Premedication and Sedation

Premedication Goals

• Modern premedication aims to relieve anxiety using BZDs (-zolams).
• Goals include providing sedation and analgesia
• Prevent nausea and vomiting
• Prevent allergic reactions
• Reduce gastric fluid volume and acidity
• Improve coagulation
• Attenuate autonomic reflexes
• Caution required due to patients frequently being seen on the day of their surgery needing preoperative H&Ps.
• Patients may need to answer questions and sign documents preoperatively.
• Patients may wish to ask questions preoperatively.

Early Sedation

• Midazolam (BZD --> GABAa) can be administered orally or rectally
• Midazolam has little effect on respiration when given with Tylenol
• Midazolam causes sleepiness for a long period afterward
• Ketamine (CCB/NMDA ant) can be administered orally or IM
• Ketamine causes sedation and analgesia
• Ketamine may cause post-anesthesia delirium, especially in children
• Ketamine results in prolonged emergence
• Dexmedetomidine is an Alpha 2 agonist and can be administered IV or intrabuccally (pediatrics)
• Dexmedetomidine provides SA and decreases post-op pain

Pre-Op Ketamine

• Ketamine, when given orally or IM, provides sedation and analgesia, dose-dependent
• Use of Ketamine is associated with postanesthesia delirium, less common in children
• Ketamine may prolong emergence
• Ketamine is a dissociative anesthetic, sedative, analgesic, and antidepressant
• Ketamine has a rapid onset when administered IV/IM
• Ketamine causes an indirect catecholamine release and less drop in BP compared to propofol
• Ketamine is a direct cardiac depressant and synergistic with GABA agonists
• Ketamine is useful in pediatric and trauma/hypovolemic cases and for postop pain control via infusion
• Ketamine maintains airway reflexes

Contraindications of Depressant Meds

• Relative contraindications for depressant pre-meds include newborns (<1 year), elderly, and decreased level of consciousness
• Severe pulmonary disease/obstructive sleep apnea and hypovolemia also act as contraindications

Anticholinergics (Atropine)

• Anticholinergics, like atropine, dry secretions, which is not as important anymore
• They prevent bradycardia, critical in newborns/infants, adults w/ asymptomatic bradycardia, and also act as an antiemetic.

Post-Op Nausea and Vomiting

• PONV (post-operative nausea & vomiting) is caused by anesthetic factors such as opioids, especially postoperatively and nitrous oxide
• PONV is also caused by anticholinesterases when reversing neuromuscular blockade (neostigmine)
• Adverse consequences of PONV include tension on abdominal/thoracic sutures and aspiration
• Increased venous back pressure in the head and neck
• Increase intra-cranial & ocular pressure

Preventing Aspiration

• Aspiration prophylaxis includes H2 blockers to decrease gastric acid production and gastropropulsive agents (metoclopramide)
• Gastropropulsive agents are not used for GI obstruction
• Non-particulate antacids like BicitraⓇ or Sodium Citrate buffer can be used
• Rapid sequence induction with cricoid pressure is effective in emergency situations

Muscle Relaxants

• There are two types of neuromuscular blockers, depolarizing and nondepolarizing

Non-Depolarizing Muscle Relaxants

• Rocuronium, atracurium, cisatracurium, pancuronium, tubocurarine, mivacurium, doxacuriu are examples of nondepolarizing relaxants

Clinical Use of Muscle Relaxants

• Muscle relaxants are used clinically to facilitate tracheal intubation by paralyzing pharyngeal muscles to prevent bucking/coughing
• They are also used to provide muscle relaxation for surgery
• Muscle relaxants are used during ECT(electric shock therapy) because it causes violent seizures w/ limb movement
• They are useful in therapeutic hypothermia to stop muscles from shivering
• Muscle relaxants prevents patient-ventilator dyssynchrony by stopping patients from fighting the ventilator

Reversal of Muscle Relaxation

• Reversal of NMB (neuromuscular blockade)
• The dramatic increase in acetycholine would also cause an overdose at the muscarinic receptors
• Therefore reversal agents need to be given in combination w/ a muscarinic antagonist
• Termination sings include:
  • Head lift or leg lift for 15 sec
  • Grip strength test (ask to grab finger and squeeze)
  • Nerve stimulator (most objective test)
  • Train of four

Train of Four

• Stimulate a nerve 4 times to test muscle response/twitch with an electrode at thumb
• If 4/4 responses, 70-75% receptors blocked, this does not guarantee complete recovery
• 8% pts in the recovery room have residual blockade and need to monitor

