Effects of suture tension during unilateral cricoarytenoid lateralization on canine laryngeal resistance in vitro

Objective— To evaluate the effect of abduction suture tension for unilateral arytenoid lateralization on laryngeal resistance. Study Design— Experimental study. Animals— Canine cadaver larynges (n=16). Methods— Laryngeal resistance was calculated in all specimens with the epiglottis in open and closed positions. Left cricoarytenoid lateralization was performed under low or high suture tension, and laryngeal resistance was re‐calculated. The effects of suture tension on laryngeal resistance were evaluated by repeated measures ANOVA. Results— Cricoarytenoid lateralization under low or high suture tension significantly reduced laryngeal resistance with the epiglottis in an open or closed position. There was no difference in laryngeal resistance with an open epiglottis between the low‐tension (1.00±0.0001 cm H₂O/L/s) and high‐tension (1.10±0.35 cm H₂O/L/s) groups (P=.33). The low‐tension group (22.80±14.20 cm H₂O/L/s) had significantly greater laryngeal resistance than the high‐tension group (8.45±4.00 cm H₂O/L/s) with a closed epiglottis (P=.016). There was no difference in laryngeal resistance with a closed epiglottis for the low‐tension group before (34.30±36.50 cm H₂O/L/s) and after (22.80±14.20 cm H₂O/L/s; P=.42) arytenoid lateralization. Conclusions— Cricoarytenoid lateralization under low suture tension significantly reduced laryngeal resistance with an open epiglottis, but resulted in a significantly greater resistance with a closed epiglottis than cricoarytenoid lateralization under high suture tension. Clinical Relevance— Clinically, use of a low‐tension suture for cricoarytenoid lateralization may provide an adequate decrease in open‐epiglottis laryngeal resistance to alleviate clinical signs, while maintaining enough closed‐epiglottis laryngeal resistance to reduce the risk of postoperative aspiration pneumonia.     

Effect of Prosthesis Number and Position on Rima Glottidis Area in Equine Laryngeal Specimens

Objective— To assess the effect of 1 or 2 laryngeal prosthetic sutures on rima glottidis areas in equine laryngeal specimens. Study Design— Experimental, randomized design. Animals— Cadaveric equine larynges (n=16). Methods— Larynges were collected from 10 horses; 2 sutures each were preplaced in the right and left sides of each larynx. A dorsal suture (DS) was placed through the caudal rim of the dorsal midline of the cricoid cartilage, under the cricopharyngeus muscle and through the proximal and rostral aspect of the muscular process. A lateral suture (LS) was placed 1.5 cm lateral to the DS and through the muscular process more distal and caudal to the 1st suture. Larynges were positioned in a customized stand and the rima glottidis photographed after each suture (LS or DS) or suture combination (CS) was tied in random sequence. An additional 6 larynxes were used to determine whether the tension applied to the sutures was repeatable. Sutures were preplaced in both the right and left side of each larynx as described above and each suture and CS was tied and released 3 times in each larynx. Photographs were taken of the rima glottidis after each suture or CS was tied generating 3 replicates for each suture configuration on each side of the 6 larynges. Results— Mean rima glottidis area was not different between DS and LS when tied alone (P=.85); however, mean area after CS (DS+LS) was greater than DS (P<.001) and LS (P<.001) alone. The coefficient of variation for the 6 suture patterns were low (1–7%) and the intraclass correlation coefficient estimates were very high (0.997–0.998) demonstrating excellent repeatability between replicates for each of the 3 suture configurations. Conclusion— Our results suggest that laryngoplasty using 2 prostheses; 1 placed dorsally in the cricoid and through the rostral and proximal muscular process and 1 placed 1.5 cm lateral to the 1st and more caudal and distal in the muscular process results in a greater cross sectional area of the rima glottidis than either suture used alone. Clinical Relevance— Seemingly prosthetic sutures contribute independently to each other in determining the contour of the rima glottidis. Use of 2 prosthetic sutures improves crosssectional area of the rima glottidis compared with each suture alone and may improve surgical outcome in laryngoplasty.     

