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.

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.

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.

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.

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.

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.

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.

Cardiac Output Assessments in Anesthetized Children: Dynamic Capnography Versus Esophageal Doppler.

BACKGROUND: The objective of this study was to compare esophageal Doppler cardiac output (COEDM) against the reference method effective pulmonary blood flow cardiac output (COEPBF), for agreement of absolute values and ability to detect change in cardiac output (CO) in pediatric surgical patients. Furthermore, the relationship between these 2 methods and noninvasive blood pressure (NIBP) parameters was evaluated. METHODS: Fifteen children American Society of Anesthesiology (ASA) I and II (median age, 8 months; median weight, 9 kg) scheduled for surgery were investigated in this prospective observational cohort study. Baseline COEPBF/COEDM/NIBP measurements were made at positive end-expiratory pressure (PEEP) 3 cm H2O. PEEP was increased to 10 cm H2O and COEPBF/COEDM/NIBP was recorded after 1 and 3 minutes. PEEP was then lowered to 3 cm H2O, and all measurements were repeated after 3 minutes. Finally, 20-µg kg-1 intravenous atropine was given with the intent to increase CO, and all measurements were recorded again after 5 minutes. Paired recordings of COEDM and COEPBF were examined for agreement and trending ability, and all parameters were analyzed for their responses to the hemodynamic challenges. RESULTS: Bias between COEDM and COEPBF (COEDM - COEPBF) was -17 mL kg-1 min-1 (limits of agreement, -67 to +33 mL kg-1 min-1) with a mean percentage error of 32% (95% confidence interval [CI], 25-37) and a concordance rate of 71% (95% CI, 63-80). The hemodynamic interventions caused by PEEP manipulations resulted in significant decrease in COEPBF absolute numbers (155 mL kg-1 min-1 [95% CI, 151-159] to 127 mL kg-1 min-1 [95% CI, 113-141]) and a corresponding relative decrease of 18% (95% CI, 14-22) 3 minutes after application of PEEP 10. No corresponding decreases were detected by COEDM. Mean arterial pressure showed a relative decrease with 5 (95% CI, 2-8) and 6% (95% CI, 2-10) 1 and 3 minutes after the application of PEEP 10, respectively. Systolic arterial pressure showed a relative decrease of 5% (95% CI, 2-10) 3 minutes after application of PEEP 10. None of the recorded parameters responded to atropine administration except for heart rate that showed a 4% relative increase (95% CI, 1-7, P = .02) 5 minutes after atropine. CONCLUSIONS: COEDM was unable to detect the reduction of CO cause by increased PEEP, whereas COEPBF and to a minimal extent NIBP detected these changes in CO. The ability of COEPBF to react to minor reductions in CO, before noticeable changes in NIBP are seen, suggests that COEPBF may be a potentially useful tool for hemodynamic monitoring in mechanically ventilated children.

Role of information and preparation for improvement of pediatric perioperative care.

The perioperative period is a significant and stressful experience that may cause negative consequences in children, both in a short-term and long-term perspective. Despite a wide base of evidence stating the importance of adequate preparation to reduce anxiety, improve coping, cooperation and enhance recovery, many children continue to report that they feel unprepared for their perioperative experience. To secure children's right to request and need for preparation, the content, format, and availability of existing programs need to be scrutinized. Preparation programs in perioperative care must change from simply providing information to embracing the importance of children's need to process the information provided in order to learn and understand. Interactive web-based technology can function as a significant resource for preparation of children for perioperative procedures. By changing perspective from children's need for information to their need for learning and by developing preparation programs including adequate educational principles, web-based technology can be used to its fullest advantage as a healthcare learning and preparation resource.

Blood pressure and flow in pediatric anesthesia: An educational review.

During recent years, a lot of interest has been focused on blood pressure in the context of pediatric anesthesia, trying to define what is normal in relation to age and what numeric values that should be regarded as hypotension, needing active intervention. However, blood pressure is mainly measured as a proxy for flow, that is, cardiac output. Thus, just focusing on specific blood pressure numbers may not necessarily be very useful or appropriate. The aim of this educational review is to put the issue of intraoperative blood pressure in the context of pediatric anesthesia in further perspective.

Capnodynamics-Measuring cardiac output via ventilation.

