The ball python (Python regius) is a medium-sized snake of the family Boidae and is native to West Africa. Because of its gentle nature, moderate size, and variably attractive skin patterns, this snake is a popular species maintained in captivity. The respiratory system of snakes has been extensively reviewed.1 The trachea is long and narrow and composed of incomplete cartilaginous rings that are supported by a dorsal ligament. The trachea terminates into 2 short primary bronchi because ball pythons, like other boids, have both left and right lungs. Each bronchus continues a short distance as an intrapulmonary bronchus before terminating in the cranial portion of the lung. Each lung is composed of 3 areas: a highly vascular faveolar region in which gaseous exchange occurs; a short semisaccular (transitional) zone; and a larger saccular area, which is thin, semitransparent, and poorly vascularized.
As in other species of captive snakes, bacterial and fungal respiratory diseases are common in ball pythons and are often related to suboptimal temperature, humidity, or ventilation.2 In addition, paramyxovirus-associated respiratory tract disease in boids and tracheal chondromas in ball pythons have been reported.3 Given that specific treatment requires accurate diagnosis, the collection of exudates and tissue samples from the respiratory tract is important.4 Although various sampling techniques have been described, endoscopy provides the least invasive means of direct lung examination and biopsy and has been described for snakes and other reptiles.5–8 The long narrow trachea of snakes makes it difficult to impossible to use most rigid and flexible endoscopes to evaluate the distal portion of the trachea and lung via an endotracheal approach. Consequently, transcutaneous insertion of a rigid endoscope directly into the lung has been advocated.5,7 The purpose of the study reported here was to establish a safe and effective technique for transcutaneous endoscopic examination and biopsy of the lungs of snakes by use of a 2.7-mm rigid endoscope.
Materials and Methods
Animals—Seventeen recently imported adult ball pythons (15 females and 2 males) were obtained from a reptile wholesaler for use in the study. All procedures and methods were reviewed and accepted by the University of Georgia's Institutional Animal Care and Use Committee (IACUC No. A2006-10076-0). The pythons were maintained in conditions approved by the Association for Assessment and Accreditation of Laboratory Animal Care. Snakes were housed in groups of 3 or 4 in large plastic containers maintained in a room at an ambient temperature of 24°C (75°F) during the night and 27°C (81°F) during the day. Mercury halide incandescent lamps that were suspended above each enclosure provided a daytime basking area at 35°C (95°F). Pythons were exposed to a repeating cycle of 12 hours of light followed by 12 hours of darkness and a general humidity level of 50%. The snakes were physically examined on arrival and found to be clinically normal adults. The snakes were acclimatized to the research facilities for 7 days prior to the start of the study. They were not offered food during this acclimatization period, but water was available at all times. Following the surgical procedures, snakes were offered frozen-thawed rodents weekly.
On the day of surgery, the ball pythons were transferred to heated incubators at 29°C (85°F) for at least 1 hour prior to commencement of experimental procedures. The examination, anesthesia, and surgery areas were maintained at 24°C. Body weight and resting respiratory and heart rates were recorded for each snake. Each snake was identified by use of a unique number written with a permanent marker pen on the dorsal aspect of the cranium.
