Blood Gas Data Research Articles

Blood Gas, Oxygen Saturation, pH, and Lactate Values in Elasmobranch Blood Measured with a Commercially Available Portable Clinical Analyzer and Standard Laboratory Instruments

Blood gas, pH, and lactate data are often used to assess the physiological status and health of fish and can often be most valuable when blood samples are analyzed immediately after collection. Portable clinical analyzers allow these measurements to be made easily in the field. However, these instruments are designed for clinical use and thus process samples at 37 degrees C. A few studies have validated the use of portable clinical analyzers for assessing blood gases and acid-base profiles in teleosts, but equivalent data are not available for elasmobranchs. We therefore examined the relationship of blood gas, pH, and lactate values measured with an i-STAT portable clinical analyzer with those measured using standard laboratory blood gas (thermostatted to 25 degrees C) and lactate analyzers in samples taken from three species of carcharhiniform sharks. We found tight correlations (r2 > 0.90) between these methods for pH, pO2, pCO2, and lactate level values. We thus developed species-specific equations for converting blood values measured with an i-STAT portable clinical analyzer to those taken at 25 degrees C. Additional studies need to address a wider range of temperatures and elasmobranch species.

The Effects of Sleep Hypoxia on Coagulant Factors and Hepatic Inflammation in Emphysematous Rats

ObjectivesTo develop a sleep hypoxia (SH) in emphysema (SHE) rat model and to explore whether SHE results in more severe hepatic inflammation than emphysema alone and whether the inflammation changes levels of coagulant/anticoagulant factors synthesized in the liver.MethodsSeventy-five rats were put into 5 groups: SH control (SHCtrl), treated with sham smoke exposure (16 weeks) and SH exposure (12.5% O2, 3 h/d, latter 8 weeks); emphysema control (ECtrl), smoke exposure and sham SH exposure (21% O2); short SHE (SHEShort), smoke exposure and short SH exposure (1.5 h/d); mild SHE (SHEMild), smoke exposure and mild SH exposure (15% O2); standard SHE (SHEStand), smoke exposure and SH exposure. Therefore, ECtrl, SHEShort, SHEMild and SHEStand group were among emphysematous groups. Arterial blood gas (ABG) data was obtained during preliminary tests. After exposure, hepatic inflammation (interleukin -6 [IL-6] mRNA and protein, tumor necrosis factor α [TNFα] mRNA and protein) and liver coagulant/anticoagulant factors (antithrombin [AT], fibrinogen [FIB] and Factor VIII [F VIII]) were evaluated. SPSS 11.5 software was used for statistical analysis.ResultsCharacteristics of emphysema were obvious in emphysematous groups and ABGs reached SH criteria on hypoxia exposure. Hepatic inflammation parameters and coagulant factors are the lowest in SHCtrl and the highest in SHEStand while AT is the highest in SHCtrl and the lowest in SHEStand. Inflammatory cytokines of liver correlate well with coagulant factors positively and with AT negatively.ConclusionsWhen SH is combined with emphysema, hepatic inflammation and coagulability enhance each other synergistically and produce a more significant liver-derivative inflammatory and prothrombotic status.

Clinicians’ response to hyperoxia in ventilated patients in a Dutch ICU depends on the level of FiO2

PurposeHyperoxia may induce pulmonary injury and may increase oxidative stress. In this retrospective database study we aimed to evaluate the response to hyperoxia by intensivists in a Dutch academic intensive care unit.MethodsAll arterial blood gas (ABG) data from mechanically ventilated patients from 2005 until 2009 were extracted from an electronic storage database of a mixed 32-bed intensive care unit in a university hospital in Amsterdam. Mechanical ventilation settings at the time of the ABG tests were retrieved.ResultsThe results of 126,778 ABG tests from 5,498 mechanically ventilated patients were retrieved including corresponding ventilator settings. In 28,222 (22%) of the ABG tests the arterial oxygen tension (PaO2) was >16 kPa (120 mmHg). In only 25% of the tests with PaO2 >16 kPa (120 mmHg) was the fraction of inspired oxygen (FiO2) decreased. Hyperoxia was accepted without adjustment in ventilator settings if FiO2 was 0.4 or lower.ConclusionHyperoxia is frequently seen but in most cases does not lead to adjustment of ventilator settings if FiO2 <0.41. Implementation of guidelines concerning oxygen therapy should be improved and further research is needed concerning the effects of frequently encountered hyperoxia.

