Comparison between mainstream (Capnostat 5) and a low-flow sidestream capnometer (Capnostream) in mechanically ventilated, sevoflurane-anesthetized rabbits using a Bain coaxial delivery system.

OBJECTIVE: To evaluate agreement between end-tidal carbon dioxide (Pe'CO2) and PaCO2 with sidestream and mainstream capnometers in mechanically ventilated anesthetized rabbits, with two ventilatory strategies. STUDY DESIGN: Prospective experimental study. ANIMALS: A total of 10 New Zealand White rabbits weighing 3.6 ± 0.3 kg (mean ± standard deviation). METHODS: Rabbits anesthetized with sevoflurane were intubated with an uncuffed endotracheal tube (3.0 mm internal diameter) and adequate seal. For Pe'CO2, the sidestream capnometer sampling adapter or the mainstream capnometer was placed between the endotracheal tube and Bain breathing system (1.5 L minute-1 oxygen). PaCO2 was obtained from arterial blood collected every 5 minutes. A time-cycled ventilator delivered an inspiratory time of 1 second and 12 or 20 breaths minute-1. Peak inspiratory pressure was initially set to achieve Pe'CO2 normocapnia of 35-45 mmHg (4.6-6.0 kPa). A total of five paired Pe'CO2 and PaCO2 measurements were obtained with each ventilation mode for each capnometer. Anesthetic episodes were separated by 7 days. Agreement was assessed using Bland-Altman analysis and linear mixed models; p < 0.05. RESULTS: There were 90 and 83 pairs for the mainstream and sidestream capnometers, respectively. The mainstream capnometer underestimated PaCO2 by 12.6 ± 2.9 mmHg (proportional bias 0.44 ± 0.06 mmHg per 1 mmHg PaCO2 increase). With the sidestream capnometer, ventilation mode had a significant effect on Pe'CO2. At 12 breaths minute-1, Pe'CO2 underestimated PaCO2 by 23.9 ± 8.2 mmHg (proportional bias: 0.81 ± 0.18 mmHg per 1 mmHg PaCO2 increase). At 20 breaths minute-1, Pe'CO2 underestimated PaCO2 by 38.8 ± 5.0 mmHg (proportional bias 1.13 ± 0.10 mmHg per 1 mmHg PaCO2 increase). CONCLUSIONS AND CLINICAL RELEVANCE: Both capnometers underestimated PaCO2. The sidestream capnometer underestimated PaCO2 more than the mainstream capnometer, and was affected by ventilation mode.

Agreement of caudal aortic arterial blood pressure with oscillometry using two cuff widths placed on the thoracic or pelvic limbs of sevoflurane-anesthetized rabbits.

OBJECTIVE: To evaluate agreement with central systemic arterial pressure of an oscillometer and two cuff widths placed on the thoracic or pelvic limbs. STUDY DESIGN: Prospective experimental study. ANIMALS: A group of nine New Zealand White rabbits weighing 3.5 ± 0.3 kg. METHODS: Rabbits were sedated with dexmedetomidine and midazolam, then anesthetized with ketamine and sevoflurane. The femoral artery was surgically exposed and a 20 gauge, 5 cm catheter inserted to measure systolic (SAP), mean (MAP) and diastolic (DAP) blood pressure at the iliac artery and caudal aorta junction. Adjustments of vaporizer dial and dobutamine infusion provided a range of invasive blood pressure (IBP). Two measurements of IBP were recorded during the oscillometer cycling phase, and the mean value was used in analyses. Oscillometer cuffs of bladder width 2.0 cm (S1) and 2.5 cm (S2) were placed proximal to the carpus and tarsus. Cuff width to circumference ratio was calculated. Oscillometer SAP, MAP and DAP were paired with corresponding IBP values. Agreement was assessed using linear mixed models (p < 0.05). RESULTS: Cuff ratios for both limbs were 41% (S1 cuff) and 50% (S2 cuff) and 122-139 paired observations were obtained. There was significant limb × cuff interaction with SAP and MAP. The oscillometer overestimated SAP and MAP on the pelvic limb and underestimated SAP and MAP on the thoracic limb. For SAP, the oscillometer overestimated by constant bias (-19 ± 2 mmHg) and proportional bias (0.28 ± 0.02 mmHg per 1 mmHg increase). For MAP, the oscillometer underestimated by constant bias (4 ± 2 mmHg) and was worse with S2 on the thoracic limb. Overestimation was similar between cuffs on the pelvic limb. For DAP, the oscillometer underestimated by constant bias (15 ± 2 mmHg). CONCLUSIONS AND CLINICAL RELEVANCE: Cuff S1 on the thoracic limb provided best estimation of MAP.

Evaluation of lung ventilation distribution using electrical impedance tomography in standing sedated horses with capnoperitoneum.

