Anesthetic troubleshooting

Anesthetic Troubleshooting & Patient Considerations

Common Causes of Anesthetic Complications

  • Every anesthetic procedure potentially leads to animal death.
  • Reasons for complications include:
    • Human error
    • Equipment issues
    • Adverse effects of anesthetic agents
    • Patient-related issues

Human Error

  • Major aspects leading to complications:
    • Inadequate physical examination (PE) and history knowledge.
    • Insufficient training of personnel.
    • Incorrect drug administration or calculation.
    • Factors such as fatigue, haste, and inattention.
    • Errors in machine assembly.

Equipment Issues

Anesthesia Machine Failure
  • Consequences: Patient may not remain anesthetized due to incorrect gas percentages.
  • Prevention: Ensure machines are serviced annually.
Vaporizer Issues
  • Common Problems:
    • Incorrect anesthetic agent in vaporizer.
    • Solution: Change machines and contact service provider.
    • Stuck dial.
    • Solution: Change machines and contact service provider.
    • Overfilled agent.
    • Action: Turn off vaporizer if agent is flowing out and clean spills.
    • Prevention: Watch the window while refilling and fill slowly.
    • Leaking Waste Anesthetic Gas (WAG).
    • Prevention: Perform a leak test on the machine and breathing circuit prior to each use.
    • Solution: Change machines.
Endotracheal (ET) Tube Failure
  • Problems: Tube may be clogged or kinked, leading to dyspnea and insufficient anesthetic/O2 delivery.
  • Monitoring Techniques: Mark the tube pre-placement and frequently check its placement.
  • Signs to Watch For: Movement in the reservoir bag, capnograph waveform, dyspnea signals.
  • Solutions:
    • Suction the patient's airway if needed.
    • Replace the tube if clogged.
  • Additional Issues: Oxygen tank may be empty or insufficiently pressurized.
    • Prevention: Check the oxygen tank volume and pressure prior to procedure and monitor the flow meter every 5 minutes during the event.
CO2 Absorbent Exhaustion
  • Consequences: Risks re-breathing expired CO2.
  • Prevention: Label CO2 absorbent change dates; check labels before use; change as needed.
  • Action if Observed During Procedure: Change machines.
Pop-off Valve
  • Potential Issues: Check if the valve is closed or stuck.

Patient-Related Issues

  • Considerations for specific patient categories:
    • Geriatric patients
    • Neonates (Pediatric)
    • Brachycephalic breeds
    • Obesity
    • Trauma patients
    • Conditions like hypovolemia, anemia
    • Systemic diseases affecting cardiovascular, respiratory, hepatic, and renal functions.
    • Special attention for cesarean section patients.

Geriatric Patients

  • Co-morbidities: Common heart issues require consultation regarding daily medications.
  • Fluid Management: Careful of IV fluid management to avoid overhydration.
  • Drug Considerations: Renal disease affects drug metabolism; consider pre-surgical diuretics.
  • Monitoring Baseline Blood Pressure: Address any electrolyte imbalances before surgery.
  • Anemia Consideration: Assess if the patient is anemic.
  • Age-related Changes:
    • Lung Function: Lower tidal volume (Vt), increased susceptibility to hypoxemia and hypercapnia, typically lower SpO2 levels.
    • Gastrointestinal Changes: Slower transit time increases aspiration risk; may require suctioning or GI medications pre-anesthesia.
    • Body Condition Score (BCS): Consider impaired thermoregulation ability.

Pediatric Patients / Neonates (6 weeks - 12 weeks of life)

  • Considerations: Less adept in coping with physiological stresses like blood glucose fluctuations and fluid imbalances.
  • Maturity Issues: Immature liver and kidney functions; decreased drug metabolism and excretion.
  • System Considerations: Cardiovascular and respiratory systems are immature, leading to increased susceptibility to anesthetic effects.
  • Complications: Higher risks of hypothermia, hypoglycemia, and dehydration.
  • NPO Guidelines: Do not withhold water, especially in patients < 8 weeks of age; consider adding 5% dextrose to IV fluids.
  • Fluid Administration: Monitor closely to prevent overhydration.

Obese Patients

  • Considerations: Greater fat percentage affects anesthetic distribution.
  • Recommended Dosage: Adjust dosages by averaging between ideal body weight and actual weight (e.g., dosing half-way in between).
  • Equipment Needs: May require smaller reservoir bags and ET tubes.
  • Respiratory Considerations: Increased respiratory difficulty and requirement for pre-oxygenation; manual ventilation may be necessary throughout the procedure.

Brachycephalic Breeds

  • Considerations: Structural issues like elongated soft palates and small tracheas lead to respiratory challenges.
  • Procedure Strategies: Maintain an open airway during the procedure and recovery; keep sufficient oxygen supply post-operation.
  • Monitoring: Be attentive to dyspnea during recovery and potentially re-intubate; swelling risk in surgeries within the pharyngeal region.

Anesthetic Equipment Troubles

Reservoir Bag Conditions
  • Too Distended:
    • Check the pop-off valve (closed or not?), check O2 flow, and verify if the patient is breathing.
  • Deflated Bag:
    • Confirm if the patient is breathing, whether O2 flow is set correctly, and if the scavenger is overly active.
  • Decision to “Dump the System”:
    • Done when wishing for a swift change in vaporizer settings or to clear the anesthetic gas from the breathing system.

