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Effects of fetal haemoglobin on the NIR analysis of neonatal cerebral oxygenation
86 Owing to abdominal or thoracic surgery all of them needed general anesthesia. We have used the muscle relaxant tracurium besylate in all patients. The nitrous oxide requirement was minimal and temporary in eight babies. At the end of surgery flumazenil and naloxone was administered to antagonise the effects of the anesthetics. No clinically significant side effect was observed during or after anesthesia. Adequate monitoring of respiratory function is necessary because of the possibility of apnoea.
Respiratory fimction at follow-up after neonatal surf&ant replacement therapy. B. Yuksel, A. Greenough and H.R. Gamsu, Department of Child Health, King’s College Hospital, London SE5 9RS (UK) Respiratory function was assessed at a median of 7 months (range 6-12) in 17 preterm infants who, in the neonatal period, had been entered into a multi-centre randomised placebo-controlled trial of surfactant replacement therapy with synthetic surfactant (Exosurf). Seven infants (median gestational age 28 weeks (range 26-23) and birthweight 1135 g (730-l 164) received surfactant and the remaining 10 infants (median gestational age 27 weeks, range 26-29; birthweight 1140 g, 640-1300) received placebo. There was no significant difference in the duration of ventilation dependency (median 3 days, range l-23 surfactant; 5 days, range l-20 placebo) and oxygen dependency (median 8 days, 7-55 surfactant; median 10 days, range 5-58 placebo) between the two groups. Respiratory function was assessed by measurement of functional residual capacity (FRC) using a helium gas dilution technique and thoracic gas volume (TGV) and airways resistance (Raw) using a plethysmographic technique. Specific conductance (SGaw) was calculated from Raw and TGV. There was no significant difference in the FRC (median 24, range 21-29 ml/kg surfactant; median 29, range 25-37 ml/kg placebo) or TGV (median 31, range 23-38 ml/kg surfactant: 34,29-40 placebo). Raw, however, was significantly lower in the surfactant group (median 41, range 21-48 cmHIOil per s) compared to the placebo group (median 57, range 40-68 cm H,O/l per s), P < 0.05 and SGaw was significantly higher in the surfactant group (median 0.136, range 0.063-0.289 cmHzO/l per s) compared to the placebo group (median 0.081, range 0.062-0.134 cmHzOil per s), P < 0.05. These results suggest that surfactant replacement therapy improves lung function at follow-up.
Effects of fetal haemoglobin on the NIR analysis of neonatal cerebral oxygenation. Y. Wickramasinghea, K. Palmerb, R. Houstona, S. Spencerb, P. Rolfea and M. Thornileya, aDepartment of Biomedical Engineering and Medical Physics, Hospital Centre, Hartshill, Stoke-on-Trent, ST4 7QB and bNorth Staffs Maternity Hospital, Stoke-on-Trent, ST4 6SD (UK) Introduction. Fetal haemoglobin (HbF) constitutes 50-85% of total haemoglobin at birth, which gradually reduces to less than 15% at 1 year [ 11. Most of the theoretical and experimental evidence suggests that there is no clinically significant effect of HbF on techniques such as pulse oximetry. The spectral absorption characteristics of HbF and adult haemoglobin (HbA) have differences in the visible range but these are much less at near infrared wavelengths. Near infrared spectroscopic (NIRS) monitoring of cerebral oxygenation utilises light in the wavelength range 775 nm to 900 nm. The application of NIRS has now been extended from neonates to the fetus and methods of representing the NIRS data have also advanced from trend monitoring to absolute quantification of cerebral blood volume (CBV) and cerebral blood flow (CBF). The measurement of CBV and CBF has also been validated against other methods [2]. Methods. We have investigated whether the presence of HbF influences the calculated concentration changes of cerebral oxy and deoxy haemoglobin (HbQ, and Hb) in neonates. Two sets of NIR multiplier coefftcients (NIRA and NIRF) were used for the analysis, where the NIRA coefficients were derived from the absorption coefficients of adult haemoglobin and NIRF from those of fetal haemoglobin [3]. Five babies who had not received a blood transfusion and who were receiving added oxygen were studied. FiO, was adjusted to induce a transient fall in saturation of maximum 10%. Results. The changes in cerebral oxyhaemoglobin (HbG,) and deoxyhaemoglobin (Hb) were calculated assuming 100% adult Hb (HbQ2A and HbA) and 100% fetal Hb (HbGaF and HbF). The relationship between HbGzA and HbQsF as well as between HbA and HbF were tested. The slope and intercept (regression analysis) gives the relationship between these when using the two different sets of NIR coefficients. For oxyhaemoglobin (HbOd the maximum deviation from unity for slope was 0.05 and for deoxyhaemoglobin (Hb) this was 0.02. For HbGz the maximum deviation from zero for the intercept was 0.01
87
and for Hb this was 0.009. This shows that the error in NIR analysis of neonatal cerebral oxygenation due to the presence of fetal haemoglobin is inconsequential. Acknowledgements. This work was supported by the Action Research, Science. and Engineering Research Council and West Midlands Regional Health Authority. 1 Kelleher, J.F. (1989) J. Clin. Monit., 5 (I), 37-61. 2 Wickramasinghe, Y.A.B.D. et al. (1992) Arch. Dis. Child, in press. 3 Zijlstra, W.G., Buursma, A. and Meeuwsen-van der Roest, W.P. (1991): Clin. Chem., 37 (9), 1633-1638.