Treatment with the C5a receptor antagonist ADC-1004 reduces myocardial infarction in a porcine ischemia-reperfusion model

BackgroundPolymorphonuclear neutrophils, stimulated by the activated complement factor C5a, have been implicated in cardiac ischemia/reperfusion injury. ADC-1004 is a competitive C5a receptor antagonist that has been shown to inhibit complement related neutrophil activation. ADC-1004 shields the neutrophils from C5a activation before they enter the reperfused area, which could be a mechanistic advantage compared to previous C5a directed reperfusion therapies. We investigated if treatment with ADC-1004, according to a clinically applicable protocol, would reduce infarct size and microvascular obstruction in a large animal myocardial infarct model.MethodsIn anesthetized pigs (42-53 kg), a percutaneous coronary intervention balloon was inflated in the left anterior descending artery for 40 minutes, followed by 4 hours of reperfusion. Twenty minutes after balloon inflation the pigs were randomized to an intravenous bolus administration of ADC-1004 (175 mg, n = 8) or saline (9 mg/ml, n = 8). Area at risk (AAR) was evaluated by ex vivo SPECT. Infarct size and microvascular obstruction were evaluated by ex vivo MRI. The observers were blinded to the treatment at randomization and analysis.ResultsADC-1004 treatment reduced infarct size by 21% (ADC-1004: 58.3 ± 3.4 vs control: 74.1 ± 2.9%AAR, p = 0.007). Microvascular obstruction was similar between the groups (ADC-1004: 2.2 ± 1.2 vs control: 5.3 ± 2.5%AAR, p = 0.23). The mean plasma concentration of ADC-1004 was 83 ± 8 nM at sacrifice. There were no significant differences between the groups with respect to heart rate, mean arterial pressure, cardiac output and blood-gas data.ConclusionsADC-1004 treatment reduces myocardial ischemia-reperfusion injury and represents a novel treatment strategy of myocardial infarct with potential clinical applicability.

Lung Recruitment and Positive End-Expiratory Pressure Have Different Effects on CO2 Elimination in Healthy and Sick Lungs

We studied the effects that the lung recruitment maneuver (RM) and positive end-expiratory pressure (PEEP) have on the elimination of CO(2) per breath (Vtco(2,br)). In 7 healthy and 7 lung-lavaged pigs at constant ventilation, PEEP was increased from 0 to 18 cm H(2)O and then decreased to 0 in steps of 6 cm H(2)O every 10 minutes. Cycling RMs with plateau pressure/PEEP of 40/20 (healthy) and 50/25 (lavaged) cm H(2)O were applied for 2 minutes between 18-PEEP steps. Volumetric capnography, respiratory mechanics, blood gas, and hemodynamic data were recorded. In healthy lungs before the RM, Vtco(2,br) was inversely proportional to PEEP decreasing from 4.0 (3.6-4.4) mL (median and interquartile range) at 0-PEEP to 3.1 (2.8-3.4) mL at 18-PEEP (P < 0.05). After the RM, Vtco(2,br) increased from 3.3 (3-3.6) mL at 18-PEEP to 4.0 (3.5-4.5) mL at 0-PEEP (P < 0.05). In lavaged lungs before the RM, Vtco(2,br) increased initially from 2.0 (1.7-2.3) mL at 0-PEEP to 2.6 (2.2-3) mL at 12-PEEP (P < 0.05) but then decreased to 2.4 (2-2.8) mL when PEEP was increased further to 18 cm H(2)O (P < 0.05). After the RM, the highest Vtco(2,br) of 2.9 (2.1-3.7) mL was observed at 12-PEEP and then decreased to 2.5 (1.9-3.1) mL at 0-PEEP (P < 0.05). Vtco(2,br) was directly related to changes in lung perfusion, the area of gas exchange, and alveolar ventilation but inversely related to changes in dead space. CO(2) elimination by the lungs was dependent on PEEP and recruitment and showed major differences between healthy and lavaged lungs.

