Ординатура / Офтальмология / Английские материалы / Small Incision Cataract Surgery (Manual Phaco)_Singh_2002

If the pressure is too much then the lateral canthotomy can be done to decompress the globe. Retrobulbar haemorrhage, in rare instances, can lead to optic atrophy. The exact mechanism, whether it is as a result of direct injury or because of the compression of the optic nerve is not clear. Central retinal artery block has also been reported due to retrobulbar haemorrhage.

Optic nerve sheath injury There are chances of hitting the optic nerve sheath, which can lead to optic atrophy. This can be prevented by asking the patient to look straight rather than look up and in while injecting.

Globe perforation This can also occur while injecting. To prevent this disaster the needle should first be directed straight backward till you reach the equator of the eyeball. After that it should be directed towards the occiput. If globe perforation is suspected, wait for a while and ask the patient to move his eyes gently. If the needle is in the globe or in the sclera the needle will also move. The diagnosis is made by seeing the hypotony, absence of red glow and pain. In this case the needle should be withdrawn and the examination by indirect ophthalmoscope should be done. The extent of the injury is related to the depth of perforation. If the needle perforates only the sclera, then it heals by a simple scar. In case it pierces the choroid, then there are chances of choroidal haemorrhage, and if it enters the retina, then retinal holes and detachment can occur. If the fluid is injected inside the vitreous then there are chances of severe reaction from the contents of the anaesthetic used and from its preservative too. Intraocular pressure may also rise. If intravitreal haemorrhage is present, the patient should be referred to a vitreoretinal surgeon.

Contraindications include bleeding disorders, extreme myopia and posterior staphyloma.

Peribulbar Anaesthesia

This is most commonly applied technique nowadays. In retrobulbar technique we have to go in the muscle cone. It may lead to retrobulbar haemorrhage, injury to optic nerve and other complications enumerated above. All these complications can be avoided in peribulbar technique. Here the aim is to go around the eyeball. A 5cc syringe with 24 G needle is taken. In this we take 5 to 6 ml cocktail of xylocaine and sensocaine in equal quantity and hyaluronidase in a concentration of 1.5 units per ml. Xylocaine with adrenaline is better if it is not contraindicated otherwise. Lower orbital margin is palpated and at the junction of medial two-third and lateral one-third 3 ml of already prepared cocktail is

injected around the eyeball. The remaining cocktail is injected at a site at the junction of medial one-third and outer two-third of upper orbital margin. One should take care to avoid the walls of eyeball and also the conjunctiva. Ocular massage is given for ten minutes if plain ECCE is planned but massage should be avoided if manual phaco is planned.

Other sites for giving the peribulbar block are:

•Superior

•Medial

The superior site In this technique the needle goes through upper fornix. The patient is asked to look down and in. The needle passes at a tangent. Since the direction is upward there are no chances of globe rupture. It also blocks orbicularis and superior rectus is also knocked off. This prevents Bell’s phenomenon.

The medial site Here the needle passes through the caruncle and medial canthal tendon. There is a big space between medial orbital wall and wall of the eye. The only vessel that can come in the close proximity is anterior ethmoidal artery and vein which lies much above the track of the needle. It also gives a good effect and can be used as an adjunct.

Complications

Conjunctival chaemosis This is seen quite commonly. While injecting, the needle passes into the conjunctiva. The chaemosis goes off after the massage.

Globe perforation The signs and symptoms are described above. Here the emphasis is laid on the point that the globe perforation can occur in peribulbar block also. Initially there was an impression in the minds of the surgeons that it does not cause globe perforation. But the reported incidence of perforation are equal in both peribulbar and retrobulbar anaesthesia.

Oculomotor problems The oculomotor problems associated with local block are transient diplopia extending for one or two hours. But some cases of prolonged diplopia are reported. At times ptosis can also occur. These complications usually resolve in due course.

The subconjunctival route It has also been tried, but has not been widely accepted by ophthalmologists. The injection is given at superior limbus after putting topical xylocaine 4 per cent drops. Ocular massage is given. Facial block is also required. This injection may also cause accidental globe perforation. In addition, there are chances of weakening of superior rectus. Moreover, akinesia is not complete. Therefore this anaesthesia has not been used commonly for ECCE, but it may prove to be good for phacoemulsification.

