Evaluation of the Effect of the Inspired Oxygen Fraction on Blood Oxygenation during Inhalant Anaesthesia in Horses: A Systematic Review with Meta-Analysis.

In anaesthetized horses, pronounced ventilation/perfusion mismatching often occurs. Several authors have investigated the effect of lower inspired oxygen fractions (FiO2) to reduce formation of absorption atelectasis. This systematic review compared the effects of low (<0.6) and high (>0.8) FiO2 on the arterial oxygen tension (PaO2), the alveolar-to-arterial oxygen tension difference (P(A-a)O2), and the PaO2/FiO2 ratio in horses during inhalation anaesthesia. Using the Systematic Review Protocol for Animal Intervention Studies, four experimental and one clinical investigations were deemed suitable for inclusion. A meta-analysis was performed on the four experimental studies. The PaO2 was significantly lower (p = 0.0007, mean difference -23.54 kPa, 95% CI -37.18, -9.90) with a lower FiO2. However, the P(A-a)O2 was also significantly lower (p < 0.00001, mean difference -20.80 kPa, 95% CI -26.28, -15.32) when using a low FiO2. For the PaO2/FiO2 ratio, only one study fitted the inclusion criteria, so no meta-analysis was performed. It is concluded that, while only a limited number of studies are available, the use of a higher FiO2 in horses during inhalation anaesthesia will result in higher levels of PaO2, but also a larger P(A-a)O2 difference. Further studies are needed to increase the level of evidence on this subject.

Monitoring changes in distribution of pulmonary ventilation by functional electrical impedance tomography in anaesthetized ponies.

OBJECTIVE: To assess changes in the distribution in pulmonary ventilation in anaesthetized ponies using electrical impedance tomography (EIT). STUDY DESIGN: Prospective experimental study. ANIMALS: A group of eight adult pony geldings. METHODS: General anaesthesia was induced and maintained using isoflurane in oxygen with volume-controlled ventilation [tidal volume (VT) (10 mL kg-1), respiratory rate (8-12 breaths minute-1)] to maintain end-tidal carbon dioxide between 35 and 40 mmHg (4.66-5.32 kPa). Regional distribution of ventilation was assessed with EIT (plane of fifth to sixth intercostal space) at 30, 60 and 90 minutes after intubation. The resulting functional images were divided into four regions of interest (ROI, A-D) to determine: 1) the ratio of VT distribution between dependent to nondependent lung (D/ND) and 2) changes in distribution within the lungs in the latero-lateral direction. The centre of ventilation (COV) was calculated. The dimension of the chest in the latero-lateral (W) and dorso-ventral (H) direction was measured at the height of the withers and the W/H ratio was calculated. The influence of time on the D/ND ratio, COV and ROI A-D were analysed with anova followed by post hoc Bonferroni tests. Pearson correlation coefficient and the coefficient of determination (r2) were calculated to evaluate the relationship between the W/H ratio and D/ND ratio, and COV. Statistical significance was set at p < 0.05. RESULTS: The median D/ND ratio (T30-T90) was 0.67 (0.40-1.01) and for COV 31.15% (11.20-45.20), confirming the expected uneven distribution of ventilation. The D/ND ratio had a moderate negative correlation with the W/H ratio (r = -0.68, r2 = 0.46, p < 0.001), while the COV did not correlate with the W/H ratio (r = -0.04). CONCLUSIONS AND CLINICAL RELEVANCE: Uneven ventilation in mechanically ventilated right laterally recumbent anaesthetized ponies occurs within 30 minutes and changed little over the following 60 minutes.

Edible insects - defining knowledge gaps in biological and ethical considerations of entomophagy.

