Define functional residual capacity and closing volume, what is there importance in anaesthesia practice?enumerate factors affecting FRC and CV

Functional Residual Capacity is the lung volume at the end of a normal exhalation. This is the volume which  balances the outward pull of the structures of the thoracic cage and the inward elastic recoil of the lung parenchyma 

Importance in anaesthesia practice

Factors affecting the FRC and closing capacity

Closing capacity is the volume at which the small airways which lack the cartilaginous structures and depend on traction caused by the elastic recoil of the adjacent tissue for patency start to close especially in the dependent part of the lungs.

Induction with general anaesthesia reduces the FRC and closing capacity, this decrease is due to cephalic movement of the diaphragm.Other factors affecting the lung volume and compliance is the position of the patient, steep head down .The closing capping reduction can increase the intrapulmonary shunting which is more in elderly, obese and patients with lung diseases.

1) Body Habitus : FRC is directly proportional to height

2) Sex: FRC is less in females as compared to males

3) Postures:FRC is reduced in supine position 

4) Lung Disease: Restrictive lung diseases reduces the FRC and compliance of the lung

5) Diaphragmatic tone: affects the FRC

 What are the indications of transversus abdominis plane block? With the help of a diagram describe the block?

 The transversus abdominis plane block is the technique of deposition of LA agent in the fascial plane between transversus abdominis muscle and internal oblique which is done either with ultrasound guided technology or anatomical landmark guided .

Indication

unilateral block: 

• Cholecystectomy
• Appendicectomy
• Nephrectomy
• Renal transplant

bilateral block

• Ventral hernia repair
• Lower section caesarian section
• Hysterectomy
• Inguinal hernia repair
• Bariatric surgery
• Colostomy closure

Technique of the block

Equipment:

1) Ultrasound machine with linear transducer ,

curvilinear may be needful in obese pt

2) Sterile cover and gel

3) Skin disinfectant like chlorhexidine 2%

4) Block needle with tubing (50 to 100mm and    

    20 to 21 G)

5) LA agent bupivacaine,ropovacaine

6) 2 20ml syringes containing the LA

Preparation

Informed consent is obtained

Iv cannula is placed

Position

The patient generally lies supine

Monitoring

the basic monitoring of HR,SPO2,BP

High frequency linear probe with gel in sterile transparent cover is placed on the anatomical site corresponding to subcostal ,lateral or posterior TAP block

The probe is moved up and down or rotated to bring the right image

The first layer is Skin and subcutaneous tissue 

The next three are muscle layers External Oblique, internal oblique and traversus abdomens,int oblique being the thickest

As the needle tip enters the block compartment,hydrodissction done

with normal saline and when the plane within the internal oblique and transversus abdominis is separated the LA agent of around 15 to 20ml is injected slowly after negative aspiration for blood

Complications

bowel injury, hematoma, intravascular injection of LA, intraperitonal injection.

                                               

Preoperative evaluation and anaesthetic management of a 35 year-old female patient with a prosthetic mitral valve scheduled
for MTP with laparoscopic tubal ligation

Preoperative Assessment and optimisation

In patients with mechanical heart valve the anesthetic management addresses the following areas of concern

assessment of cardiac function 

• residual pathology

• infective endocarditis

• anticoagulation status

• preparation for reversal of anticoagulation if needful

• neurological evaluation for detection of microthrombi

The cardiac function is assessed with history of dyspnea,orthopnea and easy fatiguability, rhythm abnormality, chest rales, and distended jugular vein.
the labs needed would be ECG,CHEST RADIOGRAPH AND 2D ECHO
CARDIAC CATHETERISATION may provide additional information
the prosthetic valve can br mechanical or bioprosthetic
The prosthetic valve can be heterograft composed of porcine or bovine tissues mounted on metal supports or homografts which are preserved human aortic valves
they last less than the mechanical valve for 10 to 15 years and have less thrombogenic potential so long term anticoagulation is not necessary

Assessment of prosthetic heart valve with 2D ECHO for ring stability and leaflet motion while TEE provides higher resolution images.MRI for prosthetic valve regurgitation or paravalvular leak. CAG can be done for transvalvular pressure gradients and prosthetic valve area.

COMPLICATIONS WITH PROSTHETIC VALVE

• VALVE THROMBOSIS
• SYSTEMIC EMBOLISATION
• STRUCTURAL FAILURE
• HEMOLYSIS
• PARAVALVULAR LEAK
• ENDOCARDITIS

MANAGEMENT OF ANTICOAGULATION

           ANTICOAGULATION BEFORE SURGERY
                                      
                                   ⬇
INCREASED RISK OF VENOUS AND ARTERIAL THROMBOEMBOLISM

                                                             

⬇                                                               ⬇
              MINOR SURGERY.                                                                        MAJORSURGERY
                  ⬇
        CONTINUE ANTICOAGULATION IF    MINIMAL BLOOD LOSS                                                                                                                                                                                                           

                                                                                                                                                                                                            

                                                        

                                            ⬇

                                                                                  

                                           WARFARIN or clopidogrel or any of the newer anticoagulants are discontinued 1 to 5 DAYS prior to surgery

                                                                                   

                                                          ⬇

                                                                                  
                                        

              

      REPLACED WITH IV  UNFRACTIONATED  

                             HEPARIN OR LMWH

                                                                                         

                                                                 ⬇         
                                           TILL 1 DAY BEFORE   

                                             SURGERY 
                                                                                            
 RESTARTED  1 DAY POST SURGERY IF RISK OF BLEEDING IS REDUCED

ELECTIVE SURGERY IS AVOIDED IN THE FIRST MONTH AFTER AN ACUTE EPISODE OF THROMBOEMBOLISM

ANTICOAGULATION IS IMPORTANT IN PARTURIENTS IN VIEW OF HYPERCOAGULABLE STATE BUT WARFARIN IS AVOIDED AND LMWH IS CONTINUED TILL DELIVERY 

DOSE ASPIRIN THERAPY CAN BE GIVEN IN CONJUCTION WITH HEPARIN THERAPY