Physiology
Pain fibers (A, delta, C fibers): usually blocked first, followed by tempà touchà proprioceptionà motor function
Types of local

• Ester or amide linkage
• Esters: Cocaine, procaine, tetracaine (only have one I)
• Hydrolyzed by pseudocholinesterase into PABAè can cause allergy àmay require IM/IV epi
• Not dependent on hepatic or renal function
• Amide: lidocaine, bupivacaine (two I’s)
• Metabolized by hepatic microsomal enzymes and metabolites excreted by kidney

Local anesthetic 
Doses

• epinephrine prolongs the duration of action of anesthetic 
• Bupivicaine 2.5 mg/kg: has a longer duration due to protein binding (lipid solubility correlates with potency)
• Cocaine 1.5mg/kg max dose
• Lidocaine 4.5mg/kg; w/ epi 7 mg/kg max dose 
• Infiltration of tumescent can tolerate higher lidocaine doses due to rate of absorption (maximal concentration at 8-12 hours), around 35-55mg/kg
• It is OKAY to use lido w/ epi in hand/feet–> wait 25 minutes after injection for lowest risk of bleeding or highest vasoconstrictive effect (tested in context of wide-awake hand surg)
• Phentolamine reverses lidocaine
• Topical Anesthesia
• EMLA cream wait 1 hour

Blocks:

• Infraorbital nerve ipsi central incisor to two bicuspids
• TAP block (triangle of petit): triangle bounded by the latissimus dorsi, external oblique, and iliac crest –> infiltrate between internal oblique and transversus (two pops through fascia)
• PECS 1 (lateral and medial pectoral nerves) between pec major and pec minor
• PECS 2 (intercostal and intercostobrachial nerves) between pec minor and serratus
• Serratus block (long thoracic and thoracodorsal) between serratus and latissimus

Complications
Lidocaine Toxicity:

• 20% lipid emulsion
• local anesthetic toxicity can cause hypotension and cardiac arrest
• Signs and symptoms of lidocaine toxicity include dizziness, agitation, lethargy, tinnitus, metallic taste, perioral paresthesia, slurred speech, euphoria, hypotension, and bradycardia.
• Lidocaine in tumescent levels peak 8-12 hours
• Blood pressure least affected by lidocaine levels

Operating room concerns
Conscious Sedation: commonly used for anesthetic procedures, hypotension is common and should be treated with IVF first, vasopressors if fluid unsuccessful/inadequate

• Ketamine: IV, has shorter duration, lesser incidence of laryngospasm, lesser incidence of vomiting 
• The ideal conscious sedation combination is still midazolam and fentanyl given strong analgesia/amnesia and minimal respiratory depression

Complications

• Malignant hyperthermia: inherited in an autosomal dominant manner. Patients with myopathy present with a hypermetabolic reaction to anesthetic gases (halothane, enflurane, isoflurane, sevoflurane, desflurane)
• Also susceptible to succinylcholine
• Stop fluranes/turn off gas, cooling, saline, dantrolene
• Hyperkalemia, metabolic acidosis, hyperphosphatemia
• Rhabdomyolysis: Results in shock –> hyperkalemia, hypocalcemia, metabolic acidosis, compartment syndrome, acute renal failure

• Operative fire: open oxygen sources (masks and nasal cannula highest risks)
• Fire needs fuel, an oxidizer and an ignition source (fuels include alcohol cleaners, preps, drapes etc, ignition includes cautery), and oxidizer can be nitrous oxide or oxygen

Operative Positioning: 

• Lithotomy requires leg holders that incorporate heel support to prevent compression injury to the peroneal nerve
• Arm abduction should be limited to no greater than 90 degrees
• Dorsal extension of the arm should be avoided
• Decrease pressure on post-condylar groove of the humerus –> position arm in supination or supination or neutral positions
• When patient is in the prone position the neck should be well stabilized in neutral nonextended position

• Infectious Complications: 
• Needle stick from HCV: It is recommended that follow-up retesting be done at 6 weeks, 3 months, and 6 months in known HCV exposure cases.
• Prophylactic antibiosis: ASPS published consensus statement for systemic antibiotic prophylaxis for clean-contaminated, contaminated, or dirty plastic surgery of head/neck, orthognathic, hand, skin
• Also indicated for clean cases of the breast
• Other clean cases do not benefit from antibiotic prophylaxis
• SSI within 30 days, skin and subcutaneous tissues only (purulent drainage, positive cultures, diagnosis by surgeon)

Postoperative considerations
ERAS Protocols: Early Recovery After Surgery –> ideal protocols include local/regional anesthesia as well as oral pain medication

• Ex: includes liposomal bupivacaine
• Pregabalin can decrease narcotic needs after breast surgery (GABA analogue)

