Clinical Pearls Flashcards
Postoperative Visual Loss
- POVL is rare
- prone spine surgery has highest risk
- 2 most common types: central retinal artery occlusion (CRAO) and ischemic optic neuropathy (ION)
- direct pressure on globe leads to CRAO
- inadequate oxygen delivery to optic nerve leads to ION
- optic nerve perfusion: MAP-IOP or CVP
- prone position: increased IOP and CVP
- MAP may decrease during prone procedures due to hypotension or decreased CO from abdominal pressure
- risk factors: hypotension, elevated venous pressure, anemia, blood loss, long procedure (>6h), and direct globe compression
Pulmonary Resection Risk Assessment
- respiratory mechanics: predicted postoperative (ppo) FEV1% (42 total lung segments)
* ppoFEV1<40% associated w/respiratory complications and need for mechanical ventilation - lung parenchymal function
* ppoDLCO <40% associated with increased risk of both cardiac and respiratory complications - cardiopulmonary interaction (exercise testing)
* VO2 max correlates well with risk of M&M (if poor tolerance, likely ICU post-op with mechanical ventilation and staged weaning)
Neuromonitoring
- key: maintain stable anesthetic
- IV anesthetics: decrease amplitude and increase latency of SSEPs and MEPs
- etomidate and ketamine increase amplitutes of SSEPs/MEPs
- volatiles/nitrous: decrease amplitude and increase latency of SSEPs and abolish MEPs
- muscle relaxants: little effect on SSEPs but prevent recording of MEPs
- **optimal anesthetic: TIVA (prop/remi) without muscle relaxants (okay with just SSEPs)
- **0.5 MAC volatile may be okay for SSEPs
- EMGs: stimulation of a motor nerve with subsequent measured muscle response (avoid all NMBDs)
- VEPs: extremely sensitive to IV and inhalation anesthetics (used to monitor optic nerve)
References
- Miller’s Anesthesiology
- Morgan & Mikhail’s Clinical Anesthesiology
- Stoelting’s Anesthesia and Co-Existing Disease
- Jaffe’s Anesthesiologist’s Manual of Surgical Procedures
ACC/AHA Guidelines on Management of Cardiac Patients for Noncardiac Surgery (2014 Update)
- Known or Risk Factors for CAD?
Emergency? Proceed - Non-emergency
ACS? Treat - No ACS
Estimate Perioperative Risk of MACE w/RCRI or NSQIP - Low risk (<1%)
Proceed - Elevated risk (>1%)
Functional capacity >4 METS? Proceed w/o testing - Functional capacity <4 METS or unknown?
*Will testing impact decision making OR preoperative care?
Yes–>pharmacologic stress testing then coronary revascularization if abnormal
No–>proceed to surgery
Revised Cardiac Risk Index (RCRI)
- IHD
- CHF
- CVA or TIA
- DM w/insulin
- CKD (Cr 2 mg/dL)
- Surgery type: intrathoracic, intraperitoneal, or suprainguinal vascular
*Risk of cardiac death, nonfatal MI, and nonfatal cardiac arrest
0=0.4%
1=0.9%
2=6.6%
Autonomic Neuropathy
S&S: loss of normal HR variability, orthostatic hypotension, resting tachycardia, early satiety, peripheral neuropathy, lack of sweating, dysrhythmias
*diabetics high risk
Anesthetic Concerns
- gastroparesis and aspiration risk
- hypotension (impaired peripheral vasoconstriction and baroreceptor function)
- silent ischemia
- intraoperative hypothermia (impaired peripheral vasoconstriction)
- impaired ventilatory response to hypoxia and hypercapnia
EKG Findings
- RVH: RAD, tall R wave in V1
- LAE/RAE: large P wave
- LVH: S wave depth in V1 + tallest R wave height in V5-V6 > 35 mm
- LBBB: QRS > 120 msec, notched R wave in lateral leads (“M” wave), often LAD
- RBBB: QRS > 120 msec, RSR’ in precordial leads (V1-V3), often normal axis (LV depolarization is normal)
Anaphylaxis v Anaphylactoid
Anaphylaxis
- type 1 immediate hypersensitivity reaction involving IgE antibody-antigen interaction
- usually requires previous exposure
Anaphylactoid
-direct, nonimmune-mediated release of vasoactive mediators from mast cells and basophils
*Clinically indistinguishable
Primary Therapy:
- epinephrine drug of choice
