Do the Manual or Computer-Controlled Flowmeters Generate Similar Isoflurane Concentrations in Tafonius?

Introduction: Tafonius is an anesthesia machine with computer-controlled monitor and ventilator. We compared the isoflurane fluctuations in the circuit with manual (MF) or computer-driven (CF) flowmeters, investigated the origin of the differences and assessed whether isoflurane concentration time course followed a one-compartment model.Material and Methods: A calibrated TEC-3 isoflurane vaporizer was used. Gas composition and flows were measured using a multiparametric monitor and a digital flowmeter. Measurements included: (1) Effects of various FiO2 with MF/CF on the isoflurane fraction changes in the breathing system during mechanical ventilation of a lung model; wash-in kinetic was fitted to a compartmental model; (2) Gas outflow at the common gas outlet (CGO) with MF/CF at different FiO2; (3) Isoflurane output of the vaporizer at various dial settings with MF/CF set at different flows without and with reduction of the CGO diameter.Results: (1) The 3% targeted isoflurane concentration was not reached; additional time was required to reach specific concentrations with CF (lowest FiO2, longer time). The exponential course fitted a two-compartment model; (2) Set and measured flows were identical with MF. With CF at 0.21 FiO2, flow was intermittently 7.6 L min−1 or zero (mean total: 38% of the set flow); with CF at 1.00 FiO2, flow was 10.6 L min−1 or zero (mean: 4–5.3 L min−1); with 0.21 < FiO2 < 1.00, combined flow was intermittent (maximum output: 15.6 L min−1); (3) With MF, isoflurane output was matching dial setting at 5 L min−1 but was lower at higher flows; with CF generating intermittent flows, isoflurane output was fluctuating. With the 4 mm diameter CGO, isoflurane concentration was close to dial setting with both MF and CF. With a 14 G CGO, isoflurane concentration was lower than dial setting with MF, higher with CF.Conclusions and Clinical Relevance: Using MF or CF led to different isoflurane fraction time course in Tafonius. Flows were lower than set with CF; the TEC-3 did not compensate for high/intermittent flows and pressures; the CGO diameter influenced isoflurane output

A Survey on the Use of Spirometry in Small Animal Anaesthesia and Critical Care

The objective was to document the use of spirometry and ventilation settings in small animal anaesthesia and intensive care through a descriptive, open, online, anonymous survey. The survey was advertised on social media and via email. Participation was voluntary. The google forms platform was used. It consisted of eight sections in English: demographic information, use of spirometry in spontaneously ventilating/mechanically ventilated dogs, need for spirometry, equipment available and calibration status, ventilation modes, spirometry displays, compliance (CRS) and resistance (RRS) of the respiratory system. Simple descriptive analyses were applied. There were 128 respondents. Respondents used spirometry more in ventilated dogs than during spontaneous breathing. Over 3/4 of the respondents considered spirometry essential in “selected” (43%) or “most” cases (33%). Multiple devices and technologies were used. The majority of the respondents were not directly involved in or informed about the calibration of their equipment. Of all displays, pressure-volume loops were the most common. Values of CRS and RRS were specifically monitored in more than 50% of cases by 44% of the respondents only. A variety of ventilation modes was used. Intensivists tend to use smaller VT than anaesthetists. More information on reference intervals of CRS and RRS and technical background on spirometers is required

Propofol-diazepam or propofol-midazolam co-induction in healthy dogs: effects on propofol dosages, cardiovascular and respiratory events

PICO question In healthy dogs, does the use of diazepam or midazolam administered in co-induction with propofol result in a reduction in the dose of propofol required to induce anaesthesia and a decrease in adverse cardiovascular and respiratory events?   Clinical bottom line Category of research question Treatment The number and type of study designs reviewed Eight papers were critically reviewed. A total of six manuscripts were prospective, randomised, blinded, clinical studies. One trial was prospective, randomised, blinded, clinical with a Latin square, incomplete design. One study was retrospective, randomised, blinded, crossover, experimental Strength of evidence Moderate Outcomes reported Variables assessed in this Knowledge Summary included: propofol dose required to induce anaesthesia (considering successful orotracheal intubation as an end point), changes in cardiovascular variables (heart rate, systolic, mean and diastolic blood pressure) and changes in respiratory variables (development of apnoea, changes in respiratory rates) Conclusion In healthy dogs, using propofol-diazepam or propofol-midazolam co-induction resulted in a reduction in propofol dose required to induce anaesthesia in some trials only. Midazolam appeared more effective than diazepam in this context. The dosages, timing and sequence of drug administration seemed relevant. No evidence suggested that using propofol-diazepam or propofol-midazolam co-induction resulted in a reduction of adverse cardiovascular or respiratory events. In addition, although this was out of the scope of the PICO question addressed here, adverse events (e.g. excitement, poorer quality of induction) were reported in several studies when diazepam or midazolam were used in co-induction   How to apply this evidence in practice The application of evidence into practice should take into account multiple factors, not limited to: individual clinical expertise, patient’s circumstances and owners’ values, country, location or clinic where you work, the individual case in front of you, the availability of therapies and resources. Knowledge Summaries are a resource to help reinforce or inform decision making. They do not override the responsibility or judgement of the practitioner to do what is best for the animal in their care

Enantiospecific pharmacokinetics of intravenous dexmedetomidine in beagles.

