Wiel J Maertzdorf

Mixed Venous Oxygen Saturation and Biochemical Parameters of Hypoxia during Progressive Hypoxemia in 10- to 14-Day-Old Piglets

In this study we wanted to assess the relationship between mixed venous oxygen saturation (Svo2) and tissue oxygenation. For that, we compared the values of Svo2 with oxygen delivery (Do2), oxygen consumption (Vo2), and markers of tissue hypoxia such as lactate and pyruvate during progressive hypoxemia. Eight 10-14-d-old piglets were anesthetized, tracheotomized, intubated, and ventilated. A fiberoptic catheter was placed in the carotid artery to monitor arterial oxygen saturation(Sao2). A thoracotomy was performed, and a fiberoptic catheter was placed in the pulmonary artery to monitor Svo2. A transit time ultrasound flow probe was positioned around the ascending aorta to measure aorta flow. Progressive graded hypoxemia was induced by decreasing fractional inspiratory oxygen concentration (Fio2) from 1.0 to 0.30, 0.21, 0.15, and 0.10. After each Fio2 interval blood samples were taken for blood gases, lactate, and pyruvate. Do2 and Vo2 were calculated. Svo2 decreased similarly to Sao2. A value of Svo2 of more than 40% excluded oxygen restricted metabolism. When Do2 decreased below a critical range (8.4-12.8 mL/kg·min), Svo2 decreased below 15%, and lactate and the lactate/pyruvate ratio increased. We conclude1) that baseline Svo2 values excluded oxygen-restricted metabolism, 2) that Svo2 values between 15 and 40% were not a marker for oxygen-restricted metabolism, and 3) that Svo2 values below 15% were associated with oxygen-restricted metabolism. Reduced Svo2 values must be interpreted as a change of the factors that determine the balance between Do2 and Vo2 and as a warning that, with further reduction of Svo2, oxygen restricted metabolism can develop.

Effects of partial plasma exchange transfusion on cerebral blood flow velocity in polycythaemic preterm, term and small for date newborn infants

Isovolemic haemodilution with plasma was performed in 36 newborn infants with polycythaemia 3 h after birth. Continuous wave Doppler ultrasonography was used to study the short and longer term influence of partial plasma exchange transfusion on cerebral blood flow velocity in both the anterior cerebral and mid cerebral arterial system up to 24 h after haemodilution. The study group consisted of 11 preterm infants, 12 term infants, and 13 small for date infants. After exchange transfusion peripheral venous haemotocrit decreased from 72.5% to 59.4%. In all experimental groups cerebral blood flow velocity (CBFV) before exchange transfution was significantly lower (18%–44%) than matched controls, and increased to control levels after exchange transfusion. CBFV improved most in preterm infants. After the transfusion the values were no different from the age-, weight-, sex-and parity-matched control groups, and they remained at this level during the next 24 h. No differences could be found between the anterior and mid-cerebral arterial system. When clinical symptoms were present, they subsided in all infants. In conclusion, partial plasma exchange transfusion has a favourable effect for at least 24 h on cerebral blood flow velocity in newborn infants with polycythaemia.

Frequency Shift of Individual Spontaneous Otoacoustic Emissions in Preterm Infants

In adults, spontaneous otoacoustic emissions (SOAE) have shown a considerable frequency stability. In preterm infants, however, the SOAE proved to show an apparent and consistent upward shift of frequency at increasing postconceptional age (PCA). In 25 ears of 14 preterm infants (PCA, 29.1-41.3 wk) a total of 66 SOAE frequencies were monitored, ranging from 1611 to 5774 Hz. All but one of the SOAE frequencies shifted toward higher frequency. The SOAE frequency shift rate in Hertz per week was proportionally constant relative to the SOAE frequency. The mean shift rate was 0.74 ± 0.39%/wk. At increasing PCA, the SOAE frequency shift rate tended to slow down. A linear fit through the data predicted the SOAE frequency to stop at about 45-50-wk PCA. The frequency dependence and time course of the SOAE frequency shift strongly suggest cochlear maturation during the last period of gestation.

Long-term and Short-term Variations in Amplitude and Frequency of Spontaneous Otoacoustic Emissions in Pre-term Infants

In pre-term infants, spontaneous otoacoustic emission (SOAE) frequencies show an upward shift with time. The present study aimed to monitor the SOAE amplitude variation during this frequency shift. A long-term observation of 87 SOAE frequencies from 18 pre-term infants yielded a positive frequency shift of 0.72 per cent per week, which was not accompanied by a simultaneous amplitude shift, as the mean variations in SOAE amplitude were practically zero. Furthermore, there was no relationship between the short-term SOAE amplitude variation and the infants post-conceptional age. Only the absolute amount of SOAE amplitude variation seemed to grow with time. Comparison with induced variations in SOAE frequency argues against a middle ear influence on the SOAE frequency shift. In our view, the absence of any amplitude shift during the upward SOAE frequency shift further suggests cochlear development during the last period of gestation.

Continuous central venous oxygen saturation (ScvO2) measurement using a fibre optic catheter in newborn infants.

