Arterial Hemoglobin Oxygen Saturation Research Articles

Reliability, clinical performance and trending ability of a pulse oximeter and pulse co-oximeter, in monitoring blood oxygenation, at two measurement sites, in immobilised white rhinoceros (Ceratotherium simum)

BackgroundMonitoring blood oxygenation is essential in immobilised rhinoceros, which are susceptible to opioid-induced hypoxaemia. This study assessed the reliability, clinical performance and trending ability of the Nonin PalmSAT 2500 A pulse oximeter’s and the Masimo Radical-7 pulse co-oximeter’s dual-wavelength technology, with their probes placed at two measurement sites, the inner surface of the third-eyelid and the scarified ear pinna of immobilised white rhinoceroses. Eight white rhinoceros were immobilised with etorphine-based drug combinations and given butorphanol after 12 min, and oxygen after 40 min, of recumbency. The Nonin and Masimo devices, with dual-wavelength probes attached to the third-eyelid and ear recorded arterial peripheral oxygen-haemoglobin saturation (SpO2) at pre-determined time points, concurrently with measurements of arterial oxygen-haemoglobin saturation (SaO2), from drawn blood samples, by a benchtop AVOXimeter 4000 co-oximeter (reference method). Reliability of the Nonin and Masimo devices was evaluated using the Bland-Altman and the area root mean squares (ARMS) methods. Clinical performance of the devices was evaluated for their ability to accurately detect clinical hypoxemia using receiver operating characteristic (ROC) curves and measures of sensitivity, specificity, and positive and negative predictive values. Trending ability of the devices was assessed by calculating concordance rates from four-quadrant plots.ResultsOnly the Nonin device with transflectance probe attached to the third-eyelid provided reliable SpO2 measurements across the 70 to 100% saturation range (bias − 1%, precision 4%, ARMS 4%). Nonin and Masimo devices with transflectance probes attached to the third-eyelid both had high clinical performance at detecting clinical hypoxaemia [area under the ROC curves (AUC): 0.93 and 0.90, respectively]. However, the Nonin and Masimo devices with transmission probes attached to the ear were unreliable and provided only moderate clinical performance. Both Nonin and Masimo devices, at both measurement sites, had concordance rates lower than the recommended threshold of ≥ 90%, indicating poor trending ability.ConclusionsThe overall assessment of reliability, clinical performance and trending ability indicate that the Nonin device with transflectance probe attached to the third-eyelid is best suited for monitoring of blood oxygenation in immobilised rhinoceros. The immobilisation procedure may have affected cardiovascular function to an extent that it limited the devices’ performance.

Self-calibrated pulse oximetry algorithm based on photon pathlength change and the application in human freedivers.

Pulse oximetry estimates the arterial oxygen saturation of hemoglobin () based on relative changes in light intensity at the cardiac frequency. Commercial pulse oximeters require empirical calibration on healthy volunteers, resulting in limited accuracy at low oxygen levels. An accurate, self-calibrated method for estimating is needed to improve patient monitoring and diagnosis. Given the challenges of calibration at low levels, we pursued the creation of a self-calibrated algorithm that can effectively estimate across its full range. Our primary objective was to design and validate our calibration-free method using data collected from human subjects. We developed an algorithm based on diffuse optical spectroscopy measurements of cardiac pulses and the modified Beer-Lambert law (mBLL). Recognizing that the photon mean pathlength () varies with related absorption changes, our algorithm aligns/fits the normalized (across wavelengths) obtained from optical measurements with its analytical representation. We tested the algorithm with human freedivers performing breath-hold dives. A continuous-wave near-infrared spectroscopy probe was attached to their foreheads, and an arterial cannula was inserted in the radial artery to collect arterial blood samples at different stages of the dive. These samples provided ground-truth via a blood gas analyzer, enabling us to evaluate the accuracy of estimation derived from the NIRS measurement using our self-calibrated algorithm. The self-calibrated algorithm significantly outperformed the conventional method (mBLL with a constant ratio) for estimation through the diving period. Analyzing 23 ground-truth data points ranging from 41% to 100%, the average absolute difference between the estimated and the ground truth is for our algorithm, significantly lower than the observed with the conventional approach. By factoring in the variations in the spectral shape of relative to , our self-calibrated algorithm enables accurate estimation, even in subjects with low levels.