Muscle Relaxants and Tachydysrhythmias

• There are two types of muscle relaxants: depolarizing and nondepolarizing

Depolarizing Muscle Relaxants

• The only example in clinical use is succinylcholine (sux)
• Succinylcholine's adverse effects include myalgias from fasciculation
• Succinylcholine may cause transient increase in serum K+,trigger malignant hyperthermia, tachydysrhythmias, and bradycardia, especially in children
• Hyperkalemia RF can stop the heart and cause dysrhythmias

Hyperkalemia and Muscle Injury

• Muscle injury such as burn, trauma, bedbound pt, myopathies, rhabdomyolysis causes K+ release from muscle
• Denervation of muscles: UMN injury (stroke), demyelinating lesion, denervation injury, head trauma, polyneuropathies, encephalopathy, SC injury

Pre-Op Evaluation Protocols

• Elements of evaluation include medical history allergies, cardiac history, pulmonary history, hematologic Hx, renal Hx, prior anesthesia/surgery, meds, supplements
• Physical exams such as vitals, heart, lungs, airway, OSA eval, fluid status (BP dec w/ less fluid), NM stability
• History like Planned procedure, family history, NPO, acute changes
• Avoid tests that won't change management, false positives lead to unnecessary further testing and procedures.

Tests Driven by H&P

• Only conduct tests driven by the H&P
• Hx of excessive bleeding or known coagulation disorder, liver disease, malnutrition / vit K deficiency, on anticoagulants will indicate coagulation studies
• A symptomatic patient with no hx will not require coagulation studies
• COPD, Lung Operation, Smoker + symptoms (sputum, coughing, wheezing) will indicate CXR
• An asymptomatic patient will not require CXR with age being a non factor.

Testing For EKG

• Heart disease, Arrhythmias or symptoms, risk factors for CAD, high-risk surgery (fluid shifts), including liver transplant, involving pancreas, splenectomy, long procedures, including neurosurgery, spinal surgery requires EKG
• Testing should be done if patient is asymptomatic, if age does not matter, and if patient is undergoing low-risk surgery
• Diabetes, Kidney disease, Psych pt (on lithium), contrast use (for creatinine), Pt on medications that affect kidney function, history of anemia, bleeding, immune deficit, Hx of chemo/radiation, chronic renal failure, estimated blood loss > 500 cc, Hx of bleeding/bruising requires electrolyte testing
• Testing should be done if EBL > 500 cc and withheld id EBL < 500 cc

Testing For Pregnancy

• Women of childbearing age, patient uncertain of the status, irregular menstrual hx, Pt requests all require pregnancy test
• Pregnancy testing is refused if patient refuses tests or screening
• Minimally invasive surgeries (cataracts, knee arthroscopy, etc.) usually requires no pre-op testing in absence of specific indications, short cases w/ no fluid shifts, abnormal tests do not necessarily cancel the case as these surgeries have minimal risk

ASA Classification and Asthma

• ASA physical status (PS) classification does not tell you a risk, just compares the group of patients
• Classifies physical status is designed as a simple description of the patient's condition useful for comparing groups of patients in studies and only deals w/ physical status
• ASA classification does NOT include the procedure you're doing.
• ASA Class 1: A normal healthy patient.
• ASA Class 2: Pt with mild systemic disease.
• ASA Class 3: Pt with severe systemic disease (e.g., end organ damage).
• ASA Class 4: Pt with severe systemic disease that is a constant threat to life(uremia, Stroke,..)
• ASA Class 5: Moribund patient who is not expected to survive without the surgery.
• ASA Class 6: Patient pronounced dead by neurological criteria (brain dead) going for organ harvest.
• Emergency surgery: save life or limb
• ASA 2 = pts w/ asthma but under control
• ASA 3 = not under control.
• ASA 4 = constant threat to life
• ASA 5 = My patient is dying!!
• If it's a heart failure, move 3 → 4

Pre-Op Clearance

• The surgeon has final responsibility for pre-op clearance for surgery.
• Only the surgeon clears for surgery; only an anesthesiologist clears for anesthesia.