OBJECTIVE: To determine changes in distribution of lung ventilation with increasing intra-abdominal pressure (IAP) from carbon dioxide (CO2) insufflation in standing sedated horses. STUDY DESIGN: Prospective experimental study. ANIMALS: A group of six healthy adult horses. METHODS: Each horse was sedated with acepromazine, detomidine and butorphanol and sedation maintained with a detomidine infusion. The horse was restrained in a stocks system and a 32 electrode electrical impedance tomography (EIT) belt was wrapped around the thorax at the fifth-sixth intercostal space. EIT images and arterial blood samples for PaO2 and PaCO2, pH and lactate concentration were obtained during capnoperitoneum at 0 (baseline A), 5, 8 and 12 mmHg as IAP increased and at 8, 5, 0 (baseline B) mmHg as IAP decreased. At each IAP, after a 2 minute stabilization period, EIT images were recorded for ≥ 2 minutes to obtain five consecutive breaths. Statistical analysis was performed using anova for repeated measures with Geisser-Greenhouse correction and a Tukey's multiple comparison test for parametric data. The relationship between PaO2 and the center of ventilation in the ventral-dorsal (CoV-VD) and right-left (CoV-RL) directions or total impedance change as a surrogate for tidal volume (ΔZVT) were tested using linear regression analysis. Significance was assumed when p ≤ 0.05. RESULTS: There were no significant changes in CoV-VD, CoV-RL, PaO2, PaCO2, lactate concentration, pH, heart rate and respiratory rate with targeted IAP. There was a significant decrease in ΔZVT compared with baseline A at 5 mmHg IAP as IAP was increased. CONCLUSIONS AND CLINICAL RELEVANCE: Capnoperitoneum causes a significant decrease in ΔZVT in standing sedated horses with increasing IAP.

Depletion of pulmonary intravascular macrophages rescues inflammation-induced delayed neutrophil apoptosis in horses.

The objective of this study was to determine the effect of pulmonary intravascular macrophage depletion on systemic inflammation and ex vivo neutrophil apoptosis using an experimental model of intestinal ischemia and reperfusion injury in horses. Neutrophils were isolated before and after surgery from horses that were randomized to three treatment groups, namely, sham celiotomy (CEL, n = 4), intestinal ischemia and reperfusion (IR, n = 6), and intestinal ischemia and reperfusion with gadolinium chloride treatment to deplete pulmonary intravascular macrophages (PIMs, IRGC, n = 6). Neutrophil apoptosis was assessed with Annexin V and propidium iodide staining quantified with flow cytometry and caspase-3, caspase-8, and caspase-9 activities in neutrophil lysates. All horses experienced a systemic inflammatory response following surgery. Following surgery, ex vivo neutrophil apoptosis was significantly delayed after 12 or 24 h in culture, except in IRGC horses (12 h: CEL: P = 0.03, IR: P = 0.05, IRGC: P = 0.2; 24 h: CEL: P = 0.001, IR: P = 0.004, IRGC: P = 0.3). Caspase-3, caspase-8, and caspase-9 activities were significantly reduced in neutrophils isolated after surgery and cultured for 12 h in IR horses, but not in IRGC horses (IR caspase-3: P = 0.002, IR caspase-8: P = 0.002, IR caspase-9: P = 0.04). Serum TNF-α concentration was increased in IRGC horses for 6-18 h following jejunal ischemia. Following surgery, ex vivo equine neutrophil apoptosis was delayed via downregulation of caspase activity, which was ameliorated by PIM depletion potentially via upregulation of TNF-α.

Evaluation of the perioperative stress response from dexmedetomidine infusion alone, with butorphanol bolus or remifentanil infusion compared with ketamine and morphine infusions in isoflurane-anesthetized horses.

OBJECTIVE: To evaluate perioperative stress-related hormones in isoflurane-anesthetized horses administered infusions of dexmedetomidine alone or with butorphanol or remifentanil, compared with ketamine-morphine. STUDY DESIGN: Randomized, prospective, nonblinded clinical study. ANIMALS: A total of 51 horses undergoing elective surgical procedures. METHODS: Horses were premedicated with xylazine, anesthesia induced with ketamine-diazepam and maintained with isoflurane and one of four intravenous infusions. Partial intravenous anesthesia (PIVA) was achieved with dexmedetomidine (1.0 µg kg-1 hour-1; group D; 12 horses); dexmedetomidine (1.0 µg kg-1 hour-1) and butorphanol bolus (0.05 mg kg-1; group DB; 13 horses); dexmedetomidine (1.0 µg kg-1 hour-1) and remifentanil (3.0 µg kg-1 hour-1; group DR; 13 horses); or ketamine (0.6 mg kg-1 hour-1) and morphine (0.15 mg kg-1, 0.1 mg kg-1 hour-1; group KM; 13 horses). Infusions were started postinduction; butorphanol bolus was administered 10 minutes before starting surgery. Blood was collected before drugs were administered (baseline), 10 minutes after ketamine-diazepam, every 30 minutes during surgery and 1 hour after standing. Mean arterial pressure (MAP), pulse rate, end-tidal isoflurane concentration, cortisol, nonesterified fatty acids (NEFA), glucose and insulin concentrations were compared using linear mixed models. Significance was assumed when p < 0.05. RESULTS: Within D, cortisol was lower at 120-180 minutes from starting surgery compared with baseline. Cortisol was higher in KM than in D at 60 minutes from starting surgery. Within all groups, glucose was higher postinduction (except DR) and 60 minutes from starting surgery, and insulin was lower during anesthesia and higher after standing compared with baseline. After standing, NEFA were higher in KM than in DB. In KM, MAP increased at 40-60 minutes from starting surgery compared with 30 minutes postinduction. CONCLUSIONS AND CLINICAL RELEVANCE: Dexmedetomidine suppressed cortisol release more than dexmedetomidine-opioid and ketamine-morphine infusions. Ketamine-morphine PIVA might increase catecholamine activity.