Bronchopulmonary Disease in the Cat: Historical, Physical, Radiographic, Clinicopathologic, and Pulmonary Functional Evaluation of 24 Affected and 15 Healthy Cats

The results of clinical and pulmonary functional evaluation of 24 cats with bronchopulmonary disease and 15 healthy cats are presented. Affected cats had historical evidence of excessive reflexes (coughing, sneezing); physical evidence of airway secretions (crackles), obstruction (wheezing), and increased tracheal sensitivity; radiographic evidence of bronchial and interstitial lung disease; and cytological evidence of airway inflammation or mucous secretions. Bacterial isolates from healthy and affected cats were predominantly Gram-negative rods, indicating that bronchi of cats are not always sterile and that normal flora should be considered in interpreting cultures from cats with suspected bronchopulmonary disease. Cats were grouped according to relative disease severity based on scored historical, physical, and radiographic abnormalities. The mean (± standard deviation) baseline lung resistance measurement in healthy cats was 28.9 cm H₂O/L/s (±6.2 cm H₂O/L/s), whereas in mildly, moderately, and severely affected cats it was 38.3 cm H₂O/L/s (±21.5 cm H₂O/L/s), 44.8 cmH₂O/L/s (±7.7 cm H₂O/L/s), and 105.2 cm H₂O/L/s (±66.9 cm H₂O/L/s), respectively. In healthy cats, dynamic lung compliance was 19.8 (±7.4), whereas in mildly, moderately, and severely affected cats it was 14.7 mL/cm H₂O (±3.8 mL/cm H₂O), 17.7 mL/cm H₂O (±6.9 mL/cm H₂O), and 13.0 mL/cm H₂O (±7.9 mL/cm H₂O), respectively. Thus, airway obstruction was present in many of the affected cats. Based on acute response to the bron-chodilator, terbutaline, airway obstruction was partially reversible in many affected cats, although the degree of reversibility varied. Furthermore, based on bronchoprovocation testing, 6 (of 7) affected cats evaluated also had increased airway responsiveness to aerosolized methacholine.     

Effects of suture tension and surgical approach during unilateral arytenoid lateralization on the rima glottidis in the canine larynx

OBJECTIVES: To evaluate the effect of abduction suture tension and cricothyroid (CT) joint disarticulation on the area, height, and width of the rima glottidis (RG) during unilateral arytenoid lateralization. STUDY DESIGN: Experimental study. ANIMALS: Nine canine cadaver larynges. METHODS: Left arytenoid lateralization was performed with high or low abduction suture tension. RG area, height, and width were measured by computerized planimetric analysis with the epiglottis in an open and closed position. The experiment was performed with the CT joint intact and disarticulated. The effects of suture tension, CT disarticulation, and their interaction on RG area with the epiglottis closed or open were evaluated by repeated measures analysis of variance (ANOVA). RESULTS: RG area increased by 82% and 129% (P <.0001) with low and high suture tension, respectively. The aperture not covered by the epiglottis in a closed position was 467% larger with high suture tension than with low tension (P <.0001). CT disarticulation had no significant effect on RG geometry with either low or high suture tension (P =.4970). CONCLUSIONS: Low suture tension increased RG area when the epiglottis was in an open position without increasing RG aperture when the epiglottis was closed. Suture tension had a significant effect on RG opening when the epiglottis was closed. CT disarticulation did not modify the geometry of the RG. CLINICAL RELEVANCE: Use of a low-suture tension should be considered during arytenoid lateralization because it has the potential to reduce the risk of aspiration pneumonia.     