Prediction of respiratory failure in late-preterm infants with respiratory distress at birth

The aim of this study was to evaluate indices of respiratory failure in terms of their ability to predict respiratory impairment and need for ventilatory support in late-preterm neonates with respiratory distress. Arterial blood gas data during the first 12 postnatal hours or until intubation were recorded in 155 neonates with gestational age 34(0/7)-36(6/7) weeks admitted in the NICU with respiratory distress between January 2006 and June 2008. Alveolar-arterial oxygen tension difference (A-aDO(2)), arterial to alveolar oxygen tension ratio (a/A ratio), and partial arterial oxygen tension to inspired oxygen fraction ratio (PaO(2)/FiO(2)) were calculated. Considering the worst single value of each parameter, receiver operating characteristic curve analyses and area under the curve (AUC) comparisons were used to evaluate their predictive performance. Fifty-five neonates (35.5%) required mechanical ventilation. The predictive performances of the maximum A-aDO(2) (AUC 0.97), minimum a/A ratio (AUC 0.95), and minimum PaO(2)/FiO(2) (AUC 0.95) were similar. The A-aDO(2) at a threshold of >200 mmHg proved to be more effective than the other parameters, having excellent positive and negative likelihood ratios of 24.5 and 0.02, respectively. This threshold was achieved by 98.25% of the neonates who developed respiratory failure at a median of 3 h before the ventilatory support to be definitely decided. Composite indices, such as A-aDO(2), a/A ratio, and PaO(2)/FiO(2), can reasonably predict respiratory failure in late-preterm neonates with respiratory distress, allowing for closer monitoring, early medical intervention, or transfer to a level III neonatal unit.

Transient phrenic nerve paralysis after carotid endarterectomy in a patient with asthma

To the Editor: Transient phrenic nerve paralysis occurred in a patient with asthma after carotid endarterectomy (CEA). The patient, a 64-year-old male with a height of 164 cm and weight of 69 kg, had been suffering from asthma for 15 years for which he was taking 400 mg of theophylline daily. A respiratory examination showed a reduced percentage forced expiratory volume in 1 second (%FEV1.0: 61.2%), and he was assigned to class II in Hugh–Jone’s classification. The patient was scheduled for CEA due to cerebral infarction with left lower extremity paralysis and transient dizziness 1 year earlier. With respect to the patient’s positioning during surgery, the anterior edge of the skin on the sternocleidomastoid muscle was located at the highest point by placing a shoulder pillow under the right shoulder in the supine position and rotating the head 30 to the left side; the jaw was tracted in the cephalic direction and the right shoulder was also tracted in the caudal direction. Anesthetic management was performed without difficulty for 4 h and 2 min, and surgery was completed without complications in 2 h and 43 min. Since the neurosurgeons were concerned about possible respiratory disorders, such as atelectasis, due to the patient’s asthma and wanted to ensure that there was no problem, they requested an X-ray before extubation. The post-operative X-ray revealed right diaphragm elevation at the end-inspiratory phase during spontaneous breathing (Fig. 1). Since there were no problems in emergence from anesthesia or in respiratory functions, such as blood gas data or respiratory pattern or tidal volume, extubation was attempted in the sitting position. There was also no respiratory disorder after extubation. Diaphragm elevation was improved the next day. Post-operative transient phrenic nerve paralyses mainly occur after cardiac surgery due to direct injury or hypothermia, mainly on the left side, and can be caused after other surgery due to traction or compression caused by the patient’s position [1, 2]. Unilateral diaphragmatic paralysis in adults generally has minimal symptoms or no symptoms, but bilateral or unilateral diaphragmatic paralysis in children can cause serious medical problems [1, 3]. The cause in the patient described here is thought to be traction by the head position. Although extubation was performed in the sitting position because of the possibility of respiratory disorder caused by unilateral phrenic nerve paralysis with asthma, there was no problem in the respiratory system after extubation. In the present case, a post-operative X-ray, which was taken because the patient had asthma, revealed, by chance, transient phrenic nerve paralysis. However, X-rays are not standard procedures following CEA in many institutions. Presented at the Annual Meeting of the Japan Society for Clinical Anesthesia, Osaka, October 24, 2004.

