Optimal pulmonary to systemic blood flow ratio for best hemodynamic status and outcome early after Norwood operation.
OBJECTIVE
Imbalances of pulmonary to systemic blood flow ratio (Q(p)/Q(s)) compounded with inadequate systemic oxygen delivery correlate with mortality after first-stage Norwood palliation of hypoplastic left heart syndrome. Mathematical models suggest that maximal systemic oxygen delivery occurs with Q(p)/Q(s) of less than 1. Whether this applies to clinical practice is unclear. This study evaluates the level of Q(p)/Q(s) that correlates with best hemodynamic status in the first 48 postoperative hours.


METHODS
Hemodynamic data of 25 consecutive patients who underwent Norwood procedure from October 2002 to January 2005 were retrospectively analyzed. Data included, in particular, systemic venous and arterial oxygen saturation (SvO(2) and SaO(2), respectively), Q(p)/Q(s), lactate levels, and doses of required inotropes. Parameters were recorded 3 hourly. Data were assigned to three groups according to their corresponding Q(p)/Q(s): Groups 1, 2, and 3 for Q(p)/Q(s)< or =1, Q(p)/Q(s) between 1 and 2, and Q(p)/Q(s)> or =2, respectively. Thereafter, independent t-test or Fisher's exact test was used to reveal significant differences. Q(p)/Q(s) ratios and lactate levels were compared in hospital survivors and non-survivors.


RESULTS
Out of 343 samples, 110, 184, and 49 were assigned to groups 1, 2, and 3, respectively. Group 1 (Q(p)/Q(s)< or =1) was characterized by lower SaO(2) (p<0.001) with similar SvO(2) (p=0.3 and p=0.5) and, therefore, higher systemic oxygen delivery (arteriovenous oxygen saturation difference, p<0.001; oxygen excess factor, p<0.001) compared to groups 2 and 3. However, lower mean arterial pressure (p=0.07 and p<0.001), higher lactate levels (p=0.009 and p=0.01), and norepinephrine doses (p=0.006 and p<0.001) highlighted worse hemodynamics. The best hemodynamic status corresponded to group 2. Q(p)/Q(s) remained above 1 in 21 survivors and was, most of the times, below 1 in four patients who died. Lactate levels were almost always above 4 mmol/l or increasing in non-survivors.


CONCLUSIONS
Maximum oxygen delivery after Norwood operation occurs at Q(p)/Q(s) of less than 1. However, optimal hemodynamic status and end-organ function and higher survival correlates with Q(p)/Q(s) between 1 and 2. Thus, Q(p)/Q(s) should be targeted at 1.5 for improved course early after first-stage Norwood palliation.
Photiadis
Joachim
J
Department of Paediatric Thoracic and Cardiovascular Surgery, German Paediatric Heart Institute, Arnold Janssen-Strasse 29, D-53757 Sankt Augustin, Germany. photiadis@gmx.de
Sinzobahamvya
Nicodème
N
Fink
Christoph
C
Schneider
Martin
M
Schindler
Ehrenfried
E
Brecher
Anne Marie
AM
Urban
Andreas E
AE
Asfour
Boulos
B
D006439:Hemodynamics; D017052:Hospital Mortality; D006801:Humans; D018636:Hypoplastic Left Heart Syndrome / Q000097:blood / Q000503:physiopathology / Q000601:surgery*; D007223:Infant; D007231:Infant, Newborn; D019344:Lactic Acid / Q000097:blood; D010092:Oximetry; D010100:Oxygen / Q000097:blood; D010102:Oxygen Inhalation Therapy; D011182:Postoperative Care / Q000379:methods*; D011652:Pulmonary Circulation; D012039:Regional Blood Flow; D012189:Retrospective Studies; D016896:Treatment Outcome
D019344:Lactic Acid; D010100:Oxygen