Hyperoxic ventilatory response in infants is related to nocturnal hypoxaemia

BackgroundThe carotid bodies primarily serve as oxaemia sensors that affect tidal breathing. Their function has not yet been studied in infants with nocturnal hypoxaemia. This cross-sectional study aimed to characterise the hyperoxic ventilatory response (HVR) in infants and its relationship to nocturnal hypoxaemia.MethodsThe HVR was analysed in term infants aged <24 months with childhood interstitial lung disease (chILD), those with severe recurrent wheezing (wheeze), and nonrespiratory controls. The HVR timing was characterised using hyperoxia response time (HRT1), and HVR magnitude was characterised by the relative change in minute volume between normoxia and 30-s hyperoxia (VE_dH30). Time spent with an arterial haemoglobin oxygen saturation (SpO2) <90% during overnight monitoring (t90) was estimated.ResultsHVR data were available for 23 infants with chILD, 24 wheeze and 14 control infants. A significant decrease in minute volume under 30 s of hyperoxia was observed in all patients. HRT1 was shorter in chILD (5.6±1.2 s) and wheeze (5.9±1.5 s) groups than in the controls (12.6±5.5 s) (ANOVA p<0.001).VE_dH30 was increased in the chILD group (24.3±8.0%) compared with that in the controls (14.7±9.2%) (p=0.003).t90was abnormal in the wheeze (8.0±5.0%) and chILD (32.7±25.8%) groups and higher in the chILD group than in the controls (p<0.001). HRT1 negatively correlated witht90in all groups.ConclusionSignificant differences in HVR timing and magnitude were noted in the chILD, wheeze and control groups. A relationship between nocturnal hypoxaemia and HRT1 was proposed. HVR characterisation may help identify patients with abnormal nocturnalSpO2.

Arterial Oxygen Saturation: A Vital Sign?

The physical examination is a key part of a continuum that extends from the history of the present illness to the therapeutic outcome. An understanding of the pathophysiological mechanism behind a physical sign is essential for arriving at the correct diagnosis. Early detection of deteriorating physical/vital signs and their appropriate interpretation is thus the key to achieve correct and timely management. By definition, vital signs are "the signs of life that may be monitored or measured, namely pulse rate, respiratory rate, body temperature, and blood pressure." Vital signs are the simplest, cheapest and probably the most inexpensive information gathered bedside in outpatient or hospitalized patients. The pulse oximeter was introduced in the 1980s. It is an accurate and non-invasive method for the measurement of arterial hemoglobin oxygen saturation (SaO2). Pulse oximetry-based arterial oxygen saturation can be effectively used bedside in in-hospital and ambulatory patients with diagnosed or suspected lung disease. The present pandemic of COVID-19 should be considered as a wake-up call. Articles related to arterial oxygen saturation and its importance as a vital sign in patient care were searched online especially in PubMed. Available studies were studied in full length and data was extracted. Discussion: A. Clinical Utility of Oxygen Saturation Monitoring: There are many studies reporting the clinical applicability and usefulness of pulse oximetry in the early detection of hypoxemic events during intraoperative and postoperative periods. B. Role of clinical expertise accompanied by knowledge of physiology: A diagnostic sign is useful only if it is interpreted accurately and applied appropriately while evaluating a patient. The World Health Organisation also appreciates these facts and published "The WHO Pulse Oximetry Training Manual." Understanding the physiology behind and overcoming limitations of the diagnostic sign by clinical expertise is important. While using pulse oximetry, a clinician needs to keep in mind the sigmoidal nature of the oxygen-Hb dissociation curve. Considering these benefits of SaO2 measurement, there have been several references in the past to consider oxygen saturation as the fifth vital sign. In the present pandemic oxygen saturation i.e., SpO2 (arterial oxygen saturation) measured by pulse oxymeter, has been the single most important warning and prognostic sign be it for households, offices, street vendors, hospitals or governments. Measurement of trends of SaO2 added with respiratory rate will provide clinicians with a holistic overview of respiratory functions and multidimensional conditions associated with hypoxemia.

