Post-operative management

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Contents

Introduction

Good post-operative management will have started before the procedure with appropriate counselling and preparation (see Pre-operative management). This preparation will have included an assessment of fitness for the procedure and identification and management of any risk factors. The patient will have been provided with a clear explanation of the procedure (emergency or elective), the risk-benefits and the likely outcome. This will have included a description of what the patient should expect in terms of short- and long-term recovery from the procedure, possible complications and the necessity for any drains, stomas, catheters or other bits of tubing, normally alien to most of the population. The patient will have been reassured about pain control measures and, perhaps most difficult of all, the doctor will have tried to ensure that the patient's expectations match those of the health professional.

This chapter will focus on the care of the patient in the immediate post-operative period, up until the time of discharge from hospital. The immediate and short-term needs of the patient and care to be provided will depend on the magnitude and type of surgery.

Immediate management of the patient

Pain management

Pain relief is of paramount importance (see Anaesthesia and pain management) and an appropriate drug regimen will have been prescribed by surgeon and/or anaesthetist by the end of the procedure. In checking the charts of the patient after the procedure, care will be taken that these and any other medications required are prescribed and administered. These may include antibiotics prophylactic or therapeutic), sedatives, antiemetics and anticoagulants.

Monitoring

Depending on the nature of the procedure and the underlying state of health of the patient, the vital signs (blood pressure, pulse and respiratory state) will be measured and recorded regularly. If an arterial catheter has been inserted, blood pressure and pulse readings can be observed on a monitor constantly. The intensity and frequency of monitoring will be maximal in the recovery room and this level of scrutiny maintained if the patient is in an intensive care or high dependency area.

Measurement of the central venous pressure may be required for patients with poor cardiorespiratory reserve or where there have been large volumes of fluid administered or major fluid shifts are expected.

The patient chart will also record all fluid that has been given during and since the operation, together with fluid lost. Ideally, these figures will have been balanced by the end of the procedure, so that the duty of the attending doctor will be to monitor ongoing losses (digestive and urinary tracts, drains, stomas) and replace these. The normal daily fluid and electrolyte requirements will also be provided. If there has been major fluid shifts or if renal function is precarious, a urinary catheter will be inserted and regular (hourly) checks made of fluid losses. Serum electrolytes and haematological values will be checked frequently, again the frequency depending on any abnormalities present and the magnitude of any fluid and electrolyte replacement.

Mobilisation

Early mobilisation is encouraged. Unless there are specified orders to the contrary, all patients are encouraged to get up and move around as much as their underlying condition will allow. Obvious exceptions to this policy include patients with epidural catheters and those with severe multiple injuries. The aim of early mobilisation is to encourage good pulmonary ventilation and to reduce venous stasis. For those who cannot mobilise, physiotherapy should be provided to help with breathing and measures taken to either increase venous flow (pneumatic calf compression devices) or reduce risks of deep vein thrombosis (heparin). The timing of any planned heparin administration will depend on the nature of the procedure and the risks of haemorrhage from that procedure.

Communication

Most patients will seek some form of reassurance in the immediate post-operative period. They will want to know how the procedure went and how they are progressing. They will also want reassurance that all the tubes, lines and equipment to which they are attached are quite normal and not an indication of impending disaster. Any unexpected finding or complication encountered during the procedure should be discussed with the patient. The timing and detail of this discussion is a matter of fine judgement and may be best done in the presence of the patient's relatives.

Further care in the post-operative period

This covers the time from recovery from anaesthesia and initial monitoring to discharge from hospital. Wound care is discussed in Chapter 4.

Respiratory care

In the otherwise fit and healthy patient, maintenance of respiratory function is usually not a problem, particularly if there is optimal management of pain. Even with upper abdominal or thoracic procedures, most patients will require little respiratory support provided they are able to mobilise themselves and breathe unimpeded by pain. When assistance is required simple breathing exercises, with or without the help of a physiotherapist, is usually sufficient. Mechanical ventilation may be required in the early phase of recovery from a particular procedure. This can vary from prolonged endotracheal intubation, to intermittent positive pressure ventilation, to supplemental oxygenation by facemask or nasal prongs. In these instances the patient may require prolonged monitoring in an intensive care or high dependency unit with regular assessment of oxygen saturation (pulse oximetry and arterial blood gas analysis).