Continuous negative extiathoracic pressure and cerebral blood flow velocity - a pilot study. Joseph Rainea, Francis Cowanb, Martin P. Samuelsa, David Wertheimb, Patrick Roystonc, David P. Southalla, ‘Department of Paediatrics, Royal Brompton Hospital, bDepartment of Paediatrics, Hammersmith Hospital and %epartment of Medical Physics, Royal Postgraduate Medical School, London (UK) Continuous negative extrathoracic pressure (CNEP) is undergoing reevaluation as a treatment for neonatal respiratory failure. To examine whether the use of CNEP leads to changes in cerebral blood flow velocity (CBFV), a pilot study of 8 neonates aged 2-15 days (median 5) and gestation 25-36 weeks (median 29) was performed. All had respiratory distress syndrome (RDS) and were undergoing intermittent positive pressure ventilation (IPPV). Arterial blood pressure, oxygen saturation, transcutaneous PCO, and ECG were monitored continuously. CBFV in the middle cerebral artery was measured using a pulsed wave duplex Doppler system. CBFV was measured whilst IPPV was administered with either positive end expiratory pressure (PEEP) or CNEP. There were no statistically significant changes in CBFV, CBFV variability, heart rate, oxygen saturation and transcutaneous Pcq during the different ventilator regimes. There were, however, small but statistically significant decreases in arterial blood pressure with the change from IPPV and PEEP to IPPV and CNEP and significant increases in blood pressure with the change from IPPV and CNEP to IPPV and PEEP. This study shows that the use of CNEP, in conjunction with IPPV, does not lead to large changes in arterial CBFV and from this point of view, is safe to use in neonates with RDS.
Respiratory fimction at follow-up after neonatal surf&ant replacement therapy. B. Yuksel, A. Greenough and H.R. Gamsu, Department of Child Health, King’s College Hospital, London SE5 9RS (UK) Respiratory function was assessed at a median of 7 months (range 6-12) in 17 preterm infants who, in the neonatal period, had been entered into a multi-centre randomised placebo-controlled trial of surfactant replacement therapy with synthetic surfactant (Exosurf). Seven infants (median gestational age 28 weeks (range 26-23) and birthweight 1135 g (730-l 164) received surfactant and the remaining 10 infants (median gestational age 27 weeks, range 26-29; birthweight 1140 g, 640-1300) received placebo. There was no significant difference in the duration of ventilation dependency (median 3 days, range l-23 surfactant; 5 days, range l-20 placebo) and oxygen dependency (median 8 days, 7-55 surfactant; median 10 days, range 5-58 placebo) between the two groups. Respiratory function was assessed by measurement of functional residual capacity (FRC) using a helium gas dilution technique and thoracic gas volume (TGV) and airways resistance (Raw) using a plethysmographic technique. Specific conductance (SGaw) was calculated from Raw and TGV. There was no significant difference in the FRC (median 24, range 21-29 ml/kg surfactant; median 29, range 25-37 ml/kg placebo) or TGV (median 31, range 23-38 ml/kg surfactant: 34,29-40 placebo). Raw, however, was significantly lower in the surfactant group (median 41, range 21-48 cmHIOil per s) compared to the placebo group (median 57, range 40-68 cm H,O/l per s), P < 0.05 and SGaw was significantly higher in the surfactant group (median 0.136, range 0.063-0.289 cmHzO/l per s) compared to the placebo group (median 0.081, range 0.062-0.134 cmHzOil per s), P < 0.05. These results suggest that surfactant replacement therapy improves lung function at follow-up.