Recent studies have identified stable hemodynamics as a contributing factor to improve outcome in pediatric anesthesia. So far, most of the hemodynamic monitoring methods applied in children have been complex to apply and often not satisfactory validated. Standard mainstream carbon dioxide analysis in combination with real-time mathematical analysis of the measured capnography data has enabled the development of dynamic capnography, a non-invasively cardiac output monitoring method that can be applied without user practice or need for calibrations. Capnodynamic cardiac output assessment has been extensively validated against gold standard reference methods, both in experimental and clinical settings. This review will describe the principle behind dynamic capnography measurement of cardiac output and mixed venous oxygen saturation. Additionally, the methods limitations and challenges when applied in children will be delineated.

Non-invasive capnodynamic mixed venous oxygen saturation during major changes in oxygen delivery.

Mixed venous oxygen saturation (SvO2) is an important variable in anesthesia and intensive care but currently requires pulmonary artery catheterization. Recently, non-invasive determination of SvO2 (Capno-SvO2) using capnodynamics has shown good agreement against CO-oximetry in an animal model of modest hemodynamic changes. The purpose of the current study was to validate Capno-SvO2 against CO-oximetry during major alterations in oxygen delivery. Furthermore, evaluating fiberoptic SvO2 for its response to the same challenges. Eleven mechanically ventilated pigs were exposed to oxygen delivery changes: increased inhaled oxygen concentration, hemorrhage, crystalloid and blood transfusion, preload reduction and dobutamine infusion. Capno-SvO2 and fiberoptic SvO2 recordings were made in parallel with CO-oximetry. Respiratory quotient, needed for capnodynamic SvO2, was measured by analysis of mixed expired gases. Agreement of absolute values between CO-oximetry and Capno-SvO2 and fiberoptic SvO2 respectively, was assessed using Bland-Altman plots. Ability of Capno- SvO2 and fiberoptic SvO2 to detect change compared to CO-oximetry was assessed using concordance analysis. The interventions caused significant hemodynamic variations. Bias between Capno-SvO2 and CO-oximetry was + 3% points (95% limits of agreements - 7 to + 13). Bias between fiberoptic SvO2 and CO-oximetry was + 1% point, (95% limits of agreements - 7 to + 9). Concordance rate for Capno-SvO2 and fiberoptic SvO2 vs. CO-oximetry was 98% and 93%, respectively. Capno-SvO2 generates absolute values close to CO-oximetry. The performance of Capno-SvO2 vs. CO-oximetry was comparable to the performance of fiberoptic SvO2 vs. CO-oximetry. Capno-SvO2 appears to be a promising tool for non-invasive SvO2 monitoring.

A Continuous Noninvasive Method to Assess Mixed Venous Oxygen Saturation: A Proof-of-Concept Study in Pigs.

BACKGROUND: Mixed venous oxygen saturation (Svo2) is important when evaluating the balance between oxygen delivery and whole-body oxygen consumption. Monitoring Svo2 has so far required blood samples from a pulmonary artery catheter. By combining volumetric capnography, for measurement of effective pulmonary blood flow, with the Fick principle for oxygen consumption, we have developed a continuous noninvasive method, capnodynamic Svo2, for assessment of Svo2. The objective of this study was to validate this new technique against the gold standard cardiac output (CO)-oximetry Svo2 measurement of blood samples obtained from a pulmonary artery catheter and to assess the potential influence of intrapulmonary shunting. METHODS: Eight anesthetized mechanically ventilated domestic-breed piglets of both sexes (median weight 23.9 kg) were exposed to a series of interventions intended to reduce as well as increase Svo2. Simultaneous recordings of capnodynamic and CO-oximetry Svo2 as well as shunt fraction, using the Berggren formula, were performed throughout the protocol. Agreement of absolute values for capnodynamic and CO-oximetry Svo2 and the ability for capnodynamic Svo2 to detect change were assessed using Bland-Altman plot and concordance analysis. RESULTS: Overall bias for capnodynamic versus CO-oximetry Svo2 was -1 percentage point (limits of agreement -13 to +11 percentage points), a mean percentage error of 22%, and a concordance rate of 100%. Shunt fraction varied between 13% at baseline and 22% at the end of the study and was associated with only minor alterations in agreement between the tested methods. CONCLUSIONS: In the current experimental setting, capnodynamic assessment of Svo2 generates absolute values very close to the reference method CO-oximetry and is associated with 100% trending ability.

Acute pulmonary hypertension and short-term outcomes in severe Covid-19 patients needing intensive care.

