Term
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Definition
| the use of a chemical agent on sensory neurons to produce a disruption of nerve impulse transmission, leading to a temporary loss of sensation. Like gen anes, exerts effect on neurons but the target is PNS and spinal cord. |
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Term
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Definition
| the anesthetist ensures that an increased volume of air, or more commonly, oxygen and anesthetic gases is delivered to the patient, although the pt initiates each inspiration. |
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Term
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Definition
| – the anesthetist delivers all of the air that is required by the pt, and the pt does not make spontaneous resp efforts. |
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Term
| Positive pressure ventilation |
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Definition
| any procedure by which the anesthetist assists or controls the delivery of oxygen and anesthetic gas to the pt’s lungs. . PPV is intended to ensure tha the animal receives adequate oxygen and is able to exhale adequate amounts of carbon dioxide. |
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Term
| In a healthy awake animal what is the main stimulus to breathe? |
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Definition
Ventilation has 2 parts, an active phase (inhalation) and a passive phase (exhalation).
Inhalation
- initiated by the respiratory center in the brain
- is normally triggered by an increased level of carbon dioxide in the arterial blood (PaCO2)
- As PaCO2 rises above a threshold level (~ 40mmHg), the resp center initiates the active inspiratory pahse by stimulating the intercostals muscles and diaphragm to move, expanding the thorax
- this creates a negative pressure (partial vacuum) w/in the chest, causing the lungs to expand.
- As the lungs expand, air moves thru the breathing passages and into the alveoli.
- When the lungs reach an adequate volume, nerve impulses feed back to the resp center, signaling the brain to stop the active phase of resp.
- the intercostal muscles and diaphragm relax, and exhalation takes place as the lungs deflate,
- exhalation is passive, no active muscle movement occurs (w/ the exception of exhalation during vigorous exercise, which has an active component).
- during exhalation, the carbon dioxide level in the blood begins to rise again, and after a short pause the resp center responds by initiating another inspiration. |
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Term
| . In a healthy awake animal, exhalation lasts at least how many times as long as inhalation? |
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Definition
| ~ 2x as long as inspiration |
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Term
| The normal tidal volume of an awake animal is how many, to how many, mL/kg? |
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Definition
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Term
| Respiratory minute volume |
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Definition
| – the total amount of air that moves into and out of the lungs in 1 minute. This value can be found by multiplying the average Vt by the resp rate. |
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Term
| . An anesthetist may expect to see what normal respiratory values in an anesthetized animal that is breathing room air? |
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Definition
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Term
| Differences in ventilation between awake and anesthetized animals: |
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Definition
Tranqs and gen anes may decrease the responsiveness of the resp center to carbon dioxide so insp does not occur as often despite the fact that the CO2 level may be signif. Elevated.
T and GA also relax the intercostals/diaphragm, so they expand less than normal during the insp phase. Because chest does not expand fully, Vt is reduced. May note that reservoir bag doesn’t collapse signif during the inhalation phase (ie, vol of gas inhaled is relatively small). Because Vt and RR are decreased, resp min vol is also decreased. |
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Term
| Potential problems with reduced Vt: |
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Definition
- hypercarbia
- hypoxemia
- Atelectasis – because Vt is reduced, the alveoli do not expand as fully as nrmal on inspiration. The alveoli in some sections of the lung, particularly those lower in the body, may partially collapse |
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Term
| predisposing factors for hypercarbia, hyperoxemia, and atelectasis: |
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Definition
- prolonged anesthesia (more than 90 min)
- obesity
- admin of neuromuscular blocking agents
- preexisting lung dz such as pneumonia
- recent head trauma
- surg procedures involving the chest or diaphragm
- species differences (esp horses) |
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Term
| Types of controlled ventilation: |
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Definition
- manual ventilation (bagging)
> periodic bagging (q 2 – 5 min) is adequate to expand lungs/ prevent atelectasis. Pressure not to exceed 20 cm H2O for sm animals/squeezed for 1 – 1.5 sec
> bagging throughout anes period is called intermittent mandatory ventilation
- mechanical ventilation
> not used for periodic bagging, but for intermittent mandatory ventilation
- pt must be intubated/on anes machine for ventilation, ventilating through mask does not give adequate amts of O2 and may cause the stomach to fill with air, increasing the risk of regurg. |
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Term
| Switching from spontaneous to intermittent mandatory breathing |
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Definition
- some pts, resp depression so severe that periodic bagging doesn’t provide the needed level of vent.
