2016 FALL: Cardiopulmonary Arrest | Chocolate Toxicity | Ophthalmic Emergencies | Meet Anesthesiologist Tiffany Granone | Meet Dr. Lana Rothenburg, Internal Medicine
Cardiopulmonary arrest (CPA) is the abrupt and complete failure of the respiratory and circulatory systems, which leads to cessation of blood flow, tissue hypoxia and cell death. Studies have reported survival to discharge rates ranging from 3 – 6% in dogs and 2.3 – 9.6% in cats. Animals that arrest under general anesthesia have the greatest likelihood of regaining return of spontaneous circulation (ROSC) and survival to discharge. With such grim success rates, it is important to identify predisposing causes of CPA in an attempt to treat the underlying cause and ward off impending arrest. Some predisposing factors include hypovolemia, hypoxemia, acidosis, hypo- or hyperkalemia, hypo- or hyperthermia, toxins, trauma, tamponade and pneumothorax.
In the event of an arrest, preparedness of the veterinary team is of utmost importance. A readily available, well-stocked (routinely audited) crash cart located in patient care areas is recommended. Effective communication through designation of a team leader with delegated tasks to individual team members will ensure that protocol is followed. Debriefing staff on CPR performance, problems involving equipment or drugs, or other issues that may arise can improve the overall quality and potential outcome of future codes.
Basic life support (BLS) involves the recognition of CPA, initiation of chest compressions, airway management, and the provision of ventilation.
One of the greatest factors in CPA outcome is the quality of chest compressions. The vast difference in size and conformation of thoracic cages of our patients precludes recommendations for hand position at a single location. For cats, small dogs and keel-chested dogs, the preferred method is the cardiac pump mechanism, in which hands are placed directly over the heart. In medium to giant breed dogs with rounded chests, direct compression over the heart is unlikely to be effective. Recommended for these animals is the thoracic pump mechanism, where compressions are delivered over the widest portion of the thorax. The thoracic pump mechanism relies upon alterations in intrathoracic pressure to create forward flow. During thoracic compression there is an increased intrathoracic pressure, which causes a secondary compression of the aorta and vena cava leading to blood flow out of the thorax. During elastic recoil of the chest wall, the intrathoracic pressure becomes negative acting as a vacuum drawing blood from the periphery back into the thorax.
Recommended compression rate is 100-120/min in dogs and cats. Compressions should be performed by a person standing above the patient, with the elbows locked, bending at the waist. Compression depth of 1/3– ½ the width of the thorax in a 1:1 compression:relaxation ratio, permitting full elastic recoil of the chest is the key to good form. Recognition of compressor fatigue is important, as rate and depth of chest compressions decrease over time. Chest compressions should be performed for 2 minutes, unless signs of fatigue are recognized.
Ideally, ventilation is provided through endotracheal intubation. Non-invasive techniques such as mouth-to-snout or a tight fitting mask may be acceptable alternatives. Ventilation rates are recommended at 10 breaths per minute, 10 ml/kg tidal volume, and 1 second inspiratory time. Increased respiratory rates, tidal volumes and inspiratory times can lead to increased intrathoracic pressure, decreased venous return and decreased perfusion.
Advanced life support (ALS) includes vasopressor therapy, positive inotropes, anticholinergics, electrical defibrillation, antiarrhythmics and other miscellaneous interventions including correction of acid-base and electrolyte disorders and resolution of volume deficits.
Drug therapy is a staple of ALS. Epinephrine and vasopressin are the most common vasopressors used during CPR. Vasopressor therapy increases systemic vascular resistance increasing the cardiac output that remains within central circulation. Two doses of epinephrine have been reported for the treatment of CPA, the low dose (0.01 mg/kg IV) and the high dose (0.1 mg/kg IV) dosed every 3-5 minutes. Although the high dose has been associated with increased ROSC, it does not necessarily increase survival to discharge. High dose epinephrine may be considered for repeat dosing or prolonged CPR. Vasopressin, a nonadrenergic vasopressor, acts on vascular smooth muscle. The benefits of this drug as a vasopressor include efficacy in the face of acidosis and no inotropic or chronotropic effects, which may worsen myocardial ischemia. Epinephrine and vasopressin may be used interchangeably. Increased vagal tone is thought to be a predisposing condition to CPA in small animal veterinary patients. Routine use of atropine (0.04 mg/kg IV) in dogs and cats can be considered.