- fluids
Secondary Therapy:
- H1 blocker (50 mg diphenhydramine IV)
- steroid (100 mg IV hydrocortisone, fastest corticosteroid)
*Draw serum tryptase to establish conclusive dx of anaphylaxis/anaphylactoid reaction
Fat Embolism Syndrome
*fat emboli damage pulmonary capillaries causing respiratory failure
- Major criteria: respiratory failure, CNS, petechial rash
- Minor criteria: tachycardia, fever, jaundice, AKI, anemia, thrombocytopenia, retinal fat globules
Electrolyte Abnormalities and EKG Changes
- hyperkalemia: peaked T waves, increased PR interval, wide QRS
- hypokalemia: flat/inverted T waves, prominent U waves
-hypocalcemia: prolonged QT, wide QRS
Hypothermia
Causes
- decreased heat production (decreased metabolic rate)
- increased heat losses (peripheral vasodilation, cold room, fluids)
- impaired heat regulation (GA, hypothalamus dz)
Consequences
- CNS: prolonged awakening
- CV: arrhythmias
- Heme: impaired coagulation
- Metabolic: prolonged drug effects, particularly NMBs
- Mild hypothermia (33-37 C): coagulopathy 2/2 defects in platelet aggregation and adhesion (normal factor function)
- Extreme hypothermia (<33 C): both plt and factor function impaired)
- So: TEG more helpful in mild hypothermia (plt function not measured by PTT) and either test helpful at extreme hypothermia (coag function measure by both tests)
Alveolar Gas Equation
PAO2 = FiO2× (Pb − PH2O) − (PACO2/R)
Normal shunt
- 3% of CO normal
* bronchial and thebesian veins (cardiac veins, drain myocardium into left heart)
Difficult Mask
- Obesity
- OSA
- Beard
- Edentulous
- Age >55 yrs
Difficult Intubation
- MP 3 or 4
- Small mouth opening <2 cm
- TM distance <6 cm
- Thick neck
*MP score has best sensitivity (although still not great at 75%) and high specificity (high 90%)
Extubation Criteria
OR
- Adequate oxygenation (Sp02 >92%, PaO2 >60 mmHg)
- Adequate ventilation (EtCO2 < 50 mm Hg)
- HD stable
- Full reversal of muscle relaxation (TOF >0.9)
- Neuro intact
ICU
- Adequate mentation
- HD stable
- Adequate oxygenation and ventilation on minimal vent settings (ie. PS 5 mmHg, FiO2 <40%, PEEP 5)
- Vent Criteria (during SBT)
- RSBI <105 (f/Vt)
- NIF < 20 cm H20 (effort independent, strong - predictor, poor + predictor)
- VT >5 ml/kg
- VC >10 ml/kg
- RR < 30
*RSBI most consistent and powerful predictor
**PSV was more effective than a T-piece (30 min) for successful spontaneous breathing trials (SBTs) among patients with simple weaning.
PT v PTT
Prothrombin Time (PT)
- extrinsic coag pathway
- measures warfarin, liver damage, and vit K status
- Factors: I, II, V, VII, X
- I (fibrinogen) and II (prothrombin)
Partial Thromboplastin Time (PTT)
- intrinsic and common coag pathways
- monitors heparin
- Factors: I, II, V, VIII, IX, X, XI and XII
- NOT measured: factors VII and XIII
- **Both heparin and warfarin affect both PT and PTT
- **Heparin-ATIII part of extrinsic and common pathway
- **Warfarin-Vit K factors part of both pathways
Vitamin K Dependent Clotting Factors
II, VII, IX and X
*and proteins C and S (anti-coag factors)
Factor VIII
Only clotting factor NOT produced in the liver
Calcium Disorders
Hypercalcemia
- bones, stones, groans (N/V), psychic overtones (lethargy, coma)
- HTN and arrhythmias possible
- DDX: hyperPTH, vit d toxicity, malignancy, meds (thiazides)
- Tx: IVFs, lasix, dialysis for life-threatening hypercalcemia
Hypocalcemia
- tetany and muscle cramping (Chvostek), respiratory weakness, CHF, arrhythmias
- hypoPTH, vit d deficiency, citrate chelation
Hypoglycemia
S&S
- SNS activation (diaphoresis, tachycardia, anxiety)
- Neuro: weakness, fatigue, AMS, coma
Ddx
-exogenous insulin, insulin tumors, critical illness/sepsis, adrenal insufficiency, liver disease
Pheochromocytoma
Pre-op:
- Phenoxybenzamine: noncompetitive, nonselective, alpha blocker
- tachycardia from alpha 2 blockade
- Selective, competitive, alpha 1 blockers
- prazosin, doxazosin
