Use of near-infrared spectroscopy for estimation of renal oxygenation in children with heart disease

We evaluated whether near-infrared spectroscopy (NIRS) measurement from the flank correlates with renal vein saturation in children undergoing cardiac catheterization. Thirty-seven patients <18 years of age were studied. A NIRS sensor was placed on the flank, and venous oxygen saturations were measured from the renal vein and the inferior vena cava (IVC). There was a strong correlation between flank NIRS values (rSO₂) and renal vein saturation (r = 0.821, p = 0.002) and IVC saturation (r = 0.638, p = 0.004) in children weighing ≤ 10 kg. In children weighing > 10 kg, there was no correlation between rSO₂ and renal vein saturation (r = 0.158, p = 0.57) or IVC saturation (r = –0.107, p = 0.67). Regional tissue oxygenation as measured by flank NIRS correlates well with both renal vein and IVC oxygen saturations in children weighing <10 kg undergoing cardiac catheterization, but not in larger children.     

Reversed differential cyanosis in the newborn: a clinical finding in the supracardiac total anomalous pulmonary venous connection

The newborn can experience two types of differential cyanosis (DC). The common type of DC occurs when oxygen saturation in the right hand is greater than in the foot. The second type of DC, reversed differential cyanosis (RDC), occurs when oxygen saturation is lower in the right hand than in the foot. This phenomenon is observed in transposition of the great arteries (TGA) with patent ductus arteriosis (PDA) and elevated pulmonary vascular resistance or in TGA with PDA and preductal aortic interruption or coarctation. This report describes a case of RDC not previously described involving an infant with supracardiac total anomalous pulmonary venous connection (TAPVC). In supracardiac TAPVC, RDC results from streaming of highly saturated superior vena cava (SVC) blood into the right ventricle, out the main pulmonary artery, through a PDA, and to the descending aorta, with streaming of more desaturated blood from the inferior vena cava (IVC) into the left atrium across the atrial septal defect (ASD)/foramen ovale. Therefore, as part of a neonatal examination to rule out congenital heart disease (CHD), simultaneous pre- and postductal oxygen saturations should be documented. The presence of RDC should initiate immediate full cardiac evaluation for CHD. Supracardiac TAPVC should be included in the differential diagnosis if RDC is observed.     

The relation between inferior vena cava oxygen saturation, superior vena cava flow, fractional oxygen extraction and haemoglobin affinity in sick newborns: a pilot study

AIM: To determine whether inferior vena cava oxygen saturation (UvO2) or lower-body fractional oxygen extraction (FOE) could detect poor cardiac output in newborns. METHODS: UvO2 and arterial oxygen saturation (SaO2) were measured simultaneously with echocardiographic determination of superior vena cava blood flow (SVC flow) at <12, 12-24 and >24 h. Haemoglobin concentration ([Hb]), haemoglobin oxygen affinity (HOA) and lactate were measured and FOE calculated. RESULTS: 56 studies in 17 infants, gestational age (median (range)) 26 wk 4 d (23 wk 2 d-42 wk 3 d): UvO2 (mean (SD)) was 84.9% (5.0), 77.6% (9.2) and 81.7% (12.9) at <12, 12-24 and >24 h, respectively; SVC flow (mean (SD)) increased from 71.7 (33) to 85 (66) and 123 (88) ml/kg/min at <12, 12-24 and >24 h, respectively. Despite a fall in mean [Hb], mean upper-body oxygen delivery increased due to increases in both SVC flow and arteriovenous content difference. There was a negative correlation between [Hb] and FOE. Infants with high HOA had significantly lower FOE. CONCLUSION: Measurement of UvO2 is feasible in newborns. Changes to SVC flow and arteriovenous content difference lead to improvements in oxygen delivery. The interaction of HOA warrants further study.     

