Pharmacology and Pharmacy

VETE 4305

02/22/2015

Gastric Dilation Volvulus (GDV) Surgery

Jennifer Hohle, LVT

Ashley Lawley, LVT

Michelle Hervey, LVT

Case Study Group 2

A three-year-old intact male Great Dane was presented with a history of abdominal distention and retching. The owner had noticed the retching several hours earlier, but thought the dog had eaten something it found in the yard. Upon recognizing the abdominal distention, the owner immediately brought the dog to your clinic. Radiographs revealed a gas distended stomach with classic “double-bubble” sign. The veterinarian suspected gastric dilation volvulus and the dog was brought immediately into surgery.

Gastric Dilation Volvulus (GDV) Scenario

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In this particular case there are a few things to watch for

• First – Great Danes run the risk of cardiac arrythmias.

• Second – If the patient becomes bradicardic during anesthesia a drug like glycopyrrolate should be administered.

Identify the risk factors associated with GDV in this case. Define volvulus, hypovolemic shock.

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Volvulus Means twisting In this case twisting of the

stomach.

Is caused by rapid or severe fluid loss.

Corrected by bolus of intravenous fluids

Continued ….

Hypovolemic Shock

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What is an ASA?

ASA stands for American Society of Anesthesiologists

ASA is a classification for patients going under anesthesia to determine their anesthetic risk.

It ranges from ASA I (normal, healthy patient) to ASA VI (no brain activity).

This particular patient was given a grade of ASA IV, meaning that this is a patient with severe systemic disease that is life threatening (Thomas, 25).

You are initiating the anesthesia record for the animal. The veterinarian has assigned an ASA

status of Class IV. Explain the clinical significance of a Class IV assignment.

Please describe the actions you will take to determine why the animal is responding to stimuli/rapidly lightening up.

First - Check Equipment1. Vaporizer – sufficient anesthetic gas (Isoflurane).

2. Endotracial tube – patient is not breathing around the tube.

3. Rebreathing tube – hooked up properly to the machine. Inspiration and expiration is hooked up correctly.

4. CO2 Canister – soda lime is not exhausted and is tightly sealed.

5. Bag – no new leaks in the bag, and the correct size bag is being used for this patient.

Second – Check Patient6. Patient’s anesthetic plane was not compromised by shallow

respiration (Bauer, 2010, pp. 8-16).

The veterinarian has just entered the abdominal cavity through a ventral midline incision. You notice the dog appears to be

lightening up and is responsive to painful stimuli.

Please describe the clinical signs associated with excessive anesthetic depth.

• Decreased Respiratory Rate (< 12 RPM)• Bradycardia (<60 BPM)• Decreased SPO2 (<95 SPO2)• Pale Mucus Membranes • Dilated Pupils

After performing the above assessment you decided to increase the percent delivery of isoflurane to 3.5%.

Unfortunately, you forget to turn down the vaporizer after resolving the arousal problem and the dog is now very

“deep”.

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First – decrease or turn off vaporizer. Second – bag patient with pure oxygen every

5 seconds until normal vitals return, and can safely get the patient back to stage 3, plane 1 or 2 anesthetic depth (Bauer, 2010, pp. 8-16).

Third – increase IV fluids to help increase patient’s blood pressure.

What immediate steps should you take to correct excessively deep anesthesia?

The animal’s depth of anesthesia is determined by evaluating reflexes without using any equipment, and response of vital signs to surgical stimulation using equipment such as heart rate and respiratory rate monitors.

1. Swallowing – monitored by observing movement in the ventral neck. This shows that the animal is too light under anesthesia. If not shown, animal is in a moderate plane.

2. Pedal – Notice by pinching a digit and observing whether the animal flexes the leg or withdraws the paw. Due to this being lost during inductions, if the animal shows this reflex, it is too light under anesthesia.

3. Palpeberal – Tested by lightly tapping the medial cantus of the eye and observing whether the animal blinks in response.

4. Corneal – Obtained by gentle palpation of the lateral aspect of the cornea which causes reflex closure of the eyelids. Not always reliable in a dog.

5. Lacrimation - Tear formation

After the surgery is complete, a vet assistant asks you, “How did you know when the dog was too light or too deep?”

Please explain the common indicators (that do not require monitoring equipment) used to determine anesthetic depth.

6. Laryngeal – Stimulated by attempting to pass an endotracheal tube. Disappears in light anesthesia.

7. Pupillary Responses – Heavily influenced by pre-medication. In an un-premedicated patient, the pupil is dilated in the early excitement phase and then becomes progressively constricted as surgical anesthesia occurs. With very deep surgical anesthesia the pupil begins to dilate again and with entry into phase 4, with respiratory and cardiac arrest, the pupil is maximally dialated.