The goal of this study was to investigate the pharmacokinetic (PK) behaviour of dexmedetomidine in dogs administered as a pure enantiomer versus as part of a racemic mixture. Eight unmedicated intact purpose-bread beagles were included. Two intravenous treatments of either medetomidine or dexmedetomidine were administered at 10- to 14-day intervals. Atipamezole or saline solution was administered intramuscularly 45 min later. Venous blood samples were collected into EDTA collection tubes, and the quantification of dexmedetomidine and levomedetomidine was performed by chiral LC-MS/MS. All dogs appeared sedated after each treatment without complication. Plasma concentrations of levomedetomidine were measured only in the racemic group and were 51.4% (51.4%-56.1%) lower than dexmedetomidine. Non-compartmental analysis (NCA) was performed for both drugs, while dexmedetomidine data were further described using a population pharmacokinetic approach. A standard two-compartment mammillary model with linear elimination with combined additive and multiplicative error model for residual unexplained variability was established for dexmedetomidine. An exponential model was finally retained to describe inter-individual variability on parameters of clearance (Cl1 ) and central and peripheral volumes of distribution (V1 , V2 ). No effect of occurrence, levomedetomidine or atipamezole could be observed on dexmedetomidine PK parameters. Dexmedetomidine did not undergo significantly different PK when administered alone or as part of the racemic mixture in otherwise unmedicated dogs

Characterization of dynamic compliance of the respiratory system in healthy anesthetized dogs

IntroductionIn clinical practice, evaluating dynamic compliance of the respiratory system (C$_{dyn}$) could provide valuable insights into respiratory mechanics. Reference values of C$_{dyn}$ based on body weight have been reported, but various factors may affect them and the evidence is scanty. This study aimed to establish a reference interval for C$_{dyn}$ and identify associated variables.MethodsData were collected from 515 client-owned dogs requiring anesthesia, excluding those with lower airway disease. The dogs were anesthetized, the tracheas intubated, and lungs ventilated at clinicians' discretion across 11 centers in six countries, with no restrictions on anesthesia protocols or ventilation settings, except avoiding inspiratory pauses. Three C$_{dyn}$ measurements from three consecutive breaths per dog were recorded using a standardized form, which also documented factors affecting C$_{dyn}$ identified through literature and an online survey. Various spirometry technologies were used. The substantial variance in C$_{dyn}$ measurements led to a comprehensive analysis using a multiple linear regression model. Multicollinearity (variables highly correlated with each other) was addressed by investigating, transforming, or excluding factors. Initial simple linear regression assessed each variable's individual effect on C$_{dyn}$, followed by a multiple linear regression model constructed via stepwise forward selection and backward elimination.ResultsThe best-fitting model identified a linear relationship between C$_{dyn}$ and body mass when the following conditions were met: high BCS (Body Condition Score), orotracheal tubes <7% smaller than predicted, the use of a D-lite flow sensor, and the absence of a high FIO2 (>80%) exposure for more than 10 minutes before C$_{dyn}$ measurement. In cases where these conditions were not met, additional factors needed to be incorporated into the model. Low (1/9, 2/9, 3/9) and medium (4/9, 5/9) BCS, an orotracheal tube of the predicted size or larger and longer inspiratory times were associated with increased C$_{dyn}$. The use of alternative spirometry sensors, including Ped-lite, or prolonged exposure to high FIO$_{2}$ levels resulted in decreased C$_{dyn}$.Conclusion and clinical relevanceEstablishing a reference interval for C$_{dyn}$ proved challenging. A single reference interval may be misleading or unhelpful in clinical practice. Nevertheless, this study offers valuable insights into the factors affecting C$_{dyn}$ in healthy anesthetized dogs, which should be considered in clinical assessments

A Survey on the Use of Spirometry in Small Animal Anaesthesia and Critical Care

The objective was to document the use of spirometry and ventilation settings in small animal anaesthesia and intensive care through a descriptive, open, online, anonymous survey. The survey was advertised on social media and via email. Participation was voluntary. The google forms platform was used. It consisted of eight sections in English: demographic information, use of spirometry in spontaneously ventilating/mechanically ventilated dogs, need for spirometry, equipment available and calibration status, ventilation modes, spirometry displays, compliance (CRS) and resistance (RRS) of the respiratory system. Simple descriptive analyses were applied. There were 128 respondents. Respondents used spirometry more in ventilated dogs than during spontaneous breathing. Over 3/4 of the respondents considered spirometry essential in “selected” (43%) or “most” cases (33%). Multiple devices and technologies were used. The majority of the respondents were not directly involved in or informed about the calibration of their equipment. Of all displays, pressure-volume loops were the most common. Values of CRS and RRS were specifically monitored in more than 50% of cases by 44% of the respondents only. A variety of ventilation modes was used. Intensivists tend to use smaller VT than anaesthetists. More information on reference intervals of CRS and RRS and technical background on spirometers is require

Do the Manual or Computer-Controlled Flowmeters Generate Similar Isoflurane Concentrations in Tafonius?

