Validation of an alternative technique for RQ estimation in anesthetized pigs.

BACKGROUND: Respiratory quotient (RQ) is an important variable when assessing metabolic status in intensive care patients. However, analysis of RQ requires cumbersome technical equipment. The aim of the current study was to examine a simplified blood gas-based method of RQ assessment, using Douglas bag measurement of RQ (Douglas-RQ) as reference in a laboratory porcine model under metabolic steady state. In addition, we aimed at establishing reference values for RQ in the same population, thereby generating data to facilitate further research. METHODS: RQ was measured in 11 mechanically ventilated pigs under metabolic steady state using Douglas-RQ and CO-oximetry blood gas analysis of pulmonary artery and systemic carbon dioxide and oxygen content. The CO-oximetry data were used to calculate RQ (blood gas RQ). Paired recordings with both methods were made once in the morning and once in the afternoon and values obtained were analyzed for potential significant differences. RESULTS: The average Douglas-RQ, for all data points over the whole day, was 0.97 (95%CI 0.95-0.99). The corresponding blood gas RQ was 0.95 (95%CI 0.87-1.02). There was no statistically significant difference in RQ values obtained using Douglas-RQ or blood gas RQ for all data over the whole day (P = 0.43). Bias was - 0.02 (95% limits of agreement ± 0.3). Douglas-RQ decreased during the day 1.00 (95%CI 0.97-1.03) vs 0.95 (95%CI 0.92-0.98) P < 0.001, whereas the decrease was not significant for blood gas RQ 1.02 (95%CI 0.89-1.16 vs 0.87 (0.80-0.94) P = 0.11. CONCLUSION: RQ values obtained with blood gas analysis did not differ statistically, compared to gold standard Douglas bag RQ measurement, showing low bias but relatively large limits of agreement, when analyzed for the whole day. This indicates that a simplified blood gas-based method for RQ estimations may be used as an alternative to gold standard expired gas analysis on a group level, even if individual values may differ. In addition, RQ estimated with Douglas bag analysis of exhaled air, was 0.97 in anesthetized non-fasted pigs and decreased during prolonged anesthesia.

Capnodynamic end-expiratory lung volume assessment in anesthetized healthy children.

BACKGROUND: Capnodynamic lung function monitoring generates variables that may be useful for pediatric perioperative ventilation. AIMS: Establish normal values for end-expiratory lung volume CO2 in healthy children undergoing anesthesia and to compare these values to previously published values obtained with alternative end-expiratory lung volume methods. The secondary aim was to investigate the ability of end-expiratory lung volume CO2 to react to positive end-expiratory pressure-induced changes in end-expiratory lung volume. In addition, normal values for associated volumetric capnography lung function variables were examined. METHODS: Fifteen pediatric patients with healthy lungs (median age 8 months, range 1-36 months) undergoing general anesthesia were examined before start of surgery. Tested variables were recorded at baseline positive end-expiratory pressure 3 cmH2 O, 1 and 3 min after positive end-expiratory pressure 10 cmH2 O and 3 min after returning to baseline positive end-expiratory pressure 3 cmH2 O. RESULTS: Baseline end-expiratory lung volume CO2 was 32 mL kg-1 (95% CI 29-34 mL kg-1 ) which increased to 39 mL kg-1 (95% CI 35-43 mL kg-1 , p < .0001) and 37 mL kg-1 (95% CI 34-41 mL kg-1 , p = .0003) 1 and 3 min after positive end-expiratory pressure 10 cmH2 O, respectively. End-expiratory lung volume CO2 returned to baseline, 33 mL kg-1 (95% CI 29-37 mL kg-1 , p = .72) 3 min after re-establishing positive end-expiratory pressure 3 cmH2 O. Airway dead space increased from 1.1 mL kg-1 (95% CI 0.9-1.4 mL kg-1 ) to 1.4 (95% CI 1.1-1.8 mL kg-1 , p = .003) and 1.5 (95% CI 1.1-1.8 mL kg-1 , p < .0001) 1 and 3 min after positive end-expiratory pressure 10 cmH2 O, respectively, and 1.2 mL kg-1 (95% CI 0.9-1.4 mL kg-1 , p = .08) after 3 min of positive end-expiratory pressure 3 cmH2 O. Additional volumetric capnography and lung function variables showed no major changes in response to positive end-expiratory pressure variations. CONCLUSIONS: Capnodynamic noninvasive and continuous end-expiratory lung volume CO2 values assessed during anesthesia in children were in close agreement with previously reported end-expiratory lung volume values generated by alternative methods. Furthermore, positive end-expiratory pressure changes resulted in physiologically expected end-expiratory lung volume CO2 responses in a timely manner, suggesting that it can be used to trend end-expiratory lung volume changes during anesthesia.