Anesthesia—Each python was premedicated with butorphanol tartratea (1 mg/kg [0.45 mg/lb]) administered via injection into the epaxial muscles 20 minutes prior to induction of anesthesia via intracardiac injection with propofolb (5 mg/kg [2.27 mg/lb]). Following intubation, anesthesia was maintained by use of 1% to 3% isoflurane in 100% oxygen (flow rate, 1 L/min) and adjusted to the individual's requirements. Throughout the anesthetic period, assisted ventilation was provided by use of a pressure-cycle ventilatorc; adjustments were made to maintain end-tidal CO2 readings > 10 mm Hg. Hypothermia was minimized by placing the snake on recirculating warm water blanketsd that were set to 40°C (105°F). Monitoring included assessments of tongue and tail withdrawal reflexes and ventral muscle tone, end-tidal capnography,e cardiac Doppler ultrasonography,f pulse oximetry,g and esophageal temperature measurement.h
Endoscopy—Each python was positioned in left lateral recumbency (with the dorsum facing the surgeon) on a horizontally level surgery table. The surgical entry site was identified at 90 ventral scales caudal to the head and 9 scales lateral on the right side. Following aseptic preparation, a vertical 8- to 10-mm incision was made through the interscalar skin. The subcutis was bluntly dissected until the underlying ribs and intercostal space were identified. Small straight mosquito hemostats were used to penetrate the intercostal muscles and separate the 2 adjacent ribs. The serosal surface of the right lung was identified as a thin semitransparent membrane containing a latticework of small blood vessels, which inflated in association with ventilation. The lung was penetrated by use of small hemostats to create a 3- to 4-mm pneumotomy and facilitate insertion of the 30° telescope (2.7 mm × 18 cm) that was housed within a 14.5-F operating sheath and connected to a xenon light source, endovideo camera, monitor, and digital recorder.i
Endoscopic examinations were performed by 2 experienced reptile endoscopists (SJS and SJHD). Each endoscopist scored the ease of entry into the lung (including skin incision, hemostat penetration, and entry of the endoscope) on a scale from 1 to 5 (1 = impossible [interval to insertion of endoscope, > 15 minutes]; 2 = difficult [interval to insertion of endoscope, 11 to 15 minutes]; 3 = satisfactory [interval to insertion of endoscope, 6 to 10 minutes]; 4 = good [interval to insertion of endoscope, 2 to 5 minutes]; and 5 = excellent [interval to insertion of endoscope, < 2 minutes]). Additionally, the endoscopist scored the ease of location and observation of various structures associated with the right side of the lower respiratory tract, including the distal portion of the trachea; primary bronchus; intrapulmonary bronchus; and regions of faveolar (cranial, vascular) lung, semisaccular (transitional zone) lung, and saccular (avascular air sac) lung on a scale of 1 to 5 (1 = impossible, 2 = difficult, 3 = satisfactory, 4 = good, and 5 = excellent).
Biopsy specimen collection—Once the evaluation was completed, 3 biopsies were performed endoscopically; samples were collected from the right faveolar region by use of 5-F biopsy forcepsi through the instrument channel of the endoscope sheath. Each biopsy specimen was gently transferred from the forceps to a biopsy cassette by use of a moistened cotton-tipped applicator; the cassette was then closed and placed in neutral-buffered 10% formalin. Hemorrhage from the biopsy sites was recorded on a scale of 1 to 3 (1 = no hemorrhage, 2 = minor hemorrhage, and 3 = major hemorrhage).
Completion of procedure—Only the skin was closed by use of a single 4-0 polydioxanonej horizontal mattress suture. Any complications associated with the anesthetic or surgical procedures were recorded. Eleven snakes were permitted to recover from anesthesia and were provided with postoperative analgesia (0.2 mg of meloxicamk/kg [0.09 mg/lb], IM). Six pythons were not permitted to recover but were euthanatized via IV injection of pentobarbital for immediate necropsy.
Repeat pulmonoscopy and biopsy specimen collection—The 11 remaining snakes were maintained for 12 months before undergoing repeat anesthesia and transcutaneous pulmonoscopy, as described. This second procedure was not scored, and the entry site was located at 95 ventral scales caudal to the head and 9 scales lateral on the right side to facilitate examination of the previous surgical approach. The right lung was evaluated for signs of disease or trauma that could be associated with the previous surgery. In particular, the surgical entry site into the lung and biopsy sites were evaluated.
Three endoscopic biopsy specimens were collected from the faveolar region of each snake (33 in total), but to avoid any physical damage to the harvested tissue, each biopsy was gently shaken from the forceps into a sterile red-top blood collection tube containing 1 mL of physiologic sterile saline (0.9% NaCl) solution. The sterile saline solution was then decanted and replaced with 1 of 3 fixatives; neutral-buffered 10% formalin solution, 2% glutaraldehyde, or Davidson's medium. Biopsy specimens were processed routinely for histologic evaluation.
Necropsy and histologic examination of tissue—Six pythons were euthanatized via IV administration of pentobarbital immediately following the original endoscopic procedure, and each snake underwent a full gross necropsy examination. The remaining 11 snakes were similarly euthanatized and examined 12 months later, immediately following the second endoscopy procedure. In all instances, the right lung was evaluated for any evidence of trauma or disease, and samples of lung (and any other abnormal tissues) were collected into neutralbuffered 10% formalin for routine histologic evaluation. Biopsy and necropsy tissues were processed routinely, embedded in paraffin, sectioned at approximately 5 μm, stained with H&E stain, and examined microscopically. Histologically, biopsy and necropsy tissues were subjectively compared to determine whether biopsy specimens collected during endoscopy were representative of tissue collected during necropsy. In addition, the diagnostic quality of each biopsy specimen was scored on a scale of 1 to 4 (1 = nondiagnostic, 2 = poor, 3 = good, and 4 = excellent); the criteria used included relative size of the biopsy sample in relation to the area biopsied, presence of crushing artifacts, quality of architectural detail preservation achieved via fixation, and tinctorial quality of the stained tissue.