Hemodynamic Correlates of Clinical Severity in isolated ventricular septal defect

Summary To test the hypothesis that the clinical assessment of severity in ventricular septal defect would be more related to variables which define tissue oxygen delivery than variables which define the left-to-right shunt, cardiac catheterization data from 40 children <3 years of age were assessed. Variables which were considered indicative of clinical severity included the need for digoxin and diuretics, resting heart rate, and severity of growth failure. Variables measured at cardiac catheterization, including those which related to oxygen transport, and assessment of left-to-right shunt, were considered independently. Patients receiving digoxin and diuretics were more tachycardic (142±18 vs. 111±26 beats/min, p<0.001) and had lower superior vena cava oxygen saturation (64±6 vs. 69±5%, p<0.01). Variation in heart rate (r ²=0.46) was best explained by oxygen consumption, hemoglobin concentration, cardiac index, and pulmonary vascular resistance. Variation in growth failure (r ²=0.15) was related only to the left ventricular forward stroke index. These data suggest that variables related to oxygen delivery, including oxygen consumption, hemoglobin concentration, cardiac index, forward stroke index, and superior vena cava oxygen saturation, are the major contributors to the clinical assessment of severity in ventricular septal defect.     

Effect of Fontan Fenestration on Regional Venous Oxygen Saturation During Exercise: Further Insights Into Fontan Fenestration Closure

Fontan fenestration closure is a topic of great debate. The body of data regarding the risks and benefits of fenestration closure is limited yet growing. Previous studies have demonstrated that Fontan patients have less exercise capacity than those with normal cardiovascular anatomy. Differences also have been noted within various subgroups of Fontan patients such as whether Fontan is fenestrated or not. This study aimed to compare trends in regional oxygen saturations using near-infrared spectroscopy (NIRS) in patients with Fontan circulations during ramping exercise to further delineate differences between patients with and without a fenestration. It was hypothesized that Fontan patients with fenestrations have better exercise times, higher absolute regional oxygen venous saturations, and smaller arteriovenous differences than Fontan patients without fenestrations. For this study, 50 consecutive Fontan patients and 51 consecutive patients with normal cardiovascular anatomy were recruited. Placement of NIRS probes was performed to obtain regional oxygen saturations from the brain and the kidney. Readings were obtained at 1-min intervals during rest, exercise, and recovery. A standard Bruce protocol was used with a 5-min recovery period. Absolute regional tissue oxygenation values (rSO₂) and arterial-venous oxygen saturation differences (AVDO₂) calculated as arterial oxygen saturation (SPO₂)—rSO₂ for normal versus Fontan patients and for fenestrated versus unfenestrated Fontan patients were compared using independent t tests. When normal and Fontan patients were compared, the Fontan patients had a significantly shorter duration of exercise (9.3 vs 13.2 min; p < 0.001). No statistically significant difference in rSO₂ change or AVDO₂ was evident at the time of peak exercise, at 2 min into the recovery, or at 5 min into the recovery. A small oxygen debt also was paid back to the brain in the Fontan patients after exercise, as evidenced by a narrower AVDO₂ than at baseline. The comparison of Fontan patients with and without fenestration showed no statistically significant difference in exercise time, rSO₂ change, or AVDO₂. The Fontan patients were noted to have shorter exercise times than the normal patients and also appeared to have an alteration in postexertional regional blood flow. However, when the various Fontan subtypes were compared by presence or absence of a fenestration, no significant differences were noted with regard to change in regional oxygen saturation or arteriovenous oxygen saturation. Thus, for patients with Fontan physiology, closure of the fenestration does not seem to have an impact on the dynamics of regional oxygen extraction during exercise or recovery.     

Upper Extremity Peripheral Venous Pressure Measurements Accurately Reflect Pulmonary Artery Pressures in Patients with Cavopulmonary or Fontan Connections

After the bidirectional cavopulmonary or Fontan operation, the physiologic consequence is passive flow of the systemic venous return to the pulmonary arteries. Knowledge of pulmonary artery pressure (PA) is valuable in the management of these patients, and obtaining this information without the need for a central line or cardiac catheterization would be advantageous. The aim of this study was to evaluate the correlation between upper extremity peripheral venous (PV) pressures and PA or superior vena cava (SVC) pressures in patients who have undergone cavopulmonary or Fontan connections. During cardiac catheterization, 19 patients with complex cyanotic heart disease who had undergone a cavopulmonary shunt or Fontan procedure were studied. Simultaneous pressure measurements were obtained from the peripheral intravenous line placed prior to the procedure and the SVC or PA. The mean pressures were compared. The mean PV pressure was 17.5 ± 5.6 mmHg. The mean SVC or PA pressure was 16.1 ± 5.4 mmHg. The mean difference was 1.5 ± 1.5 mmHg (p < 0.001). The correlation coefficient PV to SVC or PA pressure was 0.97 (p < 0.001). PV pressure measurements taken from an upper extremity accurately reflect PA pressures in patients who have undergone a cavopulmonary shunt or Fontan procedure.     

