Effect of dexmedetomidine on cardiorespiratory regulation in spontaneously breathing adult rats

Purpose We examined the cardiorespiratory effect of dexmedetomidine, an α2- adrenoceptor/imidazoline 1 (I1) receptor agonist, in spontaneously breathing adult rats. Methods Male rats (226−301 g, n = 49) under isoflurane anesthesia had their tail vein cannulated for drug administration and their tail artery cannulated for analysis of mean arterial pressure (MAP), pulse rate (PR), and arterial blood gases (PaO2, PaCO2, pH). After recovery, one set of rats received normal saline for control recording and was then divided into three experimental groups, two receiving dexmedetomidine (5 or 50 μg·kg−1) and one receiving normal saline (n = 7 per group). Another set of rats was divided into four groups receiving dexmedetomidine (50 μg·kg−1) followed 5 min later by 0.5 or 1 mg∙kg−1 atipamezole (selective α2-adrenoceptor antagonist) or efaroxan (α2-adrenoceptor/I1 receptor antagonist) (n = 6 or 8 per group). Recordings were performed 15 min after normal saline or dexmedetomidine administration. Results Compared with normal saline, dexmedetomidine (5 and 50 μg·kg−1) decreased respiratory frequency (fR, p = 0.04 and < 0.01, respectively), PR (both p < 0.01), and PaO2 (p = 0.04 and < 0.01), and increased tidal volume (both p = 0.049). Dexmedetomidine at 5 μg·kg−1 did not significantly change minute ventilation (V′E) (p = 0.87) or MAP (p = 0.24), whereas dexmedetomidine at 50 μg·kg−1 significantly decreased V′E (p = 0.03) and increased MAP (p < 0.01). Only dexmedetomidine at 50 μg·kg−1 increased PaCO2 (p < 0.01). Dexmedetomidine (5 and 50 μg·kg−1) significantly increased blood glucose (p < 0.01), and dexmedetomidine at 50 μg·kg−1 increased hemoglobin (p = 0.04). Supplemental atipamezole or efaroxan administration similarly prevented the 50 μg·kg−1 dexmedetomidine-related cardiorespiratory changes. Principal conclusion These results suggest that dexmedetomidine-related hypoventilation and hypertension are observed simultaneously and occur predominantly through activation of α2-adrenoceptors, but not I1 receptors, in spontaneously breathing adult rats.

Performance of The Decarboxylation Index To Predict CO2 Removal And Mechanical Ventilation Reduction Under VV-ECMO Or High-Flow ECCO2R

Background: Optimal decarboxylation dose under extracorporeal respiratory support to ensure sufficient reduction of mechanical ventilation stress remains unclear and understudied. The aim of this study was to assess the interdependence of blood flow (BF) and gas flow (GF) in predicting CO2 removal and mechanical ventilation reduction (MVR) under extracorporeal respiratory support. Methods: All patients who benefited from veno-venous ECMO (HLS-maquet 7.0, 1.8 m²) and high-flow ECCO2R (HLS-maquet 5.0, 1.3 m²) in our intensive care unit over a period of 18 months were included. CO2 removal was calculated from inlet/outlet blood gases performed in clinical practice during the first 7 days of oxygenator use. The relationship between the BF × GF product and CO2 removal or MVR was studied using linear regression models. Results: Eighteen patients were analysed, corresponding to 24 oxygenators and 261 datasets. CO2 removal was 393 mL/min (IQR, 310–526 mL/min) for 1.8 m2 oxygenators and 179 mL/min (IQR, 165–235 mL/min) for 1.3 m2 oxygenators. The decarboxylation index was associated linearly with CO2 removal (R2 = 0.62 and R2 = 0.77 for the two oxygenators, respectively) and MVR (R2 = 0.72 and R2 = 0.62, respectively). Values in the range 20−30L2/min2 were associated with an MVR ratio between 38% and 58% for 1.8 m2 oxygenators, and between 37% and 55% for 1.3 m2 oxygenators. Conclusion: The decarboxylation index is a simple parameter to predict CO2 removal and MVR under extracorporeal respiratory support. A BF of 2 L2/min2 or more may be necessary to obtain a significant reduction of mechanical convection.Trial Registration: Being a retrospective study, no trial registration was made.

Self-Perceived Skills of Pre Intern Doctors in Sri Lanka

IntroductionThe transition from medical student to intern is a significant and challenging time in a doctor’s training. It can be stressful for the young doctor and there can be varying expectations from employers and supervisors on their capabilities. There is a time gap between graduation and internship for medical graduates in Sri Lanka. Also, there was no proper orientation prior the internship. Thus, the Good Intern Programme was developed as a skills training programme for pre interns who are awaiting internship, and this was conducted in collaboration with Ministry of Health (MOH), Government Medical Officers’ Association (GMOA), Society for Health Research and Innovation (SHRI). This study aimed to explore self-perceived competency of selected skills of pre-interns who were awaiting for internship. Methods Study populationSri Lankan medical Faculties (University of Colombo, Peradeniya, Sri Jayewardenapura, Jaffna, Kelaniya, Ruhuna, Eastern University- Batticaloa, Rajarata University and General Sir John Kotelawala Defence University -KDU), and foreign universities produce approximately 1000 medical graduates per year. In 2020, all pre- interns who joined the Good Intern Programme, Sri Lanka were invited to participate in this questionnaire survey. Statistical analyses were performed using SPSS 23.0 software. Descriptive data were presented as proportions.Results Mean age was 27.6 (+ SD 1.4). Majority of the pre-interns were females (66.5%). Majority of pre-interns perceived that they were able to performs suturing, cannulation, catheterization, setting up an Intravenous (IV) drip, infusion pump setup, blood and blood products transfusion, venipuncture, venipuncture for blood culture, injections-Subcutaneous (SC)/Intramuscular (IM), Glasgow Coma Scale (GCS) monitoring, Cardiopulmonary resuscitation (CPR), arterial puncture for Arterial Blood Gases (ABG), wound dressing, suture removal, bandaging, glucometer use, nebulization, connecting to an ECG (electrocardiogram) monitor competently with or without supervision respectively. Lack of competency perceived on the following skills. Nasogastric tube (NG) insertion, pleural tap, peritoneal tap, removal of an Intercostal tube, lumbar puncture, defibrillation, venous cut down, intubation, CVP (central venous catheter) line insertion, Intercostal (IC) tube insertion were rated by the majority of pre-interns as skills that could be performed competently with supervision or not able to perform the skill but has observed skill. ConclusionAlthough most of the skills were rated by majority of the pre-interns as skills that could be competently performed with or without supervision respectively, there were some skills which needed some improvement. This study suggests that Good Intern Programme in pre-intern period can help to prepare students for the intern role.