Results
Among the 17 ball pythons, mean ± SD body weight and snout-to-vent length were 1,348 ± 327 g (2.972 ± 0.721 lb) and 109.9 ± 9.4 cm, respectively. All snakes appeared to be clinically normal adults and were in acceptable body condition. There were no significant changes in body weights during the course of the study. Premedication with butorphanol, induction of anesthesia with propofol, and maintenance of anesthesia with isoflurane in oxygen via intermittent pressure ventilation resulted in a surgical plane of anesthesia without complications in all snakes. Preand intraoperative variables were recorded (Table 1).
Pre-and perioperative findings in 17 ball pythons that underwent transcutaneous rigid pulmonoscopy of the right lung.
| Variable | Mean ± SD |
|---|---|
| Preoperative respiratory rate (breaths/min) | 8.3 ± 4.9 |
| Preoperative heart rate (beats/min) | 44 ±8 |
| Butorphanol premedication dose* (mg/kg) | 1.0 ±0.03 |
| Propofol dose† for induction of anesthesia (mg/kg) | 5.2 ±1.4 |
| Intraoperative ventilation rate‡ (breaths/min) | 6.4 ± 0.9 |
| Intraoperative maximum inspiratory pressure (mm Hg) | 4.0 ± 0.9 |
| Intraoperative end-tidal CO2 pressure (mm Hg) | 12.4 ± 1.7 |
| Intraoperative heart rate (beats/min) | 32 ±7 |
| Intraoperative esophageal temperature (°C[°F]) | 27.4 ± 0.8 (81.3 ± 1.4) |
Administered via injection into the epaxial muscles.
Administered via intracardiac injection.
Assisted ventilation was provided throughout the anesthetic period by use of a pressure-cycle ventilator.
To convert kilograms to pounds, multiply by 2.2.
Endoscopy score data were not normally distributed (Table 2). All mean endoscopy scores were > 4 (good), and the mean hemorrhage score was only 1.1 (Figure 1). In 16 of 17 snakes, the ease of entry score was considered satisfactory to excellent; however, in 1 snake, entry was considered difficult (score of 2) because of mild hemorrhage following hemostat penetration into the lung. Observation of the structures associated with the lower respiratory tract (accessed via the right lung), including the distal portion of the trachea; primary bronchus; intrapulmonary bronchus; cranial lung lobe; and faveolar, semisaccular, and saccular lung regions, was considered excellent (score of 5) in 16 of 17 pythons. In the snake with mild hemorrhage, observations of the trachea and primary bronchus were considered good (score of 4) and satisfactory (score of 3), respectively. However, endoscopic examination and biopsy procedures were still performed without complication in that snake.
Representative endoscopic views obtained from 17 ball pythons that were anesthetized and underwent transcutaneous rigid endoscopy of the right lung. A—Cranial view of the faveolar lung region. B—Close-up view to illustrate the primary (p), secondary (s), and tertiary (t) septae of the faveoli. C—View of the semisaccular (or transitional zone) region of the lung. D—Caudal view of the saccular lung region illustrating its thin nature and poor vascularity. E—View of the cranial aspect of the faveolar lung region illustrating the intrapulmonary bronchus (i), short primary bronchus (b), trachea (t), and anterior lung lobe (a). F—Close-up view illustrating the intrapulmonary bronchus (i), short primary bronchus (b), trachea (t), and anterior lung lobe (a). G—View into the anterior lung lobe (a) in which the primary bronchus (b) is also visible. H—View inside the distal portion of the trachea (t). Notice the incomplete cartilaginous rings and dorsal ligament (d). I—View of a biopsy procedure in the faveolar lung region involving use of 5-F biopsy forceps. J—View to illustrate the minimal bleeding that was typically observed immediately following a biopsy procedure. K—View of a typical healed biopsy site (b) after an interval of 1 year. Notice the healed defect within the faveolar tissue. L—View of an original pneumotomy entry site after an interval of 1 year. Notice the complete healing and minimal scarring (arrow) of the tissues.