Sub-Tenon’s block This block is favourable to both phaco and non-phaco surgeons and can be also used in case the patient is not ready for injection into the skin. The site chosen is inferonasal or inferotemporal. But inferotemporal is best avoided since inferior oblique lies there. After instilling topical xylocaine 4 per cent drops, a snip is given in the conjunctiva and also in the Tenon’s. For assuring that the space is sub-Tenon’s an iris repositor can be passed in the sub-Tenon’s space. Then a blunt tipped cannula is taken and 2 cc of cocktail is injected after reaching posterior to the equator. The advantage of injecting posterior to the equator is that Tenon’s capsule is deficient posteriorly and the fluid goes directly into the muscle cone. Therefore excellent akinesia is obtained. Since sensory nerves cross the Tenon’s capsule immediate anaesthesia is obtained. If cannula remains anterior to the equator there are chances of proptosis. The only disadvantage seems to be a snip into the conjunctiva and also chances of subconjunctival haemorrhage. Therefore, some surgeons prefer giving this block in the upper quadrant. In case there is haemorrhage, it is covered by the lids (Fig. 10.2).

Fig. 10.2: Parabulbar or sub-Tenon’s anaesthesia Courtesy: Alcon (India)

Topical Anaesthesia

Phacoemulsification is now commonly performed under topical lignocaine. Paracaine is better as it does not cause any stingy sensation. These drops instilled 5 minutes before the surgery are very useful in anaesthetizing the cornea. But the sensation in the iris remains. For that intracameral lignocaine 0.5 ml can be used. It anaesthetises the iris. Thus there is no pain even if the iris is touched by mistake. The advantage of this technique is that there is no need of patching the eyeball and all the complications of retroand peribulbar are avoided. The disadvantage is that only phaco can be done with this technique. ECCE or nonphaco small incision should not be done under topical.

Facial Nerve Blocks

Facial nerve supplies the orbicularis oculi muscle. The action of this muscle is squeezing the lids. Its block is essential to avoid this action. Facial nerve block is maximally needed as an adjunct when retrobulbar block has been used. But at times it may be of great help in case peribulbar block does not achieve the full block of orbicularis. Phaco and non-phaco surgeries can be done without blocking the action of orbicularis because these are closed chambered technique, but not the ECCE wherein the chamber is open. It may lead to the contents coming out of the eyeball. Several blocks have been described but the most commonly used are being described here.

Nadbath and Rehman Block

This block uses the anatomical fact that the facial nerve passes below the mastoid process. The injection is given in the triangular space below the mastoid. I have seen Dr Momose using this technique in eighties. Usually this technique is not used because it blocks all the branches of facial nerve thus affecting half of the face. The vagus nerve and the glassopharyngeal nerves lie close in this area. Their block may lead to speech defect, drinking and swallowing problems. Permanent facial paralysis has also been reported.

O’brien Block

Facial nerve crosses the neck of the mandible before entering the parotid gland. This injection is given after palpating the temporomandibular joint by asking the patient to open his mouth. About half an inch below this lies the facial nerve close to the anterior border of mandible. Four to five ml of lignocaine is injected into this area. The massage is must after that because nerve lies deep. It can affect both the upper and lower branches.

Van Lint Block

With this block all the branches going to the orbicularis can be blocked. Facial nerve gives branches to orbicularis about 1 cm away from the lateral orbital margin in its lateral angle. 3 to 4 ml is injected deep in this site above the superior orbital margin, below the inferior orbital margin and back starting from the site described above. The only problem with this technique is its close proximity to the operation site as it is likely to cause haematoma formation.

There are some neuro-ophthalmic reflexes that one needs to remember. These are as follows:

Oculocardiac reflex This gets precipitated when there is pressure, torsion or pulling on the extraocular muscles. Its signs and symptoms are sinus bradycardia, ectopic beats or may be sinus arrest. Prophylaxis and treatment include IM or IV atropine injection. Its pathway is through long and short ciliary nerve to ciliary ganglion. Efferent pathway is through vagus nerve.