Evaluation of intramuscular sodium nitroprusside injection to improve oxygenation in white-tailed deer (Odocoileus virginianus) anesthetized with medetomidine-alfaxalone-azaperone.

OBJECTIVE: In ungulates, α2-adrenergic agonists can decrease oxygenation possibly through alteration of pulmonary perfusion. Sodium nitroprusside can decrease pulmonary vascular resistance (PVR) and increase cardiac output (Q˙t) through vasodilation. The objective was to determine if sodium nitroprusside would improve pulmonary perfusion and attenuate the increased alveolar-arterial (a-a) gradient resulting from medetomidine-azaperone-alfaxalone (MAA) administration. STUDY DESIGN: Prospective, randomized, crossover study with a 2 week rest period. ANIMALS: A group of eight adult female captive white-tailed deer (Odocoileus virginianus). METHODS: Deer were administered MAA intramuscularly (IM), and auricular artery and pulmonary artery balloon catheters were placed. Deer spontaneously breathed air. Saline or sodium nitroprusside (0.07 mg kg-1) were administered IM 40 minutes after MAA injection. Heart rate (HR), mean arterial pressure (MAP), mean pulmonary arterial pressure (MPAP), pulmonary artery occlusion pressure (PAOP), right atrial pressure (RAP), Q˙t, arterial pH, PaCO2 and PaO2 were obtained immediately before nitroprusside injection (baseline) and 5, 10 and 15 minutes afterwards. Mixed venous blood samples were obtained at baseline and at 5 minutes. Systemic vascular resistance (SVR), PVR, intrapulmonary shunt fraction (Q˙s/Q˙t), a-a gradient, oxygen delivery (D˙O2) and oxygen extraction ratio (O2ER) were calculated. Statistical analysis was performed with repeated measures analysis of variance with correction factors. A p value < 0.05 was considered significant. RESULTS: With nitroprusside, MAP, MPAP, PAOP, RAP, SVR and O2ER significantly decreased and HR, Q˙t and D˙O2 increased compared with baseline and between treatments. There was a significant decrease in PVR and a-a gradient and increase in PaO2 compared with baseline and saline treatment. Changes were not sustained. CONCLUSIONS AND CLINICAL RELEVANCE: Nitroprusside temporarily changed hemodynamic variables, increased PaO2 and decreased a-a gradient. Nitroprusside possibly led to better pulmonary perfusion of ventilated alveoli. However, IM nitroprusside at this dose is not recommended because of severe systemic hypotension and short action.

Plasma histamine concentrations in horses administered sodium penicillin, guaifenesin-xylazine-ketamine and isoflurane with morphine or butorphanol.

OBJECTIVE: Various drugs administered to horses undergoing surgical procedures can release histamine. Histamine concentrations were evaluated in horses prepared for surgery and administered butorphanol or morphine intraoperative infusions. STUDY DESIGN: Prospective studies with one randomized. ANIMALS: A total of 44 client-owned horses. METHODS: In one study, anesthesia was induced with xylazine followed by ketamine-diazepam. Anesthesia was maintained with guaifenesin-xylazine-ketamine (GXK) during surgical preparation. For surgery, isoflurane was administered with intravenous (IV) morphine (group M: 0.15 mg kg-1 and 0.1 mg kg-1 hour-1; 15 horses) or butorphanol (group B: 0.05 mg kg-1 and 0.01 mg kg-1 hour-1; 15 horses). Histamine and morphine concentrations were measured using enzyme-linked immunoassay before opioid injection (time 0), and after 1, 2, 5, 30, 60 and 90 minutes. In a subsequent study, plasma histamine concentrations were measured in 14 horses before drug administration (baseline), 15 minutes after IV sodium penicillin and 15 minutes after starting GXK IV infusion. Statistical comparison was performed using anova for repeated measures. Pearson correlation compared morphine and histamine concentrations. Data are presented as mean ± standard deviation. Significance was assumed when p ≤ 0.05. RESULTS: With histamine, differences occurred between baseline (3.2 ± 2.4 ng mL-1) and GXK (5.2 ± 7.1 ng mL-1) and between baseline and time 0 in group B (11.9 ± 13.4 ng mL-1) and group M (11.1 ± 12.4 ng mL-1). No differences occurred between baseline and after penicillin or between groups M and B. Morphine concentrations were higher at 1 minute following injection (8.1 ± 5.1 ng mL-1) than at 30 minutes (4.9 ± 3.1 ng mL-1) and 60 minutes (4.0 ± 2.5 ng mL-1). Histamine correlated with morphine at 2, 30 and 60 minutes. CONCLUSIONS AND CLINICAL RELEVANCE: GXK increased histamine concentration, but concentrations were similar with morphine and butorphanol.

Influence of maternal, anesthetic, and surgical factors on neonatal survival after emergency cesarean section in 78 dogs: A retrospective study (2002 to 2020).