The most common arrest rhythms identified in veterinary patients include asystole, pulseless electrical activity (PEA) and ventricular fibrillation (VF). There is no proven drug therapy for asystole or PEA. Electrical defibrillation is the most effective therapy against VF and pulseless ventricular tachycardia (VT). Antiarrhythmic agents, including amiodarone, lidocaine and magnesium, have been investigated for the treatment of VF/pulseless VT. Amiodarone is the only drug that has consistently demonstrated a benefit in these cases. Lidocaine is an alternative if amiodarone is not available, but it may increase the defibrillation threshold for conversion. There is insufficient evidence to support the routine use of magnesium.
Other drug therapies to consider during CPA include reversal agents, electrolyte therapy, alkalinization therapy and corticosteroids. Reversal agents such as naloxone, flumazenil or yohimbine/atipamezole can be administered if there is reason to believe that its counterpart drug played a role in the patient’s arrest. In the face of documented ionized hypocalcemia administration of Ca2+ may be beneficial in skeletal and smooth muscle function. Hypokalemia should be documented prior to treatment with potassium-containing drugs. Sodium bicarbonate (NaHCO3) therapy is not recommended for routine use during CPR. Corticosteroids have been investigated in both experimental and clinical studies. There is no demonstrated benefit from corticosteroids, and there is a potential for harm following high-dose administration. Thus, the routine use of steroids is not advised. IV fluids are only indicated in hypovolemic patients.
Monitoring during CPR should include ECG and ETCO2. ETCO2 can be used as an early indicator of ROSC as it assesses perfusion of the alveolus rather than ventilation. Dogs whose ETCO2 > 15 mmHg and cats ETCO2 > 20 mmHg may have an increased rate of ROSC. Electocardiographic monitoring during intercycle pauses of chest compression will allow for appropriate ALS therapy based upon rhythm diagnosis. However, chest compressions should not be stopped to assess the ECG in between theses cycles. Palpation of pulses is not an effective means of monitoring during CPR. Chest compressions should not be held so one can attempt to palpate pulses. Corneal Doppler is not recommended because it can be complicated by motion artifact and retrograde venous flow.
Following a successful resuscitation, intensive care is required. Patients should be optimized hemodynamically, respiratory function managed in an effort to target normoxia and normocapnia, and interventions provided to protect neurologic function.
If you have any questions or would like to learn more about the ACVECC RECOVER initiative, please contact our clinical manager, Natalie Clawson, RVT, email@example.com or 405.749.6989.
We’d like to thank our colleague from BluePearl in Tennessee, Andrea Monnig, DVM, DACVECC, for allowing us to use this article for Companion.
- Theobromine inhibits phosphodiesterase, causing increased cAMP and increased catecholamines.
- Caffeine is a direct myocardial/CNS stimulant.
|Type of Chocolate||Theobromine
*The low end of the range applies to instant mixes; the high end of the range is for baking chocolate.
1 ounce = 28.4 grams
16 ounces = 1 pound
Signs of theobromine toxicity can present at these amounts of ingestion:
|Mild signs||20 mg/kg|
Lethal doses of caffeine can occur at 150 mg/kg in dogs, cats and humans.
Hx: Chocolate usually presents as a known toxin. It is important to confirm time of consumption, type, quantity (in ounces, ideally), baked good product versus candy.
S/O: Early signs may include vomiting, hyperexcitability, diarrhea. Severe toxicity may include arrhythmias and CNS signs.
Induce vomiting, unless already presenting.
- Apomorphine 0.04 mg/kg IV
- Activated charcoal (avoid sorbitol due to anticipated diarrhea) PO q6h (enterohepatic recirculation)
Hospitalize for monitoring and IV fluids administration. Encourage frequent urination.
For moderate to severe cases:
Place urinary catheter to empty bladder to prevent reabsorption.
ECG monitoring for severe tachyarrhythmia (propanolol, etc.)
For seizure prevention and management – diazepam/midazolam prn, (antagonism of benzoreceptors, decrease efficacy)
For support with toxicities, please contact our emergency service 24/7.
A Sight for Sore Eyes: Ophthalmic Emergencies
Proptosis, “eye out of the socket,” is the forward displacement of the globe out of the orbit with subsequent entrapment of the eyelids behind the eye. It occurs due to trauma to the head, usually a dog fight. Dogs with wide eyes and shallow orbits are at higher risk. Cats and long-nosed dogs require very severe trauma for the eye to proptose.