Reliability of the Enterprise Point-of-Care (EPOC) blood analyzer's calculated arterial oxygen-hemoglobin saturation in immobilized white rhinoceroses (Ceratotherium simum).

Enterprise Point-of-Care (EPOC) blood analysis is used routinely in wildlife veterinary practice to monitor blood oxygenation, but the reliability of the EPOC calculated arterial oxygen-hemoglobin saturation (cSaO2 ) has never been validated in the white rhinoceros (Ceratotherium simum), despite their susceptibility to hypoxemia during chemical immobilization. We aimed to evaluate the reliability of the EPOC cSaO2 by comparing it against arterial oxygen-hemoglobin saturation (SaO2 ) measured by a co-oximeter reference method in immobilized white rhinoceroses. Male white rhinoceroses in two studies (both n = 8) were immobilized by darting with different etorphine-based drug combinations, followed by butorphanol or saline (administered intravenously). Animals in both studies received oxygen via intranasal insufflation after 60 min. Blood samples were drawn, at predetermined time points, from a catheter inserted into the auricular artery and analyzed using the EPOC and a co-oximeter. Bland-Altman (to estimate bias and precision) and area root mean squares (ARMS) plotswereused to determine the reliability of the EPOC cSaO2 compared with simultaneous co-oximeter SaO2 readings. The rhinoceros were acidotic (pH of 7.3 ± 0.1 [mean ± standard deviation]), hypercapnic (PaCO2 of 73.7 ± 10.5 mmHg), and normothermic (body temperature of 37.4 ± 1.8°C). In total, 389 paired cSaO2 -SaO2 measurements were recorded (the cSaO2 ranged between 13.2% and 99.0%, and the SaO2 ranged between 11.8% and 99.9%). The EPOC cSaO2 readings were unreliable (inaccurate, imprecise, and poor ARMS) across the entire saturation range (bias -6%, precision 5%, and ARMS 8%). The EPOC cSaO2 is unreliable and should not be used to monitor blood oxygenation in immobilized white rhinoceroses.

Therapeutic Hypothermia for Refractory Hypoxemia on Venovenous Extracorporeal Membrane Oxygenation: An In Silico Study.

Patients with respiratory failure may remain hypoxemic despite treatment with venovenous extracorporeal membrane oxygenation (VV-ECMO). Therapeutic hypothermia is a potential treatment for such hypoxia as it reduces cardiac output () and oxygen consumption. We modified a previously published mathematical model of gas exchange to investigate the effects of hypothermia during VV-ECMO. Partial pressures were expressed as measured at 37°C (α-stat). The effect of hypothermia on gas exchange was examined in four clinical scenarios of hypoxemia on VV-ECMO, each with different physiological derangements. All scenarios had arterial partial pressure of oxygen (PaO2) ≤ 46 mm Hg and arterial oxygen saturation of hemoglobin (SaO2) ≤ 81%. Three had high with low extracorporeal blood flow to ratio (). The problem in the fourth scenario was recirculation, with normal . Cooling to 33°C increased SaO2 to > 89% and PaO2 to > 50 mm Hg in all scenarios. Mixed venous oxygen saturation of hemoglobin as % () increased to > 70% and mixed venous partial pressure of oxygen in mm Hg () increased to > 34 mm Hg in scenarios with low . In the scenario with high recirculation, and increased, but to < 50% and < 27 mm Hg, respectively. This in silico study predicted cooling to 33°C will improve oxygenation in refractory hypoxemia on VV-ECMO, but the improvement will be less when the problem is recirculation.

Editor's Choice Articles for June.

Editor's Choice Articles for June.