Effects of fetal haemoglobin on the NIR analysis of neonatal cerebral oxygenation. Y. Wickramasinghea, K. Palmerb, R. Houstona, S. Spencerb, P. Rolfea and M. Thornileya, aDepartment of Biomedical Engineering and Medical Physics, Hospital Centre, Hartshill, Stoke-on-Trent, ST4 7QB and bNorth Staffs Maternity Hospital, Stoke-on-Trent, ST4 6SD (UK) Introduction. Fetal haemoglobin (HbF) constitutes 50-85% of total haemoglobin at birth, which gradually reduces to less than 15% at 1 year [ 11. Most of the theoretical and experimental evidence suggests that there is no clinically significant effect of HbF on techniques such as pulse oximetry. The spectral absorption characteristics of HbF and adult haemoglobin (HbA) have differences in the visible range but these are much less at near infrared wavelengths. Near infrared spectroscopic (NIRS) monitoring of cerebral oxygenation utilises light in the wavelength range 775 nm to 900 nm. The application of NIRS has now been extended from neonates to the fetus and methods of representing the NIRS data have also advanced from trend monitoring to absolute quantification of cerebral blood volume (CBV) and cerebral blood flow (CBF). The measurement of CBV and CBF has also been validated against other methods [2]. Methods. We have investigated whether the presence of HbF influences the calculated concentration changes of cerebral oxy and deoxy haemoglobin (HbQ, and Hb) in neonates. Two sets of NIR multiplier coefftcients (NIRA and NIRF) were used for the analysis, where the NIRA coefficients were derived from the absorption coefficients of adult haemoglobin and NIRF from those of fetal haemoglobin [3]. Five babies who had not received a blood transfusion and who were receiving added oxygen were studied. FiO, was adjusted to induce a transient fall in saturation of maximum 10%. Results. The changes in cerebral oxyhaemoglobin (HbG,) and deoxyhaemoglobin (Hb) were calculated assuming 100% adult Hb (HbQ2A and HbA) and 100% fetal Hb (HbGaF and HbF). The relationship between HbGzA and HbQsF as well as between HbA and HbF were tested. The slope and intercept (regression analysis) gives the relationship between these when using the two different sets of NIR coefficients. For oxyhaemoglobin (HbOd the maximum deviation from unity for slope was 0.05 and for deoxyhaemoglobin (Hb) this was 0.02. For HbGz the maximum deviation from zero for the intercept was 0.01
87
and for Hb this was 0.009. This shows that the error in NIR analysis of neonatal cerebral oxygenation due to the presence of fetal haemoglobin is inconsequential. Acknowledgements. This work was supported by the Action Research, Science. and Engineering Research Council and West Midlands Regional Health Authority. 1 Kelleher, J.F. (1989) J. Clin. Monit., 5 (I), 37-61. 2 Wickramasinghe, Y.A.B.D. et al. (1992) Arch. Dis. Child, in press. 3 Zijlstra, W.G., Buursma, A. and Meeuwsen-van der Roest, W.P. (1991): Clin. Chem., 37 (9), 1633-1638.
Continuous negative extiathoracic pressure and cerebral blood flow velocity - a pilot study. Joseph Rainea, Francis Cowanb, Martin P. Samuelsa, David Wertheimb, Patrick Roystonc, David P. Southalla, ‘Department of Paediatrics, Royal Brompton Hospital, bDepartment of Paediatrics, Hammersmith Hospital and %epartment of Medical Physics, Royal Postgraduate Medical School, London (UK) Continuous negative extrathoracic pressure (CNEP) is undergoing reevaluation as a treatment for neonatal respiratory failure. To examine whether the use of CNEP leads to changes in cerebral blood flow velocity (CBFV), a pilot study of 8 neonates aged 2-15 days (median 5) and gestation 25-36 weeks (median 29) was performed. All had respiratory distress syndrome (RDS) and were undergoing intermittent positive pressure ventilation (IPPV). Arterial blood pressure, oxygen saturation, transcutaneous PCO, and ECG were monitored continuously. CBFV in the middle cerebral artery was measured using a pulsed wave duplex Doppler system. CBFV was measured whilst IPPV was administered with either positive end expiratory pressure (PEEP) or CNEP. There were no statistically significant changes in CBFV, CBFV variability, heart rate, oxygen saturation and transcutaneous Pcq during the different ventilator regimes. There were, however, small but statistically significant decreases in arterial blood pressure with the change from IPPV and PEEP to IPPV and CNEP and significant increases in blood pressure with the change from IPPV and CNEP to IPPV and PEEP. This study shows that the use of CNEP, in conjunction with IPPV, does not lead to large changes in arterial CBFV and from this point of view, is safe to use in neonates with RDS.