Oculorespiratory reflex Its signs and symptoms include shallow breathing, brachypnoea or even respiratory arrest. Its prevention and treatment include controlled ventilation especially in children undergoing squint surgery. Its afferent are same as that of oculo-cardiac

reflex. Efferent are via a connection between trigeminal sensory nucleus and pneumotaxic centre in pons and medullary respiratory centre.

Oculo-metric reflex It is not well understood. It induces vomiting and occurs as a result of pull on extraocular muscles.

FURTHER READING

1.Jaffe Norman S: Atlas of ophthalmic surgery; JB Lippincott: 1990.

2.Amar Agarwal: Phacoemulsification, laser cataract surgery and foldable IOLs; Jaypee Borthers, India: 2001.

Uncooperative, mentally confused, psychotic, paled, severely deaf patients and those having involuntary movements may necessitate general anaesthesia.

4.If sensitivity to local analgesics is rare the overdose toxicity either by real overdose of the drug or due to inadvertent intravascular injection is not an uncommon happening leading to incoherent confused behaviour, perspiration, bradycardia, etc. If left ignored it may leave behind morbidity or even mortality.

5.It is one of the most frequent demands from the patient to remain unconscious during operation due to fear and anxiety. Majority of the patients after explaining the procedure get ready to be operated under local analgesia but still a small fraction of patients demand general anaesthesia. In the event of an unsuccessful or partially successful block again either deep sedation or general anaesthesia will be required.

6.In case of any unforeseen life-threatening event like the well-known ‘oculo-cardiac reflex’ if anaesthesiologist is already present in operation theatre majority of such problems can be checked to happen or treated effectively quicker and faster as in case of resuscitation the importance of time factor is wellrecognized.

7.To be guarded against medicolegal aspect the role of an anaesthesiologist is very vital in operation theatre irrespective of any speciality.

It is not only a dictum but also a practical reality that no anaesthetic whether local or general should be administered unless there is provision for artificial ventilation. Some minimum equipments, drugs and monitoring systems should be there for the purpose of resuscitation in case of any eventuality.

Minimum Equipment

i.Equipment to artificially ventilate the patient, preferably an anaesthesia machine or an AMBU bag with the provision of oxygen supplementation.

ii.Oxygen cylinder with a flow meter with provision of connecting an oxygen delivery tube with nasal prongs, nasal catheter, poly or ventimask. Those patients who had history of asthma, myocardial ischaemia or feeling of suffocation under facial drapes should be given 2-4 litres oxygen flow per minute via a tube with binasal prongs as unlike a

mask it does not cause any tenting of drapes and thus causing inconvenience to surgeon.

iii.Guedel’s oropharyngeal airways to prevent fall back of tongue in a sedated patient.

iv.A suction apparatus

v.Magill’s throat cleaning forceps

vi.Laryngoscope

vii.Endotracheal tubes of different sizes with connectors to ventilation equipment.

Minimum Drugs (Mostly in Injectable Form)

i.Atropine

ii.Adrenaline

iii.Dopamine

iv.Dobutamine

v.Preservative free 2 per cent lignocaine (Xylocard)

vi.Ephedrine or mephenternamine

vii.Hydrocortisone

viii.Frusemide

ix.Antihistaminic (Avil)

x.Analgesics like–morphine, fentanyl, pentrazocine or tramadol

xi.NSAID analgesics, e.g. diclofenac sodium

xii.Midazolam or diazepam

xiii.Thiopentone sod. or propofol

xiv.Ketamine (intraocular surgery contraindicated)

xv.Succinylcholine

xvi.Sodium bicarbonate (8.4 vol.%)

xvii.Sorbitrate tablets

xviii.Nitroglycerine–injections, tabs, ointments and patches

xix.Nitrous oxide gas

xx.Intravenous cannulas

xxi.Adequate number of disposable syringes.