Introduction: Tafonius is an anesthesia machine with computer-controlled monitor and ventilator. We compared the isoflurane fluctuations in the circuit with manual (MF) or computer-driven (CF) flowmeters, investigated the origin of the differences and assessed whether isoflurane concentration time course followed a one-compartment model. Material and Methods: A calibrated TEC-3 isoflurane vaporizer was used. Gas composition and flows were measured using a multiparametric monitor and a digital flowmeter. Measurements included: (1) Effects of various FiO2 with MF/CF on the isoflurane fraction changes in the breathing system during mechanical ventilation of a lung model; wash-in kinetic was fitted to a compartmental model; (2) Gas outflow at the common gas outlet (CGO) with MF/CF at different FiO2; (3) Isoflurane output of the vaporizer at various dial settings with MF/CF set at different flows without and with reduction of the CGO diameter. Results: (1) The 3% targeted isoflurane concentration was not reached; additional time was required to reach specific concentrations with CF (lowest FiO2, longer time). The exponential course fitted a two-compartment model; (2) Set and measured flows were identical with MF. With CF at 0.21 FiO2, flow was intermittently 7.6 L min−1 or zero (mean total: 38% of the set flow); with CF at 1.00 FiO2, flow was 10.6 L min−1 or zero (mean: 4–5.3 L min−1); with 0.21 < FiO2 < 1.00, combined flow was intermittent (maximum output: 15.6 L min−1); (3) With MF, isoflurane output was matching dial setting at 5 L min−1 but was lower at higher flows; with CF generating intermittent flows, isoflurane output was fluctuating. With the 4 mm diameter CGO, isoflurane concentration was close to dial setting with both MF and CF. With a 14 G CGO, isoflurane concentration was lower than dial setting with MF, higher with CF. Conclusions and Clinical Relevance: Using MF or CF led to different isoflurane fraction time course in Tafonius. Flows were lower than set with CF; the TEC-3 did not compensate for high/intermittent flows and pressures; the CGO diameter influenced isoflurane output

Propofol-diazepam or propofol-midazolam co-induction in healthy dogs: effects on propofol dosages, cardiovascular and respiratory events

PICO question&#x0D; In healthy dogs, does the use of diazepam or midazolam administered in co-induction with propofol result in a reduction in the dose of propofol required to induce anaesthesia and a decrease in adverse cardiovascular and respiratory events?&#x0D;  &#x0D; Clinical bottom line&#x0D; Category of research question&#x0D; Treatment&#x0D; The number and type of study designs reviewed&#x0D; Eight papers were critically reviewed. A total of six manuscripts were prospective, randomised, blinded, clinical studies. One trial was prospective, randomised, blinded, clinical with a Latin square, incomplete design. One study was retrospective, randomised, blinded, crossover, experimental&#x0D; Strength of evidence&#x0D; Moderate&#x0D; Outcomes reported&#x0D; Variables assessed in this Knowledge Summary included: propofol dose required to induce anaesthesia (considering successful orotracheal intubation as an end point), changes in cardiovascular variables (heart rate, systolic, mean and diastolic blood pressure) and changes in respiratory variables (development of apnoea, changes in respiratory rates)&#x0D; Conclusion&#x0D; In healthy dogs, using propofol-diazepam or propofol-midazolam co-induction resulted in a reduction in propofol dose required to induce anaesthesia in some trials only. Midazolam appeared more effective than diazepam in this context. The dosages, timing and sequence of drug administration seemed relevant. No evidence suggested that using propofol-diazepam or propofol-midazolam co-induction resulted in a reduction of adverse cardiovascular or respiratory events. In addition, although this was out of the scope of the PICO question addressed here, adverse events (e.g. excitement, poorer quality of induction) were reported in several studies when diazepam or midazolam were used in co-induction&#x0D;  &#x0D; How to apply this evidence in practice&#x0D; The application of evidence into practice should take into account multiple factors, not limited to: individual clinical expertise, patient’s circumstances and owners’ values, country, location or clinic where you work, the individual case in front of you, the availability of therapies and resources.&#x0D; Knowledge Summaries are a resource to help reinforce or inform decision making. They do not override the responsibility or judgement of the practitioner to do what is best for the animal in their care.&#x0D;  &#x0D; </jats:p