[Acute hyponatremia can be a life-threatening condition. Recommendations for hydration of children in surgery and acute disease reduces the risk]. / Akut hyponatremi kan vara ett livshotande tillstånd--Rekommendationer för vätsketillförsel till barn vid kirurgi och akut sjukdom minskar risken.

Hyponatremia is the most frequent electrolyte abnormality seen postoperatively in pediatric patients receiving maintenance fluid therapy. Hyponatremia is also common in acute pediatric illness. The main factors contributing to hyponatremia in these conditions are increased secretion of antidiuretic hormone (ADH) and routine use of sodium hypotonic fluids. An increased ADH secretion results in an impaired ability to excrete free water. If the sodium concentration falls to less than 125 mmol/L hyponatremic encephalopathy might develop, resulting in cerebral edema. This is avoided if hypotonic maintenance fluids are not used perioperatively or for rehydration or maintenance during acute critical illness in children.

The development of pediatric anesthesia and intensive care in Scandinavia.

The initiation and development of pediatric anesthesia and intensive care have much in common in the Scandinavian countries. The five countries had to initiate close relations and cooperation in all medical disciplines. The pediatric anesthesia subspecialty took its first steps after the Second World War. Relations for training and exchange of experiences between Scandinavian countries with centers in Europe and the USA were a prerequisite for development. Specialized pediatric practice was not a full-time position until during the 1950s, when the first pediatric anesthesia positions were created. Scandinavian anesthesia developed slowly. In contrast, Scandinavia pioneered both adult and certainly pediatric intensive care. The pioneers were heavily involved in the teaching and training of anesthetists and nurses. This was necessary to manage the rapidly increasing work. The polio epidemics during the 1950s initiated a combination of clinical development and technical innovations. Blood gas analyses technology and interpretation in combination with improved positive pressure ventilators were developed in Scandinavia contributing to general and pediatric anesthesia and intensive care practice. Scandinavian specialist training and accreditation includes both anesthesia and intensive care. Although pediatric anesthesia/intensive care is not a separate specialty, an 'informal accreditation' for a specialist position is obtained after training. The pleasure of working in a relatively small group of devoted colleagues and staff has persisted from the pioneering years. It is still one of the most inspiring and pleasant gifts for those working in this demanding specialty.

Recruitment and PEEP level influences long-time aeration in saline-lavaged piglets: an experimental model.

OBJECTIVES: To evaluate aeration/ventilation in saline-lavaged piglets during a 3-h follow-up after a recruitment maneuver (RM)/PEEP titration compared with PEEP 10 cmH2O without a RM. BACKGROUND: Lung recruitment and PEEP titration are used to find a PEEP preventing repetitive opening/collapsing of lung. METHODS: Twenty-one lung-lavaged piglets, mean age 7 weeks and mean weight 10 kg; a RM-group and a PEEP10-group, were ventilated at PEEP 5 cmH2O (baseline) followed by zero PEEP ventilation. In the RM-group, tidal elimination of CO2 and dynamic compliance (Cdyn) guided recruitment and PEEP titration, respectively. A final 3-h ventilation followed using PEEP 2 cmH2O above the first decline of Cdyn and end-inspiratory pressure (EIP) for a target tidal volume (VT) of 10 ml · kg(-1). In the PEEP10-group, PEEP 10 cmH2O without a RM was used during the final 3-h ventilation. CT scans and blood gases were repeated every 30 min. Airway pressures, Cdyn and hemodynamics were continuously recorded. RESULTS: Aeration improved without differences between groups. The RM-group PEEP level of 10 ± 0.6 cmH2O did not differ from the PEEP10-group. Compared to baseline EIP was lower in the RM-group after 3-h ventilation. In both groups, driving pressure (DP) was lower and Cdyn higher than baseline. In the RM-group, final EIP and DP were lower and Cdyn higher than in the PEEP10-group. CONCLUSIONS: Both RM/PEEP titration and PEEP elevation resulted in improved aeration without differences between groups at the end point. Lung aeration was achieved at lower EIP and DP and higher Cdyn in the RM-group than in the PEEP10-group.

Lung aeration during ventilation after recruitment guided by tidal elimination of carbon dioxide and dynamic compliance was better than after end-tidal carbon dioxide targeted ventilation: a computed tomography study in surfactant-depleted piglets.

