Consultant Paediatric Cardiac Surgeon,
Jaypee Hospital, NOIDA, UP, India
In their publication entitled ‘Elective delayed sternal closure portends better survival after congenital heart surgery’, Drs Simran Kundan et al. present a sizeable experience of a series of 2,111 consecutive congenital heart operations with an overall hospital mortality of 3.7%.The authors are to be complimented for a candid and thorough data retrieval and for tabulating their entire experience, divided into different categories.
Out of the 2,111 patients, there were 206 in whom the sternum was electively left open and in this group, they report a mortality of 11.6% (23 patients). There was an additional smaller group of 14 patients where the patients were shifted from OT with the sternum closed, but who required secondary opening of the chest in ICU for hemodynamic instability. In this group, they report a mortality of 71.4%, which was significantly higher than the elective chest-open group. The authors conclude that if problems can be predicted, it is safer postponing chest closure and shifting the patient to ICU with chest open at conclusion of surgery.
The conclusion reached in the paper makes intuitive sense in that any patient after intracardiac repair, where future hemodynamic compromise is likely, would be better off with the sternum unclosed. The paradigm they followed in deciding when to leave a sternum open in their own words is as follows: ‘In neonates with poor preoperative status, we tend to leave the sternum open in majority of such patients. Empirically our indications include situations in which the pump time and clamp time are long, leading to tissue edema involving the heart and lungs, ventricular dysfunction, medical bleed, any palliated or residual lesions which predispose to a hemodynamically unstable postoperative course requiring high inotropes, situations in which there was a space constraint eg conduit placement or in patients with central ECMO. After closure, the patient is monitored closely for the same flag signs’. In their experience, 55.9% of the patients whose chest were left open were neonates. There were 4 major operations which constitute the bulk of their primarily open and also secondarily opened sternums: the arterial switch operation, repair of TAPVC, aortic arch repairs, and repair of tetralogy of Fallot.
Obviously, despite the above protocol, these 14 patients were missed or developed fresh problems in the ICU, which had not been predicted at the time of proceeding to close the sternum. Six of the 14 were opened for ‘hemodynamic instability’ and it is not clear if this was related to bleeding, cardiac tamponade or primary cardiac dysfunction with 3 survivors, while 6 others were reopened for a cardiac arrest. Of the latter group, 3 were put on ECMO, despite which there were no survivors among these 6. Two patients had sudden arrhythmia and one could be salvaged after reopening.
The authors postulate that presumably, the act of going ahead with sternal closure in these patients negatively impacted their potential chance of survival.
Quite possibly, in my opinion.
For the delay entailed in reaching the decision to reopen and the obvious reluctance to do so having once closed the chest, in an unpopulated hour of the night, after a busy day’s work, can quite likely result in a progressively worsening situation, when one finally does reach the point of reopening a chest. Also, the valuable adjunct of leaving the chest open, i.e. having cannulation tourniquets already in place, is obviously missing in a closed chest, and placing fresh purse strings in a situation where the aorta is behind the anteriorly translocated pulmonary artery (post ASO) or in a diminutive aorta of a TAPVC, when the patient is spiraling out of control or has already had a cardiac arrest, single handedly, can be a daunting exercise to the best in the business.
What if they were to have left the sternum open in all the susceptible groups of patients, i.e. group A2?
The downside of leaving the sternum open, in their own experience, is higher blood stream infection, but no significant increase in local wound infection and an understandably higher time on ventilator, ICU stay and hospitalization. If the entire lot of their group A2 were to have been left open, or even if this was limited to the arterial switches, TAPVC repairs and arch repairs, it would entail a major increase in cumulative morbidity and hospital expenditure and would doubtless be an overkill.
The million dollar question is how do we identify the patient who looks okay, now in the OT, but is going to fall apart in the ICU?
Leaving the sternum open primarily is an option exercised by most units doing cardiac, and, especially, pediatric and, more so, neonatal cardiac surgery. ‘Tight syndrome’ is a well-recognized phenomenon in patients soon after having undergone neonatal cardiac surgery and results more often with prolonged cardiopulmonary bypass and ischemic times, especially after certain specific operations, e.g. arterial level repair of transposition of the great arteries, patients with obstructed total anomalous pulmonary venous drainage, or relief of aortic arch obstruction with or without concomitant intracardiac repair or stage I Norwood repair.
In general, significant oozing, borderline hemodynamics, bulging heart, hyperinflated lungs that would also take up space once the sternum is closed, higher than normal airway pressures and low central venous saturations in any patient are some of the prescribed indices to consider when deciding to close a sternum or not. In Dr. Kundan’s group’s experience, mixed venous saturation (MVO2) is not mentioned, as an index that was measured when taking this decision. In my opinion, this particular parameter, if one does not have access to near-infrared spectroscopy (NIRS) of the abdomen, needs to be looked at seriously, and may have a role in helping one take a call when all else suggests closeability.
Similarly, having been received in the ICU with sternum closed, any patient whose abdominal NIRS or mixed venous saturation drifts low (MVO2 below 50%) would probably be better off with more space for lung expansion and cardiac filling, as the next step after optimizing inotropy and preload. This index, if followed serially in the ICU, may assist more timely intervention than other more conventional parameters mentioned earlier. If after this intervention, too, the situation still does not seem to improve, then arrangements for mechanical circulatory support as the final strategy for prevention of impending cardiac collapse can be readied.