- less tachycardia and shorter elimination times may be advantageous in avoiding postoperative hypotension
Pre-op treatment until blood pressure improves (typically 10-14 days)
- orthostatic hypotension and nasal congestion common side effects
- hold 24 hours prior to surgery to prevent postoperative hypotension
*Beta blockade (typically B1 selective like metoprolol/esmolol) only needed for patients with predominantly epinephrine secreting tumors or patients who develop tachycardia from alpha antagonism tx
ARDS v TRALI
ARDS and TRALI
-clinically indistinguishable noncardiogenic pulmonary edema (increased pulmonary endothelial permeability/leakage)
-frothy pulmonary secretions, fever, tachycardia, dyspnea hypoxia, hypotension
Dx: acute onset hypoxemia (PaO2/FiO2 <300, SpO2 <90%), bilateral chest infiltrates on CXR, absence of cardiac failure or fluid overload (PAOP <18)
Tx: supportive (diuretics and steroids not beneficial)
*mortality rate significantly lower with TRALI (6%, compared to 40% for ARDS) and requires h/o transfusion w/in 6 hours
TACO v TRALI
TRALI
- donor antibodies leads to activation of neutrophils on the pulmonary vascular endothelium–>release of activating factors leads to endothelial damage, capillary leakage, and acute lung injury (usually with plasma-rich blood products)
- tx: supportive (O2 and low TVs), stop blood products and notify blood bank
TACO
- cardiogenic (hydrostatic) pulmonary edema from volume overload during transfusion
- tx: diuretic, inotrope and/or afterload reducer if needed
Differentiation:
- Signs and Symptoms
- TRALI: low BP, fever, leukopenia
- TACO: HTN, JVD, peripheral edema, S3 heart sound - Fluid Status
- TRALI: normovolemia or hypovolemia
- TACO: hypervolemia - Cardiac Function
- TRALI: normal
- TACO: impaired - BNP (peptide secreted by ventricles in overload)
- TRALI: nl
- TACO: elevated - Edema fluid to serum protein ratio
- TRALI: high in plasma proteins
- TACO: low in plasma protein
Beta Blocker Initiation
- never start day of surgery
- if 3 or more risk factors (RCRI), then it may be reasonable to start, but must start 2-7 days pre op (2014 ACC/AHA)
Respiratory Sinus Arrhythmia
*Heart Rate Changes With Respiration
Bainbridge Reflex: increased heart rate during inspiration (from increased cardiac filling)
Baroreceptor Reflex: increase in BP (increased SV/CO during inspiration) leads to a decrease in HR
*Balance of these two reflexes leads to HR changes
***Bezold-Jarisch: bradycardia and hypotension in response to underfilled LV (Vagus nerve)
Bezold–Jarisch reflex
Bradycardia and hypotension in response to under-filled LV (via Vagus nerve)
*opposes baroreceptor reflex
cm H20 to mmHg
10 cm H20 = 7.5 mmHg
Corneal Abrasion
- red and watery
- foreign body sensation
- photophobia
- worse with blinking
- tx: antibiotic ointment
Benzodiazepine
- midazolam: short acting
- lorazepam: intermediate acting
- diazepam: long acting
*lorazepam may be best for EtOH withdrawal in liver disease due to its intermediate half-life
SIMV v AC
AC
- each breath (initiated by the patient) is assisted or controlled by preset volume or pressure
- backup rate for preset volume/pressure breath if none is initiated by patient
- every breath is the same
- pros: if patient weak, continue to receive full volume/pressure breaths
- cons: risk of hyperventilation/hyperinflation (resp alkalosis)
SIMV
- guarantees certain number of breaths (preset backup rate of certain volume/pressure)
- mandatory breaths synchronized to coincide with spontaneous respirations
- patient triggered breaths may be smaller
- if the patient is taking good volumes during their spontaneous breaths, this may indicate that weaning might be possible
- pressure support can be added to patient breaths if too small
- pros: reduced risk of hyperventilation/hyperinflation
- cons: increased work of breathing, reduction in CO (in patients w/reduced LV function)