INTRODUCTION: Critically ill Covid-19 pneumonia patients are likely to develop the sequence of acute pulmonary hypertension, right ventricular (RV) strain, and eventually RV failure due to known pathophysiology (endothelial inflammation plus thrombo-embolism) that promotes increased pulmonary vascular resistance and pulmonary artery pressure. This study aimed to investigate the occurrence of acute pulmonary hypertension (aPH) as per established trans-thoracic echocardiography (TTE) criteria in Covid-19 patients receiving intensive care and to explore whether short-term outcomes are affected by the presence of aPH. METHODS: Medical records were reviewed for patients treated in the intensive care units at a tertiary university hospital over a month. The presence of aPH on the TTE was noted, and plasma NTproBNP and troponin were measured as markers of cardiac failure and myocardial injury, respectively. Follow-up data were collected 21 d after the performance of TTE. RESULTS: In total, 26 of 67 patients (39%) had an assessed systolic pulmonary artery pressure of > 35 mmHg (group aPH), meeting the TTE definition of aPH. NTproBNP levels (median [range]: 1430 [102-30 300] vs. 470 [45-29 600] ng L-1 ; P = .0007), troponin T levels (63 [22-352] vs. 15 [5-407] ng L-1 ; P = .0002), and the 21-d mortality rate (46% vs. 7%; P < .001) were substantially higher in patients with aPH compared to patients not meeting aPH criteria. CONCLUSION: TTE-defined acute pulmonary hypertension was frequently observed in severely ill Covid-19 patients. Furthermore, aPH was linked to biomarker-defined myocardial injury and cardiac failure, as well as an almost sevenfold increase in 21-d mortality.

Primary spread of caudal blockade in children: the possible limiting role of the lumbar spinal cord enlargement (tumenescence) in combination with the cerebrospinal fluid rebound mechanism.

BACKGROUND: Despite being the most frequently used pediatric nerve block, certain aspects of the initial intraspinal spread of local anesthetics when performing a caudal block need further elucidation. The fact that injected volumes of 0.7-1.3 mL kg-1 initially only reach the thoraco-lumbar junction, with only a few vertebral segments difference despite the huge difference in injected volume, still has no apparent explanation. We hypothesize that the narrowing of the epidural space caused by the lumbar spinal enlargement may provide an anatomical barrier causing this restriction of initial spread, alone or in combination with increased intrathecal pressure caused by the "cerebrospinal fluid rebound mechanism." The aim of this observational study was to find support for or refute this hypothesis. METHODS: Twenty nine MRI scans of the vertebral column, performed in children 0-6 years of age, was identified from the radiographic imaging computer system and analyzed for the vertebral level of the maximum of the lumbar spinal enlargement (Associated anatomical data related to the spinal canal, the dura mater, and the spinal cord were also recorded. RESULTS: The maximum of the lumbar spinal enlargement was found at a median vertebral level of Th 11 (IQR 11-11). CONCLUSION: The maximum of the lumbar spinal enlargement is located at the Th 11 vertebral level. Although not entirely conclusive, the findings of the present study do support the notion that the lumbar spinal enlargement, in combination with the CSF rebound mechanism, may be the factors limiting the initial spread of a caudal block to the thoraco-lumbar junction.

Rapid systemic uptake of naloxone after intranasal administration in children.

BACKGROUND: Naloxone has a high affinity for the µ-opioid receptor and acts as a competitive antagonist, thus reversing the effects of opioids. Naloxone is often administrated intravenously, but there is a growing interest in the intranasal route in treating patients with opioid overdose, and in reversing effects after therapeutic use of opioids. As administration is painless and no intravenous access is needed, the intranasal route is especially useful in children. AIM: The aim of this study was to investigate the uptake of naloxone 0.4 mg/ml during the first 20 min after administration as a nasal spray in a pediatric population, with special focus on the time to achieve maximum plasma concentration. METHODS: Twenty children, 6 months-10 years, were included in the study. The naloxone dose administered was 20 µg/kg, maximum 0.4 mg, divided into repeated doses of 0.1 ml in each nostril. Venous blood samples were collected at 5, 10, and 20 min after the end of administration. RESULTS: All patients had quantifiable concentrations of naloxone in venous blood at 5 min, and within 20 min, peak concentration had been reached in more than half of the children. At 20 min after intranasal administration, the plasma naloxone concentrations were within the range of 2-6 nanogram/ml. CONCLUSION: This study confirms the clinical experience that the rapid effect of naloxone after intranasal administration in children was reflected in rapid systemic uptake to achieve higher peak plasma concentrations than previously reported in adults.

Cerebral blood flow alterations associated with high volume caudal block in infants.

