Term
| Mice are usually best picked up by which structure? |
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Definition
- By the base of the tail, then allowed to rest on operator’s forearm for assessment of external appearance
- Allow them to rest on a rough surface such as a towel, then grasp by the skin overlying the shoulders, gripping the tail between the fingers of the other hand
- SQ admin of meds can be done singlehandedly in skin over shoulders
- Intraperitoneal/IM inj by asst |
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Term
| What bad thing(s) can result from over restraint of a mouse by the scruff of their neck? |
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Definition
| May interfere w/ respiration |
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Term
| Rats are usually best picked up by which method? |
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Definition
Picked up around shoulders out of box
Allowed to rest on handler’s forearm and be gently retrained by tail or around shoulders
If resists handling, can be picked up by base of tail as mice are, placed on a rough surface and grasped around shoulders |
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Term
| Guinea pigs are usually best picked up by which method? |
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Definition
- On initial exam may be immobile but may become very agitated and run around
- Can be grasped swiftly and firmly around the shoulders, other hand used to support hindquarters
- For SQ inj, can place hands on either side of body to restrain on table |
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Term
| What is the key to picking up and restraining rabbits? |
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Definition
- Provide support to the animal’s back at all times and never leave animal unrestrained on table
- Grasp by skin over shoulders and support body weight with other hand
- Do not release until feet in firm contact with the table surface
- Then restrain by gently holding skin over shoulders |
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Term
| What is the name of the pigment that may appear red around the eyes of rats? |
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Definition
- Buildup of porphyrin secretions
- Black or reddish brown d/c, bright red when wiped w/ damp swab
- Nonspecific response to stress or illness such as chronic resp dz |
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Term
| Know the limitations of using the capillary refill time small mammals to assess perfusion |
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Definition
- Difficult to assess mm in sm rodents
- In rabbits both the gingival/conjunctiva can be inspected easily
- Rabbits have normal reddish coloration, CRT <1s |
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Term
| Know how to determine the degree of dehydration in small mammals. |
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Definition
- Loss of skin tone in response to dehydration is difficult to detect in sm animals
- If loss of elasticity is noted, usually indicates more than 10% of body wt has been lost as fluid
- When markedly dehydrated, eyes become sunken, commonly seen in rabbits and sm mammals anes for dental tx. Because dz may have been present for some time, may have prolonged period of reduced food/water intake. Essential that they get supportive fluid therapy before anes |
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Term
| Food should be made available to rabbits until how many to how many hours before anesthesia? |
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Definition
- Strongly recommended that food be available up until 1 – 2 hrs before anes and provided again as soon as animal has recovered. (many sm animals are nocturnal and may not eat during day)
- withholding food may cause hypoglycemia (rabbits/guinea pigs w/h food can trigger digestive disturbances leading to endotoxemia, which can be fatal)
- sm rodents and rabbits do not vomit, generally no reason to w/h |
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Term
| What are the suitable sites for fluid administration in small mammals? |
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Definition
- Rabbits – marginal ear veins and cephalic veins may be used
- Can give SQ, IP (intraperitoneal) or IO (intraosseous)
- SQ fluids are unlikely to be effective if dehydration is severe
- IO is valuable means of providing prolonged fluid therapy in rabbits, guinea pigs and rats
- If in poor condition, make every attempt to commence supportive therapy (fluids) before anes |
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Term
| Volumes of fluid admin for adult small mammals |
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Definition
IP
- Gerbil 2 – 3 ml
- Guinea pig 20 ml
- Hamster 3 ml
- Mouse 2 ml
- Rabbit 50 ml
- Rat 5 ml
SQ
- Gerbil 1-2 ml
- Guinea pig 10-20 ml
- Hamster 3 ml
- Mouse 1- 2 ml
- Rabbit 30 - 50 ml
- Rat 5 ml
- fluids should be warmed to body temp before admin
- maint rates 100ml/kg q 24 hrs |
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Term
| Why should glycopyrrolate be used in rabbits instead of atropine? |
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Definition
| Atropine is often relatively ineffective in rabbits because many animals have high levels of atropinase, an enzyme that inactivates atropine |
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Term
| What would be the greatest drawback when using ketamine in small rodents? |
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Definition
| Salivation (preanesthetics can reduce this) |
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Term
| Excellent sedative for rodents (esp rabbits, who are often immobilized) |
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Definition
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Term
| Which drug is generally considered to the opioid analgesic of choice in small mammals because of its longer duration of action? |
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Definition
- Opioid analgesics may be given 30 – 45 min before induction of anesthesia. This reduces the concentration of volatile anes needed to maintain anes and provides preemptive anes
- Butorphanol |
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Term
| What is generally considered the safest and most effective method of providing general anesthesia in small rodents? |
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Definition
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Term
| What would be a common result of using inhalant agents for anesthetic induction in rabbits? |
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Definition
- Freq hold breath when exposed to inhalants
- Breath-holding may be prolonged, may cause marked bradycardia
- Should be pre-med (ex: ace, diazepam, midazolam, or medetomidine)before mask or chamber induction in order to avoid violent struggling and prolonged breath-holding
- After premed takes effect, a mask used to admin 100% O2 for 1 – 2 min before inhalant agent
- Animal may still hold breath but unlikely to struggle
