Guidelines and criteria for the placement of laryngeal mask airways in dogs

Comparative study of ventilation techniques with supraglottic airway devices in cats: volume-controlled vs pressure-controlled techniques

OBJECTIVES

This study compared the effectiveness of a new supraglottic airway device (SGAD) in cats undergoing anaesthesia using two types of mechanical ventilation: volume-controlled ventilation (VCV) and pressure-controlled ventilation (PCV).

METHODS

A total of 13 healthy cats (five male, eight female; median age 2 years [range 1-3]) were randomly allocated to either VCV or PCV. Five tidal volumes (6, 8, 10, 12 and 14 ml/kg) and five peak inspiratory pressures (4, 5, 6, 7 and 8 cmH2O) were randomly applied with a minute ventilation of 100 ml/kg/min. Various parameters, such as blood pressure, gas leakage, end-tidal CO2 (ETCO2) and work of breathing (WOB), were measured while using VCV or PCV.

RESULTS

The occurrence of hypotension (mean arterial blood pressure <60 mmHg) was slightly less frequent with VCV (38 events, 65 ventilating sessions) than with PCV (40 events, 65 ventilating sessions), but this difference did not reach statistical significance (P = 0.429). The number of leakages did not differ between the VCV group (3 events, 65 ventilating sessions) and the PCV group (3 events, 65 ventilating sessions) (P = 1.000). Hypercapnia was identified when using VCV (10 events, 65 ventilating sessions) less frequently than when using PCV (17 events, 65 ventilating sessions), but this difference did not reach statistical significance (P = 0.194). The study found a significantly higher WOB in the PCV group compared with the VCV group (P <0.034).

CONCLUSIONS AND RELEVANCE

The present results suggested that both VCV and PCV can be used with an SGAD during anaesthesia, with VCV preferred for prolonged mechanical ventilation due to its lower workload. Adjusting tidal volume or inspiratory pressure corrects hypercapnia.

Use of Laryngeal Mask and Anesthetic Management in Hamadryas Baboons (Papio hamadryas) Undergoing Laparoscopic Salpingectomy-A Case Series

The study aims to describe the anesthetic and airway management of baboons (Papio hamadryas) undergoing laparoscopic salpingectomy with a laryngeal mask airway (LMA) device. Eleven baboons received tiletamine-zolazepam and medetomidine; anesthesia was induced with propofol. An LMA was positioned for oxygen and isoflurane administration in spontaneous respiration. Heart rate (HR), mean arterial pressure (MAP), respiratory rate (RR), end tidal carbon dioxide (EtCO₂), minute volume (MV), and peripheral hemoglobin oxygen saturation (SpO₂) were recorded before (PREPP) and immediately after abdomen insufflation (PP1), at 10 (PP2), 20 (PP3), and 30 (PP4) minutes during pneumoperitoneum, and after (POSTPP) pneumoperitoneum. The respiratory rate was significantly higher at all times compared to PREPP. The end tidal carbon dioxide concentration was significantly higher at PP2, PP3, PP4, and POSTPP, compared to the previous times. The higher values for RR and EtCO₂ were registered at PP4: 22.7 (95% CI 17.6-27.8) breaths/min and 57.9 (95% CI 51.9-63.8) mmHg, respectively. The minute volume was significantly higher at PP4 and POSTPP compared to the other times. The higher value for MV was registered at POSTPP (269.1 (95% CI 206.1-331.8) mL/kg/min). This protocol is suitable for baboons undergoing laparoscopic salpingectomy. The LMA was easy to insert and allowed for good ventilation, gas exchange, and delivery of the anesthetic in spontaneous breathing baboons.

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.

Comparison of plasma propofol concentration for apnea, response to mechanical ventilation, and airway device between endotracheal tube and supraglottic airway device in Beagles

The relationships between propofol plasma concentrations and the pharmacodynamic endpoints may differ according to a type of airway device. To clarify these relationships in different airway devices would be useful to avoid the complication such as apnea and intraoperative awareness. The aim of this study was to investigate the influence of difference of airway device on propofol requirement during maintenance of anesthesia in dogs. We compared the influence of airway devices on the plasma propofol concentrations for apnea, response to mechanical ventilation, and response to airway device between endotracheal tube (ETT) and supraglottic airway device (SGAD) in Beagles. The pharmacodynamic effects were repeatedly assessed at varying propofol concentrations. The plasma concentrations (mean ± SD) of propofol in the ETT and SGAD groups were 10.2 ± 1.8 and 10.9 ± 2.4 µg/ml for apnea (P=0.438), 7.9 ± 1.2 and 7.4 ± 1.5 µg/ml for response to mechanical ventilation (P=0.268), and 5.2 ± 0.7 and 5.4 ± 1.5 µg/ml for response to airway device (P=0.580), respectively. Required propofol concentration during maintenance of anesthesia may be similar between ETT and SGAD. Without moderate to strong stimuli such as airway device insertion or painful stimulation during surgery, the type of airway device may have little impact on required propofol concentration during maintenance of anesthesia in dogs.

