Blood Gas Variables Research Articles

The effect of intravenous magnesium sulphate infusion on total intravenous anesthesia with propofol in adult dogs: A randomized, blinded trial

ObjectiveTo evaluate cardiopulmonary, arterial blood gas and propofol-sparing effects of magnesium sulfate (MgSO4) constant rate infusion (CRI) in mechanically ventilated dogs maintained under total intravenous anesthesia with propofol. Study designBlinded, randomized, clinical trial. AnimalsA total of 24 healthy adult dogs. MethodsDogs were premedicated with intramuscular acepromazine (0.05 mg kg–1) and morphine (0.5 mg kg–1), followed by an intravenous (IV) bolus of saline or MgSO4 (50 mg kg–1 over 15 minutes) and propofol (given to effect to induce anesthesia). Anesthesia was maintained with an IV propofol infusion (beginning at 0.3 mg kg–1 minute–1, adjusted as necessary). Concurrently, one of three IV infusions were administered: GS (0.9% NaCl), GM30 (MgSO4, 30 mg kg–1 hour–1) or GM80 (MgSO4, 80 mg kg–1 hour–1). Propofol induction and maintenance doses were recorded. The following variables were recorded at baseline (T0), after bolus treatment (T1), after beginning mechanical ventilation (T5) and every 15 minutes until the end of the procedure (T15–T120): mean arterial pressure, heart rate, peripheral oxygen saturation, end-tidal partial pressure of CO2, temperature, blood gas variables, indirect calorimetry and extubation time. Values of p < 0.05 were considered significant. ResultsPropofol induction bolus dose was lower in GM30 (31.2%, p = 0.04) and GM80 (38.9%, p = 0.003) than in GS. The maintenance propofol infusion rate in GM80 was 16.9% lower (p = 0.03), resulting in fewer propofol CRI rescues during the perioperative period. GM30 and GM80 exhibited faster extubation times than GS (46.2%, p = 0.002 and 48.9%, p = 0.001, respectively). Conclusions and clinical relevanceInfusion of a 50 mg kg–1 bolus, followed by CRI of MgSO4 (30 and 80 mg kg–1 hour–1), reduces the propofol induction and maintenance (CRI) requirement, maintaining cardiorespiratory stability and reducing the time required to extubation.

Cerebral hemodynamics and optic nerve sheath diameter acquired via neurosonology in critical patients with severe coronavirus disease: experience of a national referral hospital in Peru.

We aimed to describe the neurosonological findings related to cerebral hemodynamics acquired using transcranial Doppler and to determine the frequency of elevated ICP by optic nerve sheath diameter (ONSD) measurement in patients with severe coronavirus disease (COVID-19) hospitalized in the intensive care unit of a national referral hospital in Peru. We included a retrospective cohort of adult patients hospitalized with severe COVID-19 and acute respiratory failure within the first 7 days of mechanical ventilation under deep sedoanalgesia, with or without neuromuscular blockade who underwent ocular ultrasound and transcranial Doppler. We determine the frequency of elevated ICP by measuring the diameter of the optic nerve sheath, choosing as best cut-off value a diameter equal to or >5.8 mm. We also determine the frequency of sonographic patterns obtained by transcranial Doppler. Through insonation of the middle cerebral artery. Likewise, we evaluated the associations of clinical, mechanical ventilator, and arterial blood gas variables with ONSD ≥5.8 mm and pulsatility index (PI) ≥1.1. We also evaluated the associations of hemodynamic findings and ONSD with mortality the effect size was estimated using Poisson regression models with robust variance. This study included 142 patients. The mean age was 51.39 ± 13.3 years, and 78.9% of patients were male. Vasopressors were used in 45.1% of patients, and mean arterial pressure was 81.87 ± 10.64 mmHg. The mean partial pressure of carbon dioxide (PaCO2) was elevated (54.08 ± 16.01 mmHg). Elevated intracranial pressure was seen in 83.1% of patients, as estimated based on ONSD ≥5.8 mm. A mortality rate of 16.2% was reported. In the multivariate analysis, age was associated with elevated ONSD (risk ratio [RR] = 1.07). PaCO2 was a protective factor (RR = 0.64) in the cases of PI ≥ 1.1. In the mortality analysis, the mean velocity was a risk factor for mortality (RR = 1.15). A high rate of intracranial hypertension was reported, with ONSD measurement being the most reliable method for estimation. The increase in ICP measured by ONSD in patients with severe COVID-19 on mechanical ventilation is not associated to hypercapnia or elevated intrathoracic pressures derived from protective mechanical ventilation.

Importance of Renal Graft Reperfusion Thermoregulation in Living Donor Kidney Transplant Patients: Gasometrical and Hemodynamical Study

