definition: Heart not being able to produce enough power
Signs of cardiogenic shock?
Low CO, high SVR, high HR, low urine output
o Also get an decrease in ATP and increase in lactic acid (switch to anaerobic). An increase in lactic acid results in increase in protons leading to metabolic acidosis
o Signs of left-sided heart failure (bilateral crackles on chest exam)
Causes of cardiogenic shock?
Myocardial dysfunction, myocarditis, aortic valve stenosis, arrhythmias, dilated cardiomyopathy
Symptoms of cardiogenic shock?
Cool extremities due to peripheral vasoconstriction, cyanosis
Management of cardiogenic shock?
o General: supplementary oxygen and IV access
o Inotropic Agents: vasopressors (epinephrine), dobutamine (positive inotrope)
o Intra-aortic balloon pump: encourage blood flow, alleviate cardiac workload
o MI:
▪ Angioplasty/Stenting: via cardiac catheterization
▪ Thrombolytics: clot busters or fibrinolytics to dissolve clots
▪ Surgery: coronary artery bypass, repair, ventricular assist device, transplant
Definition of distributive shock?
Definition: This type of shock is due to decreased SVR (vessels are very dilated)
What is Beck’s triad for cardiac tamponade?
Beck’s triad – High JVP, low BP, decreased heart sounds
What is neurogenic shock and the S/S?
Neurogenic Shock: decreased sympathetic tone – watch for hypotension (loss of sympathetic nervous system tone), bradycardia (unopposed PNS), poikilothermia (lacking SNS so no shunting of blood from extremities to the core) – occurs within 30 minutes of spinal injury at level T6 or above, lasting up to 6 weeks
o S/S: hypotension without tachycardia or peripheral vasoconstriction (warm skin)
Treatment of neurogenic shock?
Treatment: provide airway support, fluids, atropine (for bradycardia), vasopressors for BP support – get sBP >100)
What is spinal shock?
Absence of all voluntary and reflex activity below level of injury
S/S of spinal shock?
Decreased reflexes, no sensation, flaccid paralysis below level of injury, lasting days to months
Definition of septic shock?
Fulfill the criteria for sepsis and who, despite adequate fluid resuscitation, require vasopressors to maintain a mean arterial pressure (MAP) ≥65 mmHg and have a lactate >2 mmol/L (>18 mg/dL).
Pathophysiology of septic shock?
Gram -ves release endotoxins which act on cells to release prostaglandins and leukotrienes which stimulate the mast cells to release histamines, PG, LT, proteases and those dilate the blood vessels and make them leaky (permeability) and thus decreases BP
▪ The WBC will come to fight the bacteria which releases factors like IL-1 and TNF-a which goes to the hypothalamus which releases PGE2 which increases your body temperature (fever)
▪ Endotoxins also increase plasminogen activator inhibitor-1 results in more microvascular clots which decreases perfusion to tissues.
Common triggers of anaphylactic shock?
Foods (nuts, shellfish, etc.), stings, drugs (penicillin, NSAIDs, ACEi), radiographic contrast media, blood products, latex
S/S of severe anaphylactic reaction?
Severe wheezing, laryngeal/pulmonary edema, shock
S/S of moderate anaphylactic reaction?
Generalized urticaria, angioedema, wheezing, tachycardia
Treatment of severe anaphylactic reaction?
Treatment: ABCs, may need definitive airway (e.g. ETT) due to airway edema, epinephrine, antihistamines, steroids (hydrocortisone 100mg IV) or methylprednisolone (1 mg/kg IV q6g x 24h), large volumes of crystalloid may be required
Treatment of moderate anaphylactic reaction?
Treatment: epinephrine 0.3-0.5mg (IM in lateral thigh) to constrict the blood vessels, antihistamines (Benadryl 25-50mg IM), Salbutamol 1cc via MDI
What is anaphylactic shock?
