Anesthetic Monitoring Lecture Notes

Anesthetic Monitoring Lecture Notes

Introduction

  • Discussion on anesthetic monitoring covering a wide range of topics.
  • Speaker acknowledges the length of the lecture and suggests breaks.
  • Reminder about checking laundry procedures in lab settings.
    • Importance of shaking out towels and blankets to prevent leaving unexpected items like catheter caps in laundry.

Reading Assignments

  • Assignments consist mostly of comparison tables and flow charts.
  • Upcoming in-depth lecture planned on ECGs which has been briefly covered before.
    • Students should be familiar with the normal ECG complex due to prior exposure in diseases and possibly anatomy classes.
    • Speaker expresses limited usefulness of ECG in monitoring compared to other devices.

Pre-Anesthetic Preparation

  • Importance of obtaining baseline measurements before surgery:
    • Temperatures, Pulse, Respiration (TPR), body weight, and necessary blood work.
    • Big Four Blood Work - PCV, Total Protein, Glucose, BUN.
    • CBC with differential plus chemistry panel (full blood work).
    • Consider adding a urinalysis for comprehensive assessment.
  • Ensure availability of cage setup for post-operative recovery, including warming equipment.
  • Importance of knowing the anesthetic drugs and having a conversation with the doctor about post-operative medications.

Anesthesia Equipment Check

  • Check the anesthesia machine:
    • Leak test the machine and breathing circuit.
    • Verify vaporizer levels and Sodasorb freshness.
    • Select and leak check appropriate endotracheal tubes based on patient size post-sedation.
  • Check monitors for battery levels or plug-ins.
  • Importance of warming equipment due to risk of hypothermia during inhalant anesthesia to prevent complications post-surgery.

Importance of Monitoring Patients

  • Monitoring ensures patient safety during anesthesia.
  • Key parameters to observe include:
    • Respiratory rate and heart rate.
    • Oxygenation levels, End tidal CO2.
  • Recognizing changes in anesthetic depth to prevent emergencies:
    • Patients can be light (perceiving pain), too deep (slow recovery risk), or potentially face overdose risk leading to death.
  • Monitoring intervals:
    • Every 5 minutes for vital signs, and every 15 minutes for temperature if accessible.

Monitoring Techniques

  • Primary Monitor: The anesthetist themselves - understanding baseline vital signs is key.
  • Equipped Devices: Various attachments on patients including:
    • Endotracheal tubes, esophageal stethoscopes, breathing circuits, capnographs, pulse oximeters, blood pressure monitors, and ECG leads.
  • Require attention to detail during procedures to prevent complications, ensuring nothing is mistaken or disconnected.

Vital Signs Monitoring

  • Respiratory and Circulatory Monitoring:
    • Monitor heart rhythm and rate through auscultation or ECG.
    • Watch lung respiration pattern and effort, respiratory depth/quality.
    • Normal blood pressure and mucous membrane color, capillary refill time, pulse quality, and temperature are crucial indicators.
  • Reflex Monitoring:
    • Palpebral reflex, swallowing reflex, pedal reflex, and pupillary light response.
    • Corneal reflex in large animals (rarely used in small animals).
  • Ensure no spontaneous movement; eyes should be ventromedial in proper anesthetic depth (eye position can be indicative of anesthetic depth).

Stages of Anesthesia

  • Overview of stages:
    • Stage One: Calm to light anesthesia.
    • Stage Two: Excite phase before anesthesia.
    • Stage Three: Surgical plane—No response to painful stimuli, normal vital signs.
    • Stage Four: Imminent danger—needs immediate intervention.
  • Signs of too light or too deep anesthesia:
    • Too light: Movement response, increased heart rate.
    • Too deep: Lowered tidal volumes, prolonged CRT, central eye positioning with dilated pupils.

Recommended Monitoring Frequency & Tools:

  • Monitor every 5 minutes, temperature every 15.
  • Notable need to track:
    • Blood pressure, depth of anesthesia, vital signs including Mucous membrane and reflexes.

Equipment and Techniques for Monitoring:

  • Oxygenation:
    • Measure arterial Oxygen saturation (SpO2) via pulse oximeter.
    • Normal range: 95-100% SpO2, with 90-94% being concerning and under 85% as emergency.
    • Unbound oxygen dissolves in plasma; bound oxygen attaches to hemoglobin.
    • Arterial blood analysis is gold standard for checking oxygen and carbon dioxide levels.

Blood Gas Analysis:

  • Understanding arterial (PaO2, PaCO2) vs. venous blood (PVO2, PVCO2).
  • Recognizing thresholds for hypoxemia and action levels:
    • Below 60 mmHg (PaO2) requires intervention—emergency.

Ventilation Monitoring:

  • Tidal Volume: Volume of air exchanged in one full respiratory cycle, must monitor quality.
  • Use of capnographs/capnometers:
    • Normal end-tidal CO2: 35-45 mmHg, up to 55 in surgical patients.
    • Monitoring for respiratory distress/hypercapnia with capnographs.

Circulation Monitoring:

  • Assess heart rate based on pre-anesthetic evaluation (dogs: 60-120, cats: 95-160 BPM).
  • Blood Pressure: Important thresholds:
    • Systolic < 90 = concern; normal MAP should be 70-90.
    • Knowing your patient’s baseline is crucial for effective monitoring.
    • Using Doppler and Oscillometric Machines:
    • Doppler gives systolic; Oscillometric provides more comprehensive readings but might underestimate in certain cases.

Temperature Regulation:

  • Normal temperature range 100-102°F, with actions required for hypothermia (<97°F).
    • Measures to prevent cooling: heated tables, bear hugger, warm IV fluids.
  • Overheating (>103.5°F) also traumas, monitoring with consequences.

Post-Anesthetic Recovery:

  • Stay with patients during recovery; frequent assessments of their temperature, vitals, reflexes, and activity.
  • Awareness of Risks: Animals can crash during recovery if not monitored closely; need for oxygen and re-acclimatization checks.
  • Shivering expected; protect airway from obstruction due to secretions.
  • Utilize proper handling techniques when extubating and provide adequate post-operative care.

Conclusion

  • Recap of significant points about monitoring and managing patients during and post-anesthesia.
  • Emphasis on the importance of comprehensive understanding and vigilance during surgical procedures.
  • Students encouraged to prepare thoroughly before the test for comprehensive understanding and application during the practical sessions.