Jeff Baier MS DVM Birds of Prey Foundation Broomfield, CO

Transcription

1 Jeff Baier MS DVM Birds of Prey Foundation Broomfield, CO

2 Squamates Chelonians Snakes Lizards Varanids Monitor Lizards Crocodilians

3 Reptilian adaptations Anaerobic glycolysis Low metabolic rate Cardiovascular system Renal portal system

4 Based on aerobic metabolism reptiles are weaker than their mammalian counterparts Anaerobic glycolysis allows reptiles to exceed the strength of mammals for periods of time

5 Aerobic metabolism 70 kg human is five times stronger than 700 kg crocodilian Anaerobic metabolism Allows crocodilian to develop the strength of 20 humans

6 Anaerobic metabolism allows for the quick utilization of stored energy Lactic acid is produced No carbon dioxide is produced

7 Reptiles may utilized anaerobic metabolism when hospitalized Physical examination Restraint for diagnostic sampling

8 Fluid replacement considerations Patient likely to have significant lactate levels Fluid replacement using fluids containing lactate may be contraindicated

9 Suggestions for fluid replacement 2.5% Dextrose in 0.45% Saline Mixture of equal parts 5% Dextrose with Normosol

10 Suggestions for fluid replacement Slightly hypotonic fluids may be preferred Reptiles have higher intracellular volumes and lower plasma volume than mammals Replacement of intracellular volume appears to be important.

11 Metabolic rate is not constant for all reptilian species Trends As the size of the animal increases metabolic rate decreases Alligators have lower metabolic rate than anoles Cattle have lower metabolic rate than shrews

12 Trends As an individual grows and ages the metabolic rate decreases Neonates have higher metabolic rates than adults

13 Generally the metabolic rate of reptiles is lower than that of mammals of considerable size

14 Differences in metabolic rate Mammals Body temperature is constant Body temperature maintained internally

15 Differences in metabolic rate Reptiles Body temperature is not constant Body temperature maintained by a combination of metabolic heat and environmental heat

16 Activity temperature range Range of temperatures in which a reptilian species conducts normal activities At or above the upper limit animals cannot survive At or below lower limit animals can survive, if proper conditions exist

17 Within the activity temperature range for a species the animal will be able to maintain its preferred body temperature The temperature at which all physiological functions are optimal

18 Temperature preferences and disease state Reptiles in acute stages tend to seek out warm areas in their environment Reptiles in chronic stages of disease tend to seek out cooler areas in their environment

19 Metabolic rate and induction of anesthesia Induction with inhalant anesthetics is a slow process Respiration may be slowed due to presence of anesthetic agent Respiration may be slowed due to the high oxygen content

20 Oxygen consumption increases with temperature

21 Stroke volume in iguanas decreases as temperature increases Heart rate and oxygen delivery to tissues increases to compensate

22 Organ perfusion Perfusion of heart and kidney increase with temperature Once activity temperature range is exceeded, perfusion to these organs decreases

23 Antibiotics Volume of distribution Clearance rate MIC

24 Digestion Rate of passage Nutrient absorption, assimilation and utilization

25 Preferred body temperature Typically O C Maintained through physical, behavioral and physiological factors Preferred activity range

26 Acid-Base Balance ph varies inversely with temperature

27 Water regulation Increased ambient temperature increases water loss

28 Adaptations of the cardiovascular system have allowed snakes to become a highly successful group Snakes utilize terrestrial, arboreal and aquatic habitats

29 Three Chambers Atria Left - filled by sinus venousum Right - filled by pulmonary veins Ventricle Subdivided into 3 interconnecting cava

30 Ventricular Cava Cavum arteriosum supplies blood to systemic circuit Cavum pulmonale supplied blood to pulmonary circuit Cavum venosum interconnects the c. arteriosum and c. pulmonale

31 The ventricle is considered a single pressure pump Pressure in each of the cava is equal during systole

32 Squamates - systemic and pulmonary circuits are in parallel arrangement Mammals - systemic and pulmonary circuits are in series

33 Cavum venousum reduced Admixture and intracardiac shunting of blood still possible Functions similar to mammalian heart