Neonatal mortality rate (NMR) may be affected by maternal physical condition, anesthesia, and uterine incision or en-bloc neonate removal. The association of selected factors with number of dogs with dead puppies at hospital discharge was evaluated using 78 records. Data obtained at admittance for emergency cesarean section included: age, small or large body size, rectal temperature, packed cell volume, serum total protein, blood urea nitrogen, glucose, puppy in pelvic canal, and heart rate. Administration of opioids, propofol, alfaxalone, isoflurane, and sevoflurane, and anesthesia/surgical times and surgical technique were evaluated using Fisher's exact tests. There were 238 live puppies and 38 dogs had 58 dead puppies; the NMR was 19.6%. Mortality was associated with puppy in the pelvic canal (P = 0.003) and duration of anesthesia > 80 minutes (P = 0.029). Age > 8 years (P = 0.054) and induction time to start of surgery > 30 minutes (P = 0.17) may be associated with mortality. Expedient cesarean section with obstructive dystocia and an induction time to start of surgery < 30 minutes are important for puppy survival.

Influence des facteurs maternels, anesthésiques et chirurgicaux sur la survie néonatale après césarienne d'urgence chez 78 chiens : Une étude rétrospective (2002 à 2020). Le taux de mortalité néonatale (TMN) peut être affecté par l'état physique de la mère, l'anesthésie et l'incision utérine ou l'ablation en bloc du nouveau-né. L'association de facteurs sélectionnés avec le nombre de chiens avec des chiots morts à la sortie de l'hôpital a été évaluée à l'aide de 78 dossiers. Les données obtenues à l'admission pour une césarienne d'urgence comprenaient : l'âge, la taille corporelle petite ou grande, la température rectale, l'hématocrite, les protéines sériques totales, l'azotémie, le glucose, la présence de chiot dans le canal pelvien et la fréquence cardiaque. L'administration d'opioïdes, de propofol, d'alfaxalone, d'isoflurane et de sévoflurane, ainsi que les temps d'anesthésie/de chirurgie et la technique chirurgicale ont été évalués à l'aide des tests exacts de Fisher. Il y avait 238 chiots vivants et 38 chiens avaient 58 chiots morts; le TMN était de 19,6 %. La mortalité était associée la présence de chiot dans le canal pelvien (P = 0,003) et à la durée de l'anesthésie > 80 minutes (P = 0,029). Un âge > 8 ans (P = 0,054) et un délai d'induction avant le début de la chirurgie > 30 minutes (P = 0,17) peuvent être associés à la mortalité. Une césarienne opportune lors de dystocie obstructive et un temps d'induction avant le début de la chirurgie < 30 minutes sont importants pour la survie du chiot.(Traduit par Dr Serge Messier).

Myoclonus and hypersensitivity of the hind limbs and tail with urinary retention following neuraxial administration of morphine in a cat.

An adult female domestic shorthair cat developed myoclonus, muscle rigidity, and hypersensitivity of the hind limbs and tail with urinary retention following neuraxial administration of morphine. Myoclonic contractions resolved following treatment with midazolam and a urinary catheter was placed until normal micturition returned. The cat was clinically normal 36 hours after neuraxial morphine injection. The cat underwent a second surgery without neuraxial morphine and control of postoperative pain required more intervention. Key clinical message: Neuraxial morphine may cause myoclonus and urinary retention. The response to pharmacological treatment of myoclonus is varied, but a benzodiazepine drug may be effective.

Myoclonie et hypersensibilité des membres postérieurs et de la queue avec rétention urinaire après administration neuraxiale de morphine chez un chat. Une chatte domestique à poils courts adulte a développé une myoclonie, une rigidité musculaire et une hypersensibilité des membres postérieurs et de la queue avec rétention urinaire après l'administration neuraxiale de morphine. Les contractions myocloniques se sont résolues après un traitement avec du midazolam et un cathéter urinaire a été placé jusqu'à ce que les mictions normales reviennent. Le chat était cliniquement normal 36 heures après l'injection neuraxiale de morphine. Le chat a subi une deuxième intervention chirurgicale sans morphine neuraxiale et le contrôle de la douleur postopératoire a nécessité plus d'intervention.Message clinique clé:La morphine neuraxiale peut provoquer une myoclonie et une rétention urinaire. La réponse au traitement pharmacologique de la myoclonie est variée, mais un médicament à base de benzodiazépine peut être efficace.(Traduit par Dr Serge Messier).

Comparison of mainstream (Capnostat 5) and two low-flow sidestream capnometers (VM-2500-S and Capnostream) in spontaneously breathing rabbits anesthetized with a Bain coaxial breathing system.