- pts who need intermittent mandatory ventilation - if go into resp arrest after induction (preex heart/lung dz, diaphragmatic hernia, etc), sm Vt (sm shallow breaths) or RR <6 breaths/min
- to start, use reservoir bag to superimpose positive pressure on the animal’s own spontaneous breathing efforts. For many pts, it is adequate to give a few larger than normal breaths manually then connect to ventilator or manual vent.
- the initial large Vt depresses the urge to breathe by lowering blood CO2 levels.
- once pt connected, usually stops spontaneous breathing efforts w/in 1 min.
- initial RR should be 8 – 20 resp/min, depending on pt size.
- if pt still making spon breathing efforts after 3 – 5 min, may need neuromuscular blocking agent
- once control established, Vent rate of 6 – 12 breaths/min usually adequate.
- pressure of 15 – 20 cm H2Q sm animals
- expiratory time 2x as long as inspiratory
- pop-off closed when bag squeezed but opened briefly q 2 – 3 breaths to allow gas to escape circuit.
- airway pressure must return to 0 during expiration so that cardiopulmonary fxn can normalize ( improving venous return of blood to the heart and increasing stroke volume) |
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Term
| To “wean” pt off intermittent mandatory breathing: |
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Definition
- turn off anes while continuing to vent lungs w/ O2
- reverse neuromuscular blocking agent if used
- gradually reduce the rate of insp to ~ 2 – 4/min while observing for evidence of spontaneous breathing
- when spon breathing seen, pt’s ventilation can be assisted by sqeezing a sm amt of air from the bag w/ each inspiration
- eventually, animal will regain the ability to maintain normal RR and Vt and vent assist can be discontinued |
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Term
| What is the most common acid-base abnormality in anesthetized patients? |
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Definition
| PaCO2 may rise, combining with water molecules in the bloodstream to form bicarbonate ions (HCO3-) and Hydrogen ions (H+). Accumulation of H+ cause pH of circulating blood o fall, leading to resp acidosis. Blood ph in awake animal is 7.38 to 7.42, anes animal may be as low as 7.20. |
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Term
| What specific problems may result from excessive controlled ventilation? |
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Definition
- excessive airway pressure may rupture alveoli (>pneumothorax or pneumomediastinum)
- Cardiac output may be decreased if + pressure maintained throughout resp cycle (insp/expiration)
- if vent rate too high, excessive amts CO2 may be exhaled, leading to resp alkalosis, which (if severe) may cause cerebral vasoconstriction and decreased cerebral blood flow.
- controlled vent is more effective at delivering anes gases, even from a precision out of circle vaporizer. Thus a vent will deliver more anes gas to pt which may lead to exacerbation of side effects |
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Term
| What should you do when intermittent mandatory manual ventilation is applied to a patient that is connected to a circle system with a vaporizer? |
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Definition
Turn the vaporizer to 0 before bagging, to prevent sudden vaporization of lg amts of gas as a result of the increased flow of carrier gas through the vaporizer. Mandatory controlled vent w/ an in-circle vaporizer is difficult and may be dangerous unless vaporizer is turned off /down/end tidal anes monitoring is avail.
