Chapter 18 Flashcards
adipose tissue
tissue containing fat cells
akathesia
continuous body movement in which an individual is restless of constantly paces about
akinesia
loss of voluntary muscle movement restless leg movement
analgesia
- lack of pain or feeling
- decreased response to pain; condition in which painful stimuli are not consciously interpreted (perceived as hurting
cation
positively charged ion
dehiscence
bursting open or separation of a would, usually along sutured line
dissociative anesthesia
form of general anesthesia in which patients do not appear to be unconscious
dyskineasia
uncontrollable involuntary repetitive movements; spastic
emetogenic
a substance that causes vomiting
euphoria
feeling of well-being or elation; feeling good
expectorate
eject from the mouth; split
extrapyramidal syndrome
movement disorders such as akathisia, dystonia, and parkinsonism caused by antipsychotic drug therapy
GABA (gamma-amino butyric acid)
- the principal inhibitory neuro transmitter in the brain stem and spinal cord
- inhibitory hyperpolarized the membrane. Barbiturates, benzodiazepines, etomidate, Propofol, and volatile anesthetics enhance GABAa
general anesthesia
deep state of unconsciousness in which there is no response to stimuli including painful stimuli
halogenated hyrocarbon
compound that contains halogen (chlorine, fluorine, bromine, iodine) combined with hydrogen and carbon
hyperpolarized
a change in the cell membrane potential that makes the inside of the cell even more negative so it cant respond to stimulations
hyperthermia
abnormally high body temperature
hypothalamus
center of the brain that influences mood, motivation, and perception of pain
hypotaxia
reduction of oxygen supply to tissues below the amount required for normal physiological function
induction of general anasthesisa
time required to take a patient from consciousness to Stage III of anesthesia
maintenance of general anesthesia
ability to keep a patient safely in stage III anesthesia
-monitoring of vital signs and ECG, EEG, and general observation
medullary depression
inhibition of automatic response controlled by the medulla, such as breathing or cardiac function
medullary paralysis
condition in which overdose of anesthetic shuts down cardiovascular and respiratory centers in the medulla, causing death
microcilia
tiny hairs that line the respiratory tract and continuously move, pushing secretions toward the mouth
minimal alveolar concentration (MAC)
standard reference for inhaled anesthetics indicating the lowest concentration of anesthetic in the alveoli (lungs) that keeps 50 percent of the patients from responding to stimuli (moving)
monitored anesthesia care (MAC)
- intravenous sedation with midazolam, followed by Propofol and/or fentanyl
- induces conscious sedation- patient can speak and answer questions but has altered state of awareness and minimal response to pain; can be light enough to permit interaction or heavy enough so patient cannot be aroused easily
neuroleptanalgesia
condition in which a patient is quiet and calm and has no response to pain after the combined administration of an opioid analgesic (fentanyl) and a tranquilizer (droperidol)
neuroleptanesthesia
state of unconsciousness plus neuroleptanalgesia produced by the combined administration of nitrous oxide, fentanyl and droperidol
neurotransmitter-gated ion channel
receptor-ion complex in the membrane that opens and allows rapid transmission of signal
NMDA (N-methyl D-aspartate) receptor
a glutamate receptor in the brain that causes excitation
- depolarizes the membrane, ketamine, nitrous oxide, and Propofol antagonize glutamate action
preferred anesthetic
produces adequate anesthesia with minimal side effects
synergism
when the action resulting from a combination of drugs is greater than the sum of their individual drug effects
therapeutic dose
dose at which the desired effect is produced
what happens in the limbic system with Mild Inhibition?
reduces anxiety
what happens in the limbic system with More Intense depression?
sleep (state of unconsciousness)
- can be awakened
what happens in the limbic system with General Anesthesia?
a deeper state of unconsciousness
Local Anesthesia
inhibits pain in a specific area of the body
General anesthesia
- causes complete loss of consciousness
- balanced anesthesia
- requires less absolute CNS depression because it uses other drugs such as anti anxiety and muscle relaxants that complement the action of anesthetic
balanced anesthesia
- requires less absolute CNS depression because it uses other drugs such as anti anxiety and muscle relaxants that complement the action of anesthetic
Stage I
of Anesthesia with CNS Depression
analgesia/lack of pain or feeling
- decreased response to pain
- euphoria/giddiness
Stage II
excitement (delirium)
- cerebral cortex if fully depressed
- achieved by the hypothalamus assuming control of body functions
- increased sympathetic tone
- elevated blood pressure and heart rate
- hyper reaction to stimulation
- cardiac erythema’s can occur in this stage
Stage III (Surgical Anesthesia)
- sleep
- normal blood pressure and respiration
- dilated pupils, loss of corneal reflex
- skeletal muscle relaxation
- paralysis of the diaphragm, hypotension occur
Stage IV
medullary paralysis
-represents an overdose of general anesthetic in which respiratory paralysis leas to circulatory collapses and death
What is the ideal state of General Anesthesia?
