BASIC PRINCIPLES OF ANESTHESIA
P H A R M AC O L O G Y
WHAT IS
ANESTHESIA?
A purposefully induced
physiologic state in which the
patient is rendered “without
feeling”
Anesthetics have effects on the
spinal cord, the cerebral cortex,
and the reticular activating
system (RAS) in the brain stem
ANESTHESIA
WITHOUT SENSATION
A state of controlled,
temporary loss of sensation or
awareness that is induced for
medical purposes
It may include analgesia,
muscular paralysis, amnesia,
and unconsciousness
Volatile Inhalation anesthetics (sevoflurane,
desflurane)
Potent narcotics (fentanyl, hydromorphone
(dilaudid), sufentanil, remifentanil)
Analgesics (acetaminophen (Tylenol), aspirin,
ketorolac, celecoxib (Celebrex),
anticonvulsants-gabapentin)
Benzodiazepines (midazolam, diazepam)
Local anesthetics (lidocaine, bupivacaine)
IV sedative hypnotic agents
(dexmedetomidine (Precedex), ketamine)
Induction drugs (diprivan (Propofol),
etomidate)
Neuromuscular blocking agents
(succinylcholine, rocuronium)
Adjunct drugs (antiemeticsondanseteron/zofran, PPI’spantoprazole/protonix)
• General anesthesia (GA) or general
endotracheal anesthesia (GETA)
• Total intravenous anesthesia (TIVA)
ANESTHETIC
TECHNIQUES
• Monitored anesthesia care (MAC)
• Local with sedation (L&S)
• Conscious sedation
• Neuraxial also referred to as regional
anesthesia (RA) (spinal or epidural)
• Peripheral nerve blocks (PNB’s)
LEVEL OF CONSCIOUSNESS
• Level of consciousness (LOC) and the presence of protective airway reflexes
determines the type and “depth” of anesthesia, differentiates between degrees
of sedation and general anesthesia
• The unconscious patient is unable to protect themselves from aspirating
stomach contents (loss of gag reflex) placing them at risk for aspiration
pneumonia (mortality rates 21-30%)
• With decreased LOC patient is likely to hypoventilate and is at risk of airway
obstruction and respiratory arrest
• The patient rendered unconscious is also likely to have fluctuations of heart
rate and blood pressure
What does
NPO mean?
GENERAL ANESTHESIA
• A combination of medications administered to
produce a state of unconsciousness with a loss of
protective airway reflexes, providing amnesia,
analgesia, and immobility
• Combination of agents are used to achieve a state
of general anesthesia: inhalation anesthetics (gas
vapors) delivered through the anesthesia machine
breathing circuit, intravenous agents (propofol and
ketamine), potent narcotics (fentanyl, dilaudid), and
neuromuscular blocking agents/paralytic drugs
(vecuronium, rocuronium)
• Requires a secured airway to control ventilation
and prevent aspiration
GENERAL
ENDOTRACHEAL
ANESTHESIA (GETA)
ANESTHESIA
MACHINE
REGIONAL
ANESTHESIA
NEURAXIAL
• Drugs administered into the
spinal space or the epidural
space to block sensory and
motor innervation from the
spinal cord at the level of
injection and distally (lower
half of the body)
• Drugs used include local
anesthetics (lidocaine,
bupivacaine) and narcotics
(fentanyl, morphine)
• Ex. Cesarean section, total
knee replacement
NEURAXIAL
PERIPHERAL
NERVE
BLOCKS
• The administration of local
anesthetic to nerves
innervating a particular
area of the body. Blocks
sensory and motor
innervation.
• Drugs administered
typically local anesthestic
(bupivacaine)
• Ex interscalene nerve block
provides anesthesia to the
arm
 Peripheral nerve block
 Abdominal wall T6-L1
 Ultrasound guided
technique
 Last 18-24 hrs approx.
