maintaining anesthesia
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
MAINTAINING ANESTHESIA
Involves both vital signs and reflexes
Can be done with or without machines
MONITORING
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
VITAL SIGNS
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)
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
HEART RATE AND RHYTHM
AUSCULTATION
PALPATION
ESOPHAGEAL STETHOSCOPE
OPTIONS FOR CARDIAC MONITORING
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
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
CAPILLARY REFILL TIME
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
MUCOUS MEMBRANE COLOR
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
PULSE STRENGTH
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
EVALUATING BLOOD LOSS
Intra-abdominal blood clot
Intra-abdominal blood pooling
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
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 anestheticdepth. 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
RESPIRATION RATE AND DEPTH
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)
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
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.
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
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
THERMOREGULATION
Fluid line warmer
Self-warming surgery table
Circulating warm waterheating pad
BairHuggers
Excessive efforts to warm a patient could cause thermal injuries.◦ Always place towels between the patient and the
heat source!
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.
THERMOREGULATION
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.
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.
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.
Laryngeal (Swallowing) Reflex
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.
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.
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.
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.