Small Animal Benchmark May 2013

Transcription

1 Small Animal Benchmark May 2013 A 5-year-old MC yellow Laborador Retriever (35 kg) is referred for management of the burn injury depicted below. This injury was suspected to have been sustained from prolonged direct contact with an electrical heating pad during right tibial plateau-leveling osteotomy performed at another hospital 5 days prior to referral. The burn became noticeable to the owner approximately 72 hours after the TPLO surgery, following a day during which the dog was hypersensitive over the affected area. The referral veterinarian performed initial wound debridement, placed a wet-to-dry bandage, administered 0.1 mg/kg Oxymorphone IV, and referred the patient to you. The owners report that the dog has been lethargic and anorexic since they brought him home the morning following TPLO surgery. On examination, the dog was assessed as 8% dehydrated; physical examination (P.E.) perfusion parameters were normal with the exception of heart rate (150 BPM). Systolic blood pressure was 150 mm Hg, and rectal temperature was F. The tachycardia was attributed to pain, as the dog additionally was reluctant to walk and whined at any manipulation near the burn injury. Other differentials for the tachycardia included fever/hyperthermia, hypovolemia and SIRS/sepsis. No other significant P.E. findings were noted. Upon exposure and evaluation, the burn injury appeared to involve both the epidermis and dermis with extension into the subcutaneous tissue, and to involve approximately 25% of the total body surface area (TBSA). Following initial debridement and eschar removal (at the rdvm), the majority of the burn injury demonstrated a healthy granulation bed; there were, however, several areas of questionable tissue viability

2 Outline the criteria for the two currently-favored methods of burn classification listed below. A) Depth of tissue destruction: B) Total body surface area (TBSA): How would you classify this dog s burns as far as depth of tissue destruction? What are the definitions of local burn injury and severe burn injury (SBI)? In one sentence, what is the significance of classifying a burn as local versus severe (or in other words, what are the major differences between these two categories)?

3 Complete the following chart referable to homeostatic alterations that accompany SBI: Resuscitation Phase (hypodynamic/ebb) Hyperdynamic Phase (hyperdynamic and hypermetabolic/flow) Time after injury Change in cardiac output (CO) Causes for CO changes Vascular permeability Primary mediators What are the roles of caspases and MIF (macrophage migration inhibitory factor) in the cardiac output alterations that characterize the resuscitation phase of SBI?

4 An 18-gauge peripheral catheter was placed in the left cephalic vein and an emergency venous data base was collected: PCV 65 % % TP 4.0 g/dl g/dl Na mmol/l mmol/l K + 5 mmol/l mmol/l Cl mmol/l mmol/l Glu 110 mg/dl mg/dl Lac 4 mmol/l mmol/l ph 7.26 PvCO 2 45 mm Hg mm Hg HCO 3 18 mmol/l mmol/l BE -8 mmol/l -4-4 mmol/l CBC and coagulogram were also evaluated and were within normal limits. Outline your initial fluid plan. Provide an evidence-based argument for the singular or combined use of the following fluid types in victims of SBI: isotonic crystalloids; natural and synthetic colloids; and hypertonic crystalloids.

5 List and briefly describe the 3 classifications of burn pain. Outline your analgesic plan for this dog. Include in your answer both mechanisms of action and dosages for any drug/s chosen.

6 Complete the following chart pertaining to methods of wound debridement: Method Agent Advantage (1) Disadvantage (1) Surgical Enzymatic Mechanical/ bandage Interactive dressings Larval

7 All of the following therapies have reported efficacy in burn victims. Provide the mechanism/s of action for each therapeutic intervention listed below: Sugar Honey Nanocrystalline Silver Dressing (NSD)

8 Hyperbaric Oxygen Therapy (HBOT) Vacuum Assisted Closure (VAC)

9 Intraabdominal hypertension (IAH) and abdominal compartment syndrome (ACS) are common sequelae to SBI in people. Define ACS. Differentiate among primary, secondary and tertiary ACS. List 10 risk factors for IAH and ACS. List and briefly describe 4 organ dysfunctions that can occur associated with ACS. You elect to measure IAP in your patient with SBI. Outline the technique you will utilize to obtain such a measurement.

10 This dog s IAP was measured 3 times an hour apart and pressures were 18, 22 and 20 mm Hg, respectively. Concurrent mean arterial pressure was 60 mm Hg. What is normal IAP in dogs? Given your answer, does this dog have IAH? What is this patient s abdominal perfusion pressure (APP)? Is this APP normal? List 5 medical strategies that can be employed in patients with ACS to decrease IAP. Over the course of the next 3 days, daily wound debridement and bandage changes were supervised by the soft tissue surgeon in preparation for delayed primary closure (see photographs included below.) List and briefly describe the 3 (or 4) phases of wound healing. What are 5 contraindications to primary wound closure.