Evaluation of oxygen saturation as an indicator for tracheal intubation in patients with COVID-19: a prospective cohort study

Background. Since the beginning of COVID-19 pandemic, the importance of clinical criteria for tracheal intubation in critically ill patients with respiratory failure became more noteworthy, especially in resource limitations. The objective was to evaluate the importance of hemoglobin oxygen saturation as a criterion for tracheal intubation in patients with COVID-19. Materials and methods. This is a multi-center, prospective, observational cohort study. We included 117 patients with COVID-19 who needed respiratory support between March to June 2021. Patients were intubated by the protocol of each institution participating in the study and the anesthesiologist’s clinical judgement. Signs of respiratory failure, methods of respiratory support and patient outcome were recorded. Results. Among 117 studied cases, 100 patients had hemoglobin oxygen saturation of 60–90 % in whom 58 were intubated. During hospitalization, 56 intubated patients and 14 non-intubated patients died (96.6 % Vs. 33.3 %). Conclusion. Arterial blood hemoglobin oxygen saturation of 60–90 could not be the correct key to unlock the problem of intubation decision in patients with COVID-19. Therefore, hemoglobin oxygen saturation should not be solely regarded as an indication for intubation in COVID-19.

Sedative and cardiopulmonary effects of intranasal butorphanol with midazolam or dexmedetomidine in New Zealand white rabbits.

This study aimed to compare the sedative and cardiopulmonary effects of intranasal (IN) administration of dexmedetomidine-butorphanol (DB) and midazolam-butorphanol (MB) combinations in New Zealand white rabbits. Eight New Zealand white rabbits were sedated by IN administration of a combination of 0.1mg/kg dexmedetomidine and 0.4mg/kg butorphanol (DB treatment) and 2mg/kg midazolam and 0.4mg/kg butorphanol (MB treatment). The electrocardiogram, pulse rate (PR), respiratory frequency (fR ), arterial haemoglobin oxygen saturation (SpO2 ), fraction of expired carbon dioxide (EtCO2 ), rectal temperature (RT), noninvasive mean arterial pressure (MAP), noninvasive systolic arterial pressure (SAP) and diastolic arterial pressure (DAP) were recorded. The onset of sedation, duration of sedation and sedation score (SS) were also noted. There were no significant differences in the EtCO2 , RT, MAP, SAP and DAP measurements between treatments. The PR significantly decreased in DB compared with MB over time (p = 0.001). Compared with baseline, SpO2 decreased over time in both treatments. The SS was significantly elevated over time in DB compared with MB (p = 0.002). No pharmacokinetic information was available for either treatment, so the findings should be interpreted cautiously. IN DB provides more effective sedation than MB, but cardiopulmonary impairment was observed in both treatments.

Reliability of pulse oximetry at four different attachment sites in immobilized white rhinoceros (Ceratotherium simum)

ObjectivesTo determine the reliability of peripheral oxygen haemoglobin saturation (SpO2), measured by a Nonin PalmSAT 2500A pulse oximeter with 2000T transflectance probes at four attachment sites (third eyelid, cheek, rectum and tail), by comparing these measurements to arterial oxygen haemoglobin saturation (SaO2), measured by an AVOXimeter 4000 co-oximeter reference method in immobilized white rhinoceros (Ceratotherium simum). Study designRandomized crossover study. AnimalsA convenience sample of eight wild-caught male white rhinoceros. MethodsWhite rhinoceros were immobilized with etorphine (0.0026 ± 0.0002 mg kg–1, mean ± standard deviation) intramuscularly, after which the pinna was aseptically prepared for arterial blood sample collection, and four pulse oximeters with transflectance probes were fixed securely to their attachment sites (third eyelid, cheek, rectum and tail). At 30 minutes following recumbency resulting from etorphine administration, the animals were given either butorphanol (0.026 ± 0.0001 mg kg–1) or an equivalent volume of saline intravenously. At 60 minutes following recumbency, insufflated oxygen (15 L minute–1 flow rate) was provided intranasally. In total, the SpO2 paired measurements from the third eyelid (n = 80), cheek (n = 67), rectum (n = 59) and tail (n = 76) were compared with near-simultaneous SaO2 measurements using Bland-Altman to assess bias (accuracy), precision, and the area root mean squares (ARMS) method. ResultsCompared with SaO2, SpO2 measurements from the third eyelid were reliable (i.e., accurate and precise) above an SaO2 range of 70% (bias = 1, precision = 3, ARMS = 3). However, SpO2 measurements from the cheek, rectum and tail were unreliable (i.e., inaccurate or imprecise). Conclusions and clinical relevanceA Nonin PalmSAT pulse oximeter with a transflectance probe inserted into the space between the third eyelid and the sclera provided reliable SpO2 measurements when SaO2 was > 70%, in immobilized white rhinoceros.

