First intention

Rapid wound healing occurs by the approximation of wound edges soon after injury. This results in a narrow scar formation with superior cosmetic result. Most surgical skin incisions are closed, to heal by first intention.

There are three phases of wound healing:

Second intention

Contaminated wounds can be left open to heal by secondary intention. They may require debridement of debris and dead tissue first. The wound heals from the base upward with granulation tissue, and re-epithelialisation occurs from the skin edges.

Delayed primary closure

This is suitable for wounds where bacterial contamination is high and wound breakdown likely if closed immediately, e.g. anal surgery for fistula-in-ano. Healthy-looking wounds are closed after irrigation, debridement and a period of observation have occurred.

Skin grafting

This may be suitable for large, non-infected, healthy granulating wounds. Indications include burns, traumatic skin loss, ulcers, and wounds following excision of large skin tumours.

Classification of surgical wounds

Management of bleeding (haemostasis)

The optimal environment for wound healing is a dry wound with minimal ooze. Inadequate control of bleeding:

The main techniques used to stop bleeding are:

Wound closure

Wound closure can be achieved in a number of ways:

Details of these techniques are given in Chapter 23.

Contaminated wounds require adequate debridement, often in the operating theatre. These result from road traffic accidents, farming accidents or bomb injuries in civilian life. Gravel must be removed and all foreign bodies (FBs) extracted along with bits of clothing etc. X-rays to exclude deeper FBs are mandatory. Bites, human or animal, should be thoroughly cleaned and disinfected. Clean wounds may be primarily sutured but others should be left to granulate.

Blood products

The components of blood, e.g. red cells, platelets, fresh frozen plasma (FFP), are prepared from single donors whilst plasma derivatives, coagulation factor concentrates etc. are made from many donors.

Blood groups

Blood groups are determined by antigens on the red cell surface. There are over 400 different types, the most important being the ABO and rhesus (Rh) systems. Incompatibility transfusion reactions involving other blood groups can occur, resulting in haemolytic anaemia. Compatibility testing is always done by the transfusion service; donor blood of the same ABO and Rh group as the recipient is chosen. The patient’s serum is also screened for antibodies against other red cell antigens.

Most hospitals now have strict guidelines for the use and ordering of blood for operations and with new technology blood can be available within 20–30 minutes of a request even if the blood is not ‘grouped and saved’. The blood transfusion checking procedure is shown in Box 2.2.

Complications of blood transfusion

Alternatives to blood transfusion

Concerns about blood transfusion safety have resulted in alternative strategies for its use. Artificial haemoglobin solutions are being developed along with autologous blood transfusion and intraoperative blood salvage (e.g. the cell saver system).

Water

The basic principle behind fluid balance is that what goes out must come in. Water losses occurring through the skin, the lungs as water vapour, kidneys as urine and GI tract as faeces approximate to 2500 mL/day (Table 2.1).

Table 2.1 24-hour intake and output of water and electrolytes in health

These losses can be much greater due to pyrexia, vomiting and diarrhoea, bowel preparation, or intestinal obstruction. On average, 3 litres of fluid per day will be adequate for normal losses, but much greater volumes are required when there is a deficit to be made up.

Electrolytes

The main electrolytes are Na⁺ and K⁺. Sodium is lost mainly in the urine at 100 mmol/day with an additional 40 mmol lost in sweat. Potassium (also lost in urine) loss is 80 mmol/day. These amounts should be added to water replacement. A typical regime in a surgical patient might be 1 L 0.9% saline plus 20 mmol KCl in 8 hours followed by 1 L dextrose 5% plus 20 mmol KCl in 8 hours followed by another litre of dextrose 5% plus 20 mmol KCl in the final 8 hours of a 24-hour period. This gives 150 mmol Na⁺ and 60 mmol K⁺; this regime would of course only replace losses in a healthy patient, as these totals are the normal daily requirement. Alternating sodium-rich fluid with dextrose solution may be required if sodium-rich fluid is lost pre- or perioperatively.

In addition to losses suffered during an operation, surgical patients can also ‘lose’ fluids in the postoperative phase, e.g. during paralytic ileus into interstitial spaces (third space losses). These fluids will return to the normal spaces upon recovery, often seen in the diuretic phase after intestinal surgery or recovery from shock.

Metabolic acidosis

This is commonly seen in surgery where there is a failure of oxygen transport and excess acid production due to anaerobic metabolism (lactic acidosis). Fluid loss, bleeding or sepsis may cause peripheral circulatory failure (see Ch. 3). Initial compensation occurs in the lungs but when, for example, sepsis is prolonged, ventilatory failure also occurs. Mechanical ventilation often restores the balance whilst additional compensation is provided by the kidneys. If acidosis is persistent despite the above measures, intravenous administration of sodium bicarbonate may correct the situation.

