| What are preanesthetics? | they are used to calm the pt, relieve pain and block side effects of admin anesthetics or procedure itself
They include
H2 blockers (Famotidine and Ranitidine - reduce gastric acidity)
Benzodiazepines (Midazepam and diazepam - reduce anxiety facilitate amnesia)
Non opioids (acetaminophen) and Opioid (Fentanyl) as anelgisics.
Antihistamines (diphenhydramine - block allergic rxns)
Antiemetics (odanestion)
Anticholinergics (block bradycardia and secretion of fluids into respiratory tract) |
| What are neuromuscular blockers (NMBs)? | Facilitate tracheal intubation and surgery
Succinylcholine, Rocuronium and Vecocuronium |
| What are types of potent general anesthetics? What are stages of anesthesia? | Inhaled (volatile [halogenated HCs] or gas [N2O])
IV
Stages:
Admin, induction (onset), surgical anesthesia, maintenance (during these we keep giving anesthesia) then when we stop surgery we stop admin, and get into recovery |
| What are the general anesthetics? | . |
| How is potency of volatile liquid general anesthetics? | Minimal alveolar actions (MAC) expressed as the % of gas needed to achieve the effect.
Small for potent anesthetics, more lipid soluble (MAC decrease and potency increase) |
| How is uptake and distribution of inhaled anesthetics? | Alveolar Wash in (replace normal gases w/anesthetic as partial pressure increases transfer begins)
Anesthetic Uptake (related to solubility in blood [ if low like N2O then few molecules are needed to increase PP, achieve steady state rapidly, if high (halothane) less time needed], Cardiac output [lower == slower delivery], Alveolar-venous PP gradient [if higher gradient between blood and alveoli higher uptake])
Effect of different tissue types (organ w/high perfusion faster flow [brain, heart, liver, spleen...], poor perfusion slow flow [muscles])
Washout (NO2 exits faster than halothane) |
| How is mechanism of action of inhaled general anesthetics? | Increase sensitivity of GABA Rs, prolongs inhibitory chloride ion current, increase activity of glycine Rs and block excitatory postsynaptic current of nicotinic Rs. |
| What is nitrous oxide (N2O) | Non irritating potent analgesic
Weak general anesthetic, used in denistry and refractory pain in terminal illness
Combined w/other anesthetics, poorly soluble in blood (rapid action, diffusion hypoxia [due to speed movement])
No respiratory depression, no muscle relaxation, no CV effect or cerebral blood flow effect
Least hepatotoxic agent (safest) |
| What is halothane? | no longer used, potent anesthetic and weak analgesic, combined w/ N2O, Opioids and local anesthetics
Doesn't stimulate bronchial or salivary secretions, no nausea, relaxes muscles (including uterine used in GYN), pleasant odor (not irritating)
Better agent is Sevoflurane
Hepatotoxic in adults, strong resp depressant, vagomimetic (atropine sens. bradycardia)
causes arrythmia, sensitizes heart to catecholamine effects
Hypotension (best tx w/direct acting vasoconstrictors phenylephrin)
Malignant hyperthermia |
| What is isoflurane? | little metabolism (not toxic to liver or kidney)
doesn't induce cardiac arrythmia, doesn't sensitize heart to catecholamine, hypotension, pungent odor (+ respiratory reflexes- irritating) |
| What is desflurane? | Most rapid onset (lowest solubility), low volatility (given in special vaporizer), decrease vascular resistance perfuses well organs, irritating to airways, rare tissue toxicity. |
| What is sevoflurane? | Rapid onset, not irritating (like halothane), nephrotoxic |
| What is propolol? | Sedative/hypnotic, for induction or maintenance anesthesia, onset 30-40s, depresses CNS w/excitatory phenomena (twitching, spontaneous mvmnts, hiccups)
decrease BP w/out depressing myocardium, decrease ICP, respiratory depressant apnea, replaced thiopental due to euphoric feeling and antiemetic property, doesn't produce analgesia. |
| What is dexamedetomidine? | Sedative (ICU and surgery), sedation w/o respiratory depression, similar to clonidine (k2 Rs agonists in some brain areas) |
| What is ketamine? | Short acting, + dissociative state where pt is unconscious and doesn't feel pain
Amnesia, sedation and immobility
+ central symptoms outflow (+ heart increase BP and CO)
bronchodilator potent, benificial for pt w/ hypovolemia/CShock, asthamtics,.
Dream like state + hallucination |
| What are barbiturates? | No longer used, Thiopental
Potent anesthetic and weak analgesic, ultra short acting, high lipid soluble, quickly enters CNS and depresses it, redistributed out of brain rapidly, slow metabolism, not analgesic, respiratory depressant (apnea, cough, laryngospasm, bronchospasm)
Minor effect on CVS |
| How are benzodiazepines? | Midazepam, diazepam, lorazepam
Induce anesthesia, rapid uptake, redistributed to tissues, amnesia and sedation effect block effects of GABA, minimal CV effects and respiratory depressant. |
| What are opioids? | Fentanyl, Sulentanil and Remifentanil.
Analgesics/adjuncts, cause analgesia faster than morphine, not good for amnesia, respiratory depression, minimal cardio effects and cause nausea and vomiting. |
| What are local anesthetics? | Block nerve conduction from periphery to CNS, abolish sensation.
At high concentrations, block motor activity, most sensitive nerves are small unmyelinated
Admin (topical, infiltration, peripheral nerve blocks, neuroaxial)
Include (lidocaine [most used], bupivacaine, Ropivicaine, Mepivacaine, Procaine [ester])
Add vasoconstrictor EPI to local anesthetic, decrease rate of absorption and thus prolong effect |
| What are adverse effects of local anesthetics? | Seizures, Cardio collapse, allergic rxn (procaine) |