Fascial plane blocks in children-Scientifically supported or not?

Since the introduction of Fascial Plane Blocks in 2007 there has been an enormous interest and application of Fascial Plane Blocks, evidenced by substantially more than 1000 PubMed items. Despite this gigantic number of publications, also including randomized controlled trials and meta-analyses in children, there is still no clear-cut insight into how much of the purported effect is in fact due to the blockade of nerve structures and how much is merely adding the well-known analgesic and anti-inflammatory effects of the plasma levels of local anesthetics that are achieved with these techniques. Furthermore, Fascial Plane Blocks appear useful only if compared to conventional multi-modal analgesia (no block or placebo) and Fascial Plane Blocks lack the potency to provide surgical anesthesia on their own and appear only to be of value when used for minor-moderate surgery. Despite the huge literature, there has so far not emerged any clinical situations where Fascial Plane Blocks have definitively been shown to be the block of choice, being decisively more effective than other established regional blocks. Lastly, Fascial Plane Blocks may appear as virtually free of complications, but case reports are emerging that point to a real risk for causing local anesthetic systemic toxicity when using Fascial Plane Blocks. This text aims to synthesize the current knowledge base regarding the Fascial Plane Blocks that are relevant to use in the pediatric context. In summary, there does currently not exist any convincing scientific evidence for the continued support for the use of Fascial Plane Blocks in children, except for the rectus sheath block and possibly also the transmuscular quadratus lumborum block.

Spinal anaesthesia in children: A narrative review.

Spinal anaesthesia is an established and frequently used anaesthetic technique in adults. However, this versatile regional anaesthetic technique is less frequently used in paediatric anaesthesia even though it can be used for minor (e.g. inguinal hernia repair) and major (e.g. cardiac surgery) surgical procedures. The aim of this narrative review was to summarize the current literature with regard to technical aspects, surgical context, choice of drugs, potential complications, as well as the effects of the neuroendocrine surgical stress response and potential long-term effects of anaesthesia during infancy. In summary, spinal anaesthesia represents a valid alternative in the paediatric anaesthesia setting also.

Standardized blood volume changes monitored by capnodynamic hemodynamic variables: An experimental comparative study in pigs.

BACKGROUND: The capnodynamic method, based on Volumetric capnography and differential Fick mathematics, assess cardiac output in mechanically ventilated subjects. Capnodynamic and established hemodynamic monitoring parameters' capability to depict alterations in blood volume were investigated in a model of standardized hemorrhage, followed by crystalloid and blood transfusion. METHODS: Ten anesthetized piglets were subjected to controlled hemorrhage (450 mL), followed by isovolemic crystalloid bolus and blood re-transfusion. Intravascular blood volume, and all hemodynamic variables, were determined twice after each intervention. The investigated hemodynamic variables were: cardiac output and stroke volume for capnodynamics and pulse contour analysis, respectively, pulse pressure and stroke volume variability and mean arterial pressure. One-way ANOVA and Tukey's test for multiple comparisons were used to identify significant changes. Trending was assessed by correlation and concordance. RESULT: Concordance against intravascular volume changes for capnodynamic cardiac output and stroke volume were 96 and 94%, with correlations r = .78 and .68, (p < .0001) with significant changes for 6 and 5 of the 6 measuring points, respectively. Mean arterial pressure and pulse pressure variation had a concordance of 85% and 87%, r = .67 (p < .0001) and r = -.45 (p < .0001), respectively, and both changed significantly for 3 of 6 measuring points. Pulse contour stroke volume variation, stroke volume and cardiac output, showed concordance and correlation of 76%, r = -.18 (p = .11), 63%, r = .28 (p = .01) and 50%, r = .31 (p = .007), respectively and significant change for 1, 1 and 0 of the measuring points, respectively. CONCLUSION: Capnodynamic cardiac output and stroke volume did best depict the changes in intravascular blood volume. Pulse contour parameters did not follow volume changes in a reliable way.