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12 In addition to daily wound management, over the next several days your burn patient was treated with a combination of isotonic crystalloids and synthetic colloids, analgesics, anxiolytics as needed, prokinetics, and antiemetics (for perceived nausea and several episodes of vomiting). On day 3 the decision was made to place a multi-lumen central venous (jugular) catheter and start the dog on a total nutrient admixture. On day 5 of hospitalization, your morning P.E. revealed recurrence of tachycardia (HR 160 BPM, sinus on EKG), hyperdynamic femoral pulses, and a rectal temperature of 104 F. A CBC was submitted to further investigate the patient s new elevation in body temperature and revealed the following abnormalities: Result Reference Range WBC K/uL NEUTROPHIL SEG % NEUTROPHIL BANDS % ABSOLUTE NEUTROPHIL SEG /ul ABSOLUTE NEUTROPHIL BAND /ul REMARKS Neutrophils appears moderately toxic Provide a definition for nosocomial infection and list the 4 main sites of this type of infection in human (and likely veterinarian) patients.

13 You suspected a blood stream infection (BSI) in your patient, which was confirmed when Staphylococcus aureus was cultured from both the dog s blood and central venous catheter (CVC). List 5 other organisms that have been associated with catheter-related blood stream (CRBSI) infections in dogs. List at least 5 risk factors associated with nosocomial CRBSI. List 5 management strategies recommended to reduce the incidence of BSI in hospitalized patients. Following replacement of the dog s CVC, a 20 ml/kg bolus of isotonic crystalloids and antibiotics selected based on available susceptibility data (Cefotaxime, 50 mg/kg IV QID) were administered. However, the dog s heart rate remained elevated (HR BPM, sinus on EKG) and P.E. on the morning of day 6 revealed some new and alarming problems: depression; cold mucous membranes and extremities; poor pulse quality and a rectal temperature of 98.8 F. The dog s indirect blood pressure (BP) measured 85/40 mm Hg with a mean of 55 mm Hg; urine output dropped from 2ml/kg/hour to 0.4ml/kg/hour over a 4-hour period of time. Central venous pressure (CVP) was being continuously measured and remained constant at 6 mm Hg. The decision was made to administer an additional fluid bolus to challenge this patient.

14 Describe how the CVP can be used to determine if the patient s hypotension is due to hypovolemia? Briefly discuss the controversy surrounding the use of CVP in determining preload and/or predicting response to a fluid challenge After your fluid bolus the BP remained unchanged, the CVP increased to 8 mm Hg and remained there for over 30 minutes. List possible causes of this patient s persistent hypotension.

15 To evaluate the dog s cardiac function an echocardiogram was performed and the following image was obtained: What mode of echocardiography is depicted in the main picture? Calculate the fraction shortening, showing calculations. What is the most likely diagnosis and therefore cause of this dog s hypotension and why (assume the patient has no previous cardiac abnormalities)? Briefly describe the following concepts as they pertain to the diagnosis obtained above: a) Timing of cardiac changes and recovery

16 b) Coronary blood flow c) Myocardial depressant factor d) Mitochondrial dysfunction e) Intracellular calcium

17 f) β receptor hypo responsiveness List 3 drugs that could be used to improve cardiac contractility in this patient and outline their mechanism/s of action. 12 hours after initiating inotropic therapy, the dog s indirect BP had improved (120/80 with a mean of 74). Urine output remained at 0.4 ml/kg/hr. Outline the RIFLE and AKIN criteria for acute kidney injury (AKI) and classify this dog s AKI according to these criteria.

18 What effect does this AKI classification have on the patient s prognosis? Biomarkers have been widely investigated in the human critical care arena. Define what is meant by the term biomarker and describe how biomarkers can be clinically applied to patients with suspected and/or confirmed AKI? Below are 3 biomarkers of renal tubular injury. Briefly provide the rationale behind the measurement of each in critically ill (human) patients. Neutrophil gelatinase-associated lipocalin (NGAL): Kidney Injury Molecule-1 (KIM-1): Cystatin-C:

19 Forty-eight hours after initiating appropriate antibiotic therapy, treatment with selected inotropes at appropriate dosages and continued (and then tapering) intravenous fluid therapy and parenteral nutrition, analgesics and other supportive measures, your patient s hemodynamic status (including urine output [and both RIFLE and AKIN stages]) normalized and his clinical status began to improve daily. His burn injury was primarily closed (>90%) on day 10 of hospitalization (see photographs below). A repeat echocardiogram on the same day revealed marked improvement in systolic function. He was discharged 11 days after presentation and is normal today.

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