INTRODUCTION: Hypothermia, defined as a decrease in core body temperature below 36°C, has a notable influence on hemodynamic variables during anesthesia, which is of great interest in perioperative medicine. Temperature regulation is crucial in anesthetic management because hypothermia can significantly impact the patient's cardiovascular functioning. Accidental (uncontrolled) hypothermia during anesthetic and surgical procedures carries considerable risks such as: Increases the incidence of surgical site infections, prolongs the effects of drugs administered during anesthesia, and disrupts normal coagulation, potentially increasing the risk of bleeding. For these reasons, body temperature regulation is a critical aspect to monitor and control during anesthesia. MATERIAL AND METHODS: A descriptive, observational, single-center, and retrospective study was carried out in patients undergoing a related living donor kidney transplant between June 2022-2023 at the Juarez Hospital in Mexico. All data were collected from the demographic sheets, laboratories and trans anesthetic sheets of the patient's file. The data was integrated into an Excel database and statistical processing was performed in SPSS or STATSm software. The statistical analysis was tested for normality according to Kolmogorov-Smirnov with Lilliefors correction, where it was found that the population has a normal or non-normal distribution. The Mann-Whitney U test was performed to compare the difference of the means between the two groups. A correlation was made with Kendall´s Tau coefficient; All statistical analyzes were performed with a value of p&lt;0.05, considering these significantly. RESULTS: Of the 65 transplanted patients between Jun 2023 and June 2024 only 28 have appropriate inclusion criteria. Of the remaining 28, 16 were female (57.14%) and 12 were male (42.8%) with an average age of recipients of 30.2430.46 ±11.45 years with a weight of 58.23 ±10.47 kg, height 154.20 ±15.32 cm. Gasometrical and Hemodynamic Values upon Reperfusion with a Forced Air Turbine. The gasometrical variables before reperfusion were: Venous pH 7.41±0.05 (p=0.046); Arterial pH 7.40±0.04 (p=0.015); Venous Oxygen Saturation 68.2±9.74% (p = 0.039). Hemodynamic variables before reperfusion were: IC 3.67±1.77 lt/min/m2 (p=0.001); Stroke Volume 79.5±39.6 ml/beat (p=0.022), Oxygen Extraction 25.1±9.95% (p=0.001) and Myocardial Efficiency 0.28±0.06 (p=0.024); The gasometrical variables after reperfusion were: Venous pH 7.40±0.03; Arterial pH 7.380±0.04; Venous Oxygen Saturation 60.03±4.37%; The hemodynamic variables after reperfusion were: IC 2.88±0.48 liter/min/m2; Stroke Volume 65.4±16.01 ml/beat; Oxygen Extraction Rate 36.9±4.31% (p = 0.039) and Myocardial Efficiency 0.32±0.06 Gasometrical and Hemodynamic Values upon Reperfusion without Forced Air Turbine. The gasometrical variables before reperfusion were: Venous pH 7.32±0.04 (p=0.012); Arterial pH 7.30±0.04 (p=0.019); Venous Oxygen Saturation 64.7±8.27% (p = 0.026). Hemodynamic variables before reperfusion were Cardiac Index 3.28±1.66 lt/min/m2 (p=0.006); Stroke Volume 72.39±45.44 ml/beat (p=0.029); Oxygen Extraction 29.11±9.65% (p=0.001) and Myocardial Efficiency 0.268±0.08 (p=0.022). The gasometrical variables after reperfusion were: Venous pH 7.33±0.04; Arterial pH 7.320±0.05; Venous Oxygen Saturation 58.593±5.41%. The hemodynamic variables after reperfusion were: Cardiac Index 2.75±0.69 liter/min/m2, Stroke Volume 59.05±18.81 ml/beat, Oxygen Extraction Rate 38.47±6.17% and Myocardial Efficiency 0.31±0.05. CONCLUSIONS: Understanding the behavior of blood gas and hemodynamic variables upon reperfusion in transplant patients is essential for adequate kidney graft survival. In these patients, the use of a hot forced air turbine improves the conditions under which said reperfusion is performed, impacting not only at the blood gas level (venous pH, arterial pH and venous oxygen saturation) but also at the hemodynamic level (cardiac index, stroke volume, myocardial efficiency The limitations of the study are heterogeneity of the etiologies of CKD, sample size, and volume status prior to the procedure. To date the published works are consistent with the literature.

Nicardipine constant rate infusion alleviates the cardiovascular effects of dexmedetomidine infusions without affecting the minimal alveolar concentration in sevoflurane-anesthetized dogs

Two randomized crossover trials evaluated the effects of nicardipine constant rate infusion (CRI) on 1) the anesthetic potency of sevoflurane and 2) the ability to attenuate dexmedetomidine-induced cardiovascular depression in anesthetized dogs. First, six healthy Beagle dogs weighing 11.7 ± 0.9 kg were allocated to one of three treatments that administered a CRI of carrier (saline) or dexmedetomidine 0.5 or 3.0 μg/kg/h following a loading dose. The minimum alveolar concentration (MAC) of sevoflurane was determined utilizing electric stimuli before and after the loading dose of nicardipine (20 μg/kg intravenously for 10 min), followed by CRI at 40 μg/kg/h with 60 min of equilibration. Subsequently, cardiovascular and blood gas variables were evaluated in another trial under sevoflurane anesthesia at the individual 1.5 MAC. After baseline measurements, the dogs were assigned to two treatments (dexmedetomidine CRI at 0.5 or 3.0 μg/kg/h following a loading dose) with sevoflurane doses adjusted to 1.5 times of MAC equivalent, and the measurements were repeated every 15 min for 120 min. After 60 min, nicardipine CRI at 40 μg/kg/h with a loading dose was added to the dexmedetomidine CRI. Dexmedetomidine infusions significantly decreased the sevoflurane MAC but nicardipine did not significantly alter the MAC either with or without dexmedetomidine CRI in dogs. Dexmedetomidine dose-dependently decreased the cardiac index and increased the systemic vascular resistance index; these effects were fully counteracted by concomitant nicardipine CRI. Nicardipine CRI can be useful for controlling the cardiovascular depression elicited by dexmedetomidine in anesthetized dogs without affecting the anesthetic potency of sevoflurane.