- Personal preference prevails, except in the following scenarios
1. Patients who breathe rapidly on ACV should switch to SIMV
2. Patients who have respiratory muscle weakness and/or left-ventricular dysfunction should be switched to ACV
Neurogenic Pulmonary Edema
- can occur after any CNS injury
- mechanism poorly understood
- both cardiogenic and noncardiogenic components
- massive sympathetic surge–>widespread vasoconstriction–>increased pulmonary blood flow
- subsequent pulmonary leak
- treatment largely supportive: treat CNS injury, lung protective ventilation, consider diuretics to reduce pulmonary hydrostatic pressure
SIADH v CSWS
SIADH
- euvolemic
- urine sodium < 100 mEq/L
- tx: fluid restriction and diuretics
CSWS
- hypovolemia
- urine sodium >100 mEq/L
- tx: fluid and sodium replacement
Absent Left Sided Breath Sounds
Right mainstem ETT v Pneumothorax
*EtCO2 decreased in pneumothorax, usually normal in endobronchial intubation
Other features of pneumothorax: decreased CO, hypotension, hyper-ressonance to percussion, contralateral tracheal shift, distended neck veins
Pneumothorax tx
- needle decompression 2nd intercostal space, midclavicular line
- chest tube 5th intercostal space just anterior to midaxillary line
Epidurals for post-op pain control
- improved pain scores
- greater mobility
- decreased post-op pulmonary complications (less opioid induced respiratory depression, less splinting leading to hypoventilation and pneumonia)
SAB and TURP
- T10 goal sensory level
- provides comfort and covers bladder but also allows for early detection of bladder perforation (abdominal pain and diaphragmatic irritation/shoulder pain)
Pseudocholinesterase Deficiency
Dibucaine # (normally inhibits normal pseudocholinesterase)
- 80%: normal (80% inhibition of enzyme by dibucaine)
- 50%: heterozygote
- 20%: homozygote
- Sux lasts 4-8 hours
- Phase 2 blockade: fade on TOF (like nondepolarizers)
Myocardial Oxygen Supply/Demand
Decreased supply: anemia, hypoxia, tachycardia, decreased CPP (hypotension, vasospasm, plaque, AS, AR, elevated LVEDP)
*Demand = HR, contractility, and wall tension (and basal O2 demand)
Increased demand: tachycardia, increased wall tension, contractility, and afterload
*myocardium is dependent on increasing coronary blood flow during times of demand, because oxygen extraction can only be minimally increased
Digoxin Toxicity
- EKG changes, arrhythmias, fatigue, N/V, confusion, visual disturbances
- exacerbated by hypokalemia, hypomagnesemia, and hypercalcemia
*can cause ST depression even in therapeutic range
Mixed SvO2
Normal 75% (range 60-80%)
Morbid Obese Risks
- airway mgmt
- pulmonary abnormalities (atelectasis, hypoxia, decreased FRC, increased CC, rapid desaturation w/apnea)
- obesity hypoventilation syndrome (Pickwickian syndrome)
- OSA
- metabolic syndrome
- DMII
- HTN
- CAD
- CVA
- DVT/PE
- Fatty liver disease
Tumescent Liposuction Lidocaine Max
55 mg/kg
*lidocaine 4 mg/kg or 7 mg/kg w/epi
Celiac Plexus Block
Procedure:
- prone patient, just anterior to L1 vertebral body
- test block first w/local, then neurolytic block (alcohol or phenol)
Complications:
- paralysis (neurolytic injection into spinal/epidural space or damage to arterial supply ie. artery of Adamkiewicz)
- postural hypotension, intravascular injection, hemorrhage, sexual dysfunction, diarrhea
- postural hypotension most common
Induction for a kid with acute epiglottitis and family history of MH?
IM ketamine–>IV–>airway
10 mg/kg
*maintain spontaneous respiration
Transplanted Heart
- dependent on circulating catecholamines and preload
- response to circulating catecholamines is normal and possibly enhanced due to denervation sensitivity (increased receptor density)
- absence of vagal influences causes a relatively high resting HR (90-120)
- responsive to direct acting agents: isoproterenol, epinephrine, dobutamine, dopamine