Anesthesia & Surgical Assisting Part 1 PDF

Anesthesia & Surgical Assisting Part 1 WEEK 11  Preoperative evaluation → gathers enough information to Preoperative minimize the life-threatening risk of anesthesia & surgery Considerations Patient characteristics...

Anesthesia & Surgical Assisting Part 1 WEEK 11  Preoperative evaluation → gathers enough information to Preoperative minimize the life-threatening risk of anesthesia & surgery Considerations Patient characteristics Patient history Physical examination Laboratory tests Most important step because all anesthetic decisions are based on health status Any abnormalities found should be pursued to determine their potential effect on anesthetic outcome 2 Preoperative Considerations Lab tests: (the selection will Patient characteristics: Patient medial history: Physical exam: depend on the age of animal) Species Signalment Genearal body condition score PCV/TS Breed Vaccine status Evaluation of each body Liver enzymes Age Medical & surgical history system Bile acids Gender Injuries BUN/Cr Diseases Glucose Past anesthetic complications Electrolytes Changes in the patient’s Blood smear condition since last observed Heartworm status Purpose of the appointment Fecal analysis Observance of fasting Urinalysis recommendations Blood coagulation screen Concurrent medications +/- chest rads +/- ECG 3  Varies depending on the procedure Standard practice = withhold food for 8-12 Patient Preparation hours (the night before) & water 2-4 hours (the morning of) prior to anesthesia Pediatric or smaller patients should be fasted for a shorter period of time Chronically compromised patients should be stabilized, if possible, before anesthesia Anemic patients should have a transfusion Dehydrated patients should have IV fluids Patients with low TS should have plasma Obtain an accurate weight Place IVC 4  Preanesthesia Checklist Personnel Materials for securing catheter (tape) 1. Select personnel & identify roles Saline flush or heparinized saline in syringe with 2. Review procedure needle 3. Review emergency procedures Fluid delivery sets Patient Endotracheal Intubation 1. Identify patient properly 1. Select and inspect 3 sizes of ET tubes 2. Verify patient was fasted 2. Gather necessary equipment: 3. Weigh patient Lubricating gel 4. Perform special prep as needed Rolled gauze for securing 5. Perform preanesthetic examination Laryngoscope and appropriate blades Stylets Drugs Lidocaine spray or swab if needed 1. Select drugs; confirm they are available 2. Review routes of drug administration Equipment 3. Check crash cart inventory 1. Review anesthetic machine checklist 2. Select and inspect monitoring equipment Fluid Administration 1. Select IV fluids; maintain at proper temperature Miscellaneous Supplies 2. Confirm sufficient fluids available for adverse events 1. Ophthalmic ointment 3. Gather necessary equipment: 2. Circulating warm water blanket, table insulation or Y shaped IV catheters heated table Injection caps 3. Face mask 5  Checklist for Daily Inspection of Anesthetic Equipment Sufficient oxygen available – check cylinder pressure Flowmeter bobbin or float moves freely through Anesthesia Equipment & length of tube Unidirectional valves properly functioning Supplies Vaporizer filled & filler caps tightened All gas lines correctly connected Sufficient & fresh CO2 absorbent time available Scavenging system properly connected & All equipment should be prepared and checked operational Cuff syringe available to be in working order before administration of Attach breathing circuit, tubes, and reservoir bag Check for leaks: anesthetics 1. Close pop-off vale 2. Occlude patient end of breathing circuit Use a preanesthetic checklist for inspection (where ET tube attaches) 3. Fill circuit with oxygen to a pressure of 20 cm H2O 4. Turn on oxygen flow to 100 mL/min 5. If pressure increases, leaks are within acceptable limits 6. If pressure drops, increase the flow rate until pressure remains stable 7. Leaks exceeding 200 mL/min must be corrected via machine maintenance 8. Open the pop-off valve while occluding the Y piece; pressure should drop to 0 cm H2O 6 Supplies for IV Fluids Placement of an IVC is essential for patient safety during anesthesia Provides immediate access for IV injections & fluid administration Place before anesthetic induction Because most anesthetic cause hypotension (low blood pressure) or vasoconstriction (narrowing of blood vessel diameter) Supplies: Appropriately sized catheters Infusion sets Needles Syringes Tape Injection cap 7 Endotracheal Tubes Endotracheal intubation ensures a patent airway, facilitates patient ventilation, and provides easy delivery of volatile anesthetics ET T (endotracheal tube) diameter and length are important Diameter should be the largest size that will fit into the trachea with ease Generally – cats require 3-45. mm; dogs require 6-14 mm Length – inserted tip of the ETT should not extend beyond the thoracic inlet to prevent bronchial intubation The rostral end of the tube should be extend more than 1-2 inches beyond the mouth to limit mechanical dead space If ETT has an inflatable cuff → check for leaks 8 Laryngoscope Glottis = facilitates visualization of the glottis as the endotracheal tube passes through into the trachea Handle + detachable blade (variety of shapes & sizes) 9 Endotracheal Intubation 10  Medical Gas Supply Medical gases can be delivered via compressed gas cylinders by a central pipeline or direct attachment to the anesthesia machine Common sizes: E cylinder (4.25 x 26 inches) Attach directly to anesthetic machine (as backup or as direct source) H cylinder (9.25 x 51 inches) Color coded: Oxygen = green (except in Canada → white) Pressure regulators → attach to cylinder valve (H