Monitoring of Neonatal Haemodynamics

Case 1
35 YO G3P2, uneventful pregnancy
Presented in labour @ 39 wks
Shoulder dystocia
Pulseless, apneic, and pale
Responded to PPV and chest compressions. AS 1, 3, 6, 7

Case 1
At 20 min of life:
Ventilated, poor resp. effort, FiO 2 0.25
Temp 36ºC, HR 120 bpm, MBP 42 mmHg
Mottled skin, CRT 3-4 sec

Case 1
What is the next action?

Case 2
25 YO, G2P1, regular ANC
Presented 3 days prior to delivery in threatened preterm labour @ 26 wks
No pPROM
Received Beta x 2, Amp and Erythro
Baby was born pink, HR>100, apneic
Intubated, Bless, Ventilated, UAC, UVC

Case 2
At 1 hr of age:
AC/VG, PEEP 6, VG 4 ml/kg, FiO 2 0.23
HR 150 bpm, MBP 23 mmHg, CRT 2-3 sec

Case 2

Case 3
25 YO, G2P1, regular ANC
Presented 3 days prior to delivery in threatened preterm labour @ 26 wks
No pPROM
Received Beta x 2, Amp and Erythro
Baby was born pink, HR>100, apneic
Intubated, Bless, Ventilated, UAC, UVC

Case 3
At 6 hrs of age:
HR 150 bpm, MBP 29 mmHg, CRT 2-3 Sec
AC/VG, PEEP 6, FiO 2 0.25, VG 4 ml/kg,
VR 40, RR 50’s
ABG: pH 7.22, PCO 2 37, PO 2 54,
HCO 3 15, BE -12

Case 3

Monitoring of Neonatal Hemodynamics* Ayman Abou Mehrem, MD, CABP Neonatology Fellow University of Manitoba * Adapted from Early Human Development 86 (2010) 135-165

Monitoring of Neonatal Hemodynamics
Introduction
Objective
Part 1: Clinical Monitoring of Systemic Hemodynamics
Part 2: Cardiac Output Monitoring
Part 3: Functional Echocardiography
Part 4: Peripheral Hemodynamics

Introduction
Hemodynamics: from Greek
αίμα (haima): blood
Δύναμις (dynamis): power or strength
The study of the movements of blood and the forces concerned herein 1
1 Dorland's illustrated medical dictionary. Philadelphia: Saunders; 2003

Introduction
Circulation in neonates is unique:
Transition from low resistant placental circulation to high resistant systemic circulation
Presence of intra- and extra-cardiac shunts
Underdeveloped regulatory mechanism at the end organs in preterm neonates

Picture from: Kliegman: Nelson Textbook of Pediatrics, 18th ed

Introduction
Adequate blood circulation is necessary for adequate supply of O 2 and other essential nutrients, and to remove toxic metabolic products from all tissues
O 2 supply is dependent on:
Arterial O 2 content
Blood flow
Picture from: www.learnhemodynamics.com/hemo/oxygen.htm

Introduction
Arterial O 2 content
Hemoglobin concentration
Arterial O 2 saturation (SaO 2 )
The limitation of O2 supply monitoring
the ability to monitor blood flow to the tissues

Objective
Review of available methods for monitoring of hemodynamics and end-organ perfusion in neonates.
Identify best evidence-based practice in directing the management of circulatory insufficiency in neonates, achieving hemodynamic stability and avoiding deleterious effect of various interventions.

Part 1 Clinical Monitoring of Systemic Hemodynamics

What do your criteria to diagnose “ circulatory insufficiency” in neonates?

Clinical monitoring of systemic hemodynamics
In questionnaire across Canada: 2
25.8% of the respondents rely on absolute BP values alone when defining hypotension
The remainder combine BP values and clinical signs of perfusion: color, capillary refill time and urine output
87.1% defined hypotension as BP in mm Hg less than gestational age in weeks
2 Dempsey EM, Barrington KJ. Diagnostic criteria and therapeutic interventions for the hypotensive very low birth weight infant. J Perinatol 2006;26:677–81.

