Feline Anesthesia Fluid Therapy Treatment of Anesthetic Complications

Transcription

1 Feline Anesthesia Fluid Therapy Treatment of Anesthetic Complications Rebecca A. Krimins, DVM, MS April 29, 2018 DCVR Annual Spring Symposium

2 Cat Anesthesia There is no single best method for anesthetizing cats. Considerations: the patient s temperment, medical history, the available staff, the equipment, the owners expectations, finances, the procedure to be performed, physical status, etc. Often, when formulating an anesthetic plan, it is best to consider using relatively low doses of several different drugs rather than a large dose of a single drug. A provision to control pain should be included.

3 Feline Anesthesia Patient history Physical examination Laboratory evaluation Physical status (ASA)

4 Feline Patient Preparation Fasting Patient stabilization Venous access Intravenous fluids

5 List of Conditions That Should be Corrected Prior to Anesthesia Severe dehydration Anemia (PCV < 20%) or hypoproteinemia (Albumin < 2.0 g/dl) Acid-base (ph < 7.2) and electrolyte disturbances (Potassium < or > 6.0 Pneumothorax Cyanosis Oliguria or anuria Congestive heart failure Severe, life-threatening cardiac arrhythmias

6 The Anesthetic Plan Short-term anesthesia (< 15 minutes) Intermediate-term anesthesia (15-60 minutes) Long-term anesthesia (> 1 hour)

7 Feline Premedications Acepromazine plus opioid Ketamine Acepromazine plus ketamine Dexmedetomidine (young and healthy) Telazol (tiletamine/zolazepam) Low dosages are preferred

8 Feline Induction Intravenous induction Intramuscular induction Chamber/mask

9 Vaporizer Settings Drug Induction Phase (%) Maintenance Phase (%) halothane isoflurane sevoflurane

10 Feline Anesthesia What Else? Anesthetic maintenance The anesthetic record Perioperative analgesia Recovery Perioperative hypothermia Delayed anesthetic recovery

11 Fluid Therapy

12 Fluid Therapy An animal s body water is ~ 60% of the adult body weight. An animal s blood volume is ~ 7% of the adult body weight. Body fluid compartments Intracellular Extracellular: intravascular, interstitial, and transcellular compartments Water moves between compartments through osmosis Water will move to follow Na

13 Indications for Fluid Therapy Fluid therapy is a vital tool to help provide the stable conditions required for cardiovascular support. Inhaled anesthetic agents cause a dose-dependent vasodilation of the periopheral vessels and a reduction in cardiac output. Fluid administration is essential to counter hypotension and ensure optimal oxygen delivery to tissues. Animals are exposed to sensible and insensible fluid loss in the perioperative period and are unable to compensate for these losses without proper fluid administration.

14 Loss of Body Fluids Sensible Fluid Loss Vomiting and diarrhea Blood loss during surgery or trauma ascites Urination under normal conditions Insensible Fluid Loss Fluid loss through airway during inhalant anesthesia Water vapor loss through respiration and panting Evaporation through open body cavity during surgery Third spacing of fluid loss

15 Fluid Classification Crystalloids Colloids Blood products

16 Crystalloids Advantages Disadvantages

17 Crystalloid Fluid Rates Always Reassess Fluid rates should be reassessed Maintenance fluid rate in healthy cat: 5 ml/kg/hr When to increase? Blood loss Hypovolemia Hypotension When to decrease? After two hours of anesthesia Overhydration Cardiac disease Intracranial disease

18 Colloids Daily limit: 20 ml/kg IV Bolus amount: 5 ml/kg IV given over ten-twenty min. Advantages Disadvantages

19 Blood Products Advantages Disadvantages

20 Anesthetic Complications

21 What Can Go Wrong? Circulation Oxygenation Ventilation Body temperature Blood glucose levels Blood lactate levels Blood electrolytes Depth of anesthesia Pain management

22 Overview What s Important? Monitoring : remember COVE COVE Circulation Oxygenation Ventilation 22

23 Blood Pressure Accuracy of BP Readings Equipment: Direct: arterial line (most accurate) Indirect: Doppler Oscillometric (least accurate) 23

24 Blood Pressure under GA SBP: mmhg (normals) DBP: mmhg MBP: mmhg Causes of hypotension: hypovolemia, poor cardiac output, vasodilation Most general anesthetics contribute to hypotension (i.e. acepromazine, inhalants, local anesthetics, NMBAs, etc.)

