Airway management under general anaesthesia in pigs using the LMA-ProSeal™: a pilot study

EVALUATION OF A LARYNGEAL MASK AIRWAY AS AN ALTERNATIVE TO OROTRACHEAL INTUBATION FOR MAINTAINING AIRWAY PATENCY DURING INHALANT ANESTHESIA UNDER SPONTANEOUS VENTILATION IN CAPYBARAS (HYDROCHOERUS HYDROCHAERIS)

Orotracheal intubation carries greater difficulty in rodents than in most domestic species. The human laryngeal mask airway (LMA) was compared with an endotracheal tube (ET_tube) for maintaining airway patency in anesthetized capybaras (Hydrochoerus hydrochaeris). Six capybaras (24-52 kg) were remotely darted with intramuscular ketamine, midazolam, and acepromazine on two occasions (≥7-day intervals). After isoflurane mask induction for random placement of an ET_tube or a LMA during each episode, anesthesia was maintained with isoflurane in oxygen under spontaneous ventilation for 90-120 min. Computed tomography of the pharynx and larynx was performed in two of six animals and three of six animals with the ET_tube and LMA, respectively. End-tidal isoflurane [median (range)] was not significantly different between ET_tube [0.6% (0.5-1.5%)] and LMA [0.6% (0.4-0.9%)]. Heart rate [67 ± 11 beats/min (ET_tube) and 67 ± 18 beats/min (LMA)], mean arterial pressure [74 ± 13 mm Hg (ET_tube) and 74 ± 14 mm Hg (LMA)], arterial CO2 tension [41 ± 2 mm Hg (ET_tube) and 43 ± 4 mm Hg (LMA)], and arterial O2 tension [360 ± 59 mm Hg (ET_tube) and 360 ± 63 mm Hg (LMA)] were not significantly different between treatment groups. Computed tomography showed gas in the esophagus with the LMA (three of three animals); the fit of the LMA to the larynx was adequate in two of three animals and fair in one of three animals. Recovery from anesthesia was uneventful. The LMA is a feasible alternative to the ET_tube for maintaining airway patency during inhalant anesthesia in spontaneously breathing capybaras. However, the LMA may be dislodged during movement of the animal.

Usage of Laryngeal Mask Airway Devices in Veterinary Medicine

Providing a secure airway management during general anesthesia could be problematic in some medical cases, especially when there is a risk of regurgitation and aspiration of the gastric content due to increased intragastric pressure. The current study aimed to test the applicability of two types of LMA in several animal species and to compare its effectiveness to the endotracheal intubation method in securing sealed airway respiration as an alternative to using endotracheal tubes. The study was conducted in dogs (n=33), cats (n=9), swine (n=9), rabbits (n=5), sheep (n=7) and roe deer (n=1). One or both types of laryngeal masks were used for each animal species: LMA Classic™-cLMA and LMA ProSeal™-PLMA. The assessment of each laryngeal mask was performed by determining the insertion technique, the possibilities of first-attempt insertion and malposition, the compliance with various animal species, ventilation time, cuff pressure, and sealing capacity. The highest LMA size compatility in dogs (23,87±14,30 kg) was size-3 in six and size-4 in forteen subjects; In swine (43,22±12,32 kg), size-4; In rabbits (3,84±0,36 kg) size-1; and in sheep (48,29±4,65 kg) size-3 and size-4. Ventilation time was highest in swine and roe deer (121,11±42,85 min and 300,00 min, respectively) and lowest in cat (28,33±16,96 min). First-attempt LMA insertion success was lowest in rabbits (60%), and highest in sheep and roe deer (100%). Malposition was with highest rate in rabbits (40%) and lowest in cat, sheep and roe deer (0%). Gastric reflux was most frequently observed in sheep (71,4%) and roe deer (100%). The usage of LMA in the veterinary anesthetic practice significantly improves airway management in animals during general anesthesia. The inflated LMA cuff does not prevent its disposition. Therefore, both the drain and respiratory tubes must be fixed. The usage of LMA in rabbits was associated with higher incidence of malposition and other complications. Our findings suggest that LMA designed for humans can be used for airway management in veterinary medicine.

Flexible fibreoptic intubation in swine - improvement for resident training and animal safety alike

Background

Efficient airway management to facilitate tracheal intubation encompasses essential skills in anaesthesiologic and intensive care. The application of flexible fibreoptic intubation in patients with difficult airways has been identified as the recommended method in various international guidelines. However, providing the opportunity to adequately train residents can be challenging. Using large animals for practice during ongoing studies could help to improve this situation, but there is no recent data on fibreoptic intubation in swine available.