Minimum Monitoring

The following monitoring systems should be available:

i.Stethoscope

ii.Sphygmomanometer to measure blood pressure at regular intervals preferably self-reading electronic instrument to avoid repeated use of stethoscope.

iii.Pulse-oximeter It is one of the most valuable noninvasive monitoring systems measuring peripheral

arterial oxygen saturation (SpO2) usually with an audible beep to monitor heart rate also, which the operator himself can see and hear while operating. With its ease to use it should be used in every patient. It has a light-emitting probe which can be inserted

in finger, ear lobule or palm or foot (in case of a child) and the electronic signals are taken to the microprocessor, which performs the necessary calculations giving the SpO2 per cent reading on monitor.

iv.Cardiac monitor It is again a non-invasive monitoring of electrical activity of heart using various chest leads, especially in lead II. Arrhythmias occurring during operation can be detected early and treated accordingly.

v.Defibrillator It is the equipment, which can be used in case of cardiac arrest to return normal rhythm of heart by giving electrical shocks of different intensities.

All the above monitoring systems are available in different models either as a single system monitor or two in one to five in one models.

vi.Dextrostix These are the enzyme-impregnated sticks for quick measurement of blood glucose from capillary blood by dipstick method.

Postoperative 12

Infections:

Prevention and

Management

Jagat Ram

Gagandeep Singh Brar

Postoperative endophthalmitis is one of the most devastating complications of intraocular surgery, leading to a marked loss of vision in over 80 per cent of cases.1 Better instrumentation, microsurgical

techniques, prophylactic antibiotics and better understanding of asepsis has significantly reduced the incidence of this complication. Maintenance of asepsis is imperative for ensuring safe surgery for the patient and minimizing postoperative infection and its disastrous consequences. The reported incidence of postoperative endophthalmitis varies and appears to be influenced by preoperative prophylaxis with antibiotics, the aseptic technique used and the geographical location.

The average incidence of endophthalmitis has reduced from approximately 10 cases per thousand prior to 1950 to the present figures of approximately one case per thousand.2-4 Postoperative endophthalmitis may occur clinically as an isolated event or as cluster infections in the form of a surgical epidemic.5-7 Although in most cases, the source of the infecting organism cannot be identified with certainty, the most common infecting organism is

Staphylococcus epidermidis.7-9

Postoperative endophthalmitis will be discussed under two major headings:

i.Prevention of postoperative inflammation and endophthalmitis.

ii.Management of postoperative endophthalmitis.

PREVENTION OF POSTOPERATIVE ENDOPHTHALMITIS

Operating Room Layout

Contemporary theatre design incorporates zoning of areas within the operation theatre complex.9 The

important aspects of OR layout include location, design, proper ventilation and separation of the sterile zone from the non-sterile areas.

For strict asepsis, an eye OT should preferably be nonsharing with any other surgical discipline. The location should preferably be on an upper floor in the building. Contamination from a hospital construction environment has been documented to cause an epidemic of Aspergillus endophthalmitis.8

The major zones of an OT complex are:

a.Outer zone reception area providing access for all persons and supplies.

b.Changing room This area is located near the entrance of the OR complex.

c.Transfer zone This area includes a corridor for transferring the patient.

d.Aseptic zone Scrub and gowning area, the preparation room and the operating room (OR).

e.Operating room The OR should have one opening towards the scrub area and another towards a sterile zone marked for instrument packing and sterilization. The head ends of the operating tables should be directed away from the entrance. Floors and walls should preferably be of non-porous material with minimum joints to enable proper cleaning and carbolization.

f.Disposal zone processing of used equipment supplies and disposal of waste.

Ventilation

Air decontamination is important. High Efficiency Particulate Air (HEPA) systems remove most microorganisms ranging in size from 0.5-5.0 μ.10 The principle

of ventilation in the OR is delivery of positive pressure filtered air in a unidirectional vertical flow over the operating table. The current United States Public Health Service minimum requirement for optimum OR air is: temperature between 18 and 24°C, humidity 55-80 per cent, and 25 changes per hour.10 Fridkins et al11 reported 4 cases, who contracted Acremonium kiliense endophthalmitis due to defective ventilation in the OR. In the surgical operation theatre, bacterial count of air should not exceed 1/ft3 (35.3/m3).12 and air entering the theatre from filters should not contain more bacteriacarrying particles than 0.5/m3, within 30cm of the operation site not more than 10/m3, and elsewhere in the theatre should not exceed 20/m3.

