Effect of blood transfusions on cerebral haemodynamics in preterm infants

Aim: To assess the possible cerebral haemodynamic changes occurring in preterm infants after blood transfusions. Methods: Preterm infants who had undergone blood transfusions were prospectively studied using both near infrared spectroscopy and cerebral Doppler ultrasonography. Results: Fourteen infants (mean gestational age 29.6 wk, SD 2.6; mean birthweight 1430 g, SD 332) were studied at the mean age of 29 (SD 14) d. A significant increase in oxygenated haemoglobin (O 2 Hb), deoxygenated haemoglobin (HHb), mixed cerebral oxygen saturation (SmO 2 ) and change in cerebral blood volume occurred after transfusion. Between ultrasound parameters, we found a decrease in diastolic velocity and an increase in resistance index.

Conclusion: Blood transfusions improve cerebral oxygen supply and induce a decrease in cerebral blood volume, probably due to an increase in cerebral vessel resistance.     

Randomized trial of high-frequency oscillatory ventilation versus conventional ventilation: effect on systemic blood flow in very preterm infants

OBJECTIVE: Low superior vena cava (SVC) flow is common in very preterm infants in the first day and strongly associated with periventricular hemorrhage and disability. We examined the effect of high-frequency oscillatory ventilation (HFOV) compared with conventional ventilation (CV) on SVC flow and right ventricular output. METHODS: Forty-five infants <29 weeks were randomized before 1 hour of age to HFOV or CV. Echocardiography was performed on 43 infants at 3, 10, and 24 hours of age. Infants with low SVC flow (<50 mL/kg/min) or hypotension (mean blood pressure < or =20) were treated with volume and inotrope. RESULTS: Infants allocated to HFOV (n=23) and to CV (n=20) were well matched. There was a nonsignificant trend toward more infants on HFOV having SVC flow <50 mL/kg/min (48% vs 20%) and receiving volume and inotropes (61% vs 40%). There were no significant differences in mean SVC flow or right ventricular output at 3, 10, or 24 hours. Infants on HFOV had a significantly higher calculated upper body vascular resistance at 10 hours and mean blood pressure at 24 hours. CONCLUSIONS: There were no significant adverse effects of HFOV on systemic blood flow in very preterm infants during the first 24 hours of life.     

Effects of repeated indomethacin administration on cerebral oxygenation and haemodynamics in preterm infants: Combined near infrared spectrophotometry and Doppler ultrasound study

The objectives of this study were to evaluate the effect of repeated indomethacin administration on cerebral oxygenation in relation to changes in cerebral blood flow velocity (CBFV) and other relevant physiological variables. Fourteen preterm infants with patent ductus arteriosus were studied during three subsequent indomethacin bolus administrations with intervals of 12 and 24 h. Changes in concentration of oxyhaemoglobin (cO₂Hb), deoxyhaemoglobin (cHHb) and oxidized cytochrome aa₃ (cCyt.aa₃) in cerebral tissue and changes in cerebral blood volume (CBV) were measured by near infrared spectrophotometry; changes in mean CBFV in the internal carotid artery were measured by pulsed Doppler ultrasound. Simultaneously heart rate, transcutaneouspO₂ andpCO₂, arterial O₂ saturation and blood pressure were measured. All variables were continuously recorded until 60 min after indomethacin administration. Within 5 min after each indomethacin administration, significant decreases in CBFV, CBV and cO₂Hb and cCyt.aa₃ were observed which persisted for at least 60 min, while cHHb increased or did not change at all. There were no changes in the other variables recorded. These data demonstrate that indomethacin administration is accompanied by a reduction in cerebral tissue oxygenation due to decreased cerebral blood flow. Therefore, low arterial oxygen content, either caused by low arterial O₂ saturation or by low haemoglobin concentration, may be a contraindication for indomethacin treatment in preterm infants.     