For less fit patients, and particularly those with chronic obstructive pulmonary disease, the risks of respiratory failure will be considerable and measures such as epidural local anaesthesia will be employed. Control of pain, attention to regular hyperinflation (inhalation spirometry and physiotherapy) and early mobilisation are the keys to preventing respiratory complications.

Fluid balance

Introduction

The three principles of management of fluid balance are:

  • correct any abnormalities
  • provide the daily requirements
  • replace any abnormal and ongoing losses.

Ideally, any abnormalities will have been identified and corrected before or during the surgical procedure. In the calculation of a patient's fluid requirements, there is a distinction to be made between the volume required to maintain the body's normal functions and that required to replace any abnormal losses. The normal maintenance fluid requirements will vary depending on the patient's age, gender, weight and body surface area.

Basic requirements

The total body water of a 70-kg adult comprised 45–60% of the bodyweight. Lean patients have a greater percentage of their bodyweight as body water and older patients a lesser proportion. Of the total body water, two-thirds is in the intracellular compartment and the other one-third is divided between plasma water (25% of extracellular fluid) and interstitial fluid (75% of extracellular fluid). Therefore, a lean individual weighing 70 kg would have a plasma water of 3 L, an interstitial volume of 11 L and an intracellular volume of 28 L, making a total volume of 42 L.

The normal daily fluid requirement to maintain a healthy 70-kg adult is between 2 and 3 L. The individual will lose about 1500 mL in the urine and about 500 mL from the skin, lungs and stool. Loss from the skin will vary with the ambient temperature.

The electrolyte composition of intracellular and extracellular fluid (ECF) varies (Table 6, “Electrolyte concentrations”). Sodium is the predominant cation in ECF and potassium predominates in the intracellular fluid (ICF). The normal daily requirements of sodium and potassium are 100-150 mmol and 60-90 mmol, respectively. This will balance the daily loss of these two cations in the urine.

Table 6. Electrolyte concentrations
Electrolyte Extracellular fluid (mmol/L) Intracellular fluid (mmol/L)
Sodium 135 10
Potassium 4 150
Calcium 2.5 2.5
Magnesium 1.5 10
Chloride 100 10
Bicarbonate 27 10
Phosphate 1.5 45

Replacement

If an otherwise healthy adult is deprived of the normal daily intake of fluid and electrolytes, suitable intravenous maintenance must be provided. One relatively simple regimen is 1 L of 0.9% saline and 1–2 L of 5% dextrose solution.

Both these solutions are isotonic with respect to plasma. The electrolyte solution contains the basic electrolyte requirements (154 mmol/L of sodium and 154 mmol/L of chloride) and the total volume can be adjusted with various amounts of dextrose solution. Potassium can be added as required. Other solutions (e.g. Ringer's lactate) may contain a more balanced make-up of electrolytes, but are rarely needed for a patient who is otherwise well and only requires intravenous fluids for a few days.

In the immediate post-operative period there is an increased secretion of antidiuretic hormone, with subsequent retention of water. In an adult of average build, maintenance fluids can be restricted to 2 L per day with no potassium supplements until a diuresis has occurred.

Fluid and electrolyte replacement is that required to correct abnormalities. Volume depletion and electrolyte abnormalities are relatively common in surgical patients, particularly those admitted with acute illnesses. Volume depletion usually occurs in association with an electrolyte deficit, but can occur in isolation. Reduced fluid intake, tachypnoea, fever or an increase in the ambient temperature may all lead to a unilateral volume loss. This will cause thirst and dehydration, which may progress to a tachycardia, hypotension and prostration. In severe cases there may be hypernatraemia and coma. Intravenous administration of 5% dextrose is used to correct the problem.