While seeking novel food sources to feed the increasing population of the globe, several alternatives have been discussed, including algae, fungi or in vitro meat. The increasingly propagated usage of farmed insects for human nutrition raises issues regarding food safety, consumer information and animal protection. In line with law, insects like any other animals must not be reared or manipulated in a way that inflicts unnecessary pain, distress or harm on them. Currently, there is a great need for research in the area of insect welfare, especially regarding species-specific needs, health, farming systems and humane methods of killing. Recent results from neurophysiological, neuroanatomical and behavioral sciences prompt caution when denying consciousness and therefore the likelihood of presence of pain and suffering or something closely related to it to insects. From an animal protection point of view, these issues should be satisfyingly solved before propagating and establishing intensive husbandry systems for insects as a new type of mini-livestock factory farming.

Impact of four different recumbencies on the distribution of ventilation in conscious or anaesthetized spontaneously breathing beagle dogs: An electrical impedance tomography study.

The aim was to examine the effects of recumbency and anaesthesia on distribution of ventilation in beagle dogs using Electrical Impedance Tomography (EIT). Nine healthy beagle dogs, aging 3.7±1.7 (mean±SD) years and weighing 16.3±1.6 kg, received a series of treatments in a fixed order on a single occasion. Conscious dogs were positioned in right lateral recumbency (RLR) and equipped with 32 EIT electrodes around the thorax. Following five minutes of equilibration, two minutes of EIT recordings were made in each recumbency in the following order: RLR, dorsal (DR), left (LLR) and sternal (SR). The dogs were then positioned in RLR, premedicated (medetomidine 0.01, midazolam 0.1, butorphanol 0.1 mg kg-1 iv) and pre-oxygenated. Fifteen minutes later anaesthesia was induced with 1 mg kg-1 propofol iv and maintained with propofol infusion (0.1-0.2 mg kg-1 minute-1 iv). After induction, the animals were intubated and allowed to breathe spontaneously (FIO2 = 1). Recordings of EIT were performed again in four recumbencies similarly to conscious state. Centre of ventilation (COV) and global inhomogeneity (GI) index were calculated from the functional EIT images. Repeated-measures ANOVA and Bonferroni tests were used for statistical analysis (p < 0.05). None of the variables changed in the conscious state. During anaesthesia left-to-right COV increased from 46.8±2.8% in DR to 49.8±2.9% in SR indicating a right shift, and ventral-to-dorsal COV increased from 49.8±1.7% in DR to 51.8±1.1% in LLR indicating a dorsal shift in distribution of ventilation. Recumbency affected distribution of ventilation in anaesthetized but not in conscious dogs. This can be related to loss of respiratory muscle tone (e.g. diaphragm) and changes in thoracic shape. Changing position of thoraco-abdominal organs under the EIT belt should be considered as alternative explanation of these findings.

Assessment of distribution of ventilation and regional lung compliance by electrical impedance tomography in anaesthetized horses undergoing alveolar recruitment manoeuvres.

OBJECTIVE: To examine changes in the distribution of ventilation and regional lung compliances in anaesthetized horses during the alveolar recruitment manoeuvre (ARM). STUDY DESIGN: Experimental study in which a series of treatments were administered in a fixed order on one occasion. ANIMALS: Five adult Warmblood horses. METHODS: Animals were anaesthetized (xylazine, midazolam-ketamine, isoflurane), placed in dorsal recumbency and ventilated with 100% oxygen using peak inspiratory pressure (PIP) and positive end-expiratory pressure (PEEP) of 20 cmH2O and 0 cmH2O, respectively. Thoracic electrical impedance tomography (EIT), spirometry and routine anaesthesia monitoring were performed. At 90 minutes after induction of anaesthesia, PIP and PEEP were increased in steps of 5 cmH2O to 50 cmH2O and 30 cmH2O, respectively, and then decreased to baseline values. Each step lasted 10 minutes. Data were recorded and functional EIT images were created using three breaths at the end of each step. Arterial blood samples were analysed. Values for left-to-right and sternal-to-dorsal centre of ventilation (COV), lung compliances and Bohr dead space were calculated. RESULTS: Distribution of ventilation drifted leftward and dorsally during recruitment. Mean±standard deviation (SD) values at baseline and highest airway pressures, respectively, were 49.9±0.7% and 48.0±0.6% for left-to-right COV (p=0.009), and 46.3±2.0% and 54.6±2.0% for sternal-to-dorsal COV (p=0.0001). Compliance of dependent lung regions and PaO2 increased, whereas compliance of non-dependent lung regions decreased during ARM and then returned to baseline (p<0.001). Bohr dead space decreased after ARM (p=0.007). Interestingly, PaO2 correlated to the compliance of the dependent lung (r2=0.71, p<0.001). CONCLUSIONS AND CLINICAL RELEVANCE: The proportion of tidal volume distributed to dependent and left lung regions increased during ARM, presumably as a result of opening atelectasis. Monitoring compliance of the dependent lung with EIT may substitute PaO2 measurements during ARM to identify an optimal PEEP.