Factors to consider before replacing the eye into the orbit:
- Time elapsed since injury
- How many extraocular muscles are ruptured (no more than three)
- Presence of hyphema
- Whether or not the the globe is soft
Because more than three extraocular muscles are ruptured, compromising the globe arterial supply, this eye must be enucleated.
If the decision is made to replace the globe in the orbit, it should be done immediately. The patient should be stable enough for a short period of general anesthesia. After the area is prepped (recommend minimal clipping, trim long hairs with scissors and use betadine solution 1:50 dilution only – betadine scrub and chlorhexidine should never be used near the globe), infiltrate the lateral canthus with local anesthesia, then perform a lateral canthotomy if needed. Depending on the size of the palpebral fissure, lateral canthotomy may not be required. This will enlarge the palpebral fissure immediately and allow grasping of the skin on the upper and lower eyelids with Allis forceps; pull gently up and over the globe. Once the eyelids are manipulated over the globe, the eye returns to the orbit. Suture the lateral canthotomy and place a temporary tarsorrhaphy to protect the globe during the first two weeks postsurgery. Topical antibiotic, oral analgesia and anti-inflammatories are in order.
Postoperative deviation of the globe occurs due to rupture of extraocular muscles. Strabismus often diminishes over weeks to months.
Glaucoma, increased pressure within the eye beyond that compatible with normal ocular function, vision and comfort, is one of the leading causes of blindness in animals and people. It is caused by a disturbance in the flow of fluid within and out of the globe. Once one eye has been affected by primary glaucoma, the second eye will normally be affected within two years. Other causes of glaucoma include inflammation, trauma and intraocular tumors. Glaucoma patients often present with a painful eye and decreased vision. Other presenting complaints include injected conjunctival and episcleral vessels, gray uneven discoloration of the cornea, mid-range mydriatic pupil and elevated intraocular pressure. Glaucoma is one of the ophthalmic conditions with severe visual implications and should be referred to a veterinary ophthalmologist for further management. It is rarely cured, and many animals lose vision despite medical and surgical treatment.
An accurate diagnosis of glaucoma is based on a thorough ocular examination and measurement of the intraocular pressure (IOP) with a tonometer. Normal IOP should be lower than 20-25 mmHg. Acute glaucoma is an ophthalmic emergency and must be treated immediately! If the pressure remains elevated for a few hours, permanent vision loss occurs. The combination of the carbonic anhydrase inhibitor, dorzolamide, and a beta blocker, timolol, works very well together with the prostaglandin analogue, latanoprost.
Lens luxation into the anterior chamber may be seen with elevated intraocular pressure or not. It is a true ophthalmic emergency that requires surgery. Prompt surgical removal of the luxated lens is recommended if prognosis for vision is good.
The normal lens position is behind the pupil. When luxation occurs the lens may be displaced completely in front of the pupil (anterior luxation) or behind the pupil to the back of the eye (posterior luxation). The luxation can also be partial (incomplete or subluxation). Lens luxation is observed in young adult dogs usually 4 – 5 years of age. Primary lens luxation is common in terrier breeds such as the wirehaired fox terrier, Jack Russell terrier, Sealyham terrier, Tibetan terrier and terrier crosses. The breeds predisposed to this condition are border collie, Australian blue heeler, German shepherd dog and Shar Pei. Primary lens luxation is bilateral, although the onset of luxation varies between the eyes. Secondary lens luxation and subluxation may occur after the globe has increased in size (buphthalmia) in glaucoma cases or after chronic intraocular inflammation (uveitis, cataracts).
Superficial corneal ulcer. Notice the positive fluorescein uptake on the stroma and between the stroma and the epithelium at the ulcer margin.
A deep corneal ulcer, descemetocele, progressed from a superficial ulcer.
Anterior lens luxation usually manifests with acute tearing (epiphora) and eye pain and redness. Cloudiness of the cornea is present if the intraocular pressure is elevated (glaucoma). If the cornea is clear, the luxated lens can be observed in front of the pupil. The luxated lens can migrate back and forth through the pupil.
Corneal ulcers start as simple superficial ulcers that become deeper. One should be worried if the ulcer is deep (descemetocele) and there is a risk of rupturing. Topical antibiotics and pain management, topical atropine, oral analgesics and anti-inflammatories, are recommended. Use of an E-collar is also recommended. An uncomplicated ulcer should heal within 7 to 10 days. If healing takes longer, the ulcer may be indolent and require debridement and grid keratotomy.