The Association of Shelter Veterinarians' 2016 Veterinary Medical Care Guidelines for Spay-Neuter Programs

As community efforts to reduce the overpopulation and euthanasia of unwanted and unowned cats and dogs have increased, many veterinarians have increasingly focused their clinical efforts on the provision of spay-neuter services. Because of the wide range of geographic and demographic needs, a wide variety of spay-neuter programs have been developed to increase delivery of services to targeted populations of animals, including stationary and mobile clinics, MASH-style operations, shelter services, community cat programs, and services provided through private practitioners. In an effort to promote consistent, high-quality care across the broad range of these programs, the Association of Shelter Veterinarians convened a task force of veterinarians to develop veterinary medical care guidelines for spay-neuter programs. These guidelines consist of recommendations for general patient care and clinical procedures, preoperative care, anesthetic management, surgical procedures, postoperative care, and operations management. They were based on current principles of anesthesiology, critical care medicine, infection control, and surgical practice, as determined from published evidence and expert opinion. They represent acceptable practices that are attainable in spay-neuter programs regardless of location, facility, or type of program. The Association of Shelter Veterinarians envisions that these guidelines will be used by the profession to maintain consistent veterinary medical care in all settings where spay-neuter services are provided and to promote these services as a means of reducing sheltering and euthanasia of cats and dogs.

Removal of an Airway Foreign Body via Flexible Endoscopy Through a Laryngeal Mask Airway

A Silky terrier weighing 4.7 kg was presented with an airway foreign body after having aspirated a fragment of an orotracheal tube that was identified on radiological examination. Due to the small size of the patient, flexible endoscopy could not be performed through the lumen of a tracheal tube. Following IV induction of general anesthesia, the airway was instrumented with a laryngeal mask airway that was attached via a three-way connector to an anesthesia breathing circuit. A flexible endoscope was passed through the free port of the connector. That arrangement allowed for the passage of an endoscope through the lumen of the laryngeal mask airway and into the trachea without interrupting the continuous supply of O2 and sevoflurane.

Effect of inhaled carbon dioxide on laryngeal abduction

Hypercapnia produces a profound effect on respiratory drive and upper airway function to maintain airway patency. Previous work has evaluated the effects of hypercapnia on the sole arytenoid abductor, the posterior cricoarytenoid (PCA), using indirect measures of function, such as electromyography and direct nerve recording. Here we describe a novel method to evaluate PCA function in anesthetized animals and use this method to determine the effects of hypercapnia on PCA function. Eight dogs were anesthetized, and a laryngeal mask airway was used, in combination with high-speed videoendoscopy, to evaluate laryngeal function. A stepwise increase in inspired partial pressure of CO2 produced marked arytenoid abduction above 70-mmHg end-tidal CO2 (ETCO2) ( P < 0.001). Glottic length increased above 80-mmHg ETCO2 ( P < 0.02), and this lead to underrepresentation of changes in glottic area, if standard measures of glottic area (normalized glottic gap area) were used. Use of a known scale to determine absolute glottic area demonstrated no plateau with increasing ETCO2 up to 120 mmHg. Ventilatory parameters also continued to increase with no evidence of a maximal response. In a second anesthetic episode, repeated bursts of transient hypercapnia for 60 s with an ETCO2 of 90 mmHg produced a 43–55% increase in glottic area ( P < 0.001) at or shortly after the end of the hypercapnic burst. A laryngeal mask airway can be used in combination with videoendoscopy to precisely determine changes in laryngeal dimensions with high temporal resolution. Absolute glottic area more precisely represents PCA function than normalized glottic gap area at moderate levels of hypercapnia.

Influence of the collection and oxygenation method on quantitative bacterial composition in bronchoalveolar lavage fluid samples from healthy dogs

The purpose of the study was to evaluate the effects on quantitative and qualitative microbial content of endoscopic bronchoalveolar lavage fluid (BALF) in healthy dogs using a laryngeal mask airway (LMA). It was hypothesised that oropharyngeal protection might prevent contamination of BALF with oropharyngeal microflora. Ten healthy Beagle dogs were randomly assigned to two groups and underwent endoscopic BAL on two occasions, either via an open unprotected oropharynx with oxygen supply provided via a nasal catheter (NT) or through a sterile LMA. For the second sampling, groups were switched. BALF analysis included quantitative microbial culture, nucleated cell counts and cytology. The mean (+/-SD) number of colony forming units (CFU)/mL found in the BALF using the LMA was 25,610+/-22,943 in the right lung (RL) and 22,510+/-18,779 in the left (LL). With the NT technique, the figures were 21,068+/-19,375 for the RL and 16,060+/-15,523 for the LL, respectively. Nucleated cell counts/microL were 691.0+/-181.6 (RL) and 734.0+/-171.6 (LL) for LMA, and 772.0+/-251.0 (RL) and 748+/-163.2 (LL) for NT. No significant differences were detected either in the number of CFU/mL or in the diversity of bacterial species with the two methods. A significant increase in BALF bacterial counts (with reduced species diversity) was observed on the second compared to the first sampling regardless of the method used. Protection of the oral cavity and oropharynx using an LMA had no significant influence on BALF bacterial counts. The findings suggest that with careful endoscope insertion, the risk of contamination of BALF by resident and transient oropharyngeal microflora can be negligible.