More often volume depletion is accompanied by an electrolyte deficit. Excessive fluid and electrolyte may be lost from the skin (e.g. sweating, burns), the renal tract (e.g. diabetic ketoacidosis) and the gastrointestinal tract (e.g. vomiting, ileus, fistula, diarrhoea). There is considerable scope for abnormal fluid losses in a surgical patient, particularly after a major abdominal procedure. There may be pooling of fluid at the operation site itself, an ileus might develop, fluid could be lost through a nasogastric tube or drains, and there might be increased cutaneous loss if there is a high fever.

The source of fluid loss will determine the type of electrolyte lost. There is considerable variation in the electrolyte content of different gastrointestinal secretions (Table 7, “Approximate electrolyte concentrations”). Loss from the upper digestive tract tends to be rich in acid, while loss from the lower tract is high in sodium and bicarbonate. Thus, patients with severe and prolonged vomiting from gastric outlet obstruction may develop a metabolic alkalosis.

Table 7. Approximate electrolyte concentrations
Secretions Sodium (mmol/L) Potassium(mmol/L) Chloride (mmol/L) Bicarbonate (mmol/L) Hydrogen (mmol/L)
Salivary 50 20 40 50 -
Gastric 50 15 120 20 70
Duodenal 140 5 80 - -
Biliary 140 10 100 40 -
Pancreatic 140 10 80 80 -
Jejuno-ileal 130 20 105 30 -
Faeces 80 10 100 25 -
Diarrhoea 100 30 50 60 -

While the management of maintenance fluid requirements can often be done on a daily basis, the fluid and electrolyte replacements needs of an acutely ill surgical patient is likely to be more involved and necessitate close monitoring and adjustment. Clinical assessment and appreciation of the types of fluid loss will give an approximate guide to the scale of the problem, but regular biochemical electrolyte estimations will be required to determine the precise needs of what needs to be replaced. In most instances, measurement of plasma electrolyte concentrations will provide sufficient information, but occasionally it may be necessary to estimate the electrolyte contents of the various fluids being lost.

Drains and catheters

Drains serve a number of purposes. They may be put down to an operative site or into a wound as it is being closed to drain collections or potential collections. Drains may also be put into the chest cavity to help the lungs re-expand. They may be put into ducts and hollow organs to divert secretions or to decompress that structure. Examples of decompression include insertion of a tube into the common bile duct after duct exploration or nasogastric intubation to decompress the stomach after surgery for intestinal obstruction. Sump drains are used to irrigate sites of contamination or infection.

Drains can act as a point of access for infection, and whilst this may be of little consequence if the tube has been put in to drain an abscess cavity, all efforts are made to reduce contamination of any wound. There is increased use of closed drainage systems and dressings around drains are changed regularly. Any changes to tubes or bags on drains must be carried out using aseptic techniques. Once a drain has served its purpose, it should be removed. The longer a drain stays in situ, the greater the risk of infection.

The contents and volumes discharged through a drain must be recorded. Large volumes, such as those from the gastrointestinal tract, may need the equivalent amount replaced intravenously.

Gut function

Some degree of gut atony is common after abdominal surgery, particularly emergency surgery. The condition is usually self-limiting and of little clinical consequence. There are three conditions that can produce massive gut dilatation and pose serious problems for the patient:

  • gastric dilatation;
  • paralytic (small intestine) ileus;
  • pseudo-obstruction (large intestine).

Gastric dilatation

Gastric dilatation is rare and when it occurs, tends to be associated with surgery of the upper digestive tract. It may occur suddenly 2–3 days after the operation and is associated with massive fluid secretion into the stomach, with the consequent risk of regurgitation and inhalation. Treatment is by insertion of a nasogastric tube and decompression of the stomach. Unfortunately, when gastric dilatation does occur, often the first indication of the problem is a massive vomit and inhalation after the dilatation has occurred. By then the damage is done and the value of a nasogastric tube at this stage is questionable. Traditionally, nasogastric tubes were used routinely for patients following laparotomy, particularly in the emergency setting. However, the nasogastric tube is often the patient's major source of irritation and discomfort in the post-operative period and its routine use should be abandoned.