Citation: Journal of the American Veterinary Medical Association 233, 3; 10.2460/javma.233.3.440
Representative endoscopic views obtained from 17 ball pythons that were anesthetized and underwent transcutaneous rigid endoscopy of the right lung. A—Cranial view of the faveolar lung region. B—Close-up view to illustrate the primary (p), secondary (s), and tertiary (t) septae of the faveoli. C—View of the semisaccular (or transitional zone) region of the lung. D—Caudal view of the saccular lung region illustrating its thin nature and poor vascularity. E—View of the cranial aspect of the faveolar lung region illustrating the intrapulmonary bronchus (i), short primary bronchus (b), trachea (t), and anterior lung lobe (a). F—Close-up view illustrating the intrapulmonary bronchus (i), short primary bronchus (b), trachea (t), and anterior lung lobe (a). G—View into the anterior lung lobe (a) in which the primary bronchus (b) is also visible. H—View inside the distal portion of the trachea (t). Notice the incomplete cartilaginous rings and dorsal ligament (d). I—View of a biopsy procedure in the faveolar lung region involving use of 5-F biopsy forceps. J—View to illustrate the minimal bleeding that was typically observed immediately following a biopsy procedure. K—View of a typical healed biopsy site (b) after an interval of 1 year. Notice the healed defect within the faveolar tissue. L—View of an original pneumotomy entry site after an interval of 1 year. Notice the complete healing and minimal scarring (arrow) of the tissues.
Citation: Journal of the American Veterinary Medical Association 233, 3; 10.2460/javma.233.3.440
Representative endoscopic views obtained from 17 ball pythons that were anesthetized and underwent transcutaneous rigid endoscopy of the right lung. A—Cranial view of the faveolar lung region. B—Close-up view to illustrate the primary (p), secondary (s), and tertiary (t) septae of the faveoli. C—View of the semisaccular (or transitional zone) region of the lung. D—Caudal view of the saccular lung region illustrating its thin nature and poor vascularity. E—View of the cranial aspect of the faveolar lung region illustrating the intrapulmonary bronchus (i), short primary bronchus (b), trachea (t), and anterior lung lobe (a). F—Close-up view illustrating the intrapulmonary bronchus (i), short primary bronchus (b), trachea (t), and anterior lung lobe (a). G—View into the anterior lung lobe (a) in which the primary bronchus (b) is also visible. H—View inside the distal portion of the trachea (t). Notice the incomplete cartilaginous rings and dorsal ligament (d). I—View of a biopsy procedure in the faveolar lung region involving use of 5-F biopsy forceps. J—View to illustrate the minimal bleeding that was typically observed immediately following a biopsy procedure. K—View of a typical healed biopsy site (b) after an interval of 1 year. Notice the healed defect within the faveolar tissue. L—View of an original pneumotomy entry site after an interval of 1 year. Notice the complete healing and minimal scarring (arrow) of the tissues.
Citation: Journal of the American Veterinary Medical Association 233, 3; 10.2460/javma.233.3.440
Assessments (mean ± SD scores) of ease of entry into the right lung, ease of observation of anatomic structures, and hemorrhage from biopsy sites in 17 ball pythons that were anesthetized and underwent transcutaneous rigid pulmonoscopy of the right lung.
| Variable | Score |
|---|---|
| Ease of initial entry* | 4.2 ± 1.0 |
| Ease of location and observation of various structures† | |
| Distal portion of the trachea | 4.9 ± 0.2 |
| Primary bronchus | 4.9 ± 0.5 |
| Intrapulmonary bronchus | 5.0 ± 0.0 |
| Faveolar lung region | 5.0 ± 0.0 |
| Semisaccular lung region | 5.0 ± 0.0 |
| Saccular lung region | 5.0 ± 0.0 |
| Postbiopsy hemorrhage‡ | 1.1 ±0.3 |
Ease of entry into the lung was assessed on a scale from 1 to 5 (1 = impossible [interval to insertion of endoscope, > 15 min]; 2 = difficult [interval to insertion of endoscope, 11 to 15 min]; 3 = satisfactory [interval to insertion of endoscope, 6 to 10 min]; 4 = good [interval to insertion of endoscope, 2 to 5 min]; and 5 = excellent [interval to insertion of endoscope, < 2 min]).
