Microsurgery Essentials: Preparation
Preconditions for Success
Stick to your normal coffee drinking habits. Coffee causes a slight tremor, but acute coffee withdrawal causes a worse one. Two factors that contribute even more to tremors are anxiety and strenuous manual exertion. Try to rest as much as you can prior to operating, and be sure to eat. Do not allow yourself to become irritated or discouraged, because this will affect your technical abilities. Strenuous activity such as heavy lifting, playing tennis, or even holding on to large retractors will make it difficult for you to use your small muscles precisely. Manual exertion should be avoided for at least 24 hours prior since it will leave a residual tremor. Don’t hold your breath while working, and don’t hold your body rigidly. Stay relaxed!
Ensure that all instruments are in excellent working condition, that their tips meet, and that they have the correct spring tension. Make sure they are not magnetized. Never allow the tips to touch another hard object, and avoid putting the tips down on a hard table. Keep them away from heavier instruments. Never grab a bunch of instruments and carry them together. Make a “basket” lined with heparinized saline gauze when you are in the OR.
- Sterile Doppler probe
- Especially helpful for identifying and ensuring the patency of perforators, as well as the pedice.
- Bipolar cautery
- A necessary tool to assist with side-branch cauterization to avoid trauma to perforators and pedicle.
- Microvascular Coupler
- An automatic device that is useful for the anastomosis of veins and thin-walled arteries.
- Heparin 100 Units/cc
- Use to rinse vessels, to prevent clots, and to keep the field clean.
- Lidocaine, usually 20%
- Papavarine, ½ or full strength
- Background material
- Necessary for providing platform for vessels while performing microsurgical anastomosis.
- Options include green or blue flexible plastic material, or even a suture pack.
- 1” cottonoids
- Absorb blood under vessels
- Wec Spheres
- “Microsponge” on a stick used for blotting
- Vessel Loop
- Retracting blood vessels and nerves
- Come in various sizes--large, medium, small, and gem clips
- Used to clip side-branches
- Irrigation cannulas
- Anterior chamber cannula (Visitec needle) used for intraluminal heparinized saline irrigation and topical papavarine irrigation
- Sterile Doppler probe
- Needle: use swedged on, cutting needles (Reverse diamond)
- Suture size:
- Greater than 2 mm: 9-0
- Less than 2 mm: 10-0
- In the OR and for practicing, you will most often use:
- Nylon black monofilament 100 micron suture with a 1/2 circle needle (Sharpoint Brand, Ref AA-105, HRM4)
Terms that you should know about:
- Focal Length: Use a lens with a focal length of 250 mm if you’re sitting down. Use a lens with a focal length of 300 mm if you’re standing up.
- Focusing: You should start your case with your microscope set to be in the center of the visual box fully zoomed in. With the scope on high power (20X), move the entire microscope head until the vessels are in full view and in focused. Then zoom out to low power (5-10X) to do the initial vessel dissection
- Visual field
- Field depth: vertical distance that is in focus
- Field width: diameter of circle that is visible
- X-Y control: Foot pedal (joystick) control allows hands-free repositioning of visual field
- Interpupillary distance: distance between eyepieces
- Light source: Usually use the brightest setting
- Halogen – 3500 degrees K
- Xenon – 5000 degrees K
- (Sunlight – 6500 degrees K)
- Glare: Caused by reflected light coming back into your eyes. Minimize glare by avoiding pools of water/saline, drying the background, using anodized black clamps.
Comfort is key. You may have learned elsewhere in surgical training that you ought to disregard your own comfort, but in microsurgery, you must get in the habit of doing the opposite. Discomfort will steadily eat away at your ability to concentrate, and it will ruin your skill. In microsurgery, comfort is defined largely in terms of the amount of muscle activity needed to maintain your body position: the less, the better.
- Make room for your legs. Your feet should be directly under the table and flat, so remove obstacles that get in the way.
- Sit so that your head and upper body remain motionless. Your forearms must lie passively on the table, completely at rest, using no upper extremity muscles to maintain your position. Do not lean on your elbows to stabilize your body, since this will make your arm muscles tense and will produce a tremor.
- Use 3 point stabilization
- Elbow stabilization: on table or folded towels
- Wrist stabilization: on table or folded towels as needed
- Finger stabilization: long, ring, and small fingers resting on table or heparinized gauze sponges. These fingers form a stage for your index finger and thumb to work.
- In microsurgery, only the fingertips move. Keep your fingers in a ”writing” position. Your elbows, wrist, and ulnar side of your hands rest on the table. The forearm should be supinated. The instruments are held between your thumb, index, and middle fingers. You will be able to open and close your instruments with fine control using your index finger and thumb, which should maintain contact with the middle finger for stability and to minimize tremor.
Setting Up the Microscope
Putting Microscope in Position:
Take an instrument in each hand, rest your elbows widely apart on the table, and bring your hands together in front of you. This point will be your best working spot for the microscope head. Adjust the tilt of the scope so that the eyepieces incline at about 50 degrees (more acute angle if you’re short; a wider angle if you’re tall).
Adjust the height of your stool so that your eyes are at the right level to see down the eyepieces. Eyes should be pointing straight ahead. Elbows should be level with hands, so set the table height to allow this. If the table will not go low enough to position your forearms horizontally (or if your wrists are hyperflexed to get into a hole), then you should stand up to do the microsurgery.
Adjusting Interpupillary Distance:
Move the eyepieces as far apart as they will go. With one eye looking down the microscope, adjust the main focus (can be done with a foot pedal), until you can see the object clearly as a small circle. Now slowly bring the two eyepieces together. A second small circle will come into view. Adjust until the two circles become one circle. Remember this setting. (Diagram adapted from Leica M720 0H5 User Manual, courtesy of John Powell.)
Each eyepiece contains its own focusing adjustment that will correct for near or farsightedness. If the strength of your eyeglasses is between plus one diopter (farsighted) and minus three diopters (nearsighted), you should take off your glasses and use the eyepiece focusing adjustment. If your correction is outside this range, you should keep your glasses on since you’ll have a hard time seeing objects in front of you when looking away from the microscope. If you keep your corrective lenses on, set the focusing adjustment on each eyepiece to “0,” and make sure the eyepieces are pushed down all the way on their seating.
- Zoom in to the highest magnification (usually with hand controls or foot pedal)
- Get your field of view into focus using the main microscope focus (usually with hand controls or foot pedal). Leave the main focus control alone, and don’t touch it again!
- Zoom out so that magnification is at its lowest setting. Your view most likely will go out of focus.
- Without touching the main focus control, move the individual eyepiece focusing adjustment until your low-magnification view comes back into perfectly clear focus.
- Zoom in again to high magnification. Your view with your second eye should be sharp at this point.
- Change the magnification to low again. It may go out of focus.
- Adjust the eyepiece focus until the second eye is perfectly sharp.
- Reset the interpupillary distance. Microscope should be fully adjusted now, and you’re ready to get to work.
Ideally, you should adjust the focus one eye at a time. Do this by setting the interpupillary distance of the eyepieces a long way out of adjustment (rather than shutting each eye tightly). It's important to get focus set up correctly so that throughout the case you will maintain parafocality, which means that your view stays in focus regardless of any change you make in the magnification.
Microscope controls will vary from model to model. The above diagram is the handle control set up for the microscope currently used in the Stanford OR (Adapted from Leica M720 0H5 User Manual, courtesy of John Powell.). Familiarize yourself with the microscope that you are using prior to operating. Know how to focus, zoom in, and manipulate the arm.