Principles and Techniques of Operative Surgery Including Neurosurgery

The Operating Environment

Modern operating theatre design plays a key role in control of airborne wound contamination. This is important mainly for staphylococci carried on airborne skin scales.

The main factors influencing airborne operating theatre infection rates are:

• the concentration of organisms in the air;

• the size of bacteria-laden particles;

• the duration of exposure of the open wound.

The first two are influenced mainly by theatre design and air supply, and the last can be minimised by avoiding unnecessarily long procedures. Operating theatre complexes are laid out so as to minimise introduction of infection from outside via air, personnel or patients. Air is drawn from the relatively clean external environment, filtered and then supplied to the theatres at a slightly higher pressure than outside to ensure a constant outward flow. Air turnover is the most important factor; the aim is to ensure 3 to 15 air changes per hour which ‘scrubs out’ the theatre air by dilution. Standard air delivery systems aim to achieve a constant flow of clean air towards the operating table, which is then exhausted from the theatre. Despite this, convection currents allow some recirculation of air, which may be contaminated, into the operation site.

The crucial importance of preventing infection in joint replacement surgery led to the development of sophisticated ultra-clean air delivery systems . These reduce postoperative infection two- to fourfold in joint replacement surgery, but the cost is very high. Enclosure of the patient in a sterile tent in which the surgeons wear space-type suits can reduce infection rates by a further 5% to 7.5%. However, correct use of prophylactic antibiotics gives better reduction in infection rates than any clean air system.

Preoperative Preparation

For many elective operations, preoperative screening for methicillin-resistant Staph. aureus (MRSA) is commonly used. This involves taking bacterial swabs from the nose, groin and other places. If positive, local antibacterial cream and other measures reduce the risk of MRSA infection for the patient and the risk of cross-infection of other patients.

Surgical Technique

Surgical technique plays an important part in minimising the risk of operative infection. Non-vital tissue and collections of fluid and blood are vulnerable to colonisation by infecting organisms, which may then enter via the bloodstream even if direct contamination has been avoided by aseptic technique. Tissue damage should be kept to a minimum by careful handling and retraction and by avoiding unnecessary diathermy coagulation. Haematoma formation is minimised by careful haemostasis and placing drains into potential sites of fluid collection; closed-drainage or suction-drainage systems reduce the risk of organisms tracking back into the wound from the ward environment.

During extensive resections of bowel, early ligation of its blood supply allows bacteria to permeate the wall ( translocation ) and this may contaminate the peritoneal cavity. Prolonged operations are a recognised risk factor for postoperative surgical infections.

Faecal contamination is associated with a high risk of infection and great care needs to be taken in operations where the bowel is opened. In emergency operations for large bowel perforation, free faecal matter is meticulously removed. A planned ‘second-look’ laparotomy after 48 hours can be considered to deal with remaining contamination and new abscesses even if the patient appears well.

General Principles

Some form of anaesthesia is needed for almost every surgical procedure, with the aim of preventing pain in all cases, minimising stress for the patient in most, and providing special conditions for some operations, for example, muscular relaxation in abdominal surgery. The choice of anaesthetic techniques includes topical (surface) anaesthesia, local anaesthetic infiltration or peripheral nerve block, spinal or epidural anaesthesia and general anaesthesia . Methods other than general anaesthesia may be supplemented with IV sedation if the patient is anxious or agitated (e.g., with benzodiazepines). IV sedation with these drugs produces relaxation, anxiolysis and amnesia, whilst retaining protective reflexes. However, these drugs can also cause unconsciousness and they must be carefully titrated to produce just the desired effects. IV sedation of this type does not provide pain relief; if needed, this is achieved with local anaesthesia or IV analgesics.

Choice of Anaesthetic Technique

Combining local or regional anaesthesia (for pain relief) with general anaesthesia can minimise postoperative respiratory and cardiovascular depression compared with general anaesthesia alone, reducing morbidity. An example is the use of caudal anaesthesia in perineal operations. Local or regional anaesthesia with bupivacaine or levobupivacaine can also be administered during an operation to provide postoperative pain relief; for example, intercostal nerve blocks during an abdominal operation allow more comfortable breathing and coughing, reducing respiratory complications. Another common example is wound infiltration with the same long-acting local anaesthetics. The main factors influencing choice of anaesthesia are summarised in Box 10.4 .

Choice of Incision

The purpose of most skin incisions is to gain access to underlying tissues or body cavities. When planning an incision, the first concern is to achieve good access and to allow it to be extended if necessary. It must also be sited in such a way that it can be effectively closed to give the best chance of primary healing and the lowest chance of an incisional hernia later. Despite patients’ impressions, the length of an incision (and the number of sutures) has little bearing on the rate of healing, and the success of an operation should not be put at risk by inadequate access.

Secondary considerations in the choice of incision are as follows:

• Orientation of skin tension lines (based on Langer lines) and skin creases —where possible, incisions should be made parallel to the lines of skin tension determined by the orientation of dermal collagen (e.g., a ‘collar’ incision for thyroid operations) as the wound is less likely to break down, there is minimal distortion, and healing occurs with little scar tissue to give the best cosmetic result

• Strength and healing potential of the tissues —the nature and distribution of muscle and fascia influences the strength of the repair, particularly in different parts of the abdominal wall. For example, a vertical lower midline incision along the linea alba, a strong layer of fascia, is less prone to incisional herniation than a paramedian incision, lateral to the midline

• The anatomy of underlying structures, particularly nerves —the incision line should run parallel to, but some distance away from the expected course of underlying structures, reducing the risk of damage. For example, to gain access to the submandibular gland, the incision is made 2 cm below the lower border of the mandible, to avoid the mandibular branch of the facial nerve

• Cosmetic considerations —wherever possible, incisions should be placed in the least conspicuous position, such as in a skin crease or a site that will later be concealed by clothing or hair, for example, a transverse suprapubic ( Pfannenstiel or bucket-handle) incision below the ‘bikini’ line for operations on the bladder, uterus or ovary, or a periareolar incision for breast biopsy

Dissection and Handling of Deeper Tissues

The skin consists of thin epidermis and dense, somewhat thicker dermis , as well as the underlying fatty hypodermis, which may be 10 or more cm thick in an obese individual.