In contrast, w/ an out of circle vaporizer, no need to turn vaporizer to 0, but should reduce settings or pt’s level of anes may be too deep due to increased delivery of anes to the lungs |
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Term
| What is the name of the type of ventilation where the anesthetist delivers all of the air required by the patient, and the patient does not make any spontaneous respiratory efforts? |
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Definition
| Controlled ventilation (manual ventilation/intermittent mandatory ventilation or mechanical ventilation) |
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Term
| . What are the predisposing factors for hypercarbia, hypoxemia, and atelectasis when ventilating an anesthetized patient? |
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Definition
- prolonged anesthesia (more than 90 min)
- obesity
- admin of neuromuscular blocking agents
- preexisting lung dz such as pneumonia
- recent head trauma
- surg procedures involving the chest or diaphragm
- species differences (esp horses |
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Term
| When properly set, a mechanical ventilator should precisely provide what ventilatory effects and parameters to a patient? |
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Definition
RR = 6 to 12 breaths/min
Duration of inspiration = 1 to 1.5 sec
Duration of expiration = 2 to 6 sec
Insp/exp ratio = 1:2 or 1:3
If pressure-cycled ventilator, pressure setting of 12 cm to 20 cm
Settings may vary depending on pt |
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Term
| . What are the specific types of mechanical ventilators? |
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Definition
- pressure-cycled ventilator – will supply air until the pressure reaches a pre-set level
- time-cycled ventilator – supplies air according to a set inspiratory time
- volume-cycled ventilator – delivers a pre-set Vt regardless of the pressure reqd. anesthetist must adjust the vol of gas to be delivered on inspiration (usually 10 to 15 mL/kg, less if respiration is to be assisted rather than controlled. |
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Term
| What is the recommended ventilation pressure for small animals with a closed chest? |
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Definition
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Term
| What is the recommended ventilation pressure for large animals with a closed chest? |
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Definition
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Term
| What are the specific indications for the use of neuromuscular blocking agents? |
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Definition
- pts who require mechanical ventilation
- orthopedic sx
- ophthalmic sx
- c-sections (provide abdo muscle relaxation and do not cross the placenta)
- difficult intubations
- occas in “balanced anesthesia” techniques
Administered ONLY in unconscious pts whose resp is controlled by IMM or MV. |
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Term
| effects and properties of depolarizing neuromuscular blocking agents. |
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Definition
NmBA act by interrupting normal transmission of impulses from motor neurons to the muscle synapse. The site of action is the nerve-muscle junction, where acetylcholine is released by the neurons in proximity to the muscle end plate. Tjere are 2 ways in which muscle-paralyzing agents may disrupt nervous transmission, and neuromuscular blocking agents are classified as depolarizing or nondepolarizing according to which of the two mechanisms applies.
>depolarizing agents, such as succinylcholine,
- cause a single surge of activity at the neuromuscular junction, followed by a period in which the muscle end plate is refractory to further stimulation.
- Animals given these agents may show spon muscle twitching followed by paralysis.
- Succinylcholine has a fast onset (20 sec) but a short duration of effect
- useful for rapid intubation.
- potential adverse effects of succinylcholine include hyperkalemia and cardiac arrhythmias |
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Term
| effects and properties of nondepolarizing neuromuscular blocking agents |
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Definition
NmBA act by interrupting normal transmission of impulses from motor neurons to the muscle synapse. The site of action is the nerve-muscle junction, where acetylcholine is released by the neurons in proximity to the muscle end plate. Tjere are 2 ways in which muscle-paralyzing agents may disrupt nervous transmission, and neuromuscular blocking agents are classified as depolarizing or nondepolarizing according to which of the two mechanisms applies.
> nondepolarizing agents, such as gallamine, pancuronium, atracurium besylate, and cisatracurium, act by blocking the receptors at the end plates.
- they do not cause an initial surge of activity at the neuromuscular junction, and spon muscle movements are not seen.
