Acute Coronary Syndrome
Definition
Acute coronary syndrome (ACS) is an acute imbalance between myocardial O 2 supply and demand that leads to ischemia and infarction. ACS is classified as being unstable angina, non–ST segment elevation myocardial infarction (NSTEMI), or STEMI.
Etiology
Total or subtotal coronary artery occlusion
Primary ACS results from coronary artery occlusion
Plaque disruption with thrombus formation
Coronary vasospasm from endothelial dysfunction or drug ingestion (e.g., cocaine, serotonin receptor agonists)
Coronary artery embolism
Coronary artery dissection
Aortic dissection
Secondary ACS results from
Increased myocardial O 2 demand
Decreased myocardial O 2 supply
Typical Situations
Patients with known CAD or risk factors for atherosclerosis (males, hypertension, hyperlipidemia, diabetes, peripheral vascular disease, smoking, family history of CAD)
Increased myocardial O 2 demand
Tachycardia, fever, severe hypertension, or thyrotoxicosis
Decreased myocardial O 2 supply
Systemic hypotension, hypoxemia, or anemia
Miscellaneous factors (e.g., polyarteritis nodosa, Kawasaki disease)
Prevention
Evaluate myocardial function and reserve and optimize medical therapy prior to surgery
Modify cardiac risk factors if possible
Optimize β-blocker and statin therapy
Manage antiplatelet therapy (e.g., aspirin, clopidogrel) in collaboration with surgical team
Patients with coronary stents on antiplatelet therapy require comanagement with cardiologist and surgeon
Patients may require “bridging therapy” (e.g., eptifibatide and heparin) to reduce risk of perioperative stent thrombosis
Avoid elective anesthesia and surgery in patients with unstable angina or with a history of MI in the previous 6 months
Optimize hemodynamics and hematocrit during anesthesia
Maintain myocardial O 2 supply
Prevent increases in myocardial O 2 demand
Revascularization (CABG or PCI) prior to elective surgery is not usually recommended
Consult cardiology and cardiac surgery
Manifestations
In awake patients
Chest pain, pressure, or discomfort radiating to arm and jaw
Women, diabetics, and the elderly may exhibit atypical chest pain (e.g., epigastric pain, sharp pain, fatigue, or dyspnea) or no symptoms at all
Nausea, diaphoresis, palpitations, syncope
Cardiac arrest
Electrocardiogram
ST segment elevation or depression
Conduction abnormalities (e.g., left bundle branch block or complete atrioventricular block)
Peaked T-waves
Progression to inverted T-waves and development of Q-waves
Arrhythmias including PVCs, VT, or VF
Cardiac biomarkers
Increase in troponin I, troponin T, and CK-MB isoenzyme
Diagnosis of MI requires presence of ECG changes or symptoms, because other conditions may be responsible for elevated cardiac biomarkers
Hemodynamic abnormalities
Hypotension
Tachycardia
Bradycardia
New regional wall motion abnormality on TEE or TTE
Elevation of filling pressures (CVP, PCWP)
Criteria required for diagnosis of MI
Symptoms of ischemia
ECG changes
ST segment changes
Q-waves
New left bundle branch block
Evidence of new regional wall motion abnormality
Detection of rise and/or fall of cardiac biomarkers including
Troponin I
Troponin T
CK-MB
Similar Events
PE (see Event 21, Pulmonary Embolism )
Esophageal spasm, costochondritis, acute abdomen
Primary pulmonary pathology (e.g., pneumonia, pulmonary infarction)
Acute aortic dissection
Nonischemic ST segment or T-wave changes (see Event 12, ST Segment Change )
ECG artifact
Improper electrode placement
Changes in patient position or surgical manipulation may alter position of heart relative to the electrodes
Management
Inform the surgeon
Confirm diagnosis by evaluating available leads on ECG monitor
Ensure adequate oxygenation and ventilation
Optimize hemodynamics—improve myocardial O 2 supply while decreasing demand
Treat hypotension with vasopressors and IV fluids to increase DBP
Phenylephrine IV bolus, 50 to 200 μg
Phenylephrine IV infusion, 10 to 100 μg/min
Optimize circulating blood volume
Treat tachycardia
Assure adequate depth of anesthesia
Administer β-blockers in the absence of evidence of heart failure
Esmolol IV, 10 to 30 mg
Esmolol IV infusion, 25 to 200 μg/kg/min
Metoprolol IV, 1 to 5 mg
Calcium channel blockers
Diltiazem IV, 0.15 to 0.25 mg/kg load, then 5 to 15 mg/hr