Arytenoid Lateralization for Treatment of Laryngeal Paralysis in 10 Cats

Objective— To describe the signalment, history, clinical signs, surgical technique, and outcome for cats with laryngeal paralysis that had arytenoid lateralization.
Study Design— Case series.
Animals— Cats with laryngeal paralysis (n=10).
Methods— Medical records (1996–2002) for cats with laryngeal paralysis that had arytenoid lateralization were reviewed for signalment, history, clinical signs, degree of paralysis, cause, concurrent medical conditions, surgical technique, and outcome. Follow-up information was obtained from owners or referring veterinarians.
Results— Of 10 cats, 9 had bilateral and 1 had unilateral laryngeal paralysis. Arytenoid lateralization were unilateral (n=7), bilateral (1), and staged bilateral procedures (2), 10 days and 3 years apart, respectively. Postoperatively, 1 cat had persistent inspiratory noise because of minimal enlargement of the rima glottidis and 2 cats required a temporary tracheostomy for management of laryngeal swelling. Three cats developed aspiration pneumonia and died 4, 7, and 150 days after surgery; all 3 had bilateral (simultaneous or staged) procedures. Of the 7 remaining cats, 4 were alive at follow-up and 3 had died of causes unrelated to arytenoid lateralization. The calculated mean survival time for all 10 cats was 406 days (median, 150 days; range, 4–1825 days).
Conclusions— Arytenoid lateralization was effective at enlarging the rima glottidis and reducing signs of airway obstruction in most cats.
Clinical Relevance— Unilateral arytenoid lateralization is a feasible option for the surgical management of cats with marked clinical signs; however, bilateral procedures should be avoided or at least performed with considerable caution because of the apparent risk for aspiration pneumonia.     

In vitro effect of ventriculocordectomy before laryngoplasty on abduction of the equine arytenoid cartilage

Objective: To determine whether ventriculocordectomy (VCE) performed before prosthetic laryngoplasty (PL) results in increased rima glottidis size compared with PL alone. Study Design: Experimental study. Animals: Equine cadaver larynges (n=13). Methods: Right arytenoid cartilages were maximally abducted using a standard PL technique. Standard PLs were then performed on the left side and the force required to maximally abduct the left arytenoid cartilage recorded (F_max). Photographs were taken of the rima glottidis at zero force and at five equal levels of force up to F_max. The force applied was released, left VCE performed, and photographs repeated. Arytenoid left:right angle quotients (LRQ) and glottic cross‐sectional area ratios (CSAR) were calculated at each force level in each condition (PL and VCE‐PL). Results: Mean LRQ and CSAR for both PL and VCE‐PL increased with increasing force, initially rapidly before plateauing at ～50% of F_max. LRQ and CSAR were significantly greater for VCE‐PL than for PL (P<.001). When VCE was performed before PL, 12% less force was required to achieve an LRQ of 0.8, and 45% less for a CSAR of 0.8. Conclusions: In vitro, VCE performed before PL enables the arytenoid cartilage to be abducted to a greater degree for a given PL suture force.     

Neuroanatomy of the equine dorsal cricoarytenoid muscle: surgical implications

Reason for performing study: Studies are required to define more accurately and completely the neuroanatomy of the equine dorsal cricoarytenoid muscle as a prerequisite for developing a neuroprosthesis for recurrent laryngeal neuropathy. Objective: To describe the anatomy, innervation, fibre types and function of the equine dorsal cricoarytenoid muscle. Methods: Thirty‐one larynges were collected at necropsy from horses with no history of upper airway disease and 25 subjected to gross dissection. Thereafter, the following preparations were made on a subset of larynges: histochemical staining (n = 5), Sihler's and acetylcholinesterase staining for motor endplates (n = 2). An additional 6 larynges were collected and used for a muscle stimulation study. Results: Two neuromuscular compartments (NMC), each innervated by a primary nerve branch of the recurrent laryngeal nerve, were identified in all larynges. Stimulation of the lateral NMC produced more lateral displacement of the arytenoid cartilage than the medial NMC (P<0.05). The medial NMC tended to rotate the arytenoid cartilage dorsally. Motor endplates were identified at the junction of the middle and caudal thirds of each NMC. If fibre type grouping was present it was always present in both NMCs. Conclusions: The equine dorsal cricoarytenoid muscle has 2 distinct muscle NMCs with discrete innervation and lines of action. The lateral NMC appears to have a larger role in increasing cross‐sectional area of the rima glottidis. Potential relevance: This information should assist in planning surgical reinnervation procedures and development of a neuroprosthesis for recurrent laryngeal neuropathy.     