SEDATION
• Drugs administered to
relieve anxiety and provide
pain relief
• Conscious---light--moderate---deep--unconscious
• Drugs typically
administered for sedation
include versed, fentanyl,
propofol, precedex,
lidocaine, ketamine
ANESTHESIA
• Anesthetic agents have an additive effect with the majority of drugs leading to
varying degrees of dose dependent myocardial and respiratory depression
• Maintain physiologic homeostasis and hemodynamic stability through
oxygenation, ventilation and perfusion in the anesthetized patient
• Deliver oxygen, provide adequate ventilation, administer fluid and blood
therapy, manipulate the physiology of the ANS, administration of cardiac and
vasoactive medications, alter the neuromodulation of pain, mitigate the stress
response to surgery
• Provide optimal conditions for the surgeon while providing patient safety,
comfort, while preventing iatrogenic harm
• Preoperative phase of care; assessment
and planning, informed consent
PHASES OF
ANESTHESIA
CARE
• Intraoperative phase of care;
administration of anesthesia, case
management : Induction---maintenance--emergence
• Postoperative phase of care; recovery
from anesthesia, management of side
effects and pain management
• Perioperative refers to care surrounding
surgery and procedures
• The anesthesia technique is determined
by the invasiveness of the planned
procedure
• Consideration is given to the patients
age, comorbidities or coexisting diseases
• Elective versus emergency surgery
CHOICE OF
ANESTHESIA
TECHNIQUE
• Required position for the procedure
• Duration of the procedure
• Anticipated recovery length/disposition
• NPO status/full stomach
• Airway evaluation/anticipated difficult
airway
• Surgeon, patient and anesthesia provider
preference
MONITORING
• All anesthetized patients
require monitoring: ECG,
BP, Capnography (etCO2
monitor), SpO2 (pulse
oximeter), and
temperature
• All patients require
adequate IV access for the
purpose of delivering fluid,
administering drugs and
resuscitation if needed.
PHARMACOLOGY
• Pharmacology is a branch of science that deals with the study of drugs and their
actions on living systems - that is, the study of how drugs work in the body
• Pharmacokinetics (PK) refers to the movement of drugs through the body. PK
describes a drug's exposure by characterizing absorption, distribution,
bioavailability, metabolism, and excretion as a function of time
• Pharmacodynamics (PD) refers to the body's biological response to drug, receptor,
potency, response curves
• Agonist a substance which initiates a physiologic response when combines with a
receptor
• Antagonist a substance that competes/interferes or blocks the physiologic action of
another
BENZODIAZEPINES
• Benzodiazepines have anxiolytic,
sedative, hypnotic, amnestic, and
anticonvulsant properties in the CNS
• Raise the level of the inhibitory
neurotransmitter GABA in the brain
• Diazepam (valium), lorazepam (ativan),
and midazolam (versed) are three of the
most important class members in the
practice of anesthesia.
• Alprazolam (xanax) and Clonazepam
(klonopin) are also commonly
prescribed benzo’s for treating anxiety
VERSED
 Supplied: 1mg/ml in 2 or 5ml vials
 Rapid onset (1-5 min) with relatively short duration
(highly lipophylic) max effect 20-60 min, recovery
time 2-6 hrs
 Minimal respiratory depression
 Dose: adult sedation 1-5mg IV, decrease dose in
patients with hepatic or renal impairment
 IV administration requires specialized care
setting/monitoring
 Reverse with Flumazenil (Romazicon) 0.2mg IV, q 1
min x4 doses
OPIOIDS
NARCOTICS
• Also known as “opioids,” the term “narcotic”
comes from the Greek word for “stupor” and
originally referred to a variety of substances that
dulled the senses and relieved pain
• “narcotic” refers to opium, opium derivatives,
and their semi-synthetic substitutes.
• A more current term for these drugs, is “opioid.”