Improve collateral myocardial blood flow and decrease myocardial wall stress
Administer nitroglycerin IV, 0.2 to 2 μg/kg/min
Do not administer when patients are hypotensive or have recently taken phosphodiesterase inhibitors
Draw labs
ABG, HCT, electrolytes, cardiac biomarkers
Consider additional monitoring
Arterial line, CVP line, TEE
Administer aspirin (PO, NGT, or PR) 325 mg
Treat arrhythmias according to ACLS protocol (see Event 19, Nonlethal Ventricular Arrhythmias )
In case of STEMI
Obtain stat interventional cardiology consult and alert cardiac catheterization laboratory of your concerns for management
Terminate surgery as soon as possible and prepare patient for transport to cardiac catheterization lab
Evaluate and treat cardiogenic shock
Consider treating with vasopressors and/or ionotropes to improve end-organ perfusion
Dopamine IV infusion, 2 to 10 μg/kg/min
Norepinephrine IV infusion, 10 to 100 ng/kg/min
Consider mechanical support with IABP or percutaneous left ventricular assist device (LVAD) for patients not responding to pharmacologic support
Consider antiplatelet therapy and anticoagulant therapy
Weigh risk of bleeding from recent surgery against benefit of improved mortality from ACS; requires joint discussion with cardiologist and surgeon
Request ICU bed for postoperative care
Complications
Heart failure
Arrhythmias
Cardiac arrest
Thromboembolic complications
Papillary muscle dysfunction or rupture
Rupture of the interventricular septum or the ventricular wall
Suggested Reading
Anaphylactic and Anaphylactoid Reactions
Definition
Anaphylactic and anaphylactoid reactions are serious allergic reactions that are rapid in onset and may cause death.
Anaphylactic reaction (immunologic) involves antigen and IgE antibodies; requires previous sensitization to the antigen
Anaphylactoid reaction (nonimmunologic) mediated primarily by histamine; may occur with the first exposure to a triggering agent
Complement activation may follow both immunologic and nonimmunologic reactions
Etiology
Administration or exposure to an agent that the patient has been sensitized to by prior exposure, with production of antigen-specific IgE (anaphylactic reaction)
Allergic reaction to agent requiring no previous exposure (anaphylactoid reaction)
Typical Situations
The true incidence is unknown, but is estimated at 1 in 10,000 to 1 in 20,000 anesthetic procedures. Approximately 1500 deaths occur each year in the United States from anaphylaxis in all settings.
In patients with a known allergy or sensitivity to a specific agent or with conditions making a reaction to an agent more likely
Allergic reactions to protamine are more likely in patients with fish allergy, prior protamine administration, or after treatment with protamine-zinc insulin
Patients with a history of allergy to nondrug allergens have a higher risk of anaphylaxis during anesthesia
After exposure to substances that can trigger anaphylactic or anaphylactoid reactions
Neuromuscular blocking drugs (60% of anesthesia-related anaphylaxis)
Latex (20% of anesthesia-related anaphylaxis)
Antibiotics (15% of anesthesia-related anaphylaxis, with penicillins and cephalosporins responsible for 70% of antibiotic induced anaphylaxis)
Opioids
Amino-ester local anesthetic agents
Blood and blood products
Iodinated contrast material
Chlorhexidine preparation solutions
Individuals with frequent latex exposure
Health care workers
Patients who have undergone multiple surgical procedures
Patients who require intermittent bladder catheterization
SCI patients
Chronic care patients
Prevention
Avoid agents to which the patient has a documented allergy
Minimize the use of latex products in health care (in the United States many institutions have replaced most products with latex-free versions)
If there is a history of latex allergy, establish a latex-free environment
Avoid contact with or manipulation of latex devices
Use nonlatex surgical gloves
Use syringe/stopcock or unidirectional valves for injecting medications
Do not insert a needle through any multiple-dose vial with a natural rubber stopper
Take the top of the vial completely off
Use medication from a glass ampule, if available
Use glass syringes with glass plunger or plastic syringes with known non-latex plungers. (Check manufacturer for materials used.)