25 Blood Pressure What Is Too High? Too high of a blood pressure? SBP>140, DBP>100, MBP>120 Is your patient awake? Is your patient painful?

26 Cuff width = 40% circumference

27 Blood Pressure What Is Too Low? Too low of a blood pressure? SBP<100, DBP<60, MBP<80 Turn down inhalant Give crystalloid bolus Give colloid bolus Start a positive inotrope CRI When initiating blood pressure treatment, most of these treatments will take at least ten minutes before you see the affect.

28 Managing Blood Pressure Positive Inotropes Dopamine CRI ( mcg/kg/min) How to make your own CRI (360 mcg/ml) Need: 60 drop/ml IV drip set, 250 ml bag fluids Add 1.1ml dopamine (80 mg/ml) to a 250 ml bag fluid bag Run at 1 drop/1-5 seconds

29 Pulse Pressure Palpate a pulse Difference between systolic and diastolic blood pressure How to interpret?

30 Electrocardiography Monitors electrical activity of the heart (heart rate and rhythm) Can you see a P wave, QRS wave, T wave? 30

31 Heart Rate and Blood Pressure Always Assess Together Heart Rate MBP Causes Treatment Low Low Drugs, high vagal tone, hypothermia, etc. Low High Athletic animal (normal), alpha-2 agonist High Low Drugs causing vasodilation, dehydration, hypovolemia Anticholinergics, treat underlying problem No treatment Reduce drug therapy; fluid therapy High High Drugs, pain, etc. Treat underlying problem 31

32 How To Assess Oxygenation? Mucous membrane color (subjective) Keep flashlight nearby Pulse oxymetry Arterial blood gas

33 Pulse Oxymetry (SPO 2 ) ALWAYS > 95% Measures hemoglobin saturation

34 Causes of Hypoxemia Hypoventilation Low inspired oxygen conc. V/Q mismatch (shunting) Diffusion impairment (COPD) Low CO Increased metabolism for O 2 Decreased CaO 2 (anemia)

35 Factors that Influence SPO 2 Motion (shivering, movement) Ambient light (fluorescent light bulbs) Poor blood flow Electrical noise (cautery) Hair and/or pigmented skin Probe is too loose/tight Poor contact between probe and tissue (use wet gauze)

36 Pre-oxygenation

37 Ventilation subjective assessments Monitor chest excursions and/or rebreathing bag Auscultate breathing sounds Place hand one-inch away from patient s nose and feel for expiratory breath

38 Ventilation objective assessments Capnometry Arterial blood gas

39 Capnometry What can your capnograph tell you? Inadequate FGF Circuit kink Esophageal intubation Circuit disconnection or extubation Hypoventilation Cardiac arrest Exhausted soda lime

40 Other monitoring parameters (besides COVE) Signs of pain Blood glucose, blood lactate, electrolyte balance, PCV, TP Core body temperature Depth of anesthesia

41 Temperature Normal body temp for dog/cat is F Heat loss: evaporative, convective, conductive and radiant

42 Preventing Heat Loss Turn the hot water blankets on as soon as possible and use different types of warming devices on the patient Hair clipping and prepping be careful Replace wet blankets Dry patient after surgery Pre-warm lavage fluids Check temp q 5-15 min until normal

43 Tech to tech How to handoff a case What s the wrong way to hand off a case? What s the right way to hand off a case?

44 Veterinary Technicians When To Speak Up? The anesthetist: takes care of the patient s anesthetic and analgesic needs while allowing the veterinarian to perform a procedure in an efficient manner Veterinary preferences: what does the DVM prefer Bring abnormalities/problems to your doctor s attention Have a solution

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