Vertebral Subluxation Repair in a Pet Goat.

OBJECTIVES: To describe the perioperative management, including surgery, anesthesia, metabolic derangements, and physiotherapy, in a goat referred for paraparesis secondary to a road traffic accident. STUDY DESIGN: Case report. ANIMALS: 2-year-old mixed breed dwarf 44 kg female pet goat. METHODS: Clinical examination showed symptoms of early compensatory stages of shock, paraparesis with hyperextension of the thoracic limbs, pain on palpation of the thoracolumbar spine, increased patellar reflexes of both pelvic limbs without superficial sensitivity, but preserved deep pain sensation. These signs suggested a spinal cord injury with upper motor neuron syndrome and an anatomic localization between the third thoracic and third lumbar vertebrae. Radiographic examination revealed a thoracolumbar vertebral subluxation. Vertebral stabilization was achieved with the application of pins in the vertebral bodies stabilized by an interconnecting bridge of polymethylmethacrylate, a technique commonly adopted in companion animals. RESULTS: Surgery and recovery from anesthesia were uneventful, but 3 days later ruminal atony and subsequent bloating occurred. This was associated with metabolic derangements (metabolic alkalosis), decreased mentation, and marked tachypnea that responded to medical treatment. From day 3 post-surgery, the goat underwent physiotherapy with manual and active exercises during the rehabilitation period of 21 days duration. CONCLUSION: The injury in this goat was successfully managed using vertebral stabilization similar to that used in dogs and cats. Extensive postoperative physiotherapeutic support contributed to the complete recovery of the animal.

Modern Spirometry Supports Anesthetic Management in Small Animal Clinical Practice: A Case Series.

Modern spirometry, like no other monitoring technique, allows insight into breath-to-breath respiratory mechanics. Spirometers continuously measure volume, airway pressure, and flow while calculating and continuously displaying respiratory system compliance and resistance in the form of loops. The aim of this case series is to show how observation of spirometric loops, similar to electrocardiogram or CO2 curve monitoring, can improve safety of anesthetic management in small animals. Spirometric monitoring cases described in this case series are based on use of the anaesthesia monitor Capnomac Ultima with a side stream spirometry sensor. The cases illustrate how recognition and understanding of spirometric loops allows for easy diagnosis of iatrogenic pneumothorax, incorrect ventilator settings, leaks in the system, kinked or partially obstructed endotracheal tube, and spontaneous breathing interfering with intermittent positive-pressure ventilation. The case series demonstrates the potential of spirometry to improve the quality and safety of anesthetic management, and, hence, its use can be recommended during intermittent positive-pressure ventilation and procedures in which interference with ventilation can be expected.

Clinical Practice of Epidural Puncture in Dogs and Cats Assisted by a Commercial Acoustic Puncture Assist Device-Epidural Locator: Preliminary Results.