34 Right to left shunting of blood can occur during periods of apnea Shunting occurs through Foramen Panizzae

35 Shunting is controlled by systolic pressure differences Normal left sided pressure is higher than that of the right Apnea Right and left pressures equalize

36 Shunting Shunts can occur simultaneously in both directions Direction of the net shunt is determined by which circuit receives the majority of total cardiac output

37 Right to left shunting Diving Cooling Left to right shunting Basking Temporary L-R shunts occur during apnea Anticipatory L-R shunt prior to end of dive

38 Most commonly functions similar to four chambered heart Controlled shunting does occur

39 Control of shunting Regulation of peripheral resistance increased pulmonary resistance - right to left shunt increased systemic resistance - left to right shunt

40 Control of shunting Adjustments of cardiac excitation Ventilation - low velocity right to left depolarization Apnea - high velocity left to right depolarization

41 Matched ventilation and perfusion Right to left shunting during apnea allows ventilation and perfusion to remained matched, while maintaining systemic perfusion

42 Shunting does not save cardiac energy during apnea Right to left shunting during apnea does not allow for oxygen metering

43 Pulmonary bypass reduces plasma filtration into lungs Left to right shunting facilitates CO 2 elimination

44 Maintenance of core body temperature Right to left shunting facilitates warming Left to right shunting in conjunction with panting facilitates cooling

45 Arboreal Snakes must deal with the effects of gravity on their circulatory system

46 Arboreal snakes have the following adaptations Higher blood pressure Heart is located closer to the head Tightly adherent skin Good muscle tone The vascular lung is cranial to the heart and short in comparison with other snakes

47 Sea snakes live in an environment of near neutral buoyancy

48 Sea snakes have the following adaptations to their environment The heart is located near the mid-point of the body The vascular portion of the lung extends nearly the entire length of the body

49 Sea snakes lack the ability to compensate for gravitational effects on their circulatory system

50 Reptilian Kidney Unable to concentrate urine nephron lacks loop of Henle Glomerular filtration rate determined by the number of nephrons perfused

51 Veins arising in the caudal half of the body pass through the kidney prior to passing through the liver Blood passes over the renal tubules

52 Functions Water conservation Perfusion of the kidney

53 Thoughts on the renal portal system Therapeutic agents injected in the caudal half of the body may be cleared more rapidly Injections of potentially nephrotoxic agents made in the caudal portion of the body may increase the likelihood of nephrotoxicity

54 Blood in the renal portal system does not necessarily enter the kidney

55 Injection site does not appear to have clinically significant effect on pharmacokinetics

56 There does not appear to be elimination on first pass through the kidney

57 There does not appear to be accumulation of substances in the kidney

58

59 UV light is necessary for the synthesis of vitamin D Vitamin D is necessary for calcium absorbtion

60 Due to a lack of commercially formulated complete diets herpetoculturists must rely on UV lighting to meet the vitamin D requirements of captive reptiles

61 Light in the UVB spectrum is necessary for animals to produce Vitamin D Wavelength of approximately nm

62 The amount of UV produced by a fluorescent tube decreases over time Fluorescent tubes should be replaced every six months

63 Fluorescent tubes do not produce UVB along their entire length Only 50% of the tube produces UVB

64 The portion of the tube that produces UVB is in the center of the bulb There is no UVB production at the ends of the tube

65 UV light transmission Window glass blocks nearly all UVB Acrylic panels block nearly all UVB UV transmissible Plexiglas blocks nearly 40% of UVB A typical screen aquarium top blocks approximately 30% of UVB

66 Intensity of UV light is affected by distance Inverse Square Law

67 Typical fluorescent light tubes used to provide UV light to reptiles have an effective distance of 18 inches

68 UVB Irradiance Distance from Light Source Light Source 6 inches 12 inches 24 inches Reptile Daylight Sun Lamp (New) Sun Lamp (Used) Wonder Light (160) N/A Wonder Light (300) N/A Measurements in microwatts/cm 2

69 UVB Irradiance Distance from Light Source Light Source 6 inches 12 inches 24 inches Vitalight Black Light Cool White Experimental Lamp Reptisun Measurements in microwatts/cm 2