Glossary of Anesthesia Exam 3
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- What devices are used to monitor ventilation during anesthesia?
blood gas analyzer
- What device is used to monitor paO2 during anesthesia? What does paO2 stand for?
- blood gas analyzer
partial pressure of oxygen in blood
- What device is used to monitor % Hb saturation during anesthesia?
- pulse oximeter
- What parameters does an ECG measure during anesthesia?
- heart rate & rhythm
- What devices are used to monitor arterial blood pressure during anesthesia?
direct arterial catheter
- What does a capnometer measure?
- partial pressure of CO2 in expired air (pECO2)
- What is relationship b'twn pECO2 & paCO2 & what causes this relationship?
- paCO2 - pECO2 ~ 5-7 mm Hg
due to anatomic dead space ventilation
- why is paCO2 increased during anesthesia?
- anesthetic drugs depress sensitivity of medullary cells that drive ventilation
decreased contractility of diaphragm & intercostal mm. during anesthesia
- 2 reasons for low PECO2
large dead space fraction
- At what level of PECO2 should ventilatory support be initiated & why?
- pECO2 ~ 60 mm Hg
increased paCO2 --> respiratory acidosis
- At what value of paO2 is Hb 95-100% saturated in room air?
- paO2 > 80 mm Hg
- what are the 2 most common causes of hypoxemia (paO2 < 80 mm Hg)
- airway obstruction --> hypoventilation
- V/Q < 1: pneumonia, atelectasis
- V/Q > 1: vascular obstruction
- What should be done if Hb saturation < 90% in patient breathing room air?
- increase inspired O2 concentration to point that increases Hb saturation to > 95%
- nasal insufflation
- placement in O2 cage
- How do disturbances in cardiac rate & rhythm affect anesthetized patient?
- can compromise cardiac output, thereby interfering w/ O2 delivery
CO = HR x SV
- What are the determinants of arterial blood pressure & why is blood pressure used to define patient's CV health?
- MAP = CO x SVR
BP is sensed by cells in body that initiate baroreceptor reflex
BP is very easy to measure non-invasively
- What is the most routine management issue in veterinary anesthesia?
- mild to moderate hypotension
- Define autoregulation of bloodflow.
Under what range of MAP does autoregulation normally occur?
- normal process of O2 delivery (via blood flow) to any organ being determined by metabolic demand of those cells for O2
occurs over MAP range of 60-160 mm Hg
- What are the 2 most common causes of anesthesia-induced hypotension?
- autonomic imbalance: high PS tone relative sympathetic
- In treating anesthesia-induced hypotension, why do we 1st treat to increase cardiac output instead of SVR?
- increasing SVR accomplished by vasoconstriction, which decreases perfusion of organs
- What are the 4 steps in the protocol for tx of cardiac arrest?
- A: maintain patent airway
B: breathing (Ambubag or anesthetic machine to give 100% O2)
C: circulation via cardiac massage (internal vs. external)
D: defibrillation, drugs (epi, atropine)
- How does hypothermia affect requirements for anesthetic drugs?
- hypothermia decreases MAC --> decreases need for inhalational anesthetics
- What are the adverse effects of phenothiazines in horses & Boxer dogs?
- horses: penile paralysis
Boxers: very sensitive to sedative, vasodilatory effects
- Which species are sensitive to lidocaine, requiring a lower dose?
- cats, horses, small ruminants
- What are some reasons to use local anesthetics?
- decrease dorsal horn wind up
decrease stress response
avoid use of systemic anesthetics
improved CV function
- How do local anesthetics work?
- block nerve conduction by inhibiting influx of Na ions thru Na channels in nerve mem --> impairment of AP generation
- What are some adverse effects of local anesthetics?
- local site rxn
sedation --> agitation, seizures, coma
bupivicaine 16x more cardiotoxic than lidocaine --> bradycardia, hypotension
nerve injury: needle or drug induced
allergic rxn to preservative
- What sites would be blocked for a declaw procedure & what drugs would be used?
- combo of lidocaine & bupivicaine
radial n: mid-dorsal aspect of distal radius
median, ulnar nn.: on either side of distal aspect of accessory carpal pad
- Name 4 nerve blocks of the face.
infraorbital: blocks most of upper dental arcade, nasal cavity, upper lip
mental: blocks canine tooth
- Distinguish b'twn epidural, spinal, & caudal anesthesia.
- epidural: inject drug into space b'twn dura mater & wall of vertebral canal (epidural canal)
spinal: inject into subarachnoid space (b'twn arachnoid & pia mater)
caudal: inject into epidural canal at level of sacrococcygeal vertebrae
- Indications for neuraxial anesthesia
- caudal, urogenital, orthopedic, or thoracic sx
- Benefits of neuraxial opioids
- normal sympathetic nervous system & proprioception
lower systemic opioid effects
longer duration of action
- How do you confirm that you are in the epidural space?
- loss of resistance: air or saline, hanging drop, bubble compression
- Sites of end of spinal cord in cats, dogs, ruminants, horses, pigs
- cats: L6-L7, dogs: L3-L4
- do caudal injection at L7-S1
horses, ruminants, pigs: mid-sacral
- results of cephalad blockade
- anal relaxation, sweating, hind limb paresis/paralysis, Schiff-Sherrington like reflexes, abdominal distension
- What is the blood supply to the liver?