Managing Steroid Use

• Patients who have had steroids within the past few months may have impaired adrenal function.
• Usually receive 100mg IV hydrocortisone pre-anesthesia + 100mg every 8 hours, at risk of acute Addisonian crisis w/ refractory hypotension.
• If pt has steroid use longer than 2 weeks in the past few years body cannot put proper cortisol, give supplement (hydrocortisone)

Management of Pre-Op Meds

• Problematic pre-op medications include diabetic medications
• For Insulin, administer one half the usual dose in the AM
• For oral hypoglycemic agents (metformin), hold because usually hyperglycemic the day of surgery (stress increased)
• For GLP-1 drugs Semaglutide (Ozempic; Wegovy), Tirzepatide (Mounjaro; Zepbound), Dulaglutide (Trulicity) and Liraglutide (Victoza), hold these drugs.
• SGLT-2 drugs Empagliflozin (Jardiance) Dapagliflozin (farxiga) stop these drugs 3 to 4 days prior to the procedure
• ACEIs (-pril) and ARBs (-sartan) Antihypertensives are okay preop except for ACEIs and ARBs
• Medications for opioid use disorder, Naltrexone, stop 3 days prior to surgery if opioid analgesics are anticipated
• Arrangements should be made for patients on methadone maintenance
• MAO inhibitors (also tramadol and St John's Wort)
• Psychiatric medications are okay except for MAOIs, SSRIs, ketamine, etc. can usually be continued.
• Anticoagulants and antiplatelet medications Big issue such as NOACs, Coumadin, Aspirin, NSAIDs, etc.

Supplemental Oxygen

• Supplemental oxygen is given because sedation (and anesthesia) reduce ventilation.
  • Ventilation is reduced due to:
    • Diminished response to hypoxia
    • Diminished response to hypercarbia
• Reduced muscle tone
  • Reduces tidal volume
  • Possible obstruction
• Everyone who gets sedation/anesthesia gets supplemental O2 pre and post (recovery room)

Supplemental Oxygen Devices

• Supplemental Oxygen include a nasal cannula
• High-Flow Nasal Cannula (HFNC)
• Simple mask, Venturi mask and a non-rebreather mask
• Pros of using this device:
  • All of these devices can be used in a conscious/responsive patient and are Simple to use, no special expertise is required
• Cons of using these devices:
  • None of these devices significantly increase tidal volume, actively remove CO2, or treat obstruction.

Upper Airway Obstruction

• Relieve the obstruction
• Chin lift → head tilt pull tongue forward away from the throat
• Head tilt lines up oral, pharyngeal, and laryngeal axes creates straight path for airflow
• Jaw thrust to avoid extending cervical spine, pulls tongue and soft tissue forward to open pharynx and relieve obstruction

Successful Endotracheal Intubation

• Endotracheal Tube contains Cuff, Murphy's Eye, Tube, Pilot balloon, Connector, Radiopaque Line, Depth Markings.
• Checking for Placement of ETT (endotracheal tube) you should look for things like:
  • Bilateral breath sounds (maybe); Absence of sounds in stomach (maybe) Chest wall movement (maybe)
  • Vapor in ETT (maybe) Expired CO2 (Winner!) – gold standard
  • Indications for the evaluation of upper airway obstruction

Evaluating Upper Airway Obstruction

• Signs of obstructions include:
  • Rocking boat movement
  • Jaw thrust and chin lift.
  • Accessory muscles starts to work harder
  • The clavicle becomes prominent w/ inspiration
  • Rocking chest motion (chest falls + abd rises opposite of normal) Diaphragm descends maximally → push abd contents up (abd rises)
  • Negative pressure w/o air coming into the chest cavity (chest falls)
  • Faint/absent breath sounds, which indicate that this is the clearest sign in adult
  • Nasal flaring and cyanosis (late and unreliable sign) indicate O2 saturation < 85%

Ambu Bag

• Self-inflating bag is used
• Bag-mask ventilation:
  • is imperative
  • Important to have a proper mask seal ; Do not press too hard on the patient's face
  • Do not fight the patient's ventilation
• Use once airway established from methods, such as:
  • Mask (attach to face)
  • Valve (create pressure)
  • Self-inflating bag (O2 reservoir)
  • Tubing (connect to O2 source)

Signs of Difficult Airway

• Difficulties during intubation involve:
  • Short mento-hyoid or mento-thyroid distance
  • Prominent maxilla -Immobility of TMJs
  • Inability to fully open mouth -Long overriding incisors
  • Limitations of neck extension/flexion, and a thick neck.
    • Can't intubate - can't ventilate FONA – Front of Neck Airway which includes Cricothyrotomy and Tracheostomy / Tracheotomy -Mallampati score describes/predicts intubation difficulty during pre-op