Ease of location and observation of various structures was assessed on a scale of 1 to 5 (1 = impossible, 2 = difficult, 3 = satisfactory, 4 = good, and 5 = excellent).
Hemorrhage from the biopsy sites was assessed on a scale of 1 to 3 (1 = no hemorrhage, 2 = minor hemorrhage, and 3 = major hemorrhage).
Among the 17 snakes, minor hemorrhage was rarely associated with entry into the lung but more commonly developed following lung biopsy. In the initial experiment, biopsy procedures were associated with minor and clinically unimportant bleeding in 15 of 17 snakes. In 2 snakes, intraoperative bleeding was considered severe in the endoscopic views, but in one of those snakes, no major hemorrhage was identified during necropsy performed immediately after completion of the experiment. The other affected python recovered completely and uneventfully, without any evidence of mucous membrane pallor associated with severe hemorrhage.
All 11 snakes that were allowed to recover from aesthesia did so uneventfully, without any evidence of morbidity and with no deaths associated with the procedure. Repeat pulmonoscopy 1 year later revealed healing of the previous biopsy sites, which appeared as small defects within the faveolar lung; typically, the original pneumotomy site was barely visible as a small scar.
Necropsy examinations did not reveal any notable damage to the skin, subcutis, and pulmonary or other visceral tissues. Diagnostic quality scores of the biopsy specimens obtained via pulmonoscopy were assessed; criteria for score allocation included the presence of crushing artifacts, preservation of architectural detail, and tinctorial quality of H&Estained tissues. Specimens collected from 17 snakes (3 specimens/snake; 51 biopsy specimens in total) during the initial endoscopic procedure were transferred to a biopsy cassette by use of a cotton-tipped applicator, and the cassette was placed in neutral-buffered 10% formalin; for these samples, mean ± SD quality score was 2.5 ± 0.8. Specimens were also collected from 11 of those snakes during a repeat procedure 1 year later (3 specimens/snake; 33 biopsy specimens in total). Samples were each shaken from forceps into saline solution and transferred to a biopsy cassette prior to placement in neutral-buffered 10% formalin, glutaraldehyde, or Davidson's medium; for these samples, mean ± SD quality score was 3.0 ± 0.0, 3.3 ± 0.5, and 2.0 ± 0.0, respectively.
Regardless of the fixative solution and method used for tissue handling, biopsy specimens were well-fixed and representative of the luminal half of the faveolar lung (Figure 2). Although most of the specimens were of adequate size, some were too small or were crushed during collection or transfer to the fixatives. In other specimens, the faveolar septae were clumped or collapsed; such artifact was detected most frequently in specimens that were transferred from forceps directly to fixative solution by use of cotton-tipped applicators. Architectural integrity and detail of the biopsy specimens were well preserved in all fixatives, but the tinctorial quality was best maintained in samples placed in the 2% glutaraldehyde solution; tinctorial quality was somewhat less well maintained in samples placed in neutralbuffered 10% formalin. Preservation of the tinctorial quality was inadequate in tissues fixed with Davidson's medium.
Photomicrographs of sections of biopsy specimens collected during endoscopy from the faveolar lung region of ball pythons. A—Representative lowmagnification image of a section of lung tissue that was gently shaken into physiologic saline (0.9% NaCl) solution before fixation in 2% glutaraldehyde. Notice that there are minimal crushing artifacts, and the preservation of architectural detail by fixation and tinctorial quality of this tissue are excellent. H&E stain; bar = 318 μm. B—Representative high-magnification image of a section of a lung tissue specimen that was gently shaken into saline solution before fixation in Davidson's medium. Preservation of architectural detail by fixation and tinctorial quality of this tissue are poor. H&E stain; bar = 35 μm. C—Representative high-magnification image of a section of a lung tissue specimen that was gently shaken into saline solution before fixation in neutral-buffered 10% formalin. Notice that there are minimal crushing artifacts, and the preservation of architectural detail by fixation and tinctorial quality of this tissue are excellent. H&E stain; bar = 35 μm. D— Representative high-magnification image of a section of a lung tissue specimen that was gently shaken into saline solution before fixation in 2% glutaraldehyde. Notice that there are minimal crushing artifacts, and the preservation of architectural detail from fixation and tinctorial quality of this tissue are excellent. H&E stain; bar = 35 μm.
