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MAINTAINING ANESTHESIA

MAINTAINING ANESTHESIA. MONITORING. Involves both vital signs and reflexes Can be done with or without machines. VITAL SIGNS. Tell us how well a patient is maintaining homeostasis through respiration & circulation

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MAINTAINING ANESTHESIA

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  1. MAINTAINING ANESTHESIA

  2. MONITORING • Involves both vital signs and reflexes • Can be done with or without machines

  3. VITAL SIGNS • Tell us how well a patient is maintaining homeostasis through respiration & circulation • Often grouped according to whether they reflect circulation, oxygenation, or ventilation • For example, values that reflect circulation are: HR, heart rhythm, pulse strength, CRT, mucous membrane color, and blood pressure • Values that reflect oxygenation are:mucous membrane color, hemoglobin saturation, measurement of arterial blood oxygen • Values that reflect ventilation are:RR, respiratory depth, breath sounds, expired CO2 levels, measurement of arterial CO2

  4. MONITORING WITHOUT INSTRUMENTATION THE MOST IMPORTANT MONITORING TOOLS ARE YOUR HANDS, EYES, & EARS! MACHINES WILL FAIL! ONLY RELY ON MACHINES FOR VALUES THAT YOU CANNOT GET ON YOUR OWN(blood pressure, ECG, SPO2)

  5. HEART RATE AND RHYTHM • Anesthetic agents are expected to lower the heart rates of patients • While under anesthesia, the following heart rates are appropriate for dog: • Large dogs: 60 - 140 beats per minute • Small dogs: 70-160 beats per minute • Notify the vet if heart rates are outside these ranges • While under anesthesia, the following heart rates are appropriate for cats: • 100-180 beats per minute

  6. OPTIONS FOR CARDIAC MONITORING AUSCULTATION PALPATION ESOPHAGEAL STETHOSCOPE

  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

  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 tissue perfusion • A normal CRT does not guarantee 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 increased anesthetic depth

  9. MUCOUS MEMBRANE COLOR • IDEALLY, COLOR SHOULD BE PINK! • 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 • CYANOSIS = purple or blue discoloration= EMERGENCY! • ICTERUS=yellow discoloration, may indicate severe liver disease or hemolysis

  10. PULSE STRENGTH • Can be done at the lingual, femoral, metacarpal/metatarsal, and dorsal pedal arteries • Should be strong and match the heart beat • Weak pulses may indicate hypotension Causes: excessive anesthetic depth, cardiac insufficiency, excessive blood loss

  11. EVALUATING BLOOD LOSS • Excessive blood loss can cause complications such as shock • One soaked3x3 gauze = ~5-6 mL of blood • One soaked 4x4 gauze= ~10mL blood • The actual amount lost may be more due to clotting or pooling of blood • Healthy animal can tolerate ~ 13mL/kg blood loss during surgery

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

  13. RESPIRATION RATE AND DEPTH • Anesthetic agents are expected to reduce the tidal volume, which is the amount of air inhaled with each breath. • Can be evaluated by watching the patient’s chest or the reservoir bag on the anesthetic machine • Normal values while under anesthesia for dogs & cats: 8-20 bpm

  14. RESPIRATION RATE AND DEPTH • Bagging the patient refers to the process of manual ventilation. • Gentle squeezing of the reservoir bag causes oxygen/anesthetic gas to be forced into the patient’s lungs • Can be used to increase anesthetic depth. If an animal is waking up, manually forcing anesthetic gas into the lungs will cause it to fall asleep more rapidly • Can be to increase respiratory rate. If the respiratory rate is low, we can provide manual breaths ~q20 seconds to increase the rate • To reverse atelectasis. Atelectasis refers to the collapse of alveoli

  15. RESPIRATORY RATE & DEPTH • Hyperventilation=Increase in respiratory depth • Tachypnea = increase in respiratory rate • Causes of hyperventilation and tachypnea: • Increased CO2 in the blood • Underlying pulmonary disease • Surgical stimulation • Decrease in anesthetic depth (animal is too light)

  16. RESPIRATORY RATE AND DEPTH • 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 • Hypothermia is the most common anesthetic problem • Begin prevention from the moment the animal is induced. • The greatest decrease in body temperature is within the first 20 minutes of anesthesia.

  18. THERMOREGULATION • The following can decrease body temperature: • Shave and scrub of the surgical area • Inability of the animal to shiver to create body heat • Decreased metabolic rate • Exposure of the internal organs to the air • Anesthetic agents that cause vasodilation, and increase the rate of heat loss • Pediatric and geriatric animals • Room temperature • Check the patient’s temperature at least every 30 minutes if there is not an esophageal probe available. In between temp checks, feel the animal’s extremities

  19. THERMOREGULATION • Several methods to avoid hypothermia: • Circulating warm water heating pad. Electric heating pads may cause more burns. For all heating pads, put a towel between the heating pad and the patient • IV fluid line warmer • Hot water bags/rice socks • Saran wrap/bubble wrap • Bair hugger • Warm towels • Heated surgery table • Baby booties on the paws

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

  21. Bair Huggers

  22. THERMOREGULATION • Excessive efforts to warm a patient could cause thermal injuries. • Always place towels between the patient and the heat source!

  23. THERMOREGULATION • Some patients, usually cats, will become hyperthermic post-operatively. This is due to the effects of some drugs such as ketamine and opioids. • If the temp reaches 103.5˚ or higher, we should begin cooling methods. • Taking all blankets/towels out of the cage • Putting a fan in front of the cage • Wiping the patient down with a wet washcloth • Applying alcohol to the footpads.

  24. REFLEXES Reflexes are involuntary reactions to a stimulus It is also important to monitor reflexes, which will help you determine the stages and planes of anesthesia.

  25. Palpebral Reflex Touch the corner of the eyelids and the animal blinks. The palpebral reflex is stimulated by tapping the skin at the medial canthus of the eye or by running the finger along the eyelashes. This disappears in light to medium plane of surgical anesthesia in small animals.

  26. Laryngeal (Swallowing) Reflex • Simulation of the larynx will cause the animal to swallow. This is a mechanism to prevent accidental aspiration of fluids into the lungs. • passing an endotracheal tube • presence of secretions at the larynx.

  27. Withdrawal 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, squeezing the claws together in cattle and swine and firm pressure on the pastern of horses. The reflex disappears late in phase III and indicates deep anesthesia. When checking the reflex, the legs should be held in extension. Probably more useful in monitoring laboratory animal patients and birds.

  28. Pupillary 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 phase IV, with respiratory and cardiac arrest, the pupil is maximally dilated.

  29. Corneal Reflex Touch the cornea and the animal blinks. Be careful not to damage the cornea if this reflex is tested. The corneal reflex is obtained by gentle palpation of the lateral aspect of the cornea. This causes reflex closure of the eyelids. The reflex disappears in the deeper levels of phase III, plane II. This reflex is not always reliable in the dog, particularly if the eyeball is markedly rotated.

  30. EAR FLICK 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.

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