The objective of this study was to compare an Acoustic Puncture Assist Device-Epidural Locator (APAD-EL) with the "pop sensation" (POP) and "lack of resistance" (LOR) commonly used to confirm penetration of the ligamentum flavum and to ensure correct epidural placement in dogs and cats. We recruited 38 dogs and cats undergoing surgery and receiving epidural analgesia. Two anesthetists performed epidural puncture using the POP and LOR signs. Simultaneously, APAD-EL was used to collect visual and acoustic confirmation during advancement and placement of the needle tip for post hoc evaluation. A positive APAD-EL sign consists of a sudden pressure drop at the needle tip visible on a display and a concomitant pitch change of an acoustic signal. Failure to record a sudden pressure drop is considered a negative APAD sign. Descriptive statistics were used. In 32 patients with positive POP and LOR, the APAD was also positive. In one patient, POP was positive with a negative LOR and APAD result. Five patients had negative POP but positive LOR. Four patients had APAD positive and one (a dog) APAD negative. The study results showed that the APAD-EL information supports the subjective signs of correct needle placement suggested by positive POP and LOR experienced by trained anesthetists. The technique can be useful to assist difficult epidural puncture and as a training and teaching tool.

Publication rate of studies presented at veterinary anaesthesia specialty meetings during the years 2003-2008.

OBJECTIVE: To assess publication rates, factors predicting publication, and discrepancies between conference abstracts and subsequent full-text publications of abstracts from the veterinary meetings of the American College of Veterinary Anesthesiologists and the Association of Veterinary Anaesthetists from 2003 to 2008. STUDY DESIGN: Retrospective cohort study. METHODS: A total of 607 abstracts were identified and a database search (Scopus, PubMed, CAB) was conducted to identify matching publications. Authors of nonmatching abstracts were contacted to participate in a confidential online survey. Risk ratios were used to assess factors predicting publication and these were tested for significance (p < 0.05) using Fisher's exact test. RESULTS: The overall publication rate was 63.3% and the mean (± SD) time to publication was 25 ± 19 months. Factors significantly associated with subsequent full publication (i.e. publication of a full manuscript in a peer-reviewed journal) were continent of origin (North America), study design (experimental studies), specialty (analgesia) and the presence of a source of funding. The principal reasons why studies remained unpublished were lack of time and responsibility lying with co-authors. Minor changes compared with the original abstract were found in 71.6% of all publications. Major changes were noted in 34.6% and the outcome of the study changed in 7.6%. CONCLUSIONS AND CLINICAL RELEVANCE: These data suggest that some of the abstracts reported preliminary findings. Therefore, caution is warranted when quoting abstracts as references in scientific publications. To date, major veterinary journals have not issued recommendations in their author guidelines addressing the use of abstracts as a reference. The authors propose the inclusion of such a statement in author guidelines.

Comparison of respiratory function during TIVA (romifidine, ketamine, midazolam) and isoflurane anaesthesia in spontaneously breathing ponies Part I: blood gas analysis and cardiorespiratory variables.