OBJECTIVE: To test the hypothesis that tidal elimination of carbon dioxide and dynamic compliance guided lung recruitment and positive end-expiratory pressure titration in surfactant-depleted piglets result in improved aeration (repeated computed tomography scans) and reduced ventilation pressures compared to those of a control group with conventional end-tidal carbon dioxide targeted ventilation. DESIGN: Prospective animal investigation. SETTING: Clinical physiology research laboratory. SUBJECTS: Seventeen saline-lavaged piglets. INTERVENTIONS: The piglets were initially ventilated at an end-inspiratory pressure of 20 cm H2O, a positive end-expiratory pressure of 5 cm H2O, and a tidal volume of 10 mL kg for an end-tidal carbon dioxide target of 30-45 torr followed by 5 mins of ventilation without positive end-expiratory pressure. After this, the control group was ventilated for the same end-tidal carbon dioxide target during the study period. In the recruitment group, the protocol started with an increase of the positive end-expiratory pressure to 15 cm H2O. The end-inspiratory pressure was then increased in steps of 3 cm H2O to a tidal elimination of carbon dioxide peak/plateau in one recruitment group and further increased in two steps in a second recruitment group. A downward positive end-expiratory pressure titration was followed by continuous dynamic compliance monitoring. The "open lung positive end-expiratory pressure" was set 2 cm H2O above the positive end-expiratory pressure at the first dynamic compliance decline and used for a final "open lung ventilation" period. MEASUREMENTS AND MAIN RESULTS: The recruitment groups showed better aeration, lower ventilatory pressure amplitude, and better dynamic compliance than the control group at the end of the study. Recruitment using airway pressures above the tidal elimination of carbon dioxide peak/plateau did not improve aeration. Using end-tidal carbon dioxide targeted ventilation in the control group restored aeration after the ventilation without positive end-expiratory pressure, but no recruitment or improvement of dynamic compliance was measured. CONCLUSIONS: Aeration was significantly better after recruitment and positive end-expiratory pressure titration than in a control group managed by "conventional" end-tidal carbon dioxide targeted ventilation. An increase of the end-inspiratory pressure above the tidal elimination of carbon dioxide peak/plateau did not result in an increased amount of normally aerated lung. A recruitment maneuver resulted in a lower ventilatory amplitude for achieving a target tidal volume and better dynamic compliance at the end of the study period compared to those of the control group.

Intraoperative thromboelastometry is associated with reduced transfusion prevalence in pediatric cardiac surgery.

BACKGROUND: The majority of pediatric cardiac surgery patients receive blood transfusions. We hypothesized that the routine use of intraoperative thromboelastometry to guide transfusion decisions would reduce the overall proportion of patients receiving transfusions in pediatric cardiac surgery. METHODS: One hundred pediatric cardiac surgery patients were included in the study. Fifty patients (study group) were prospectively included and compared with 50 procedure- and age-matched control patients (control group). In the study group, thromboelastometry, performed during cardiopulmonary bypass, guided intraoperative transfusions. Intraoperative and postoperative transfusions of packed red blood cells, fresh frozen plasma, platelets, and fibrinogen concentrates, and postoperative blood loss and hemoglobin levels were compared between the 2 groups. RESULTS: The proportion of patients receiving any intraoperative or postoperative transfusion of packed red blood cells, fresh frozen plasma, platelets, or fibrinogen concentrates was significantly lower in the study group than in the control group (32 of 50 [64%] vs 46 of 50 [92%], respectively; P < 0.001). Significantly fewer patients in the study group received transfusions of packed red blood cells (58% vs 78%, P = 0.032) and plasma (14% vs 78%, P < 0.001), whereas more patients in the study group received transfusions of platelets (38% vs 12%, P = 0.002) and fibrinogen concentrates (16% vs 2%, P = 0.015). Neither postoperative blood loss nor postoperative hemoglobin levels differed significantly between the study group and the control group. CONCLUSIONS: The results suggest that routine use of intraoperative thromboelastometry in pediatric cardiac surgery to guide transfusions is associated with a reduced proportion of patients receiving transfusions and an altered transfusion pattern.

A study of the physiological consequences of sympathetic denervation of the heart caused by the arterial switch procedure.