Does Treatment of Patent Ductus Arteriosus With Cyclooxygenase Inhibitors Affect Neonatal Regional Tissue Oxygenation?

The effect of patent ductus arteriosus (PDA) treatment with cyclooxygenase (COX) inhibitors (indomethacin [INDO] and ibuprofen [IBU]) on regional oxygenation requires further clarification. The authors hypothesized that both INDO and IBU reduce regional tissue oxygenation in preterm neonates with PDA but that the risk is not uniform for different tissues and other factors may contribute. Regional cerebral (rSO_2-C), renal (rSO_2-R), and mesenteric (rSO_2-M) tissue oxygenation measured by near-infrared spectroscopy and peripheral arterial oxygen saturation measured by pulse oximetry were recorded simultaneously before, during, and after treatment with the first dose of INDO or IBU in very preterm-born infants with PDA. Tissue-specific fractional oxygen extraction (FOE) was calculated using the rSO_2-C, rSO_2-R, rSO_2-M, and corresponding SpO₂ measurements. The findings showed a significant reduction in rSO_2-C, rSO_2-R, and rSO_2-M and an increase in regional FOE after treatment with COX inhibitors in approximately one third of the 38 enrolled infants, which were associated with increased baseline regional tissue oxygen saturation (p?<?0.01). However, the infants with posttreatment reduction of tissue oxygenation had significantly lower baseline rSO_2-C (66.7?±?8.1 vs 69.7?±?8.1?%), rSO_2-R (55.2?±?10.8 vs 62.7?±?11.8?%) and especially rSO_2-M (37.8?±?11.4 vs 46.7?±?16.0?%) than the neonates with unchanged or increased tissue oxygenation. The two groups did not differ in terms of the risk for posttreatment reduction in regional tissue oxygenation with respect to either INDO or IBU treatment and their respective blood levels. Treatment of PDA with either INDO or IBU is associated with a 30?C40?% risk for a reduction in regional tissue oxygenation, which is more pronounced in mesenteric tissue than in cerebral or renal tissue. Despite the inconsistency, reduction of regional tissue oxygenation in preterm infants with PDA is more likely associated with the administration of INDO than with the administration of IBU.     

Oxygen therapy in preterm infants: recommendations for practice

Oxygen is one of the most commonly used therapies in neonatology but optimum oxygen saturations for preterm infants have been debated for the past 50 years. The history of oxygen use in this population and multiple clinical trials over the years have shown that liberal oxygen administration is associated with retinopathy of prematurity (ROP) and bronchopulmonary dysplasia (BPD) whereas restrictive use results in increased mortality and neurodisability. Pulse oximetry (SpO₂) is a bedside tool to guide the fraction of inspired oxygen (FiO₂) delivered to the patient, and is the current standard of care for continuous monitoring. Although evidence favours targeting predetermined oxygen saturation ranges, achieving this goal consistently in clinical practice has been challenging due to intrinsic pulmonary immaturity, the need for respiratory support therapies and factors relating to the bedside caregivers ability to adjust FiO₂. This review article focuses on the difficulties of titrating oxygen therapy in this vulnerable group and provides recommendations for the best practice based on up to date evidence.     

Awake and asleep oxygen saturations in infants with chronic neonatal lung disease

Aim: There is uncertainty about the best method of withdrawing supplemental oxygen in babies with chronic neonatal lung disease (CNLD). Some authors advocate withdrawal of oxygen in the day, but continuing supplementation during sleep, based on early work suggesting that oxygen saturations are lower during sleep, which did not accord with our clinical impression. We re‐examined the hypothesis that babies have lower saturations while asleep. Methods: We studied infants with CNLD during the day, while awake and asleep. We recorded video with simultaneous real‐time capture of oxygen saturation (SpO₂), heart rate and plethysmographic waveform from pulse oximetry. Behavioural state was scored using observation and video and classified as awake (feeding, active or quiet) or sleep. Results: Thirteen infants had analysable data, although one had strikingly lower SpO₂ values while awake and was excluded from analysis. The infants had a median gestation of 26 weeks and were studied at a median (range) postmenstrual age of 66 (37–130) weeks, for 229 (89–330) min. Mean SpO₂ was 97.6% during sleep and 97.0% awake (p = 0.011). Conclusion: Babies with CNLD have lower oxygen saturation while awake. There is no physiological justification for increasing oxygen during sleep, or withdrawing selectively during the daytime, although larger studies are needed to confirm this finding.     