Obtain a careful history of previous allergic reactions, atopy, asthma, or significant latex exposure
Avoid transfusion of blood or blood products whenever possible
Check the identity of the patient and blood products carefully prior to transfusion
If a specific drug must be administered to a patient known to be at risk of an allergic reaction, administer prophylaxis
Corticosteroids
Dexamethasone IV, 20 mg, or methylprednisolone IV, 100 mg
H 1 antagonist
Diphenhydramine IV, 25 to 50 mg
Administer a test dose of drug
Obtain a consultation from an allergist if a critical allergy must be defined
Manifestations
Anaphylaxis has the potential for acute onset with catastrophic consequences. Severe hypotension, increased PIP, and hypoxemia are the most common initial signs but need not be present simultaneously.
Cardiovascular
The awake patient may complain of dizziness or lose consciousness
Severe hypotension
Bradycardia—may be initial sign
Arrhythmias
Cardiac arrest
Respiratory
The awake patient may complain of dyspnea or chest tightness
Hypoxemia
Decreased lung compliance
Severe bronchospasm
Cutaneous—may be obscured by surgical drapes
Flushing, hives, urticaria, pruritus
Swelling of mucosal membranes, conjunctiva, lips, tongue, and uvula
Similar Events
Anesthetic overdose (see Event 72, Volatile Anesthetic Overdose )
Pulmonary edema (see Event 20, Pulmonary Edema )
Hypotension from other causes (see Event 9, Hypotension )
ACS (see Event 15, Acute Coronary Syndrome )
Cardiac tamponade (see Event 18, Cardiac Tamponade )
Venous air embolism (see Event 24, Venous Air or Gas Embolism )
Vasovagal reaction
Septic shock (see Event 13, The Septic Patient )
Drug administration error (see Event 63, Drug Administration Error )
Stridor (see Event 36, Postoperative Stridor )
PE (see Event 21, Pulmonary Embolism )
Aspiration of gastric contents (see Event 28, Aspiration of Gastric Contents )
Pneumothorax (see Event 35, Pneumothorax )
Bronchospasm (see Event 29, Bronchospasm )
Skin manifestations of drug reactions not associated with anaphylaxis
Transfusion reaction (see Event 50, Transfusion Reaction )
Fat embolism syndrome
Amniotic fluid embolism (see Event 81, Amniotic Fluid Embolism )
Management
Stop administration of any possible antigen
Retain blood products for analysis
Remove all latex-containing products from contact with the patient
Inform the surgeons and call for help
Check to see whether they have injected or instilled a substance into a body cavity
Consider aborting the surgical procedure if severe
Anaphylaxis may be biphasic and can recur after successful initial treatment
Ensure adequate oxygenation and ventilation
Administer 100% O 2
Intubate the trachea if not already intubated
The airway can rapidly become very edematous making intubation (or extubation) more difficult or impossible
Treat hypotension
Epinephrine is the drug of choice for treatment of anaphylaxis
For mild to moderate hypotension, administer epinephrine IV, 10 to 50 μg increments, and repeat as necessary with escalating doses
For cardiovascular collapse or cardiac arrest, administer epinephrine IV, 500 to 1000 μg boluses, and repeat as necessary (see Event 2, Cardiac Arrest )
Administer vasopressin IV, 10 to 40 U, in cases of anaphylactic shock resistant to catecholamines; in pulseless arrest, follow the ACLS pulseless arrest algorithm
Norepinephrine infusion may be required
Glucagon IV, 1 to 5 mg, may be useful in patients receiving β-blocker therapy who do not respond to epinephrine
Methylene blue IV, 10 to 50 mg, has been successfully used in catecholamine- and vasopressin-resistant anaphylaxis
Rapidly expand the circulating fluid volume
Place patient in Trendelenburg position
Immediate fluid needs may be massive (several liters of crystalloid)
Ensure adequate IV access
Decrease or stop administration of anesthetic agents if hypotension is severe
If bronchospasm is present
Administer bronchodilator
Albuterol metered dose inhaler (MDI), 5 to 10 puffs
Volatile anesthetics may be administered for bronchodilation if the patient is normotensive
Administer an H 1 and H 2 histamine antagonist
Diphenhydramine IV, 50 mg
Ranitidine IV, 50 mg
Administer corticosteroids
This is not helpful for the acute event, but may reduce risk of further episodes