PONV: (post-operative nausea and vomiting) patient risk factors include female sex, history of PONV, non-smoking status, young age, type of surgery, BMI >30

• Anesthesia factors: opioids, inhalational anesthetics, nitrous oxide, general vs regional
• Can give aprepitant 40mg orally 1-3 hours prior to the induction of anesthesia (has high efficacy against opioid nausea)
• Other postoperative drugs for nausea include: zofran, droperidol, metoclopramide, promethazine, haloperidol, dexamethasone (for refractory nausea)

Post-Operative Delirium: acute brain dysfunction that is characterized by changes in levels of consciousness, inattention or disorganized thinking

• Hyperactive or hypoactive
• For patients at risk (elderly)–> should avoid benzodiazepines and antihistamines

Pulmonology

• Respiratory Quotient: indirect calorimetry measurements, calculated by VCO2/V02 (carbon dioxide produced/oxygen consumed)
• Ideal ratio is 0.8-0.9
• Value <0.8 underfed
• >1.0 suggest overfeeding (lipogenesis)
• Minute ventilation: calculated by multiplying respiratory rate and tidal volume (amount of air/gas displaced during each quiet breath)
• Residual volume is volume of air still remaining in the lungs after the most forcible exhalation
• Dead volume is air/gas that does not take part in gas exchange
• Inspiratory capacity is the volume of air that enters the lungs during the most forcible inspiration possible
• Vital capacity: the total amount of air that can be forcibly expired from the most forcible inspiration possible

Cardiac and Hematology concerns
Cardiac Concerns:

• Drug eluting stents should continue both aspirin and clopidogrel throughout surgery
• METS >4 may proceed with surgery
• If AF has existed for >48 hours than need TEE prior to cardioversion 
• VWF and VIII, give desmopressin prior – stimulates release of VWF to improve clotting
• Patients with acute MI should receive oxygen, aspirin, electrolyte supplementation (K >4, Mg >2) to prevent life threatening arrhythmias

Arrhythmias 
AV block: prolonged PR interval (first degree AV block), second degree AV block occurs with intermittent failure of the conduction of the impulse to the ventricles (dropped QRS complexes)
Multifocal atrial tachycardia: abnormal automaticity –> demonstrates irregular rate and rhythm (three or more morphologically different P waves) 110-140 beats
Afib: one of the most common dysrhythmias encountered in the ICU setting –> normal complex tachycardia without P waves; irregularly irregular
Aflutter: typically 2:1 ratio, evidenced by sawtooth flutter wave 
VTE using the Caprini risk assessment model

• ASPS VTE task force recommends those undergoing elective plastic surgery who have score of 7 or greater to have VTE risk reduction strategies: limiting OR time, weight reduction, discontinuation of hormone therapy, early postoperative mobilization, consider extended use of LMWH
• Major plastic surgery cases (>60 minutes) should undergo prevention
• Caprini risk 3-6 and major surgery should have LMWH or UH
• Highest risk factors include age >75, DVTPE or embolic stroke hx, Positive factor V leiden, HIT, elevated anticardiolipin or serum homocysteine or prothrombin or lupus anticoagulant, congenital or acquired thrombophilia, family hx of thrombosis

• Rivaroxaban (xarelto): inhibits factor Xa which helps convert prothrombin to thrombin

• Contraindicated in renal failure
• Andexxa or Factor Xa used to reverse xarelto
• ASA: interferes with platelet function
• Patients undergoing minor cutaneous surgery at no greater risk of hemmorrhagic complications than those with no agents
• Coumadin: affects vitamin K dependent factors (1972) X, IX, VII, II
• Heparin: prevents clot propagation by blocking thrombin-mediated activation of fibrinogen to fibrin 
• NSAIDS: inhibits COX1/COX2 and production of thromboxane A2
• Treatment of presumed DVT/PE includes IV heparin empirically

Other medical complications
Red Man Syndrome:  generalized discomfort, erythematous rash that involves the face, neck, upper torso. can be caused by vancomycin administration. 