An in vitro comparison of cordopexy, cordopexy and laryngoplasty, and laryngoplasty for treatment of equine laryngeal hemiplegia

OBJECTIVE: To examine the effect of cordopexy, laryngoplasty, and cordopexy combined with a modified laryngoplasty on airway mechanics. STUDY DESIGN: Experimental airway mechanics were determined by subjecting equine cadaveric larynges to airflows similar to inspiratory airflow of exercising horses. ANIMALS OR SAMPLE POPULATION: Twenty equine larynges. METHODS: Using cadaveric larynges, we developed and tested a new technique of arytenoid cartilage abduction. All larynges had the right arytenoid cartilage abducted to mimic the degree of arytenoid abduction that occurs at maximal exertion in live horses. Three surgical techniques were used to stabilize the left arytenoid cartilage of treated larynges; the left arytenoid cartilage was not stabilized in control larynges. Technique 1: Cordopexy--a suture was placed between the vocal ligament and the lamina of the thyroid cartilage. Technique 2: Standard laryngoplasty--a suture was placed between the muscular process of the arytenoid cartilage and the caudomedial aspect of the cricoid cartilage. Technique 3: Cordopexy plus modified laryngoplasty--the cordopexy suture was placed with a second suture between the horizontal ridge rostral to the muscular process of the left arytenoid cartilage and the lamina of the thyroid cartilage. Translaryngeal impedances (TI) were determined for each surgical technique by subjecting the larynges to increasing airflows and measuring the translaryngeal pressure differences. The arytenoid right to left angle quotient (RLQ) and the glottic cross-sectional area (CSA) were also measured. RESULTS: At maximal airflow, the adjusted means for the arytenoid RLQ and the TI for the cordopexy plus modified laryngoplasty (1.48 +/- 0.04, 0.69 +/- 0.05 cm H2O/L/s) and the standard laryngoplasty (1.39 +/- 0.04, 0.78 cm H2O/L/s) were different (P < .05) from values obtained after cordopexy alone (2.74 +/- 0.37, 1.76 +/- 0.48 cm H2O/L/s) or in control larynges (3.66 +/- 0.54, 4.16 +/- 0.96 cm H2O/L/s). Overall, a cordopexy plus modified laryngoplasty (9.69 cm2), a standard laryngoplasty (9.34 cm2), and a cordopexy alone (9 cm2) resulted in an increased glottic CSA greater than that for control larynges (6.94 cm2; P = .0001). CONCLUSIONS: Cordopexy alone did not improve airflow in a left laryngeal hemiplegic model. Cordopexy plus modified laryngoplasty was as efficacious as the standard laryngoplasty in alleviating the effects of left laryngeal hemiplegia on TI, glottic CSA, and arytenoid RLQ. CLINICAL RELEVANCE: Fixation of the vocal cord (cordopexy) in addition to a laryngoplasty procedure may prove useful in the surgical treatment of equine laryngeal hemiplegia.     