Dexamethasone IV, 20 mg bolus, or methylprednisolone IV, 100 mg bolus
In the absence of any other cause, consider latex allergy
Ensure all latex products in contact with the patient have been removed from the surgical field (double check whether these products do or do not contain latex)
Surgical gloves
Urinary catheter
Medications drawn up through a latex stopper
Place invasive monitors to help guide fluid and vasopressor management
Arterial line
CVP or PA catheter
TTE or TEE
Urinary catheter
Obtain blood sample for measurement of mast cell tryptase within 2 hours of onset to confirm diagnosis of anaphylactic reaction
Arrange admission to an ICU for postoperative management and observation
Consider referring patient to an allergist on discharge from the hospital
Complications
Inability to intubate, ventilate, or oxygenate
Hypertension, tachycardia from vasopressors
ARDS
Renal failure
Cardiac arrest
Anoxic brain injury
Death
Suggested Reading
Autonomic Dysreflexia
Definition
Autonomic dysreflexia (AD) is a massive, unopposed, reflex sympathetic discharge triggered by a noxious stimulus below the level of a chronic SCI.
Etiology
Bladder or urinary tract distention (e.g., instrumentation, infection, or calculi of the urinary tract)
Lower GI tract stimulation (e.g., bowel distention from any cause)
Performance of a surgical procedure below the level of an SCI with inadequate anesthesia/analgesia
Skin stimulation (e.g., pressure sore, ingrown toenail, tight-fitting clothing)
Exposure to temperature extremes
Medications (e.g., nasal decongestants, sympathomimetic drugs, misoprostol)
Typical Situations
In patients with SCI, usually at least 6 weeks after the injury
In patients whose level of SCI is at or above T6 (the higher and more complete the lesion, the higher the incidence)
During performance of urologic procedures such as bladder catheterization, cystoscopy, or cystometrography
In patients with disorders of the lower GI tract (e.g., fecal impaction, hemorrhoids, anal fissure)
During procedures involving the rectum or colon
During recovery from neuraxial, regional, or general anesthesia
During labor and delivery
Prevention
Obtain a thorough history from patients with SCI. They are often aware of some of the stimuli that will evoke this response
Avoid stimuli known to trigger AD if possible
Check the baseline BP for comparison with perioperative values
Consider preoperative prophylaxis of patients at risk of AD
Clonidine 0.2 to 0.4 mg PO, preoperatively
Nifedipine 10 mg SL, immediately preoperatively
Phenoxybenzamine 10 mg PO, 3 times daily to maximum of 60 mg/day
Prazosin 6 to 15 mg PO
Provide adequate regional or general anesthesia and postoperative analgesia for a surgical procedure
Manifestations
Acute, paroxysmal onset of severe systolic and diastolic hypertension
Normal BP in most SCI patients is low, so reference the change in BP to the patient’s resting value
Increased blood loss from surgical site
Reflex bradycardia (tachycardia and arrhythmias may also occur)
Additional signs of sympathetic hyperreactivity
Below the level of SCI: cool, pale skin; pilomotor erection; spastic muscle contraction and increased muscle tone; penile erection
Above level of SCI: sweating, vasodilation and flushing of the skin, mydriasis, nasal and conjunctival congestion, eyelid retraction
If the patient is awake
Severe pounding headache, blurred vision, nasal congestion, dyspnea, nausea, or anxiety
Similar Events
Light anesthesia
Vasopressor overdose
Preeclampsia/eclampsia in pregnant SCI patient (see Event 88, Preeclampsia and Eclampsia )
Intraoperative hypertension from other causes (see Event 8, Hypertension )
Pheochromocytoma
Migraine and cluster headaches
Management
Verify the BP; check for additional signs and symptoms of sympathetic hyperreactivity
Inform the surgeon and ask for the surgical stimulus to be stopped (e.g., drain bladder)
Place patient in reverse Trendelenburg position to facilitate venous pooling in lower extremities
If the patient is under general anesthesia
Increase the depth of anesthesia
Increase the inspired concentration of volatile anesthetic
Administer additional opioid (e.g, fentanyl IV, 25 to 50 μg)
If hypertension persists, administer drugs with rapid onset and short duration
Phentolamine 2 to 10 mg IV, titrated to effect