The effect of phototherapy on cerebral blood flow velocity in preterm infants

Cerebral blood flow velocity was studied with two-dimensional/pulsed Doppler ultrasound before, during and after discontinuation of phototherapy in 22 preterm infants (gestational age ≤32 weeks), who were treated for a minimum of 12h with blue-light phototherapy for non-haemolytic hyperbilirubinaemia. Before the cerebral blood flow velocity measurements, patency of the ductus arteriosus was diagnosed by Doppler echocardiography. All infants had normal brain ultrasound scans. Mean cerebral blood flow velocity increased significantly after initiation of phototherapy in all infants. Only in “healthy” (non-ventilated) infants did cerebral blood flow velocity return to pre-phototherapy values (baseline) after discontinuation of phototherapy, whereas in “unhealthy” (ventilated) infants cerebral blood flow velocity did not return to baseline. In 10 infants the ductus arteriosus reopened during phototherapy. In those infants, mean cerebral blood flow velocity returned to pre-phototherapy values after 2h of phototherapy prior to its discontinuation.     

Estimating cerebral blood flow in newborn infants: comparison of near infrared spectroscopy and 133Xe clearance.

A new method of measuring cerebral blood flow (CBF) in newborn infants by means of near infrared spectroscopy (CBFnirs) was compared with the i.v. 133Xe clearance technique (CBFxe). Forty CBFnirs measurements were obtained during 19 133Xe measurements in 16 infants; 79 other CBFnirs data sets were discarded because the assumptions for their use were not fulfilled. The test-retest variation of repeated near infrared-measurements during each 133Xe clearance was 17.5%. CBFnirs was closely related to CBFxe (r2 = 0.84, p less than 0.0001), with a slope of 0.75 (SEM = 0.064) and a intercept of 1.58 mL/100 g/min (SEM = 0.51). The difference between the measurements obtained by the two methods (CBFnirs-CBFxe) was negative in the high range of CBF, whereas the difference was close to zero in the low range. We conclude that CBF measured with near infrared spectroscopy was in good agreement with the CBF measured with the 133Xe method. The near infrared spectroscopy method has the advantage of being noninvasive, and it does not involve ionizing radiation. Because of methodologic constraints, however, it may underestimate CBF in the high range of flow, and it may have limitations of application in clinical research.     

Increased cerebral blood flow velocities in newborn infants of smoking mothers

Cerebral blood flow velocities (CBFV) were measured by the pulsed Doppler method in 41 infants of smoking mothers and in 59 apparently healthy control infants. Although gestational age, birth weight, and systolic blood pressure were lower in infants exposed to tobacco smoke prenatally, systolic (65±11 vs. 47±12 cm/s, mean ±SD;P<0.001), mean (36±6 vs. 25±6 cm/s;P<0.001), and diastolic (17±4 vs 13±4 cm/s;P<0.001) CBFVs in the anterior cerebral artery were significantly higher when compared to control infants. Similar differences were seen in the internal carotid and in the basilar arteries. Multiple regression analysis did not reveal differences other than maternal smoking to explain these observations. We conclude that prenatal tobacco smoke exposure is related to increased CBFVs in newborn infants. Further studies should determine whether this relation is not only statistical but causal and whether increased CBFVs are an indicator of prolonged effects of prenatal tobacco smoke exposure.     

早产儿呼吸窘迫综合征高频振荡通气后两种撤机方式的安全性研究：前瞻性随机对照试验

目的 探讨高频振荡通气（HFOV）治疗早产儿呼吸窘迫综合征（RDS）后两种撤机方式的安全性。方法 前瞻性纳入2019年1月1日至2020年6月30日厦门市妇幼保健院新生儿科重症监护病房（NICU）收治的胎龄≤ 32⁺⁶周或体重≤ 1 500 g、首选HFOV治疗的RDS早产儿101例,随机分为HFOV直接撤机组（观察组）50例,HFOV转为常频机械通气撤机组（对照组）51例。比较两组患儿撤机后72 h内的撤机失败率,撤机前2 h、撤机后2 h、撤机后24 h的血气分析各指标,比较两组呼吸支持治疗情况、并发症的发生率及出院时的转归情况。结果 观察组和对照组撤机失败率差异无统计学意义（8% vs 14%,P > 0.05）。观察组有创机械通气时间较对照组缩短[（64±39）h vs（88±69）h,P < 0.05]。两组患儿总机械通气时间、总用氧时间、撤机前后的血气分析各指标、并发症发生率、出院时转归情况差异均无统计学意义（均P > 0.05）。结论 对于RDS早产儿,使用HFOV后采取直接撤机策略是安全可靠的,且可减少有创呼吸机使用时间,值得临床推广应用。     