Physiological and skeletal muscle responses to high-intensity interval exercise in Thoroughbred horses.

The purpose of this study was to determine whether acute high-intensity interval exercise or sprint interval exercise induces greater physiological and skeletal muscle responses compared to moderate-intensity continuous exercise in horses. In a randomized crossover design, eight trained Thoroughbred horses performed three treadmill exercise protocols consisting of moderate-intensity continuous exercise (6 min at 70% VO2max; MICT), high-intensity interval exercise (6 × 30 s at 100% VO2max; HIIT), and sprint interval exercise (6 × 15 s at 120% VO2max; SIT). Arterial blood samples were collected to measure blood gas variables and plasma lactate concentration. Biopsy samples were obtained from the gluteus medius muscle before, immediately after, 4 h, and 24 h after exercise for biochemical analysis, western blotting and real-time RT-PCR. Effects of time and exercise protocol were analyzed using mixed models (p < 0.05). Heart rate and plasma lactate concentration at the end of exercise were higher in HIIT and SIT than those in MICT (heart rate, HIIT vs. MICT, p = 0.0005; SIT vs. MICT, p = 0.0015; lactate, HIIT vs. MICT, p = 0.0014; SIT vs. MICT, p = 0.0003). Arterial O2 saturation and arterial pH in HIIT and SIT were lower compared with MICT (SaO2, HIIT vs. MICT, p = 0.0035; SIT vs. MICT, p = 0.0265; pH, HIIT vs. MICT, p = 0.0011; SIT vs. MICT, p = 0.0023). Muscle glycogen content decreased significantly in HIIT (p = 0.0004) and SIT (p = 0.0016) immediately after exercise, but not in MICT (p = 0.19). Phosphorylation of AMP-activated protein kinase (AMPK) in HIIT showed a significant increase immediately after exercise (p = 0.014), but the increase was not significant in MICT (p = 0.13) and SIT (p = 0.39). At 4 h after exercise, peroxisome proliferator-activated receptor γ co-activator-1α mRNA increased in HIIT (p = 0.0027) and SIT (p = 0.0019) and vascular endothelial growth factor mRNA increased in SIT (p = 0.0002). Despite an equal run distance, HIIT and SIT cause more severe arterial hypoxemia and lactic acidosis compared with MICT. In addition, HIIT activates the AMPK signaling cascade, and HIIT and SIT elevate mitochondrial biogenesis and angiogenesis, whereas MICT did not induce any significant changes to these signaling pathways.

Establishment and validation of intravenous anesthesia with dexmedetomidine for pigs under assisted spontaneous breathing: A preclinical model of intensive care conditions.

Large animal models are frequently used to investigate new medical approaches. In most cases, animals are kept under general anesthesia and mandatory mechanical ventilation during the experiments. However, in some situations assisted spontaneous breathing is essential, e.g. when simulating conditions in a modern intensive care unit. Therefore, we established an anesthesia regime with dexmedetomidine and midazolam/ketamine in porcine models of assisted spontaneous breathing. The total intravenous anesthesia was used in lung healthy pigs, in pigs with oleic acid induced acute respiratory distress syndrome and in pigs with methacholine induced bronchopulmonary obstruction. We were able to maintain stable conditions of assisted spontaneous breathing without impairment of hemodynamic, respiratory or blood gas variables in lung healthy pigs and pigs with induced acute respiratory distress syndrome for a period of five hours and in pigs with induced bronchopulmonary obstruction for three hours. Total intravenous anesthesia containing dexmedetomidine enables stable conditions of assisted spontaneous breathing in healthy pigs, in pigs with induced acute respiratory distress syndrome and in pigs induced bronchopulmonary obstruction as models of intensive care unit conditions.

Changes in Respiratory Mechanics With Trunk Inclination Differs Between Patients With ARDS With and Without Obesity

Studies investigating the effect of trunk inclination on respiratory mechanics in mechanically ventilated patients with ARDS have reported postural differences in partition respiratory mechanics. Compared with more upright positions, the supine-flat position provided lower lung and chest wall elastance, allowing reduced driving pressures and end-inspiratory transpulmonary pressure. However, the effect of trunk inclination on respiratory mechanics in patients with obesity and ARDS is uncertain. Does the effect of change in posture on partition respiratory mechanics differ between patients with ARDS with and without obesity? In this single-center study, patients with ARDS with and without obesity were randomized into two 15-minute steps in which trunk inclination was changed from semi-recumbent (40° head up) to supine-flat (0°), or vice versa. At the end of each step partition respiratory mechanics, airway opening pressure and arterial blood gases were measured. Paired t test was used to examine respiratory mechanics and blood gas variables in each group. Forty consecutive patients were enrolled. Twenty were obese (BMI, 38.4 [34.5-42.3]), and 20 were non-obese (BMI, 26.6 [25.2-28.5]). In the patients with obesity, lung and chest wall elastance, driving pressure, inspiratory transpulmonary pressure, Paco2, and ventilatory ratio were lower supine than semi-recumbent (P< .001). Airways resistance was greater supine (P= .006). In the patients without obesity, only chest wall elastance was lower in supine vssemi-recumbent (P< .001). In mechanically ventilated patients with ARDS and obesity, supine posture provided lower lung and chest wall elastance, and better CO2 clearance, than the semi-recumbent posture. This study was registered with Australian New Zealand Clinical Trials Registry (ACTRN12623000794606).

