**5.2.2 Right to left**

62 Perioperative Considerations in Cardiac Surgery

Transcranial near-infrared spectroscopy (NIRS)17 is a sensitive measure of regional hypoperfusion. It measures all haemogloblins and useful in non pulsatile cardiopulmonary bypass and circulatory arrest. Cerebral oximeter detects intravascular haemoglobin oxygen

Intraoperative transesophageal echocardiography (TEE) plays a critical role in improving surgical outcome in CHD surgeries by confirming diagnosis and identifying residual defects. It is also helpful in the placement of devices in catheterization lab. Micromultiplane TEE probe and three dimensional technologies are new advances in echocardiography. Epicardial echocardiography is an alternative option in institutions where smaller TEE probe is not available18. Adult TEE probe can be used in patient

Arterial blood gases and blood glucose should also be done frequently. Tight blood glucose

Anaesthetic management during surgery depends on presence or absence of shunt, pulmonary hypertension, hypoxaemia, Ventricular dysfunction, pulmonary flow and

Shunting through these defects depends upon diameter of defect and balance between systemic and vascular resistance. Balance between systemic vascular resistance (SVR) and pulmonary vascular resistance (PVR) is essential in the anaesthetic management of patient

Normal pulmonary: Systemic ratio (Qp:Qs ratio) is 1:1 which indicate either no shunting or bidirectional shunt of equal magnitude. Qp:Qs ratio of 2:1 indicate left to right shunt while less than 1:1 ratio (0.8:1) means right to left shunt. The ratio is estimated from oxygen saturation measurements at pulmonary veins, pulmonary artery, systemic arterial and

L –R shunt reduces greatly with drop in SVR or an increase in PVR. It leads to excess pulmonary blood flow. Patients are usually acynotic but deterioration in gas exchange may result from pulmonary congestion. Avoid 100% oxygen and hyperventilation in patients

control is suggested by certain authors as high blood sugar is toxic to mitochondria.

**5.1.5 Cerebral oximeter** 

saturation of cerebral cortex.

**5.1.6 Echocardiography** 

weighing more than 20Kg.

**Intraoperative management** 

arrhythmia.

**5.2 Shunt** 

with shunts.

mixed venous blood.

with L R shunt.

**5.2.1 Left to right shunt**  1. Atrial septal defect (ASD) 2. Ventricular septal defect (VSD) 3. patent ductus arteriosus (PDA) 4. Atrio ventricular (AV) canal defects

5. Complete anamolous venous return (CAVR) 6. Partial anomalous venous return (PAVR) 7. Artificial Blalock taussig (BT shunt)

These intra cardiac shunts lead to prolong inhalation induction. **R L shunt** (e.g. tetralogy of fallot (TOF) or shunt reversal12 occur when SVR drops or PVR increases. Hypercyanotic spell under anaesthesia will respond to volume, Increase SVR with alpha agonists such as Phenylephrine.
