Preoperative optimization of the high-risk surgical patient

Barrier function of the gut and multiple organ dysfunction after cardiac surgery

We studied the influence of sequential involvement of the gastrointestinal (GI) tract on the development of multiple organ dysfunction (MOD) after cardiopulmonary bypass (CPB). One hundred and forty-six patients undergoing elective cardiac surgery were included in this prospective observational study. Standardized oral inert-sugar tests (sucrose, lactulose, mannitol, sucralose) were performed before and after CPB in different patients. Enzyme-linked immunosorbent assay of plasma levels of endotoxin core antibodies (EndoCAb) were performed peri-operatively. The functional mucosal surface was calculated from the amount of mannitol absorbed from the GI tract. Lower urine concentrations of absorbed mannitol were observed pre-operatively in patients developing MOD. In binary logistic regression this was an independent parameter. Decreased plasma concentrations of EndoCAb after surgery were seen in every patient, but were more significant in patients developing MOD. A reduced pre-operative functional mucosal surface may predict the early occurrence of MOD after surgery.

Performing perioperative optimization of the high-risk surgical patient

Perioperative risk of death after general surgery is quoted as overall less than 1%. However, each individual's risk varies widely according to many identified factors with some having a significantly increased risk of a worse outcome. The observation that manipulating and targeting certain physiological parameters in selected patients can influence this risk has been reported in numerous studies. Yet it is still not widely practised to assist the process, despite the availability of various invasive and non-invasive monitors. This may be in part because of a lack of experience with the practicalities of perioperative optimization, and lack of knowledge in applying currently available tools. This article aims to try and address this deficit and increase awareness of how and when to utilize monitoring equipment to achieve optimal results for the patients we treat.

High-Risk Mitral Valve Surgery: Perioperative Hemodynamic Optimization with Nesiritide (BNP)

BACKGROUND

Nesiritide is a recombinant brain-type natriuretic peptide (BNP), which decreases pulmonary arterial (PA) pressures and myocardial oxygen consumption while increasing coronary flow and urine output. Mitral valve (MV) surgery in patients with severe mitral regurgitation (MR), impaired left ventricular function, and pulmonary hypertension is associated with a high operative mortality. We hypothesized that the perioperative use of Nesiritide is safe, and may improve surgical outcomes.

METHODS

From May 2003 to August 2004, 14 patients (11 male, 3 female; mean age, 64 years [23-87 years]; mean systolic PA, 63 mm Hg [48-94 mm Hg]; mean ejection fraction, 36% [10-50%]), undergoing MV surgery (10 repairs, 2 replacements, and 2 rereplacements) for severe MR, were treated for a median of 24 hours (13-55 hours) preoperatively with intravenous Nesiritide. Expected mortality by EuroSCORE was 26% (7.8-59%) (5 reoperations). Concomitant procedures included tricuspid valve repair (n = 7), coronary artery bypass grafting (n = 5), and left atrial maze procedure (n = 3). Eleven patients received Nesiritide postoperatively during a mean duration of 22 hours (2-80 hours).

RESULTS

Operative mortality was 0%. Prior to surgery after BNP treatment, mean systolic PA pressure dropped to 39 mm Hg (p = 0.0003), pulmonary capillary wedge pressure to 15 mm Hg (p = 0.001), central venous pressure to 6 mm Hg (p = 0.002), and weight by 3.7 kg (p = 0.006). Postoperative median ventilation time was 14 hours (4-48 hours). All other major hemodynamic parameters (systemic blood pressure, heart rate, and cardiac output) remained constant. The treatment was well-tolerated in all patients.

CONCLUSIONS

Perioperative use of Nesiritide is safe, and may contribute to improved early outcomes in high-risk patients undergoing MV surgery. This may be due to improved ventricular loading conditions (decreased PA pressures, more effective diuresis) and/or a direct myocardial effect of BNP. Further prospective evaluation of the role of BNP in cardiac surgery is warranted.