Effect of maternal hyperoxygenation on neonatal outcomes among women in labour with pathological cardiotocography: an open-label randomized controlled trial

Hyperoxygenation has shown promise in improving suspicious fetal heart patterns in women in labor. However, the effect of hyperoxygenation on neonatal outcomes in women in labor with pathologic fetal heart rate tracing has not been studied. This study aimed to evaluate the effect of fractional inspiration of oxygen of 80% compared with fractional inspiration of oxygen of 40% on neonatal outcomes in women with pathologic fetal heart rate tracing. This randomized, open-label, parallel arm, outcome assessor-blinded clinical trial was conducted in a large tertiary care university hospital. Singleton parturients aged ≥18 years at term gestation in active labor (cervical dilatation of ≥6 cm) with pathologic fetal heart rate tracing were recruited in the study. Pathologic fetal heart rate tracing was defined according to the International Federation of Gynecology and Obstetrics 2015 guidelines. The International Federation of Gynecology and Obstetrics classifies fetal heart rate tracings into 3 categories (normal, suspicious, and pathologic) based on rate, variability, and deceleration. Women in the intervention arm received oxygen at 10 L/min via a nonrebreathing mask, and those in the usual care arm received oxygen at 6 L/min with a simple face mask. Oxygen supplementation was continued until cord clamping. The primary outcome measure was a 5-minute Apgar score. The secondary outcome measures were the proportion of neonatal intensive care unit admission, umbilical cord blood gas variables, level of methyl malondialdehyde in the cord blood, and mode of delivery. Overall, 148 women (74 women in the high fractional inspiration of oxygen arm and 74 in the low fractional inspiration of oxygen arm) with pathologic fetal heart rate tracing were analyzed. The demographic data, obstetrical profiles, and comorbidities were comparable. The median 5-minute Apgar scores were 9 (interquartile range, 8-10) in the hyperoxygenation arm and 9 (interquartile range, 8-10) in the usual care arm (P=.12). Furthermore, the rate of neonatal intensive care unit admission (9.5% vs 12.2%; P=.6) and the requirement of positive pressure ventilation (6.8% vs 8.1%; P=.75) were comparable. Concerning cord blood gas parameters, the hyperoxygenation arm had a significantly higher base deficit in the umbilical vein and lactate level in the umbilical artery. The cesarean delivery rate was significantly lower in women who received hyperoxygenation (4.1% [3/74]) than in women who received normal oxygen supplementation (25.7% [19/74]) (P=.00). In addition, umbilical vein malondialdehyde level in the umbilical vein was lower in the hyperoxygenation group (8.28±4.65 μmol/L) than in the normal oxygen supplementation group (13.44±8.34 μmol/L) (P=.00). Hyperoxygenation did not improve the neonatal Apgar score in women with pathologic fetal heart rate tracing. In addition, neonatal intensive care unit admission rate and blood gas parameters remained comparable. Therefore, the results of this trial suggest that a high fractional inspiration of oxygen supplementation confers no benefit on neonatal outcomes in women with pathologic fetal heart rate tracings and normal oxygen saturation.

Cephalic and saphenous venous blood collected by continuous heating of the paws compared with arterial blood for measurement of blood gas values in well-perfused dogs.

"Arterialization" of the dorsal hand vein is well-established in human medicine, but not in veterinary medicine. To compare cephalic and saphenous venous blood collected by continuously heating the paws to 37°C ("arterialization"), with arterial blood (AB) for measurement of blood gas variables in well-perfused dogs. Eight healthy dogs. Experimental study. Fore and hind paws were continuously heated to 37°C to "arterialize" cephalic and saphenous venous blood. AB and "arterialized" cephalic and saphenous venous blood (ACV and ASV, respectively) were simultaneously collected from lightly anesthetized dogs with induced metabolic and respiratory acid-base disorders. The pH, partial pressures of carbon dioxide (PCO2 ) and oxygen (PO2 ), bicarbonate concentration [HCO3 - ], and base excess (BE) were measured once in each state. Systolic blood pressure was maintained above 100 mm Hg. The AB, ACV, and ASV values were compared. The pH, [HCO3 - ], and BE values had no significant difference and good agreement, the PCO2 values had a strong correlation (correlation coefficient of .91-1.00), and the PO2 values had a significant difference (P < .01) and poor agreement between AB and ACV, and between AB and ASV. The PCO2 values of ASV overestimated those of AB by ~3.0 mm Hg, which was considered within clinically allowable limits, while those of ACV were not within clinically allowable limits. Under experimental conditions, the ASV samples were more identical to the AB samples than the ACV samples for pH, PCO2 , [HCO3 - ], and BE values in well-perfused dogs. The saphenous vein is suitable for "arterialization."

Lung Injury Risk in Traumatic Brain Injury Managed With Optimal Cerebral Perfusion Pressure Guided-Therapy.