Blood Pressure
Hypotension:
BP < the tenth (or fifth) percentile of normative BP values from a reference population with regard to GA, BW, and postnatal age
The lower limit of normal MABP: the numeric value of GA in wks, provided no additional signs exist of hypoperfusion of endorgans
MABP < 30 mm Hg

Blood Pressure
Osborn et al, 2004: 3
Poor correlation between BP and Systemic Blood Flow in preterm infants < 30 wks GA
3 Osborn DA, Evans N, Kluckow M. Clinical detection of low upper body blood flow in very premature infants using blood pressure, capillary refill time, and central–peripheral temperature difference. Arch Dis Child Fetal Neonatal Ed 2004;89: F168–73.

Blood Pressure

Blood Pressure
Groves et al, 2008: 4
Low blood pressure does not correlate with poor perfusion in the first 48 h of postnatal life in sick preterm infants < 30 wks GA
Infant with reduced systemic perfusion (SVC flow < 41 ml/kg/min) tend to have normal or high blood pressure in the first hours of life.
High systemic vascular resistance may lead to reduced blood flow.
4 Groves AM, Kuschel CA, Knight DB, Skinner JR. Relationship between blood pressure and blood flow in newborn preterm infants. Arch Dis Child Fetal Neonatal Ed. 2008 Jan;93(1):F29-32. Epub 2007 May 2.

Heart Rate
In neonate,
It is supposed that cardiac output is almost entirely dependent on HR !!!??

Heart Rate
Kluckow and Evans, 2000: 5
No correlation between HR and systemic blood flow (SBF)
The normal range of SBF: being above the lowest recorded SVC flow at each of the four scans, that is, above 30, 34, 42, and 46 ml/kg/min respectively at 5, 12, 24, and 48 hours of age
5 Kluckow M, Evans N. Low superior vena cava flow and intraventricular haemorrhage in preterm infants. Arch Dis Child Fetal Neonatal Ed 2000;82: F188–94.

Heart Rate

Color
Skin and mucosal membranes color is influenced by:
Oxygenation
Hb concentration
Skin temperature
Skin thickness
Peripheral perfusion
Race
Gestational age
ambient temperature
Light

Color
O'Donnell et al, 2007: 6
Among clinicians observing the same videos there was disagreement about whether newborn infants looked pink with wide variation in the SpO 2 when they were considered to become pink
6 O'Donnell CP, Kamlin CO, Davis PG, Carlin JB, Morley CJ. Clinical assessment of infant colour at delivery. Arch Dis Child Fetal Neonatal Ed 2007;92:F465–7.

Capillary refill time (CRT)
The time required for the return of color after the application of a blanching pressure to a distal capillary bed
Raichur et al, 2001: 7
There was good interobserver agreement when CRT was measured on the chest but not the forehead, palm or heel
7 Raichur DV, Aralihond AP, Kasturi AV, Patil DH. Capillary refill time in term neonates: bedside assessment. Indian J Pediatr. 2001 Jul;68(7):613-5.

CRT > 3 sec had a sensitivity of 55% and a specificity of 80% for predicting low SVC flow

Urine Output
Miletin et al, 2009: 8
There was a poor correlation between the capillary refill time, MBP, urine output and low SVC flow (< 40 ml/kg/min)
8 Miletin J, Pichova K, Dempsey EM. Bedside detection of low systemic flow in the very low birth weight infant on day 1 of life. Eur J Pediatr 2009;168:809–13.

Urine Output

Lactate
⁭ Blood Lactate ≠ Lactic Acidosis
Cause of ⁭ lactate production in neonates:
Anaerobic metabolism (e.g. circulatory failure)
Increased glycogenolysis
Administration of sympathicomimetic drugs
Inborn errors of metabolism.

Lactate
Elevated lactate may be associated with:
Normal pH, acidosis, alkalosis
Normoxia, hypoxia or anoxia
Deshpande and Platt, 1997: 9
There was no correlation between common acid-base parameters such as pH, base excess, bicarbonate concentrations and blood lactate concentrations
9 Deshpande SA, Platt MP. Association between blood lactate and acid–base status and mortality in ventilated babies. Arch Dis Child Fetal Neonatal Ed 1997;76: F15–20.