Caudwell Xtreme Everest Expedition

The Caudwell Xtreme Everest (CXE) expedition involved the detailed study of 222 subjects ascending to 5300 m or higher during the first half of 2007. Following baseline measurements at sea level, 198 trekker-subjects trekked to Everest Base Camp (EBC) following an identical ascent profile. An additional group of 24 investigator-subjects followed a similar ascent to EBC and remained there for the duration of the expedition, with a subgroup of 14 collecting data higher on Everest. This article focuses on published data obtained by the investigator-subjects at extreme altitude (>5500 m). Unique measurements of peak oxygen consumption, middle cerebral artery diameter and blood velocity, and microcirculatory blood flow were made on the South Col (7950 m). Unique arterial blood gas values were obtained from 4 subjects at 8400 m during descent from the summit of Everest. Arterial blood gas and microcirculatory blood flow data are discussed in detail.

Blood cells and serum chemistry in the world’s largest fish: the whale shark Rhincodon typus

Descriptive information regarding the peripheral blood of normal whale sharks Rhin- codon typus Smith 1828 is presented based on samples collected from 2 healthy female specimens held in an aquarium collection. Erythrocyte morphology was similar to other orectolobiforms and major leukocyte types were similar to other non-carcharhinid sharks. The numerically dominant pop- ulation was the lymphocyte (46%), followed by the fine eosinophilic granulocyte or heterophil (39.5%). The remaining 15% of white blood cells were divided among coarse eosinophilic granulo- cytes or eosinophils, simple neutrophils, monocytes similar to those of most elasmobranchs and a rare basophilic stippled granulocyte or basophil. Thrombocytes were similar to those of other shark spe- cies; no granulated thrombocytes were observed in this species. Blood gas data and serum chemistry values are also presented. For comparison, 22 blood samples collected from 2 moribund male speci- mens showed that the heterophil/lymphocyte ratio may be a potentially useful biomarker of whale shark health. A pattern of marked heterophilia in these animals became more pronounced as their clinical condition deteriorated. These data represent the first exploration of the internal biology of the world's largest fish.

Effects of vaporized perfluorocarbon therapy on seawater respiratory distress syndrome in rabbit models

To investigate the effects of vaporized perfluorocarbon therapy on pulmonary gas exchange and lung compliance in seawater respiratory distress syndrome rabbit models. After induction of seawater respiratory distress syndrome by means of intratracheal injection of seawater, 24 female New Zealand rabbits were randomly divided into 3 groups: (1) CMV group (n = 8): Animals were ventilated with equal tidal volumes of 8 ml/kg during gas ventilation for 6 h. (2) PFC group (n = 8): For the first 2 h, animals received vaporized PFC with volumes of 6 - 7 mlxkg(-1)xh(-1), followed by gas ventilation for 4 h. (3) control group (n = 8): No ventilation was administered. Physiological and blood gas data were compared among the 3 groups by analysis of variance. The right lung of each animal was cut into 2 or 3 slides which were fixed with 10% buffered formalin for pathological evaluation. After lung injury, the measurements of lung compliance and oxygenation became significantly worse. After vaporized PFC for 30 min, lung compliance and oxygenation improved significantly as compared to the CMV group [(2 +/- 1) mm Hg/cm H2O vs (1 +/- 0) mm Hg/cm H2O (1 mm Hg = 0.133 kPa, 1 cm H2O = 0.098 kPa), F = 20, P < 0.05; (158 +/- 65) mm Hg vs (74 +/- 12) mm Hg, F = 26, P < 0.05]. After PFC inhalation, the improvement of oxygenation in PFC group lasted for 4 h [(253 +/- 96) mm Hg vs (78 +/- 19) mm Hg, F = 15, P < 0.05]. The lung injury score was also decreased in the PFC group compared to the CMV group (6.9 +/- 1.6 vs 9.8 +/- 1.3, chi(2) = 22, P < 0.05). All animals in the control group died in 15 min without ventilation. Vaporized PFC improved oxygenation and lung compliance and attenuated lung injury in a rat model of seawater induced respiratory distress syndrome.