OBJECTIVE: To compare pulmonary function and gas exchange in ponies during maintenance of anaesthesia with isoflurane or by a total intravenous anaesthesia (TIVA) technique. STUDY DESIGN: Experimental, cross-over study. ANIMALS: Six healthy ponies weighing mean 286 (range 233-388) ± SD 61 kg, age 13 (9-16) ± 3 years. METHODS: The ponies were anaesthetized twice, a minimum of two weeks apart. Following sedation with romifidine [80 µg kg(-1) intravenously (IV)], anaesthesia was induced IV with midazolam (0.06 mg kg(-1)) and ketamine (2.5 mg kg(-1), then maintained either with inhaled isoflurane (Fe'Iso = 1.1 vol%) (T-ISO) or an IV infusion of romifidine (120 µg kg(-1) hour(-1)), midazolam (0.09 mg kg(-1) hour(-1) IV) and ketamine (3.3 mg kg(-1) hour(-1)) (T-TIVA). Ponies were placed in lateral recumbency. Breathing was spontaneous and Fi'O(2) 60%. After an instrumentation/stabilisation period of 30 minutes, arterial and mixed venous blood samples were taken simultaneously every 10 minutes for 60 minutes and analysed immediately. Oxygen extraction ratio (O(2)ER) and venous admixture were calculated. Tidal volume (TV), minute volume (MV), respiratory rate (f(R)), packed cell volume (PCV), arterial blood pressure and heart rate (HR) were measured and recorded. Data were analysed with mixed model anova (α = 0.05). Treatments were compared overall and at two selected time points (T30 and T60) using Bonferroni correction. RESULTS: Arterial and mixed venous partial pressures of O(2) and CO(2), and TV were significantly lower and MV and f(R) were higher in T-TIVA compared to T-ISO. Venous admixture did not differ between treatments. O(2) R was significantly higher in T-TIVA. Mean arterial pressure was higher and HR was lower in T-TIVA compared to T-ISO. CONCLUSIONS AND CLINICAL RELEVANCE: Whilst arterial CO(2) was within an acceptable range during both protocols, the impairment of oxygenation was more pronounced with the T-TIVA evidenced by lower arterial and venous oxygen partial pressures.

Comparison of respiratory function during TIVA and isoflurane anaesthesia in ponies Part II: breathing patterns and transdiaphragmatic pressure.

OBJECTIVE: To compare breathing patterns and transdiaphragmatic pressure during total intravenous (TIVA) and isoflurane anaesthesia in ponies. STUDY DESIGN: Experimental, cross-over study. ANIMALS: Six healthy ponies weighing 286 (233-388) ± 61 kg, age 13 (9-16) ± 3 years. METHODS: Following premedication with romifidine [80 µg kg(-1) intravenously (IV)], general anaesthesia was induced with midazolam (0.06 mg kg(-1) IV) and ketamine (2.5 mg kg(-1) IV) and maintained with either isoflurane (Fe'Iso = 1.1%) (T-ISO) or an IV combination of romifidine (120 µg kg(-1) per hour), midazolam (0.09 mg kg(-1) hour(-1)) and ketamine (3.3 mg kg(-1) hour(-1)) (T-TIVA), while breathing 60% oxygen (FIO(2)). The circumference changes of the rib cage (RC) and abdominal compartment (ABD) were recorded using respiratory ultrasonic plethysmography (RUP). Balloon tipped catheters were placed in the distal oesophagus and the stomach and maximal transdiaphragmatic pressure (Pdi max) was calculated during Mueller's manoeuvre. RESULTS: The breathing pattern T-ISO was more regular and respiratory rate significantly lower compared with T-TIVA. Ponies in T-TIVA showed regularly appearing sighs, which were never observed in T-ISO. Different contribution of the RC and ABD compartments to the breathing pattern was observed with a smaller participation of the RC to the total volume change during T-ISO. Transdiaphragmatic pressures (mean 13.7 ± SD 8.61 versus 23.4 ± 7.27 cmH(2) O, p < 0.0001) were lower in T-TIVA compared to T-ISO [corrected]. The sum of the RC and ABD circumferential changes was lower during T-TIVA compared to T-ISO (6.32 ± 4.42 versus 11.72 ± 4.38 units, p < 0.0001). CONCLUSION AND CLINICAL RELEVANCE: Marked differences in breathing pattern and transdiaphragmatic pressure exist during inhalation- and TIVA and these should be taken into account for clinical estimation of anaesthetic depth.

Variety of non-invasive continuous monitoring methodologies including electrical impedance tomography provides novel insights into the physiology of lung collapse and recruitment ­ case report of an anaesthetized horse.