Citation: Journal of the American Veterinary Medical Association 233, 3; 10.2460/javma.233.3.440
Photomicrographs of sections of biopsy specimens collected during endoscopy from the faveolar lung region of ball pythons. A—Representative lowmagnification image of a section of lung tissue that was gently shaken into physiologic saline (0.9% NaCl) solution before fixation in 2% glutaraldehyde. Notice that there are minimal crushing artifacts, and the preservation of architectural detail by fixation and tinctorial quality of this tissue are excellent. H&E stain; bar = 318 μm. B—Representative high-magnification image of a section of a lung tissue specimen that was gently shaken into saline solution before fixation in Davidson's medium. Preservation of architectural detail by fixation and tinctorial quality of this tissue are poor. H&E stain; bar = 35 μm. C—Representative high-magnification image of a section of a lung tissue specimen that was gently shaken into saline solution before fixation in neutral-buffered 10% formalin. Notice that there are minimal crushing artifacts, and the preservation of architectural detail by fixation and tinctorial quality of this tissue are excellent. H&E stain; bar = 35 μm. D— Representative high-magnification image of a section of a lung tissue specimen that was gently shaken into saline solution before fixation in 2% glutaraldehyde. Notice that there are minimal crushing artifacts, and the preservation of architectural detail from fixation and tinctorial quality of this tissue are excellent. H&E stain; bar = 35 μm.
Citation: Journal of the American Veterinary Medical Association 233, 3; 10.2460/javma.233.3.440
Photomicrographs of sections of biopsy specimens collected during endoscopy from the faveolar lung region of ball pythons. A—Representative lowmagnification image of a section of lung tissue that was gently shaken into physiologic saline (0.9% NaCl) solution before fixation in 2% glutaraldehyde. Notice that there are minimal crushing artifacts, and the preservation of architectural detail by fixation and tinctorial quality of this tissue are excellent. H&E stain; bar = 318 μm. B—Representative high-magnification image of a section of a lung tissue specimen that was gently shaken into saline solution before fixation in Davidson's medium. Preservation of architectural detail by fixation and tinctorial quality of this tissue are poor. H&E stain; bar = 35 μm. C—Representative high-magnification image of a section of a lung tissue specimen that was gently shaken into saline solution before fixation in neutral-buffered 10% formalin. Notice that there are minimal crushing artifacts, and the preservation of architectural detail by fixation and tinctorial quality of this tissue are excellent. H&E stain; bar = 35 μm. D— Representative high-magnification image of a section of a lung tissue specimen that was gently shaken into saline solution before fixation in 2% glutaraldehyde. Notice that there are minimal crushing artifacts, and the preservation of architectural detail from fixation and tinctorial quality of this tissue are excellent. H&E stain; bar = 35 μm.
Citation: Journal of the American Veterinary Medical Association 233, 3; 10.2460/javma.233.3.440
Discussion
The ball pythons in the present study were also used for various other projects including anatomic studies. In our study, the use of ball pythons for evaluation of the safety and effectiveness of rigid endoscopy to examine the lower respiratory tract of snakes was highly successful. The right lung was chosen for this procedure because the left lung is either absent or reduced in most snakes.1 However, in boids with disease that affects the left lung, a left (or bilateral) approach could be undertaken. The endoscope entry site into the right lung was specifically determined to coincide with the reduced vascularity of the semisaccular (transitional) portion of the lung. In addition to minimizing hemorrhage, entry at this level permitted an excellent view as far cranial as the distal portion of the trachea and as far caudal as the caudal extent of the saccular lung (air sac). In ball pythons, the entry site was located at 90 ventral scales caudal to the head and 9 scales lateral on the right side. This equates to 44% of the total snout-to-vent length. This landmark was determined by the anatomic evaluation and scale counts of several dissected specimens and published morphometric data.1 Jekl and Knotek7 suggest a similar entry point (35% to 45% of the total snout-to-vent length) for ball pythons, boa constrictors (Boa constrictors), and Burmese pythons (Python molurus bivittatus). Extensive morphometric data for many species of snakes has been summarized1 and can be used to accurately determine entry into the semisaccular lung. However, in the authors' experience, entry into the right lung of most snake species can be approximated by identifying the location of the heart and selecting a point halfway between the heart and the vent (ie, at approx 40% to 45% of the total snout-to-vent length).
