**4.1.3 Post-capillary**

#### **Left heart disease**

Left and right ventricular functions are interdependent. All LV function abnormalities induced by coronary artery disease, congestive heart failure, valvular heart disease, or systemic hypertension will influence RV function through ventricular interdependence mainly through an effect on the interventricular septum. Hence, a dilated LV and left atrium can shift the interatrial and interventricular septum and compress the right atrium and ventricule and reduce RV end-diastolic volume.

Fernandes *et al*. (Fernandes et al., 2011) compared iNO to oxygen in 29 patients with PH after MVR. Treatments were initiated for 48 hours immediately after surgery. After 24 and 48 hours, patients receiving iNO had a significantly greater increase in CI compared to patients receiving oxygen (p <0.0001). Pulmonary vascular resistance was also more significantly reduced in patients receiving iNO versus oxygen (p = 0.005) at 48 hours. Patients in the iNO group required less systemic vasoactive drugs and had a shorter ICU stay (p = 0.02).

Kim *et al*. (Kim et al., 2010) compared the pulmonary vasodilation effect of combined preoperative oral sildenafil (50 mg) and beraprost (40 µg) (pulmonary vasodilators) to placebo in 50 patients scheduled for valvular heart surgery with PH (MPAP > 30 mmHg). Medication was initiated 15 min before the induction of anesthesia. The treatment group had a significantly lower systemic vascular resistance index (SVRI) at 60 min after medication. No other significant intergroup differences in hemodynamic variables were observed. In addition, significantly more patients in the treatment group required vasopressor therapy. In both groups, the PAP was significantly reduced by general anesthesia, and almost normalized after valvular heart surgery. The combination of preoperative oral sildenafil and beraprost treatment resulted in a loss of pulmonary selectivity, and did not provide any additional pulmonary vasodilation or benefits perioperatively.

Wang *et al*. (Wang et al., 2009) investigated the postoperative effects of inhaled milrinone in 48 patients with PH undergoing MVR. Patients were randomly assigned to receive inhaled milrinone (nebulized for 4 hours) or intravenous milrinone (control group bolus of 50 microg/kg i.v. milrinone and then received a continuous milrinone infusion, 0.5 microg/kg/min, for 4 hours) After milrinone administration, MPAP and PVR showed a comparable decrease in both groups. However, both mean MPAP and SVR in the inhaled group were significantly higher than in the control group. MPAP and PVR returned to baseline values 60 minutes after termination of milrinone inhalation. In addition, in the inhaled group, there was a reduction in intrapulmonary shunt fraction (Qs/Qt), with an improvement in arterial oxygen tension/fraction of inspired oxygen (PaO2/FiO2).

elimination of ventilation/perfusion mismatch from and atelectasis can also help control

Chest drainage is required in patients with elevated intrathoracic pressure resulting from accumulated air or blood. However, chest closure may be associated with hemodynamic instability in patients requiring long procedures associated with prolonged CPB due to myocardial edema. The solution to this "thoracic compartment syndrome" consists in leaving the chest temporarily opened in order to reduce surrounding pressures until edema

Left and right ventricular functions are interdependent. All LV function abnormalities induced by coronary artery disease, congestive heart failure, valvular heart disease, or systemic hypertension will influence RV function through ventricular interdependence mainly through an effect on the interventricular septum. Hence, a dilated LV and left atrium can shift the interatrial and interventricular septum and compress the right atrium and

Fernandes *et al*. (Fernandes et al., 2011) compared iNO to oxygen in 29 patients with PH after MVR. Treatments were initiated for 48 hours immediately after surgery. After 24 and 48 hours, patients receiving iNO had a significantly greater increase in CI compared to patients receiving oxygen (p <0.0001). Pulmonary vascular resistance was also more significantly reduced in patients receiving iNO versus oxygen (p = 0.005) at 48 hours. Patients in the iNO group required less systemic vasoactive drugs and had a shorter ICU