Sodium nitroprusside IV infusion, 0.2 to 1.0 μg/kg/min, titrated to effect with arterial line monitoring
AD may occur during emergence and recovery
If the patient is awake
For less severe hypertension:
NTG 0.4 mg/spray into oral cavity
Nitropaste 2%, 1 inch applied to the skin above the level of the SCI
Captopril 25 mg SL
Nifedipine 10 mg capsule, bitten and swallowed
For severe elevation in BP:
Phentolamine 2 to 10 mg IV, titrated to effect
Sodium nitroprusside IV infusion, 0.2 to 2.0 μg/kg/min, titrated to effect with arterial line monitoring
If AD resolves, continue with surgery (AD may recur)
If AD does not resolve with treatment
Abort surgery if possible
Place an additional peripheral IV or a CVP line to administer potent vasodilators
Insert an arterial line if not already done
Complications
Myocardial ischemia or infarction
Pulmonary edema
Hypertensive encephalopathy or stroke
Atrial and ventricular arrhythmias, heart block
Seizures, coma, intracerebral or subarachnoid hemorrhage
Increased surgical blood loss
Hypotension secondary to therapy with vasodilators
Cardiac arrest
Suggested Reading
Cardiac Tamponade
Definition
Cardiac tamponade is the accumulation of blood, a blood clot, or fluid in the pericardial space, limiting ventricular filling and resulting in hemodynamic compromise.
Etiology
Bleeding after cardiac surgery
Coagulopathy
Cardiac perforation
Rheumatologic or autoimmune diseases
Pericardial malignancy or tumor metastasis
Pericardial infection, typically as a complication of sepsis
Chronic renal failure
Radiation-induced pericardial effusion
Typical Situations
Idiopathic
Iatrogenic
Post cardiac surgery
Clots may cause tamponade even in the presence of an open pericardium and patent mediastinal drains
Erosion of CVP catheter, especially through right atrial wall
Invasive cardiac procedure
PCI
Electrophysiologic procedure
Percutaneous valve repair/replacement
Trauma, including gun shot wounds (may be insidious in onset)
Malignancy
End-stage renal disease
Collagen vascular disease (e.g., systemic lupus erythematosus, scleroderma)
Post MI (myocardial rupture, consequences of anticoagulant or thrombolytic therapy)
Bacterial infection (e.g., tuberculosis)
Aortic dissection
Radiation therapy to the mediastinum
Prevention
Achieve and maintain hemostasis during and after cardiothoracic surgery
Treat coagulopathy
Place central lines and pacemaker leads carefully
CVP catheter tip should be at the junction of the superior vena cava (SVC) and right atrium
Obtain a CXR following placement to confirm the position of the CVP catheter tip when feasible
Treat and control underlying medical problems that predispose the patient to pericardial effusion
Perform pericardiocentesis of large pericardial effusion prior to surgery
Manifestations
Beck triad (distant heart sounds, jugular venous distension, hypotension)
Tachycardia, decreased CO
Narrow pulse pressure, exaggeration of pulsus paradoxus
Normal limit of pulsus paradoxus is a decrease in SBP on inspiration of less than 10 mm Hg
Equalization of cardiac diastolic filling pressures at a relatively high value (right atrial pressure, PA diastolic pressure, PA wedge pressure)
Dyspnea, orthopnea
Following cardiac surgery
Consider tamponade in the differential diagnosis of any patient with low CO
Increased drainage followed by decreased drainage from the mediastinal chest tube
Pericardial fluid visible on TEE or TTE in conjunction with
Atrial and/or ventricular collapse
Abnormal ventricular septal motion with respiration
IVC plethora (i.e., lack of the normal inspiratory collapse of the IVC on TTE)
Low-amplitude ECG with ST changes and/or electrical alternans
Increased size and bottle shape of the cardiac silhouette on CXR
Similar Events
Congestive heart failure
Constrictive pericarditis
Exacerbation of asthma or COPD (see Event 29, Bronchospasm )
Hypovolemia
ACS (see Event 15, Acute Coronary Syndrome )
Acute aortic dissection
PE (see Event 21, Pulmonary Embolism )
Acute RV infarction
Tension pneumothorax (see Event 35, Pneumothorax )
Restrictive cardiomyopathy
Auto-PEEP
Management
The pericardium has low compliance, and the rate of fluid accumulation will determine the rapidity of onset of symptoms. Rapid accumulation of 150 to 200 mL of blood or fluid can critically compromise myocardial function.