- potential adverse effects – histamine release, hypo or hypertension, tachycardia, and ventricular rhythms |
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Term
| Other drugs/tx that affect the potency of NmBA: |
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Definition
- Concurrent use of inhalant anes increases the potency
- recent tx w/ organophosphate insecticides also show increased susceptibility
- other drugs, incl corticosteroids, barbiturates, furosemide and other diuretics, anticancer drugs, epinephrine, tetracycline, and aminoglycoside abx such as gentamicin affect potency |
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Term
| What type of muscle is most affected by neuromuscular blocking agents? |
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Definition
- Only voluntary (skeletal) muscles are affected
- do not affect the involuntary muscles, incl cardiac, smooth muscle of intestine/bladder,.
- skeletal muscles are affected in a predictable order:
1st: facial/neck paralysis
2nd: tail, limbs, abdo muscles
3rd: intercostals muscles/diapraghm |
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Term
| What parameters can be used to monitor the anesthetic depth in a patient that has been given a neuromuscular blocking agent? |
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Definition
Depth may be difficult to assess due to inhibition or absence of normal reflex responses and the absence of jaw tone
- HR and BP may give some indication of depth
- If salivation, tongue curling and lacrimation are seen, pt is likely not deep enough for sx |
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Term
| Know and be able to identify the various nondepolarizing and depolarizing neuromuscular blocking agents. |
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Definition
- depolarizing agents – succinylcholine
- nondepolarizing agents – gallamine, pancuronium, atracurium besylate, and cisatracurium |
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Term
| . Local anesthetics block transmission of nerve impulses from which kinds of neurons? |
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Definition
| Sensory neurons and motor neurons,also autonomic nervous system neurons |
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Term
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Definition
- almost immediate onset
- duration 1 – 2 hrs
- conc of .5 – 2%
- can be diluted w/ sterile saline (not water) if a lower conc desired |
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Term
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Definition
- onset 20 min
- duration 6 hrs
- conc of .25 - .5%
- can be diluted w/ sterile saline (not water) if a lower conc desired |
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Term
| What is the specific mode of action of local anesthetic agents? |
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Definition
When deposited in proximity to the neuron, local anes result in antagonism, or blockade, of sodium channels.
- when the sodium channels of a neuron are blocked, the neuron cannot generate electrical impulses
- locals therefore act as a membrane stabilizer, stopping the process of nerve conduction
- reversal of this effect occurs as the drug is absorbed into local circulation
- local anes are then redistributed to the liver, where they are metabolized.
> loss of sensation and loss of motor ability are seen concurrently
- motor neurons (convey impulses from the brain to muscle fibers and is resp for initiating and controlling voluntary movements) are also sensitive to local anes and may cause temp paresis (weakness) or paralysis in the area served by the affected motor neurons.
- also affect the neurons of the autonomic nervous system. These neurons convey impulses between the brain and the blood vessels (incl heart). If exposed to l.a., may be temp loss of fxn. This is most important in the SNS and is called a sympathetic blockade.
- main effect of a sympathetic blockade in the peripheral tissues is vasodilation, resulting in flushing and increased skin tem of the affected area. If severe, vasodilation may cauase BP to fall.
- symp blockade may also be seen after epidural blocks w/ lidocaine and other l.a. because sympathetic ganglia adjacent to the vertebrae are affected. If symp bloc occurs w/in the thoracic spinal cord (as may occur if l.a. is allowed to diffuse into the thoracic spinal canal), sympathetic innervation to the heart may be blocked, resulting in bradycardia and impaired ventricular contractions (undesireable) |
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Term
| . Does epinephrine prolong the effects of a local anesthetic when it mixed with the drug? |
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Definition
- conc of Epi used is 0.01 mg/ml of lidocaine
- lidocaine may be purchased w/ or w/o epi
- Epi is added to lidocaine for 2 reasons
1. Epi causes constriction of blood vessels in the area of inj. This decreases the rate of drug absorption and prolongs the effect by nearly 50%
2. by causing vasoconstriction, epi reduces the conc of l.a. that enters the bloodstream at any given time, thereby reducing toxicity of the drug. Most effective for short-acting drugs like lidocaine and less helpful for long-acting such as bupivicaine.