Management of traumatic brain injury (TBI) has to counterbalance prevention of secondary brain injury without systemic complications, namely lung injury. The potential risk of developing acute respiratory distress syndrome (ARDS) leads to therapeutic decisions such as fluid balance restriction, high PEEP and other lung protective measures, that may conflict with neurologic outcome. In fact, low cerebral perfusion pressure (CPP) may induce secondary ischemic injury and mortality, but disproportionate high CPP may also increase morbidity and worse lung compliance and hypoxia with the risk of developing ARDS and fatal outcome. The evaluation of cerebral autoregulation at bedside and individualized (optimal CPP) CPPopt-guided therapy, may not only be a relevant measure to protect the brain, but also a safe measure to avoid systemic complications. We aimed to study the safety of CPPopt-guided-therapy and the risk of secondary lung injury association with bad outcome. Single-center retrospective analysis of 92 severe TBI patients admitted to the Neurocritical Care Unit managed with CPPopt-guided-therapy by PRx (pressure reactivity index). During the first 10 days, we collected data from blood gas, ventilation and brain variables. Evolution along time was analyzed using linear mixed-effects regression models. 86% were male with mean age 53±21 years. 49% presented multiple trauma and 21% thoracic trauma. At hospital admission, median GCS was 7 and after 3-months GOS was 3. Monitoring data was CPP 86±7mmHg, CPP-CPPopt -2.8±10.2mmHg and PRx 0.03±0.19. The average PFratio (PaO2/FiO2) was 305±88 and driving pressure 15.9±3.5cmH2O. PFratio exhibited a significant quadratic dependence across time and PRx and driving pressure presented significant negative association with PFRatio. CPP and CPPopt did not present significant effect on PFratio (p=0.533; p=0.556). A significant positive association between outcome and the difference CPP-CPPopt was found. Management of TBI using CPPopt-guided-therapy was associated with better outcome and seems to be safe regarding the development of secondary lung injury.

Acid-base imbalances and the association of blood-gas variables, electrolytes, and biochemical analytes with outcome in hospitalized calves undergoing abdominal surgery.

Surgical abdominal emergencies in calves are associated with a guarded prognosis and have the potential for complex metabolic derangements including acid-base imbalances. To perform a comprehensive analysis of acid-base status and to assess the prognostic relevance of preoperative clinicopathologic variables in calves undergoing abdominal surgery. Hospital-based study samples of 535 (dataset 1; DS1) and 83 calves (dataset 2; DS2). Retrospective (DS1) and prospective (DS2) case series. In DS1, acidemia (pH <7.33) was present in 49.9%, whereas alkalemia (pH >7.37) was present in 30.7% of calves. Plasma L-lactate, chloride, and serum inorganic phosphorus concentration accounted for 51.9%, 11.6% and 9.4% of the variation of venous blood pH, respectively. Classification tree analysis indicated that a negative outcome (death or euthanasia during hospitalization) was associated with venous pO2 ≤33.6 mm Hg, anion gap >18.3 and >22.9mEq/L, serum albumin concentration ≤36.5 and ≤29.4g/L, serum urea concentration >4.4 mmol/L, and plasma ionized calcium concentration ≤1.26 mmol/L. The area under the receiver operating characteristic curve of this model was 0.85 (95% CI: 0.82-0.89, P < .001) and the resulting sensitivity and specificity for the prediction of nonsurvival at the optimal probability cut-point of 0.5 was 89.8% and 65.7%, respectively. In DS2 the model had a similar sensitivity and specificity of 90.5% and 70%, respectively. Clinicopathologic imbalances and associated changes of acid-base status are common in calves with surgical abdominal emergencies and have clinical utility for the prediction of a negative postoperative outcome.

Effects of three immobilizing drug combinations on ventilation, gas exchange and metabolism in free-living African lions (Panthera leo).

Free-living lions (12 per group) were immobilized with tiletamine-zolazepam-medetomidine (TZM), ketamine-medetomidine (KM), or ketamine-butorphanol-medetomidine (KBM). During immobilization, respiratory, blood gas and acid-base variables were monitored for 30minutes. Respiratory rates were within expected ranges and remained constant throughout the immobilizations. Ventilation increased in lions over the immobilization period from 27.2 ± 9.5 to 35.1 ± 25.4L/min (TZM), 26.1 ± 14.3 to 28.4 ± 18.4L/min (KM) and 23.2 ± 10.8 to 26.7 ± 14.2L/min (KBM). Tidal volume increased over the immobilization period from 1800 ± 710 to 2380 ± 1930mL/breath (TZM), 1580 ± 470 to 1640 ± 500mL/breath (KM) and 1600 ± 730 to 1820 ± 880mL/breath (KBM). Carbon dioxide production was initially lower in KBM (0.4 ± 0.2L/min) than in TZM (0.5 ± 0.2L/min) lions but increased over time in all groups. Oxygen consumption was 0.6 ± 0.2L/min (TZM), 0.5 ± 0.2L/min (KM) and 0.5 ± 0.2L/min (KBM) and remained constant throughout the immobilization period. Initially the partial pressure of arterial oxygen was lower in KBM (74.0 ± 7.8mmHg) than in TZM (78.5 ± 4.7mmHg) lions, but increased to within expected range in all groups over time. The partial pressure of arterial carbon dioxide was higher throughout the immobilizations in KBM (34.5 ± 4.2mmHg) than in TZM (32.6 ± 2.2mmHg) and KM (32.6 ± 3.8mmHg) lions. Alveolar-arterial gradients were initially elevated, but decreased over time for all groups, although in KM lions it remained elevated (26.9 ± 10.4mmHg) above the expected normal. Overall, all three drug combinations caused minor respiratory and metabolic side-effects in the immobilized lions. However, initially hypoxaemia occurred as the drug combinations, and possibly the stress induced by the immobilization procedure, hinder alveoli oxygen gas exchange.