Acid–Base Balance, Blood Gases Saturation, and Technical Tactical Skills in Kickboxing Bouts According to K1 Rules

Background: Acid–base balance (ABB) is a major component of homeostasis, which is determined by the efficient functioning of many organs, including the lungs, kidneys, and liver, and the proper water and electrolyte exchange between these components. The efforts made during competitions by combat sports athletes such as kickboxers require a very good anaerobic capacity, which, as research has shown, can be improved by administering sodium bicarbonate. Combat sports are also characterized by an open task structure, which means that cognitive and executive functions must be maintained at an appropriate level during a fight. The aim of our study was to analyze the changes in ABB in capillary blood, measuring levels of H+, pCO2, pO2, HCO3−, BE and total molar CO2 concentration (TCO2), which were recorded 3 and 20 min after a three-round kickboxing bout, and the level of technical and tactical skills presented during the fight. Methods: The study involved 14 kickboxers with the highest skill level (champion level). Statistical comparison of mentioned variables recorded prior to and after a bout was done with the use of Friedman’s ANOVA. Results: 3 min after a bout, H+ and pO2 were higher by 41% and 11.9%, respectively, while pCO2, HCO3−, BE and TO2 were lower by 14.5%, 39.4%, 45.4% and 34.4%, respectively. Furthermore, 20 min after the bout all variables tended to normalization and they did not differ significantly compared to the baseline values. Scores in activeness of the attack significantly correlated (r = 0.64) with pre–post changes in TCO2. Conclusions: The disturbances in ABB and changes in blood oxygen and carbon dioxide saturation observed immediately after a bout indicate that anaerobic metabolism plays a large part in kickboxing fights. Anaerobic training should be included in strength and conditioning programs for kickboxers to prepare the athletes for the physiological requirements of sports combat.

Carbon Dioxide Sensing—Biomedical Applications to Human Subjects

Carbon dioxide (CO2) monitoring in human subjects is of crucial importance in medical practice. Transcutaneous monitors based on the Stow-Severinghaus electrode make a good alternative to the painful and risky arterial “blood gases” sampling. Yet, such monitors are not only expensive, but also bulky and continuously drifting, requiring frequent recalibrations by trained medical staff. Aiming at finding alternatives, the full panel of CO2 measurement techniques is thoroughly reviewed. The physicochemical working principle of each sensing technique is given, as well as some typical merit criteria, advantages, and drawbacks. An overview of the main CO2 monitoring methods and sites routinely used in clinical practice is also provided, revealing their constraints and specificities. The reviewed CO2 sensing techniques are then evaluated in view of the latter clinical constraints and transcutaneous sensing coupled to a dye-based fluorescence CO2 sensing seems to offer the best potential for the development of a future non-invasive clinical CO2 monitor.

Blood Gas Analyses in Hyperbaric and Underwater Environments: A Systematic Review

Background: Pulmonary gas exchange during diving or in a dry hyperbaric environment is affected by increased breathing gas density and possibly water immersion. During free diving there is also the effect of apnea. Few studies have published blood gas data in underwater or hyperbaric environments: this review summarizes the available literature and was used to test the hypothesis that arterial PO2 under hyperbaric conditions can be predicted from blood gas measurement at 1 atmosphere assuming a constant arterial/alveolar PO2 ratio (a:A). Methods: A systematic search was performed on traditional sources including arterial blood gases obtained on humans in hyperbaric or underwater environments. The a:A was calculated at 1 atmosphere absolute (ATA). For each condition, predicted PaO2 at pressure was calculated using the 1 ATA a:A, and the measured PaO2 was plotted against the predicted value with Spearman correlation coefficients. Results: Of 3640 records reviewed, 30 studies were included: 25 were reports describing values obtained in hyperbaric chambers, and the remaining were collected while underwater. Increased inspired O2 at pressure resulted in increased PaO2, although underlying lung disease in patients treated with hyperbaric oxygen attenuated the rise. PaCO2 generally increased only slightly. In breath-hold divers, hyperoxemia generally occurred at maximum depth, with hypoxemia after surfacing. The a:A adequately predicted the PaO2 under various conditions: dry (r=0.993, p< 0.0001); rest vs. exercise (r=0.999, p< 0.0001); and breathing mixtures (r=0.995, p< 0.0001). Conclusion: Pulmonary oxygenation under hyperbaric conditions can be reliably and accurately predicted from 1 ATA a:A measurements.