Video-Assisted Left Partial Arytenoidectomy by Diode Laser Photoablation for Treatment of Canine Laryngeal Paralysis

Objectives— To evaluate the clinical outcome of left partial arytenoidectomy by video-assisted laser diode photoablation as a surgical treatment for canine laryngeal paralysis (LP).
Study Design— Case series.
Animals— Dogs with bilateral LP (n=20).
Methods— After endoscopic diagnosis of bilateral LP, left partial arytenoidectomy was performed by photoablation of arytenoid cartilage tissue using a diode laser (600 μm diameter, 15 W power, 980 nm wave length) to increase the width of the rima glottidis. Outcome was evaluated endoscopically (1 and 6 months) and clinically (1, 6, and 12 months).
Results— No substantial complications occurred during photoablation or in the immediate postoperative period. Postoperative width of the rima glottidis ranged from 6 to 10 mm at its widest aspect. At 1 month, respiratory function after walking and short running appeared good. Clinical and endoscopic examination revealed good outcome at 1 and 6 months. At 6 months, there was no evidence of hypertrophic scar, hypertrophic granulation tissue, or stricture of the laryngeal glottis in any dog. Two dogs developed aspiration pneumonia after 12 months.
Conclusions— Partial arytenoidectomy using video-assisted diode laser photoablation appears to be an effective technique for treating LP.
Clinical Relevance— Partial arytenoidectomy by diode laser photoablation should be considered as an alternative technique for treatment of canine LP.     

Laryngeal function in normal dogs administered isoflurane following partial clearance of alfaxalone or propofol

ObjectiveTo assess laryngeal function in normal dogs administered isoflurane following partial clearance of alfaxalone or propofol.Study designRandomized experimental crossover study.AnimalsA group of 12 purpose-bred, male Beagle dogs.MethodsDogs were randomly assigned to one of two treatments: alfaxalone–isoflurane (ALF-ISO) or propofol–isoflurane (PRO-ISO) and anesthetized for three video laryngoscopy examinations. The alternate treatment occurred after ≥ 14 days interval. Examinations were performed after induction of anesthesia (LS-A), after 20 minutes of breathing isoflurane via a facemask (LS-B) and after a further 20 minutes of isoflurane (LS-C). Parameters of objective laryngeal function included inspiratory rima glottidis surface area (RGSA-I), expiratory rima glottidis surface area (RGSA-E) and % RGSA increase, calculated from three consecutive respiratory cycles in the final 15 seconds of each video laryngoscopy examination. The % RGSA increase was calculated using [(RGSA-I – RGSA-E)/RGSA-E] × 100. Subjective laryngeal function was evaluated independently by two experienced surgeons blinded to treatment.ResultsThe % RGSA increase within each treatment was greater for LS-B and LS-C than for LS-A (ALF-ISO: p = 0.03, PRO-ISO: p = < 0.001). There was no difference within each treatment from LS-B compared with LS-C. RGSA-I increased within each treatment from LS-A to both LS-B and LS-C (ALF-ISO: p = 0.002) and to LS-C (PRO-ISO: p = 0.006). Subjective laryngeal function scores improved from LS-A to LS-C.Conclusions and clinical relevanceLaryngeal function improved from postinduction examination following either 20 or 40 minutes of anesthesia with isoflurane via facemask. This study demonstrates that isoflurane may have a lesser effect on arytenoid abduction activity compared with more commonly used intravenous induction anesthetics (alfaxalone and propofol).     

Surgical management of laryngeal collapse associated with brachycephalic airway obstruction syndrome in dogs

Objective: To describe the use of cricoarytenoid lateralisation combined with thyroarytenoid caudo- lateralisation (arytenoid laryngoplasty) for the management of stage II and III laryngeal collapse in dogs. Methods: A retrospective study of a consecutive series of 12 dogs suffering from life-threatening stage II or III laryngeal collapse associated with brachycephalic airway obstruction syndrome. Results: Pre-operatively, either stage II collapse (2/12) or stage III collapse (10/12) was confirmed on visual examination. In all cases, a left-sided arytenoid laryngoplasty was performed. Two dogs were euthanased postoperatively as a result of persistent life-threatening respiratory compromise. The procedure resulted in subjective enlargement of the rima glottidis and an associated improvement in respiratory function in the remaining 10 dogs. Follow-up, long-term outcome (median, 3·5 years) in these dogs indicated that all owners considered that the surgery had resulted in marked improvements in their dog's respiratory function, tolerance to exercise, and quality of life. Clinical Significance: Combined cricoarytenoid and thyroarytenoid caudo-lateralisation may be a useful procedure for treatment of stage II and III laryngeal collapse in the dog.     