Examples include heroin and pharmaceutical
drugs like OxyContin,Vicodin, codeine, morphine,
methadone, and fentanyl
Adverse Physiologic Effects of Opioids
• Ventilatory depression
• Muscle rigidity
OPIOIDS
• Nausea, vomiting
• Puritis
• Ileus
• Hyperalgesia
• Tolerance
• Addiction
FENTANYL CITRATE
 Brand: Sublimaze
 Class: Synthetic opioid, 100x more potent than
morphine
 Supplied: 50 mcg/ml in 2 or 5ml vial, po, parenteral,
transmucosal, transdermal
 Opioid agonist used with general, regional and spinal
anesthesia, acute and chronic pain management
 Strong agonist at mu and kappa opiate receptors,
mediates analgesia through the perception of pain
 Rapid onset, relatively short duration
 50-100mcg bolus doses IV
 Respiratory depression
 Reversed with naloxone (Narcan) 0.4-2mg IV, IM, or SC
up to total of 10mg
HYDROMORPHONE
• Brand: Dilaudid, Class: semisynthetic opioid agonist
(oral, rectal, SC, IM & IV),
• IV use for immediate release of moderate to severe
pain: po extended release for continuous therapy for
chronic pain
• Rapid onset, dosing for acute pain management, 0.2,
0.5, 1.0 mg IV bolus.
• Respiratory depressing effects, decrease HR & BP
• Immediate availability of airway support
• Reverse with narcan
INDUCTION AGENTS
• General anesthesia is a medically-induced loss of consciousness with
concurrent loss of protective reflexes due to anesthetic agents
• Induction of anesthesia can be accomplished through inhalation of gas through
a face mask but is commonly achieved through the administration of IV
induction agents
• An induction dose of an anesthetic drug will render the patient unconscious
and apneic requiring airway management and control of ventilation
• Induction agents include propofol, etomidate, methohexital, ketamine
PROPOFOL
• Brand: Diprivan, Class: IV anesthetic
• Most common induction agent used,
also used in ICU for sedation in
mechanically ventilated patients
• Sedation, Hypotension, Apnea,
• Antiemetic properties
• CNS depression decreases CMrO2
and CBF
• Supplied: 10/mg/ml in 20,50, or 100 ml
glass bottles
• Rapid onset with rapid clearance
(highly lipophilic)
• IV bolus dose 1.5-2 mg/kg, followed
by infusion 100-200 mcg/kg/min for
GA
• ICU sedation range 25-50 mcg/kg/min
PROPOFOL INFUSION
SYNDROME
• Propofol infusion syndrome (PRIS) is
a rare syndrome which affects
patients undergoing long-term
treatment with high doses of the
anesthetic and sedative drug propofol.
It can lead to cardiac failure,
rhabdomyolysis, metabolic acidosis,
and kidney failure, and is often fatal
• Certain risk factors for the
development of propofol infusion
syndrome are described, such as
appropriate propofol doses and
durations of administration,
carbohydrate depletion, severe illness,
and concomitant administration of
catecholamines and
glucocorticosteroids
• Brand: Brevital, Class: Barbiturate;
reduces neuronal activity, CNS
depressant, potentiates GABA
METHOHEXITAL
SODIUM
• Used alone as an anesthetic for short
procedures that are relatively painless, as
an induction agent, or as an adjunct drug.