cylinder) or near hanger yokes (E cylinder) Passively reduce oxygen pressure to the normal working pressure of the anesthetic machine (50 psi) A = line pressure gauge B = tank pressure gauge line pressure gauge before every procedure C = pressure reducing valve 11  Anesthesia Machines Deliver a mixture of oxygen and inhaled anesthetic to the breathing circuit Components: Oxygen source A = carrier gas supply Pressure regulator B = vaporizer Oxygen pressure valve C= breathing circuit Flowmeter Vaporizer Breathing circuit Reservoir bag Circuit manometer Positive pressure relief valve Carbon dioxide absorbent Unidirectional dome valves 12 Anesthesia Machine 13  Flowmeter Receives medical gases from the pressure regulator Purpose: To measure & deliver a constant gas flow to the vaporizer, common gas outlet & breathing circuit Further reduces the pressure of the gas in the intermediate pressure line from 50 psi to 15 psi O2 enters the flowmeter near the bottom & travels upward through a tapered, transparent flow tube w/ a floating indicator Common sources of leaks Control valve 14 Anesthesia Machine 15 Vaporizer Inhalant anesthetic gas = volatile liquids that vaporize at room temperature Main function of a vaporizer = controlled enhancement of anesthetic vaporization Each vaporizer is design to be used with a specific inhalant anesthetic & is color coded Deliver a constant concentration (as a %) that is automatically maintained with changing O 2 flow rates & temperature Designed to function out of the breathing circuit (VOC = vaporizer out of circuit) = between flowmeter and breathing circuit Hazards A = inlet port B = outlet port Filling with the incorrect agent C = safety lock Tipping the vaporizer D = indicatory window Overfilling the chamber E = fill port F = oxygen flush valve 16 Anesthesia Machine 17 Breathing Medical gases pass from the anesthesia machine to the patient through tubing = breathing circuit Circuits Deliver fresh gases (oxygen & anesthetic vapor) to the patient & transport exhaled gases away from the patient Two types: Rebreathing system (circuit) – breathing circuit is incorporated into the machine & CO 2 is eliminated from the circuit by soda lime absorption Nonrebreathing system (circuit) – CO2 is eliminated using high gas flow rates & NOT a CO2 absorber 18 Rebreathing Circuits Most commonly used in veterinary medicine; aka circle system Amount of CO2 “rebreathed” depends on the degree of CO2 absorption & fresh gas flow rate Components: Reservoir bag Manometer Positive pressure relief valve (pop-off valve) Carbon dioxide absorbent Unidirectional valves Fresh gas inlet Removable set of breathing tubes 19 Rebreathing Circuits Advantages: Conservation of body heat & fluids Reuse of exhaled O2 & anesthetic gases Cost-efficient Lower flow rates Disadvantages: Danger of hypercapnia = high blood CO2 due to malfunction of CO2 absorbent or unidirectional valves 20 Reservoir Bag Aka rebreathing bag Provides a gas volume sufficient for the patient to inhale maximally without creating negative pressure in the circuit Used to give positive pressure ventilation (breaths) or to inflate the lungs when needed Sizes = 0.5 – 5 L (small animals) Ideal size = 5-6 x patient’s normal tidal volume of 10 ml/kg 21 Manometer Used to monitor circuit pressure Excessive circuit pressure – may prevent normal respiration & cause decreased venous return & a drop in cardiac output Useful during positive pressure ventilation (bagging) During spontaneous breathing – should not be above 2 cm H2O 22  Positive Pressure Relief Valve Aka pop-off valve Prevents excessive pressure in the rebreathing circuit & allows for the removal of excess waste gases ALWAYS LEAVE OPEN – except when giving a positive pressure ventilation Connected to the scavenging system → to prevent gas discharge into room air 23 Positive Pressure Relief Valve 24 Carbon Dioxide Absorbent Canister Removes CO2 from the exhaled gases before the gases are returned to the patient Gases are directs to the canister by the expiratory unidirectional valve Contains absorbent granules (calcium hydroxide) – removes CO2 from the expired air Should be changed either monthly or after 6-8 hours of use (whichever is first) 25  Comparison of Fresh & Exhausted CO2 Granules Feature Fresh CO2 Granules Exhausted CO2 Granules Consistency Ca(OH)2 – chip or crumble CaCO3 – hard and brittle with finger pressure Color White Slightly off white pH indicator Pink or white depending on When ⅓ - ½ of granules brand change color to white instead of pink/violet instead of white Carbon Dioxide Absorbent Granules 26 Unidirectional One-Way Valves Aka flutter valves Maintain one way flow of gases within the breathing circuit Inhalation/inspiratory unidirectional valve – opens so that fresh gas + anesthetic can flow into patient Exhalation/expiratory unidirectional valve – opens during exhalation Passes through the CO2 absorbent 27 Inspiratory & Expiratory Breathing Tubes Corrugated hoses that carry anesthetic gases to and from the patient Each tube is connected to a unidirectional valve at one end and the Y piece at the other end Standard tubes = 1 m long for patients weight 7 kg – 135 kg (15.4 -297 lb) Shorter tubes for patients under 7 kg Large animal tubes = 1.7 m long Classic set up = separate inhalation & exhalation tubes connected via Y piece F-circuit = inhalation tube inside exhalation tube Advantages = warming of inhaled gas by exhaled gas 28 Rebreathing Circuit = oxygen = anesthetic gas = CO2 29 Nonrebreathing Circuits Do not have a carbon dioxide absorber Exhaled gases are immediately vented from the system through another hose (usually into a reservoir bag) where the gases are released into the scavenging system through an overflow valve Recommended for patients