OBJECTIVE: To evaluate agreement with PaCO2 of two low sampling rate sidestream capnometers and a mainstream capnometer in rabbits and the effect of using high fresh gas flow from a Bain coaxial breathing system. STUDY DESIGN: Prospective, crossover study. ANIMALS: A total of 10 New Zealand White rabbits weighing 3.4 ± 0.3 kg [mean ± standard deviation (SD)]. METHODS: Two sidestream analyzers (Viamed VM-2500-S and Capnostream 35) with a sampling rate of 50 mL minute-1 and a mainstream capnometer (Capnostat 5) were tested. All capnometers used infrared spectroscopy and advanced microprocessor technology. Rabbits were anesthetized and intubated with noncuffed endotracheal tubes of 3 mm internal diameter and adequate seal. A sidestream sampling adapter or the mainstream capnometer was attached to the endotracheal tube and connected to a Bain coaxial breathing system. Oxygen (1.5 L minute-1) delivered sevoflurane to maintain anesthesia. An auricular artery catheter allowed blood sampling for PaCO2 analysis corrected to rectal temperature. Inspired and end-tidal carbon dioxide (Pe'CO2) measurements were recorded during blood sample withdrawal. From each rabbit, 10 paired PaCO2/Pe'CO2 measurements were obtained. Each rabbit was recovered from anesthesia and was anesthetized again with an alternate capnometer after 1 week. Data were analyzed using Bland-Altman and two-way anova for repeated measures. RESULTS: Analysis included 100 paired samples. Negative bias reflects underestimation of PaCO2. Bland-Altman mean (±1.95 SD) was -16.7 (-35.2 to 1.8) mmHg for Capnostat 5, -27.9 (-48.6 to -7.2) mmHg for Viamed, and -18.1 (-34.3 to -1.9) mmHg for Capnostream. Viamed PaCO2-Pe'CO2 gradient was greater than other two capnometers. CONCLUSIONS: All three capnometers underestimated PaCO2. Capnostat 5 and Capnostream performed similarly. CLINICAL RELEVANCE: These capnometers underestimated PaCO2 in spontaneously breathing rabbits anesthetized using a Bain coaxial breathing system with high fresh gas flows.

Retrospective comparison of equine hemoglobin oxygen saturation measured by a human-specific co-oximeter, or derived from an algorithm using temperature-corrected and -uncorrected oxygen tension.

OBJECTIVE: Hemoglobin oxygen saturation (SO2) is measured by co-oximetry (SO2cox) or calculated from partial pressure of oxygen (PO2) using algorithms (SO2alg). To compare venous and systemic arterial blood sample data retrospectively and to examine whether temperature correction of PO2 is important. STUDY DESIGN: Retrospective study. ANIMALS: A group of 21 healthy, adult, sedated or anesthetized horses. METHODS: Mixed-venous and systemic arterial blood samples (1 mL) were anaerobically collected using commercial preheparinized syringes from the right ventricle and facial artery, respectively. Blood was analyzed using a commercial gas analyzer and human-specific co-oximeter within 10 minutes of collection or stored on ice and analyzed within 30 minutes. PO2 was measured at 37 °C and corrected using body temperature (Tcore) from a pulmonary artery catheter thermistor. SO2cox and hemoglobin subtypes were measured by co-oximetry (37 °C). An algorithm developed for Thoroughbred horse blood was used to calculate SO2alg using PO2 at 37 °C and SO2algcorr with PO2 corrected to Tcore. SO2alg and SO2algcorr were each paired with SO2cox using Bland-Altman (repeated measures) ratio of SO2alg/SO2cox (204 samples). RESULTS: SO2alg overestimated SO2cox when PO2 was <80 mmHg (10.7 kPa); ratio and limits of agreement: 1.2 (0.9-1.6) but became accurate when PO2 was ≥80 mmHg: 1.0 (1.0-1.0). With all data, SO2algcorr did not differ from SO2alg:1.1 (0.8-1.4). Methemoglobin (FMetHb) and carboxyhemoglobin (FCOHb) were significantly higher in venous [FMetHb: median (range): 1.8 (0-2.9)%; FCOHb: 0.1 (0-2)%] than in arterial blood [FMetHb: 0.5 (0-2.2)%; FCOHb: 0 (0-0.3)%]. CONCLUSIONS: The algorithm appeared robust when PO2 was ≥80 mmHg (10.7 kPa) but overestimated when PO2 was lower. Temperature correction was not important within 34.9-37.3 °C. CLINICAL RELEVANCE: SO2alg overestimation in venous blood can result in calculation of higher intrapulmonary shunt fraction than SO2cox values.

Total intravenous anesthesia with alfaxalone, dexmedetomidine and remifentanil in healthy foals undergoing abdominal surgery.

OBJECTIVE: To evaluate effects of anesthesia induced with alfaxalone and maintained with alfaxalone, dexmedetomidine and remifentanil infusions in foals. STUDY DESIGN: Prospective, experimental study. ANIMALS: A group of six healthy foals [median (range) 11 (8-33) days] undergoing abdominal surgery. METHODS: Intravenous (IV) dexmedetomidine (3-7µgkg-1) provided sedation for insertion of a pulmonary artery catheter. IV anesthesia was induced with alfaxalone (2mgkg-1) and maintained with alfaxalone (6mgkg-1hour-1), dexmedetomidine (1µgkg-1hour-1) and remifentanil (3µgkg-1hour-1). Foals were endotracheally intubated and lungs were mechanically ventilated with oxygen. Cardiac output (thermodilution), heart rate and systemic arterial pressure were measured. Arterial and mixed venous blood was analyzed for PO2 and PCO2, and glucose, lactate and electrolyte concentrations. Anesthetic depth was subjectively assessed. Systemic vascular resistance (SVR), oxygen utilization and intrapulmonary shunt were calculated. Preinduction (PB) or 10 minutes postinduction (+10B) data were used as baselines with one-way analysis of variance for repeated measures. Data are mean ± standard deviation; significance was p ≤ 0.05. RESULTS: Duration of anesthesia was 129 ± 22minutes. One foal was administered additional alfaxalone (0.5mgkg-1) following induction. Cardiac index decreased to 107 ± 31 and 87 ± 21mLkg-1minute-1 at 60 and 80minutes, respectively, compared with PB (157 ± 33mLkg-1minute-1). SVR increased to 1223 ± 166dynessecond-1cm-5 at 80minutes compared with +10B (704 ± 247dynessecond-1cm-5). Mean arterial pressures were 63-128mmHg. Time from stopping infusions to standing was 46-106minutes. All foals were hypothermic (<36°C) and three foals were administered atipamezole (0.05mgkg-1) intramuscularly during recovery. CONCLUSION: and clinical relevance Combined alfaxalone-dexmedetomidine-remifentanil provided suitable anesthesia to permit laparotomy in foals. At the doses evaluated, prolonged recovery may occur.