ДИФФЕРЕНЦИАЛЬНАЯ ДИАГНОСТИКА ХРОНИЧЕСКОЙ СЕРДЕЧНОЙ НЕДОСТАТОЧНОСТИ И ХРОНИЧЕСКОЙ ДЫХАТЕЛЬНОЙ НЕДОСТАТОЧНОСТИ У ПАЦИЕНТОВ С ХРОНИЧЕСКОЙ ОБСТРУКТИВНОЙ БОЛЕЗНЬЮ ЛЕГКИХ

Chronic respiratory failure (CRF) has traditionally been considered to be the main cause of death in patients with chronic obstructive pulmonary disease (COPD). However, modern epidemiological studies have shown that the leading causes of death in patients with COPD are CHD and CHF. Aim: to study the prevalence of CRF and CHF in patients with COPD, to determine the informative value of clinical symptoms in their diagnosis, to work out an algorithm of differential diagnosis of CRF and chronic heart failure (CHF). Methods: subjects – 100 men with COPD. The median age was 67 years. We performed clinical and laboratory examinations. COPD syndrome was diagnosed upon EchoCG and NT-proBNP results. CRF syndrome was diagnosed by the results of exercise testing with simultaneous measurement of arterial blood hemoglobin oxygen saturation. Results: CHF was established in 45.0% of patients, and right ventricular failure was diagnosed in 42.0% of cases. Patients with CHF and decreased left ventricular EF, whose prognosis could be improved by evidence-based treatment developed at the present stage, comprised only 12.0%. We revealed the correlation of CHF syndrome with CRF and with disorders of arterial blood hemoglobin oxygen saturation: CHF NYHA III is associated with CRF IIIB and any disorders of arterial blood hemoglobin oxygen saturation, while CHF NYHA II and NYHA I are respectively associated with CRF IIIA and CRF IIB as well as with a decrease in arterial blood hemoglobin oxygen saturation both on exertion and at rest. The informative value of clinical symptomatology was assessed in COPD patients for the diagnosis of CHF and CRF syndromes: the probability of CHF diagnosis based on clinical symptoms is 79.0% and for CRF – 88.0%. A symptom score scale and an algorithm for the diagnosis of CHF and CRF were developed.

ДИНАМИКА МАРКЕРОВ ФУНКЦИИ ЭНДОТЕЛИЯ, ПРО- И ПРОТИВОВОСПАЛИТЕЛЬНЫХ ЦИТОКИНОВ В ЗАВИСИМОСТИ ОТ ВЫРАЖЕННОСТИ ХРОНИЧЕСКОЙ ДЫХАТЕЛЬНОЙ НЕДОСТАТОЧНОСТИ У ПАЦИЕНТОВ С ХРОНИЧЕСКОЙ ОБСТРУКТИВНОЙ БОЛЕЗНЬЮ ЛЕГКИХ

The publication is devoted to the study of markers of endothelial function, pro- and anti-inflammatory cytokines in patients with chronic obstructive pulmonary disease depending on the severity of chronic respiratory failure and disorders of arterial blood hemoglobin oxygen saturation. The authors established a decrease in the activity of cellular immunity, insufficient activation of humoral immunity, decrease in antioxidant protection and anti-inflammatory activity of the immune system. Signs of the key link in the development of atherosclerosis – endothelial dysfunction – were revealed in patients with COPD. The results of the study suggest that the degrees of chronic respiratory failure are interrelated with the stages of atherosclerotic process development. Disturbances of hemoglobin saturation of arterial blood with oxygen and pronounced degrees of chronic respiratory failure are considered as factors contributing to the stage of atheromatosis, which underlies the formation of unstable atherosclerotic plaque.