Splanchnic Near-Infrared Spectroscopy and Risk of Necrotizing Enterocolitis After Neonatal Heart Surgery

Infants with critical congenital heart disease, especially patients with a single-ventricle (SV) physiology, are at increased risk for the development of necrotizing enterocolitis (NEC). Decreased splanchnic oxygen delivery may contribute to the development of NEC and may be detected by regional oximetry (rSO₂) via splanchnic near-infrared spectroscopy (NIRS). This prospective study enrolled 64 neonates undergoing biventricular (BV) repair or SV palliation for CHD and monitored postoperative splanchnic rSO₂ before and during initiation of enteral feedings to determine whether changes in rSO₂ are associated with risk of NEC. Suspected or proven NEC was observed in 32 % (11/34) of the SV subjects and 0 % (0/30) of the BV subjects (p = 0.001). Compared with the BV subjects, the SV palliated subjects had significantly lower splanchnic rSO₂ before and during initiation of enteral feedings, but the groups showed no difference after correction for lower pulse oximetry (SpO₂) in the SV group. The clinical parameters were similar among the SV subjects with and without NEC except for cardiopulmonary bypass times, which were longer for the patients who experienced NEC (126 vs 85 min; p = 0.03). No difference was observed in splanchnic rSO₂ or in the SpO₂–rSO₂ difference between the SV subjects with and without NEC. Compared with the patients who had suspected or no NEC, the subjects with proven NEC had a lower average splanchnic rSO₂ (32.6 vs 47.0 %; p = 0.05), more time with rSO₂ less than 30 % (48.8 vs 6.7 %; p = 0.04) at one-fourth-volume feeds, and more time with SpO₂–rSO₂ exceeding 50 % (33.3 vs 0 %; p = 0.03) before feeds were initiated. These data suggest that splanchnic NIRS may be a useful tool for assessing risk of NEC, especially in patients with an SV physiology.     

Two molecular forms of adrenomedullin in congenital heart disease

To investigate the pathophysiological role of two forms of adrenomedullin (AM), a mature AM (AM-m) and a glycine-extended AM (AM-Gly), in congenital heart disease, we measured plasma levels of AM in patients with cyanotic heart disease, high pulmonary blood flow without pulmonary hypertension (PH), high pulmonary blood flow with PH, Fontan procedure, intracardiac repair without complication, and intracardiac repair with PH and control subjects. Plasma AM-m and AM-Gly were increased only for cyanotic heart disease (2. 5 ± 1.3 pmol/L, p < 0.001; 13.1 ± 6.2 pmol/L, p < 0.05) and intracardiac repair with PH (2.3 ± 1.5 pmol/L, p < 0.01; 13.0 ± 7.0 pmol/L, p < 0.05) compared with control (1.0 ± 1.4 and 8.6 ± 1.3 pmol/L, respectively). They were similarly correlated with mean systemic arterial pressure (r = –0.40 and –0.37 respectively; p < 0.001), mixed venous oxygen saturation (r = –0.60 and –0.50; p < 0.0001), systemic arterial oxygen saturation (SA_sat) (r = –0.56 and –0.46; p < 0.0001), and pulmonary arterial resistance (Rp) (r = 0.41 and 0.38; p < 0.005). Multiple regression analysis revealed that SA_sat and Rp were independently correlated with AM. Interestingly, the venous AM-m level was significantly higher than the arterial AM-m, suggesting that the mature form is extracted in pulmonary circulation, whereas there were no venoarterial differences in AM-Gly. These results suggest that plasma AM-m and AM-Gly are similarly regulated and the main clearance site of AM-m is the lung in patients with congenital heart disease.     

