Airway and chest anatomy should be suitable for insertion of a double lumen tube to facilitate OLV. patient having documented difficulty with intubation, major scoliosis, or emphysematous chest may be identified in the preoperative clinic as unsuitable for this type of surgery. Patients with severe chronic obstructive pulmonary disease (COPD) or asthma will also be poor candidates for prolonged OLV.
External defibrillator pads are applied before induction of anesthesia.
Anaesthesia for robotic cardiac surgery
Anaesthesia For Robotic Cardiac Surgery Presented by- Dr. Tanuja Moderator- Dr. Indu Verma
Introduction• Robotic surgical technology was developed with the idea of performing remote operations and procedures in difficult spaces.• These machines allow surgical maneuvers to be performed by instruments on robotic arms that are controlled by the operator from a console situated away from the operating table.• A slow stepwise approach to learning completely endoscopic techniques is mandatory .• cardiac anesthetists to have a working knowledge of these systems to formulate an anesthetic plan, recognize potential complications, provide safe patient care and adapt to the fast developing field.
History• In May 1998, Dr. Friedrich using the da Vinci Surgical System performed the first robotically assisted heart bypass.• In 1998, Loulmet et al performed the world’s first totally endoscopic coronary arterybypass (TECAB) procedure using robotic assistance• September 1999, Dr. Wolf and Michler - first robotically assisted heart bypas.• In October 1999 the worlds first surgical robotics beating heart coronary artery bypass graft (CABG) was performed by Dr. Douglas Boyd using the ZEUS surgical robot.• In November 1999 – the first closed-chest beating heart cardiac hybrid revascularization procedure is performed (London)• In May 2006 the first AI doctor-conducted unassisted robotic surgery on a 34 year old male to correct heart arrhythmia.
Benefits of Minimally Invasive Heart Surgery• Minimally invasive heart surgery offers several advantages compared to open-chest procedures, including:• Faster return to normal activities. patients can return to work usually within three weeks.• Shorter hospital stay.• No splitting of the breastbone.• Smaller incisions.• Quicker resolution of pain.• Elimination of the heart-lung bypass machine, in most cases.• Minimal blood loss and less need for transfusion.• Little scarring.
• Two surgical robotic systems are in use today: Zeus Surgical System (Computer Motion, California, USA) da Vinci Surgical System (Intuitive Surgical, California,USA).
The da Vinci System• consists of three parts-I. The control console.II. An instrument tower.III. The robot with three arms (four arms in the new version).
Robotic cardiac surgery procedure The surgeon is seated to the left at the da Vinci console, where he controls the systems robotic arms to perform the surgery. The robotic arms are shown at right, directly above the patient.
Perioperative Anesthesia Plan• The perioperative anesthetic plan should keep in view -The primary cardiac disease of the patient. Restrictions set by the use of the robot,implication of one lung physiology in the setting of cardiac disease, prolonged percutaneous cardiopulmonary bypass (CPB) with its problems, Management of any complications.
Perioperative Anesthesia Plan Cont. Patient selection- Adequate patient size Ability of the patient to tolerate one lung ventilation.• Elective CPB using femoral cannulation may be needed in these cases prolonging CPB times if OLV is not tolerated.• Conditions such as chronic renal, hepatic failure, coagulopathy(regional anaesthesia) or a previous neurological event such as stroke which may not allow prolonged CPB should be screened.• The condition of the thoracic spine, and the skin overlying the T1-T5 area should be examined .
Preparation and Monitoring• Cardiac medication, including beta blockers, calcium channel blockers, and nitrates should be continued on the day of surgery.• Angiotensin converting enzyme inhibitors should be omitted.• Antiplatelet drugs such as clopidogrel need to be stopped five to seven days earlier.• Smoking should be stopped and preoperative bronchodilators started.• Serum electrolytes especially K + and Mg ++ should be normalized Premedication may include an oral benzodiazepine such as Midazolam 0.1 mg/Kg
Monitoring• ECG,• end tidal CO 2 concentration,• Pulse oximeter,• CVP,• Right and left radial intraarterial pressure,• bispectral index (BIS),• nasopharyngeal temperature• urine output.• Specialized cardiac monitoring may include a pulmonary artery catheter (PAC) and TEE.
Monitoring Cont.• Right radial or bilateral radial arterial pressure is used for monitoring.• This is done to detect migration of the endovascular balloon cannula causing obstruction of the innominate artery, if the heart port cannula is used for endovascular CPB.
Important issues specific to management of robotic cardiac surgeryPatient positioning,long duration of the procedure,Patient hypothermia,Respiratory and hemodynamic effects of OLVand concealed blood loss
Patient position:• Proper position allows robotic arm movement without obstruction and allows easy initiation of percutaneous CPB if needed for the procedure.• Access to the patient chest and airway is nearly impossible after docking of the robot inside the patient chest through the working ports.• Precautions must be taken to confirm the position of the double lumen endotracheal tube (DLT) before final patient position using a fiberoptic bronchoscope.• For most robotic cardiac surgeries, the patient is positioned supine. The arm on the side of the chest port placement is allowed to hang over the edge of the table in a sling to allow space for port placement.• Pads may be placed below the chest to elevate this hemithorax by 25 30 to allow port placement in a triangular arrangement.• change in the electrical axis of the heart after creation of a capnothorax may make ST segment analysis on ECG unreliable.