Fluid resuscitation strategy and efficacy evaluation in shock stage in severely burned children with different burn areas in different age groups

Fluid resuscitation strategy and efficacy evaluation in shock stage in severely burned children with different burn areas in different age groups

Use of blood colour for assessment of arterial oxygen saturation in immobilized impala (Aepyceros melampus)

ObjectiveTo determine the relationship between arterial blood colour [as defined by the International Commission on Illumination (CIE) L∗a∗b∗ colour space] and haemoglobin oxygen saturation [functional saturation (SaO2) and fractional saturation (FO2Hb)], and if arterial blood colour can be used to predict arterial haemoglobin oxygen saturation. Study designDescriptive study as an adjunct to two prospective randomized crossover studies. AnimalsA group of 10 wild caught adult female impala (Aepyceros melampus) weighing 34.1 ± 5.2 kg (mean ± standard deviation). MethodsImpala were immobilized with potent opioids (0.09 mg kg–1 of etorphine or thiafentanil). A total of 163 arterial blood samples were collected anaerobically into heparinized syringes from arterial cannulae and analysed immediately using spectrocolourimetry and co-oximetry. Data were analysed by modelling the relationship between predicted arterial blood colour CIE L∗a∗b∗ components and SaO2 and FO2Hb. The models were then used to predict values for L∗, a∗ and b∗ to produce a colour palette for the range of SaO2 and FO2Hb used. The modified version of the Farnsworth-Munsell hue test was used to assess the subjective ordering of the resulting colour palette by 20 observers. ResultsThe second-order polynomial (quadratic) model produced the best fit for all three arterial blood colour CIE L∗a∗b∗ components for both SaO2 and FO2Hb. The regression models were used to generate predicted arterial blood colour CIE L∗a∗b∗ components for the midpoint of each decile over a range of SaO2 and FO2Hb percentages (15% to 95%). The resulting colour palettes were correctly ordered by all observers in the SaO2 range of 45–95% saturation. Conclusions and clinical relevanceAn association between arterial blood colour (as defined by CIE L∗a∗b∗ components) and SaO2 and FO2Hb exists, and arterial blood colour can be used to give a clinically useful estimate of arterial haemoglobin oxygen saturation in impala.

Shining new light on sensory brain activation and physiological measurement in seals using wearable optical technology.

Sensory ecology and physiology of free-ranging animals is challenging to study but underpins our understanding of decision-making in the wild. Existing non-invasive human biomedical technology offers tools that could be harnessed to address these challenges. Functional near-infrared spectroscopy (fNIRS), a wearable, non-invasive biomedical imaging technique measures oxy- and deoxyhaemoglobin concentration changes that can be used to detect localized neural activation in the brain. We tested the efficacy of fNIRS to detect cortical activation in grey seals (Halichoerus grypus) and identify regions of the cortex associated with different senses (vision, hearing and touch). The activation of specific cerebral areas in seals was detected by fNIRS in responses to light (vision), sound (hearing) and whisker stimulation (touch). Physiological parameters, including heart and breathing rate, were also extracted from the fNIRS signal, which allowed neural and physiological responses to be monitored simultaneously. This is, to our knowledge, the first time fNIRS has been used to detect cortical activation in a non-domesticated or laboratory animal. Because fNIRS is non-invasive and wearable, this study demonstrates its potential as a tool to quantitatively investigate sensory perception and brain function while simultaneously recording heart rate, tissue and arterial oxygen saturation of haemoglobin, perfusion changes and breathing rate in free-ranging animals. This article is part of the theme issue 'Measuring physiology in free-living animals (Part I)'.