Once the skin incision has been made, the scalpel is reserved mainly for incising fascia and other fibrous structures, such as breast tissue, and for very fine dissection. Anatomic detail is exposed and displayed by a combination of blunt and sharp dissection. Blunt dissection involves teasing or stripping tissues apart using fingers, swabs or blunt instruments, following natural tissue planes. Sharp dissection with scissors and forceps or scalpel is used where tissues have to be cut and also to display small structures. Some surgeons prefer sharp to blunt dissection in general, believing it causes less tissue trauma. Most dissection, however, involves a combination of both.

Clipping, Ligation and Underrunning

Ligation or specialised bipolar diathermy is obligatory when large vessels are divided and is desirable for vessels larger than about 1 mm calibre ( Fig. 10.1 ). If the end of a bleeding vessel cannot be grasped by haemostat forceps, a suture can be used to encircle the vessel and its surrounding tissues, a technique often described as underrunning . It is particularly useful for a bleeding artery in the fibrous base of a peptic ulcer.

Diathermy

Diathermy achieves haemostasis by local intravascular coagulation and contraction of the vessel wall caused by heating ( -thermy ), generated by particular electrical waveforms. However, enough heat is also produced to burn the tissues and these may be needlessly damaged by careless use, particularly near the skin, nerves or bowel. Ordinary diathermy is ineffective for large vessels, which should be ligated. There are three main variants of diathermy, illustrated in Fig. 10.2 , and all three modes are available on modern diathermy machines.

Monopolar diathermy is the most widely used for operative haemostasis but there is wide dispersion of coagulating and heating effects, making it unsuitable for use near nerves and other delicate structures. Since the current passes through the patient’s body, there is a risk of coagulating vessels en passant (e.g., monopolar diathermy used in circumcision may cause penile thrombosis and therefore it is essential that only bipolar diathermy is used on the penis), as well as provoking arrhythmias in patients with cardiac pacemakers. Monopolar diathermy may also result in skin burns at the indifferent electrode plate if skin contact is poor or if the plate becomes wet during operation. To improve contact, hair should be shaved from the skin where the plate is placed.

Bipolar diathermy is used mainly for finer surgery, digits and the penis. The current passes only between the blades of the forceps and it requires fairly accurate grasping of the bleeding vessel. It uses low levels of electrical power, there is almost no electrical dispersion from the tip of the forceps and much less heat is generated. The main advantages are minimal tissue damage around the point of coagulation and safety in relation to nearby nerves, blood vessels and cardiac pacemakers. Specialised computer-controlled bipolar diathermy is often used for larger vessels during laparoscopic surgery.

Cutting diathermy is mainly used for dividing large masses of muscle (e.g., during thoracotomy or access to the hip joint) and cutting vascular tissues (e.g., breast). The intention is a form of sharp dissection, at the same time coagulating the numerous small blood vessels as the tissue is cut; unfortunately, this is not always wholly effective. A blend of cutting and coagulation is sometimes used.

Tourniquet and Exsanguination

This technique is used in surgery of the limbs and hands where a bloodless field is desirable. For the whole limb, a pneumatic tourniquet is placed proximally. The limb is exsanguinated by elevation and spiral application of a rubber bandage (Esmark) or a ring exsanguinator from the periphery; the tourniquet is then inflated. Upper limb tourniquets must not be left inflated for more than 30 minutes and lower limb tourniquets for more than about 1 hour to avoid the risk of necrosis.

Pressure

Pressure is a useful means of controlling bleeding until platelet aggregation, reactive vasoconstriction and blood coagulation take over. It can be used for emergency temporary control of severe arterial or venous bleeding, but is equally useful for controlling diffuse small-vessel bleeding from a raw area, for example, liver bed after cholecystectomy. Pressure is usually applied with gauze swabs which must be kept in position for at least 10 minutes by the clock. Even if bleeding is not arrested completely, this process usually allows a clearer view and facilitates haemostasis by standard means.

For intractable bleeding which is not amenable to ligature, diathermy or suture, various resorbable packing materials, for example, oxidised cellulose, can be left in position until haemostasis occurs, allowing the wound to be closed. If bleeding simply cannot be controlled—for example, after liver injury—the bleeding cavity can be packed with gauze swabs which are left in situ and removed 48 to 72 hours later at a further operation. Bleeding, once controlled by this method, rarely recurs.

When a raw cavity has been created beneath the skin, external pressure dressings are sometimes a useful method of controlling potential superficial postoperative oozing and minimising haematoma formation.

Types of Suture Material and Needles

Numerous types of suture are available ( Box 10.5 ), with the most important distinction being between absorbable and non absorbable materials. The groups can be subdivided into natural and synthetic materials (although natural materials are being phased out) and further subdivided into monofilament and polyfilament (braided) materials. The choice of suture material depends upon the task at hand, the handling qualities and personal preference.