Emergency Medicine Notes
.docEmergency Medicine Notes, p. 1 (TB's use at your own risk)
EMERGENCY MEDICINE Alpha versus beta effects Alpha = peripheral vasoconstriction Beta = peripheral vasodilation; heart stimulation; bronchodilation [BETA 1 VERSUS BETA 2????] Alpha and beta effects of sympathomimetic drugs Epinephrine 3+ beta, 3+ alpha Dopamine 3+ beta, 2+ alpha Norepinephrine 1+ beta, 3+ alpha Dobutamine 3+ beta, 1+ alpha Isoproterenol 3+ beta, 0 alpha 1. Best catecholamine to use in anaphylaxis Epinephrine. Good bronchodilator, good vasoconstrictor. Bronchoconstriction and vasodilation are major components of anaphylaxis. Dopamine is a strong beta, fair alpha. Good bronchodilation, no vasoconstriction. Not quite as good a choice as epinephrine. Norepinephrine is a weak beta, strong alpha. Good vasoconstriction, but no bronchodilation. 2. Best catecholamine to use in cardiac arrest Epinephrine best catecholamine to use in cardiac arresst. Good vasoconstrictor, good myocardial stimulant. Alpha agonist stimulates peripheral vasoconstriction, which redistributes blood into the central circulation and diminishes loss of blood volume into the periphery. Beta agonist stimulates pacemaker activity and enhances contractility when the heart is beating. Dose: 0.02 mg/kg. Can go up to 0.2 mg/kg, which actually is more efficacious, but higher doses can cause ventricular arrhythmias. It is better to start with a low dose and titrate with higher doses to effect. Dopamine and norepinephrine second choice. Never use isoproterenol in cardiac arrest. Potent vasodilator. 3. Worse catecholamine to use in cardiac arrest Isoproterenol. Potent vasodilator, no cardiac stimulation. 4. External CPR versus internal compression CPR External comprepssion first choice because it is easier and less stress on critical patient. Internal compression if external does not work. Internal compression achieves much better cardiac output parameters. Try external compression first because often you can get the heart started without splitting the chest. 5. Theories of mechanisms of forward blood flow during CPR Heart pump mechanism. Compress heart, AV valves close, pressure pushes blood forward into aorta. Release chest, venous pressure causes diastolic filling of heart. Thoracic pump mechanism. Pressurize chest, collapse anterior and posterior vena cava to prevent backfow of blood. Pressure moves blood forward out aorta. Release chest, venous pressure causes diastolic filling of the heart. 6. Indications / contraindications for use of bicarbonate during CPR Use is very controversial. Dr. Haskins strongly believes bicarbonate is indicated during CPR to offset malperfusion acidosis. Dose: 0.5 mEq/kg slowly every five minutes after the first 5 10 minutes. People (including people who write Board questions) believe bicarbonate is not indicated, because animals do not develop a metabolic acidosis sufficient to warrant bicarbonate therapy. Also, metabolism of bicarbonate results in formation of C02, which can result in hypercapnia if the animal is not ventilate well enough. This leads to paradoxical CSF acidosis. 7. Expected resuscitation rate of CPR in private practice Poor. At VMTH, 1/3 dogs restarted; 45% cats restarted. 1% long term survival. 8. Atropine versus glycopyrolate Glycopyrolate has a slower onset, lasts twice as long and is more potent. Atropine. Vagolytic. Atropine is an antimuscarinic which competetively inhibits acetylcholine. Uses: 1) preanesthetic to reduce respiratory tract secretions; 2) treat sinus bradycardia, sinoatrial arrest, incomplete AV block; 3) antidote for cholinergic overdose; 4) hypersialism; 5) treatment of bronchoconstrictive disease. Peak effect within 3 4 minutes. Dose: 0.02 mg/kg IV; 0.04 mg/kg IM Glycopyrolate. Same effects as atropine. Onset within 1 minute IV; 30 45 minutes SQ, IM. Vagolytic effects persist 2 3 hours. Dose: 0.01 mg/kg IV 8. Can atropine cause bradycardia Low dose atropine SQ can result in bradyarrhythmias and bradycardia. This is due to a centrally mediated increase in vagal tone that is earlier in onset than the peripheral blockage effect. 9. Dose of crystalloids during CPR One half to one blood volume. 10. Blood volumes of the various species Dog 90 ml/kg. Cat 40 ml/kg. Horse 70 ml/kg. 11. When use hypertonic saline 1) When you need a good volume effect in a short amount of time 2) Any large animal. 12. Problems associated with hypertonic saline Hemolysis, hypotension, arrhythmias. Also, hypernatremia, hyperchloremia, hyperosmolality, hypokalemia, hemoglobinuria, pain (in awake patient). 