Corneal abscesses occur when a corneal ulcer becomes infiltrated by bacteria. The corneal stroma may be greenish yellow and become malacic or gelatinous. Bacteria such as P. aeruginosa and S. betahemolyticus are involved in progression of the ulcer. Clinical signs of a stromal abscess include increased tearing, severe ocular pain, redness and evidence of a whitish to yellow discoloration of the cornea.
A stromal abscess is an ocular emergency, although it may not require immediate intervention by an ophthalmologist. You can stabilize the eye by establishing strong, frequent (every 2 hours) topical antibiotic therapy (quinolones), anticollagenases (serum, EDTA), systemic antibiotics (Clavamox® or Unasyn®) and analgesia. It is often necessary to admit these patients for 24 hours. Surgical repair of the cornea (conjunctival flap) may be necessary if the ulcer progresses to deep layers, and the eye is at risk of perforation or has already perforated.
Infected anterior stromal corneal ulcer with collagenolysis
Uveitis occurs when the uveal tract, rich in vascularization, becomes inflamed. Protein, red and white blood cells leak to the usually transparent intraocular fluid, making it turbid. The condition may be present in one or both eyes. Bilateral involvement is seen more frequently in patients with infectious, parasitic, neoplastic or autoimmune diseases.
There are many causes of uveitis; it is frequently considered an ocular manifestation of a systemic disease. Among the causes are trauma, cataract formation, infections and tumors. Some of the infections in dogs include Rocky Mountain spotted fever, Lyme disease, ehrlichiosis, anaplasmosis, infected uterus, viral hepatitis and systemic fungal infections. In cats the causes include feline leukemia virus (FeLV), feline immune deficiency virus (FIV), feline infectious peritonitis (FIP), toxoplasmosis and bartonellosis.
Symptoms of uveitis include eye pain, squinting, redness, tearing, elevation of the third eyelid, cloudiness of the cornea and a small pupil. On occasions there is pus or blood inside the eye.
Diagnosis of uveitis requires a complete systemic workup to include blood and urine testing and thorax and abdomen imaging; however, approximately 60% of the cases are a diagnosis of exclusion. Possible sequela include attachment of the pupillary opening to the lens capsule (posterior synechiae) which can result in abnormal pupil shape (dyscoria), secondary glaucoma (high intraocular pressure), secondary cataract formation and retinal detachment. The eye may become blind and painful in which case surgical removal (enucleation) will be recommended. Emergency treatment should include topical eye medication to control intraocular inflammation, analgesia, systemic anti-inflammatories and antibiotics, and possibly medications to prevent glaucoma. If there are no corneal ulcers prednisolone acetate and atropine are recommended.
Our board-certified ophthalmologists, Dr. Kevin Donnelly and Dr. Jeff Studer, are on call 7 days a week through our emergency room. If you have an ophthalmic emergency, please contact our hospital at 405.749.6989.
Article courtesy of our colleague from BluePearl in Massachusetts, Clara Williams, DVM, DACVO.
FROM THE MEDICAL DIRECTOR
Hopefully you have recovered from the busy and hot summer and are enjoying the cooler temperatures. Fall is definitely my favorite time of year! Here at BluePearl, we are very excited about the coming months and the changes that they promise.
Many of you have had the opportunity to meet our two newest clinicians, Dr. Tiffany Granone, board certified in anesthesiology and pain management, and Dr. Lana Rothenburg from our internal medicine service. If you have not, please feel free to reach out and welcome them to our community. You will find a brief bio of each in this newsletter.
The construction of our new hospital continues to progress nicely, and we are hoping for completion the beginning of 2017. This is a very exciting process for us as we anxiously await having our entire team under one roof. We are also excited about the expanded space that will allow us to provide your clients with a more comfortable visit.
We continue to provide CE opportunities for you and your team. On November 3, Dr. Lana Rothenburg will be discussing advances in immune-mediated hemolytic anemia. Visit the Oklahoma page of our website, bluepearlvet.com, for information on other upcoming continuing education events.
Please do not hesitate to contact me if you have any questions or concerns.
