Monitoring Patients – Vet Anesthesia – Flashcards
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The ACVA suggests personnel monitoring the animal under anesthesia:
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suggests that the vet, tech, or other responsible party should check the patient's status at least every 5mins during anesthesia and recovery
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The ACVA suggests personnel monitoring the animal under anesthesia MUST have an understanding of:
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a. Normal physiology, and alterations by general anesthesia b. Pathophysiology - When a disease is present
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T/F: continuous monitoring is important
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T: Complications are often not detected until they are advanced and possibly irreversible.
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What is the function of cardiac monitoring?
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ensuring adequate delivery of O2 to tissues and elimination of CO2 generated by tissue metabolism
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Adequate O2 delivery and CO2 disposal is commonly affected by:
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i) Hypotension ii) Arrhythmias iii) Hypoventilation iv) Hypoxemia
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Maintenance of adequate respiratory function entail monitoring and supporting a PaCO2 value of:
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35-45mmHg
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Maintenance of adequate respiratory function entail monitoring and supporting a PaO2 value of:
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> 90mmHg
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Total Ventilation is proportioned and composed of
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Alveolar Ventilation (VA) and Dead Space ventilation (VD)
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What is VA?
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Alveolar Ventilation (VA) - Where gas exchange DOES occur
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What is VD
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Dead Space Ventilation (VD) - Where gas exchange NOT occurring
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How is VD broken up?
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Into anatomic dead space (Vdana) and Alveolar dead space (Vaphys).
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What is anatomic dead space?
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Composed of the conducting airways not participating in gas exchange.
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T/F: the anatomic dead space value is always constant
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True
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What is alveolar dead space?
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Alveoli that are ventilated but not perfused
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T/F: the alveolar dead space value is always constant?
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False: this value is dependent on the number of functioning alveoli
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What is normoventilation
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The drive for alveolar ventilation is an arterial CO2 tension of 35-45mmHg
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When does HoVent occur?
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When the VA fails to match the volume of CO2 produced by the patient: PaCO2 > 45mmHg or ETCO2 > 45mmHg
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When does HrVent occur?
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When the VA exceeds what is made by the patient: PaCO2 < 35mmHG or ETCO2 < 35mmHg
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What are cardiac oscillations?
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Cardiac impulses are transmitted to the capnograph and the oscillations are reverberations resulting from the transmission of cardiac impulses through the airways. Typically seen with deep anesthesia/respiration depression & is an artifact
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What is capnography useful/what does it give a good indication of?
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1. Adequacy of ventilation 2. Characteristic traces for certain situations 3. Assessing ventilator settings 4. Accuracy of intubation (ETT obstruction) 5. Circuit malfunction & disconnection 6. Cardio monitoring - useful during CPR
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Is capnography more useful in SA or LA?
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SA. It's the next best thing to blood-gas
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What is pulse oximetry?
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SpO2: A non-invasive measurement of the percentage of Hgb saturated with O2. The principle of pulse-ox is based on the red and infrared light absorption characteristics of oxygenated and deoxygenated Hgb
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Which absorbs more red light? Oxyhemoglobin or Deoxyhemoglobin?
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Dexoy (660nm) Oxy absorbes more infra-red light
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What is SpO2 Hypoxemia? - KNOW THIS
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95% = PaO2 of 80mmHg
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What is SpO2 in severe hypoxemia?
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90% = PaO2 of 60mmHg
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A shift to the right in the oxyhemoglobin dissociation curve means:
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decreased O2 affinity for Hgb
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When is a shift to the right seen (4 reasons)
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-Increasing temp -Decreasing pH -Increasing PaCO2 -Acidosis
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When is a shift to the left seen (5 reasons)
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-Decreasing temp -Increasing pH -Decreasing PaCO2 -Alkalosis -Fetal Hgb (HbF) - Structurally different from adult Hgb and has a greater affinity for O2
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What is the gold standard method to indicate adequacy of ventilation?