BACKGROUND: The arterial switch operation is the corrective operation for transposition of the great arteries, defined as the combination of concordant atrioventricular and discordant ventriculo-arterial connections, but there have been concerns about silent subendocardial ischaemia on exercise and coronary artery growth. The arterial switch divides the majority of the sympathetic nerves entering the heart; we have studied the effects of coronary flow and sensitivity to catecholamine stimulation in an animal model. METHODS: A total of 10 piglets were operated on cardiopulmonary bypass with section and resuturing of aortic trunk, pulmonary artery and both coronary arteries, with 13 sham-operated controls. After 5-7 weeks of recovery, seven simulated switch survivors and 13 controls were studied. RESULTS: Basal heart rate was significantly higher in switch piglets: in vivo mean (standard deviation) 112 (12) versus sham 100 (10) beats per minute, (p = 0.042); in vitro (Langendorff preparation): 89 (9) versus sham 73 (8) beats per minute (p = 0.0056). In vivo maximal heart rate in response to epinephrine was increased in switch piglets, 209 (13) versus 190 (17) beats per minute (p = 0.044). In vitro dose-response curves to norepinephrine were shifted leftward and upwards (p = 0.0014), with an 80% increase in heart rate induced by 0.095 (0.053) norepinephrine micromole per litre perfusate in switch hearts versus 0.180 (0.035) norepinephrine micromole per litre (p = 0.023). Increase in coronary flow on norepinephrine stimulation and maximal coronary flow were significantly reduced in switch hearts: 0.3 (0.2) versus 0.8 (0.4) millilitre per gram heart weight (p = 0.045) and 2.5 (0.4) versus 3.1 (0.4) millilitre per gram heart (p = 0.030), respectively. CONCLUSIONS: A combination of increased intrinsic heart rate, increased sensitivity to chronotropic actions of norepinephrine, and a decreased maximal coronary flow creates potential for a mismatch between perfusion and energy demands.

Improved response time with a new miniaturised main-stream multigas monitor.

BACKGROUND: For paediatric monitoring and demanding applications such as metabolic monitoring and measurements of functional residual capacity combining gas concentration with flow/volume measurements the performance of side-stream monitors (SSGM) is suboptimal. The objective was to evaluate the performance of a miniaturised mainstream multigas monitor (MSGM) alleged to offer fast response gas monitoring. The MSGM uses infrared technique for measurements of carbon dioxide, nitrous oxide and inhalation agents and fuel cell technique for oxygen monitoring. The MSGM performance was com- pared to a state of the art side-stream monitor in a bench study. METHODS: Response time was measured in two bench study set ups; a high flow oxygen flush to achieve one step change in gas concentrations and during continuous ventilation using a circuit with an oxygen consuming/carbon dioxide producing lung model connected to a ventilator. Averaged tracings from the tested monitors were used for calculation of the 90-10% decline of CO(2), the corresponding 10-90% incline of O(2) and N(2)O and of Isoflurane concentrations in the flush set up and at different inspired O(2) for the O(2) upslope and corresponding CO(2) down- slope during continuous ventilation at different breathing frequencies. Calibration gases with different concentrations of CO(2), O(2) and N(2)O were used for testing of accuracy. RESULTS: The MSGM response time for CO(2) was 96 (88-100) compared to 348 (340-352) ms for the SSGM (P < 0.001). Corresponding response times for O(2) was 108 (76-144), and 432 (360-448) ms (P < 0.001), respectively. At a respiratory rate of 60 BPM the SSGM trace was damped and sinusoidal whereas the MSGM displayed wider amplitude and a square waveform. The deviations from calibration gas values were within clinically acceptable range and linear for all gases over the concentration range studied for both monitors. CONCLUSIONS: The MSGM response time for CO(2) and O(2) was less than 1/3 of the SSGM. The performance of the MSGM was maintained at high breathing frequencies. The accuracy was within clinically acceptable limits for both monitors.

VTCO2 and dynamic compliance-guided lung recruitment in surfactant-depleted piglets: a computed tomography study.