Effects of alfaxalone, thiopental, or propofol and diazepam on laryngeal motion in healthy dogs.

Laryngeal function is assessed by direct visualization of the larynx under a light plane of anesthesia. This study compared the effects of 3 anesthetic protocols on arytenoid motion in healthy dogs. Eight dogs were randomly assigned to receive alfaxalone, propofol and diazepam, or thiopental. Videolaryngoscopy was performed and still images at maximum inspiration and expiration were used to measure the area and height of the glottal gap. The normalized glottal gap area (NGGA = area in pixels/height2) was calculated. The NGAA change was defined as the difference between NGAA during inspiration and exhalation. Data were analyzed using Mann-Whitney and Kruskal-Wallis tests, P-values < 0.05 were considered statistically significant. No significant difference among induction protocols was found when comparing NGGA change after induction or before recovery. Alfaxalone and propofol/diazepam are useful for evaluation of laryngeal function when administered to effect and a light plane of anesthesia is maintained.

Effets de l'alfaxalone, du thiopental ou du propofol et du diazépam sur le mouvement du larynx chez des chiens en santé. La fonction du larynx est évaluée par visualisation directe du larynx sous une légère anesthésie. Cette étude a comparé les effets de trois protocoles anesthésiques sur le mouvement aryténoïde chez des chiens en santé. Huit chiens ont été assignés au hasard pour recevoir de l'alfaxalone, du propofol et du diazépam ou du thiopental. Une vidéo-laryngoscopie a été réalisée et des images fixes à l'inspiration et à l'expiration maximales ont été utilisées pour mesurer la région et la hauteur de l'écart glottal. La région normalisée de l'écart glottal (RNEG = région en pixels/hauteur2) a été calculée. Le changement RNEG a été défini comme la différence entre le RNEG durant l'inspiration et l'expiration. Les données ont été analysées en utilisant les tests de Mann-Whitney et Kruskal-Wallis, les valeurs-P < 0,05 étaient considérées comme étant significatives sur le plan statistique. Aucune différence significative n'a été trouvée parmi les protocoles d'induction lors de la comparaison du changement RNEG après l'induction ou le réveil. L'alfaxalone et le propofol/diazépam sont utiles pour l'évaluation de la fonction du larynx lorsqu'ils sont administrés jusqu'à l'effet et qu'une légère anesthésie est maintenue.(Traduit par Isabelle Vallières).

The effect of anesthetic drug choice on accuracy of high-definition oscillometry in laterally recumbent horses.

OBJECTIVE: To determine the accuracy of high-definition oscillometry (HDO) for arterial pressure measurement during injectable or inhalation anesthesia in horses. STUDY DESIGN: Prospective, clinical study. ANIMALS: Twenty-four horses anesthetized for procedures requiring lateral recumbency. METHODS: Horses were premedicated with xylazine, and anesthesia induced with diazepam-ketamine. Anesthesia was maintained with xylazine-ketamine-guaifenesin combination [TripleDrip (TD; n = 12) or isoflurane (ISO; n = 12)]. HDO was used to obtain systolic (SAP), mean (MAP) and diastolic (DAP) arterial pressures, and heart rate (HR) using an 8-cm-wide cuff around the proximal tail. Invasive blood pressure (IBP), SAP, MAP, DAP and HR were recorded during HDO cycling. Bland-Altman analysis for repeated measures was used to compare HDO and IBP for all measurements. The generalized additive model was used to determine if means in the differences between HDO and IBP were similar between anesthetic protocols for all measurements. RESULTS: There were >110 paired samples for each variable. There was no effect of anesthetic choice on HDO performance, but more variability was present in TD compared with ISO. Skewed data required log-transformation for statistical comparison. Using raw data and standard Bland-Altman analysis, HDO overestimated SAP (TD, 3.8 ± 28.3 mmHg; ISO, 3.5 ± 13.6 mmHg), MAP (TD, 4.0 ± 23.3 mmHg; ISO, 6.3 ± 10.0 mmHg) and DAP (TD, 4.0 ± 21.2 mmHg; ISO, 7.8 ± 13.6 mmHg). In TD, 26-40% HDO measurements were within 10 mmHg of IBP, compared with 60-74% in ISO. Differences between HDO and IBP for all measurements were similar between anesthetic protocols. The numerical difference between IBP and HDO measurements for SAP, MAP and DAP significantly decreased as cuff width:tail girth ratio increased toward 40%. CONCLUSION AND CLINICAL RELEVANCE: More variability in HDO occurred during TD. The cuff width:tail girth ratio is important for accuracy of HDO.

