**5. Conclusions**

*Advances in Complex Valvular Disease*

*4.3.3 Respiratory management*

upon during inspiration [3].

rest and during exercise [23].

Right-to-left shunts become important causes of hypoxemia. Acute elevation of PVR may cause right-to-left shunting across a fenestration or a baffle leak with the consequent drop in the saturation of the patient. PVR may be decreased acutely with hyperventilation (pCO2 30 mmHg or pH 7.45) and increasing concentrations of oxygen. Usual sources of hypoxemia in the perioperative period such as endobronchial intubation, bronchospasm, and atelectasis always should be considered.

The circulatory arrangement of the Fontan amplifies the effects of respiratory mechanics upon venous return. Negative intra-thoracic pressure augments the antegrade flow from the SVC, IVC, and hepatic venous circulation into the pulmonary arterial tree. The work of breathing is a significant additional energy source to the circulation in these patients. Normal negative pressure inspiration has been shown to increase pulmonary blood flow in patients after the TCPC [3]. Physiologically there is a correlation between total hepatic venous flow and respiration. During inspiration there is marked increase in hepatic venous contribution to the total venous return, due to a dual effect on venous pressure and compression of the liver by diaphragmatic decent. The liver acts as a sump of blood which can be drawn

Magnetic resonance flow measurements have shown that approximately 30% of the CO can be directly attributed to the work of breathing in patients after the TCPC [3]. In Fontan patients, inspiration resulted in increased ventricular filling at

The opposite happens with positive pressure ventilation (PPV). It has long been known that increasing levels of positive end-expiratory pressure (PEEP) during PPV are adverse to the Fontan circulation. The available data suggests a linear relationship between mean airway pressure and CI in these patients: the higher the mean airway pressure, the lower CI [3]. This can be explained by the effect of lung volumes on PVR, since both over-distention and collapse of alveoli, result in increases in PVR. The management of these patients should therefore be directed towards minimizing mean airway pressure when these patients are being ventilated for cardiac and noncardiac procedures. Also, an early postoperative restoration of normal

Adjustments to minimize positive intra-thoracic pressure can be made using minimal PEEP, smaller tidal volumes, pressure-regulated ventilatory modes, or spontaneous ventilation with minimal pressure support [18], and avoid prolonged Valsalva maneuvers. One should maintain these patients with the minimum mean airway pressure compatible with normal oxygenation and adequate alveolar ventilation. A sound strategy when using PPV would be to adjust ventilatory parameters that allows to achieve the lowest mean airway pressure, moderate alkalosis (pH 7.45, pCO2 35 mmHg), and one that reduces the risk of atelectasis. Fontan patients have tolerated PPV with minimal hemodynamic effects as long as proper ventilatory settings are used. Furthermore, it has been proposed that monitored anesthesia care without adequate ventilation may be more detrimental than the physiologic effects

Fontan patients pose a particular clinical challenge for the anesthesiologist due to their abnormal physiology and high risk for adverse events. Pre-existing chronic end-organ dysfunction makes these patients susceptible to acute exacerbation or organ failure [18]. Information of baseline cardiac function and hemodynamics

negative pressure ventilation can be beneficial in these patients.

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of PPV per se [5].

*4.3.4 Circulatory management*

• Since prognosis of patients with univentricular heart has improved significantly in recent decades, this has resulted in the general anesthesiologist being able to meet at some point in his professional practice with this type of patients, whether to perform a noncardiovascular diagnostic or therapeutic procedure or noncardiac surgery. Therefore, the anesthesiologist must have an appropriate knowledge of Fontan's anatomy and physiology as well as those patients with failed Fontan in order to provide them with a correct preoperative evaluation and an adequate intraoperative and postoperative management, and to obtain the best results, thus achieving a better survival and quality of life in this population group.