Exaggerated immune mediated hypersensitivity reaction that leads to systemic leukotrienes and histamine release (from mast cells), increased vascular permeability and vasodilation – regardless of etiology the presentation and management is the same – either allergic (re-exposure to allergen) or non-allergic (e.g. exercise induced). The increased vascular permeability in the lungs constricts the bronchi and causes respiratory distress. Laryngeal edema constricts your larynx and makes it hard to breath
S/S of distributive shock (septic)?
o Arterial hypotension o Temp >38.3C or <36C o High HR o Tachypnea o LOW JVP o Signs of end-organ perfusion: Warm, flushed skin, decreased cap refill, cyanosis, additional signs of hypoperfusion include altered mental status, obtundation or restlessness, and oliguria or anuria.
Immediate evaluation and management of distributive shock (septic)?
o Stabilize respiration - O2 +/- intubation (respiratory support)
o Establish venous access: A central venous catheter (CVC) can be used to infuse intravenous fluids, medications (particularly vasopressors), and blood products, as well as to draw blood for frequent laboratory studies
o Investigations:
▪ CBCd + liver function tests and coagulation studies including D-dimer
▪ Serum lactate
▪ Peripheral blood cultures (aerobic and anaerobic cultures from at least two different sites), urinalysis, and microbiologic cultures from suspected sources (eg, sputum, urine, intravascular catheter, wound or surgical site, body fluids).
▪ Arterial blood gas (ABG) analysis – ABGs may reveal acidosis, hypoxemia, or hypercapnia.
▪ Imaging targeted at the suspected site of infection is warranted (eg, chest radiography, computed tomography of chest and/or abdomen).
Initial resuscitative therapy of distributive shock (septic)?
IV Fluids:
▪ Large volume infusions of IVF (30 mL/kg) are indicated as initial therapy for severe sepsis or septic shock, unless there is convincing evidence of significant pulmonary edema
▪ Crystalloid solutions (eg, normal saline, Ringer’s lactate)
IV antibiotics (empirical, start broad like piperacillin/tazobactam then narrow once susceptibilities are known) + IV hydrocortisone in patients with septic shock unresponsive to fluid resuscitation and vasopressors
What is multiple organ dysfunction syndrome ?
Multiple organ dysfunction syndrome (MODS) refers to progressive organ dysfunction in an acutely ill patient, such that homeostasis cannot be maintained without intervention. It is at the severe end of the severity of illness spectrum of both infectious (sepsis, septic shock) and noninfectious conditions (eg, SIRS from pancreatitis).
Definition of hypovolemic shock?
Definition: due to decrease in intravascular volume
Causes of hypovolemic shock?
- Hemorrhage (GI bleed, AAA rupture, trauma, postpartum hemorrhage, ectopic pregnancy),
- Non-blood fluid loss: burns, DKA, vomiting, diarrhea, interstitial fluid redistribution
Signs of hypovolemic shock?
Low CO, high SVR, high HR, CBC (low hematocrit – blood loss, high hematocrit – non-blood loss), low JVP, dry mucous membranes
Symptoms of hypovolemic shock?
Cool extremities due to peripheral vasoconstriction, cyanosis
What is the 3:1 Rule in the treatment of hypovolemic shock?
3:1 Rule: since only 30% of infused isotonic crystalloids remains in intravascular space, you must give 3x estimated blood loss
Management of hypovolemic shock?
- Clear the airway and breathing either first or simultaneously + apply direct pressure on external wounds while elevating extremities (do not remove impaled objects in the emergency room setting as they may tamponade bleeds)
- Start: TWO LARGE BORE (14-16G) IVs in the brachial/cephalic vein of each arm and run 1-2L bolus of IV Normal Saline/Ringer’s Lactate (warmed, if possible)
- If: continual bleeding or no response to crystalloids, consider pRBC transfusion, ideally crossmatched – if not available, consider O- for women of childbearing age and O+ for men – use FFP, platelets, or tranexamic acid in early bleeding
- Consider: common sites of internal bleeding (abdomen, chest, pelvis, long bones) where surgical intervention may be necessary
- Watch: hypothermia
Pre-operative investigations?