Cerebral Near-Infrared Spectroscopy Correlates to Vital Parameters During Cardiopulmonary Bypass Surgery in Children

Near-infrared spectroscopy (NIRS) can monitor changes in cerebral regional oxygen saturation (rSO₂) and tissue hemoglobin content (HbT). The relation between cerebral NIRS readings and vital parameters has not been analyzed before at a fine temporal scale. This study analyzed this relation during cardiopulmonary bypass (CPB) surgery in 10 children (0–9 years, 1,770 min of data records) by using a novel random-coefficient model. The analysis indicated that a small number of patients is sufficient for obtaining significant results with this model. Changes of vital parameters explained 84.7 % of rSO₂ changes and 90.7 % of HbT changes. Cerebral rSO₂ correlated positively with perfusion pressure and inversely with body temperature (P < 0.05). Cerebral HbT correlated positively with perfusion pressure, central venous pressure, and temperature and inversely with arterial oxygen saturation (P < 0.05). During hypothermic circulatory arrest, the half-life of the exponential rSO₂ decay correlated to the rSO₂ reserve (P = 0.016). In conclusion, NIRS readings of cerebral hemoglobin content and tissue oxygen saturation correlate well to vital parameters during CPB surgery in children. NIRS may therefore become a monitoring device for the neuroprotective optimization of those vital parameters.     

Neurophysiological Effects of Pediatric Balloon Dilatation Procedures

Balloon dilatation of valvar and vascular stenoses has become routine therapy in pediatric cardiology. Repeated balloon inflations cause many episodes of low cerebral oxygen delivery. This study is a prospective study to assess the effects of balloon dilatation on cerebral perfusion and oxygenation. The study included 11 patients scheduled for elective catheterization and balloon dilatation at a university pediatric hospital. Blood flow velocity in the middle cerebral artery (V _mca) and regional cerebral oxygen saturation (rSO₂) were monitored by means of transcranial Doppler sonography and near infrared spectroscopy, respectively. In group 1, consisting of 6 patients without an intracardiac shunt, inflation of the balloon resulted in a decrease in V _mca followed by a minor decrease in rSO₂. In group 2, consisting of 5 patients with an interatrial communication, inflation resulted in an increase in right-to-left shunt fraction, arterial desaturation, and a major decrease in rSO₂ with minor changes in V _mca. Balloon dilatation causes an important decrease in cerebral oxygen delivery by different mechanisms. This may lead to serious morbidity and even mortality. Neuromonitoring is a useful tool in assessing the cerebral effects of balloon dilatation and brain recovery.     

Comparison of vena cava distensibility index and pulse pressure variation for the evaluation of intravascular volume in critically ill children

ObjectiveIn this study, the authors aimed to evaluate the effectiveness of the vena cava distensibility index and pulse pressure variation as dynamic parameters for estimating intravascular volume in critically ill children.MethodsPatients aged 1 month to 18 years, who were hospitalized in the present study's pediatric intensive care unit, were included in the study. The patients were divided into two groups according to central venous pressure: hypovolemic (< 8 mmHg) and non-hypovolemic (central venous pressure ≥ 8 mmHg) groups. In both groups, vena cava distensibility index was measured using bedside ultrasound and pulse pressure variation. Measurements were recorded and evaluated under arterial monitoring.ResultsIn total, 19 (47.5%) of the 40 subjects included in the study were assigned to the central venous pressure ≥ 8 mmHg group, and 21 (52.5%) to the central venous pressure < 8 mmHg group. A moderate positive correlation was found between pulse pressure variation and vena cava distensibility index (r = 0.475, p < 0.01), while there were strong negative correlations of central venous pressure with pulse pressure variation and vena cava distensibility index (r = –0.628, p < 0.001 and r = –0.760, p < 0.001, respectively). In terms of predicting hypovolemia, the predictive power for vena cava distensibility index was > 16% (sensitivity, 90.5%; specificity, 94.7%) and that for pulse pressure variation was > 14% (sensitivity, 71.4%; specificity, 89.5%).ConclusionVena cava distensibility index has higher sensitivity and specificity than pulse pressure variation for estimating intravascular volume, along with the advantage of non-invasive bedside application.     