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Blood gas analysis (PaCO2) - Accurate. More values give a larger picture of the entire respiratory/acid-base system.
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What are the advantages of BGA?
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-PaO2 -PaCO2 -pH -Calculated bicarbonate -Base-deficit -SaO2 -Some include electrolytes & lactate
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What are the disadvantages of BGA?
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Invasive, time-consuming, equipment cost and maintenance, single time-point sample
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What is an i-STAT clinical analyzer & what are it's advantages
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a BG machine. It's fast, simple, convenient, versatile, and portable.
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What is measured with inspired & expired gas analysis?
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Concentration of O2, CO2, inhalation agents including N2O. Gives % of gases entering and leaving patient and concentration of gas in breathing system
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Does inspired & expired gas analysis measure PaO2?
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No, only the O2 in the breathing system
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What are rate monitors (Apnea alarms)?
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Thermistor is placed in the patient airway between the Et-tube and the patient airway. As warmed gas passes over the htermistor it is converted to an electrical signal which causes the machine to beep with each expiration. Can be set to alarm if no breath takes place after a set-period
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Why do we care about cardio monitoring?
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adequate blood flow to tissues
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How do you measure CO?
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CO = SV x HR
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What is MAP?
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A product of HR & SV
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What tools are used to measure HR?
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Stethoscope/esophageal stethoscope, pulse-ox, ECG, or Doppler for this
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What are pros of palpation of peripheral pulse rate (PR)?
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Assessment of artery tonicity (dilation vs. constriction) Assess quality of pulse (strong vs. weak, thready, bounding
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What are cons of palpation of peripheral pulse rate (PR)?
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-Not palpable if MAP is <40mmHg, Skin thickness may skew interpretation -Experience may skew interpretation -HoVol animals may have a weak pulse but a normal BP
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Where can you take a peripheral pulse in a K9?
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Femoral Tibial Dorso-Pedal Palmar digital Lingual Caudal arteries
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Where can you take a peripheral pulse in a Fl?
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Femoral Tibial +/- dorso-pedal +/- caudal arteries
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Where can you take a peripheral pulse in a Eq?
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Facial, transverse facial, mandibular facial, nasal, auricular, carotid, femoral, lateral metatarsal, coccygeal, digital arteries
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Where can you take a peripheral pulse in a Ru or Pc?
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Auricular, digital (median)(SmallRU), caudal (Ru) arteries
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What is the mathematical equation for PP (pulse pressure)
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PP = SAP - DAP Therefore, a strong pulse is considered to have a large PP & vice versa
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What is used as a sign of peripheral perfusion?
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Mucous membrane color and CRT
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What is the MOST SENSITIVE method for measuring tissue perfusion?
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Arterial Blood Pressure
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What are the two ways to measure tissue perfusion?
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Non-invasive and invasive
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What are the non-invasive methods for measuring BP?
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Doppler & Oscillometery
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How does a doppler work?
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peizo-electric crystal is placed on an artery with a cuff placed proximally. The cuff is manually inflated above the systolic pressure and then slowly deflated until the sound returns at the systolic pressure
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What considerations need to be taken into account with a doppler?
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Size and placement of cuff. If it's too big or too tight it will underestimate. If it's too small or too loose it will overestimate. Sound disappears w/SAP <40mmHg so be sure to check the patient first if you don't hear sound THEN adjust your instrument
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What is a DINAMAP?
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Device for Indirect Non-Invasive Automated Mean Arterial Pressure - this involves automated inflation of a cuff above the anticipated systolic pressure. Oscillation the start at the SAP, reach a max intensity at the MAP and fade at the DAP
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What does Oscillometry monitor?
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-Measure SAP, MAP, DAP, and PR -Cycle at a predetermined interval -Are reasonable accurate -Non-invasive, low morbidity -As the pulse is what causes the oscillation in the cuff pressure, it becomes unreliable in small, bradycardic, and arrhythmic patients
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What are the invasive ABP methods?