Cardiopulmonary effects of pleural insufflation with CO2 during two-lung ventilation in dorsally recumbent anesthetized horses.

OBJECTIVE: To record the cardiopulmonary effects of pleural CO2 positive pressure insufflation in anesthetized horses. STUDY DESIGN: Prospective study. ANIMALS: Seven horses (mean ± standard deviation, 530.9 ± 68.1 kg) undergoing terminal surgery. METHODS: Horses were sedated with xylazine. Anesthesia was induced with ketamine-propofol and maintained with isoflurane, positive pressure ventilation, detomidine infusion, and butorphanol with the horses in dorsal recumbency. Baseline measurements were cardiac output, heart rate, pulmonary and systemic arterial and right atrial blood pressures, body temperature, expired and inspired gas concentrations, and arterial and mixed venous blood gases, electrolytes, glucose, and lactate concentrations. An 18 gauge 6.6 cm needle was inserted into the right pleural cavity midway between the sternum and dorsal midline in the sixth or seventh intercostal space for pleural pressure (PP) measurement. A 14 gauge 18 cm needle placed 5 cm below the previous needle allowed CO2 insufflation into the pleural cavity. All measurements were repeated after: needle insertion, at 2, 5, and 8 mmHg PPs, and after pleural gas removal (GR). Data were compared with baseline using one-way analysis of variance with repeated measures. p < 0.05 was considered significant. RESULTS: Actual PPs were within 1.1 mmHg of the targeted PP. Pulmonary systolic and mean arterial pressures, alveolar dead space to tidal volume ratio, and isoflurane requirements increased at 8 mmHg PP and GR. Cardiac index decreased at 5 mmHg PP. Stroke index decreased at 2 mmHg PP to GR. PaO2 decreased at 5 mmHg PP to GR. PaCO2 increased at 8 mmHg PP and GR. Oxygen delivery decreased at 5 and 8 mmHg PP. Intrapulmonary shunt fraction and lactate concentration increased with GR. CONCLUSIONS AND CLINICAL RELEVANCE: Severe adverse cardiopulmonary effects arise from CO2 positive pressure insufflation into the right hemithorax in dorsally recumbent isoflurane-anesthetized horses. PP should be ≤2 mmHg.

Basics of monitoring equipment.

Monitoring equipment has become reliable and affordable for use in general veterinary practice. This article provides a guide to technology, troubleshooting, and obtaining quality data using 4 non-invasive techniques that are commonly used in practice. Pulse oximetry estimates oxygen saturation of hemoglobin in arterial blood, capnography measures the carbon dioxide content of inspired and expired gas, and either Doppler shift detection or oscillometry can be used to measure blood pressure. These useful non-invasive techniques all rely on adequate perfusion of the tissues for optimum function.

Éléments fondamentaux de l'équipement de monitorage. L'équipement de monitorage est devenu fiable et abordable pour utilisation dans la pratique vétérinaire générale. Le présent article présente un guide sur la technologie, le diagnostic de panne et l'obtention de données de qualité en utilisant quatre techniques non invasives qui sont communément utilisées en pratique. L'oxymétrie pulsée estime la saturation en oxygène de l'hémoglobine dans le sang artériel, la capnographie mesure le contenu en gaz carbonique du gaz inspiré et expiré et la détection du déplacement Doppler ou l'oscillométrie peut être utilisée pour mesurer la pression artérielle. Ces techniques non invasives s'appuient toutes sur une perfusion adéquate des tissus pour une fonction optimale.(Traduit par Isabelle Vallières).

Effect of Arthroscopic Lavage on Systemic and Synovial Fluid Serum Amyloid A in Healthy Horses.

OBJECTIVE: To evaluate the effect of arthroscopic lavage on systemic serum amyloid A (SAA) and SAA, total protein, nucleated cell count, and percentage of neutrophils in synovial fluid in healthy horses. STUDY DESIGN: Prospective experimental study. ANIMALS: Healthy adult horses (n = 6). METHODS: Middle carpal joints were randomly assigned to 1 of 2 treatments: arthrocentesis (controls) or arthroscopic lavage, with 30 day washout period between treatments. Synovial fluid and blood samples were collected at 0, 24, 48, 72, 96, and 120 hours. Measurements included systemic and synovial fluid SAA, as well as total protein, nucleated cell count, and percentages of neutrophils in synovial fluid. Data were analyzed by median quantile regression and Wilcoxon signed-rank test and significance level set at P < .05. RESULTS: Systemic and synovial fluid SAA did not increase from baseline (except systemic SAA at 24 hours for both treatments) and were not significantly different between treatments. Total protein values were significantly increased after arthroscopic lavage (except at 96 hours) but not in controls at all time points. With both treatments, nucleated cell counts significantly increased from baseline values at all time points. Percentages of neutrophils were significantly increased after arthroscopic lavage at all time points, but only at 24 hours in controls. CONCLUSION: Total protein, nucleated cell count, and percentage of neutrophils in synovial fluid were significantly increased after arthroscopic lavage; however, synovial fluid SAA was not affected by this procedure. Further research is warranted to validate synovial fluid SAA as a monitoring tool during treatment of septic arthritis.

A pilot study evaluating laparoscopic closure of the nephrosplenic space using an endoscopic suturing device in standing horses.