Perioperative water and electrolyte balance and water homeostasis regulation in children with acute surgery.

BACKGROUND: Hospital-acquired hyponatremia remains a feared event in patients receiving hypotonic fluid therapy. Our objectives were to assess post-operative plasma-sodium concentration and to provide a physiological explanation for plasma-sodium levels over time in children with acute appendicitis. METHODS: Thirteen normonatremic (plasma-sodium ≥135 mmol/L) children (8 males), median age 12.3 (IQR 11.5-13.5) years participated in this prospective observational study (ACTRN12621000587808). Urine was collected and analyzed. Blood tests, including renin, aldosterone, arginine-vasopressin, and circulating nitric oxide substrates were determined on admission, at induction of anesthesia, and at the end of surgery. RESULTS: On admission, participants were assumed to be mildly dehydrated and were prescribed 50 mL/kg of Ringer's acetate intravenously followed by half-isotonic saline as maintenance fluid therapy. Blood tests, urinary indices, plasma levels of aldosterone, arginine-vasopressin, and net water-electrolyte balance indicated that participants were dehydrated on admission. Although nearly 50% of participants still had arginine-vasopressin levels that would have been expected to produce maximum antidiuresis at the end of surgery, electrolyte-free water clearance indicated that almost all participants were able to excrete net free water. No participant became hyponatremic. CONCLUSIONS: The use of moderately hypotonic fluid therapy after correction of extracellular fluid deficit is not necessarily associated with post-operative hyponatremia. IMPACT: Our observations show that in acutely ill normonatremic children not only the composition but also the amount of volume infused influence on the risk of hyponatremia. Our observations also suggest that perioperative administration of hypotonic fluid therapy is followed by a tendency towards hyponatremia if extracellular fluid depletion is left untreated. After correcting extracellular deficit almost all patients were able to excrete net free water. This occurred despite nearly 50% of the cohort having high circulating plasma levels of arginine-vasopressin at the end of surgery, suggesting a phenomenon of renal escape from arginine-vasopressin-induced antidiuresis.

Capnodynamics - noninvasive cardiac output and mixed venous oxygen saturation monitoring in children.

Hemodynamic monitoring in children is challenging for many reasons. Technical limitations in combination with insufficient validation against reference methods, makes reliable monitoring systems difficult to establish. Since recent studies have highlighted perioperative cardiovascular stability as an important factor for patient outcome in pediatrics, the need for accurate hemodynamic monitoring methods in children is obvious. The development of mathematical processing of fast response mainstream capnography signals, has allowed for the development of capnodynamic hemodynamic monitoring. By inducing small changes in ventilation in intubated and mechanically ventilated patients, fluctuations in alveolar carbon dioxide are created. The subsequent changes in carbon dioxide elimination can be used to calculate the blood flow participating in gas exchange, i.e., effective pulmonary blood flow which equals the non-shunted pulmonary blood flow. Cardiac output can then be estimated and continuously monitored in a breath-by-breath fashion without the need for additional equipment, training, or calibration. In addition, the method allows for mixed venous oxygen saturation (SvO2) monitoring, without pulmonary artery catheterization. The current review will discuss the capnodyamic method and its application and limitation as well as future potential development and functions in pediatric patients.

How to report drug concentrations or classic pharmacokinetics in regional anesthesia and pain medicine: what information needs to be provided?