Lidocaine w/ epi should NOT be used IV, should NOT be used at an incision site (may impair healing) or on the ears, tail or digits (may compromise circulation). Use w/ caution animals known heart dz, may cause arrhythmias |
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Term
| Effectiveness of local anes: |
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Definition
highly acidic, - obstacles such as scar tissue, fat, edema, hemorrhage impede diffusion
- relatively ineffective in areas of inflamed or infected tissue (w/ active inflamm tissue pH is resulting in rapid inactivation of the drug)
- |
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Term
| When used in a line block, a local anesthetic agent will have a direct effect on which part of the nervous system? |
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Definition
- Line blocks are positioned between the target area and the spinal cord to block the sensory neurons most effectively
- used when target is an area of tissue that is served by numerous small nerves
- done by inserting the needle along the proposed line of infiltration, then gradually withdrawing the needle while simultaneously injecting a sm amt of local anes |
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Term
| . By which methods should local anesthetics be, and not be, administered? |
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Definition
- can be injected
- can be absorbed by mm, incl conjuctiva, nose, mouth, latynx, lining of urethra
can be administered as topical sprays, drops or ointment to these areas
- can be used as patches
- can be introduced into a joint, nerve plexus, vein, or the epidural space |
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Term
| What is the name of the procedure when a local anesthetic is injected around a single major nerve? |
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Definition
Nerve block
Used for:
- lameness exams in horses
- corneal blocks for dehoring cattle
- paravertebral blocks for abdo sx or c-sections in cattle
- dental blocks in dogs/cats (infraorbital, mental, mandibular, and maxillary nerve blocks)
- intercostal nerve blocks in animals undergoing chest sx
- infiltration of nerves during amputation of a limb (0.5ml of 0.5% bupivacaine, injected into and around the nerve during sx)
- nerve block to provide analgesia for declawing cats |
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Term
| . The maximum subcutaneous dose of lidocaine for a dog is how many mg/kg? |
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Definition
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Term
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Definition
| a local anes is injected into a major nerve plexus or in proximity to the spinal cord, resulting in the blockage of nervous impulses to and from a relatively large area, Ex: paravertebral, apidural, spinal (intrathecal), and brachial plexus blocks |
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Term
| How far caudally does the spinal cord of a cat extend? |
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Definition
| In cats the spinal cord extends as far caudally as S1, and there is a slight risk of entering the subarachnoid space when performing epidural anesthesia. |
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Term
| How far caudally does the spinal cord of a dog extend? |
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Definition
| In dogs the spinal cord normally ends at L6 or L7. |
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Term
| Where is epidural anes performed? |
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Definition
| Local anes is deposited in the epidural space, between the dura mater and the vertebrae. Spinal nerves pass through the epi space as they exit through the intervertebral foramina and are affected by local anes and other drugs deposited in this space. In dogs the location of the block is between the last lumbar vertebrae (L7) and the sacrum. |
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Term
| When performing a Bier block the anesthetist should use which drug or combination of drugs? |
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Definition
| **Bupivacaine should not be used for IV regional anesthesia as cardiotoxicity is likely after release of the tourniquet** |
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Term
| . Local anesthetic agents such as lidocaine or proparacaine do not work well when applied by which method(s)? |
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Definition
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Term
| What are the clinical signs of systemic toxicity from a local anesthetic agent? |
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Definition
| Sedation, followed by nausea, restlessness, muscle twitching, hyperexcitability, seizures, respiratory depression, and eventually, coma |
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Term
| . What local anesthetic should not be used for IV regional anesthesia as it can cause cardiotoxicity after the tourniquet is released. |
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Definition
| **Bupivacaine should not be used for IV regional anesthesia as cardiotoxicity is likely after release of the tourniquet** |
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Term
| When performing epidural injections in the dog, the epidural needle is placed between which two vertebrae? |
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Definition
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Term
