Outcomes in General Anaesthesia versus Sedation
Levels of sedation can vary with the drugs being used, the response of those drugs by the patients, their co-morbidities, and lifestyle/social history such as alcohol use. Sedation can range from minimal to conscious to deep should be performed by a clinician experienced in the use and monitoring of patients under anaesthesia.
Table 2 shows the American Society of Anaesthesiologists Definition of General Anaesthesia and Levels of Sedation/Analgesia
Renner et al studied the outcomes of patients at a single centre undergoing TAVI with either GA or Conscious sedation (CS) with anaesthesia performed by two experienced cardiac anaesthesiologists. Both groups used low dose midazolam IV (intravenous) at 0.01-0.02 mg/kg prior to the procedure. Both groups had an arterial line and central venous catheter. Patients in the GA groups had either an endotracheal intubation or a laryngeal mask airway (LMA). Those who had an endotracheal intubation were able to have transoesophageal echocardiography (TOE), whereas those with a LMA and in the CS group had transthoracic echocardiography (TTE) before and after the procedure. Total intravenous anaesthesia (TIVA) was used in the GA group with either a bolus of propofol or etomidate on induction followed by continuous infusion of propofol (3-5 mg/kg/hr) and remifentanyl (0.3-0.4 mcg/kg/min) and rocuronium as a muscle relaxant. The CS group used much lower doses of propofol (0.3-0.5 mg/kg) and remifentanyl (0.02-0.06 mcg/kg/min) and 5-10 ml of 1% Mepivicaine was infiltrated to the groin at the site of vascular access. 107 patients were in the GA group with a mean age of 82 (6.1) years, and 93 patients in the CS group with a mean age of 82 (6.4). There was no difference between groups in terms of co-morbidities, New York Heart Association (NYHA) classification or LogEuroSCORE. Conversion from CS to GA was needed in 5 cases: 4 due to procedural complications and 1 due to agitation. Mean anaesthesia time was significantly longer in the GA group, as expected more anaesthetic agents such as propofol was used up in the GA group and so the need to reach haemodynamic stability with the use of vasopressors and IV fluids were more common in the GA group. Lower mean arterial pressure (MAP) was noted in the GA group. Shorter intensive care unit (ICU) stays were noted in the CS group, though there was no difference in length of stay in hospital between the groups. There was no significant different in 30-day mortality between the groups. Even in those who were high risk with a LogEuroSCORE >22 there was no difference in intra-procedural characteristics between groups. 9.3% patients all of whom were in the GA group required cardiopulmonary resuscitation. [6]
Husser et al studied the outcomes of patients receiving TAVI with the support of either GA or LA or CS (LACS). 16543 patients from multiple centres across Germany were enrolled, mean age was 81 years and LACS was used as the primary approach in 49% of cases. LACS was more likely to be conducted in experienced TAVI centres. Procedural success was achieved in 97.5%. The LACS group showed shorter procedural duration and fluoroscopy time. Conversion to sternotomy and bleeding complications were less frequent in the LACS group, though vascular complications were higher. Rate of device embolization and malposition was less in the LACS group. There was no difference in paravalvular leak (PVL) between groups. Post procedural course was less complicated in the LACS group such as delirium, respiratory failure, CPR. Duration of ICU and hospital stay was shorter in the LACS group in population matched analysis. 30-day mortality was less in the LACS group, though there was no significant difference at 1 year mortality. [7] Miles et al in a single centre study looked at the outcomes of GA and CS in patients enrolled for TAVI. CS involved a remifentanyl infusion at 0.05 mcg/kg/min with a fascia iliaca block ilioinguinal block using 2 mg/kg 0.25% levobupivacaine. 118 patients were involved with 44 receiving CS. There was a 17% reduction in anaesthetic time and a 29% reduction in recovery room time in the CS group. Reduction in inotrope requirement was seen in the CS group and no difference were seen in terms of postprocedural complications between groups. 7% from the CS group required ICU admission with one due to respiratory failure needing tracheal intubation. 14% in the GA group need ICU admission. 4 patients required conversion to GA. [8] Goren et al in a single centre study involving 204 patients undergoing TAVI found significantly less use of catecholamines and intravenous fluids in patients received sedation over GA. Total procedural times were also less. Conversion to GA occurred in 4.6%. In hospital mortality and total length of stay were similar between groups. [9]
Thiele et al performed a multi-centre randomised trial (SOLVE trial) of patient undergoing TAVI with either GA or CS with LA. Patient included had severe AS, age >75 years and high risk for surgical valve replacement. GA was provided via TIVA with continuous infusion of propofol and remifentanyl maintaining a BIS of 40-60. LA was provided by the interventionalist. CS was given either by dexmedetomidine, propofol or other nonbenzodiazepine drugs and titrated to keep BIS >70. Ventilation was monitored with capnography and supplemental oxygen was given. 225 patients were randomly assigned to the GA group and 222 to CS. Mean age was 81.6+/-5.5 years, a median logEuroSCORE of 14.8% and similar baseline characteristics between groups. Conversion to GA from CS occurred in 5.9% with the reasons being the need for CPR, respiratory insufficiency, and agitation. Minimum oxygen saturation during anaesthesia and cerebral oxygen saturation at the end of the procedure was significantly lower in the CS group. As expected, the quantity of anaesthetic agents used were greater in the GA group. At 30 days the rate of the composite primary end point of all cause mortality, stroke, myocardial infraction, acute kidney injury was similar between groups. Device time, procedural time, POD, moderate to severe prosthetic valve regurgitation at 30 days and cardiovascular mortality did not differ significantly between groups. Mean length of ICU and hospital stays were similar. The need for vasopressor and inotropes were greater in the GA group. [10]