Respiratory acidosis

Chronic lung disease is the commonest cause of this condition. The renal system compensates by excreting acid urine. Patients should have intensive pre- and postoperative physiotherapy to maximise their lung function or alternative methods of anaesthesia should be considered (e.g. epidural, local block). Patients often require prolonged weaning from ventilators due to a metabolic alkalosis induced by ventilation itself (high HCO₃^–), the renal system taking a long time to excrete the HCO₃^–.

Metabolic alkalosis

Gastric outlet obstruction is a cause of this situation due to prolonged vomiting and loss of HCl. Sodium and potassium loss compound the problem due to their preferential retention by the kidneys instead of H⁺. There is paradoxically acid urine in the presence of a metabolic alkalosis. Treatment consists of fluid and electrolyte correction allowing the kidneys to redress the alkalosis.

Respiratory alkalosis

Apart from the ventilatory problems described above, respiratory alkalosis may be seen in patients who hyperventilate (hysteria, panic attacks). Breathing into a paper bag to increase the level of inspired CO₂ usually stabilises the H₂CO₃ levels in the blood.

Measurement of acid–base balance

The pH, PO₂, PCO₂, standard bicarbonate, corrected bicarbonate and base excess/deficit can be easily measured on an arterial sample in a blood gas analysis machine. The base deficit figure may be used to calculate the amount of bicarbonate required to correct a metabolic acidosis, given by the equation: sodium bicarbonate infusion (mmol) = base deficit multiplied by weight (kg) divided by 3.

Infection control and prevention

The patient and healthcare worker both need protection. Risks emanate from both the environment and the patient’s own flora. Frequent handwashing and a mixture of (a) disinfectants that kill most pathogens but not spores or slow viruses, (b) antiseptics that can be used on living tissues and (c) sterilisation will prevent infection.

The patient is protected by knowledge of the risk factors that are associated with an increased risk of infection, namely (a) operations lasting more than 2 hours, (b) abdominal procedures, (c) endogenous or exogenous contamination and (d) more than three diagnoses for the patient. Aseptic surgical technique, preparation of the skin and bowel, and antibiotic prophylaxis reduce the risks substantially.

Antibiotic prophylaxis

Patients at high risk should be given antibiotic prophylaxis. The choice of antibiotic depends on the type of operation, the most likely organisms to be encountered, the likelihood of the development of resistance, and financial costs involved (risk management) (Table 2.2). Cephalosporins are widely used in general and orthopaedic surgery and given at the time of induction. Two further doses over 24 hours are sufficient thereafter. Antibiotics may be administered orally, rectally, intravenously or topically. Long-term prophylaxis, for example in post-splenectomy patients, is given to prevent overwhelming infections.

Principles of antibiotic usage

Intravenous administration of antibiotics is the route of choice in seriously ill patients, ensuring high serum levels. Oral therapy requires a functioning bowel and ability to tolerate by mouth. Topical antibiotics should be avoided as they lead to colonisation, resistance and sensitivity reactions.

The dose of antibiotic varies with the patient’s weight and age. Most paediatric doses are calculated to this formula, but adults tend to have a fixed dose despite their weight and their serum levels may therefore fluctuate to suboptimal levels. Aminoglycoside antibiotics need careful monitoring to achieve the therapeutic level required. The length of a prescribed course is debatable. Prophylactic prescriptions need only one dose, which must be given before the operation starts. The length of the course is based on the patient’s general condition. A 5–7 day course is the norm.

The choice of agent is often directed by microbiological advice. The more expensive drugs are not necessarily the best. A suggested list of antimicrobial chemotherapy is shown in Table 2.3.

Table 2.3 Common antibiotics and their uses

Infections acquired in hospital

Common sites include an operative site, in relation to a prosthesis, respiratory or GI tract translocation, urinary tract from catheters, infections from intravenous lines and cross-infection from any site (MRSA – see below).

Specific infections

Pulmonary embolism

The mortality of untreated PE is 30%. Symptoms include pleuritic chest pain, dyspnoea, haemoptysis, and collapse/loss of consciousness. There may be hypotension, raised jugular venous pressure, tachycardia and arrhythmias. Examination may elucidate a pleural rub, signs of consolidation and pyrexia. The most common clinical finding, however, is of sinus tachycardia alone.

Chest X-ray is normal or with a wedge of consolidation. CT pulmonary angiography is the quickest way to confirm the diagnosis. Radio-isotope scan (ventilation perfusion or V/Q scan) using technetium-99-labelled albumin demonstrates areas of underperfusion, but this is less frequently used. ECG changes include tall peaked P waves, right bundle-branch block and axis deviation and T-wave inversion. Blood gas analysis shows relative or absolute hypoxia, dependent on the percentage of inhaled oxygen given to the patient. Differential diagnosis includes myocardial infarction, severe fluid overload, sepsis, tension pneumothorax, cardiac tamponade and aortic dissection.

Treatment entails resuscitation and anticoagulation; thrombolysis is employed by some for massive PE but a significant risk of bleeding remains a major issue.