A Comparison of the Effects of Unilateral Thyroarytenoid Lateralization Versus Cricoarytenoid Laryngoplasty on the Area of the Rima Glottidis and Clinical Outcome in Dogs with Laryngeal Paralysis

OBJECTIVE: To compare the clinical effects of unilateral thyroarytenoid lateralization versus unilateral cricoarytenoid laryngoplasty for the treatment of canine laryngeal paralysis. Study Design-A prospective, clinical trial. ANIMALS: Twenty client-owned dogs admitted to Glasgow University Veterinary Hospital (GUVH) between 1997 and 1999 with a diagnosis of laryngeal paralysis. METHODS: A thorough evaluation of each dog was undertaken that included history, physical and neurologic examinations, complete blood count, serum biochemistry profile, serum thyroxine (T4) level, and thyroid-stimulating hormone (TSH) assay. The exercise tolerance of each dog was investigated by assessing respiratory rate and arterial blood gas analysis at rest and after 5 minutes of mild exercise. Animals were included in the study on the basis of a definitive diagnosis of laryngeal paralysis made by endoscopic observation of the larynx in the lightly anesthetized patient. The animals were randomly assigned to 1 of 2 treatment groups: unilateral thyroarytenoid lateralization or unilateral cricoarytenoid laryngoplasty, with all procedures being performed by the same surgeon. Video images of the rima glottidis were recorded pre- and postoperatively using video endoscopy. Video images were digitized and the area of the rima glottidis measured using image-analysis software. An increase in the area of the rima glottidis was expressed as a percentage of the preoperative area. All animals were reassessed 6 weeks' postoperatively, and exercise tolerance tests were repeated. RESULTS: The mean increase in the area of the rima glottidis postoperatively when compared with the preoperative area was 140% for those animals undergoing unilateral thyroarytenoid lateralization (range, 120%-158%) and 207% for those animals undergoing unilateral cricoarytenoid laryngoplasty (range, 183%-228%). This difference was statistically significant (P < .0001). At the 6-week postoperative examination, there was no significant difference in improvement between the 2 groups when compared on either a clinical basis or exercise tolerance tests. The mean surgical time in the 2 groups was 25 minutes for thyroarytenoid lateralization and 43 minutes for cricoarytenoid laryngoplasty. This was a statistically significant difference (P = .002). CONCLUSION: Although increase in area of the rima glottidis was significantly greater after unilateral cricoarytenoid laryngoplasty compared with unilateral thyroarytenoid lateralization, no difference in clinical outcome could be detected. However, the cricoarytenoid laryngoplasty procedure required significantly more surgical time. CLINICAL RELEVANCE: Both unilateral cricoarytenoid laryngoplasty and unilateral thyroarytenoid lateralization are successful methods for the treatment of laryngeal paralysis; however, thyroarytenoid lateralization requires less surgical time to perform.     

Aspects of in vivo endotracheal tube intracuff pressure in cats

Objectives

To determine the endotracheal tube cuff pressure produced with two inflation techniques, in two brands of endotracheal tube in cats. To determine the inspiratory pressure which produces an audible leak when the intracuff pressure is 30 cmH₂O.

Effects of 12 and 17 cmH2O positive end-expiratory pressure applied after alveolar recruitment maneuver on pulmonary gas exchange and compliance in isoflurane-anesthetized horses

Objective

To compare static compliance (C_st) and alveolar–arterial oxygen tension difference [P(a–a)O₂] between positive end-expiratory pressures (PEEP) of 7, 12 and 17 cmH₂O applied after an alveolar recruitment maneuver (RM) in isoflurane-anesthetized horses.

