Trans-apical aortic valve replacement is a new treatment for severe aortic stenosis. It is offered to elderly patients with medical problems that would markedly increase the risk of conventional cardiac surgery. The rate of delirium (acute confusional state) after surgery in these patients may exceed 50%. Estimated hospital costs associated with delirium at Toronto General Hospital last year exceeded $1-million CAD. Pain after surgery and the use of opioids (morphine type of pain-relief drugs) are known to increase the risk of delirium. The investigators plan to minimize the use of opioids and improve pain management by replacing the standard intravenous opioid-based pain management with the paravertebral nerve block using only the local anesthetic. These two management strategies will be compared with respect to the rate of delirium, duration of hospital stay, and the overall costs.

Hypothesis: Paravertebral analgesia with LA decreases the incidence of delirium after trans-apical AVR when compared to standard systemic opioid-based analgesia.

A prospective, randomized, controlled, multicentre study (Toronto General Hospital and Sunnybrook Health Science Centre, Toronto, Canada.) The investigators are planning to replace the standard intravenous opioid analgesia with a continuous paravertebral block using local anesthetic after trans-apical aortic valve replacement.

Anesthesia management will be standardized to minimize any impact that anesthetic type may have on neurological outcomes.

Metrics to evaluate outcomes: Assessment of delirium will be performed utilizing the CAM-ICU preoperatively (baseline) and postoperatively every 12 hours or as needed according to the patient's condition during the first 7 postoperative days or until discharge.

The CAM recognizes both, hyperactive and hypoactive, forms of delirium. It includes four-step algorithm and assesses 1) an acute onset of changes or fluctuations in the course of mental status, 2) inattention, 3) disorganized thinking and 4) an altered level of consciousness. The patient is determined to be delirious (CAM positive) if he/she manifests both features 1 and 2, plus either feature 3 or 4.

Primary screening for delirium will be performed by the nursing staff. Diagnose of delirium will be confirmed by the psychiatry consult. Assessment of Sedation and Pain: Standardized according to institutional guidelines.

Cost Calculations: The total cost (summation of direct-variable, direct-fixed, and overhead costs) for each patient will be determined for both study groups.

Inclusion Criteria:

• Consenting subjects who are scheduled to undergo the TAVI surgical procedure

Exclusion Criteria:

• patients with symptomatic cerebrovascular disease,
• history of delirium and schizophrenia