AIMS: To describe the range of central venous oxygen saturation (ScvO2) values in stable newborn infants breathing room air; to examine the correlation between ScvO2 and arterial oxygen saturation (SaO2); to describe fractional oxygen extraction; and the shunt index, an estimate of the venous admixture. METHODS: A prospective clinical observational study was made of 10 preterm infants breathing room air after the acute phase of respiratory distress syndrome, and with an umbilical venous catheter in situ. A fibre optic catheter remained in the right atrium for continuous measurement of oxygen saturation. RESULTS: ScvO2, SaO2, blood pressure and heart rate were registered every 15 minutes. Fractional oxygen extraction and shunt index were calculated. SaO2 and ScvO2 were 93.4 (SD 3.7)% and 73.56 (5.25)%, respectively. In seven patients ScvO2 values correlated significantly with SaO2. Fractional oxygen extraction was 0.21 (0.04) and was significantly correlated with ScvO2. The shunt index was 24% (12) and was significantly correlated with SaO2. CONCLUSIONS: Stable preterm infants breathing room air had an ScvO2 ranging from 65% to 82% (5th and 95th percentile), which corresponded to SaO2 > or = 86%. ScvO2 values were significantly correlated with SaO2 in most patients.

Use of Teicoplanin in Preterm Neonates with Staphylococcal Late-Onset Neonatal Sepsis

Objective: To study the clinical pharmacology of teicoplanin in babies admitted to a newborn intensive care unit, by monitoring serum levels, efficacy and potential side effects. Methods: An open, nonrandomized descriptive study was performed in the neonatal intensive and high care unit of the Universtiy Hospital Maastricht, The Neterlands. Twenty-three preterm neonates, gestational age ranging from 26 to 32 weeks (median 28.4 weeks), postnatal age from 5 to 47 days, and birth weight from 570 to 1,740 g, presenting with (suspected) late onset septicemia, were studied. Of 21 culture-proven septicemias, 20 were caused by staphylococci. The teicoplanin loading dose was 15 mg/kg i.v., followed by a maintenance dose of 8 mg/kg every 24 h. Intravenous gentamicin was also administered pending blood culture. Serum teicoplanin concentrations were measured by fluorescence polarization immunoassay. Clinical and microbiological cure/failure rates were determined and possible side effects were monitored. Results: The study of individual pharmacokinetics during multiple-dose intravenous infusions was rendered impossible by apparently inaccurate dosing. Peak (30 min after end of the infusion) and trough teicoplanin levels were stable throughout the study and averaged 27.8 (interquartile range 23.7–32.9) and 12.3 (interquartile range 9.1–16.8) mg/l, respectively. The microbiological and clinical cure rates were 90% in gram-positive septicemia. There was no apparent toxicity. Conclusions: Inaccurate drug administration was a problem in this study, making a multidose pharmacokinetic study impossible. It is possible that inaccurate drug administration and not current dosage guidelines yielded trough levels below 10 mg/l in 57 (32%) of 176 instances. This pharmaceutical aspect clearly warrants further study. However, microbiological and clinical cure rates were high in gram-positive septicemias. No side effects attributable to teicoplanin therapy were encountered.

Click-evoked oto-acoustic emission measurement in preterm infants.

Abstract Click-evoked oto-acoustic emissions (CEOAE) are acoustic responses produced by the inner ear, reflecting functional auditory integrity. We studied both the success rate of the CEOAE method and the CEOAE presence in preterm infants during their stay at the Neonatal Intensive Care Unit (NICU), by analysis of the results of longitudinal CEOAE measurements in 19 preterm infants. The CEOAE method proved to be feasible in the majority of the population under study; the CEOAE measurement failed in 8% of the total of 226 attempts. Within the range of 30–40 weeks post-conceptional age (PCA) the CEOAE presence increased from about 50% to 80%. These results show the possible clinical application of CEOAE in a NICU for the monitoring of cochlear function during treatment of preterm infants. Conclusion Bedside CEOAE measurement in preterm infants in a NICU is feasible at a PCA as low as 30 weeks.

The effect of hypercapnia and hypercapnia associated with central cooling on breathing in unanesthetized fetal lambs

In utero breathing activity is present periodically, but it must become continuous at birth. We investigated the effect of hypercapnia and of hypercapnia combined with central cooling on fetal breathing in seven chronically instrumented fetal lambs of 131-134-d gestation, using an extracorporeal membrane oxygenation (ECMO) system to control fetal blood gases and fetal temperature. During fetal hypercapnia (from a partial pressure of arterial CO2 (Paco2) 6.18 ± 0.11 kPa to Paco2 7.39± 0.15 kPa) frequency, amplitude, and incidence of fetal breathing movements during low voltage electrocortical activity (LV ECoG) increased significantly compared with isocapnic control on ECMO, but breathing remained absent during high voltage electrocortical activity (HV ECoG). During hypercapnia accompanied by central cooling (Paco2 7.90 ± 0.13 kPa, temperature decreased by 2.1°C) there were similar changes in fetal breathing movements during LV ECoG, but in four out of seven fetuses fetal breathing movements continued throughout HV ECoG. Hypercapnia accompanied by central cooling can thus override the inhibitory effects of HV ECoG on fetal breathing movements. This may be due to changes in sensitivity to CO2 produced by an increase in afferent input to the CNS.

Delayed Peripheral Auditory Maturation in Small for Gestational Age Infants; a Matched Control Study of Click Evoked Otoacoustic Emissions

Delayed Peripheral Auditory Maturation in Small for Gestational Age Infants; a Matched Control Study of Click Evoked Otoacoustic Emissions

VENOUS OXYGEN SATURATION (SvO 2 ) AND CHANGE IN LACTATE DURING PROGRESSIVE ISOVOLEMIC ANEMIA IN 10 DAY OLD PIGLETS. 315

VENOUS OXYGEN SATURATION (SvO 2 ) AND CHANGE IN LACTATE DURING PROGRESSIVE ISOVOLEMIC ANEMIA IN 10 DAY OLD PIGLETS. 315