8. Muscle Relaxation

Continued…

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Five Stages of Anesthesia1. lost Not anesthetized2. Excitatory phase, loss of consciousness3. Surgical Anesthesia

Plane 1 – Light anesthesia. Palpebral reflex is present.Plane 2 – Moderate anesthesia. Adequate for all procedures. Laryngeal reflexes are lost.Plane 3 – Deep Anesthesia. No lacrimation, cornea is dry. Animal is receiving too much anesthesia and should be lightened.

4. Overdose5. DeathThe swallowing reflex is usually last under a medium plane of

anesthesia.The pedal reflex is usually lost during induction.The palpebral reflex is during a light plane of anesthesia.

Now that the assistant knows the indicators, please describe how the indicators are affected by the depth of anesthesia (i.e., light, medium, deep).

White – Right Forelimb proximal to elbow Black – Left hind limb proximal to elbow Red – Left hind limb proximal to stifle Green – Right hind limb proximal to stifle Brown – Ventral chest above the heart

As part of your anesthetic monitoring protocol you will use electrocardiography. You have applied the five ECG

leads/electrodes to the dog. Please state the locations of the lead application

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Please state where you will apply each of the following colors: White, Black, Red, Green, and Brown. White-Proximal to the elbow

on the right forelimb. Black-Proximal to the elbow

on the left forelimb. Green-Proximal to the stifle

right hind limb. Red-Proximal to the stifle left

hind limb Brown-Ventral chest above the

heart.

Unfortunately the above leads are color coded only; there is no visible writing on the leads. At some point in time, you

intended to label the leads but today you must rely upon the color coding system.

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What is a PVC? What are common causes of PVC? A PVC is a beat originating from

ventricles instead of the SA node, causing the ventricles to contract before the atria, and resulting in a decrease in the amount of blood pumped to the body (Romich 2010).

PVCs can be caused by heart disease, drugs, hypoxia, acid-base or electrolyte disorders (Thomas 2011).

PVCs can also be caused by restrain of a fearful animal. This can cause epinephrine release and cause a PVC (Thomas 2011).

PVC is something that would be seen in this case due to the acid-base imbalance, and once the stomach is untwisted could cause epinephrine release in the patient.

Twenty minutes into the surgery you notice a PVC . “Classic Looking”

PVC

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What is the medical term for this phenomenon?

Premature Ventricular Contractions is the medical term for PVC.

Lidocaine 1% 0r 2% most commonly used.

Used because it depresses myocardial excitability.

Used IV to control or treat PVCs and ventricular tachycardia.

Side effects are rare (Romich 2010). Procainamide, tocainide, and

mexiletine can be used but can cause ataxia, unsteadyness, vomiting, diarrhea, hypotension and weakness.

In this case the other medications would not be recommended because of side effects.

You are examining the ECG tracing. You notice four consecutive PVCs.

What drug is most commonly used to treat this condition?

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How many mL of fluid will the dog receive during the first hour of anesthesia?

Conversion Formula:

Wt(lb) x 1kg/2.2lb x mL/kg/hr = Answer in mL/hr

Conversion with animals weight in pounds:

150 lb x 1kg/2.2 lb = 68.2 kg 68.2 kg x 1mL/1kg/1hr=682

mL/1 hr

You are currently administering IV fluids at a rate of 10 mg/mL/hr. The dog weight is 150 lbs.

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You are using a drip set which has a conversion of 10 drops/mL. What is the correct drip rate

(drops/sec.)?

Conversion Formula:• mL/hr x 1hr/60 min. x gtt/mL =

Answer in gtt/min.• gtt/min. x 1 min./60 sec. =

Answer in gtt/sec.

Conversion with patients calculated amount of fluids.

• 682 mL/hr x 1 hr/60 min. x 10 gtt/mL = 114 gtt/min.

• 114 gtt/min. x 1 min./60 sec. = 2 gtt/sec.

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The patient recovered from surgery very well and will remain in the clinic for the next 3-7 days for observation. GDV surgery is an extremely severe condition and the patient is lucky the client brought him to the clinic in time. When the patient is stable enough to go home the client can take him home.

Conclusion

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Anesthesia Monitoring.(2015, January 1). Retrieved February 23, 2015, from http://www.ruralaeavet.org/PDF/Anesthesia-Patient_Monitoring.pdf

Bauer, M., (2010). Anesthesia. In The Veterinary Technician’s Pocket Partner. (pp. 8-16.Clifton Park, NY, Delmar Cengage Learning. Print

Ettinger, S.J., Feldma, E.C..Textbook of Veterinary Internal Medicine.W.B. Saunders, Philadelphia. Print

Romich, Janet, A.(2010).Fundamentals of Pharmacology for Veterinary Technicians Second Edition.Delmar, Cengage Learning. Print

Thomas, J., A., Lerche, P.,(2011).Anesthesia and Analgesia for Veterinary Technicians Fourth Edition. St. Louis, MO, Mosby Elsevier. Print

References