Exam 1 - Anesthesia Notes PDF

Analgesia ★​ Goal: alleviate the pain in your patients, understand pain and the pain pathway ○​ Where do we block pain? What will happen when we do not manage pain properly? ○​ “Friends don’t let friends hurt.” You are your patient's advocate, be their v...

Analgesia ★​ Goal: alleviate the pain in your patients, understand pain and the pain pathway ○​ Where do we block pain? What will happen when we do not manage pain properly? ○​ “Friends don’t let friends hurt.” You are your patient's advocate, be their voice. ★​ Pain = an unpleasant sensory or emotional experience associated with an actual or potential tissue damage ○​ The body has been built to recognize and to avoid pain (ex. the hot burner) ○​ Anxiety and emotions will add to the pain pathway - neurotransmitters associated with emotions will play a role in the pain pathway, elevating or diminishing such ★​ Analgesia = the absence of awareness of pain (without a loss of consciousness) through the usage of drugs or other modalities ○​ General anesthesia - they are unconscious and unaware of their pain but analgesia is not provided ★​ Analgesia vs. Anesthesia ○​ Analgesia is pain relief without loss of consciousness, while anesthesia is the loss of physical sensation, with loss of consciousness. ★​ Chronic vs. Acute Pain ○​ It can be difficult to define - ie. hard to determine when it changes between the two ★​ Acute Pain - adaptive pain: the protection mode of pain, protects the animal and promotes healing after an injury ○​ Sx injury with proper management without long term pain ★​ Chronic pain - maladaptive pain: not managed properly, great and ongoing pain even when the area of injury has been healed  ○​ Diseased state - the nervous system has already made changes due to an amplified stimulus, the pain will amplify and continue even when the injury has been healed ★​ Managing Acute or Chronic Pain ○​ Needs to be different - the adaptive phase is very important for management (prevention) ○​ Acute - has a normal and healthy nervous system vs. Chronic - abnormal and “diseased” nervous system ○​ Physiology makes management more difficult ​ Nerves have developed an increased sensitivity, new multiple pain receptors have developed, and there are silent nociceptors (pain receptor) that have woken up and behind sending messages ★​ Recognizing: an animal in maladaptive pain ‘ ○​ Normal pain response: receiving a stimulus multiple times onto the skin, there is not pain at the beginning but as the pressure increased gradually, it will then begin to hurt ie. with stimulus intensity, the pain intensity should increase at a gradual rate ★​ Hyperalgesia: prolonged bombardment of receptors that results in a windup or amplification of signals (surgical pain, chronic pain, long-term pain) ○​ receiving a stimulus is multiple times more painful than normal in a short amount of time - it takes less stimulus to reach level 10 pain intensity than it does with a normal nervous system ○​ The animal has received a previous injury and has developed an abnormal pain response to intensity ★​ Allodynia: a stimulus that was previously non-painful, has not become extremely painful for an animal within a maladaptive state  ○​ Example: simply petting the animal now causes a pain response ★​ Overall: what can we do to prevent this? ○​ Medication, more intense pain control ★​ Wind-up = an amplification of signals that leads to allodynia and hyperalgesia ○​ Peripheral = changes in the nociceptors ​ The threshold for triggering a depolarization wave will take less stimulus to reach the threshold ​ Individual nociceptors are more sensitive to sending a pain signal ​ Silent nociceptors are awoken ​ ○​ Centrally - spinal cord ​ Changes in neurotransmitters ​ When the nerve impulse enters the spinal cord from the periphery, it will synapse to the brain/brainstem - the receiving of this information from the periphery enters/passes the