Methods

Thirty male German landrace pigs were anesthetized, instrumented and randomized into two groups. The animals were either intubated conventionally using direct laryngoscopy or a single-use flexible video-endoscope. The intervention was carried out by providers with 3 months experience in conventional intubation of pigs and a brief introduction into endoscopy. Intubation attempts were supervised and aborted, when SpO2 dropped below 93%. After three failed attempts, an experienced supervisor intervened and performed the intubation. Intubation times and attempts were recorded and analysed.

Results

Flexible fibreoptic intubation showed a significantly higher success rate in first attempt endotracheal tube placement (75% vs. 47%) with less attempts overall (1.3 ± 0.6 vs. 2.1 ± 1.3, P = 0.043). Conventional intubation was faster (42 s ± 6 s vs. 67 s ± 10s, P < 0.001), but showed a higher complication rate and more desaturation episodes during the trial.

Conclusions

Flexible fibreoptic intubation in swine is feasible and appears to be a safer and more accessible method for inexperienced users to learn. This could not only improve resident training options in hospitals with animal research facilities but might also prevent airway complications and needless animal suffering.

A Novel and Simple Method for Tracheal Intubation in a Swine Model: Preparing for the Era of Xenotransplantation

OBJECTIVES

Organ transplant in humans is an established therapy for a variety of end-stage organ diseases. However, due to organ shortages and lack of donors, the need for xenotransplant has gradually increased. Xenotransplantation has great potential to solve many of the problems facing organ transplantation. Pigs are being developed as xenogeneic organ donors for use in humans. In this study, we propose a novel and simple method for tracheal intubation in a swine model using neuromuscular blocking agents and laryngeal mask airway.

MATERIALS AND METHODS

Eight Yorkshire pigs were used for the 2 separate experiments, which were conducted 1 week apart. In the first experiment, an anesthesiologist with no previous comparable experience performed endotracheal intubation of pigs. One week later, using the same pig, a second experiment was performed by an experienced anesthesiologist. Anesthesia was induced with intramuscular injection of a mixture of 1 mg/kg xylazine (Rompun, Bayer Korea Ltd., Seoul, Korea) and 7 mg/kg Zoletil (a mixture of tiletamine hydrochloride and zolazepam hydro-chloride, Virbac Laboratory, Carros, France). The laryngeal mask was then placed, and 0.15 mg/kg vecuronium bromide was injected intravenously. Tracheal intubation was attempted after mask removal. The duration and number of intubation attempts were recorded, and the degree of intubation difficulty was scored.

RESULTS

In all cases, the laryngeal mask was easily inserted, and endotracheal intubation was successfully completed. Oxygen saturation did not fall below 95%, and there were no hypoxemia episodes. Degree of intubation difficulty and duration were not significantly different between the 2 anesthesiologists.

CONCLUSIONS

Tracheal intubation in our swine model was successfully performed using neuromuscular blocking agents and laryngeal masks without resulting in hypoxemia, with even anesthesiologists who are unfamiliar with endotracheal intubation of pigs easily able to do so using our protocol. Therefore, our protocol will enable all investigators to perform successful tracheal intubation in swine models.

Anatomy and bronchoscopy of the porcine lung. A model for translational respiratory medicine

The porcine model has contributed significantly to biomedical research over many decades. The similar size and anatomy of pig and human organs make this model particularly beneficial for translational research in areas such as medical device development, therapeutics and xenotransplantation. In recent years, a major limitation with the porcine model was overcome with the successful generation of gene-targeted pigs and the publication of the pig genome. As a result, the role of this model is likely to become even more important. For the respiratory medicine field, the similarities between pig and human lungs give the porcine model particular potential for advancing translational medicine. An increasing number of lung conditions are being studied and modeled in the pig. Genetically modified porcine models of cystic fibrosis have been generated that, unlike mouse models, develop lung disease similar to human cystic fibrosis. However, the scientific literature relating specifically to porcine lung anatomy and airway histology is limited and is largely restricted to veterinary literature and textbooks. Furthermore, methods for in vivo lung procedures in the pig are rarely described. The aims of this review are to collate the disparate literature on porcine lung anatomy, histology, and microbiology; to provide a comparison with the human lung; and to describe appropriate bronchoscopy procedures for the pig lungs to aid clinical researchers working in the area of translational respiratory medicine using the porcine model.