Abstract 9704: Role of Arterial Blood Gas Variables in the Prognostication of Patients With Acute Decompensated Heart Failure Admitted to Cardiac Intensive Care Unit

Introduction: Several risk factors and scores have been studied to predict in-hospital mortality [IHM] and rehospitalization [RH] in patients with AHF. Hypothesis: The impact of the initial therapies implemented for AHF on the variables of the acid base gases (ABG) has not been evaluated for prognostication of IHM and RH. Methods: We prospectively evaluated 216 patients admitted in CICU with AHF from 2015 to 2021. Demographic, clinical and ABG variables were analyzed on admission and at 24 hours. Patients were grouped according to whether they presented improvement in respiratory failure, defined as improvement in SaO2, PaO2 and PaCO2 as well as de-escalation of respiratory support devices (NIV or high flow). The aim of the study was to identify whether the improvement in ABG variables, O2 requirement or respiratory support within 24 hours of admission is associated with lower IHM and RH at 60 days. Data was analyzed using bivariate and multivariate analyzes by logistic regression. Results: Mean age was 75 years (44% female), normal EF 62% and reduced 38%. Mean NT-pro-BNP was 9280 ng/dl. RH at 60 days was 25% and IHM was 8.7%. Mean PaO2 on admission was 75 mmHg and at 24 hours 82 mmHg, PaCO2 on admission was 38 mmHg and at 24 hours 40 mmHg, mean SaO2 on admission was 94% and at 24 hours 95%. In bivariate analysis, the highest elevation of the PaCO2 on admission as well as PaCO2 at 24 hours were identified as predictors of IHM (38.42 vs 40.26 mmHg, p = 0.025) and (40.17 vs 46.84 mmHg, p = 0.002) respectively. In multivariate analysis, AKI on CKD (p = 0.03), cardiogenic shock (p = &lt;0.0001), acute myocardial infarction (p = &lt;0.004), emergency PCI (p = &lt;0.001), NIV failure (p = &lt;0.001), NT-pro-BNP (p = &lt;0.01), and elevated PaCO2 at 24 hours (p = 0.02) were identified as independent predictors for IHM. No association between the improvement in ABG variables and RH at 60 days was found. Conclusions: The lack of improvement in PaCO2 at 24 hours of admission to CICU for AHF identifies patients at higher risk for IHM. However, there was no association between the improvement ABG variables at 24 hours and the RH for AHF.

Effects of detomidine or romifidine during maintenance and recovery from isoflurane anaesthesia in horses

ObjectiveTo evaluate the effects of detomidine or romifidine on cardiovascular function, isoflurane requirements and recovery quality in horses undergoing isoflurane anaesthesia. Study designProspective, randomized, blinded, clinical study. AnimalsA total of 63 healthy horses undergoing elective surgery during general anaesthesia. MethodsHorses were randomly allocated to three groups of 21 animals each. In group R, horses were given romifidine intravenously (IV) for premedication (80 μg kg–1), maintenance (40 μg kg–1 hour–1) and before recovery (20 μg kg–1). In group D2.5, horses were given detomidine IV for premedication (15 μg kg–1), maintenance (5 μg kg–1 hour–1) and before recovery (2.5 μg kg–1). In group D5, horses were given the same doses of detomidine IV for premedication and maintenance but 5 μg kg–1 prior to recovery. Premedication was combined with morphine IV (0.1 mg kg–1) in all groups. Cardiovascular and blood gas variables, expired fraction of isoflurane (Fe′Iso), dobutamine or ketamine requirements, recovery times, recovery events scores (from sternal to standing position) and visual analogue scale (VAS) were compared between groups using either anova followed by Tukey, Kruskal-Wallis followed by Bonferroni or chi-square tests, as appropriate (p < 0.05). ResultsNo significant differences were observed between groups for Fe′Iso, dobutamine or ketamine requirements and recovery times. Cardiovascular and blood gas measurements remained within physiological ranges for all groups. Group D5 horses had significantly worse scores for balance and coordination (p = 0.002), overall impression (p = 0.021) and final score (p = 0.008) than group R horses and significantly worse mean scores for VAS than the other groups (p = 0.002). Conclusions and clinical relevanceDetomidine or romifidine constant rate infusion provided similar conditions for maintenance of anaesthesia. Higher doses of detomidine at the end of anaesthesia might decrease the recovery quality.

Reducing the Fermentability of Wheat with a Starch Binding Agent Reduces Some of the Negative Effects of Heat Stress in Sheep.