NMDA receptor, the neurotransmitter that passes through this receptor is known as glutamate (excitatory NT) - it increases the NMDA stimulation and  therefore increases the number of pathways coming from the one peripheral nerve up to the brain (the stimulus and signals are increased to the brain) ★​ Changes seen with maladaptive pain: ○​ The changes occur in the tissue level as well as within the spinal cord level ○​ Managing maladaptive pain - we need to work within the tissue level BUT also preventing wind-up via the NMDA receptor (ie. drugs like ketamine) ​ Diminishing wind up in the goal ​ Tissue trauma, peripheral nociceptors (pick up signal, reach threshold) , through peripheral nerve, into the reflex arc via the dorsal root ganglion, connects through the neurons, to brain/brain stem, into thalamus, into cerebral cortex ★​ Medications are used to treat or to prevent maladaptive changes ○​ Multiple drugs at different locations to block the windup ★​ Adaptive Pain - nociceptive vs. inflammatory pain ○​ Nociceptors has multiple different sensations and functions - there are thresholds ​ These detect noxious stimulus ​ Heat, ischemia (blood loss), distension (bladder distension), mechanical (surgical pain) ○​ Chemical receptors ie. inflammatory pain! ​ Pain associated with inflammation ★​ Maladaptive Pain Recap: also known as neuropathic or functional pain ○​ Serves NO physiological purpose or protective purpose (not apart of the healing process) ○​ Intense nociceptive barrage ○​ Occurs due to a severe nerve injury (dewclaws, amputations) or from abnormal sensory processing ○​ Pain perception with NO evidence or tissue damage (it has been healed and the pain is still felt) ★​ Types of sensory neurons  ○​ A-beta fibers + A-delta fibers ​ Large, myelinated ​ Light touch and vibration ​ FAST TRACKS - easily localizable ​ Somatic pain: body, bone, skin, muscle, tendons, ligaments = higher level of a-fibers ○​ C-fibers ​ Unmyelinated, mechanical thermal and chemical ​ Not easily localized ​ Dull, slow, throbbing pain that comes in later ​ Visceral pain: organ, GI pain, abdominal = more c-fibers ★​ Why treat pain? ○​ Animals lack the skills to explain their pain ○​ General anesthesia LACKS analgesia ○​ Rapid recovery from gas means that the paraesthesias have worn off ○​ Give presumptive pain management ○​ Opioids can stimulate more nociceptors ★​ Pain MYTHS ○​ We cannot measure pain from non-verbal patients ○​ Pain does not exist if we cannot see tissue damage ○​ The same stimulus produces the same degree of pain in all individuals ○​ Don't start analgesia until the pain is already existing ○​ Aggressive pain management means only opioids ○​ Animals should feel pain to not overdo it during recovery ★​ Pain will result in poor recovery ○​ Pain triggers the sympathetic nervous system ○​ Pain -> glucocorticoid/catecholamine -> SNS stimulation which leads to… ​ Fear, anxiety due to anticipating the pain ​ Increased HR and BP, arrhythmias, pale MM ie. vasoconstriction ​ Increased infection risk ​ Slower wound healing ★​ What does pain appear like to you? Recognizing pain ○​ Helps to matching the protocol to the type of pain in the patient ★​ Pain signs: ○​ Abnormal behavior ○​ Restlessness ○​ Aggression (be careful) ○​ Unwillingness to move ○​ Abnormal posture (laying in funny way) ○​ Facial expression (grimacing) ○​ Insomnia, depression ○​ Licking the area ★​ Cat Pain Score / Signs / Indications ○​ Generally silent, may growl or hiss, purring ○​ Stiff and hunched in sternal recumbency, limbs tucked underneath the body ○​ Reluctant to move limb(s) or carry limb(s) ○​ Reclusive, seeks solitude ○​ Hair coat is rough or fluffed up ○​ Decreased appetite - not interested in food ★​ Dog Pain Score / Signs / Indications ○​ Whimpers, howls, growls ○​ Cowers, crouches, recumbent ○​ Reluctant to move, awkward, shuffles ○​ Can be subdued or vicious, quiet or restless ○​ Unwilling to move any part of the