Lactate
Despite circulatory insufficiency, lactate may not increase when :
Lactate clearance is in balance with lactate production
Oxygen delivery meets the oxygen demand in the tissues by increased oxygen extraction
Lactate may accumulate locally and remain undetectable until perfusion improves

Lactate
Miletin et al, 2009: 8
Serum lactate ≥ 2.8 mmol/l has sensitivity of 100% and specificity 60% for detecting low flow states.
8 Miletin J, Pichova K, Dempsey EM. Bedside detection of low systemic flow in the very low birth weight infant on day 1 of life. Eur J Pediatr 2009;168:809–13.

Lactate

Central–peripheral temp. difference (CPTd)
There was no correlation between CPTd and SVC flow

Central–peripheral temp. difference (CPTd)

Acid–base balance
Kluckow and Evans, 2001: 10
No correlation between low SVC flow and pH or base excess
10 Kluckow M, Evans N. Low systemic blood flow and hyperkalemia in preterm infants. J Pediatr 2001;139:227–32.

Venous oxygen saturation (SvO 2 )
Mixed SvO 2 represents the oxygen reserve after tissue oxygen extraction
SvO 2 depends on:
Arterial O 2 concentration
O 2 consumption
Cardiac output
Hb concentration
Main PA is most optimal site for mixed venous blood sampling

In NB, we can measure central SvO 2
Mixed SvO 2 ≠ Central SvO 2
Difference is influenced by:
Sampling site of central venous blood
Presence of left-to-right shunts
Incomplete mixing of venous blood
Redistribution of blood flow through upper and lower body
Level of consciousness (anaesthesia)
Myocardial O 2 consumption

In healthy adults:
SVC saturation is 2–3% lower than the true mixed venous saturation

In Shock:
The relationship between SVC saturation and mixed venous saturation reverses, with the reported difference ranging from 5–18%
SVC saturation will typically overestimate Mixed SvO 2 , whereas IVC saturation may underestimate it
11 Martin J, Shekerdemian LS. The monitoring of venous saturations of oxygen in children with congenitally malformed hearts. Cardiol Young 2009;19:34–9.

Hart et al, 2006: 12
No linear relationship has been found between IVC SvO 2 , obtained from UVC, and systemic blood flow (SVC flow)
12 Hart J, Vemgal P, Cocks-Drew S, Harrison C, Andersen C. The relation between inferior vena cava oxygen saturation, superior vena cava flow, fractional oxygen extraction and haemoglobin affinity in sick newborns: a pilot study. Acta Paediatr 2006;95:50–5.

de Oliveira et al, 2008: 13
Aiming at a central SvO 2 ≥ 70%, improves outcome of pediatric septic shock
13 de Oliveira CF, de Oliveira DS, Gottschald AF, et al. ACCM/PALS haemodynamic support guidelines for paediatric septic shock: an outcomes comparison with and without monitoring central venous oxygen saturation. Intensive Care Med 2008;34:1065–75.

Combination of different clinical hemodynamic variables de Boode. Clinical monitoring of systemic hemodynamics in critically ill newborns. Early Human Development 86 (2010) 137–141

Conclusion
The clinical assessment of cardiac output by the interpretation of indirect parameters of systemic blood flow is inaccurate , irrespective of the level of experience of the clinician

Conclusion
Using BP to diagnose low systemic blood flow will consequently mean that too many patients will potentially be undertreated or overtreated , both with substantial risk of adverse effects and iatrogenic damage.

Conclusion
Combining different clinical hemodynamic parameters enhances the predictive value in the detection of circulatory failure, although accuracy is still limited.

Conclusion
Variation in time (trend monitoring) might possibly be more informative than individual, static values of clinical and biochemical parameters to evaluate the adequacy of neonatal circulation.

THANK YOU

Monitoring of Neonatal Haemodynamics

by Ayman Abou Mehrem

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