Mallampati Score

• Class 1: see everything; see vocal cord 3: see the hood of epiglottis 4: cannot see epiglottis

Rapid Sequence Induction

• Used if intubation is unsuccessful
• Involves Preoxygenation, Hypnosis/sedation and Muscle relaxant, Laryngoscopy, Intubation
• Higher failure rate than normal induction at risk for aspiration
  • Common Indications (at risk for aspiration) includes a Pregnant , Obese, Recently eaten fatty meal,Trauma pt Delayed gastric emptying (Bowel obstruction,Acute abd,Narcotic usage), Pt who swallowed gastrograffin (constant), Pt w/ bleeding in mouth , Increased complications compared to regular intubation & higher rate of failure

Aspiration

• The main risk is in b/w induction + securing the airway Increase risk w/ rapid intubation
• Aspiration pneumonia Particulate aspiration is the worst (take non-particulate antacids to decrease risk); , Interstitial edema Intra-alveolar hemorrhage Atelectasis Increase airway resistance Hypoxia
• Common Prevention includes: H2 blocker to decrease the production of gastric acid Gastropropulsive agent and Non-particulate antacid
• Rapid sequence induction w/ cricoid pressure for emergency situations

Cardiovascular Complications

• Pulmonary complications include : Post-op hypoventilation Post-op ciliary dysfunction

Atelectasis

• Worsened V/Q mismatch & shunt post-op mobilize the patient ,and use an incentive spirometer
• Cardiac/cardiovascular complications involve : Hypotension Hypertension Arrhythmias ,Perioperative myocardial infarction Myocardial depression Significant fluid shift: Thrombo-embolic phenomena

Risk Factors

• Pts with higher risk for aspiration Bronchospasm Anesthesia Pregnant women(from the start of the second trimester) Obese patients have recently eaten (esp. Meals high in fat)Patients have recently swallowed gastrograffin
• Patients that have W/ delayed gastric emptying or had Bleeding into the mouth, oropharynx patients
• Bronchospasm have a higher risk of having these complications ;Patients may have current or recent respiratory tract infection hyperactive airway

Hypotension During General Anesthesia

• Hypotension during anesthesia is usually due to decreased cardiac output, reduced systemic vascular resistance hypotension. Chronic hypotension can cause labile BP during case, Anaphylaxis hypotension and Rapid fluid shift causes hypotension
• Post op hypoventilation has close association with Pulmonary complications and has direct effect on "splinting" pain*
• Closing capacity increase in children (decrease ventilation for both)

Closing Capacity

• Closing capacity increase in children and elderly compared to FRC functional residual capacity They have increased atelectasis increase problems with ventilation
• Decrease problems with ventilation= Airway closes early that can worsen post atelectasis and prolong very time they inhale —> increase problems w/ ventilation

Respiration

• Dec resp muscles, strength and Increased wall compliance
• Dec FRC, Dec tidal volume and Minute ventilation .Increases RR to compensate
• Closing volume increased
• Higher high risk of hypoxemia and Smaller O2 reserve and rapid depletion

Impaired diaphragm

• Impaired diaphragm abdomen contents. Airway impairment and rapid depeletion of oxygen

Cardiac Output

• Heart muscle is child Heart muscle is child cardiac output stroke . Neonate need may require compression from neonatals

Hemocrat Levels

• Separation that has approx and is not out
• Neonatales have high decrease by Neonatales are deficient and volume for

1. blood high

Separation and Blood Volume

• Sepertation of blood for bleeding . Neonatales have and are deficient in

Neonatoles Blood Voulme

Blood volume in and decese in bleeding for

Hypothermia in Infants

• High body surface area relative to mass significantly increases heat loss Children get cold quickly increase cardiac demand ) Low subcutaneous fat Underdeveloped muscle . Primary mechanisms to combat hypothermia are peripheral vasoconstriction and Infants
• Infant has high BSA high heat loss combat hypothermia Shrinking is not effective management of small children – Clear liquids

Management

• Clear Liquids Clear to hours preop heavy meal . massive what to

Management

• Is give unit to the and later is related acute , which may occur

Separation and Transfusion

• Separational for
• Anoxia, OEE are

Tali

• Tranlson related to acute lung injury . Can be has

Risk Factor

• CPSp has highy