Evaluation of change of cerebral circulation by SpO2 in preterm infants with apneic episodes using near infrared spectroscopy

BACKGROUND: In the neonatal intensive care unit (NICU), hemodynamics in very low-birthweight infants are generally examined for oxygen saturation (SpO2), heart rate, respiration rate, and blood pressure. The present study examined how changes in cerebral circulation in preterm infants can be evaluated by the SpO2 monitoring method with near infrared spectroscopy (NIRS) to detect the cerebral circulation. METHODS: The study was conducted in 11 low-birthweight neonates with a mean weight of 1252 g (940-1948 g), mean post-conceptional age of 28.9 weeks (28-31 weeks) and in whom a total of 145 apneic episodes were examined. Changes in cerebral circulation at the apneic attack were evaluated by two parameters of Delta HbD ( micro mol/L) for reduction in cerebral oxygenation and Delta cHb (mL/100 g brain) for variation in cerebral blood volume using the near infrared spectroscopy (NIRS). RESULTS: There was a tendency for a reduction in cerebral oxygenation and a change in cerebral blood volume as SpO2 was reduced. In the event of apneic attacks where SpO2 was reduced to <85%, cerebral oxygen saturation was extensively reduced. In addition, cerebral blood volume was also greatly changed when the SpO2 was reduced to <85%, and changed further still when SpO2 was reduced again to < or =75%. CONCLUSION: Reduction in SpO2 (<85%) was suggested to be an effective indication to changes in cerebral circulation. In the case of apneic attacks where SpO2 was < or =85%, the cerebral circulation in preterm low-birthweight neonates was extensively changed and, therefore, attention should be paid to changes in the concentration of SpO2 when managing apnea of prematurity in NICU.     

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.Abbreviations AUC area under the curve (mean flow velocity) - CBFV cerebral blood flow velocity - EDFV end diastolic flow velocity - Hct haematocrit - PI pulsatility index according to Pourcelot - PRET partial plasma exchange transfusion - PSFV peak systolic flow velocity     

The effect of blood transfusion and haemodilution on cerebral oxygenation and haemodynamics in newborn infants investigated by near infrared spectrophotometry

The objective of this study was to investigate the influence of blood transfusion and haemodilution on cerebral oxygenation and haemodynamics in relation to changes in cerebral blood flow velocity (CBFV) and other relevant physiological variables in newborn infants. Thirteen preterm infants with anaemia (haematocrit < 0.33) and ten infants with polycythaemia (haematocrit > 0.65) were studied during blood transfusion and haemodilution respectively using adult red blood cells and partial plasma exchange transfusion. Changes in cerebral concentrations of oxyhaemoglobin (cO₂Hb), deoxyhaemoglobin (cHHb), total haemoglobin (ctHb), (oxidized - reduced) cytochrome aa₃ (cCyt.- aa₃) were continuously measured using near infrared spectrophotometry throughout the whole procedure. Simultaneously, changes of mean CBFV in the internal carotid artery were continuously measured using pulsed Doppler ultrasound. Heart rate, transcutaneous partial pressure of oxygen and carbon dioxide, and arterial O₂ saturation were continuously and simultaneously measured. Blood transfusion resulted in increase of cO₂Hb, cHHb, ctHb and red cell transport (product of CBFV and haematocrit), whereas CBFV decreased. The increase of cO₂Hb exceeded that of cHHb, reflecting improvement of cerebral O₂ supply. Haemodilution resulted in a decrease of cO₂Hb, cHHb and ctHb, whereas CBFV increased. Red cell transport was unchanged. The decrease of cO₂Hb exceeded that of cHHb, reflecting decreased cerebral O₂ supply. cCyt.aa₃ decreased after blood transfusion and remained unchanged after haemodilution, but the reliability of these results is uncertain. With the exception of a small, but significant increase in transcutaneous partial pressure of oxygen after blood transfusion, the other variables showed no changes. Each blood withdrawal during exchange transfusion resulted in only a significant increase in heart rate without changes in the other variables measured, suggesting unchanged cerebral perfusion. Conclusion In newborn infants blood transfusion in anaemia results in improvement of cerebral oxygenation, but haemodilution in polycythaemia does not improve cerebral oxygenation despite possible improvement of cerebral perfusion. Received: 21 December 1995 and in revised form: 29 August 1996 / Accepted: 4 September 1996