Used in ECT therapy
• Rapid onset and ultra short acting
(highly lipophilic) Induction dose 1-1.5
mg/kg
• Respiratory depression, use with
extreme caution in patients with
coexisting pulmonary disease
ETOMIDATE
• Brand: Amidate Class: sedative hypnotic IV anesthetic, CNS depression
• Rapid onset and recovery (highly lipophilic)
• Supplied 2mg/ml solution in 10 ml single use vials
• Dose: 0.2-0.6 mg/kg for induction
• Useful due to minimal cardiac and respiratory depression, preserves HR & BP
• Adrenocortical suppression
KETAMINE HYDROCHLORIDE
• Brand: Ketalar Class: Non barbiturate sedative
hypnotic
• Produces intense analgesia but not amnestic, produces
a dissociative state
• Eyes open, reflexes and airway intact, preserves HR &
BP, cerebral vasodilator, causes increase in secretions
• Inhibits the (N-methyl-D-aspartate) NMDA receptor
• Similar in structure and action of PCP (phencyclidine)
• Supplied 10, 50, or 100 mg/ml vials
• Dose: 1-4.5 mg/kg IVP
• Alpha-adrenergic agonist
(activates alpha CNS receptors)
• Hypnotic & analgesic effects
• Decreases BP, HR
• Minimal respiratory effects
• IV infusion
• Short term sedation in ICU or
adjunct to general anesthesia
(GA)
• ETOH Withdrawal – adjunctive
treatment with benzodiazapine
Sevoflurane
Desflurane
 NMB’s are skeletal muscle
relaxants for intravenous (IV)
administration indicated as an
adjunct to general anesthesia, to
facilitate tracheal intubation, and
to provide skeletal muscle
relaxation during surgery or
mechanical ventilation
 Classified as depolarizing or non-
depolarizing based on their
mechanism of action
depolarizers and non-depolarizers
Depolarizing - Succinylcholine
 Brand: Anectine
 Supplied: 20 mg/ml in 10 ml vials
 Intubating dose: 1.5-2ml/kg
 Mimics acetylcholine
 Rapid onset ~ 30-60 sec (paralysis)
 Ultra short acting, rapidly metabolized
Negative Side effects:
• Fasciculation – myalgia
• Cardiac dysrhythmia-Hyperkalemia
• Increased ICP
• Malignant hyperthermia
 Malignant hyperthermia (MH) is a type of severe reaction that occurs in
response to particular medications used during general anesthesia, among
those who are susceptible. Hypermetabolic state with calcium release into
muscles. Symptoms include muscle rigidity, high fever, and a fast heart
rate. Complications can include muscle breakdown and high blood
potassium
 The classic signs of MH include hyperthermia to marked
degree, tachycardia, tachypnea, increased carbon dioxide production,
increased oxygen consumption, acidosis, muscle rigidity, and
rhabdomyolysis, all related to a hypermetabolic response
 Triggered by volatile inhalation anesthetics and succinylcholine
 RX: discontinue agent, hyperventilate, cool the patient, support
hemodynamics (HR & BP support)
 Dantrolene: (Dantrium, Ryanodex, Revonto) is used to treat the reaction
by stopping the release of calcium into the muscle
Nondepolarizing- Rocuronium Bromide
 Brand: Zemuron
 Supplied: 10 mg/ml in 5 0r 10 ml vials
 Intubating dose: 0.4-0.6 mg/ml
 Competes with acetylcholine (postjunctional receptors)
 Skeletal muscle paralysis (without depolarization)
 Different onset depending on the dose, slower rate of
recovery, metabolism
 Effects of these drugs monitored during anesthesia
 Non-depolarizing muscle relaxants can be reversed
LOCAL ANESTHETICS
“ L O S S O F S E N S AT I O N I N A D I S C R E T E R E G I O N O F T H E
B O DY ”
• Local anesthetics work by moving inside of the cell membrane
and binding to the Na+ channel, blocking the influx of ions,
stops the conduction of the nerve impulse and prevents further
signals from reaching the brain.
Two different classes due to molecular structure:
Amides – Lidocaine, Mepivacaine, Bupivacaine, Ropivacaine
Esters - Procaine, Chloroprocaine,Tetracaine
• Blocking of Na ion flux through plasma membrane
• pH of tissue matters
• Not an all-or-nothing phenomena
LOCAL ANESTHESIA
Different sensory or motor blockade
Drug deposited around the nerve/s
Additive: Epinephrine (typical 5mcg/ml = 1:200 000) decrease
breakdown through vasoconstriction
Adverse effects – systemic toxicity!! LAST
Early: lips tingling, circumoral numbness, hypotension………
• CNS - seizures
• Cardiovascular collapse (bupivacaine)
• Allergic reactions
Treat with infusion of intralipids and hemodynamic support
SPINAL OR EPIDURAL ANESTHESIA
What’s the difference and why
should you care?