Simple SummaryHeat stress is one of the major problems affecting the thermotolerance of livestock in Australia and in many parts of the world. Dietary interventions are considered to be one of the effective strategies to beat the heat. Hence, this study evaluated the benefits of reducing the fermentability of wheat grains (BioprotectTM) in the diet of Merino lambs. These results indicated that Bioprotect supplementation had a positive effect on the respiratory rate and heart rate of heat-stressed lambs.The objective of this study was to investigate the effects of reducing the fermentability of grains on thermoregulatory responses in heat stressed (HS) lambs. To achieve this, wheat grain treated with a commercial starch binding agent, Bioprotect, is compared to maize, which has already demonstrated effects in ameliorating heat stress-induced thermoregulation responses and untreated wheat grains. An initial in vitro experiment was conducted to examine cumulative gas production from the fermentation of wheat grain with different dosages of the commercial starch binding agent, Bioprotect. Based on the in vitro results, an in vivo lamb experiment was conducted using 24 Merino lambs (1 year old; 42.6 ± 3.6 kg BW). The lambs were offered one of three dietary treatments: a wheat-based diet (WD), a Bioprotect treated wheat-based diet (BD), and a maize-based diet (MD). Three successive 1-week experimental periods were conducted with lambs from all dietary groups (P1, P2, and P3). During P1, lambs were exposed to a TN environment and fed a 1.7× Maintenance feed intake (MF) level; in P2, lambs were kept in a HS environment and fed a 1.7× MF level; and in P3, animals were kept in a HS environment and fed a 2× MF level. The in vitro experiment revealed a reduction in cumulative gas production (p < 0.05) from the Bioprotect treated wheat compared to untreated wheat samples. In the in vivo component of the study, the replacement of wheat with maize or 2% Bioprotect-treated wheat reduced the respiration rate (p < 0.001) and heart rate (p ≤ 0.01) of lambs during HS. There was a reduction in the concentration of blood gas variables such as a base excess of blood (BE(b)) and extracellular fluid (BE(ecf)), bicarbonate (CHCO3−), the partial pressure of carbon dioxide (pCO2), the total concentration of carbon dioxide (ctCO2), and sodium (Na+) (p ≤ 0.001 for all) during the periods of HS compared to the thermoneutral conditions. Moreover, BD- and MD-fed lambs had a higher blood potassium concentration (K+) than the WD-fed lambs (p = 0.008). The results of the present study suggest that Bioprotect can be a viable feed treatment strategy for treating rapidly fermentable grains such as wheat to alleviate the effects of HS. Further, Bioprotect-treated wheat could be an option to replace maize in concentrate rations in jurisdictions where maize is cost-prohibitive or unavailable.

Physiological Regulation of Growth, Hematology and Blood Gases in Chicken Embryos in Response to Low and High Incubation Humidity.

Variations from a relative humidity (RH) of ∼50–60% can unfavorably alter chicken embryo development, but little is known of whether the embryo can mitigate these effects through physiological regulation. We examined effects of Low RH (25–35%), and High RH (85–93%) compared to Control RH (50–60%) on hatchability, embryonic growth, hematology and blood gases and pH. Mean hatchability was not affected by RH. Yet, Low RH decreased wet body mass of advanced embryos (days 17–19; d17-19), with lowered body water content compared with embryos of Control and High RH. However, dry body mass of developing (d11-19) embryos was not different between the three RH groups. Mean blood osmolality across development was higher in Low RH embryos and lower in High RH embryos compared with Control embryos. Mean blood lactate was higher in both Low and High RH embryos compared to Control embryos. Unexpectedly, hematological respiratory variables (Hct, [RBC], MCV, [Hb]) and blood gas variables (Po2, Pco2, pH, [HCO3 −]) across development were not affected by RH. Mean wet body mass at hatch (d20-22) was larger in High RH embryos compared with Low RH embryos, but mean wet and dry body mass upon euthanasia on d22 was unaffected. The ability of the three populations to physiologically regulate blood respiratory variables and blood acid-base balance was then examined by observing their responses to intrinsic hypoxemia and hypercapnia created by controlled partial egg submersion in water. Hct and [RBC] responses were less disturbed by submersion in High RH embryos compared with both Control and Low RH embryos, which showed major disturbance. Acid-base regulatory responses did not differ between RH groups. We conclude that, while different incubation RHs cause large differences in tissue water content and body mass, most hematological and acid-base regulatory capabilities are regulated near Control values.

Effectiveness of Intermediate Respiratory Care Units as an Alternative to Intensive Care Units during the COVID-19 Pandemic in Catalonia.

Objectives: During the COVID-19 pandemic, the risk of collapse for the health system created great difficulties. We will demonstrate that intermediate respiratory care units (IRCU) provide adequate management of patients with non-invasive respiratory support, which is particularly important for patients with SARS-CoV-2 pneumonia. Methods: A prospective observational study of patients with COVID-19 admitted to the ICU of a tertiary hospital. Sociodemographic data, comorbidities, pharmacological, respiratory support, laboratory and blood gas variables were collected. The overall cost of the unit was subsequently analyzed. Results: 991 patients were admitted, 56 to the IRCU (from a of 81 admitted to the critical care unit). Mean age was 65 years (SD 12.8), Barthel index 75 (SD 8.3), Charlson comorbidity index 3.1 (SD 2.2), HTN 27%, COPD 89% and obesity 24%. A significant relationship (p < 0.05) with higher mortality was noted for the following parameters: fever greater than or equal to 39 °C [OR 5.6; 95% CI (1.2–2.7); p = 0.020], protocolized pharmacological treatment [OR 0.3; 95% CI (0.1–0.9); p = 0.023] and IOI [OR 3.7; 95% CI (1.1–12.3); p = 0.025]. NIMV had less of a negative impact [OR 1.8; 95% CI (0.4–8.4); p = 0.423] than IOI. The total cost of the IRCU amounted to €66,233. The cost per day of stay in the IRCU was €164 per patient. The total cost avoided was €214,865. Conclusions: The pandemic has highlighted the importance of IRCUs in facilitating the management of a high patient volume. The treatment carried out in IRCUs is effective and efficient, reducing both admissions to and stays in the ICU.