| Paravertebral anesthesia is preformed on the dorsal and ventral roots of which spinal nerves in cattle? |
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Definition
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Term
| Which local analgesic procedures can be used to assist with post surgical analgesia in cats that are being declawed? |
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Definition
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Term
| Which specialized surgical instruments are used for OHE’s? |
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Definition
| may or may not use a spay hook (Snook hook) – used to exteriorize the uterine horn, allowing a smaller incison |
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Term
| . Which significant complications should the technician be most aware of after an animal has been spayed and is in the recovery cage? |
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Definition
Intra-abdominal hemorrhage
If ligation of a bleeding stump was attempted w/o proper visualization, renal dysfunction may occur secondary to ureteral ligation |
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Term
| Know the signs, symptoms, and sequelae to pyometria. |
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Definition
Seen w/in 4 – 8 wks after last heat cycle
- decreased appetite
- lethargy
- increased thirst and urination
- foul-smelling vaginal d/c in some but not all cases
- fluid-filled uterus may be detected by xray
Most affected are 6+ intact females
Stump pyo poss in spayed fem if ovarian tissue was left behind during the spay |
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Term
| . How is pyometria treated? |
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Definition
OHE recommended tx
IV abx post-op until stable
Oral abx 7 – 10 days post-op
O may elect medical mngmt for valuable breeder – this should be discouraged due to risk of severe complications
- could rupture leading to septicemia and /or endotoxemia
- rate of pyo recurrence after med tx is as high as 77% |
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Term
| Which of the anatomic structures should be examined and palpated before an anesthetic agent is administered to a patient undergoing a neuter? |
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Definition
| The scrotum should be palpated and examined for the presence of both testicles |
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Term
| Know the indications for, and the possible complications from, castrations. |
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Definition
- hemorrhage
- scrotal hematoma
(cold compresses can be placed to aid in hemostasis post op if hemorrhage
scrotal ablation may be needed if hemostasis unsuccessful)
- self-inflicted trauma
-infxn
- dehiscence |
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Term
| . Know the specific signs, symptoms, and indications for cystotomies. |
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Definition
- to remove cystic calculi
(most frequent is struvite – 40-50%)
- hematuria
- stranguria
- dysuria
- and pollakiuria |
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Term
| 55. Know the specific signs, symptoms, and indications for cystotomies. |
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Definition
- to remove cystic calculi
(most frequent is struvite – 40-50%)
- neoplasia(most common bladder cancer dogs/cats is transitional cell carcinoma)
- congenital abnormalities
Symptoms of bladder stones
- hematuria
- stranguria
- dysuria
- and pollakiuria |
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Term
| . What are the most appropriate diagnostic studies to perform when an animal is presented for possible bladder stones? |
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Definition
|
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Term
| . A patient is brought to an emergency clinic after being struck by a motorcycle. The surgeon is set to perform abdominal surgery on this dog. Which procedures should, and should not, be done before surgery? |
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Definition
- Bladder should NOT be expressed as bladder condition may be in question
- Abdominocentesis – creatinine and urea measurements of the abdo cavity fluid is compared with blood serum levels |
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Term
| When is it most appropriate to begin analgesia on surgical patients? |
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Definition
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Term
| Where should the tourniquet be placed before declaw sx? |
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Definition
| Distal to the elbow – placing it proximal to the elbow can cause permanent radial nerve damage |
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Term
| When is the use of topical alcohol for scrubbing contraindicated before surgery? |
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Definition
| If the laser method for declawing is used, alcohol is contraindicated as it will likely ignite when the laser hits the area |
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Term
| What are the instructions you should, and should not, give to a client who is bringing her cat home from the clinic after declawing? |
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Definition
-pain meds 4 – 5 days
- shredded paper or pelleted litter for 10 days
- restricted activity/excessive grooming discouraged until healed |
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