A.F.J. van Heyst

Hemodynamic changes during opening of the bridge in venoarterial extracorporeal membrane oxygenation

Objective To investigate the cause of the hemodynamic changes occurring during opening of the bridge in venoarterial (VA) extracorporeal membrane oxygenation (ECMO). Design Prospective intervention study in animals. Setting Animal research laboratory of a university medical center. Subjects Eight anesthetized lambs installed on VA-ECMO. Interventions During VA-ECMO the bridge was randomly opened during 1, 2.5, 5, 7.5, 10, and 15 secs at ECMO flow rates of 500, 400, 300, 200, 100, and 50 mL/min. Flows in the ECMO circuit between venous cannula and bridge and bridge and arterial cannula, mean arterial blood pressure, mean left carotid artery blood flow, central venous pressure, superior sagittal sinus pressure, inline mixed venous oxygen saturation, heart rate, and arterial oxygen saturation were measured continuously. Using near infrared spectrophotometry, changes in concentrations of cerebral oxygenated and deoxygenated hemoglobin and cerebral blood volume were also measured. Values during bridge opening were compared with values before opening. The same variables were determined with a roller pump on the bridge with a flow over the bridge at various flow rates. Measurements and Main Results Bridge opening resulted in a change of flow direction between venous cannula and bridge and bridge and arterial cannula. A biphasic response with initial decrease and secondary increase occurred in mean arterial blood pressure and mean left carotid artery blood flow. Central venous pressure, superior sagittal sinus pressure, deoxygenated hemoglobin, and cerebral blood volume increased, whereas cerebral oxygenated hemoglobin decreased. These effects occurred in each combination of ECMO flow rate and opening time. These effects could be abolished by installing a roller pump on the bridge. Conclusions Bridge opening in VA-ECMO resulted in significant cerebral hemodynamic changes caused by an arteriovenous shunt over the bridge. The decreased cerebral perfusion pressure may contribute to the occurrence of cerebral ischemia, and the venous congestion may result in intracranial hemorrhages. These could be prevented by installing a roller pump on the bridge.

Serial plasma concentrations of atrial natriuretic peptide, plasma renin activity, aldosterone, and antidiuretic hormone in neonates on extracorporeal membrane oxygenation.

To obtain information on water and salt regulating hormones and volume homeostasis during neonatal extracorporeal membrane oxygenation (ECMO), serial determinations of atrial natriuretic peptide (ANP), plasma renin activity (PRA), aldosterone (Aldo), antidiuretic hormone (ADH), colloid-osmotic pressure (COP), osmolality (Osmol), and central venous pressure (CVP) before, during, and after neonatal ECMO in 10 neonates with meconium aspiration syndrome (MAS) were carried out. Mean gestational ages and birth weights were 41+3 weeks (39+6 - 42+4) and 4,063 gm (3,500–4700), respectively; mean age at start and duration of ECMO 29.3 (14–69) and 152.6 hr (92–267), respectively. Plasma ANP (mean ± SD) was 67.8 ± 69.1 pmol/L before, decreased to 33.3 ± 22.1 (not significant) pmol/L during, and significantly increased to 274.6 ± 131.8 pmol/L after ECMO (p < 0.05). ANP correlated positively with CVP (r = 0.63;p < 0.001). Pre-ECMO PRA, Aldo, and ADH were comparable to those described earlier in normal neonates, decreased during (p < 0.001 for Aldo;p < 0.05 for PRA and ADH) and either remained elevated (PRA, p < 0.001; Aldo, p < 0.05) or decreased (ADH) after ECMO. COP and Osmol remained unchanged. Neonatal ECMO for MAS is characterized by circulatory and osmotic equilibrium. It is suggested that circulating volume contracts during and expands after neonatal ECMO for MAS.

Intravascular volume administration: a contributing risk factor for intracranial hemorrhage during extracorporeal membrane oxygenation?

OBJECTIVE. The objective of this study was to determine the relationship between the frequency and total volume of intravascular volume administration and the development of intracranial hemorrhage during venoarterial extracorporeal membrane oxygenation. METHODS. In a retrospective, matched, case-control study, 24 newborns who developed an intracranial hemorrhage during venoarterial extracorporeal membrane oxygenation treatment were compared with 40 control subjects. Both groups were analyzed for gestational age, gender, race, Apgar scores at 1 and 5 minutes, birth weight, cardiopulmonary resuscitation before venoarterial extracorporeal membrane oxygenation, age at the start of treatment, duration of treatment, worst arterial blood gas sample preceding treatment, activated clotting time values, need for platelet transfusions, mean blood pressure, and the use of inotropics and steroids before the treatment. For both groups, total number and volume of intravascular infusions of normal saline, pasteurized plasma protein solution, erythrocytes, and platelets during the first 24 hours of treatment were determined. Variables were analyzed in their relationship to intracranial hemorrhage by using univariate and multivariate conditional logistic regression. RESULTS. The only statistically significant difference in patient characteristics between the case patients and control subjects was arterial blood gas values. Newborns who developed intracranial hemorrhage during the treatment received both a statistically significantly higher number and a statistically significantly higher total volume of intravascular volume administrations compared with control patients. After adjustment for pH, Paco2, and Pao2 in the multivariate analysis, we found a significant relation between the development of intracranial hemorrhage and >8 infusions or >300 mL of volume infusion in the first 8 hours and >10 infusions in the first 24 hours of treatment. CONCLUSIONS. The number and total volume of intravascular volume administration in the first 8 and 24 hours of venoarterial extracorporeal membrane oxygenation treatment are statistically significantly related to the development of intracranial hemorrhage.

Abnormalities of coagulation related to the use of inhaled nitric oxide before extracorporeal membrane oxygenation.

Objective: Evaluation of the influence of previous inhaled nitric oxide (iNO) treatment on the occurrence of clotting complications and disseminated intravascular coagulation during extracorporeal membrane oxygenation (ECMO). Design: Retrospective study in newborns treated with venoarterial ECMO during a 5-yr period. Setting: Neonatal intensive care unit of a university medical center. Patients: A total of 59 newborns with severe respiratory insufficiency treated with venoarterial ECMO. Interventions: Patients received iNO before ECMO (iNO group) or not (control group). Measurements and Main Results: There were no differences between the groups for patient characteristics and medication use before ECMO, except for norepinephrine. After correction for diagnosis and duration of ECMO, significantly more clotting complications and disseminated intravascular coagulation as individual variables were seen in the iNO group. For the combination of clotting complications and disseminated intravascular coagulation, there was a significantly higher prevalence in the iNO group. Conclusions: In our population, we found a remarkable relationship between clotting complications or disseminated intravascular coagulation and iNO use before ECMO treatment, which needs further prospective research before conclusions can be drawn.