SPINAL ANESTHESIA
Complications:
• Less time to perform rapid onset
• Hypotension
• Better quality of
sensory and motor
anesthesia
• High spinal
• Commonly used during
c-section, urologic
procedures etc
• Bradycardia
• Post–dural puncture
headache (PDH)
• Backache
• Urinary retention
EPIDURAL ANESTHESIA
• Advantages:
• less hypotension
than spinal
• ability to prolong the
anesthesia through
an in dwelling
catheter
• option to use
catheter for post op
pain management
POSTANESTHESIA CARE
• Pain control (pain scales)
• Mild to moderate
Oral medications/ IV medications
Agonist-antagonists
NSAIDS
• Moderate to severe
Parenteral or intraspinal opioids
Regional anesthesia
Nerve blocks
• Pre-emptive Analgesia
POSTANESTHESIA CARE
Most frequently encountered PACU
complications:
Need for airway support
Hypotension/hypertension
PONV
Dysrhythmias
Altered mental status
REPORT & HANDOFF
Patients name and age
Surgical procedure and anesthesia used
Drugs used
Preop vital signs
Coexisting medical diseases
Allergies
Estimated blood loss (EBL)
Urinary output (UO)
Fluid replacement
Special instructions
Pain management
CXR/ Labs
AIRWAY MANAGEMENT:
SUPPLEMENTAL OXYGEN DELIVERY
DEVICES
• Nasal cannula
• 1L-6L or 24-40 % (R/A = 21%)
• FiO2 increases about 4% w/ each liter O2
AI RWAY M AN AG E M E N T:
S UP P L E ME NTAL OX YG E N
D E L I VE RY D E V I CE S
• Simple mask
Oxygen flow usually 6-8 L
FiO2: 0.40-0.50%
• Venturi mask (Entrapment Device)
• FiO2: 24-28-35-40-50%
AI RWAY M AN AG E M E N T:
S UP P L E ME NTAL OX YG E N D E L I VE RY
DEVI CES
• Partial Rebreather Mask,
8-11 liters
FiO2: 50-75% FiO2
• Non-Rebreather Mask
12-15 liters
80-100% FiO2
One-way valve
device
Highest amount FiO2 delivery
POSTANESTHESIA CARE
• Discharge Criteria
• Determination made by anesthesia dept.
• 0bserved for 20-30 minutes post last dose of narcotics
• Easily aroused
• Full orientation
• Ability to maintain and protect airway
• Stable vital signs for 15-30 minute
• No obvious surgical complications
• Regional discharge criteria
Secondary but important
Controlled post operative pain
Controlled PONV
Normothermia
POSTOPERATIVE NAUSEA AND
VOMITING (PONV)
Direct relationship between the incidence of PONV and the duration of
surgery and anesthesia.
• Important patient outcome
• Patients report PONV as worse than postop pain
• Unanticipated delay in recovery, hospital admission
• Prevention includes pretreatment, selection of anesthetics less likely to cause
N&V
• Antiemetics perioperative (Zofran & Decadron) with rescue plan in PACU
• Multiple classes of antiemetics are recommended for high risk patients
undergoing high risk procedure procedures
Drug
Duration
Side Effects
Route
Onset
5-HT3-receptor
antagonist
IV
IM
PO/ODT
10 min
41 min
–
1
24 h
HA, lightheadedness
abdominal pain
constipation
Promethazine
Phenergan
Phenothiazine
IV
IM/PO/PR
5 min
20 min
4–6
4–6 h
Dry mouth,
blurred vision
Metoclopramide
Substituted
benzamide
IV
IM
PO
1–3 min
10–15 min
30–60 min
4
1–2 h
EPS,
drowsiness,
lassitude
Patch
4–24 h
1
Ondansetron
Class
Doses in
24 h
Zofran
Reglan
Transdermal
scopolamine
Anticholinergic
Zofran®, Anzemet®, Phenergan®, Compazine®, Reglan®, and Transderm Scop®
prescribing information.
HA = headache; EPS = extrapyramidal symptoms.
Zofran and Compazine are registered trademarks of GlaxoSmithKline.
Anzemet is a registered trademark of Aventis Pharmaceuticals Inc.
Phenergan and Reglan are registered trademarks of Wyeth Pharmaceuticals.
Up to 24 h Dry mouth,
post surgery drowsiness