BACKGROUND: High-volume (1.5 ml kg-1) caudal block in infants results in major reductions of cerebral blood flow velocity (CBFV) and cerebral oxygenation, caused by rostral CSF movement which increases intracranial pressure. The primary aim of this study was to determine the relationship between injected volume and CBFV changes. We hypothesised that this volume-blood flow relationship would have a similar albeit inverted shape to the well-known intracranial pressure volume-pressure curve. METHODS: Fifteen subjects, age 0-6 months, mean (range) weight 4.9 (2.1-6.4) kg, were studied. A 1.5 ml kg-1 caudal injection of 0.2% ropivacaine was administered in three phases separated by two pauses. Subjects were randomised into five groups, in whom the pauses were implemented at different pre-set proportions of the total injected volume. Middle cerebral artery Doppler ultrasonography was used for CBFV measurements (Vmax, peak CBF velocity; Vmin, lowest CBF velocity; velocity time index). Mean flow velocity, pulsatility index, and resistivity index were calculated, and haemodynamic parameters were recorded. RESULTS: CBFV parameters decreased in all patients. The most affected parameter, Vmin, was reduced by ∼50% (range 15-68%) compared with baseline. There was a nonlinear relationship between the volume of the first phase injection and the CBFV measurement during the first pause. Across all time points, there was a linear relationship between volume administered and CBFV. Systemic haemodynamic parameters remained stable throughout the study. CONCLUSIONS: Injection pauses appear to attenuate adverse CBFV increases during administration of a high-volume caudal block.

End-expiratory lung volume assessment using helium and carbon dioxide in an experimental model of pediatric capnoperitoneum.

BACKGROUND: Capnoperitoneum during laparoscopy leads to cranial shift of the diaphragm, loss in lung volume, and risk of impaired gas exchange. Infants are susceptible to these changes and bedside assessment of lung volume during laparoscopy might assist with optimizing the ventilation. Thus, the primary aim was to investigate the monitoring value of a continuous end-expiratory lung volume (EELV) assessment method based on CO2 dynamics ( EELV CO 2 ) in a pediatric capnoperitoneum model by evaluating the correlation and trending ability against helium washout (EELVHe ). METHODS: Intra-abdominal pressure (IAP) was randomly varied between 0, 6, and 12 mm Hg with CO2 insufflation, while positive end-expiratory pressure (PEEP) levels of 3, 6, and 9 cm H2 O were randomly applied in eight anesthetized and mechanically ventilated chinchilla rabbits. Concomitant EELV CO 2 and EELVHe and lung clearance index (LCI) were obtained under each experimental condition. RESULTS: Significant correlations were found between EELV CO 2 and EELVHe before capnoperitoneum (r = .85, P < .001), although increased IAP distorted this relationship. The negative influence of IAP was counteracted by the application of PEEP 9, which restored the correlation between EELV CO 2 and EELVHe and resulted in 100% concordance rate between the methods regarding changes in lung volume. EELVHe and LCI showed a curvilinear relationship, and an EELVHe of approximately 20 mL kg-1 , determined with a receiver operating characteristic curve, was associated with near-normal LCI values. CONCLUSION: In this animal model of pediatric capnoperitoneum, reliable assessment of changes in EELV based on EELV CO 2 requires an open lung strategy, defined as EELV above approximately 20 mL kg-1 .

Determination of adequate positive end-expiratory pressure level required for carbon dioxide homeostasis in an animal model of infant laparoscopy.

BACKGROUND: Capnoperitoneum provides a ventilatory challenge due to reduction in end-expiratory lung volume and peritoneal carbon dioxide absorption in both children and adults. The primary aim of this controlled interventional trial was to determine the positive end-expiratory pressure (PEEP) level needed to ensure for adequate carbon dioxide clearance and preservation of carbon dioxide homeostasis in an experimental model of infant laparoscopy. The secondary aim was to evaluate potential effects on cardiac output of PEEP and abdominal pressure level variations in the same setting. METHODS: Eight chinchilla bastard rabbits were anesthetized and mechanically ventilated. Intra-abdominal pressures were randomly set to 0, 6, and 12 mm Hg by carbon dioxide insufflation. Carbon dioxide clearance using volumetric capnography, arterial blood gas data, and cardiac output was recorded, while PEEP 3, 6, and 9 cmH2 O were applied in a random order. RESULTS: A PEEP of 9 cmH2 O showed restoration of carbon dioxide clearance without causing changes in arterial partial pressure of carbon dioxide and bicarbonate and with no associated deterioration in cardiac output. CONCLUSION: The results promote a PEEP level of 9 cmH2 O in this model of infant capnoperitoneum to allow for adequate carbon dioxide removal with subsequent preservation of carbon dioxide homeostasis. The use of high PEEP was not associated with any decrease in cardiac output.