Persistent left superior vena cava: Experience of a tertiary health‐care center

Background: The aim of this study was to assess the prevalence of persistent left superior vena cava (PLSVC) in patients with all types of congenital heart defects and to determine the congenital heart anomalies accompanying PLSVC. Methods: The present study is based on a retrospective review of 1205 children who consecutively underwent cardiac catheterization from 2000 to 2007. In order to determine the existence of PLSVC, all the subjects routinely underwent superior vena cava (SVC) injection during angiography at the catheter laboratory of the study center. Results: The prevalence of PLSVC was computed to be 6.1% for the present study population. Transthoracic echocardiography was able to detect PLSVC in 32 children (2.6%) whereas angiography diagnosed PLSVC in 74 children (6.1%). The mean age of the patients with PLSVC was 40.09 ± 50.21 months. A communication between the right and left SVC was determined in 27% of the children who were diagnosed with PLSVC after angiography was performed (20 out of 74). A statistically significant association was present between PLSVC and other congenital cardiac anomalies, including ventricular septal defect (n= 42, 56.8%), atrial septal defect (n= 31, 41.9%), pulmonary stenosis (n= 19, 25.7%), atrioventricular septal defect (n= 10, 13.5%), patent ductus arteriosus (n= 6, 8.1%) and cor triatriatum (n= 3, 4.1%). Conclusion: Transthoracic echocardiography usually visualizes dilated coronary sinus in association with PLSVC. However, SVC injection should be performed in patients undergoing angiography so that morbidity and mortality related with persistent left superior vena cava can be avoided during cardiovascular surgery.     

Cerebral Near Infrared Spectroscopy Is a Reliable Marker of Systemic Perfusion in Awake Single Ventricle Children

Clinical assessment of systemic perfusion in single ventricle patients with parallel circulation can be difficult in the outpatient setting. Near infrared spectroscopy (NIRS) is a noninvasive measure of cerebral oximetry. We measured vital signs, pulse oximetry, and NIRS in 20 single ventricle patients with parallel circulation prior to routine cardiac catheterization. These variables were evaluated to determine the best noninvasive predictor of the superior vena cava saturation (SVC_sat) as a marker for the adequacy of systemic oxygen delivery. The mean age was 6.7 months [standard deviation (SD), 8.6] and mean weight was 6.5 kg (SD, 2.2). Diagnoses were hypoplastic left heart syndrome (8), tricuspid or pulmonary atresia (10), and double-outlet right ventricle variants (2), all prior to cavo pulmonary anastomoses or complete repairs. Stepwise multiple regression analysis generated a model in which only NIRS was a significant independent predictor of SVC_sat (p = 0.009). These results support the conclusion that NIRS can be a useful tool to evaluate awake single ventricle patients in the outpatient setting. Paper presented at the 55th annual scientific session of the American College of Cardiology, Atlanta, GA, USA, March 2006     

Bedside detection of low systemic flow in the very low birth weight infant on day 1 of life

We aimed to assess the relationship between the clinical and biochemical parameters of perfusion and superior vena cava (SVC) flow in a prospective observational cohort study of very low birth weight (VLBW) infants. Newborns with congenital heart disease were excluded. Echocardiographic evaluation of SVC flow was performed in the first 24 h of life. Capillary refill time (forehead, sternum and toe), mean blood pressure, urine output and serum lactate concentration were also measured simultaneously. Thirty-eight VLBW infants were examined. Eight patients (21%) had SVC flow less than 40 ml/kg/min. There was a poor correlation between the capillary refill time (in all sites), mean blood pressure, urine output and SVC flow. The correlation coefficient for the serum lactate concentration was r = −0.28, p = 0.15. The median serum lactate concentration was 3.5 (range 2.8–8.5) vs. 2.7 (range 1.2–6.9) mmol/l (p = 0.01) in low flow versus normal flow states. A serum lactate concentration of >2.8 was 100% sensitive and 60% specific for detecting a low flow state. Combining a capillary refill time of >4 s with a serum lactate concentration of >4 mmol/l had a specificity of 97% for detecting a low SVC flow state. Serum lactate concentrations are higher in low SVC flow states. A capillary refill time of >4 s combined with serum lactate concentrations >4 mmol/l increased the specificity and positive and negative predictive values of detecting a low SVC flow state.     