body ○​ No eager to interact with what is going on ○​ Droopy ears or worried facial expression ★​ Degree of pain ○​ Based off of: visual signs and palpation ○​ Observe the patient, repeated evaluation is needed ○​ If it looks like it hurts, it definitely does. (highest degree of pain = anytime you’re cutting into nerves) ★​ We must be good at looking for a painful animal with physical clues ○​ HR, RR ○​ Pale mm ○​ Increased BP (vasoconstriction on non-essentials) ○​ Premature ventricular contractions ○​ Pain on palpation along an incision site  ○​ Sedatives can mask the pain symptoms Preanesthetic Assessments ★​ Patient Assessment ○​ Gathering information ★​ Why is this important? ○​ We are challenging their natural physiology - we need to ensure that their body is prepared to handle what we are going to give ○​ How risky do we think anesthesia is? ★​ Signalment, Chief complaint, Hx ○​ Signalment = sex, repro status, age, breed, weight ​ Lots of breed differences with pain management and anesthesia (brachycephalics) ​ Behavior? Chill or flighty? ○​ Previous illnesses, Ill in the past 24 hours? ○​ Any current issues? (kidney, heart, respiratory) ○​ Meds? Allergies to meds? ○​ C/S/V/D ○​ Tolerating exercise? (cardiovascular and respiratory problems) ○​ Vaccines current? (hopefully 2 weeks before) ○​ Sx or Dx that will be performed ○​ Any previous anesthesia & how they did ○​ LOC - calm, hyperactive ○​ Weight - BCS (when we calculate, we are basing it on their lean body mass) ★​ Physical Exams (doctors will perform the physical exam in most clinics) - always have a baseline ○​ Cardiovascular - normal hearts are necessary for smooth and easy anesthesia ​ Hx and PE clues for cardiovascular problems ​ Not having endurance - exercise intolerance, weakness ​ Coughing, changes in breathing - dry, hacking ​ Abnormal heartbeat - heart murmur, arrhythmia (can be nervous, but should normalize) ​ Weak pulse, pulse deficits, prolonged CRT >3 (most significant physical finding for perfusion and BP) ​ Dx tests or pre-tests ​ BP (hypotensive, pulse deficits) ​ EKG ​ Chest x-ray ​ Echocardiogram ​ Anesthetic concerns: ​ The heart workload is going to change - we compromise the cardiovascular system, if the patient is already compromised they cannot tolerate worsening of their system ​ Increased sympathetic tone (flight system) ​ Arrhythmias, BP issues, preload of the heart, vasoconstriction/dilation ​ Fluids - when we pump more fluids into the body, we cause more stress on the heart as it needs to pump more fluids ○​ Respiratory - works together with cardio. - we suppress and challenge the respiratory system ​ Hx & PE ​ Oxygenation issues ​ Coughing (dry hacking vs. moist), sneezing, wheezing, snoring (changes in resp.) ​ Out of breath after exercise ​ Observe the breathing - labored breaking, cough, sneeze, wheeze, stridor (increased sound), tachypnic, MM color (red - CO2 problem, perfusion) ​ Open mouth breathing - cats ​ Clear nasal or ocular discharge? (can experience pulmonary edema) ​ Respiratory distress ​ Brachycephalic? ​ Dx tests or pre op tests ​ Chest x ray ​ Pulse OX (cannot handle movement, hard when they are awake) ​ Oxygen trial - p[ut them on oxygen for a while ​ Supplemental oxygen ​ Anesthetic concerns - drugs we give cause resp. depression ​ Gas exchange issues, assistance with ventilation, hypo-hyperventilation can affect O2 CO2 levels, monitor the pulse ox, capnograph, blood gases ​ Use machines that measure ventilation ○​ Genitourinary - combing system of repro with urinary ​ (Repro not super important) ​ Urinary = kidneys and urine prod. ​ Hx & PE ​ Intact? Last heat? Bred? (can bleed under anesthesia in estrus, diestrus is prone to pyometra, pregnant/last time bred) ​ Changes in urination? “Are they urinating?” ​ Inappropriate urination/elimination? ○​ Underlying UTI (undiagnosed infections can affect animals health) ​ Both testicles? (intact males metabolize drugs