Monitoring Circulation: Anesthesia Lecture | ECG | Veterinary PDF

Anesthesia 2 -- Lecture 4 **Vital Signs Grouping** Circulation = HR & Rhythm, pulse strength, CRT, MM, BP & Cardiac sounds & impulses/conduction Oxygenation = MM, CRT, Hemoglobin Saturation, Inspired Oxygen, Arterial Blood Oxygen Ventilation = Resp rate and depth, breath sounds, end expired C02,...

Anesthesia 2 -- Lecture 4 **Vital Signs Grouping** Circulation = HR & Rhythm, pulse strength, CRT, MM, BP & Cardiac sounds & impulses/conduction Oxygenation = MM, CRT, Hemoglobin Saturation, Inspired Oxygen, Arterial Blood Oxygen Ventilation = Resp rate and depth, breath sounds, end expired C02, arterial C02 levels, blood pH **Instruments Used to Monitor Circulation Heart Rate & Rhythm** - Esophageal Stethoscope - Electrocardiography (ECG) - CRT/MM - Peripheral Pulse & Pulse Quality - Heart Rate - Echocardiography (ultrasound of the heart) **Cardiac Auscultation** - Listen to left, right & sternal, as well as throat - Watch breathing to distinguish sounds - Palpate pulse while listening - Then listen for at least a minute for abnormal sounds - HR will be more difficult to hear on anesthetized patients - Be patient - Locate apical pulse to find loudest sounds (5^th^/6^th^ ribs) - Due to reduced cardiac contraction strength Heart Rhythm - Should be assessed along with heart rate - Arrythmias occur commonly in anesthetized animals & vary in significance from innocuous to life threatening. Therefore the anesthetist must assess the patient's heart rhythm at many points during any anesthetic procedure to keep the patient safe **Cause of Arrythmias** - Hypoxemia - Hypercapnia - Hypotension - Hypo/Hyperthermia - Electrolyte abnormalities (potassium & magnesium) - Oculo-cardiac reflex - Diseases states or conditions - Drugs/Inadequate anesthesia / analgesia **Common Cardiovascular Circulation** - Cardiac arrythmias - Cardiac murmurs - Hypotension - Hemorrhage - Hypoxemia - Respiratory arrest - Cardiac arrest **A&P Review** Impulses flow from base to apex of hearts anatomy (SA to Purkinje Fibers) Resting heart cel state is a negatively charged cell on the inside -- this is called "polarized" and is impermeable to the + ions around it Electrical impulses are generated by automaticity of specialized cardiac cells But when the heart cell gets a zap of electricity it changes to permeable and allows + ions in - Na rushed into the cell, which causes cell to know have + cells inside AND with + cells on the outside this causes contraction because it is less negative -- called depolarization -- firing of the cell After contraction I relaxation; this is where the cells go back to their negative state This is called repolarization when cell returns to negatively charged state - Occurs when cell is more permeable to K ions leaving the cell causing it to be negatively charged again, leading to muscle relaxation The cell cant fire (depolarize/contract) until the cell is in its resting state - This is called the refractory period If the animal had a shortened refractory period the heart muscle could continuously fire - Called fibrillation -- an arrythmia It is this depolarization and repolarization process that creates the electrical activity of the heart, which can be represented as the PQRST waveform on an ECG **ECG**  Diagram of a heart with a diagram Description automatically generated What is Electrocardiography - A diagnostic test that records electrical activity about the heart rhythm in real time - In animals, electrodes may be attached to the limbs, thorax, and/or other areas (neck, abdominal flanks) to pick up electrical impulses produced by a beating heart - Cardiac electrical impulses (action potentials) originating from the SA node are recorded as voltage (amplitude y-axis) against time x-axis (speed/duration) - Produces P QRS T waveform, one heart beat = 1 ventricular contraction - ECG trace (graph) with Heart Rate is calculated number based on highest point of complexes (therefore artifact or irregular rate or irregular rate or rhythm can affect an accurate ECG HR calculation) - ECG's can read up to 12 leads, ECG is reading the heart as a 2D structure (instead of 3D) from 12 different angles - Think of each of the 12 leads as different views of the heart For anesthesia purposes we use 3 limb lead set up called Einthoven's Triangle   One lead is made from the communication of 2 electrodes Lead 1 -compares RL to LA Lead 2 compares RA -- LL - What we set monitor to read (lead 2) - Yields largest complex on the screen, reps most natural conduction through heart Small animals have "Type A" Conduction where current flows from base to apex Electrodes placed from various angles to "capture" the electrical sign (& strength) Use lead II in small animals because the electrodes are far apart & yields the tallest R wave  A diagram of a dog with wires attached to its body Description automatically generated  Lead Placement -- White on Right & Smoke over Fire **Clip Types** - Crocodile Clips (Atraumatic) -- requires gel or alcohol - Alligator clips can cause skin trauma if left on too long -- requires gel or alcohol - Red dot stickers with snap clips - For very small patients, needles places SQ can be used with clips attached **ECG Settings** - Find the menu or settings on your ECG module and adjust to ensure graph is large but not too large it is off the screen - Set to Lead II - Ok to change leads to look at different views for troubleshooting **Tech Tips** - Lear how to obtain the best ECG under normal conditions - Aim for a steady baseline, artifact free, & print worth tracing that can be interpreted (breathing & movement most common artifacts) - Know your machine & ECG settings - Ground your equipment to reduce interference - Ensure wires are not twisted, bent or touching other electrical equipment - Ensure all connections are tight on each electrode and cord - Coil cords loosely, keep dry and clean - Know limitations oof an ECG **ECG Rhythm** Know what a normal P QRS T Complex looks like, troubleshoot lead placement, machine settings, and alert RVT/DVM if needed - Can be complex - Keep simple until you have a good foundation For anesthesia monitoring patient body position does not matter, electrode placement & leads matter Electrodes must contact skin and use ECG gel, saline or alcohol - Must have for red dots or place them on a paw pad - Patient must be in right lateral for diagnostic ECG's with electrodes not touching or intertwined   P Wave = Atrial muscles depolarizing = atrial contractions QRS = ventricular muscles depolarizing = ventricular contractions T Wave = ventricular muscle repolarization = ventricles relaxing & refilling Atrial repolarization occurs but hidden in QRS complex Sinus Arrhythmia  A graph with a line on it Description automatically generated Sinus Tachycardia -- abnormally fast HR, inadequate depth, drug reactions or surgical stimulation. Treat according to cause Tachycardia cause -- anticholinergic and cycloheximides, inadequate anesthetic depth, pain, hypotension, blood loss & shock, low 02 or high C02