- If breath-holding occurs, briefly remove mask and replace when breathing again
- Alternatively, admin a short-acting induction agent such as propofol and maintain anes w/ an induction agent |
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Term
| The ability to induce anesthesia by IV injection is usually limited to which species? |
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Definition
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Term
| Marked sedation in rabbits and rodents |
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Definition
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Term
| . Know the appropriate drugs that are used for preanesthetics and induction agents in rodents and small rabbits |
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Definition
- Inhalants are anes method of choice for sm mammals
Inj anesthetics of choice
- ketamine w/ an alpha2 agonist
- fentanyl-fluanisone w/ a benzodiazepine
if inj drug admin and desired depth of anes not reached, possible to admin an addtl drug to deepen anes but often preferable to deepen anesthesia w/ a low concentration of an inhalant agent or alternatively to provide local anesthesia by infiltrating the sx site w/ a local anesthetic
in these cases, a low dose of an inj anesthetic combo can be given to provide a light plane of anes, and inhalation anes or local anes can be use dto provide sx anes |
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Term
| Know which endotracheal tubes are most appropriate for rodents and rabbits. |
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Definition
- Rodents generally too small
- Relatively simple to intubate rabbits
- Uncuffed ET tube
- 3 – 3.5mm (3kg rabbit)
- very small rabbits (<800g) less than 2.5mm
- or maintain airway w/ laryngeal masks |
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Term
| alternative to intubation |
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Definition
- nasal catheter can be passed and positioned in back of pharynx
- allows O2 supp during oral sx but does not allow assist ventilation
- can also be used in sm rodents to deliver O2 or anes gases, esp useful during dental procedures
- waste anes gases can be removed by placing an extract tube close to the animal’s nose and the potential problem reduced by using approp low fresh gas flows |
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Term
| Know the principles and precautions for using breathing circuits in small rabbits. |
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Definition
- Out of circuit precision vaporizer
- Open, non-rebreathing systems preferred to closed-circuit systems because they offer less resistance and have less equipment dead space (ex: bain, Ayers T-piece)
- w/ smaller rabbits, best to use low-dead space pediatric connectors to attach the ET tube to the breathing circuit
- low dead space T-piece systems for humans are also useful in rabbits
- fresh gas flow rates calc same as for dogs/cats |
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Term
| What is the most reliable method of determining if a small rodent is at an suitable stage of anesthesia for a surgical procedure? |
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Definition
- Assess the pedal withdrawal reflex or tail pinch reflex
- Tail pinch - firmly pinch tip of tail w/ nails hard enough to produce painful stimulus but not hard enough to damage
- If too light for sx, will flick tail and may vocalize
- Tail pinch response usually lost at light to medium planes of anes
- Followed by a loss of the pedal withdrawal response at medium to deep planes of anesthesia
- Most sx can be carried out when pedal withdrawal reflex is absent or barely detectable
- Rabbits/guinea pigs – ear pinch reflex can be used |
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Term
| Why might pulse oximeters not be reliable in small mammals? |
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Definition
| Not designed to fxn normally w/in the range of heart rates (often 250 – 300 bpm) |
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Term
| Why is the position of the eye not used to assess the depth of anesthesia in rodents? |
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Definition
- w/ most anes, position of eye remains fixed in rodents and palpebral (blink) reflex may still be present at sx planes of anes
- rabbits – considerable variation in loss of ocular reflexes, however, at deep planes of anes the eye may rotate and protrude
- because cardiac arrest may occur shortly after rabbit reaches such a deep plane of anes, this appearance indicates that supportive measures be initiated immed and admin of anes reduced/terminated |
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Term
| Know the limitations of using the capillary refill time small mammals to assess perfusion. |
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Definition
- Sm size of rodents usually prevent use of CRT
- May be difficult to assess mm in sm rodents
- Color of mm can give some indication of probs w/ blood loss, cyanosis, and poor peripheral perfusion
- In addition to inspecting the gingival, the color of light reflected in the eyes can be used to detect cyanosis or pallor caused by blood loss in albino animals
- In rabbits both the gingival/conjunctiva can be inspected easily
- Rabbits have normal reddish coloration, CRT <1s |
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Term
| . What would be the blood volume of an adult mouse weighing a given number of grams? |
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Definition
- Total blood vol 70 ml/kg
- 100 g hamster = blood vol of 7ml
- loss of more than 15% can lead to hypovolemic circulatory failure (as with dogs/cats)
- critically important to monitor blood loss by carefully weighing swabs and assessing other loss at the surgical site |
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Term
| Monitoring HR/Rhythm under anesthesia |
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Definition
- Sm size makes difficult
- Not usually poss to palpate peripheral pulse
- Auscultation of chest wall poss in rabbits/guinea pigs
- Esophageal stethoscope can be used in rabbits
- Heart beat can be detected through chest wall in all spp
- May not be poss to accurately assess HR due to high HR (often > 250 bpm)
- ECG often upper limit of 250 – 300 bpm and may also be unable to detect low-amplitude signals generated by rodents |
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Term
| Monitoring Arterial BP under anesthesia |
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Definition
Rabbits
- Rabbits w/ catheter placed in central ear artery
- Or noninvasively w/ an oscillometric technique, place pressure cuff either on forelimb just proximal to elbow or on hindlimb, proximal to stifle, success of this depends on size of rabbit and ability of monitor.
- Alternatively, Doppler probe may be placed over a suitable artery and if probe is combined w/ use of a BP cuff and sphygmomanometer, an estimate of arterial blood pressure can be obtained |
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