OBJECTIVE: Using computed tomography (CT) as reference, our primary objectives were to test if maximal tidal elimination of carbon dioxide (VTCO2) could be used as a marker of "optimal recruitment," indicating maximal available lung tissue for gas exchange and if a decrease in dynamic compliance (Cdyn) indicated the beginning of lung collapse during a downward positive end-expiratory pressure (PEEP) titration. DESIGN: Prospective laboratory animal investigation. SETTING: Clinical physiology research laboratory. SUBJECTS: Six piglets undergoing lung lavage. INTERVENTIONS: Saline-lavaged piglets were initially ventilated without PEEP at a tidal volume (VT) of 10 mL/kg followed by baseline ventilation at end-inspiratory pressure (EIP) 25 cm H2O and PEEP 6 cm H2O. PEEP was increased to 12 or 15 cm H2O. Then EIP was increased in steps of 5 cm H2O and the EIP where VTCO2 peaked or leveled off was assumed to define optimally recruited lungs. A downward PEEP titration followed from 12 or 15 to 4 cm H2O in steps of 1 cm H2O. First decline of Cdyn was assumed to define onset of lung collapse. VTCO2 and Cdyn were continuously recorded and CT scans iterated for each change of ventilation. "Open-lung PEEP" was set 2 cm H2O above PEEP at the first Cdyn decline and was used for a final period of "open-lung ventilation." MEASUREMENTS AND MAIN RESULTS: CT images showed recruited lungs at peak VTCO2 and that a minimal amount of normally aerated lung was added by further increase in EIP. Cdyn declined just before CT scans indicated lung collapse. Compared with baseline, the target VT of 10 mL/kg was achieved at lower EIP and pressure amplitude (EIP-PEEP) during the final open-lung ventilation with more normally aerated and fewer collapsed lungs. Cdyn was doubled after recruitment. CONCLUSIONS: The lung recruitment maneuver was effective and lungs optimally recruited at maximal VTCO2. A fall in Cdyn indicated lung collapse during downward PEEP titration as confirmed by CT.

Myocardial substrates in children with congenital heart disease: relationship to substrate supply, age, growth and desaturation.

AIM: The myocardial uptake of substrates in children has only been investigated on a small scale. The purpose of this study was to define myocardial substrate uptake in relation to the arterial supply of substrates, age, growth and oxygen saturation. METHODS: Thirty patients with congenital heart disease, aged 3 months to 16 years, were studied during cardiac catheterization. Arterial and coronary sinus blood was analyzed for the major fuel metabolites and amino acids. RESULTS: The uptake of all major substrates correlated significantly with the arterial supply: free fatty acids (r = 0.52, p = 0.004), beta-hydroxybutyrate (r = 0.74, p < 0.0001), lactate (r = 0.70, p < 0.0001) and glucose (r = 0.48, p = 0.01). Free fatty acids were the dominant substrate, irrespective of age, growth and saturation. With age, there was an increase in the uptake of lactate (r = 0.61, p = 0.0004) and a decrease in the uptake of beta-hydroxybutyrate (r =-0.41, p = 0.02). In multivariate analyses, these changes were explained by the arterial supply of the substrates, while age per se did not contribute significantly. CONCLUSION: The uptake of myocardial metabolites correlated with the arterial supply. Free fatty acids were the dominant substrate at all ages. The uptake of lactate and beta-hydroxybutyrate, although varying with age, was also determined by the arterial supply.

Myocardial metabolism is better preserved after blood cardioplegia in infants.

BACKGROUND: We have previously reported improved hemodynamic function after blood cardioplegia in comparison with crystalloid cardioplegia. Furthermore, lactate was released from the heart after crystalloid cardioplegia but not after blood cardioplegia. The purpose of this study was to determine whether the difference in substrate metabolism between the two cardioplegia methods was restricted to lactate, or whether the difference in metabolic derangement was more extensive. METHODS: Thirty consecutive infants with complete atrioventricular septal defects were included in this prospective, randomized, controlled study. Arterial and coronary sinus blood concentrations of substrates and amino acids were measured after weaning from bypass. RESULTS: After crystalloid cardioplegia, there was a myocardial uptake of glutamate (p = 0.003), leucine (p = 0.03), lysine (p = 0.003), and beta-hydroxybutyrate (p = 0.004), whereas lactate was released (p = 0.03). After blood cardioplegia, there was a myocardial uptake of free fatty acids (p = 0.01) but no uptake of amino acids and no release of lactate. CONCLUSIONS: There are differences in myocardial substrate metabolism between blood cardioplegia and crystalloid cardioplegia, which involve carbohydrates and amino acids. The differences may include lipids but our data in this respect are not conclusive.

Blood cardioplegia provides superior protection in infant cardiac surgery.