Common Anesthetic Problems and Emergencies

  • Recognize critical signs indicative of anesthetic issues:
    • Inability to maintain anesthesia.
    • Patient excessively deep or light in anesthesia:
    • Pale mucous membranes (MMC)
    • Prolonged capillary refill time (CRT)
    • Hypotension
    • Dyspnea / cyanosis
    • Tachypnea
    • Tachycardia / bradycardia
    • Abnormal cardiac rhythm
    • Apnea
    • Potential cardiopulmonary arrest (CPA)
  • Action Steps: Stay calm and assess; have the crash cart/drug bin accessible for emergencies.

Responses to Anesthetic Complications

Waking Up Mid-Procedure
  • Checks Required:
    • Verify vaporizer levels, ensuring agent is not depleted and settings are optimal.
    • O2 flow examination; potentially increasing flow may help enhance delivery time.
    • Confirm ET tube placement to rule out improper insertion or obstruction.
  • If this occurs frequently, consider servicing the vaporizer/machine.
Excessive Anesthetic Depth Signs
  • Clinical Indicators:
    • Respiratory rate (RR) < 6 breaths per minute, shallow breaths.
    • Pale or cyanotic MMC, prolonged CRT.
    • Bradycardia, cold extremities; hypothermic signs.
    • Central eye position, dilated unresponsive pupils, weak pulse, hypotension.
  • Actions:
    • Adjust vaporizer settings accordingly and assess oxygen flow; alert the veterinarian for further interventions.
    • Consider reversing anesthetic drugs if patient depth is too excessive.
Pale MMC Issues
  • Potential Causes:
    • Anemia, blood loss, anesthetic agents / pre-meds, vasoconstriction, hypotension, hypothermia, pain, hypovolemia.
  • Address: Determine anesthetic depth, assess vitals, and address causative factors including potentially administering a blood transfusion or adjusting the vaporizer settings.
Prolonged CRT (> 2 seconds) Implications
  • Causes:
    • Related to hypotension, perfusion problems, dehydration, or exacerbating conditions.
  • Recommended Action: Assess and address blood pressure, alert the veterinarian, potentially adjust vaporizer settings.
Hypotension Observations
  • Common in Anesthesia:
    • Defined by parameters: Systolic BP < 80-90 mmHg and/or MAP < 60 mmHg.
    • Possible causes include excessive anesthetic depth, drug effects, hypovolemia, or dehydration.
  • Prevention/Management Techniques:
    • Ensure appropriate cuff size during BP measurement (40% of limb circumference).
    • If stable, verify BP equipment accuracy before treating the patient.
Hypotension Treatments
  • Protocols include:
    • Assess patient stability, check correct cuff placement and size.
    • If stable, adjust vaporizer settings, administer IV fluids or boluses after consultation with the veterinarian.
    • Typical fluid rates: Dogs: 5 ml/kg/hr; Cats: 3 ml/kg/hr; bolus: ~10 ml/kg, then reassess.
  • Bradycardia Relationship:
    • Monitor and manage alongside hypotension, potential administration of glycopyrrolate.
    • Consider medications like dopamine, dobutamine, vasopressin, or hetastarch as needed.
Dyspnea / Cyanosis Understanding
  • Definitions:
    • Dyspnea: Inability to obtain sufficient oxygen with normal respiratory effort; indicates potential respiratory distress.
    • Cyanosis: Sign of inadequate tissue perfusion/oxygenation.
  • Immediate Measures: Check SpO2 levels, act swiftly to prevent respiratory arrest.
    • Potential causes may include equipment failures, airway obstructions, or excessive anesthetic depth.
Dyspnea / Cyanosis Actions
  • Responses to Equipment Failures: Replace O2 tank or machine; insert a new ET tube.
  • If Patient Issues: Turn off vaporizer, empty system, administer 100% O2, alert the veterinarian for further treatment.
Tachypnea Recognition
  • Signs: Elevated respiratory rates and shallow breaths.
  • Diagnosis: Often indicates light anesthetic depth, especially in conjunction with tachycardia. It may also result from hypoxemia, hyperthermia, or obesity.
  • Treatment Steps: Administer analgesia if pain is the cause or adjust the anesthetic depth if needed.
Tachycardia vs. Bradycardia
  • Tachycardia Overview: Usually indicates too light a depth of anesthesia; treated with vaporizer adjustments, analgesia, and induction agents.
  • Bradycardia Overview: Indicates depth that is too deep; managed by lowering vaporizer settings, assessing for drug responses, and possibly reversing agents.
  • Temperature Effects: Be vigilant; hypothermia may worsen bradycardia events.
Apnea Situations
  • Definition: Cessation of breathing during induction or maintenance phases of anesthesia.
  • Monitoring Needs: Assess vital parameters including end-tidal CO2 (EtCO2), SpO2, and MMC.
    • Manual breaths may be necessary or placing the patient on a ventilator, based on patient condition.
Review of Oxygen Saturation (SpO2) and End-tidal CO2 (EtCO2) Parameters
  • SpO2 Reference Values: Normal range between 96%-100%; <90% indicates hypoxemia needing immediate intervention, and adjustments should be made for patient and equipment.
  • EtCO2 Values: Normal 35-45 mmHg, with >55 mmHg often linked to hypoventilation due to anesthetic agents; <35 mmHg indicates hyperventilation due to various causes.
  • Management Adjustments: Tailor oxygen delivery and evaluate respiratory efforts or ventilatory patterns accordingly.

Final Notes

  • Always remain vigilant about signs of distress or potential emergencies during anesthetic procedures, regularly verify equipment function, and adjust anesthetic depth or oxygen as needed to maintain patient safety.