Propofol and isoflurane provided effective and controllable anesthesia in the ball pythons of the present study. End-tidal CO2 values have been poorly investigated in reptiles. Observations in green iguanas have indicated that there may be poor correlation between end-tidal CO2 and arterial PCO2 values because of intracardiac or intrapulmonary shunting.9 However, clinical observations by the authors have suggested that maintaining the end-tidal CO2 value at > 10 mm Hg in snakes reduces the time to return to unassisted respiration following anesthesia. Insertion and movement of the endoscope within the right lungs of the study snakes did not appear to interfere with the maintenance of surgical anesthesia and did not alter the measured physiologic variables; however, the ability to accurately control and maintain respiration by use of the electrical ventilator was likely essential. A tight seal between the endoscope and the snake's skin, combined with closure of all the sheath ports, was important for preventing gas exchange across the surgical site. If a port were accidentally left open, the pressure cycle ventilator would not trigger and end-tidal CO2 values would decrease to zero.
The surgical approach used for endoscopic lung examination in snakes in the present study was more lateral and less extensive but otherwise similar to that described previously.7 In 16 of the 17 snakes, the ease of entry score was considered satisfactory to excellent; however, in 1 snake, entry was considered somewhat difficult because of mild hemorrhage following hemostat penetration into the lung. Endoscopic evaluation of the structures associated with the right lower respiratory tract was considered excellent in 16 of 17 pythons; in the snake with hemorrhage, observations of the trachea and primary bronchus were considered good and satisfactory, respectively, but this did not impede completion of the examination and biopsy procedures.
Minor hemorrhage was occasionally associated with entry into the lung but most commonly evident following lung biopsy. Biopsy procedures were associated with minor bleeding in 15 of the 17 snakes. In 2 snakes, intraoperative bleeding appeared severe endoscopically; in 1 snake, no major hemorrhage was detected at necropsy immediately after the endoscopic examination, and the other recovered without clinical signs of severe hemorrhage. Although pre-and postoperative Hct values were not determined, on the basis of the clinical and necropsy findings, we concluded that hemorrhage was minor and clinically unimportant but was magnified by the optics of the endoscope. All snakes permitted to recover from anesthesia after the initial evaluation did so uneventfully and without any evidence of morbidity and with no deaths during the following 12-month period.
Lung biopsy tissues are delicate. In the present study, lung tissue architecture was damaged during transfer of specimens by use of cotton-tipped applicators, resulting in poor to satisfactory diagnostic quality (mean quality score, 2.5). Diagnostic quality of tissues was improved by gently shaking specimens free from the forceps into sterile saline solution, before proceeding with fixation in neutral-buffered 10% formalin or glutaraldehyde (mean quality score, 3.0 and 3.3, respectively). Compared with those fixation techniques, use of Davidson's medium resulted in poorer staining (mean quality score, 2.0) and is therefore not recommended for processing of snake lung biopsy specimens.
Transcutaneous pulmonoscopy appears to be safe and effective for examination of the lower respiratory tract of snakes and is recommended when fine-diameter flexible or rigid endoscopes cannot reach the lungs via an endotracheal approach. Furthermore, biopsy procedures performed during lung endoscopy appear to be tolerated well and yield tissue samples of diagnostic quality.
Torbugesic (10 mg/mL), Fort Dodge Animal Health, Overland Park, Kan.
Propofol (10 mg/mL), Abbott Laboratories, North Chicago, Ill.
VT-5000, BAS Vetronics, Bioanalytical Systems Inc, West Lafayette, Ind.
Temperature therapy pad TP22G and temperature therapy pump TP500T, Gaymar, Orchard Park, NY.
ETCO2/SpO2 monitor, CO2 SMO, Novametrix Medical Systems, Wallingford, Conn.
Ultrasonic Doppler, Parks Electric Laboratory, Aloha, Ore.
V3301 Pulse Oximetry, SurgiVet, Waukesha, Wis.
Precision Thermometer, Tandy, Fort Worth, Tex.
64018BSA, 67065C, 201320-20, 69235106, 9291-B, 20094002U, and 67161 Z, Karl Storz Veterinary Endoscopy America Inc, Goleta, Calif.
PDS II, 2 metric, Ethicon, Somerville, NJ.
Metacam (5 mg/mL, injectable), Boehringer Ingelheim Vetmedica Inc, St Joseph, Mo.
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