differently), confirm the sex! Swelling, discharge? Cryptorchid? ​ Bladder palpation - blocked, rock hard bladder, we need to allow them to void before procedure, also painful for the animal - express bladder or void sample ​ HR - bradycardic cat with rock hard bladder? = urinary obstruction, potassium levels becoming high and dangerously high (need to clear their potassium levels) repolarization phase, the electrical impulse becomes hyperpolarize making it harder to trigger depolarization phase ​ Dx tests or pre op tests ​ Electrolytes - sodium and potassium ​ U/A - SG for underlying kidney dz ○​ Prerenal azotemia and postrenal azotemia ​ Vaginal smear - where are they in their heat? ​ EKG is blocked (bradycardia) ​ Xray  ​ U/S ​ BP - kidneys cannot handle BP lower than their normals ​ Anesthetic concerns ​ Monitor the urine prod. If they cannot urinate, watch their preload ​ Excretion of drugs - avoiding drugs cleared through the urinary system ​ Hypotension - causes the kidneys to not work as well, kills nephrons ○​ Nervous - normal function brain, stem, spinal cord ​ Hx and PE ​ LOC (level of consciousness) changes - mentation ○​ BAR ○​ QAR ○​ Lethargic/depressed ○​ Obtunded - aware via vocal stimulation ○​ Stuporous - aware via physical stimulation ○​ Comatose - out of it completely ​ Neuro exam - ocular, basic reflexed, pupils active on each side, ○​ PLR - pupillary light response ○​ Anisocoria - one pupil larger than another ​ Changes in resp., brain stem is the trigger for when we breath ​ Altered BP, HR - intracranial pressure changes (bodies reflex is to decrease HR when there is pressure) ​ Dx tests or pre op tests ​ Baseline neuro eczema  ​ BP ​ Xray, CT. MRI ​ Anesthetic concerns ​ Fluids - too much or too little can affect BP and intracranial pressure ​ BP - intracranial pressure ​ Ventilation ○​ Musculoskeletal - under medications to manage the pain or under chronic pain, altering our pain management ​ Hx and PE ​ Slow to rise, favoring one limb, crying when picked up ​ What meds? OTC? ​ Hunched, stiff ​ Dx tests or pre op tests ​ Xray ​ Orthopedic exam ​ Anesthetic concerns ​ What drugs are they already on ​ How can we manage their pain? ​ How can we poston them to allow them less pain and normal function ○​ Integumentary System ​ Sx to remove tumor - mast cell tumor - do not touch the tumor, scrub around the tumor which will release histamine and cause anaphylactic reactions and decrease in BP ​ Maybe administer antihistamines before sx  ○​ Digestion ​ Hx and PE ​ V/D/ constipation? ​ Changes in stool? ​ Appetite? ​ Good oral exam ​ Abdominal exam ​ Check for signs of dehydration ​ Abdominal palpation ​ Dx tests ​ Blood work (PCV, TP, BUN, lytes) ​ Xray ​ Fecal ​ Anesthetic concerns ​ Dehydration, low proteins (lower drug binding/metabolism) , regurgitation, aspiration risk ★​ Minimal Database Testing ★​ PCV - more than 20% - not in need of a transfusion  ○​ Less then 20% - more than likely in need of a transfusion before anesthesia ​ RBC mass is measured (these carry oxygen, less than a certain amount we are not getting a good amount of oxygen to our tissues) ★​ TP normal 5 - 6 ½ ○​ Needs to be above 3.5 g/dL, below they need plasma ○​ They need proteins to carry drugs, this changes our drug binding ★​ Albumin is the main colloid pull that keeps fluids in the bloodstream ○​ Needs to be above 2.0 maintains the oncotic pressure ○​ Needs transfusion ○​ More fluid is leaving the capillary bed ★​ SQ urine ○​ Appropriate for the hydration status, dehydrated = concentrated urine ★​ CBC ★​ BUN (blood urea nitrogen) ★​ ALT (alanine transferase) hepatic enzyme inside the liver cell, needs borken liver cells to be released ○​ Gives you idea of liver function, the liver has drugs so its important to understand the function of liver due to it filtering/clearing drugs ★​ SG and full U/A ★​ Additional Tests ○​ Clotting times - can they clot their blood? ​ BMBT = buccal mucosal bleeding times