Paralytic ileus

Paralytic ileus is less sinister and more common. In the acutely ill patient who has undergone surgical intervention for peritonitis, paralytic ileus may be present from the first post-operative day. Otherwise, it tends to make its presence felt about 5 days after operation, and the patient may have been making an apparently uneventful recovery. Abdominal distension occurs and the patient may vomit. Oral fluid restriction should be instituted and intravenous replacement may be required. Most cases resolve spontaneously. Occasionally a prokinetic agent may be considered.

Pseudo-obstruction

Classically, pseudo-obstruction occurs in the elderly patient who has recently undergone surgery for a fractured neck of femur. The condition is also often seen where there has been extensive pelvic or retroperitoneal injury and sometimes the condition appears to be more related to the use of opiate analgesia rather than the type of surgery itself. The atony, with abdominal distension and absence of bowel function, tends to occur 2-3 days after surgery (or from the time the injury was sustained). Pseudo-obstruction is often mistaken for mechanical obstruction and the dilatation of the colon and caecum can be massive. If the condition does not resolve spontaneously, colonoscopic decompression is usually successful. Occasionally, surgical intervention is required to prevent caecal perforation.

Important post-operative complications

Respiratory failure

If the patient's respiratory function deteriorates in the intermediate post-operative period, this is indicative of the development of a new problem. The important causes to consider are:

  • pulmonary embolus;
  • abdominal distension;
  • opiate overdose.

Depending on the initial state of respiratory function and the degree of deterioration, the patient may require anything from supplemental oxygen supplied by face mask to endotracheal intubation. A Pco2 above 45mmHg, a Po2 below 60mmHg and a low tidal volume all indicate that mechanical ventilation will be required. Once appropriate ventilatory support has been achieved, the cause of the respiratory failure can be addressed.

Wound failure

Provided the surgical procedure has a minimal risk of infection (see Surgical infections) and has been performed in an uneventful manner in a low risk patient, then the chances of problems with the wound are minimal and most such wounds can be left undisturbed until the patient leaves hospital. If there are identifiable risks the wounds may need to be attended to regularly. The problems that are likely to occur with wounds relate to:

  • Discharge of fluid
  • Collection of fluid
  • Disruption of the wound

Risk factors that may contribute to the above problems include those that:

There are general and local factors that increase the risk of breakdown of a wound. General factors include those that interfere with wound healing, such as diabetes mellitus, immunosuppression, malignancy and malnutrition. Local factors include the adequacy of wound closure, infection and anything that might put mechanical stress on the wound. For example, abdominal wound failure is a potential problem in the obese, and those with chest infections, ascites, or ileus.

In the early stages of wound healing any abnormal fluid at the wound site is likely to discharge rather than collect. The fluid may be blood, serous fluid, serosanguinous fluid or infected fluid of varying degrees up to frank pus. As discussed elsewhere in this chapter, the discharge of blood from a wound may have all sorts of consequences for the patient, which will vary from prompt opening of the neck wound of a patient with a primary haemorrhage after a thyroidectomy to evacuation of a haematoma after a mastectomy.

Serous fluid may be of little significance and be the result of a liquefying haematoma from within the depths of the wound. However a serosanguinous discharge from an abdominal or chest wound may herald a more sinister event, particularly if it occurs between days 5-8 after the operation. The discharge may have been preceded by coughing or retching. Such a wound is in imminent danger of deep dehiscence with evisceration. Should such an event occur, the wound must be covered in sterile moist packs and arrangements made to take the patient to the operating room for formal repair of the wound.

Collections in and under a wound may be blood, pus or seroma. As mentioned above, the rapidity with which a haematoma appears and any pressure effects such a haematoma may cause will determine its treatment. Collections of pus must be drained. Depending on its proximity or distance from the skin surface, an abscess may be drained by opening the wound or inserting (under radiological control) a drain into a deeperlying cavity. Seromas tend to occur where there has been a large area of dissection in subcutaneous tissues (e.g. mastectomy) or where lymphatics may be damaged (e.g. groin dissections). The seroma may not appear a week after the procedure. Seromas will lift the skin off the underlying tissues and impede wound healing. They also make fertile ground for infection. Seromas should be aspirated under sterile conditions and the patient warned that several aspirations may be required as the seroma may re-collect.