Self-preference music for gagging patient: Effect on physiology and oral health-related quality of life during dental impression

BackgroundGagging condition is among factors contributing to avoidance behavior to seek the dental treatment, and rigorous management is still under investigation. This study aims to explore the effect of listening to the self-preference music in reducing the gagging condition during dental impression procedure towards gagging patient. Physiology and psychological impact to the procedure with and without musical intervention are investigated. Method and materialA group of twenty-five patients that will undergo impression procedure was randomly selected. Self-reported Gagging Problem Assessment (GPA-pa-SF) questionnaires was then administered to determine the severity of gagging. Maxillary impression was taken twice within the same patient in two different time intervals (1st without any intervention and 2nd with musical intervention). During both procedures, the pulse rate/minutes (BPM) and arterial oxygen saturation of haemoglobin (SpO2%) were recorded and psychometric assessment was evaluated through the Oral Health Impact Profile (OHIP-14). ResultMean value of BPM was significantly reduced with music (p < 0.05) while SpO2 was considerably has positive effect although was found no significant. The OHIP 14 demonstrated that functional limitation and psychological disability were the most affected before the intervention. Overall, musical stimuli had a significant effect on stress reduction in both physiological (p < 0.05) and psychological (p < 0.05) outcomes except for social disability and handicap items. ConclusionListening to self-preference music during impression taking had improved physiology and psychology of gagging patients thus, can be attributed to the better dental management.

Ventilation strategies for front of neck airway rescue: an in silico study

BackgroundDuring induction of general anaesthesia a ‘cannot intubate, cannot oxygenate’ (CICO) situation can arise, leading to severe hypoxaemia. Evidence is scarce to guide ventilation strategies for small-bore emergency front of neck airways that ensure effective oxygenation without risking lung damage and cardiovascular depression. MethodsFifty virtual subjects were configured using a high-fidelity computational model of the cardiovascular and pulmonary systems. Each subject breathed 100% oxygen for 3 min and then became apnoeic, with an obstructed upper airway. When arterial haemoglobin oxygen saturation reached 40%, front of neck airway access was simulated with various configurations. We examined the effect of several ventilation strategies on re-oxygenation, pulmonary pressures, cardiovascular function, and oxygen delivery. ResultsRe-oxygenation was achieved in all ventilation strategies. Smaller airway configurations led to dynamic hyperinflation for a wide range of ventilation strategies. This effect was absent in airways with larger internal diameter (≥3 mm). Intrapulmonary pressures increased quickly to supra-physiological values with the smallest airways, resulting in pronounced cardio-circulatory depression (cardiac output <3 L min−1 and mean arterial pressure <60 mm Hg), impeding oxygen delivery (<600 ml min−1). Limiting tidal volume (≤200 ml) and ventilatory frequency (≤8 bpm) for smaller diameter cannulas reduced dynamic hyperinflation and gas trapping, preventing cardiovascular depression. ConclusionsDynamic hyperinflation can be demonstrated for a wide range of front of neck airway cannulae when the upper airway is obstructed. When using small-bore cannulae in a CICO situation, ventilation strategies should be chosen that prevent gas trapping to prevent severe adverse events including cardio-circulatory depression.

Comparison of anesthetic effects of tiletamine–zolazepam–medetomidine or ketamine–medetomidine in captive Amur leopard cats (Prionailurus bengalensis euptailurus)

