Pre-Anaesthetic Evaluation, ASA Risk & IV Catheter Placement – Comprehensive Study Notes

Overview of Anaesthetic Procedure

Pre-Anaesthetic Evaluation

• Dual goal: (1) Detect pre-existing problems, (2) Generate an anaesthetic plan tailored to patient & procedure.

• Must be performed every time, even for “routine” cases (spays, neuters, dentals, CT scans, etc.).

Key Topic Questions (Lecturer Prompts)

• Can you perform—and explain the importance of—a pre-anaesthetic assessment?

• Do you understand the purpose, placement steps and required equipment for an IV catheter (IVC)?

Self-Assessment Questions for Students

• Why is a FULL clinical exam essential before anaesthesia?

• List key parameters to assess (HR, RR, temperature, mucous membranes, etc.).

• How do findings alter anaesthetic risk or drug choice?

• What common pre-anaesthetic tests exist (blood work, BP) and why do they matter?

• Describe your role in assisting the veterinarian during this stage.

Clinical Examination

Required Equipment

• Stethoscope

• Printed/ digital Clinical Examination Form

• Thermometer + lubricant

• Blood-pressure monitor (oscillometric or Doppler)

Core Parameters (minimum data set)

• Temperature – look for hypothermia or pyrexia.

• Heart rate and pulse rate – auscultate for murmurs, palpate for pulse strength/ deficits; note arrhythmias.

• Respiratory rate & effort – tachypnoea, bradypnoea, noisy breathing, restrictive pattern.

• Blood pressure – especially in geriatric or systemically compromised animals.

• “Nose-to-Tail” general inspection.

Nose-to-Tail Examination Items

• Mucous membranes & capillary refill time (CRT)

• Eyes, ears, and oral cavity

• Peripheral lymph nodes (sub-mandibular, prescapular, popliteal)

• Thoracic auscultation (heart and lung fields)

• Abdominal palpation (veterinarian only)

• Skin condition (parasites, wounds, dermatitis)

• Body Condition Score (BCS) & hydration status

• Gait, mobility, signs of pain

Why It Matters

• Detects hidden disease → adjusts drug choice, monitoring intensity, fluid plan.

• Provides baseline values for intra-operative comparison and post-op recovery.

• Determines ASA score and informs consent discussion with client.

Decision-Making Scenarios ("What would you do if …")

• Heart murmur ➔ Notify vet; consider echo, choose cardio-friendly agents (e.g.
  avoid high doses of $\alpha_2$ agonists).

• Pale mucous membranes ➔ Check PCV/TP, suspect anaemia or hypovolaemia; may postpone procedure.

• Abnormal lung sounds ➔ Chest radiographs, postpone if pneumonia/ oedema.

• Tachycardia/ bradycardia ➔ ECG, adjust pre-med; possibly avoid anticholinergics vs. use them.

• Laboured breathing ➔ Oxygen, thoracic imaging; GA may be high-risk.

• Hypotension ➔ IV fluids pre-op, dopamine/dobutamine ready intra-op.

• Pyrexia/ hypothermia ➔ Treat source, active warming/ cooling before GA.

• Unexpected pain or swelling ➔ Analgesia plan; investigate cause (abscess, fracture, tumour).

Documentation & Communication

• Record ALL findings legibly; electronic or paper accepted by clinic policy.

• Immediate escalation of abnormal findings to veterinarian/ anaesthetist.

• Findings may trigger:

  • Drug changes (e.g.
    avoid $\alpha_2$ in severe bradycardia).

  • Additional monitoring (ECG, arterial line, capnography).

  • Delay or cancellation if risk > benefit.

Pre-Anaesthetic Testing

Common Tests & Why They Matter

• Bloodwork:

  • Packed Cell Volume (PCV) & Total Protein (TP)

  • Complete Blood Count (CBC/haematology)

  • Biochemistry (renal, hepatic, electrolytes, glucose)

  • Special tests: coagulation, thyroid, bile acids, cross-match.

• Urinalysis – kidney concentrating ability, glucose, protein.

• Imaging – radiographs, ultrasound for cardiac/ abdominal screening.

• Neurological or orthopaedic exam when indicated.

Preparation for Blood Tests

• Gather all consumables BEFORE venepuncture:

  • Clippers, alcohol/ tincture swab, 20-G needle & syringe, labelled tubes, micro-haematocrit tubes & plug.

Workflow After Collection

• Perform or send tests; ensure correct sample/ machine pairing (some in-house units run only biochemistry).

• Results entered in patient record; vet adapts pre-meds and intra-op plan accordingly.

Anaesthetic Risk Assessment

Purpose

• Proactively identify complications; match resources (staffing, monitoring, emergency drugs) to patient risk.

• Foundation for informed owner consent.

ASA Physical Status Classification (adapted to veterinary species)

• I – Healthy, no disease (e.g.
  1-2 yr dog for routine neuter).

• II – Mild systemic disease (mild dental disease, controlled diabetes, obesity).

• III – Moderate systemic disease (heart murmur, early CKD, anaemia).

• IV – Severe systemic disease, constant threat to life (sepsis, uncontrolled diabetes, severe dehydration).

• V – Moribund, likely to die without operation (GDV, major trauma, end-stage organ failure).

Using ASA in Practice

• Assign class during pre-anaesthetic visit; log in anaesthetic record.

• Guides:

  • Choice & dose of agents (e.g.
    an ASA III may receive opioid + benzodiazepine pre-med rather than $\alpha_2$-agonist).

  • Monitoring depth (basic vs. invasive BP, arterial blood gas).

  • Team readiness (ecc cart location, extra IV lines, blood products on standby).