INTRODUCTION: The use of alveolar recruitment maneuvers during general anaesthesia of horses is a potentially useful therapeutic option for the ventilatory management. While the routine application of recruitments would benefit from the availability of dedicated large animal ventilators their impact on ventilation and perfusion in the horse is not yet well documented nor completely understood. CASE HISTORY: A healthy 533 kg experimental horse underwent general anaesthesia in lateral recumbency. During intermittent positive pressure ventilation a stepwise alveolar recruitment maneuver was performed. MANAGEMENT: Anaesthesia was induced with ketamine and midazolam and maintained with isoflurane in oxygen using a large animal circle system. Mechanical ventilation was applied in pressure ventilation mode and an alveolar recruitment maneuver performed employing a sequence of ascending and descending positive end expiratory pressures. Next to the standard monitoring, which included spirometry, additionally three non-invasive monitoring techniques were used: electrical impedance tomography (EIT), volumetric capnography and respiratory ultrasonic plethysmography. The functional images continuously delivered by EIT initially showed markedly reduced ventilation in the dependent lung and allowed on-line monitoring of the dynamic changes in the distribution of ventilation during the recruitment maneuver. Furthermore, continuous monitoring of compliance, dead space fraction, tidal volumes and changes in end expiratory lung volume were possible without technical difficulties. FOLLOW: up The horse made an unremarkable recovery. CONCLUSION: The novel non-invasive monitoring technologies used in this study provided unprecedented insights into the physiology of lung collapse and recruitment. The synergic information of these techniques holds promise to be useful when developing and evaluating new ventilatory strategies in horses.

Comparison of an infrared anaesthetic agent analyser (Datex-Ohmeda) with refractometry for measurement of isoflurane, sevoflurane and desflurane concentrations.

OBJECTIVE: To assess agreement between infrared (IR) analysers and a refractometer for measurements of isoflurane, sevoflurane and desflurane concentrations and to demonstrate the effect of customized calibration of IR analysers. STUDY DESIGN: In vitro experiment. SUBJECTS: Six IR anaesthetic monitors (Datex-Ohmeda) and a single portable refractometer (Riken). METHODS: Both devices were calibrated following the manufacturer's recommendations. Gas samples were collected at common gas outlets of anaesthesia machines. A range of agent concentrations was produced by stepwise changes in dial settings: isoflurane (0-5% in 0.5% increments), sevoflurane (0-8% in 1% increments), or desflurane (0-18% in 2% increments). Oxygen flow was 2 L minute(-1) . The orders of testing IR analysers, agents and dial settings were randomized. Duplicate measurements were performed at each setting. The entire procedure was repeated 24 hours later. Bland-Altman analysis was performed. Measurements on day-1 were used to yield calibration equations (IR measurements as dependent and refractometry measurements as independent variables), which were used to modify the IR measurements on day-2. RESULTS: Bias ± limits of agreement for isoflurane, sevoflurane and desflurane were 0.2 ± 0.3, 0.1 ± 0.4 and 0.7 ± 0.9 volume%, respectively. There were significant linear relationships between differences and means for all agents. The IR analysers became less accurate at higher gas concentrations. After customized calibration, the bias became almost zero and the limits of agreement became narrower. CONCLUSIONS AND CLINICAL RELEVANCE: If similar IR analysers are used in research studies, they need to be calibrated against a reference method using the agent in question at multiple calibration points overlapping the range of interest.

A novel flow partition device for spirometry during large animal anaesthesia.

OBJECTIVE: We describe and test a novel device for large animal anaesthesia monitoring that uses standard human medicine spirometry sensors. STUDY DESIGN: In-vitro study. METHODS: The 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). RESULTS: Equipped with four D-lite sensors, and a flow of 700 L minute⁻¹ the pressure drop of the FPD was 13.5 cm H2O, resistance 1.17 cm H2O second L⁻¹ and volume (potential dead space) 182 mL, compared to 2.8 cm H2O, 0.24 cm H2O second L⁻¹ and 54 mL respectively for the Horse-lite. The predicted value of the flow partition of » could be confirmed. Limits of agreement were found to be 4.2% in inspiratory direction and 7.1% in expiratory direction. CONCLUSIONS AND CLINICAL RELEVANCE: The 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.