13. Use of Dextran 70 1) Hypoproteinemia; 2) Good volume effect with smaller volume of fluid. Dextran is a better volume expander because 80% remains in the vascular compartment, as compared with 25% with LRS. 14. Problems associated with Dextran 70 Bleeding problems. Interferes with platelet adhesivements, factor VIII activity and vWF. See poor platelet function, prolonged PTT and prolonged ACT. Not a common problem. Volume overload. Also possible. 15. Why is D5W not a very good blood volume expanding agent Too much redistributed to the interstitial and intracellular fluid compartment. Contraindicated for blood volume expansion therapy. 16. DSW isotonic or hypotonic Bottle says isotonic (actually 250). In body, glucose is metabolized and it acts like it is hypotonic. 17. Feline blood groups In USA, almost all cats are type A. Type B can occur more commonly in purebred cats, especially British Short Hair, Cornish Rex, and Devon Rex. Cats with type B have anti A in their serum and will hemolyze type A red blood cells and have acute transfusion reactions. Cats with type A rarely have type B antibody. 18. Canine blood groups Want a donor negative for DEA 1.1, 1.2 and 7. With first time transfusions, you can give multiple transfusions without cross matching up to 5 days until antibody formation. Autoimmune dogs have a lot of naturally occurring antibodies to red cell antigens. 19. Indications for blood transfusion PCV < 20. Real answer, when clinical signs show you that oxygen delivery is not adequate. 20. Signs of a transfusion reaction Typical anaphylactic reaction. Fever, restlessness, hypotension, nausea, vomiting, tachycardia, wheezing, dyspnea, urticaria, hemoglobinemia, hemoglobinuria. Hypocalcemia can also occur because transfused blood has a lot of citrate in it. Hypothermia if the blood is not warmed up. 21. Can you get a transfusion reaction with only plasma Yes. 22. Cross match if giving plasma Yes. Minor cross match, plasma plus recipient RBC. 23. Blood products to use for platelets If you need platelets, use fresh. Fresh whole blood, fresh plasma. Centrifugation and refrigeration kills platelets. Six hours is the definition of fresh. 24. Blood products to use for colloids If you only need colloids, you can give fresh, fresh frozen or stored plasma. Or you can give synthetic colloids. 25. PCV of packed cells 80. 26. Is Mannitol a crystalloid or colloid Molecular weight of mannitol is 180, small enough to diffuse across the endotheliam membrane. That makes it a crystalloid. The definition of a colloid is a molecule of sufficient size that it doesn't diffuse across the vascular endothelial membrane, 500,000 or greater. 27. Molecular weight of molecules that are glomerularlv filtered rapidly < 50,000. 28. Is Mannitol a hypervolemic agent or a hypovolemic agent Bolus mannitol is very hypervolemic agent because it pulls water out of the interstitial fluid compartment into the vascular space. As diuresis occurs, it becomes hypovolemic as water is pulled into the urine with the mannitol. 29. Problems that can occur with Mannitol 1) Dehydration and hypovolemia via osmotic diuresis; 2) Cerebral edema; pulmonary edema. 30. Is Mannitol contraindicated in head trauma In theory it is contraindicated. The theory is that mannitol will leak through broken blood vessels and draw more fluid into the cranial vault to make cerebral edema worse. However, the probably does not happen, since mannitol is given slowly over 20 minutes and is greatly diluted in the bloodstream. However, the answer on the boards is "True." 31. Causes of hypoxemia Three: 1) Low FI02; 2) hypoventilation; 3) venous admixture. 32. What is venous admixture Venous blood mixes with arterialized blood. Blood goes from right side of circulation to left side without being oxygenated. Due to a lung problem. 33. Types of venous admixture [LOOK UP] Low VQ; No VQ; Diffusion defect; anatomical shunt 34. Interpretation of blood gases [LOOK UP] 35. Fluid therapy 36. Corticosteroids in septic shock Depends on the study. Unknown if efficacious. 37. SIRS Systemic Inflammatory Response Syndrome. Anything that causes intravascular hemolysis. 53. What does SIADH mean Syndrome Of Inappropriate Andidiuretic Hormone Release. 54. Mechanism of ADH Decrease in sodium concentration. 55. DIC 56. How does potassium work as a pharmacological defibrillating agent Stops the heart. Repolarization is accomplished by diffusion of potassium out of the cell. If extracellular potassium is high, potassium cannot diffuse out and the cell will not repolarize. 57. How does calcium stop the effects of hyperkalemia Elevates the threshhold.