Blood gas changes in Duchenne type muscular dystrophy

We studied changes in blood gas data from 32 patients with Duchenne type muscular dystrophy (DMD), who were followed for more than 5 years. Regression lines for each blood gas variable were obtained by the least square regression method, from 276 observations. The mean change per year was calculated by averaging the individual slopes. All blood gas variables (PaO2, PaCO2, pH, and [HCO3-]) correlated significantly with age the regression lines were: PaO2 = 95.6-0.45x Age, PaCO2 = 34.7 + 0.70x Age, pH = 7.397-0.0023x Age, [HCO3-] = 20.7 + 0.28x Age. The rates of change were -0.74 Torr/year for PaO2, 1.07 Torr/year for PaCO2, -0.0028 per year for pH and 0.55 mEq/l/year for [HCO3-]. The slope of each regression line was within the average individual yearly change +/- one standard deviation. AaDO2 did not change significantly with age, but chronic respiratory acidosis worsened because of alveolar hypoventilation. As an index of the severity of DMD, PaCO2 was better than PaO2, because the former was more strongly correlated with age and the values of PaCO2 deviated less from the the regression line.

Relationship between clinical symptoms and nocturnal oxygen desaturation in sleep apnea syndrome and chronic lung disease

Nocturnal oxygen desaturation (NOD) is commonly seen not only in sleep apnea syndrome (SAS) but also in chronic lung disease (CLD) including chronic obstructive lung disease even without sleep apnea. However, the relationship of NOD to clinical symptoms such as morning headache, sleep deprivation due to breathlessness, and daytime sleepiness is not known. In this study, we examined by polysomnography the relationship between several NOD indexes, parameters of apnea, and subjective symptoms in 25 patients with SAS and 22 patients with CLD. In addition, the relation between daytime arterial blood gas data and NOD indexes, parameters of apnea, was examined. In the SAS group, there were no differences in any parameters of NOD and apnea between patients with subjective symptoms and those without symptoms. However, in the CLD group, symptomatic patients had significantly lower lowest SaO2, higher mean SaO2, and longer total desaturation time. In both groups, daytime PaCO2 had a significant correlation with several NOD parameters such as mean SaO2, lowest SaO2, and total desaturation time. In the SAS group, daytime PaCO2 was also correlated with the parameters of apnea. On the other hand, daytime PaO2 was significantly correlated with mean SaO2 only in the CLD group. From these data, we conclude that in patients with SAS, daytime PaCO2 is a variable that is related to the degree of NOD, and that in patients with CLD, subjective symptoms and daytime PaO2 in addition to daytime PaCO2 are associated with NOD.

Predictors of survival in congenital diaphragmatic hernia patients requiring extracorporeal membrane oxygenation: CNMC 15-year experience

To review outcomes of patients with congenital diaphragmatic hernia (CDH) requiring extracorporeal membrane oxygenation (ECMO) at a level IIIC neonatal intensive care unit and to determine if pre-ECMO respiratory status can help predict mortality. A single-center retrospective chart review was conducted on all infants with CDH treated with ECMO in the past 15 years. Demographic and clinical information, including pre-ECMO ventilatory and blood gas data, was collected. Differences between survivors and non-survivors were evaluated using independent samples t-/Mann-Whitney U-and Fisher's exact/chi (2)-tests for continuous and categorical data, respectively. Cox regression analysis was performed to evaluate predictors of survival while controlling for covariates. Significant predictors were further explored with receiver operating characteristic (ROC) curve and Kaplan-Meier survival analysis. Overall survival of the population of 62 patients treated with ECMO was 50%. Survivor and non-survivors were similar in birth weight, gestational age, gender, race and Apgar scores. Approximately 80% of patients in both groups had a left-sided defect. Less than half of patients were prenatally diagnosed in either group. Patients in the non-survivor group had associated anomalies (42 vs 23% for survivors) but this was not statistically significant (P=0.303). Non-survivors were more likely to be put on ECMO earlier, stay on ECMO longer and be operated upon later. On pre-ECMO blood gas analyses, survivors had higher pH and PaO(2), and lower oxygenation index and PaCO(2) compared with non-survivors. After controlling for covariates, a lower minimum PaCO(2) and side of defect were the only independent predictors of survival. ROC curve for minimum pre-ECMO PaCO(2) had a significant area under the curve (0.72, P=0.003). Survival was 27% in babies unable to achieve a pre-ECMO PaCO(2) <60 mm Hg whereas no patients survived if their lowest pre-ECMO PaCO(2) was >70 mm Hg. Minimum achievable pre-ECMO PaCO(2) is an independent predictor of survival in patients with CDH requiring ECMO life support. These data provide useful prognostic information for counseling families and may facilitate direction of care in extreme cases where the degree of pulmonary hypoplasia may be incompatible with life.