Confusion

Confusion in surgical patient is common and has many causes. Often the confusion is minor and transient and does not need treatment. The patient is typically elderly, has become acutely ill and in pain, is removed from the security and familiarity of their home surroundings, is subject to emergency surgery and more pain, is put in a noisy environment with strangers bustling around and is sleep-deprived. These factors alone would make many otherwise healthy individuals confused. Add to that recipe the deprivation of the patient from their regular medications (particularly alcohol), upset their body biochemistry, render them hypoxic and give them a concoction of opioids and other agents.

When a patient does become confused in the post-operative period, it is important to ensure that no easily correctable cause has been overlooked. Confusion is often secondary to hypoxia, where chest infection, oversedation, cardiac problems and pulmonary embolism need to be considered. Other important causes to consider include sepsis, drug withdrawal, metabolic and electrolyte disturbances and medications.

The management of the confused patient will include a close study of the charts, seeking information on any co-existing disease (particularly cardiorespiratory), drug record, alcohol consumption and the progress of the patient since the operation. Current medications should be noted, together with the nursing record of the vital signs.

If possible, try to take a history and examine the patient. Ensure that the patient is in a well-lit room and give oxygen by face mask. Attention should be focussed on the cardiorespiratory system, as this may well be the site of the underlying problem. Some investigations may be required to help determine the cause of the confusion. These might include arterial blood gas analysis, haematological and biochemical screens, blood and urine cultures, a chest X-ray and an electrocardiogram.

Most patients with post-operative confusion do not require treatment other than that for the underlying cause. However, the noisy, violent patient may need individual nursing care, physical restraint or sedation. Sedation should be reserved for patients with alcohol withdrawal problems, and either haloperidol or diazepam should be considered in such circumstances. Most hospitals have clearly defined protocols for the management of patients going through alcohol withdrawal. These correlate the anxiety, visual disturbances and agitation of the patient with the degree of monitoring and sedation required.

Pyrexia

The body's normal temperature varies and has a range between 36.5 and 37.5°C. The core temperature tends to be 0.5°C warmer than the peripheral temperature. Thus an isolated reading of 37.5°C has little meaning by itself and needs to be viewed in context with the other vital signs. Changes in temperature and the pattern of change are more important. A temperature that rises and falls several degrees between readings suggests a collection of pus and intermittent pyaemia, while a persistent high-grade fever is more in keeping with a generalised infection.

Fever can be due to infection or inflammation. In determining the cause of the fever the following should be considered:

  • the type of fever
  • the type of procedure which the patient has undergone
  • the temporal relationship between the procedure and the fever

Perhaps the most useful factor in trying to establish the cause of a patient's fever is the relationship between the time of onset of the fever and the procedure. Fever within the first 24 hours of an operation is common and may reflect little more than the body's metabolic response to injury. Atelectasis is common during this time and may produce a self-limiting low-grade fever.

A fever that is evident between 5 and 7 days after an operation is usually due to infection. While pulmonary infections tend to occur in the first few days after surgery, fever at this later stage is more likely to reflect infection of the wound, operative site or urinary tract. Cannula problems and deep vein thrombosis (DVT) should also be considered. A fever occurring more than 7 days after a surgical procedure may be due to abscess formation. Apart from infection as a cause of fever, it is important to remember that drugs, transfusion and brainstem problems can also produce an increase in the body's temperature.

A careful history, review of the charts and physical examination will usually determine the cause of the fever. The next stage in management will depend on the state of health of the patient. The fever of a septic process, which has led to circulatory collapse, will require resuscitation of the patient before any investigation. Otherwise, appropriate investigations may include blood and urine cultures, swabs from wounds and drains, and imaging to define the site of infection.

Treatment will depend on the severity and type of infection. The moribund patient will require resuscitation and an educated guess from the surgeon on which antibiotic regimen to use. Surgical or radiological intervention (e.g. to drain an abscess) may be required before the patient improves. However, the well patient may have antimicrobial therapy deferred until an organism has been identified (e.g. Gram stain or culture).