Impact of Acute Blood Loss on Clinical, Hematological, Biochemical, and Oxidative Stress Variables in Sheep.

Blood loss in sheep can have different causes and may result in anemia. We aimed to evaluate the clinical, hematological, and biochemical alterations and the oxidative stress generated by acute blood loss. Eighteen healthy sheep underwent phlebotomy to remove 40% of the blood volume and were evaluated clinically and by laboratory tests for clinical, biochemical, and blood gas variables and to assess oxidative stress before induction (T0), 30 min (T30 min), and 6 (T6 h), 12 (T12 h), and 24 h (T24 h) after blood loss. The sheep showed tachycardia from T30 min until T24 h, reduction in the hematocrit, number of erythrocytes, and hemoglobin concentration, with lower values at T24 h and increase in the number of leukocytes from T12 h on. There was a reduction in blood pH and oxygen pressure at T30 min, increased lactate concentration and reduced blood bicarbonate at this time. There was an increase in urea concentration from T6 h until the end of the study, with no change in creatinine levels. The animals did not show changes in the concentration of malonaldehyde, and in the activity of the enzymes superoxide dismutase, glutathione peroxidase, and catalase, but there was a reduction in the concentration of reduced glutathione at T24 h. The acute loss of 40% of blood volume is capable of promoting relevant clinical, hematological, blood gas, and biochemical alterations, and contributed to the appearance of oxidative stress with reduced glutathione concentration, suggesting that this process generated free radicals in sufficient quantity to diminish the action of antioxidants.

Indications and outcome associated with positive-pressure ventilation in dogs and cats: 127 cases.

To determine the indications and outcomes of positive-pressure ventilation (PPV) and identify factors associated with successful weaning. Retrospective study from October 2009 to September 2013. University teaching hospital. One hundred and eleven dogs and 16 cats. Medical records were retrospectively reviewed; signalment, indication for PPV, patient characteristics, blood gas, and ventilator variables during PPV, duration of PPV, and outcome were recorded. Dogs were most commonly ventilated for pneumonia (36/111; 32%) and cats for multiple pulmonary diseases (8/16; 50%). The median duration of PPV for all animals was 25.7h (range, 0.1-957h). Long-term PPV (≥24h) was performed in 53% of cases. No differences were noted in successful weaning rates between cases ventilated for pulmonary etiologies (23/99; 23%) versus nonpulmonary etiologies (9/28; 32%). Overall, 32 of 127 (25%; 30 dogs, 2 cats) animals were successfully weaned from PPV and 28 of 127 (22%; 26 dogs, 2 cats) survived to hospital discharge. Long-term ventilation had a higher likelihood of successful weaning (26/67 [39%] vs 6/60 [10%], P=0.0002) and higher rates of survival to discharge (23/67 [34%] vs 5/60 [8%], P=0.0005) than short-term ventilation. Animals with higher Pao2 /Fio2 and Spo2 /Fio2 and lower APPLE and SOFA scores on day 1 of PPV were more likely to be weaned (P<0.03). The outcome of PPV appears to be most heavily determined by the underlying disease process and no clear improvement in outcome could be demonstrated in this study, despite advances in veterinary critical care and ventilator management strategies since previous studies. Dogs and cats receiving PPV for more than 24h in this study had a higher likelihood of a positive outcome. Several indices of oxygenation and illness severity at the onset of PPV were predictive of outcome and maybe useful when considering prognosis of these cases.

Cardiopulmonary Parameters and Arterial Blood Gases During Etorphine-Medetomidine-Midazolam Immobilization in Free-Ranging Black Rhinoceroses (Diceros bicornis) Undergoing Electro-Ejaculation-A Preliminary Study.

Conservation management interventions for the critically endangered black rhinoceros (Diceros bicornis) require immobilization, which offer opportunities for semen collection and cryopreservation to establish genetic reservoirs. In free-ranging rhinoceroses, a combination of the potent opioid etorphine and the tranquilizer azaperone is routinely used for chemical immobilization but is associated with muscle rigidity and severe cardiopulmonary changes. Additionally, azaperone inhibits semen emission. Seven free-ranging, male, sexually mature black rhinoceroses were immobilized with an alternative protocol consisting of 4.5 mg etorphine, 5 mg medetomidine, 50 mg midazolam and 2,500 IU hyaluronidase delivered remotely by darting from a helicopter. During the immobilization, electro-ejaculation was performed with a portable electro-ejaculator, and a species-specific rectal probe. Animals were observed for muscle tremors. Longitudinal changes in respiratory rate, heart rate and peripheral oxyhemoglobin saturation, measured at 5 min intervals, were assessed using a general mixed model. Non-invasive oscillometric blood pressure and arterial blood gas variables were measured at first handling and before reversal and compared using the Wilcoxon rank sum test. All animals were successfully immobilized, showed no muscle tremors, presented with normal heart rates and lactate concentration (<5 mmol/L), recovered uneventfully, but experienced acidemia, hypoxemia and hypercapnia. Induction time and total time in recumbency were 4.2 ± 0.41 and 38.4 ± 6.9 min, respectively. Electro-stimulation commenced after 11.7 ± 3.98 min and completed after 24.3 ± 6.65 min. Semen-rich fractions were successfully collected from six animals. Our observations indicate that etorphine-medetomidine-midazolam provides a promising immobilization protocol for free-ranging black rhinoceroses, that allows for successful electro-ejaculation.