Ventilation and Haemodynamic Indicators in Spontaneously Breathing Pigs under General Anaesthesia

The aim of this study was to obtain ventilation and haemodynamic data of healthy piglets under general anaesthesia for future patho-physiological experimental studies. A total of 34 domestic piglets of the Czech Black Pied (Přeštice) breed were used in the study. The animals (male to female ratio 8 : 9) were six weeks old and their average body mass was 22 kg. A general anaesthetic (fentanyl and azaperon) was introduced via a pulmonary artery catheter and the spontaneously breathing animals were monitored for 60 min. Cardiac output and haemodynamic indicators were established using intermittent pulmonary artery thermodilution. Blood gas data were deduced using fan dynamic parameters of ventilation and ventilation indices. The study yielded reliable data of dynamic lung indicators (p &lt; 0.05); e.g. the tidal volume 6.00 ± 0.82 ml/kg, hypoxemic index 350.47 ± 42.50 mmHg, lung compliance 0.63 ± 0.12 ml/cmH2O/kg, and haemodynamic indicators (p &lt; 0.01) such as cardiac output 2.12 ± 0.75 l/min, pulmonary vascular resistance 3.92 ± 0.52 and systemic vascular resistance 15.8 ± 6.81 Woods units. Reliable data regarding lung dynamics, cardiac output, preload and afterload of both heart ventricles in spontaneously breathing healthy piglets under general anaesthesia were achieved.

Early prediction of septic shock in hospitalized patients

Hospitalized patients who develop severe sepsis have significant morbidity and mortality. Early goal-directed therapy has been shown to decrease mortality in severe sepsis and septic shock, though a delay in recognizing impending sepsis often precludes this intervention. To identify early predictors of septic shock among hospitalized non-intensive care unit (ICU) medical patients. Retrospective cohort analysis. A 1200-bed academic medical center. Derivation cohort consisted of 13,785 patients hospitalized during 2005. The validation cohorts consisted of 13,737 patients during 2006 and 13,937 patients from 2007. Development and prospective validation of a prediction model using Recursive Partitioning And Regression Tree (RPART) analysis. RPART analysis of routine laboratory and hemodynamic variables from the derivation cohort to identify predictors prior to the occurrence of shock. Two models were generated, 1 including arterial blood gas (ABG) data and 1 without. When applied to the 2006 cohort, 347 (54.7%) and 121 (19.1%) of the 635 patients developing septic shock were correctly identified by the 2 models, respectively. For the 2007 patients, the 2 models correctly identified 367 (55.0%) and 102 (15.3%) of the 667 patients developing septic shock, respectively. Readily available data can be employed to predict non-ICU patients who develop septic shock several hours prior to ICU admission.

Avoidance of Reintubation by Using Sedation during Noninvasive Positive Pressure Ventilation in a 3-Month-Old Infant with Postoperative Respiratory Failure

Maintaining alertness during noninvasive positive pressure ventilation (NPPV) is important, but there are no established guidelines for the use of sedation. We report our first experience of an infant with post-surgical vocal cord paralysis, severe stridor and breathing difficulties, who was reintubated after NPPV treatment without sedation, but who avoided a third reintubation through the use of sedation with the second NPPV treatment. NPPV treatment with the proper sedation can improve blood gas data in those patients with severe dyspnea, which can occur during respiratory care in several situations, and can affect not only infants, but also adults including elderly patients.

Does Biventricular Pacing Improve Hemodynamics in Children Undergoing Routine Congenital Heart Surgery?