- CBC
- Sickle cell screen – genetically predisposed patient
- INR, aPTT
- Lytes, Cr
- Fasting glucose, HbA1c
- ECG - Heart disease, DM, other risk factors for cardiac disease; subarachnoid or intracranial hemorrhage, cerebrovascular accident, head trauma
- CXR
- C-spine X-ray in rheumatoid arthritis
- Investigations for further risk stratification: cardiac stress testing, sleep study
What is the “3-3-2 rule”
- 3 of patient’s own fingers can be placed between the incisors (incisor distance)
- 3 fingers along the floor of the mandible between the mentum and hyoid bone (hyoid-mental distance)
- 2 fingers in the superior laryngeal notch (thyroid-mouth distance)
- thyromental distance (distance of lower mandible in midline from the mentum to the thyroid notch); <3 finger breadths (<6 cm) is associated with difficult intubation
- mouth opening (<2 finger breadths is associated with difficult intubation)
- anterior jaw subluxation (<1 finger breadth is associated with difficult intubation)
Pre-operative Physical Exam
- Weight, height, BP, heart rate, respiratory rate, oxygen saturation
- Focused physical exam of the CNS, CVS, and respiratory systems
- General assessment of nutrition, hydration, and mental status
- Airway assessment:
- Cervical spine stability and neck movement – upper cervical spine extension, lower cervical spine flexion (“sniffing the morning air” position)
- Mallampati classification
- “3-3-2 rule”
- Tongue size
- Dentition, dental appliances/prosthetic caps, existing chipped/loose teeth – pose aspiration risk if dislodged and must inform patients of rare possibility of damage
What past medical conditions should be asked on pre-operative assessment
- Neuro: seizures, TIA/strokes, raised ICP, spinal disease, aneurysm, conditions affecting neuromuscular junction (e.g. myasthenia gravis)
- Resp: smoking, asthma, COPD, recent upper respiratory tract infection (URTI), sleep apnea
- CVS: angina/CAD, MI, CHF, HTN, valvular disease, dysrhythmias, peripheral vascular disease (PVD), conditions requiring endocarditis prophylaxis, exercise tolerance, CCS/NYHA class
- GI: GERD, liver disease
- Renal: acute vs. chronic renal insufficiency, dialysis, chronic kidney disease
- Endocrine: DM, thyroid disorders, adrenal disorders
- MSK: arthritides (e.g. rheumatoid arthritis, scleroderma), cervical spine pathology (e.g. cervical tumours, cervical infections/abscesses, trauma to cervical spine, previous cervical spine surgery), cervical spine instability (e.g. Trisomy 21)
- Other: morbid obesity, pregnancy, ethanol/recreational drug use
- Hematologic: anemia, coagulopathies, blood dyscrasias
Pre-operative Assessment: YAMPLLE
- Y – Why are you here/indication for surgery
- A – Anesthetic history: previous anesthetics, any complications, previous intubations, post-operative N/V
- FHx: abnormal anesthetic reactions, malignant hyperthermia, pseudocholinesterase deficiency
- Medications + allergies
- PMHx
- Last meal
- Labs and Investigations
- E – airway and cardio-resp exam
What is ASA 1?
A healthy, fit patient
What is ASA 2?
A patient with mild systemic disease
- e.g. controlled Type 2 DM, controlled essential HTN, obesity, smoker
What is ASA 3?
A patient with severe systemic disease that limits activity
- e.g. stable CAD, COPD, DM, obesity
What is ASA 4?
A patient with incapacitating disease that is a constant threat to life
- e.g. unstable CAD, renal failure, acute respiratory failure
What is ASA 5?
A moribund patient not expected to survive 24h without surgery
- e.g. ruptured abdominal aortic aneurysm (AAA), head trauma with increased ICP
What is ASA 6?
Declared brain dead, a patient whose organs are being removed for donation purposes for emergency operations, add the letter E after classification (e.g. ASA3E)
Pre-operative medications to stop
- Oral antihyperglycemics: do not take on morning of surgery
- ACEI and angiotensin receptor blockers: do not take on the day of surgery (controversial – they increase the risk of hypotension post-induction but have not been shown to increase mortality or adverse outcomes; therefore, some people hold and some do not)
- Warfarin (consider bridging with heparin), anti-platelet agents (e.g. clopidogrel), Xa inhibitor, direct thrombin inhibitors
- Herbal supplements: stop one week prior to elective surgery (ephedra, garlic, ginko, ginseng, kava, St. John’s Wort, Valerian, Echinacea)
Pre-operative medications to adjust
- Insulin (consider insulin/dextrose infusion or holding dose), prednisone, bronchodilators
