Marine Turtle Trauma Response Procedures:   A Veterinary Guide

Mettee, Nancy (2014) WIDECAST Technical Report No. 16

Anesthetic Protocols

Anesthesia is defined as a general or local insensibility to pain; this loss of feeling permits performance of surgery and other painful procedures.  

Sea turtles do indeed feel pain which can manifest as withdrawal, biting, slapping, and evasion responses that can be very dangerous to both the patient and handlers attempting to restrain the animal. In addition, pain has many physiologic responses which can affect anesthesia, surgery, and healing (catecholamine release which can increase blood pressure, heart rate, and induce cardiac arrhythmias; increased cortisol which will increase blood glucose and can suppress the immune system, to name just a few). For these reasons, chemical restraint is preferred for any procedure that is likely to cause pain.

Reptiles are poikilothermic or “cold-blooded” which means their circulation will be extremely variable depending on the activity level prior to anesthesia, overall health status, and ambient temperature. Sea turtles additionally have physiologic dive responses (shunting of blood away from limbs and the ability to hold their breath for a significant amount of time) that will affect the uptake of anesthetics. For these reasons, whenever possible the intravenous route is preferred over SQ or IM and mask induction is not feasible. Thermal support during anesthesia and recovery will result in improved drug metabolism and provide more rapid recoveries (especially important in air conditioned environments). This may be accomplished with ambient light sources (hot lights), warm water bottles, or circulating water surgical tables. Caution should be exercised to avoid placing electrical heating elements beneath the patient as fluid leakage may cause an electrical short and subsequent burn. Electric blankets should never be used as they will overheat a reptile.

Sea turtles are pachyostotic and osteosclerotic meaning that their bone density increases with size and age. This will affect drug dosing as anesthetics typically do not distribute into bone. For this reason, smaller turtles will typically require higher end drug doses than larger turtles whose total body weight is greater affected by the presence of bone. 



Eye lubrication is standard when the palpebral response has been lost as the cornea may become dry.

INTUBATION

Intubation of sea turtles may be done after induction when there is sufficient loss of jaw tone. The largest tube that can safely be placed in the trachea should be used to reduce leakage as the cuff should NOT be inflated. (Sea turtles have complete tracheal rings and severe endothelial damage can occur is the tube fits too tightly in the windpipe.) The endotracheal tube need not be sterile, but simply cleaned and lubricated with K-Y jelly.

The tube can be introduced between the arytenoid cartilages located at the base of the tongue. The tip can be used to gently open the epiglottis. The trachea bifurcates at the base of the heart and splits into two primary bronchi that run the length of the lung. The split comes early so caution should be used when inserting the tube to make sure it does not go too far.

  sea turtle intubation

Waterproof tape should be used to secure the tube in place. A mouth gag should be left in place for the entire procedure to ensure the tube is not bitten by the patient.

 TapedGag1TapedGag

 

Example of a typical anesthetic protocol for sea turtles:

PREMEDS (may be given within one hour of induction)

Meloxicam 0.2 mg/kg SQ 

Buprenorphine 0.03 mg/kg IM

INDUCTION:


Propofol  3-5 mg/kg IV (given slowly)



OR

Ketamine 5 mg/kg IM/IV + Dexdomitor 50-100 mcg/kg IM/IV

OR

Telazol 10-15 mg/kg IM/IV (may result in very long recoveries)

MAINTENANCE:

Sevoflurane/Isoflurane @ variable percentage

 (Nitrous oxide may be added as a second gas)

Propofol CRI (titrate)

Sevoflurane has little to no patient benefit over isoflurane and cost remains high for this inhalant anesthetic. Sevoflurane is preferred when possilbe over isoflurane because incidental exposure of humans to sevoflurane carries a reduced risk over isoflurane. Isoflurane, however, still remains a good option for sea turtle anesthesia.



The drive for respiration is hypoxia and hypercapnea. As part of the dive response, sea turtles are extremely tolerant of both. Because of this, turtles will have no spontaneous respirations during anesthesia requiring intermittent positive pressure ventilation for maintenance of anesthesia. This may be done by a ventilator or manually. Breaths should be every 10 seconds with pressures not exceeding 20 mmHg. A sigh every 5 minutes is recommended (where the lungs are inflated and the pressure held for 5 seconds before release). Evaluation of the tidal volume can also be done by visualizing the patient’s body movement, but this will be challenging if the patient is in dorsal recumbency.



sea turtle anesthesia

Use palpebral response, cloacal tone, and tail avoidance to evaluate depth of anesthesia. Typically, it is appropriate to begin surgery when a tail pinch fails to elicit a response and the palpebral response has been lost.



Length of surgery will vary, but we usually begin to decrease the concentration of the sevoflurane gradually after we have reached the half way point. It is typical to have turtles breathing strictly oxygen during closure of the incision.



After the surgery is complete, the patient should be left on oxygen for 15-30 minutes during which IPPV is continued but the frequency of respirations may be decreased to one per minute. After this, the turtle should remain intubated on room air. An AMBU-bag may be used to continue IPPV, but the frequency may be further decreased to one breath every 5 minutes. Massage of the limbs to improve circulation and moving the turtle outdoors into the sun may also speed recovery, but it is vital that the turtle be supervised while still intubated.

Sea turtle “CPR” can be used to help flush residual anesthetic from deep in the lung fields.  See page 33 in Marine Turtle Trauma Response Procedures: A Field Guide for a description of the procedure. PDF 

MONITORING

The sea turtle heart has three muscular chambers: two atria and one ventricle. This configuration results in the mixing of oxygenated and non-oxygenated blood. Due to shunting and the overall capacity of sea turtle red blood cells for carrying oxygen, it does not have much impact clinically. It will affect EKG interpretation as a single peak pulse wave will be seen and not a typical PQRS display. Peripheral pulses are not palpable and cardiac auscultation is not possible due to the presence of the external shell.

Cardiac evaluation is possible with a Doppler flow meter, EKG or ultrasound.

A Doppler flow meter is used with the transducer placed over a major vessel.

doppler Carotid artery doppler

ventral cervical vessel doppler

EKG lead II placement will yield a pulse wave only, not a PQRS wave. Lead placement close to the body and with metal attachments to patient by skin staples or hypodermic needles can enhance the EKG trace in smaller patients.

EKG

Ultrasound can visualize movement of the heart, left and right aortic arches, and pulmonary arteries using the left and right cervicobrachial area as a window.  (need an image)

Reflexes

 anesthesiadepthSm



Recovery frequently involves several spurts of activity followed by rest. Do not extubate until at least three strong recovery spurts have been noted. If possible, delay extubation until the turtle is alert and having regular spontaneous respirations.

Following anesthesia, all patients are dry docked overnight, and not returned to the water until they demonstrate sufficient strength. A small bin or pen should be used to prevent the turtle from excessive activity while out of the water.





 

This chapter should be cited: Mettee, Nancy. 2014. Anesthetic Protocols. Marine Turtle Trauma Response Procedures:  A Veterinary Guide. WIDECAST Technical Report No. 16. Accessed online [date].

Updated 3/2014