Induction and Maintenance Of General Anesthesia• Anesthetic techniques are primarily narcotic- based, induction being with a hemodynamically stable agent such as Etomidate with Rocuronium for muscle relaxation.• Longer acting muscle relaxants may subsequently be added to ensure patient immobility after port placement.• Intubation is done with an appropriate sized DLT. Either a left or a right sided DLT may be used but it may be advisable to intubate the bronchus on the side to be ventilated.
Regional Anaesthesia+GA• Use of regional anesthesia as general anesthesia adjuvant allows lighter levels of GA during surgery, with minimal intraoperative hemodynamic changes and a smooth transition to postoperative analgesia.• RAVECAB procedures, technique of choice may be combination of thoracic PVB and light GA.• Pre-induction placement reduces intraoperative anesthetic requirements and can provide cardiac sympathectomy.• When PVB has been established, the GA is induced with a small dose of narcotic (fentanyl 3-5 mg/kg) and of propofol (0.5-1 mg/kg) and rocuronium (1 mg/kg).• Because the RAVECAB procedure currently requires four to six hours, an infusion of rocuronium and low dose propofol (50 mg/kg/min) is maintained throughout surgery.
Creation of Capnothorax CO 2 is insufflated into the hemithorax through the side being operated upon, to prevent smoke formation and hazard of gas explosion in the hemithorax.• Increased CO 2 pressure, above 5-10 mmHg, may reduce venous return to the heart or result in increased arterial CO2 tension.• 18G venous cannula in the pleural space can be used to measure pleural pressure and also act as a vent for excess CO 2 , avoiding tension capnothorax.• Gastric decompression with a nasogastric tube may prevent rise of airway or intrapleural pressures from gastric distention.• The capnothorax may interfere with TEE monitoring.
Physiological Perturbation Respiratory System-: Need for OLV and creation of a capnothorax with CO2 insufflation on the side of robotic port placement causes Respiratory embarrassment. Ventilation-Perfusion (V/Q) mismatch Increase in shunt flow large [P (A-a) O 2 ] gradient and low (PaO 2 ).
Management• Continuous positive airway pressure (CPAP) of 5 cm is applied on the collapsed lung to improve oxygenation and reduce shunt fraction.• Continual vigilance and monitoring of insufflation pressure, airway pressure, expired tidal volume, and central venous pressure is essential.• Hypoxia and hypercarbia should be avoided as it can elevate pulmonary artery pressure and pulmonary vascular resistance as well as reduce cardiac output.
Physiological Perturbation Cont. Cardiovascular system-:• CO2 insufflation into the non-ventilated hemithorax with the deflated lung causes rise in intrathoracic pressure and decreases venous return.• causes reduced cardiac output, increased CVP, mPAP, and PCWP.• SvO 2 decreases in OLV, recover on resumption of TLV• Rise in PaCO2 during OLV and Capnothorax can cause coronary vasoconstriction.
Management• Maintaining insufflation with CO 2 at two to three liters per minute, avoiding intrapleural pressures above 10 mmHg, reduces chances of cardiorespiratory compromise.• Infusion of nitroglycerin is used to control ST segment changes or elevations of pulmonary capillary wedge pressure.• Maintain a heart rate between 50-80 bpm.• External defibrillator pads are applied before induction of anesthesia
Hypothermia• Occurs Because of exposure, prolonged surgery, use of cold intravenous fluids, respiratory gases and CO 2 insufflation.• Delaying extubation or causing shivering in the postoperative period that may increase oxygen requirements significantly.• Ambient air warmers may be used to maintain normothermia [Sessler 1992]
Fluid management• Titrate fluid therapy to maintain pulmonary capillary wedge pressure (PCWP) at patients’ preoperative values, 12-15 mmHg.• In the event that conversion to CPB is required after several hours, the addition of pump prime solution may result in significant crystalloid fluid overload.• The perfusionist must be aware of this potential for fluid overload, with the possible requirement for ultrafiltration during rescue CPB in such stand- by cases.
Cardiopulmonary Bypass Management Placement of Cannulae- Arterial access: Femoral arterial cannulation is the standard .• TEE assessment of the descending aorta is essential to rule out severe atherosclerosis. Arterial cannulae of sizes 15 Fr to 19 Fr can be introduced transfemorally using Seldinger technique with a side port for distal limb perfusion for conventional femorofemoral CBP.• 10.5 Fr intra-arotic balloon clamp introduced transfemorally into the ascending aorta.• on inflation, it internally cross clamps the aorta and has a distal port for aortic root venting, antegrade delivery of cardioplegia and for active suctioning and deairing at the termination of CPB.