Laryngeal paralysis in dogs: An evaluation of the bilateral arytenoid lateralisation procedure

Within the past decade, the number of reported cases of laryngeal paralysis in dogs has increased markedly. The disease is characterised by laryngeal obstruction caused by the inadequate abduction and instability of the arytenoid cartilages, aryepiglottic folds and vocal cords. Therefore, surgery performed to alleviate the clinical signs should ideally aim to reduce the airway obstruction and to prevent dynamic collapse. This paper presents the effectiveness of bilateral arytenoid lateralisation in 19 dogs with bilateral laryngeal paralysis. The procedure was effective in alleviating the clinical signs of laryngeal obstruction in all 19 dogs, with most surviving for several years. Postoperative laryngoscopic observations showed that the arytenoid cartilages were held in a satisfactory abducted position. A comparison of PaO₂ values before and after surgery demonstrated a significant (P 0·001) fall in the PaO₂ measurement between the pre- and postoperative blood samples. Postoperative complications included suture prosthesis failure in two dogs and a single non-fatal incident of aspiration pneumonia in two dogs.     

A novel flow partition device for spirometry during large animal anaesthesia

ObjectiveWe describe and test a novel device for large animal anaesthesia monitoring that uses standard human medicine spirometry sensors.Study designIn-vitro study.MethodsThe device consists of two adapters that enable the flow to be split evenly into four tubes in parallel, each tube containing a D-lite sensor. The performance of this flow partitioning device (FPD) over a range of flows from 100 to 700 L minute^?1 was determined and the pressure versus flow relation, resistance and dead space was compared with a Horse-lite (Moens 2010).ResultsEquipped with four D-lite sensors, and a flow of 700 L minute^?1 the pressure drop of the FPD was 13.5 cmH₂O, resistance 1.17 cmH₂O second L^?1 and volume (potential dead space) 182 mL, compared to 2.8 cmH₂O, 0.24 cmH₂O second L^?1 and 54 mL respectively for the Horse-lite. The predicted value of the flow partition of ¼ could be confirmed. Limits of agreement were found to be 4.2% in inspiratory direction and 7.1% in expiratory direction.Conclusions and clinical relevanceThe FPD is an affordable device that extends the specification of any commercially available human spirometry sensors to large animal applications. However, an increase in total resistance and dead space has to be taken into account. Therefore, the new device could be useful during equine anaesthesia.     

Correlation between jugular and central venous pressures in laterally recumbent horses

Objective To compare and correlate right atrial pressure, which represents central venous pressure (CVP) to jugular vein pressure (JVP) in laterally recumbent horses under anesthesia. Study design Retrospective clinical trial. Animals Seven adult healthy horses (411 ± 8.7 kg). Methods Horses were sedated with IV xylazine and anesthesia was obtained with IV ketamine and diazepam. Anesthesia was maintained with sevoflurane in oxygen. All horses were positioned in left lateral recumbency. An 8F catheter introducer was inserted into the right jugular vein to measure JVP. An 8F catheter introducer was inserted into the left jugular vein to be used as the port for a 7F 110 cm catheter that reached the right atrium to measure CVP. Both, CVP and JVP were measured simultaneously with a water calibrated aneroid manometer using the sternum as the 0 cmH₂O reference point. Measurements were compared using Spearman correlation and the Bland‐Altman plot. Results Twenty paired samples were obtained over a period of 2 hours. The CVP ranged from 7 to 31 cmH₂O, while the JVP ranged from 5 to 30 cmH₂O. The Spearman correlation coefficient indicated that CVP and JVP had a strong correlation with r = 0.88. The Bland‐Altman plot showed a bias of 0.7 cmH₂O. Conclusion and clinical relevance Jugular vein pressure showed a strong correlation with CVP in healthy, euvolemic, laterally recumbent anesthetized adult horses. Thus, JVP cannot replace CVP but it may be used clinically to monitor CVP in laterally recumbent horses.     