• Treatment includes antihistamine, and resuming vancoymycin at slower rate once symptoms improve
• Not thought to be due to antibodies

Anaphylaxis: 

• Epinephrine should be administered intramuscularly (anterolateral thigh) as soon as dx is made (0.01mg/kg)
• Should also initiate measures of ABC (airway, breathing, and circulation)-

CKD from immunosuppression: (usually calcineurin inhibitors) –> pre transplant includes treating renal conditions, avoiding hypotension and hypertension, and limiting nephrotoxic drugs, limiting IV contrast, avoiding hypovolemia/ischemia time

• Postoperative recommendations include decreasing trough levels, treating hypertension, treating hyperglycemia, avoiding IV contrast

Renal Failure:

• AKI treatment in diabetic patient: isotonic crystalloids over colloids, glucose control, no diuretic or dopamine, Low protein
• FENA: Secret Urinal- SCr.Una/UCr.SNA x100 –> less than 1% is suggestive of prerenal disease, >2% is indicative of salt wasting ATN
• Free body water: amount of free water required to bring the sodium back to normal- (1-(na/140)

Acute Hyperkalemia: can treat with insulin and glucose, calcium gluconate (in scenario of EKG changes, give ca gluconate first), beta 2 agonists (albuterol), diuretics
Cerebral Edema: can result after head trauma (hyponatremia)

• Can use hypertonic saline (3%) to decrease intracranial pressure
• Can also use hyperventilation, mannitol, diuretics, and surgical decompression

Neurogenic diabetes insipidus: can be caused by head trauma, deficiency in vasopressin (ADH)
Sepsis:

• Antibiotics should be initiated as soon as possible after recognition and within 1 hour for both sepsis and septic shock –> delays associated increasing mortality and end organ damage
• Patients with septic shock can be clinically identified by having both of two criteria:
• Vasopressor requirement to maintain a mean arterial pressure of 65 mmHg or greater and
• Serum lactate level greater than 2 mmol/L (>18 mg/dL) in the absence of hypovolemia.
• Should include fluid resuscitation with IV crystalloid, transfuse if <7, vasopressors are second line after fluid resuscitation

Transplantation
Eligible organ donors: 

• Contraindications include no consent from parent or guardian, creutzfeldt-jakob disease, prion disease, metastatic cancer
• HIV no longer a contraindication
• Transplant Rejection: 
• Hyperacute: humoral response mediated by antibodies that are already present in the host at the time of transplantation (starts within minutes to hours)
• Accelerated: starts within 2nd-5th day after transplant –> form of hyperacute that results from pre-sensitization to donor tissue antigens
• Acute: regulated by activation of T cells –> can occur within first 6 months and it is characterized by short term organ dysfunction, and cutaneous/mucosal manifestations
• Chronic: antibody and cell mediated, indolent and progressive arterial sclerosis and fibrosis of transplanted organ (months to years)
• GVHD: cellular response caused by activation of transplanted grafts immune cells by the recipient cells – typically in BMT/stem cell txps

Trauma drama
Trauma and pregnancy:

• Perform FAST (abdominal ultrasound)
• Four hours of electronic fetal monitoring in patients >23 weeks gestation
• Determination of Rh status mandatory, those Rh negative mothers should be given rhogam within 72 hours to prevent sensitization 
• >32 weeks should logroll the patients on their left side to prevent compression of the vena cava by the gravid uterus
• Medications in pregnancy: local OK, avoid benzos, opiates oK

RRT: (rapid response) created to intervene in the care of a greater number of hospitalized patients at an earlier stage of clinical deterioration (preventing catastrophic events)

• Can be called for hypotension, rapid HR, respiratory distress, and altered consciousness 
• Code team responds to cardiac arrest, respiratory arrest, airway obstruction

BLS/ACLS:

• PEA: pulseless electrical activity –> use epinephrine, 1mg every 3-5 minutes
• CPR should not be halted for drug administration
• Should not shock in PEA
• CPR should be resumed immediately after shock delivery, without pausing for rhythm or pulse check
• 2 minutes of CPR, followed by rhythm check, CPR repeated
• High quality chest compressions include 100-120 a minute, 5cm of sternal decompression; rate of 30:2 or 10 breaths per minute

Confirmation of brain death: absence of brain stem reflexes needs to be present for brain death to occur. 

• Absence of corneal reflexes, absence of respiratory rate, absence of nystagmus on caloric testing, absence of mild cough or gag during tracheal manipulation
• Additionally need cause of brain death prior to brain death examination

Blood loss prevention in in craniosynostosis: TXA (tranexamic acid) –> inhibits conversion of plasminogen to plasmin
Tension Pneumothorax: clinical diagnosis of tachypnea, dyspnea, jugular venous distention, tracheal deviation to the opposite side, hypotension, hyperresonance on affected side

• If patient is hypotensive and tachypneic, treat with needle decompression at the second intercostal space –> followed by chest tube insertion
• Tension pneumothorax is when there is injury to the lung and air leakage into the pleural space that cannot escape–> each breath makes it worse

• Lower Extremity Trauma: 
• Early administration of abx within 3 hours has been shown to be the most important determinant of infection prevention after traumatic open fractures of LE (more important than time to washout, surgeon, severity of trauma etc)
• Cephalosporin +/-  GMN coverage in contaminated wounds