MAINTAINING ANESTHESIA

1. MAINTAINING ANESTHESIA *Information is primarily found in ch. 5 of Your surgery textbook on pgs 139, 140-145, 169-173

2. MONITORING • Involves both _________and __________ • Can be done with or without ___________

3. VITAL SIGNS Variables that indicate the response of the patient’s homeostatic mechanisms to anesthesia and how well the patient is maintaining circulatory and respiratory function during anesthesia VITAL SIGNS INCLUDE: Heart rate, CRT, mucous membrane color, pulse strength, blood pressure, respiration rate, and temperature

4. MONITORING WITHOUT INSTRUMENTATION • YOUR _________, ________, AND ______ ARE YOUR MOST VALUABLE MONITORING TOOLS! • Machines WILL fail! • Only rely on machines to provide you with the values that you cannot determine on your own (______________, _____________, _____________, ___________________, ___________________________)

5. HEART RATE AND RHYTHM under ANESTHESIA • DOGS: 60-150 bpm • REPORT if ________ or ______ bpm in lg dogs ________ or ______ bpm in sm dogs • CATS: 120-180 bpm • REPORT if _______ or _______ bpm • Lower heart rates are commonly observed with anesthesia due to the effects of the anesthetic agents. • Anesthetic drugs can also effect the heart’s rhythm.

6. OPTIONS FOR CARDIAC MONITORING __________________ __________________ _________________________

7. ESOPHAGEAL STETHOSCOPE An esophageal stethoscope is a thin, flexible tube that is attached to a regular stethoscope. Lubrication is applied to the end of the tube which is placed in the oral cavity and down the esophagus until a heartbeat is heard. This allows a person to listen to the heart on an animal that is draped in for a surgical procedure Always assess heart rate/rhythm along with pulse strength, CRT, mucous membrane color, and blood pressure if possible

8. CAPILLARY REFILL TIME • The rate of the return to color for mucous membranes after the application of digital pressure compresses capillaries and blocks blood flow temporarily • Provides information about __________________ • A normal CRT does not necessarily indicate that the patient is normal, however a prolonged CRT (longer than 2 seconds) means that tissue perfusion is not adequate • Possibly due to vasoconstriction, hypotension, hypothermia, heart failure, shock, or excessive anesthetic depth

9. MUCOUS MEMBRANE COLOR • SHOULD BE PINK! • Look at gingiva – most convenient • If gums are pigmented, look at the conjunctiva, or the inner prepuce or vulva • If pale, there may be blood loss, anemia, or poor perfusion • _______________= purple or blue discoloration. EMERGENCY!

10. PULSE STRENGTH • Can be done at the _____________, _________________-, _______________________, and ________________________________ • Should be strong and match the heart beat • Weak pulses may indicate hypotension (low blood pressure) • Causes: excessive anesthetic depth, excessive vasodilation, cardiac insufficiency, excessive blood loss

11. BLOOD LOSS • Can cause complications such as shock • One 3x3 gauze = ______ mL of blood • The actual amount lost may be more due to clotting or pooling of blood • Healthy animal tolerates ~ 13mL/kg blood loss during surgery

12. Intra-abdominal blood clot Intra-abdominal blood pooling

13. RESPIRATION RATE AND DEPTH • Can be evaluated by watching the _________ ______________ or ____________________ • Normal values while under anesthesia: ________ bpm • ____________________ (volume of air inhaled) decreases with the anesthetic depth • Shallow breaths can cause the lung on the down side of the body to collapse (atelectasis)

14. RESPIRATION RATE AND DEPTH Bagging the patient • Performed when assisted ventilation is necessary to _____________________________________ , or to _______________________________ • Closing of the pop off valve and gently squeezing of the reservoir bag causing the patient’s chest to fill with oxygen/anesthetic gas

15. HYPERVENTILATION and tachypnea • HYPERVENTILATION: Increase in respiratory depth • (tachypnea = increase in respiratory rate) • Causes of hyperventilation and tachypnea • Body’s response to increased CO2 in the blood • Underlying pulmonary disease • Surgical stimulation • Decrease in anesthetic depth • Patient is too “light” or waking up

16. RESPIRATORY RATE AND DEPTH CONTINUED… • Normal breaths are smooth and regular, not gasping or labored • DO NOT FORGET TO USE YOUR STETHOSCOPE TO EVALUATE BREATH SOUNDS! • Should not hear crackles or wheezes

17. THERMOREGULATION ______________ is the most common anesthetic problem and has many ways to be prevented or corrected Prevent from the moment the animal is induced. • The greatest decrease is within the first 20 minutes.

18. The following can decrease body temperature: Check the patient’s temperature at least every 15-30 minutes if there is not an esophageal or rectal probe available to do continous monitoring. In between temp measurements, feel the animal’s extremities.

19. Several methods to avoid hypothermia:

20. Circulating warm water heating pad Fluid line warmer Self-warming surgery table

21. Bair Huggers

22. ALWAYS PLACE A TOWEL OVER HEAT SOURCES TO PREVENT BURNS!!!!!! Do not place animal directly onto stainless steel table or heating pads! Also monitor for hyperthermia (especially post-operatively) which can happen with some anesthetic agents (opiods, ketamine).

23. HEATING PAD BURNS

24. REFLEXES Involuntary response to a stimulus Indicate depth of anesthesia, but no info on homeostatic mechanisms Most commonly used: palpebral, pupillary light response, swallowing, pedal (withdrawal), ear flick, laryngeal

25. _________________ Reflex Touch the corner of the eye and the animal blinks. This reflex is stimulated by tapping the skin at the medial or lateral canthus of the eye or by running the finger along the eyelashes. This reflex is gradually lost as anesthetic depth increases.

26. __________________________ Reflex Immediate closure of the epiglottis and vocal cords when the larynx is touched by any object. Stimulation of the larynx will cause the animal to swallow. The stimulation may be from outside, for example, an attempt to pass an endotracheal tube or may be internal for example the presence of secretions at the larynx. This is a mechanism to prevent accidental aspiration of fluids into the lungs.

27. ____________________ Reflex Pull a limb gently, pinch the toe and the animal will pull back the limb. The reflex is obtained by firm pressure of the interdigital skin in the dog and cat *particularly important in animals undergoing mask inductions

28. ______________________ Reflex Shine a light in the eye and the pupil constricts. The pupillary responses under anesthesia are heavily influenced by pre-medication. Species variations exist. There is also variability in response to different anesthetics. In general, in un-premedicated patients, the pupil is dilated in the early excitement phase and then becomes progressively constricted as surgical anesthesia occurs. With very deep surgical anesthesia the pupil begins to dilate again and with entry into stage IV, with respiratory and cardiac arrest, the pupil is maximally dilated.

29. _________________ Reflex Touch the cornea and the animal blinks. Be careful not to damage the cornea if this reflex is tested. This reflex is obtained by gentle palpation of the lateral aspect of the cornea. This causes reflex closure of the eyelids. This reflex is not always reliable in the dog, particularly if the eyeball is markedly rotated.

30. _____________________ REFLEX Pinnal reflex used in cats. Gently touch the hair on the inner surface of the ear and watch the pinna twitch. Don’t test too frequently or the reflex will be inaccurately lost.