Repeatability, reproducibility, and effect of head position on central venous pressure measurement in standing adult horses

Background: Central venous pressure (CVP) is a used as an estimation of intravascular volume status in various species. Techniques for measuring CVP in horses have been described, but the repeatability of these readings at a single time point or over time has not been established. Hypothesis: That CVP measurements in healthy adult horses would be repeatable at each time point, that these readings would be reproducible over time, and that alteration in head position relative to the heart would alter CVP. Animals: Ten healthy adult research horses. Methods: In an experimental study, horses were instrumented with a central venous catheter. Readings were taken in triplicate q6h for 2 days by water manometry, and twice daily with the head in neutral, elevated, and lowered positions by electronic manometry. Results: Variation in the “neutral” measurements obtained at each time point was <0.1 ± 1.0 cmH₂O (P= .718). There was a significant decrease in CVP over time (P= .015), which was eliminated when results were controlled for acute decrease in body weight of ?1.35% (presumed hypohydration because of lack of acclimatization and decreased water intake). Head height had a significant and directional effect on CVP in that the elevated head position decreased CVP ?2.0 ± 6.5 cmH₂O (P < .001) while the lowered head position increased CVP by 3.7 ± 5.5 cmH₂O (P < .001). Conclusions and Clinical Importance: CVP values obtained by water manometry were repeatable in adult horses, but were reproducible only when controlled for changes in hydration. Care should be taken to maintain consistency in head position to prevent erroneous readings.     

Comparison of the effects of alfaxalone and propofol with acepromazine,butorphanol and/or doxapram on laryngeal motion and quality of examination in dogs

Objective

To compare the effects of alfaxalone and propofol, with and without acepromazine and butorphanol followed by doxapram, on laryngeal motion and quality of laryngeal examination in dogs.

Intermittent positive pressure ventilation with constant positive end-expiratory pressure and alveolar recruitment manoeuvre during inhalation anaesthesia in horses undergoing surgery for colic, and its influence on the early recovery period

Objective To compare, ventilation using intermittent positive pressure ventilation (IPPV) with constant positive end‐expiratory pressure (PEEP) and alveolar recruitment manoeuvres (RM) to classical IPPV without PEEP on gas exchange during anaesthesia and early recovery. Study design Prospective randomized study. Animals Twenty‐four warm‐blood horses, weight mean 548 ± SD 49 kg undergoing surgery for colic. Methods Premedication, induction and maintenance (isoflurane in oxygen) were identical in all horses. Group C (n = 12) was ventilated using conventional IPPV, inspiratory pressure (PIP) 35–45 cmH₂O; group RM (n = 12) using similar IPPV with constant PEEP (10 cmH₂O) and intermittent RMs (three consecutive breaths PIP 60, 80 then 60 cmH₂O, held for 10–12 seconds). RMs were applied as required to maintain arterial oxygen tension (PaO₂) at >400 mmHg (53.3 kPa). Physiological parameters were recorded intraoperatively. Arterial blood gases were measured intra‐ and postoperatively. Recovery times and quality of recovery were measured or scored. Results Statistically significant findings were that horses in group RM had an overall higher PaO₂ (432 ± 101 mmHg) than those in group C (187 ± 112 mmHg) at all time points including during the early recovery period. Recovery time to standing position was significantly shorter in group RM (49.6 ± 20.7 minutes) than group C (70.7 ± 24.9). Other measured parameters did not differ significantly. The median (range) of number of RMs required to maintain PaO₂ above 400 mmHg per anaesthetic was 3 (1–8). Conclusion Ventilation using IPPV with constant PEEP and RM improved arterial oxygenation lasting into the early recovery period in conjunction with faster recovery of similar quality. However this ventilation mode was not able to open up the lung completely and to keep it open without repeated recruitment. Clinical relevance This mode of ventilation may provide a clinically practicable method of improving oxygenation in anaesthetized horses.