• Not designed to predict surgical outcome; purely anaesthetic risk.

Limitations

• Subjective grading between clinicians.

• Does not include procedure complexity (e.g.
  long orthopaedic vs.
  10-min lump removal).

• Always integrate with full clinical picture.

Case Examples

• Case 1: 2-year Labrador neuter = ASA I.

• Case 2: 10-year cat, hyperthyroid = ASA III (moderate disease).

• Case 3: 5-year dog, HBC with internal bleeding = ASA IV–V depending on stability.

Intravenous Catheter (IVC) Placement

Why EVERY Anaesthetised Patient Needs One

• Immediate vascular access for induction, emergency drugs, and fluid therapy.

• Allows titration of anaesthetic agents and CRIs.

• Facilitates blood sampling without repeated venepuncture.

• Enhances overall patient safety; should also be placed for deep sedation where airway access is limited.

General Considerations

• Use catheter gauge suitable for the patient, not the placer; larger is not always better but must allow required flow.

• Prepare all equipment before restraining.

• Observe the “2-stick rule”: if unsuccessful twice, ask another trained person to try.

Skin Preparation & Asepsis

• IVC = direct portal to bloodstream; strict aseptic technique mandatory.

• Clip a WIDE area, using clean and fully charged clippers.

• Three-step scrub (example):

  1. Chlorhexidine soap (Microshield 4) ± gauze scrub.

  2. Aqueous chlorhexidine (Microshield 5 + water).

  3. Alcohol-based tincture (Microshield 5 + alcohol).

• Allow adequate contact time for each layer; scrub until visibly clean.

• Wear gloves; hand disinfect with Sterillium prior to placement.

Complete Equipment Checklist

• Clippers

• Chlorhex/alcohol swabs & full scrub solutions

• Multiple IVCs (e.g.
  20 G, 22 G)

• Tape (hypoallergenic & strong adhesive varieties)

• T-port or bung

• Sterile saline flush (syringe + needle-free hub)

• Softban padding & vet-wrap

• Sharps container

• Gloves

• Optional: extension set, armboard, cohesive tape, heparinised saline

Selecting a Vein

• Cephalic vein (forelimb) = default in dogs & cats.

• Alternatives: jugular, lateral/medial saphenous, accessory cephalic, auricular (exotics), tail (large dogs).

• Choose a vein that provides straight access, minimal movement during procedure.

Step-by-Step Placement Technique

1. Restrain patient in sternal or lateral recumbency; extend limb.

2. Assistant “raises” vein by digital occlusion distal to intended site.

3. Palpate vein; align catheter bevel up.

4. Pierce skin briskly (tough) then vein wall (soft) at shallow angle.

5. Look for blood “flashback” in hub.

6. Advance catheter off stylet into vessel; keep stylet stable.

7. Ask assistant to occlude vein just distal to hub.

8. Remove stylet; attach bung/T-port.

9. Release occlusion; flush with $0.9\%$ NaCl to check patency (feel vein for fluid pulse).

10. Secure with tape:

    • First strip underneath hub → wrap over top.

    • Additional strips pinched around hub & extension line.

11. Light padded bandage (Softban + vet-wrap) from paw upward; avoid excessive compression.

12. Label time/ date; flush every 4 h in hospitalised patients.

Post-Placement Checks & Fluid Line Setup

• Re-flush and palpate vein; confirm no swelling or resistance.

• Attach IV fluid line; tape line up limb to reduce kinking.

• Keep injection ports accessible.

IV Fluids During Anaesthesia

Why Give IV Fluids?

• Support arterial blood pressure (counteract anaesthetic-induced vasodilation).

• Maintain hydration (patients are fasted and may be dehydrated).

• Improve circulation of drugs, oxygen, and metabolic waste.

Basic Calculation Formulae

• Maintenance fluid rate: $2\,\text{mL/kg/hr}$ (dogs) to $3\,\text{mL/kg/hr}$ (cats) during anaesthesia (varies by clinic).

• Example total rate: $\text{Rate} = \text{Weight\,(kg)} \times 3\,\text{mL/kg/hr}$ ⇒ 4 kg cat ≈ $12\,\text{mL/hr}.$

• Shock dose guideline (dog): $90\,\text{mL/kg};$ (cat): $60\,\text{mL/kg}$ – but given in aliquots & titrated.

Preparing IV Fluids

• Select correct fluid type (LRS, Hartmann’s, Plasmalyte, saline, colloid) per veterinarian.

• Gather giving set ± extension; hang on drip stand.

• Aseptically spike bag; fill chamber halfway.

• Prime line slowly to remove air; check for bubbles/ leaks.

• Allocate a calibrated infusion pump & ensure charger presents.

Ethical, Practical & Communication Notes

• Informed owner consent must include discussion of identified risks (ASA class, comorbidities).

• Students/ nurses must communicate abnormal findings IMMEDIATELY—patient safety overrides hierarchy.

• Respect patient comfort: gentle handling, especially arthritic seniors; use sedation if necessary for low-stress sampling.

• Maintain asepsis throughout – catheter-related infections increase morbidity & cost.

References & Further Learning

• 2020 AAHA Anaesthesia & Monitoring Guidelines for Dogs & Cats (Grubb et al., 2020).

• Portier & Ida (2018) – Evidence review on ASA classification in veterinary anaesthesia.

• World Veterinary Service (WVS) Academy – Free procedural modules & images.

• AtDove & VetGirl – Step-by-step videos for feline pre-anaesthetic evaluation and catheter placement.

• Browning & Tobias (2016) – Pre-operative roles of veterinary surgical nurse.