ObjectiveTo evaluate the effects and utility of tiletamine–zolazepam–medetomidine (TZM) and ketamine–medetomidine (KM) for anesthesia of Amur leopard cats (Prionailurus bengalensis euptailurus). Study designProspective, randomized experimental trial. AnimalsA total of six female (3.70 ± 0.49 kg) and six male (5.03 ± 0.44 kg; mean ± standard deviation) Amur leopard cats aged 2–6 years. MethodsEach animal was administered four protocols separated by ≥3 weeks. Each protocol included medetomidine (0.05 mg kg–1) combined with tiletamine–zolazepam (1 mg kg–1; protocol MTZLO); tiletamine–zolazepam (2 mg kg–1; protocol MTZHI); ketamine (2 mg kg–1; protocol MKLO); or ketamine (4 mg kg–1; MKHI) administered intramuscularly. At time 0 (onset of lateral recumbency) and 30 minutes, heart rate (HR), respiratory rate (fR), rectal temperature, noninvasive mean arterial pressure (MAP) and hemoglobin oxygen saturation (SpO2) were recorded. Times to onset of lateral recumbency, duration of anesthesia and time to standing were recorded. ResultsOverall, animals were anesthetized with all protocols within 10 minutes, anesthesia was maintained ≥57 minutes, and recovery (time from the first head lift to standing) was completed within 5 minutes. During anesthesia with all protocols, HR, fR, rectal temperature, SpO2 and MAP were 99–125 beats minute–1, 33–44 breaths minute–1, 37.6–39.4 °C, 90–95% and 152–177 mmHg, respectively. No adverse event was observed. Conclusions and clinical relevanceTZM and KM at various dosages resulted in rapid onset of anesthesia, duration of >57 minutes and rapid recovery without administration of an antagonist. Accordingly, all these combinations are useful for anesthetizing Amur leopard cats and for performing simple procedures. However, the low doses of the anesthetic agents are recommended because there was no difference in duration of anesthesia between the dose rates studied.

Suspected venous air embolism during thoracic limb amputation in a dog

A six-year-old dog was anaesthetised for the amputation of her left forequarter. Preoperative haematology, biochemistry and physical examination were unremarkable. Twenty minutes into surgery, a sudden decrease in end tidal...

Evaluation of hemodynamic, hematological parameters and the clinical effects of dexmedetomidine-ketamine and xylazine-ketamine anesthesia in rabbits

With this study, it was aimed to assess the effects of experimentally induced dexmedetomidine-ketamine (DK) and xylazineketamine (XK) combinations on clinical parameters and hemodynamic and hematological parameters in rabbits. In the study, 16 male New Zealand breed rabbits were divided into two groups. Group DK (n = 8) was administered dexmedetomidine (25 μg/kg) and ketamine (30 mg/kg) in the same injector, and Group XK (n = 8) was administered xylazine (4 mg/kg) and ketamine (30 mg/kg) in the same injector through the intramuscular (IM) route. Following the injection, the rabbits' reflexes were tested approximately every 30 s. Hemodynamic parameters were determined before the injection (0 min) and 5, 10, 15, 30, 45, 60, 75, 90, 105 and 120 min after the anesthetic combinations were injected. Furthermore, blood gas and electrolyte values were analyzed before, during and after anesthesia. The differences between the groups were not statistically significant in terms of the loss and return times of the righting reflex, ear-pinch reflex and pedal withdrawal reflex (P > 0.05). The mean surgical anesthesia duration was determined as 115 min in the DK group and 116.5 min in the XK group. In both groups, the heart rate (HR), respiratory rate (RR), mean arterial pressure (MAP) and arterial oxygen saturation of hemoglobin (SpO2) decreases. In the statistical analysis, the differences between the groups were statistically significant in terms of HR at the 5th, 10th and 15th min and in terms of SpO2 at the 120th min (P < 0.05). In the DK group, the change in RR based on the pre-injection time (0 min) was found significant (P < 0.05). In the statistical analyses on the arterial blood gases and electrolyte findings, the differences between the DK and XK groups were insignificant in terms of pH, pCO2 and pO2 (P > 0.05) and significant in terms of only glucose (mg/dL) at the 5th min (P < 0.05). Consequently, it was observed that the DK and XK combinations had similar effects in healthy adult rabbits regarding the reflex findings, anesthesia duration and hemodynamic and hematological parameters. It was concluded that, to prevent hypoxemia related to RR decrease in the combination of α2 adrenergic agonists and ketamine, there is a need for oxygen reinforcement starting with the induction of anesthesia, and the DK combination needs to be used carefully in patients with respiratory depression.