rapid induction and slow maintenance
What is the Mechanism of Action of General Anesthetics?
neurotransmitter-gated ION channels
- general anesthetics inhibit CNS activity by interacting with membrane ION channels
- general anesthetics bind with the GABAa Receptors
- hyperpolarized membranes
- general anesthetics bind with the GABAa Receptors
- Excitatory NMDA receptor
- antagonized by nitrous oxide, Propofol, and ketamine
- blocks cation movement and depolarization
Volatile Anestetics
liquid anesthetic that at room temperature volatilizes to a vapor, which, when inhaled, is capable of producing general anesthesia. Modulate excitatory and inhibitory synaptic transmissions
- Minimal alveolar concentration
- less when intravenous anesthetics enhance inhibitory receptors and antagonize excitatory receptors
ex- ether and halogenated hydrocarbons
Channel Proteins
a channel protein that is constantly open and allows solutes to pass into and out of the cell
Explain the Routes of Administration for General Anesthetics
inhalation or intravenous injection
- provide rapid delivery of the drug in the blood
- facilitates a smooth induction into anesthesia
What are the Solubility Characteristics of Inhalation Anesthetics?
- blood; gas partition coefficient
- the greater the value of the coefficient, higher the solubility of the drug in the blood
- volatile liquids - more soluble in the blood so like staying there
- nitrous oxide, desflurane, sevoflurane are not very soluble in the blood, so cant wait to move out of the blood
What does having a greater # of Coefficient mean?
What does having a less # of Coefficient mean?
-the more soluble the drug is in the blood.
What does having a less # of Coefficient mean?
-have a quicker onset of action because the drugs are ready to cross the CNS as soon as the circulation gets them there.
How does solubility effect the onset of action?
the more soluble the longer onset of action because they require more anesthetic to dissolve in the blood before enough drug molecules are available to cross into the brain
- once into the CNS the anesthetics modulate neuronal membranes to produce a state on anesthesia
Inhalation Anesthetic produce all stages of general anesthesia with the exception of what? Why?
nitrous-oxide
-its not potent enough to maintain stage III
(recently been re introduced in the US by manufacturer with updated delivery system for use in obstetrics
Inhalation Anesthetic - Delivery and Potency
- delivered to the alveoli and then to the blood for distribution to the tissues
- potency is measured by the concentration of drug in alveoli
What must be included in the Inhalation Anesthetic Mixture? Why?
air
- patients will rapidly develop hypoxia
Why are Intravenous Anesthetics given?
the are administered by IV because extravascular injections cause pain, swelling, and ulceration
Barbiturates
Intravenous Anesthetic
example-methohexital (Brevital)(C-IV)
- ultrashort-acting drug
- does not produce analgesia at any does
- may cause laryngospasm or bronchospasm
- contraindication- evidence of status asthmaticus or porphyria )abnormally metabolized hbg)
Benzodiazepines
Intravenous Anesthetic
example- midazolam (Versed)(C-IV)
- short acting CNS depressant- administered through the IV or rectal routes
- induces amnesia and sedation -used for induction of genera anesthesia- given with neuromuscular blocking drugs
- Flumazenil- specific receptor antagonist (only anesthetic class to have specific receptor antagonist ) - reverses the sedative effects of benzos when an over dose has occurred
Non Barbiturates- Propoful (Dipravan) not on the controlled substance list
(Intravenous Anesthetic)
- most commonly used parenteral anesthetic in the US
- used to initiate and maintain MAC sedation
- possesses a narrow margin of safety-can cause death if the medulla is fully depressed
- not regarded as an analgesic
- depresses cardiovascular and respiratory activity
- antiemetic anesthetic
- dependence is mostly psychological- cravings, loss of control over the amount and frequency of drug required to achieve desired effects
-PHARMACOLOGIC DOSE IS VER CLOSE TO THE LETHAL DOSE
Nonbarbiturates- etomidate (Amidate) no on the controlled substance list
(Intravenous Anesthetic)
- not used for continuous of maintenance anesthesia, only induction
- produces postoperative nausea and vomiting (PONV)
- used in high-risk surgical patients
- exerts less depressant effects on the heart and respiratory centers
Nonbarbiturates-Ketamine (Ketalar)
Intravenous Anesthetic
-Short-acting dissociative anesthetic - patients don’t appear to be unconscious
- Produces good analgesia
- Does not relax skeletal muscles, actually increases muscle tone
- Inhibits the excitatory pathway by a direct interaction with the NMDA receptor
- Stimulates the sympathetic nervous system
- Vivid dreams and hallucinations occur during the recovery period
Nonbarbiturates- Dexmedetomidine (Precedex)
Intravenous Anesthetic
- Potent alpha2 adrenergic agonist
- Produces analgesia, sedation, and reduced anxiety
Nonbarbiturates- Opioids and droperidol
Intravenous Anesthetic
- When administered together, the combination produces neuroleptanalgesia.
