A Retrospective Study on Canine and Feline Mortality during Anaesthesia at a University Clinic in Greece.

This retrospective cohort study investigated the mortality rate during anaesthesia and possible contributing factors in canine and feline population in an academic institution in Greece. Data on 1187 dogs and 250 cats which underwent general anaesthesia from 1 January 2018 to 31 December 2019 at the Veterinary Faculty of the Aristotle University of Thessaloniki were analysed regarding cardiac arrest and mortality. In dogs, the rate of cardiac arrest was 1.1% and the rate of death was 0.6%. In cats, these rates were 2.8% and 0.8%, respectively. The mortality rate in healthy/mild disease (ASA I-II) dogs was 0.1% and in cats was 0.5%. Sick (ASA III-V) dogs exhibited a death rate of 2.6%, while sick cats had a rate of 2.2%. In dogs, ASA status had a positive association with cardiac arrest and mortality, with sick dogs being 23 times more likely to suffer cardiac arrest and 24.5 times more likely to die than healthy/mild disease ones. Other factors associated with cardiac arrest and mortality were the anaesthetic protocol and the use of inotropes. In cats, premedication and inotropic support were related to cardiac arrest and death. Feline anaesthesia involves higher risk, and requires greater vigilance in peri-anaesthetic management than dogs.

Prophylactic Effect of Fenestration on the Recurrence of Thoracolumbar Intervertebral Disc Disease in Dogs.

This systematic review aimed to assess the effect of prophylactic fenestration (PF) on the recurrence of thoracolumbar (TL) intervertebral disc (IVD) disease in dogs. Three online databases were searched (Web of Science, MEDLINE via PubMed, SCOPUS), 115 relevant studies were thoroughly examined by the authors, 29 of which met the pre-defined inclusion criteria for this systematic review. Data about the initial treatment, the performance of PF, the incidence of recurrence, and the site of recurrence were extracted. Most of the studies were deemed to have serious to moderate risk of bias. Out of 5457 dogs, 1264 underwent prophylactic fenestration. A total of 504 cases of suspected or confirmed recurrence were recorded, in which 164 (32.54% of total recurrences and 11.02% of PF cases) were in dogs treated with PF. In order to perform quantitative analysis for the recurrence odds, we conducted a meta-analysis. Five studies were included that met the inclusion criteria. Despite a large number of relevant publications, the quality of the evidence they provide is low. This prevented us from reaching a definitive conclusion on the prophylactic effect of fenestration on recurrence in dogs surgically treated for TL IVDH.

Factors Affecting Intraoperative Gastro-Oesophageal Reflux in Dogs and Cats.

In animals, gastro-oesophageal reflux (GOR) may occur during anaesthesia, and it can lead to severe consequences such as oesophagitis and oesophageal stricture. This systematic review investigates the effect of fasting duration and anaesthetic and nonanaesthetic drugs on GOR in dogs and cats during general anaesthesia. Fifteen clinical studies met the inclusion criteria in this systematic review. In thirteen studies the population was dogs, while in two studies the population was cats. In the meta-analysis, seven studies were included. Four studies on the effect of fasting duration on GOR in dogs were included in the meta-analysis. In total, 191 dogs had a fasting duration less than 5 h, while 311 dogs had a fasting duration more than 5 h. The heterogeneity of the studies was high and statistically significant (p = 0.0002, I2 = 85%), but the overall effect was statistically nonsignificant (p = 0.82, odds ratio = 0.81, 95% CI 0.15, 4.26), in favour of the low fasting duration (<5 h). Concerning the effect of antacids on GOR, three studies were included in the meta-analysis. The heterogeneity of the studies was low and nonsignificant (p = 0.13, I2 = 52%) and the overall effect was statistically nonsignificant (p = 0.24). The low number of studies and the diverse factors affecting the incidence of reflux prevented us from reaching valuable conclusions on the risk factors for GOR.

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.

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.

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.

Anesthesia and perioperative management of a pneumonectomized dog.

Although left- or right-sided pneumonectomy is tolerated by normal dogs, complications impacting the respiratory, cardiovascular, and gastrointestinal systems are not uncommon. Pneumonectomy in dogs results in secondary changes in the remaining lung, which include: decreased compliance and vital capacity; and increased pulmonary vascular resistance potentially leading to right ventricular hypertrophy. Such alterations make the anesthetic management of an animal with one lung particularly challenging. This report describes a dog with a history of left pneumonectomy due to Aspergillus fumigatus pneumonia 3 yr before presentation. The dog presented with a vaginal wall prolapse, and surgical resection of the protruding vaginal wall, ovariectomy, and prophylactic gastropexy were performed. Anesthesia was induced with midazolam, fentanyl, and propofol and was maintained with isoflurane using intermittent positive pressure ventilation and a constant rate infusion of fentanyl. Epidural anesthesia was also used. Recovery and postoperative management were uncomplicated. Intensive hemodynamic and respiratory monitoring and appropriate response and treatment of any detected abnormalities, taking into consideration the pathophysiologic alterations occurring in a pneumonectomized animal, are required for successful perianesthetic management.