Jeff Studer, DVM, DACVO
Meet our specialist…
Tiffany Granone, DVM, MS, DACVAA
Anesthesiology and Pain Management
Tiffany Granone, DVM, MS, DACVAA
Dr. Tiffany Granone completed her residency and a master’s degree in comparative anesthesia at the University of Minnesota and her internship at Ontario Veterinary College. She chose the anesthesiology specialty because it allowed her to work with a wide variety of species putting into practice the combination of physiology and pharmacology. She has a particular interest in anesthesia in the critically ill patient. Outside the hospital, Dr. Granone enjoys cooking and exploring different local restaurants as well as fishing, exploring the outdoors and boating.
Was there a vet school course or professor that changed the direction of your career?
As a fourth year veterinary student doing my clinical rotations at Oregon State University, one of the anesthesiologists I had the opportunity to work with helped pave my career path. In an area of veterinary medicine which is often confronted with fear and nervousness, she taught me how to be strong, yet compassionate, how to face tough cases that might evoke fear with knowledge and courage, and how to remain resilient and steadfast even in the face of challenges.
What keeps you interested in cases day-after-day?
Knowing that no two patients are alike and tailoring the care that each patient receives to their individual needs makes each and every case interesting. Instead of taking a “cookbook” approach to the care of patients, I enjoy learning about each patient so that I can determine the best approach to their care. Knowing that every day brings something new keeps me excited.
Was there a case that taught you something meaningful about yourself and your practice?
A dachshund was brought into the hospital with extensive fractures to his hind limbs and pelvis, severe soft tissue wounds and a ruptured urethra after being run over by his owners. Unfortunately, his owners were unable to provide for him the care that he needed.
His prognosis was serious, and he had many doctors and staff that became part of his medical team. After multiple anesthetic events, numerous surgeries and months of hospitalization and rehab, that young little dachshund is able to run, play and enjoy life with his new family. This case reminds me that with a team of dedicated individuals, hard work and dedication to our patients, things that are seemingly impossible can have happy endings.
Lana Rothenburg, DVM, MSc
Internal Medicine Service
Lana Rothenburg, DVM, MSc
Dr. Lana Rothenburg grew up in Waterloo, Ontario, Canada and completed her undergraduate degree and a master’s degree at the University of Toronto. She worked as a research coordinator before attending veterinary school at Oklahoma State University. She completed her internship in Denver, Colorado and came back to Oklahoma State for her residency. Her professional interests include hematology, endocrine and immune-mediated disease. Outside of work, Dr. Rothenburg enjoys ashtanga yoga and spending time with her two rabbits and dog.
How do you go about helping ease the concerns of an upset client?
I think that knowledge is very important for clients struggling with a pet’s illness. I do my best to educate them regarding the relevant biology behind their pet’s disease, which then helps to explain the goals of any recommended tests or treatments. I also work to relate to my clients’ concerns and strive to give them the best advice possible as if their pet was mine.
How do you like to work with the primary care veterinarian?
I think a team-based approach to veterinary medicine is vital. Frequent communication and collaboration are a must for pets with complex diseases. After each visit, I will call and send a letter outlining our diagnostic efforts and treatment plan. After my patients leave the hospital I make myself available by phone or email to consult on cases through communication with the primary care veterinarian.
Tell us about a case that touched your heart.
Magic is just about the happiest Labrador retriever you will ever meet. I have treated her for the past two years, through multiple relapses of her immune-mediated neutropenia and associated secondary infections. Her case has required quite a bit of creativity and patience to battle two conflicting disease processes. During her two-year treatment, I have established a relationship with her family. They recently had to euthanize another dog that I had never met, and they requested that I perform the euthanasia because of the relationship that we formed. Magic and her family will always hold a special place in my heart and remind me of the importance of veterinarians in fostering the human-animal bond.
Is there a veterinary school course or professor that changed the direction of your career?
My pharmacology course in my second year of veterinary school was one of the first to combine theory with practice. Our professor made a point to include information from recent studies in her discussion of various drugs. This evidence-based approach to veterinary medicine is one that I will carry with me throughout my career.
BluePearl is strongly committed to the veterinary community. One of the ways we demonstrate this commitment is through our continuing education program, which is subsidized in part by our Partners in Education. Please check our online calendar regularly for the most current information about courses, dates and locations.
All lectures are free and include a light dinner 30 minutes prior to the lecture. Please RSVP to Joy Hardin at 405.749.6989 or firstname.lastname@example.org.
|November 3||7:00pm||Doctor||Advances in Immune-mediated Hemolytic Anemia
Lana Rothenburg, MSc, DVM
|Four Points Sheraton