- 30% from hepatic a., 70% from portal v.
liver receives ~20% of CO
- Effects of hypoalbuminemia in anesthesia & how to tx
- albumin < 1.5 g/dl --> reduced plasma oncotic pressure --> pulmonary edema may occur w/ IV fluids
plasma transfusion or colloids (Hetastarch, Dextran) to replace albumin
- good & bad pre-meds for liver dz
- good (to a degree): benzodiazepines (at low doses), opioids (mixed agonists/antagonists may be a better choice: fewer side effects)
bad: phenothiazines, alpha-2 agonists both --> hypotension
- good & bad inducation agents for liver dz
propofol: total body clearance exceeds hepatic blood flow, may have apnea
etomidate: short duration d/t rapid redistribution
dissociatives: large metabolized by liver in dogs (don't use as maintenance agents)
thiobarbiturates: hypoproteinemia --> less protein binding --> increased free drug --> increased duration & depth of anesthesia
- inhalants used for liver dz
- halothane: BAD
-caused decreased hepatic blood flow
-increases hepatic blood flow
- What is the NM blocker of choice for hepatic dz?
- atracurium: not metabolized by liver
- What causes increased risk of regurgitation during C-section?
- displacement of stomach by uterus
dec. gastric motility
inc. intragastric pressure
weakened esophageal sphincter
- respiratory effects of pregnancy
- inc. RR, hyperventilation d/t distress & pain
dec. tidal volume d/t cranial displacement of diaphragm by gravid uterus
dec. functional residual capacity of lungs d/t cranial displacement of diaphragm by gravid uterus
- CV effects of pregnancy
- inc. HR, CO d/t pain & catecholamine release
dec. venous return when placed dorsally d/t compression of vena cava by gravid uterus
dec. cardiac reserve
dec. O2 carrying capacity of blood d/t dec. PCV, Hb
- misc. physiological effects of pregnancy
- inc. regurgitation
inc. sensitivity to inhalants & local anesthetics
avoid nephrotoxic drugs
- What factors lead to rapid diffusion of a drug across placenta?
- dec. degree of ionization
inc. lipid solubility
dec. molecular weight
dec. plasma protein binding
- principles of pre-meds for C-section
use ultra short acting drug that is also reversible
good combo: benzo + sedating opioid
give antacids to dec. likelihood of regurgitation
-Sellick maneuver: dorsal compression of larynx to occlude prox. esophagus during induction (before intubation)
AVOID alpha-2 agonists --> emesis, impaired uterine blood flow, uterine contractions
- induction agents for C-section
- propofol: rapid induction, recovery
etomidate: CV friendly, wide therapeutic index, may cause vomiting
thiopental: low doses (NOT in debilitated patients)
diazepam/ketamine: good for debilitated patients
- principles for maintenance of anesthesia for C-section
- use sevo/iso +/- nitrous oxide
avoid hyperventilation --> vasonconstriction --> dec. uterine blood flow
epidural/spinal can be used
- How is neonatal respiration different from adult?
- O2 consumption 2-3 times higher than in adults --> inc. respiratory rate
higher alveolar ventilation --> faster induction & recovery from inhalants
hypoxia may lead to apnea
- What are some CV differences in neonates vs. adults?
- dec. ventricular compliance: not able to inc. stroke volume when given an IV fluid bolus
dec. ability to compensate for hypotension
MAP much lower than in adults, HR higher
- principles of anesthesia for neonates
- accurate body wt. essential to calculate proper drug dosages
use anticholinergics (atropine, glyco) to maintain HR prior to & during anesthesia
sedation rarely needed
- What would be a good choice for a pre-med (if needed) in neonate/pediatric patient?
minimal to no effect on cardiac contractility
bradycardia/heart block can be counteracted by giving w/ anticholinergic
- Why should injectable induction agents be avoided in patients under 6-8 wks old?
- don't metabolize them well, have CV effects (d/t underdeveloped renal, hepatic, CV fn)
- What are the CV changes seen in geriatric patients?
- dec. cardiac reserve capacity
dec. baroreceptor activity, blood volume, BP, CO
myocardial dz: 25% of dogs 9-12, 33% of dogs > 13
inc. incidence of HCM, hyperthyroidism in cats
- What causes geriatric patients to be borderline hypoxic normally?
- loss of strength of mm. of respiration, dec. chest wall compliance, costochondral ossification --> small airway closure --> V/Q mismatch (inc. lung volume that will NOT be ventilated during normal breathing) --> lower resting PaO2 (60-80 mm Hg)
- What drugs are often used as pre-meds in geriatric patients?
- opioids (+/- benzodiazepine)
- Why should alpha-2 agonists & anticholinergics NOT be used in geriatric patients?
- alpha-2 agonists: cause vasoconstriction, reflex bradycardia
anticholinergics: cause tachycardia, tachyarrhythmias
- Use of induction agents in geriatric patients
- thiopental: DO NOT use w/ CV, resp. compromise, or in skinny animals, prolonged recovery w/ hepatic dz
dissociatives: DO NOT use w/ CV, resp. compromise d/t tachycardia, inc. R; prolonged recovery w/ hepatic or renal dz
propofol: a drug of choice
etomidate: drug of choice for geriatric patients w/ CV dz (always give w/ a benzo to prevent vomiting)
- principles of anesthetic maintenance in geriatric patients
- iso & sevo are good
keep as light as possible
give fluids (caution w/ cardiac dz, hypoproteinemia)
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