Nutritional support

Postoperative pyrexia

The cause of fever in a postoperative patient is not always apparent. Non-infective causes, e.g. DVT, haematoma and malignancy, should be borne in mind whilst new conditions (e.g. cholecystitis, pancreatitis, viral infections) may also be a possibility.

The most likely causes will, however, be:

Pre-assessment

Pre-assessment of patients for elective cases often occurs in an outpatient setting. A full history is taken of pre-existing co-morbidity, drugs and previous hospital admissions and reactions/problems with anaesthetics. Further investigations may be required to assess cardiac or respiratory status. Blood pressure medication may need to be reviewed and diabetes stabilised. The opportunity for fully informed consent can also be taken. A list of indications for preoperative investigations is shown in Table 2.4. An overall preoperative grading, using the American Society of Anesthesiologists (ASA) system, is decided (Box 2.10).

Table 2.4 Indications for preoperative investigations

Airway examination is mandatory to assess mouth opening, jaw protrusion, neck movement, dental condition and a view of the posterior pharyngeal structures. Increasingly, pre-medication is not a necessity, particularly with day-case surgery. The commoner complications of anaesthesia are shown in Box 2.11.

Local and regional anaesthesia

Many procedures can now be performed without a general anaesthetic. Local anaesthetic agents block the generation and propagation of nerve impulses at several sites, e.g. the spinal cord, spinal nerve roots, peripheral nerves and local nerves at the site of the procedure. Factors affecting the choice of regional anaesthesia are shown in Table 2.5. Overdose can occur and the maximum safe doses of commonly used agents are shown in Box 2.12. Local anaesthetic can be administered topically, subcutaneously, by Bier’s block (intravenous regional anaesthesia, see Box 2.13), nerve block or epidural/spinal routes. The anatomy of the latter is shown in Figure 2.1. Complications of spinal and epidural anaesthesia can be very serious, ranging from prolonged headache, prolonged hypotension and nerve root damage to epidural haematoma or abscess (which can result in paraplegia).

Table 2.5 Factors to consider in choosing regional anaesthesia

Figure 2.1 The anatomy of spinal and epidural anaesthesia.

Monitoring and charting the anaesthetised patient

Apart from clinical observation, standard monitoring is directed to the cardiovascular and respiratory systems (Box 2.14). Continuous ECG and automated blood pressure measurement are mandatory. Pulse oximetry provides continuous oxygenation information. Measurement of exhaled gases also occurs, indicating if ventilation is adequate. Complex cases often utilise further monitoring, e.g. intra-arterial lines, central venous pressure measurement, cardiac output devices (e.g. oesophageal Doppler) and urine output. All these methods carry a small measure of morbidity and complication rate. However, it is increasingly recognised that optimal fluid management using these devices optimises outcome and shortens in-patient hospital stay.

The anaesthetic machine also needs monitoring. This is achieved by a variety of devices, namely: flow meters, vaporisers, and the ventilator, all of which have alarm systems in place to detect malfunction.

The agents used during the procedure may be classified into:

The criteria for discharge from the recovery unit are shown in Box 2.15. Specific signs that may be important in the early postoperative phase are shown in Table 2.6.

Table 2.6 Specific signs that may be important in the early postoperative period

Pain and its relief

Tissue damage (surgical intervention) causes release of pain mediators (e.g. histamine, bradykinins) at the site of injury. Nerve fibres are stimulated to transmit the sensation of pain via the spinal cord to the brain. Anti-inflammatory agents can inhibit release of pain mediators, whilst local blocks prevent impulses reaching the brain. Opiate analgesics exert a central effect.

Post-operative pain is inevitable for most patients. It can have serious physiological and psychological consequences (Table 2.7). Intensity of pain is influenced by cultural and family background, personality, past experience and motivation. Pre-operative literature can inform and allay anxiety while a calming, reassuring attitude from the medical and nursing staff will contribute to pain reduction. Pain management has become a subspecialty in its own right and principles only will be discussed here.

Table 2.7 Effects of postoperative pain

Therapy

All agents are better given on a regular basis. Mild pain may be treated with NSAIDs and paracetamol. Moderate pain responds well to mixtures of codeine and paracetamol. Narcotic analgesics (e.g. morphine) are widely used for severe pain and are delivered in a variety of regimens (orally, subcutaneous infusion, intramuscularly and intravenously, more often controlled by the patient – PCA) (Table 2.8). A combination of these drugs usually produces the best results. Pre-emptive analgesia before the operation has been started is also useful (e.g. infiltrating the skin prior to incision).

Table 2.8 Standard postoperative analgesia regimens (fit, adult, male, 70 kg)

PCA, patient-controlled analgesia.

The management of chronic pain is a complex subject managed by anaesthetists with an interest in this area. The skills of a number of other specialists are enlisted including psychologists, physiotherapists and relaxation therapists. Antidepressants are increasingly used in this field.