The Use of High-Resolution Computed Tomography in the Evaluation of Pulmonary Hemodynamics in Patients with Congenital Heart Disease: In Pulmonary Vessels Larger Than 1 mm in Diameter

High-resolution computed tomography (HRCT) was carried out in 36 patients with congenital left-to-right shunt disease and 10 normal control subjects to assess the feasibility of CT in the evaluation of pulmonary hemodynamics. The patients had a left-to-right or a bidirectional shunt and the hemodynamic data obtained by cardiac catheterization in these patients were compared to the information obtained by CT imaging. The pulmonary/systemic blood flow (Q _p/Q _s) ratio and pulmonic/systemic resistance (R _p/R _s) ratio had a significant correlation with the pulmonary artery/bronchus (PA/Br) ratio (r= 0.54 and r=−0.37, respectively) and pulmonary vein/bronchus (PV/Br) ratio (r= 0.66 and r=−0.66, respectively), and the R _p/R _s and mean PA pressure also showed a significant correlation with the PA/PV ratio (r= 0.53 and r=−0.61, respectively) in the mid-lung field when accompanying bronchi were 4.0–5.9 mm in diameter. There was no correlation between the hemodynamic data and the size of the central and hilar PA or with the rate of PA tapering. With HRCT, it is possible to evaluate pulmonary hemodynamics in patients with congenital heart disease with a left-to-right or bidirectional shunt, particularly R _p/R _s and mean PA pressure, which have been very difficult to obtain noninvasively. The small-sized pulmonary vessel/Br ratio or the small-sized PA/PV ratio could offer very useful information, but the dimension of the central PA provided the least useful information.     

Asthma and hemoglobinopathy: When is supplemental oxygen required?

Asthma is the most common reason for referral to the emergency department in childhood. In severe attacks, supplemental O₂ is given when oxygen saturation level is <90%. Described herein is the case of a child with persistent low oxygen saturation as measured on pulse oximetry (S_pO₂) after full clinical recovery from an asthma attack. Simultaneously, P_aO₂ was normal. A diagnosis of abnormal hemoglobin with decreased oxygen affinity (hemoglobin Seattle) was made on hemoglobin electrophoresis and genetic analysis. To ascertain when supplemental oxygen was needed, an oxygen dissociation curve was plotted using the tonometer technique, and it was found that an S_pO₂ of 70% is parallel to a P_aO₂ of 60 mmHg. Plotting an oxygen dissociation curve is a simple reproducible method to determine when supplemental oxygen is required for a child with a hemoglobinopathy.     

Comparison of blood gas values in arterial and venous blood

Objective : To compare pH and PCO₂ values of simultaneously obtained arterial, arterialized capillary, and venous blood samples and also to compare oxygen saturation (ASaO₂) measured in arterial blood and oxygen saturation by pulse oximetry (PSaO₂).Methods: Prospective study was done in the children admitted in the Pediatric Intensive Care Unit of Christian Medical College Hospital Vellore, requiring critical care. All the three blood gas samples (arterial, capillary and venous) were taken simultaneously and analyzed. Oxygen saturation by pulse oximetry was also recorded.Results: 50 children aged 14 days to 12 years were included in the study. Arterial and capillary pH values were highly correlated (r²=0.9024, p < 0.0001). Out of 16 children with arterial acidosis 9(56%) were identified by capillary blood gas. Arterial and venous pH values also showed good correlation (r²=0.8449, p eric 0.0001). The PCO₂ values of arterial and capillary blood gases were found to be highly correlated (r²=0.9534, p < 0.0001). The capillary blood gas accurately reflected the arterial PCO₂ in 41 (82%) patients. Arterial and venous blood gas PCO₂ values had less correlation (r²=0.5917, p=0.011). The arterial oxygen saturation (ASaO₂) and oxygen saturation by pulse oximetry (PSaO₂) were correlated moderately (r²=0.7241, p eric 0.0001).Conclusion: Even though arterial blood gas analysis is the gold standard, and when an arterial blood gas sample cannot be obtained, a combination of arterialized capillary blood gas and pulse oximetry can be effectively used in acutely ill children of all ages. Venous samples have a good correlation with arterial samples for pH but are not useful for monitoring blood gas status in acutely ill children.