Biventricular (BiV) pacing or cardiac resynchronization therapy (CRT) is an established therapy for heart failure in adults. In children, cardiac dyssynchrony occurs most commonly following repair of congenital heart disease (CHD) where multisite pacing has been shown to improve both hemodynamics and ventricular function. Determining which patient types would specifically benefit has not yet been established. A prospective, repeated measures design was undertaken to evaluate BiV pacing in a cohort of children undergoing biventricular repair for correction of their CHD. Hemodynamics, arterial blood gas, electrocardiographic (ECG), and echocardiographic data were collected. Pacing protocol was undertaken prior to the patient's extubation with 20 min of conventional right ventricular (RV) or BiV pacing, preceded and followed by 10 min of recovery time. Multivariate statistics were used to analyze the data with p values <0.05 considered significant. Twenty-five (14 female) patients underwent surgery at a median (range) age of 5.2 (0.1-37.4) months with no early mortality. The Risk-adjusted classification for Congenital Heart Surgery (RACHS) scores were 2 in 14 patients, 3 in eight patients, and 4 in three patients. None had pre-existing arrhythmias, dyssynchrony, or required pacing pre-operatively. No patient required implantation of a permanent pacemaker post-operatively. The median cardio-pulmonary bypass time was 96 (55-236) min. RV and BiV pacing did not improve cardiac index from baseline (3.23 vs. 3.42 vs. 3.39 L/min/m2; p > 0.05). The QRS duration was not changed with pacing (100 vs. 80 vs. 80 ms; p > 0.05). On echocardiography, the time-to-peak velocity difference between the septal and posterior walls (synchrony) during pacing was similar to baseline and was also not statistically significant. BiV pacing did not improve cardiac output when compared to intrinsic sinus rhythm or RV pacing in this cohort of patients. Our study has shown that BiV pacing is not indicated in children who have undergone routine BiV congenital heart surgery. Further prospective studies are needed to assess the role of multisite pacing in children with ventricular dyssynchrony such as those with single ventricles, those undergoing reoperation or those with high RACHS scores.

Cyanide poisoning in Taiwan

In May, 2005, a 32-year-old woman lost consciousness soon after drinking a non-alcoholic beverage. She was transported to hospital within 5 min, found to be unresponsive, and intubated. Before intubation, blood gas measurements on room air (possible venous sample), were: pH 7·846, pCO2 24·2 mm Hg, pO2 28·7 mm Hg, HCO3 41·8 mmol/L (base excess [BE] 26 mmol/L); O2 saturation was 79·4%. The beverage had a pH of 9; a working diagnosis of alkaline corrosive injury was made, and she was transferred to our emergency unit. When seen by us, about 1 h after poisoning, her blood pressure was 85/46 mm Hg, despite norepinephrine 8 μg/min; blood gases (on ventilator with 100% oxygen; O2 saturation 100%) pointed to metabolic acidosis: pH 7·096, pCO2 17·2 mm Hg, pO2 385 mm Hg, HCO3 5·4 mmol/L (BE –21·7 mmol/L); blood lactate concentration was 14 mmol/L. The anion gap was 37·6 mmol/L. Cyanide (CN) poisoning was suspected and 2·5 g intravenous hydroxocobalamine was given. Our patient showed signs of improvement 2–3 min after antidote, but a second dose was given 1 h later because of persistent severe metabolic acidosis. She continued to improve, regained consciousness, and was extubated the next morning. Her blood CN concentration on transfer to us was 288·6 μmol/L; her drink had been laced with 1·9% (fi nal concentration in the beverage) potassium cyanide (KCN). The patient was discharged 10 days later; when last seen in 2007, she was well. On May 17, 2005, over ten bottles of a non-alcoholic beverage were spiked with KCN in various convenience stores in Taiwan. Our patient was the fi rst of three people who were poisoned and who collapsed soon after consuming a small amount of the drink. Blood gas data are shown in the fi gure. Even accounting for the change in CO2 as a result of respiratory compensation, and the possible venous sample, the large change in HCO3 from A to B is probably due to huge acid production —typical of CN poisoning. The initial alkalosis seen in our patient could have been due to various factors. The pKa of KCN is 9·21 at 25°C. When it is given orally, the gastric acid environment favours formation of the unionised form of HCN and facilitates HCN absorption across the gastrointestinal mucosa. Initially, the absorbed HCN, particularly with smaller doses, stimulates central nervous system driven hyperventilation, leading to respiratory alkalosis (supported by blood gas data from the second case—not shown). In a pure respiratory alkalosis, we would have expected our patient’s blood pCO2 to be less than 10 mm Hg, given that pH was 7·846. It is possible that HCO3 formation in the stomach could have contributed to our patient’s initially raised blood pCO2. In the stomach, HCl is depleted in gastric secretions because it reacts with KCN. Each mmol of H secreted will generate 1 mmol of HCO3, leading to a transient increase in plasma HCO3. In KCN ingestion, there is no stimulus for HCO3 secretion in the duodenum because of gastric acid depletion and quick absorption of HCN. The net result is an increase in plasma HCO3 concentration. Severe metabolic acidosis, with raised lactate, occurred quickly, because KCN inhibits the electron transport chain and anaerobic respiration. Hydroxocobalamine 5–10 g is the recommended treatment. We gave our patient an initial dose of 2·5 g hydroxocobalamine because of the potential for mass casualties and low stores of antidote. Only prompt diagnosis and antidote can resolve severe CN poisoning.