Kim *et al*. (Kim et al., 2010) compared the pulmonary vasodilation effect of combined preoperative oral sildenafil (50 mg) and beraprost (40 µg) (pulmonary vasodilators) to placebo in 50 patients scheduled for valvular heart surgery with PH (MPAP > 30 mmHg). Medication was initiated 15 min before the induction of anesthesia. The treatment group had a significantly lower systemic vascular resistance index (SVRI) at 60 min after medication. No other significant intergroup differences in hemodynamic variables were observed. In addition, significantly more patients in the treatment group required vasopressor therapy. In both groups, the PAP was significantly reduced by general anesthesia, and almost normalized after valvular heart surgery. The combination of preoperative oral sildenafil and beraprost treatment resulted in a loss of pulmonary selectivity, and did not provide any additional pulmonary vasodilation or benefits

Wang *et al*. (Wang et al., 2009) investigated the postoperative effects of inhaled milrinone in 48 patients with PH undergoing MVR. Patients were randomly assigned to receive inhaled milrinone (nebulized for 4 hours) or intravenous milrinone (control group bolus of 50 microg/kg i.v. milrinone and then received a continuous milrinone infusion, 0.5 microg/kg/min, for 4 hours) After milrinone administration, MPAP and PVR showed a comparable decrease in both groups. However, both mean MPAP and SVR in the inhaled group were significantly higher than in the control group. MPAP and PVR returned to baseline values 60 minutes after termination of milrinone inhalation. In addition, in the inhaled group, there was a reduction in intrapulmonary shunt fraction (Qs/Qt), with an

improvement in arterial oxygen tension/fraction of inspired oxygen (PaO2/FiO2).

PH.

recedes.

**4.1.3 Post-capillary Left heart disease** 

stay (p = 0.02).

perioperatively.

ventricule and reduce RV end-diastolic volume.

A study by Fattouch *et al*. (Fattouch et al., 2005) evaluated the effects of inhaled prostacyclin iPGI2 and iNO and compared them with those of conventional intravenous vasodilators (i.e. NTG and nitroprusside) in 58 patients with PH (PVR > 250 dyn·sec·cm-5 and MPAP > 25 mmHg) suffering from severe mitral valve stenosis. Both drugs were administered by inhalation 5 min before weaning from CPB and continued in the ICU for up to 2 hours. Significant decreases in MPAP and PVR, as well as increases in CO and RVEF, were noted in both inhaled groups, which was not the case in the conventional group. Furthermore, patients in the inhaled groups showed easier separation from CPB, lower requirements for vasoactive drugs and shorter ICU and hospital lengths of stay.

The same investigators also compared the same three strategies in 58 patients with mitral valve stenosis and elevated PVR (>200 dyn·sec·cm-5 and/or a transpulmonary gradient (MPAP-PAOP)>10 mmHg) after MVR (Fattouch et al., 2006). Intravenous nitroprusside (5– 15 g/min), iPGI2 (10 g/min) or iNO (20 ppm) were started immediately after patient admission to the ICU. Reduction in MPAP, PVR, and transpulmonary gradient were observed in all groups. Only iPGI2 was associated with a significant increase in stroke volume and CO. Administration of nitroprusside was associated with a reduction in SVR and occurrence of systemic hypotension.

Feneck *et al*. (Feneck et al., 2001) compared milrinone to dobutamine in 120 patients with PAOP > 10 mmHg and low output syndrome after CBP (CO < 2 L/min/m²). In a subset of patients with PH (PVR > 200 dyn·sec·cm-5; MPAP > 25 mmHg), milrinone and dobutamine had similar effects in reducing PVR and increasing CI. However, milrinone was more effective in reducing PAOP and systemic vascular resistance (SVR).

Finally, in 20 patients scheduled for mitral valve surgery with PH (MPAP > 25 mmHg), Hachenberg *et al.* (Hachenberg et al., 1997) explored the role of enoximone compared to a combination of NTG and dobutamine, given after induction of anesthesia and then restarted before the end of CPB. Only enoximone was associated with a decrease in MPAP and PVR.

In the presence of PH secondary to LV failure, intra-aortic balloon counterpulsation may facilitate LV recovery.

## **Patient-prosthesis mismatch (PPM)**

In the presence of prosthetic valve dysfunction after CPB, returning under CPB to correct the problem is considered the treatment of choice (Fig. **9**).