Deep vein thrombosis

Deep vein thrombosis may occur in spite of prophylaxis (see Pre-operative management). Presentation may be silent (60%) or as a clinical syndrome (40%) with calf pain and tenderness, oedema of the leg and/or pain on dorsiflexion of the foot (Homan's sign). Rarely, massive thrombosis occurs with gross swelling of the lower limbs and venous gangrene (phlegmasia caerulea dolens).

Investigations are essential to confirm the diagnosis prior to the commencement of therapy.

Ultrasonography and duplex scanning with Doppler ultrasound have a sensitivity and specificity greater than 90%. Lower limb venography is highly accurate but invasive and is rarely indicated.

Following diagnosis, urgent therapy is required, starting with heparin i.v. in a dose of 20,000-30,000 units per day. The patient is monitored by measurement of the activated partial thromboplastin time (APTT), which is kept at 1.5-2.5 times the control value. Heparin therapy is continued for 5-7 days and is replaced by oral vitamin K antagonists such as warfarin. The dose of warfarin is adjusted according to the thromboplastin time with reference to an international standard (INR). Heparin is discontinued when full anticoagulation has been achieved and the warfarin is continued for 3-6 months to minimise the risk of further thrombosis and the development of complications (see Leg swelling and Post-operative complications).

Oliguria

Oliguria is a common problem in the post-operative period and is usually due to a failure by the attending medical staff to appreciate the volume of fluid lost by the patient during the surgical procedure and in the immediate post-operative period. For example, the development of an ileus will lead to a large volume of fluid being sequestered in the gut and this ‘loss’ not being immediately evident. Before the apparent oliguria is put down to diminished output of urine, it is important to ensure that the patient is not in urinary retention. Such an assessment can be difficult in a patient who has just undergone an abdominal procedure. If there is any doubt, a urinary catheter must be inserted. Alternately, many wards are now equipped with ultrasonographic devices capable of providing an accurate estimation of the bladder content.

Diminished output of urine may be due to:

  • poor renal perfusion (pre-renal failure: hypovolaemia and/or pump failure)
  • renal failure (acute tubular necrosis)
  • renal tract obstruction (post-renal failure).

In the assessment of a patient with poor urine output (<30 mL/h), these three possible causes must be considered. Major surgery with large intraoperative fluid loss and periods of hypotension during the procedure might suggest renal tissue damage (acute tubular necrosis), while severe peritonitis with large fluid shifts and no hypotension would be more in keeping with inadequate fluid replacement.

The treatment of oliguria depends on the cause. Pre-renal hypovolaemia is treated by fluid replacement, while poor output secondary to pump failure requires diuretic therapy and perhaps medications (e.g. inotropes, anti-arrhythmics) to improve cardiac function. To give a hypovolaemic patient a diuretic in an attempt to improve urine output may be counterproductive and detrimental.

In acute renal failure the oliguria will not respond to a fluid challenge. Management demands accurate matching of input to output, monitoring of electrolytes and even dialysis.

In summary, most cases of post-operative oliguria are secondary to hypovolaemia, and should be considered to be due to hypovolaemia until proven otherwise.

Hyponatraemia

Any reduction in the sodium concentration in the ECF may be absolute or secondary to water retention. Loss of the major cation from the ECF leads to a shift of water into the ICF. Any clinical manifestation will reflect the expansion of the ICF (e.g., confusion, cramps and coma secondary to cerebral oedema) or the contraction of the ECF in absolute hyponatraemia (e.g. postural hypotension, loss of skin turgor).

Hyponatraemia due to a decreased total body deficiency of sodium is an unusual scenario in the post-operative surgical patient. Any hyponatraemia that occurs tends to be due to dilution and is caused by the administration of an excessive amount of water. While this is a fairly frequent biochemical finding, it rarely leads to any clinically significant problem.

Any hyponatraemia secondary to dilution may also occur with inappropriate antidiuretic hormone (ADH)secretion. The trauma of major surgery will produce an increase in ADH secretion and intravenous fluid must be administered judiciously in the immediate post-operative period. A safe rule of thumb is to restrict the patient to 2 L per day of maintenance fluid until a diuresis has been established. Hyponatraemia can usually be corrected by the administration of the appropriate requirements of isotonic saline. If the patient has a severe hyponatraemia and associated mental changes; an infusion of hypertonic sodium solution may be required.