Vasodilatory effect of adenosine triphosphate does not change cerebral blood flow: a PET study with 15O-water

Adenosine triphosphate (ATP) is the parent compound of adenosine and well known as a powerful vasodilator. To investigate the effect of ATP on cerebral blood flow (CBF) and cerebral vessels, (15)O-water positron emission tomography (PET) studies were performed to evaluate changes in CBF and blood volume before and after ATP administration. Ten healthy young volunteers underwent (15)O-water PET scans under the conditions of baseline, 3 and 1 min after ATP continuous infusion. CBF values in cortical regions of the bilateral middle cerebral arteries and basal ganglia were obtained for each subject. Statistical parametric mapping (SPM) was applied for analysis of regional changes. Physiologic parameters, such as blood gas and blood pressure were also measured. Cortical CBF showed no significant change after continuous infusion of ATP compared with the baseline. Dilatation of major vessels induced by ATP was visualized on SPM analysis. Heart rates increased and mean blood pressure decreased during ATP administration while blood gas data showed no changes between the different conditions. Intravenous ATP administration caused dilatation of major cerebral vessels but no significant change in CBF under normoventilation and decrease in systemic blood pressure, indicating that this no change in CBF under vasodilatory effect of ATP may be caused by cerebral microvascular autoregulation.

Acid-base variables in patients with acute kidney injury requiring peritoneal dialysis in the pediatric cardiac care unit

We aimed to clarify the acid-base abnormalities of patients with acute kidney injury (AKI) requiring peritoneal dialysis (PD) in pediatric cardiac care units. A retrospective observational study was conducted in a pediatric cardiac care unit in a tertiary care university hospital. The subjects were 40 patients with AKI requiring PD between 2003 and 2005, and controls matched by type of surgery and body weight. Acid-base variables, including blood gas data and electrolytes, were assessed. The Stewart-Figge variables, including strong ion difference apparent (SIDa), strong ion difference effective (SIDe), and strong ion gap (SIG), were calculated. Blood gas analyses showed that the PD group was more acidemic, with a lower mean bicarbonate and a lower mean base excess, typical features of metabolic acidosis. The strong ion analyses revealed that the PD group had lower mean sodium and albumin concentrations. Based on the Stewart-Figge methodology, SIDa was smaller in the PD group than in the control group, but SIG was similar in the two groups. Receiver-operating characteristic curve analyses showed that serum albumin was the only prognostic factor associated with PCCU mortality, even after adjustment for PD treatment. Patients with AKI requiring PD in a pediatric cardiac care unit had significant metabolic acidosis compared to controls matched by the type of surgery and body weight. Hyponatremia and hypoalbuminemia were characteristics of these patients. The calculated SIDa was smaller in the PD than in the control group. Only the serum albumin had a significant prognostic value.