oa Advanced hemodynamic monitoring in critically ill neonates

The neonatal circulation is unique due to the presence of fetal shunts. With the advances in biomedical technology, the assessment of sick newborn infants has improved significantly. It allows to collect, store and analyze the complex physiometric data and provides a foundation for advances in diagnosis and management of neonatal cardiovascular compromise. This could allow the clinician to have objective information to compliment the clinical assessment. Additionally, serial assessments and trending of measured parameters provides longitudinal information on disease pathophysiology and the response to treatment.

The advanced hemodynamic monitoring however has to be structured and focussed to get the relevant information to compliment clinical signs and symptoms. It however has an inherent risk of inappropriate or over-treatment leading to a state of confusion. The following questions should thus be addressed at the outset:

1. Objectives of assessment and goal of therapy 2. Available techniques and processing information 3. Point assessment vs continuous assessment 4. Invasive monitoring vs non-invasive monitoring

The goal of hemodynamic monitoring is to optimise end-organ perfusion. The delivery of oxygen (DO2) depends on gas exchange, haematocrit, macrocirculation (preload, cardiac function and afterload) and microcirculation (capillary and end organ perfusion) (Table 1)¹. The point-of-care functional echocardiography is helpful for initial assessment to complement continuous assessment techniques such as non-invasive continuous hemodynamic monitoring and in emergency situations of hemodynamic instability.

When utilising these techniques, the limitations of individual devices and the interaction between them should be known. As compared to point-of-care assessment, when non-invasive monitoring devices are used, the trending of data from them with simultaneous single screen longitudinal display of values is helpful for diagnosis of disease and assessing response to treatment (Figure 1).² The examples are continuous cardiac output, blood pressure, central venous pressure, pulse oximetry and near infrared spectroscopy. The trending of heart rate monitoring has already been utilised for early detection of sepsis using HeRO monitor. There has been interest in continuous amplitude integrated EEG but so far it is limited to research trials.

We compared measurement of cardiac output with echocardiography with non-invasive cardiac output monitoring. We observed that absolute values were different but the trend on longitudinal assessment was comparable. This could be due to the fact that non-invasive cardiac output assessment methods utilise indirect techniques such as electric velocimetry, arterial pulse contour analysis etc. Using an example of a baby with septic shock, one can understand how the hemodynamic monitoring can guide initial management.³

BP =  cardiac output (CO) x systemic vascular resistance (SVR) (Figure 2) ⁴

If a patient has low CO, high SVR and normal BP, the choice of treatment is inodilators e.g., milrinone. If CO, SVR and BP are all low, commence treatment with norepinephrine and add epinephrine. If high CO and low BP and SVR, give fluid bolus initially and titrate therapy.

The integration of advanced hemodynamic monitoring in clinical care is akin to whole genome sequencing where a large amount of information is gathered which requires processing. Utilising this information is a challenge at present but it has the potential to open gateways for precision medicine.⁵