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Aneroid manometer (MAP) Transducer & Oscilloscope (SAP, MAP, DAP, PR)
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What are consequences of invasive ABP methods?
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Hematoma, intra-arterial injection, infection, hemorrhage, and tissue necrosis
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What is a Aneroid manometer (MAP)?
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Simple, only requires, tubing, flush, and the manometer. Is inserted at the level of the righ atrium
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What is a transducer & oscilloscope (SAP, MAP, DAP, PR)
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A bit more complex, but also provides more readings. The apparatus converts the various blood pressures into electrical signals, producing a wave form. This is ideal for critical cases as it gives beat to beat information on the patient
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What is an ECG?
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A non-invasive system that provides information on the electrical function of the heart, NOT blood flow. Therefore, it should NOT be relied upon as the sole monitor for CV function. An example of this would be EMD; which is Pulse-less electrical activity seen AFTER death!
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When using an ECG, what do you have to do before trying to Tx an arrhythmia?
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You need to treat the patient, not the waveforms on a monitor. Check the BP, pulse, MM & CRT before you try to treat an arrhythmia which may not be impacting the patient's hemodynamic function.
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What are the 2 things that must take place for urine output to be used as a cardiac monitor?
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Kidneys must be perfused to produce urine AND MAP must be > 60mmHg making this a relatively sensitive indicator or circulatory state during anesthesia. Not commonly used.
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What is CVP and what does it do?
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Central venous pressure, another less commonly used monitoring tool. It measures the hydrostatic pressure within the thoracic vena cava & gives an indication of venous return, the ability of the heart to pump that venous return, & an indication of volume status
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CVP requires a long or short catheter?
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Long
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What does a high CVP indicate?
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Fluid overload or heart failure
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What does a high CVP indicate?
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Hypovolemia or vasodilation
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What part of the brain governs thermoregulation?
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The hypothalamus
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What are 5 responses to COLD?
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-VC -Non-shivering thermogenesis (i.e., mobilization of brown fat) -Shivering -Piloerection or puffing of feathers -Lowering of body temp<--?
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What are 4 responses to WARM?
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-VD -Sweating -Panting -Salvation
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Why does anesthesia alter temperature ?
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Anesthesia inhibits VC and thermoregulatory mechanisms. As HoThermia slows metabolism and increases O2 consumption it can slow a patient's recovery time markedly
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What are 3 ways to monitor temperature and which is ideal?
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-Rectal thermometer -Esophageal probe (IDEAL - reaches the core) -Nasal, buccal temps (not ideal, too peripheral)
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What temperature defines HoThermia?
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35C or 96F... if a patient drops below this, get active with your warming
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What can you use if your animal gets HoThermia
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-Forced air warming devices - Not ideal during Sx - May contaminate site -Circulating warm water blankets -Fluid warming - Special electrical devices are uncommon & expensive -Electric warmers w/temp control - The HotDog's they use in the clinic -Wrap extremities with insulation -Heat lamps - Be sure to keep a distance to avoid burns -Always check temp when using these or other devices to avoid thermal burns!
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BG is different in:
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neonates, pediatrics, & patients with dz (sepsis). Just use a glucometer.
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HoGly can result in
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-Neuro signs masked by GA -Refractory HoTens -Coma -Prolonged recovery with depression, weakness +/- seizures
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Diabetes should be:
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-Dosed with insulin properly (fasted? when was last dose?) -Monitor accordingly - Use a dedicated arterial catheter -Check BG q/15-60min & have a dextrose drip ready
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What should you do with an animal with an insulinoma?
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-Be prepared to bolus dextrose -Manipulation of the pancreas can cause massive HoGly -BG monitored q/15-60mins & have a dextrose drip ready
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Where do you measure BP in a K9 or Fl?
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Femoral & dorsal pedal
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Where do you measure BP in a Eq?
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Facial and lateral metatarsal
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Where do you measure BP in a Bv?
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Coccygeal and auricular
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Where do you measure BP in an Ov or Cp?
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Auricular or medial metatarsal