Laryngeal pacing in minipigs: in vivo test of a new minimal invasive transcricoidal electrode insertion method for functional electrical stimulation of the PCA

Functional electrical stimulation (FES) of the posterior cricoarytenoid muscle (PCA) to restore respiratory function of the larynx may become an option for the treatment of bilateral recurrent laryngeal nerve paralysis (RLNP) in the near future. The feasibility of this has been shown in several animal trials and in a human pilot study. The common open surgical inferolateral approach for electrode insertion into the PCA for FES has a risk of damaging the recurrent laryngeal nerve (RLN) and may result in postoperative swelling and scaring of the larynx. Therefore, a minimal invasive electrode insertion technique is needed. A new miniaturized bipolar spiral tip electrode and a new electrical stimulatable insertion needle were tested in a short-term trial for an endoscopically guided and functionally controlled transcricoidal electrode insertion in eight Göttingen minipigs with bilateral normal RLN function. The feasibility of this technique was evaluated and the achieved positions of the electrodes in the PCA were analyzed using intraoperative stimulation threshold data and 3D-CT reconstructions. In seven cases it was possible to place two well-performing electrodes into the PCA. They were positioned one on either side. In one animal no functioning electrode position could be achieved because the PCA was missed. Thresholds of the electrode tips varied between 0.2 and 2.5 mA (mean 0.71 mA). In any case maximal glottal opening could be reached before adductors were co-activated. The majority of electrodes were placed into the central lower part of the PCA with no apparent correlation between threshold and electrode position. Surgical trauma might be further reduced by using endoscopy via a laryngeal mask avoiding the temporary tracheostomy used in this trial. If the implanted electrodes remain stable in long-term tests, we suggest that this method could soon be transferred into human application.

Laryngeal perforation during a standard intubation procedure in a pig

Pigs are frequently anaesthetized in animal research settings. Due to the unique laryngeal anatomy, endotracheal intubation is demanding in pigs. Several complications associated with endotracheal intubation have been reported in pigs, but laryngeal perforation following difficult intubation has not been documented so far. The present case report describes laryngeal perforation in a three-month-old pig following difficult intubation.

Ventral recumbency is crucial for fast and safe orotracheal intubation in laboratory swine

The aim of this study was to find the fastest, easiest and safest method of achieving orotracheal intubation for general anaesthesia in laboratory pigs. Twenty-one Yorkshire × Landrace crossbreed male castrated pigs (32.9 ± 4.8 kg) were investigated. Dorsal and ventral recumbency are the alternatives most frequently described for animal positioning during intubation procedures. Based on standardized induction of general anaesthesia using pentobarbital and remifentanil, the dorsoventral and ventrodorsal positions were compared with regard to the time needed, changes in oxygenation and circulatory response. Positioning was found to be crucial for fast orotracheal intubation. The time required for safe intubation is significantly shorter with the ventrodorsal position (17.3 s) in comparison with the dorsoventral position (58.4 s; P < 0.001). Hypoxia did not occur in either group. A significant drop in systolic blood pressure was observed in both groups. Diastolic and mean arterial pressures were not influenced by intubation. A significant increase in heart rate was observed in pigs intubated in ventral recumbency, but not after intubation in the dorsal position. Preoxygenation before intubation is vitally important for preventing hypoxia. With regard to clinical practice, the haemodynamic changes observed in this investigation do not appear to be relevant, as the mean arterial pressure was not altered and heart rates only increased moderately. It may be concluded that the ventrodorsal position can be recommended for orotracheal intubation in pigs as the first choice for providing a smooth and fast airway.

Feasibility of the laryngeal tube airway for artificial ventilation in pigs and comparison with the laryngeal mask airway

Airway management in anesthetized pigs is known to be technically demanding, and the 'gold standard' technique of endotracheal intubation is particularly difficult to master. The authors investigated the feasibility of the laryngeal tube as an alternative technique for airway management in German Landrace pigs (n = 5). They compared this method with the laryngeal mask, which is considered to be an effective yet relatively straightforward tool for porcine airway management. One after the other, investigators attempted to establish an airway in each anesthetized, artificially ventilated pig using each device. The laryngeal tube was too short to intubate the largest pig (weighing 45 kg), and it took investigators slightly longer to insert this device compared with the laryngeal mask. With the laryngeal mask, there were several incidents of gastric insufflation. Despite these complications, all investigators were able to establish a secure airway and maintain oxygenation with the laryngeal tube, and all subjectively rated both devices as easy to use.