BACKGROUND: We hypothesized that blood cardioplegia preserves myocardial metabolism and function more effectively than St Thomas' crystalloid cardioplegia in infant cardiac surgery. METHODS: Thirty infants with atrioventricular septal defects were randomly allocated to either blood or crystalloid intermittent cold (4 degrees C) cardioplegia. Arterial and coronary sinus blood was analyzed for lactate and oxygen. Cardiac output (thermodilution) and left ventricular function (echocardiography) were evaluated. RESULTS: The lactate concentration in coronary sinus blood early after bypass was significantly higher after crystalloid cardioplegia than after blood cardioplegia (2.1 +/- 0.3 vs 1.3 +/- 0.1 mmol/L, p = 0.006), with a significant myocardial release of lactate after crystalloid but not after blood cardioplegia. Oxygen extraction (arterial-coronary sinus O2 content) was higher early after crystalloid cardioplegia (3.02 +/- 0.13 vs 2.35 +/- 0.22 mmol/L, p = 0.01), possibly reflecting a difference in oxygen debt. The cardiac index was higher after blood cardioplegia (4.9 +/- 0.3 vs 4.0 +/- 0.3 L/min(-1)/m(-2), p = 0.04) and echocardiographic grading of left ventricular function was better (4.1 +/- 0.17 vs 3.5 +/- 0.22 arbitrary units, p = 0.046). CONCLUSIONS: This study indicates that blood cardioplegia preserves myocardial metabolism and function more effectively than crystalloid cardioplegia in infant cardiac surgery. The clinical significance of this finding is uncertain, but the more than 20% increase in cardiac index in the critical phase during weaning from bypass may be advantageous.

The dynostatic algorithm accurately calculates alveolar pressure on-line during ventilator treatment in children.

BACKGROUND: Monitoring of respiratory mechanics during ventilator treatment in paediatric intensive care is currently based on pressure and flow measurements in the ventilator or at the Y-piece. The characteristics of the tracheal tube will modify the pressures affecting the airways and alveoli in an unpredictable manner. The dynostatic algorithm (DSA), based on a one-compartment lung model, calculates the alveolar pressure during on-going ventilation. The DSA is based on accurate measurement of tracheal pressure. The purpose of this study was to test the validity of the DSA in a paediatric lung model and to apply the concept in an observational clinical study in children. METHODS: We validated the DSA in a paediatric lung model with linear, nonlinear pressure flow and frequency-dependent characteristics by comparing calculated dynostatic (alveolar) pressures with directly measured alveolar pressures in the model and proximal plateau pressure with maximum alveolar pressure. Sixty combinations of ventilation modes, positive end expiratory pressures, inspiratory : expiratory ratios, volumes and frequencies were studied. A 0.25-mm fibreoptic pressure transducer in the tube lumen was used in combination with volume and flow from ventilator signals. Clinical measurements were performed in eight patients during anaesthesia and postoperative ventilator treatment. RESULTS: In the lung model we found a correlation coefficient between calculated and measured alveolar pressure of 0.93-0.99 with root mean square median values of 1 cm H2O. Distal plateau pressure agreed well with maximum alveolar pressure. In the clinical situation, the algorithm provided a breath-by-breath display of the volume-dependent lung compliance and the temporal course of alveolar pressure during uninterrupted ventilation. CONCLUSIONS: Fibreoptic measurement of tracheal pressure in combination with the dynostatic calculation of alveolar pressure provides an on-line monitoring of the effects of ventilatory mode in terms of volume-dependent compliance, tracheal peak pressure and true positive end expiratory pressure.

Direct measurement of intratracheal pressure in pediatric respiratory monitoring.

We describe a method based on a Fabry-Perot interferometer at the tip of an optic fiber with a diameter of 0.25 mm for direct measurement of tracheal pressure in pediatric respiratory monitoring. The response time of the pressure transducer and its influence on the resistance of pediatric endotracheal tubes (internal diameter, 2.5 to 5 mm) during constant and dynamic flow at different ventilator settings in a lung model were measured. The transducer was positioned at -1.5 (inside), 0, and +1.5 cm (outside) relative to the tip of the endotracheal tube and compared with a reference pressure inside the trachea. The clinical application of the transducer was tested in five pediatric patients. The response time of the transducer was 1.3 ms. The influence of the fiberoptic transducer on tube resistance was negligible during constant flow in inspiratory and expiratory directions for all endotracheal tubes tested. There was no difference in pressure measurements with the transducer positioned at or 1.5 cm below or above the tip of the endotracheal tube during dynamic measurements. During clinical circumstances insertion of the fiberoptic transducer was easy, recordings were stable, and the safety of the patient was not jeopardized. The fiberoptic transducer provided a reliable and promising way of monitoring tracheal pressure in intubated pediatric patients. The presence of the probe did not interfere with either pressure-flow relationship or patient care and safety. The technique is proposed for monitoring of respiratory mechanics and calculation of changes in tube resistance caused by kinking and secretions.