Cleaning, Disinfection and Sterilisation of OR

The terms are independent of each other and each needs to be clarified and understood separately. Cleaning essentially means the removal of foreign matter (e.g. soil, organic matter) from the concerned surface. Unless an article is mechanically cleaned, there will not be sufficient surface contact between it and the decontaminating agent, and sterilisation will not be accomplished. Cleaning is normally accomplished with water, mechanical action and detergents. Disinfection is a process of freeing the concerned object of all pathogenic microorganisms, which may cause infection during its use. Sterilisation is a process that frees the treated object of all living organisms.13 It is impractical to attempt to sterilise the entire OR and equipment, and the current practice concentrates on disinfection. Instruments and drapes need to be sterilised adequately. Sterilisation is an absolute term, and there is no term as partial sterility.

The hundreds of compounds derived from phenol constitute phenolic compounds. They are good bactericides and are active against fungi.13 They are sometimes virucidal but are not sporicidal, except at temperatures over 100°C.

This class of compounds is used for decontamination of the OR and for noncritical medical and surgical items. The floor and 5-6 feet of OR walls should be mopped with phenolic solution. Similarly, wet mopping all OR tables, mats, instrument trolleys, stools chairs and supply shelves with phenol followed by a wipe down with 70 per cent alcohol is an effective decontaminating regimen.13Anaesthetic equipment like endotracheal tubes, airways and suction apparatus should be disinfected after every use.

Formaldehyde is the most common agent used for sterilisation of operating room. The gas is liberated by

spraying or heating formalin or solid paraformal- dehyde.9,14-16 The efficacy of the process is however uncertain especially at temperature below 20°C and relative humidity below 70 per cent.16 Before fumigation, adhesive tape is applied around the edges of the door, windows and over ventilators apertures, etc. to seal the desired area and prevent leakage to adjacent room or outdoors. For each 1000 cubic feet of space (28.3 m3), 500 ml of formaldehyde 40 per cent in one litre of water is placed in an electric boiler or in a large bowl placed on a electric hot plate with safety cut-out when boiling dry. Switch on the boiler and leave the room and seal the door. After fumigation the room is to be kept closed for 8-10 hours. Subsequently, ammonium solution is introduced and left in the room for a couple of hours to neutralise the formaldehyde (1 litre ammonium solution plus 1 litre of water for every litre of 40 per cent formaldehyde used.)

OR Discipline

Personnel entering the OT complex should be kept to a minimum. Anyone with overt infection should be barred from entering the OT complex. All persons entering the OT should change into freshly laundered clothing. Hair and beards should be clean and be well-covered by caps and masks. High filtration disposable masks are to be worn at all times when within the aseptic zone. Ladies should take special care at trimming nails and removing jewelry when working within the theatre complex. All persons must wash their hands thoroughly before entering the OR. It is desirable to restrict all persons other than the staff from the OR. In today’s age of modern electronics, it is better for students and other trainees to be seated at a remote place and observe surgery on a closed circuit television rather than crowd around the surgeon’s table.9

Sterilisation of Instruments

Instruments need to be thoroughly cleaned after every surgery before being subjected to sterilisation. Microsurgical instruments are best cleaned by an ultrasonic cleaner. These contain liquids through which sound waves pass at a frequency of 1,00,000 Hz or more.10,15 The ultrasonic waves generate submicroscopic bubbles, which collapse and create a negative pressure on particles in the suspension. The bacteria disintegrate and the protein matter is coagulated by this action.15

Sterilisation can be done by physical or chemical methods, of which the former is more reliable.