- Ex., fentanyl (C–II)and droperidol together cause a state quietness and calmness with no response to pain
- Extrapyramidal symptoms have been seen from the use of droperidol.
- Parkinsonian syndrome may occur occasionally.
CNS
Non- Anesthetic Effects of General Anesthetics
- Regulation of cerebral blood flow
- Change in intracranial pressure
- Seizure induction
- Nausea and vomiting
Postoperative nausea and vomititng (PONV)
Non- Anesthetic Effects of General Anesthetics
Volatile anesthetics are emetogenic.
Anesthetic agents increase the sensitivity of the vestibular center of the inner ear.
Rapid position change or movement may lead to the development of PONV
-Propofol is the only anesthetic to have evidence of reducing PONV
Respiratory System
Non- Anesthetic Effects of General Anesthetics
-Postoperative ventilatory failure and hypoxia
-Production of secretions
Muscle spasms along the respiratory tract
-inhalation anesthetics inhibit the microcilia that line the respiratory tract
Cardiovascular System
Non- Anesthetic Effects of General Anesthetics
- IV anesthetics increase in blood pressure and heart rate
- Cardiovascular depression may occur following depression of the medullary vasomotor centers.
- Higher doses may cause cardiovascular collapse.
Skeletal Muscle
Non- Anesthetic Effects of General Anesthetics
- Skeletal muscle relaxation occurs in Stage III.
- Inhalation anesthetics facilitate muscle incision and manipulation.
- Benzodiazepines interrupt excessive contractions in spasticity disorders and dyskinesias.
Hepatic and renal systems
Non- Anesthetic Effects of General Anesthetics
- Volatile anesthetics temporarily reduce renal and hepatic blood flow, glomerular filtration, and urine output -> usually no other significant effects other than temporary inhibition in urine output. Thus these drugs are used in patients with renal or hepatic disease.
- Hepatitis can be associated with the volatile anesthetics.
- Intravenous anesthetics are metabolized in the microsomal enzyme system of the liver.
Management of non-anesthetic effects of general anesthetics
Adjuncts to General Anesthesia
Pre-anesthetic and post-anesthetic medications are given to:
- Aid induction
- Counteract side effects of anesthesia
- Make recovery safe and more comfortable
- Fear, anxiety and pain are often associated with surgery.
- Anxiety and CNS stimulation tend to counteract a smooth induction into anesthesia
- CNS depressants may be administered before surgery to assist in a smooth induction
Examples of Adjunct Medications used with Anesthesia
analgesics
antianxiety
anitbiotics
Antiemetic drugs
Droperidol
(Adjunct Medications used with Anesthesia)
-effective as a single agent antiemetic for prophylaxis and treatment
Serotonin (5HT3) antagonists – ondansetron; first line therapy effective 4-6 hours
Neurokinin (NK1) antagonists – aprepitant; prophylaxis
Propofol and dexamethasone – prevents PONV up to 72 hours
Multimodal treatment for PONV
- Dopamine (d2) receptor antagonists
- antihistamines
- anticholinergics
(Adjunct Medications used with Anesthesia)
Used alone or in combination with the first-line drugs, but alone these drugs don’t have the efficacy that serotonin antagonists offer
Monitoring patients
- Allergic reactions – many are not aware of allergies they have; anaphylacytoid reactions are rare with anesthetics
- Black box warning
- Vital signs – should be monitored before, during, and after administration
- CNS depression – may experience a “hung over”or disoriented feeling
- Malignant hyperthermia – occurs only in certain individuals; increase is body temp, acidosis, electrolyte imbalance and shock
Drug interactions
- Droperidol – lengthen the QT interval in the heart
- Propofol – special handling is needed
Propofol handling technique
- Instructions on handling and disposition are provided on the box.
- Strict aseptic technique needs to be followed.
- Should be used with caution in patients with lipid metabolism disorders
Solution incompatibilities
- Drug admixture - Adding solutions to an existing intravenous line or by mixing two or more drugs in the same syringe
- Not all drugs are compatible.
Preferred Intravenous anesthetics
Propofol is the most frequently used induction anesthetic.
For MAC, midazolam, propofol, ketamine, fentanyl, alfentinil, and lidocaine are used.
Preferred Volatile anesthetics
Nitrous oxide, enflurane, sevoflurane, and isoflurane