This study evaluated the use of an articulating automated suturing device for laparoscopic closure of the nephrosplenic space in standing horses. Closure of the nephrosplenic space was performed in 4 horses using an automated suturing device. Second-look laparoscopy was performed at 5 weeks. A smooth fibrous adhesion formed between the spleen, the perirenal fascia, and the nephrosplenic ligament in 3 of the 4 horses in which the nephrosplenic space was closed using the automated suturing device. In 1 horse, closure of the nephrosplenic space was not possible due to constant breakage of the endoscopic needle. Intra-operative complications encountered with the automated suturing device were tearing of the perirenal fascia, nephrosplenic ligament, and dorsal splenic capsule along with breakage of the needle. The automated suturing device used in this study for laparoscopic closure of the nephrosplenic space resulted in longer surgery times, suffered instrument failures and delivered inadequate suture.

Étude pilote pour évaluer la fermeture par laparoscopie de l'espace néphrosplénique à l'aide d'un appareil de suture endoscopique chez des chevaux debout. Cette étude a évalué l'utilisation d'un appareil articulé et automatisé de suture pour la fermeture laparascopique de l'espace néhrosplénique chez les chevaux debout. La fermeture de l'espace néphrosplénique a été réalisée chez 4 chevaux à l'aide d'un appareil de suture automatisé. Une laparascopie de second regard a été réalisée à 5 semaines. Une adhésion fibreuse lisse s'était formée entre la rate, le fascia périrénal et le ligament néphrosplénique chez 3 des 4 chevaux pour lesquels l'espace néphrosplénique avait été fermé à l'aide de l'appareil de suture automatisé. Chez un cheval, la fermeture de l'espace néphrosplénique n'avait pas été possible en raison de bris constant de l'aiguille endoscopique. Des complications peropératoires avec l'appareil de suture automatisé déchiraient le fascia périrénal, le ligament néphrosplénique et la capsule splénique dorsale et l'aiguille se brisait. L'appareil de suture automatisé utilisé dans cette étude pour la fermeture laparascopique de l'espace néphrosplénique a donné lieu à des temps de chirurgie plus longs, à des défaillances de l'instrument et à des sutures inadéquates.(Traduit par Isabelle Vallières).

Cardiopulmonary effects of dexmedetomidine and ketamine infusions with either propofol infusion or isoflurane for anesthesia in horses.

OBJECTIVE: To examine the cardiopulmonary effects of two anesthetic protocols for dorsally recumbent horses undergoing carpal arthroscopy. STUDY DESIGN: Prospective, randomized, crossover study. ANIMALS: Six horses weighing 488.3 ± 29.1 kg. METHODS: Horses were sedated with intravenous (IV) xylazine and pulmonary artery balloon and right atrial catheters inserted. More xylazine was administered prior to anesthetic induction with ketamine and propofol IV. Anesthesia was maintained for 60 minutes (or until surgery was complete) using either propofol IV infusion or isoflurane to effect. All horses were administered dexmedetomidine and ketamine infusions IV, and IV butorphanol. The endotracheal tube was attached to a large animal circle system and the lungs were ventilated with oxygen to maintain end-tidal CO2 40 ± 5 mmHg. Measurements of cardiac output, heart rate, pulmonary arterial and right atrial pressures, and body temperature were made under xylazine sedation. These, arterial and venous blood gas analyses were repeated 10, 30 and 60 minutes after induction. Systemic arterial blood pressures, expired and inspired gas concentrations were measured at 10, 20, 30, 40, 50 and 60 minutes after induction. Horses were recovered from anesthesia with IV romifidine. Times to extubation, sternal recumbency and standing were recorded. Data were analyzed using one and two-way anovas for repeated measures and paired t-tests. Significance was taken at p ≤ 0.05. RESULTS: Pulmonary arterial and right atrial pressures, and body temperature decreased from pre-induction values in both groups. PaO2 and arterial pH were lower in propofol-anesthetized horses compared to isoflurane-anesthetized horses. The lowest PaO2 values (70-80 mmHg) occurred 10 minutes after induction in two propofol-anesthetized horses. Cardiac output decreased in isoflurane-anesthetized horses 10 minutes after induction. End-tidal isoflurane concentration ranged 0.5%-1.3%. CONCLUSION AND CLINICAL RELEVANCE: Both anesthetic protocols were suitable for arthroscopy. Administration of oxygen and ability to ventilate lungs is necessary for propofol-based anesthesia.

The immune response to anesthesia: part 1.

OBJECTIVE: To review the immune response to anesthesia including mechanical ventilation, inhaled anesthetic gases, and injectable anesthetics and sedatives. STUDY DESIGN: Review. METHODS AND DATABASES: Multiple literature searches were performed using PubMed and Google Scholar from spring 2012 through fall 2013. Relevant anesthetic and immune terms were used to search databases without year published or species constraints. The online database for Veterinary Anaesthesia and Analgesia and the Journal of Veterinary Emergency and Critical Care were searched by issue starting in 2000 for relevant articles. CONCLUSION: Recent research data indicate that commonly used volatile anesthetic agents, such as isoflurane and sevoflurane, may have a protective effect on vital organs. With the lung as the target organ, protection using an appropriate anesthetic protocol may be possible during direct pulmonary insults, including mechanical ventilation, and during systemic disease processes, such as endotoxemia, generalized sepsis, and ischemia-reperfusion injury.