A minimally invasive method for clinical trans-diaphragmatic pressure measurement in anaesthetized dogs.

OBJECTIVE: To measure trans-diaphragmatic pressures, as an indication of diaphragmatic contractility, in anaesthetized dogs breathing normally, or during inspiratory obstruction (Mueller's manoeuvre) in order to assess if the method is practicable for use in clinical circumstances. STUDY DESIGN: Pilot study. ANIMALS: Twenty eight client-owned dogs, ASA I or II, 1-10 years old, 5-30 kg bodyweight, which required anaesthesia for surgery, and were to be positioned in lateral recumbency. METHODS: Following a standardized regimen of premedication and anaesthetic induction, anaesthesia was stabilized and maintained with isoflurane. Two commercially available balloon catheters were introduced orally, and advanced, one into the stomach and one into the mid-third of the oesophagus. Oesophageal and gastric pressures were measured from these catheters, and trans-diaphragmatic pressure (Pdi ) calculated and recorded continuously. At three separate time points during anaesthesia, for one breath, inspiration was obstructed (Mueller's manoeuvre) and Pdi was measured. RESULTS: Placement of the catheters in the stomach was not easy, and failed in three cases. In five dogs, their size resulted in failure of correct placement of catheters. Good traces of all three pressures reflecting respiratory cycles were obtained from 20 dogs. During normal spontaneous breathing (mean ± SD [range]) Pdi was 5 ± 2.1 (3-10) mmHg. During Mueller's manoeuvre, Pdi was 14.6 ± 4.5 (9-21) mmHg. Abnormal waveforms were seen included cardiac oscillations (five dogs), inadequate intra-gastric pressure tracing (one dog), deflections with a double peak (one dog), and multiple artifacts when there was increased heart rate and tachypnoea (two dogs in response to surgery). CONCLUSIONS AND CLINICAL RELEVANCE: Measurement of trans-diaphragmatic pressure with balloon catheters was practicable in suitably sized dogs anaesthetized for clinical purposes and might be a useful tool in the assessment of diaphragmatic function. A range of catheters are required if the technique is to work in all dogs.

The effect of four anaesthetic protocols for maintenance of anaesthesia on trans-diaphragmatic pressure in dogs.

The diaphragm is the main inspiratory muscle and the main indicator of diaphragmatic contractility is the trans-diaphragmatic pressure (Pdi). The aim of this clinical study was to determine the effect of four different anaesthetic protocols on Pdi in anaesthetized healthy dogs. Eighty client-owned dogs were recruited in this clinical study. All the animals received dexmedetomidine and morphine as premedication and propofol for induction. Anaesthesia was maintained with one of four protocols: isoflurane (I), isoflurane with CRI of propofol (IP), isoflurane with CRI of fentanyl (IF), and isoflurane with CRI of ketamine (IK). When the surgical plane of anaesthesia was achieved, two balloon catheters were inserted, one into the stomach and one into the mid-third of the oesophagus for Pdi measurement. Pdi value was the highest in groups I (14.9±4.7 mmHg) and IK (15.2±3.5 mmHg) and the lowest in groups IP (12.2±3.2 mmHg) and IF (12.0±5.9 mmHg). There was a statistically significant difference (p = 0.029) between groups IK and IF. PE'CO2 was statistically significantly higher (p<0.0005) in group IF (7.7±0.8 kPa) than in group IK (6.5±0.7 kPa). Isoflurane alone or isoflurane with ketamine for the maintenance of anaesthesia seem to better preserve the respiratory function and the diaphragmatic contractility than isoflurane with either propofol or fentanyl in dogs. Therefore, the use of isoflurane or isoflurane with ketamine may be of benefit when animals with respiratory problems have to be anaesthetized.