Ensure adequate oxygenation and ventilation
Administer supplemental O 2 by nonrebreathing face mask
Expand and maintain the circulating fluid volume
Ensure adequate IV access
Place additional large-bore IV catheters as needed
Rapidly administer 250 to 500 mL crystalloid
Place invasive monitoring lines as indicated
Arterial line
CVP catheter for monitoring and drug administration
PA catheter for monitoring of cardiac filling pressures and CO
Support the circulation
Phenylephrine IV, 100 to 200 µg; may repeat and increase dose as needed
Epinephrine IV, 5 to 10 µg; may repeat and increase dose as needed
Vasopressin IV, 1 to 2 U; may repeat and increase dose as needed
Norepinephrine IV, 8 to 16 µg; may repeat and increase dose as needed
Commence infusions of vasopressors as needed
Confirm diagnosis with TEE or TTE
Consider CXR if patient is stable
Apply and connect external defibrillator pads
If the patient has had recent cardiothoracic surgery
Call for cardiac surgeon stat
Open the chest immediately to relieve the cardiac tamponade
Prepare the OR for possible mediastinal exploration
Notify nursing staff and perfusionist
If the patient has NOT had recent cardiothoracic surgery
Perform subxiphoid pericardiocentesis
This may remove enough fluid to temporarily improve the patient’s condition prior to emergency surgery
A negative aspiration does not exclude cardiac tamponade
If cardiac tamponade is suspected and the patient is stable
Review the patient’s history
Check coagulation status of the patient
PT and PTT
Platelet count
Platelet function
ACT
Thromboelastogram (TEG)
Monitor the patient using invasive techniques
Obtain CXR and TEE or TTE for diagnosis
Obtain consultation from a cardiologist and/or cardiothoracic surgeon for definitive treatment
Anesthetic management of the patient with cardiac tamponade
Hemodynamic goals are best described as keeping the patient fast (tachycardia), full (hypervolemia), and tight (increased SVR)
Maintain HR in the range of 90 to 140 bpm
Optimize filling pressures to compensate for the vasodilation that occurs with induction of anesthesia
Administer fluid bolus (250 to 500 mL crystalloid)
Consider femoral venous and arterial cannulation for emergent CPB if difficult surgical exposure is anticipated
Maintain spontaneous ventilation as long as possible, as it augments venous return and maintains CO
With positive pressure ventilation, use low airway pressure without PEEP to minimize decrease in venous return
Consider prepping and draping patient prior to induction of general anesthesia
For anesthesia, use drugs that do not decrease sympathetic output
Ketamine IV, 0.25 to 1 mg/kg
Should still anticipate hemodynamic compromise
Use succinylcholine IV, 1 to 2 mg/kg for intubation
Provide additional IV anesthesia as tolerated
Ketamine 10 to 20 mg
Fentanyl 25 to 50 μg
Midazolam 0.25 to 0.5 mg
Correct metabolic acidosis
Anticipate a rebound hypertensive response or return of normal hemodynamics after tamponade is relieved
Use additional anesthetic agents (e.g., volatile anesthetics)
Complications
Arrhythmias
Myocardial ischemia or infarction
Complications of pericardiocentesis
Pneumothorax, hemothorax
Laceration of heart or lungs
Infection
Cardiac arrest
Suggested Reading
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