When reporting individual drug concentrations or proper pharmacokinetic data, it is important to adequately report the circumstances associated with sampling, storing, analysis methodology and pharmacokinetic modelling. If this is not done in sufficient detail it will be impossible to properly evaluate the validity of the results. The present text represents a suggested approach on what to report when you are contemplating to submit a manuscript to regional anesthesia and pain medicine, this to achieve relevant standards in this context.

Intranasal dexmedetomidine sedation for paediatric MRI by radiology personnel: A retrospective observational study.

BACKGROUND: MRI often requires sedation or anaesthesia to ensure good image quality in paediatric patients. Access to paediatric anaesthesia services is, however, a limiting factor for effective paediatric MRI service, and alternative sedation methods are, therefore, warranted. OBJECTIVE: To investigate the efficacy and safety of an intranasal dexmedetomidine sedation program for paediatric MRI, without immediate presence of anaesthesia personnel. DESIGN: Single institution retrospective observational study. SETTING: Tertiary care paediatric hospital. PATIENTS: Children 0 to 12 years, ASA risk class 1 or 2 with heart rate within age-appropriate limit. INTERVENTION: Radiology personnel administered an initial dose of intranasal dexmedetomidine of 4 µg kg -1 followed by a second dose of 2 µg kg -1 to the patients if needed. Recordings of image quality, critical events, heart rate, pulse oximetry saturation and noninvasive blood pressure before and after dexmedetomidine administration were made. MAIN OUTCOME MEASURES: Changes in haemodynamic and respiratory data before vs. after intranasal dexmedetomidine were analysed for changes, and the incidence of critical events was evaluated as well as rate of successful MRI scans. RESULTS: One thousand and ninety-one MRIs under intranasal dexmedetomidine sedation were included (mean age 34 months, 95% confidence interval (CI), 33 to 36, 599 male individuals). A success rate of 93% (95% CI, 91 to 94%) was found. No major critical events were recorded, total incidence of minor issues was 0.2% (95% CI, 0 to 0.7%). Five children had a heart rate under a preset minimal limit after dexmedetomidine (0.4%; 95% CI, 0.1 to 0.9%). Significant decreases in heart rate and mean arterial pressure, within acceptable limits not requiring intervention, was seen after dexmedetomidine administration. CONCLUSION: Intranasal dexmedetomidine sedation without immediate presence of anaesthesia personnel appears to be well tolerated and associated with minimal interference on MRI image quality. TRIAL REGISTRATION: clinicaltrials.org NCT05163704, retrospectively registered.

Severe Covid-19 and acute pulmonary hypertension: 24-month follow-up regarding mortality and relationship to initial echocardiographic findings and biomarkers.

INTRODUCTION: Critically ill Covid-19 patients are likely to develop the sequence of acute pulmonary hypertension (aPH), right ventricular strain, and eventually right ventricular failure due to currently known pathophysiology (endothelial inflammation plus thrombo-embolism) that promotes increased pulmonary vascular resistance and pulmonary artery pressure. Furthermore, an in-hospital trans-thoracic echocardiography (TTE) diagnosis of aPH is associated with a substantially increased risk of early mortality. The aim of this retrospective observational follow-up study was to explore the mortality during the 1-24-month period following the TTE diagnosis of aPH in the intensive care unit (ICU). METHODS: A previously reported cohort of 67 ICU-treated Covid-19 patients underwent an electronic medical chart-based follow-up 24 months after the ICU TTE. Apart from the influence of aPH versus non-aPH on mortality, several TTE parameters were analyzed by the Kaplan-Meier survival plot technique (K-M). The influence of biomarkers for heart failure (NTproBNP) and myocardial injury (Troponin-T), taken at the time of the ICU TTE investigation, was analyzed using receiver-operator characteristics curve (ROC) analysis. RESULTS: The overall mortality at the 24-month follow-up was 61.5% and 12.8% in group aPH and group non-aPH, respectively. An increased relative mortality risk continued to be present in aPH patients (14.3%) compared to non-aPH patients (5.6%) during the 1-24-month period. The easily determined parameter of a tricuspid valve regurgitation, allowing a measurement of a systolic pulmonary artery pressure (regardless of magnitude), was associated with a similar K-M outcome as the generally accepted diagnostic criteria for aPH (systolic pulmonary artery pressure >35 mmHg). The biomarker values of NTproBNP and Troponin-T at the time of the TTE did not result in any clinically useful ROC analysis data. CONCLUSION: The mortality risk was increased up to 24 months after the initial examination in ICU-treated Covid-19 patients with a TTE diagnosis of aPH, compared to non-aPH patients. Certain individual TTE parameters were able to discriminate 24-month risk of morality.

