ST. PETERSBURG, FLA. – Critical care phases for patients with hypoplastic left heart syndrome include both the immediate postoperative period and the recovery period prior to discharge, according to Dr. Peter C. Laussen.
In the immediate postoperative course, critical care largely comes down to a fundamental concern for all critical care patients: the balance between oxygen delivery and oxygen consumption, he said at the Annual International Congenital Heart Disease Symposium.
This is true regardless of the surgical approach to HLHS – which can have its own unique critical care considerations.
“We need to optimize oxygen delivery and minimize oxygen consumption; we need to get that balance correct,” said Dr. Laussen of Children’s Hospital Boston.
This requires continuous monitoring, integration, and interpretation of data – particularly in the rate of change, he added.
Careful attention should be paid during the transfer from the operating room to the cardiac intensive care unit, which is a critical period, he said, noting that surgeons do an important job of “setting the patient up” for the transition, such as by ensuring ultrafiltration in the operating room, peritoneal dialysis catheter placement, electively leaving the sternum open, and providing access via an internal jugular line for the short term and/or a double-lumen right atrium Broviac catheter for the longer term.
“Then we’re left to use indirect measurement to really determine the balance between supply and demand,” he said.
These measurements include:
- Clinical examination, because “continued review of clinical findings is absolutely vital and a skill that needs to be reinforced and continually taught,” he said.
- Pulse width, which needs to be followed very closely, Dr. Laussen said, adding that this is a variable that often isn’t paid enough attention.
- Mixed venous oxygen saturation, which should be used if there is a catheter. Data show that continuous monitoring is associated with improved early survival and lower incidence of end-organ failure.
- End-tidal CO2, which is mandatory on every ventilated patient, he said, adding that the gradient must be known because it provides an index of what is happening with pulmonary blood flow.
- Serum lactate, which is routinely measured in these patients. The rate of change over time has been shown to be positively correlated with predictive value of mortality and morbidity.
- Cerebral and somatic near infrared spectroscopy, which is becoming a standard of care in this group of patients, he said. Findings need to be interpreted in light of all other findings in the patient, with careful attention to the rate of change, which is the critical finding, he noted.
- Clinical examination, because “continual updating of clinical examinations is absolutely vital and a skill that needs to be reinforced and continually taught,” he said.
- Pulse oximetry. This is the most common continuous, yet indirect, variable that everybody tracks and utilizes to make management decisions, Dr. Laussen said.
Once again, interpreting change is most important. There can be a great deal of variability in oxygen saturation following stage I palliation in these patients with functional single ventricular physiology, and it is “very critical to appreciate” the variability, he said.
Changes in SpO2 may be due to one of three things: alteration in pulmonary blood flow, pulmonary venous desaturation, and change in arterial oxygen content, he said.
Minimizing oxygen demand is a very important part of the equation, he said, noting that dopamine has been reported to increase myocardial oxygen consumption secondary to the associated increase in heart rate in these patients, and termination of dopamine is associated with improved oxygen consumption/oxygen delivery balance.
“This has changed our practice. We still use dopamine as our first-line inotrope, but go no higher than 10 [mcg/kg per minute], prefer to stay around 5 [mcg/kg per minute], and go very early to epinephrine,” he said, explaining that epinephrine is a very good inotrope and does not have the detrimental effects seen with dopamine.
As for the “recovery prior to discharge” period in these patients, this should also be considered a critical care phase, he said. This is a time of transfer to the floor, where a new team takes over. There’s a different thought process, and the new team has not seen what has transpired in the prior 1-2 weeks. Additionally, many changes take place in the management of the patient: Monitoring and surveillance may be reduced, efforts are made to advance nutrition, dosages (such as in diuretics) are changed, and anticoagulation practices are variable, he said, noting that “it’s very easy to unravel these patients” during this period.
“We have to be paying close attention to how we continue to follow these patients to avoid readmission to the ICU and the sudden untoward event that can still occur on the floor prior to discharge,” he said.