Plasma Sterilisation

This new modality of sterilisation of instruments has been introduced recently for heat sensitive medical devices. A very small quantity of hydrogen peroxide in various phases, including low-temperature gas plasma excited by radio waves, is lethal to organisms on the surface of medical devices. Hydrogen peroxide is injected into the chamber under reduced pressure in a dry atmosphere. Vapour diffusion occurs throughout the contents and radio frequency energy excites H2O2 into active radicals and reactive chemical species. The free radicals so produced react with and destroy microorganisms present on pre-cleaned, dry accessible surfaces. The most well known plasma sterilisation is the SterradTM from Advanced Sterilisation Products, California using hydrogen peroxide gas plasma at low temperature (< 50°C).

Monitoring of Sterilisation Protocol

All sterilisation procedures must be monitored meticulously by appropriate means for optimum effectiveness. Various parameters and tests like ‘phenol coefficient,’ Rideal-Walker test and Chick-Martin test may be used. Monitoring sterilisation is difficult. Sterilisation process indicators (e.g. temperature charts, pressure gauges) are used to indicate inadequate process conditions. The biological indicators come closest to an ideal monitor because they integrate all of the sterilising parameters involved, such as time, temperature, pressure and packaging.

Disposal of operating room biohazardous waste Operating room biohazardous waste including infected linen, disposable syringes, IV drip set, needles, residual IV fluids, infected material, excised human diseased pathological tissue is a significant hazard to public and need safe disposal to prevent recycling of disposable and spread of infection from infected material.

Over the last decade, the disposable of operating room and hospital waste has received much attention. In most of the cases it can safely be dumped in a properly designed waste pit particularly in the developing countries.26 Incineration has been advocated as a viable method of disposal of OR and hospital waste.27

Sterile Surgical Protocol

1.Patient-related factors In isolated infections, patient related factors predominate.28 Diabetic patients and those with blepharoconjunctivitis, dry eyes or atopic disease are at a higher risk of postoperative infections

as they have a higher rate of carriage of Staphylococcus aureus.28-30 Patient related preoperative risk factors include blepharitis, conjunctivitis, dacryocystitis, lacrimal drainage abnormalities, ocular surface disorders, host immunosuppression29,30 and even upper respiratory tract infections in children.31

The ocular surface and adnexa is the main source of bacteria in culture proven cases of endophthalmitis. Using microbial DNA analysis, Speaker and coworkers showed that the main source of infection is patient’s own ocular flora.32 The importance of a scrubbing bath of the head and face on the day of surgery should be emphasised.

Preoperative use of topical antibiotic The role of prophylactic antibiotics administered both topically and subconjunctivally has been documented to reduce postoperative infection.33,34 Topical antibiotics should be started 24 hours before surgery and used 6-8 times during daytime. Instillation of topical antibiotics more than 24 hours may lead to replacement of patients owns flora by more virulent microorganism and fungi.

2.Preoperative preparation and role of povidoneiodine Speaker and Menikoff,35 in a significant breakthrough showed that a single topical application of 5 per cent povidone-iodine solution reduced the inci-

dence of postoperative endophthalmitis significantly. Povidone-iodine is bactericidal in 30 seconds.35,36 Although cilia trimming was once considered helpful in reducing postoperative infection, the present trend is not to trim cilia for intraocular surgery. This practice became unnecessary following widespread practice of isolating lashes with sterile adhesive drapes. Cleaning the lids, lid margins and adjacent skin with Povidone

iodine 5 to 10 per cent is an effective method of eliminating microbes.37

3.Scrubbing and use of gloves It is important to use nail brush and scrub properly. One should scrub hands and arms below elbow. It will take 7-8 minutes to scrub with soap. A hand dis-infection system using chlor-

hexidine reduces the rate of nosocomial infections more effectively than one using alcohol and soap.38 Povidone iodine (Betadine®) or Chlorhexidine scrub (Hibiscrub ®) is best for scrubbing. With povidone iodine or chlorhexidine solution , scrubbing twice for 1-2 minutes each is adequate. After wearing sterile

gloves, it is important to wash the hand with Ringer lactate to remove the powder from the gloves.39

4.Surgical procedure Many factors are implicated in the occurrence of endophthalmitis including the patient’s