Cardiopulmonary Bypass Management cont. Venous access:• Transfemoral cannulae may not empty the ventricles completely requiring additional cannulation of superior vena cava via internal jugular vein.• TEE is helpful to guide cannulations, guide wire placement and final positioning of the SVC and inferior vena cava (IVC) cannulae.• For percutaneous CPB, the anesthesiologist places a PAC for venting the pulmonary artery and a Coronary Sinus catheter for retrograde cardioplegia through the right IJV, with positioning of both catheters confirmed by TEE.• On inflating the CS catheter balloon a previously right atrial trace changes to a right ventricular trace.• A 100 units/kg dose of heparin is recommended before CS manipulation to avoid CS thrombosis.• The PA vent catheter allows passive venting of the pulmonary artery at approximately 50ml/min.
Commencement of CPB and aortic cross clamp• Bypass is initiated with monitoring of right radial arterial pressure, aortic root pressure and with vacuum assisted or kinetic assisted venous drainage.• If the percutaneous Endoclamp system is used, The endoaortic balloon is inflated to 250 - 300 mmHg pressure after TEE guided position check, to produce an internal crossclamp.• Decompression of the heart may be aided by the PA catheter vent.
Commencement of CPB and aortic cross clamp cont.• Cardioplegia can be administered antegrade, through a distal port in the endovascular aortic cannula and the aortic root can subsequently be vented, through this port. Cardioplegia can be given retrogradely through a CS catheter if required.• Apart from the Endoclamp system, another system in use is the Estech which is similar, except for a port distal to the balloon to allow antegrade aortic flow.• Transthoracic aortic clamping can be performed by use of- A Softclamp which can be placed transthoracically on the aorta. or long bladed aortic cross clamp.
Aortic cross clamp cont.• Pump flows may need to be reduced during cross clamping for all the above clamps both transthoracic and endovascular, for proper placement and prevention of damage to the aorta.• Dislodgement of the balloon of an endovascular catheter can lead to obstruction of the innominate artery, with cerebral hypoperfusion and neurological injury.• For detecting balloon migration TEE and the radial artery pressure trace are used.• Occasionally the balloon may migrate proximally obstructing the coronary arteries, causing myocardial dysfunction.• Use of the endoaortic balloon catheter should be avoided in heavily atherosclerotic aorta for fear of dislodgement and embolization of plaque.
De-airing and weaning• De-airing of the heart is difficult after CPB, in robotic cardiac surgery.• There is lack of direct access to the heart for the surgeon and with the use of the slight lateral tilted position, the intracardiac air tends to be retained along dorsal interventricular septum and right pulmonary veins.• Use of CO 2 insufflation into the hemithorax tends to displace any air from the exposed areas of the heart and this is supplemented by hand ventilation to expel air from the pulmonary veins.• Weaning off CPB is done under TEE guidance following standard practices as for the type of surgery with conventional CPB.
De-airing and weaning Cont.• At the end of the procedure, after reversal of heparin with protamine, the DLT is changed for a single lumen endotracheal tube using a tube changer, if difficulty is anticipated due to airway edema.• If surgical trauma to the lung has resulted in intrabronchial bleeding, use of the DLT for lung separation may be continued into the intensive care unit, till bleeding is controlled.• Air and CO 2 act as electrical insulators, increasing transthoracic electrical impedance and defibrillation thresholds.• Reversal of the capnothorax and institution of two lung ventilation may help in successful defibrillation using the external defibrillation patch electrodes.
Problems specific to Robotic Cardiac Surgeries
Procedure likely to be performed using robotic assistance(Future trends)
Future Trends in Robotic Cardiac Surgery cont. Off Pump Cardiac Repair: (OPCARE)• Beating heart off pump intracardiac repair was studied in bovine experiments using a robotic system with two ultrasound based intracardiac visualization systems allowing for two different but simultaneous planes of the heart, and identification of both, intracardiac structures and the robotic instruments, within the heart chambers.• Intracardiac ultrasound probe introduced through the bovine femoral vein.
Prototype epicardial crawling device• Endoscopic robotic device for intrapericardial intervention on the beating heart .• The device adheres to the porcine epicardium and crawl like an inch worm at 8 cm / min under surgeon control to reach any site on the surface of the beating heart.• The first application being planned is for epicardial lead placement for cardiac resynchronization therapy and delivery of stem cell or myoblasts to areas of failing myocardium for regenerative therapy.
Robotic fetal techniques:• Fetal cardiac disease can now be diagnosed as early as 16 weeks of gestation.• Using robotic telemanipulation, direct visualization of the choroidal vessels is possible, allowing access to fetal cardiac chambers with catheters and the opportunity for intracardiac manipulation.• With real time 3 dimensional imaging, prenatal cardiac intervention for human fetal aortic valve stenosis can reduce left ventricular hypoplasia, restoring ventricular growth and function .
Conclusion• Robotically assisted CABG is reproducible and seems to meet general safety standards in coronary surgery. (beating and arrested heart robotic operations)• Minithoracotomy & totally endoscopic port-only approaches reduce surgical trauma while providing cosmetic benefits and preservation of structural thoracic integrity.• Given the ongoing development in hardware, software, and surgical techniques, robotically assisted CABG is here to stay, and broader application is most likely.• For the future, robotics is guaranteed to offer exciting prospects for the surgical treatment of coronary artery disease.