Local Anesthetic Cardiac Toxicity Is Mediated by Cardiomyocyte Calcium Dynamics.

BACKGROUND: Long-lasting local anesthetic use for perioperative pain control is limited by possible cardiotoxicity (e.g., arrhythmias and contractile depression), potentially leading to cardiac arrest. Off-target cardiac sodium channel blockade is considered the canonical mechanism behind cardiotoxicity; however, it does not fully explain the observed toxicity variability between anesthetics. The authors hypothesize that more cardiotoxic anesthetics (e.g., bupivacaine) differentially perturb other important cardiomyocyte functions (e.g., calcium dynamics), which may be exploited to mitigate drug toxicity. METHODS: The authors investigated the effects of clinically relevant concentrations of racemic bupivacaine, levobupivacaine, or ropivacaine on human stem cell-derived cardiomyocyte tissue function. Contractility, rhythm, electromechanical coupling, field potential profile, and intracellular calcium dynamics were quantified using multielectrode arrays and optical imaging. Calcium flux differences between bupivacaine and ropivacaine were probed with pharmacologic calcium supplementation or blockade. In vitro findings were correlated in vivo using an anesthetic cardiotoxicity rat model (females; n = 5 per group). RESULTS: Bupivacaine more severely dysregulated calcium dynamics than ropivacaine in vitro (e.g., contraction calcium amplitude to 52 ± 11% and calcium-mediated repolarization duration to 122 ± 7% of ropivacaine effects, model estimate ± standard error). Calcium supplementation improved tissue contractility and restored normal beating rhythm (to 101 ± 6%, and 101 ± 26% of control, respectively) for bupivacaine-treated tissues, but not ropivacaine (e.g., contractility at 80 ± 6% of control). Similarly, calcium pretreatment mitigated anesthetic-induced arrhythmias and cardiac depression in rats, improving animal survival for bupivacaine by 8.3 ± 2.4 min, but exacerbating ropivacaine adverse effects (reduced survival by 13.8 ± 3.4 min and time to first arrhythmia by 12.0 ± 2.9 min). Calcium channel blocker nifedipine coadministration with bupivacaine, but not ropivacaine, exacerbated cardiotoxicity, supporting the role of calcium flux in differentiating toxicity. CONCLUSIONS: Our data illustrate differences in calcium dynamics between anesthetics and how calcium may mitigate bupivacaine cardiotoxicity. Moreover, our findings suggest that bupivacaine cardiotoxicity risk may be higher than for ropivacaine in a calcium deficiency context.

The Retro Superior Costotransverse Ligament Space as a New Target for Ultrasound-Guided Intertransverse Process Block: A Report of 2 Cases.

An intertransverse process block (ITPB) is a paraspinal thoracic nerve block technique, where the local anesthetic (LA) is injected into the thoracic intertransverse tissue complex posterior to the superior costotransverse ligament (SCTL). Although an ITPB can be ultrasound-guided, it is performed using surrogate bony landmarks without even identifying the SCTL. This report describes a transverse ultrasound imaging technique to identify the retro-SCTL space and perform an ITPB with a retro-SCTL space injection, in 2 patients undergoing video-assisted thoracoscopic surgery. The resultant bilateral, symmetrical, thoracolumbar anesthesia was consistent with epidural spread of the LA and effective for perioperative analgesia.