Hypernatraemia

Hypernatraemia in the post-operative patient is a less common problem that hyponatraemia. Any hypernatraemia is usually relative rather than absolute and occurs secondary to diminished water intake. Patients with severe burns or high fever may also develop hypernatraemia. An increase in the plasma sodium concentration will lead to a loss of ECF volume and relative intracellular desiccation. The first clinical manifestation is thirst and if the hypernatraemia is allowed to persist, neurological problems (e.g. confusion, convulsions, coma) may ensue. Treatment is by administration of water by mouth or intravenous 5% dextrose.

Hyperkalaemia

With normal renal function, severe and life-threatening hyperkalaemia is rare. High concentrations of potassium in the ECF can be associated with cardiac rhythm disturbances and asystole. Hyperkalaemia may occur in severe trauma, sepsis and acidosis. Emergency treatment of arrhythmia-inducing hyperkalaemia consists of rapid infusion of a 1 L solution of 10% glucose with 25 units of soluble insulin. The insulin will help drive potassium into the cells and the glucose will help counteract the hypoglycaemic effect of the insulin. At the same time 20 mmol of calcium gluconate can be given to help stabilise cardiac membranes. If an arrhythmia has already developed the calcium gluconate should be given before the dextrose and insulin. Sodium bicarbonate (20-50 mmol) can be given if the patient is acidotic. If the level of potassium is not too high, an ion-exchange resin (resonium) can be given. These resins can be given by enema and they exchange potassium for calcium or sodium. Alternatively, the patient may be dialysed (peritoneal or haemodialysis). In the management of hyperkalaemia it is obviously as important to treat the cause as it is to treat the effect.

Hypokalaemia

Low levels of potassium in post-operative patients are common but hypokalaemia is rarely so severe as to produce muscle weakness, ileus or arrhythmias. Patients with large and continuous fluid loss from the gastrointestinal tract are prone to develop hypokalaemia. If potassium supplements are required they may be given either orally or intravenously. If by the latter route, the rate of infusion should not exceed 10 mmol/h. Faster rates may precipitate arrhythmias and should only be undertaken on a unit where the patient can be monitored for any ECG changes.

Haemorrhage

The management of haemorrhage in the post-operative period may be approached in several ways. In broad terms, bleeding may be classified as either localised or generalised. If the former, it may be classified as follows:

  • primary (bleeding which occurs during the operation)
  • reactionary (bleeding within the first 24 hours of the operation)
  • secondary (bleeding occurring at 7-10 days after the operation)

If localised, the bleeding is usually related to the operative site and/or the wound. Occasionally, the bleeding may be at a point removed from both these areas, for example gastrointestinal haemorrhage from a stress-related gastric erosion. Bleeding from the wound site is usually indicative of a mechanical problem or local sepsis. Generalised bleeding may reflect a coagulation disorder and may be manifest by the oozing of fresh and unclotted blood from wound edges and with bleeding from sites of cannula insertion.

Most cases of reactionary (and primary) haemorrhage are from a poorly ligated vessel or one that has been missed, and are not secondary to any coagulation disorder. The bleeding point may go unnoticed during the operation if there is any hypotension, and makes itself known only when the patient's circulating volume and blood pressure have been restored to normal. The bleeding in secondary haemorrhage is due to erosion of a vessel from spreading infection. Secondary haemorrhage is most often seen when a heavily contaminated wound is closed primarily, and can usually be prevented by adopting the principle of delayed wound closure.

Post-operative haemorrhage can also be classified according to its clinical presentation. The most common forms are wound bleeding, concealed intraperitoneal bleeding, gastrointestinal haemorrhage and the diffused ooze of disordered haemostasis.

The approach to management will depend on the overall condition of the patient and the assessment of the type of bleed. A stable patient with a localised blood-soaked dressing will be managed differently from a hypotensive patient with 2 L of fresh blood in a chest drain, who in turn will be managed differently from a patient with a platelet count of 15 × 109 L-1 and fresh blood oozing from all raw areas.

In the first case the tendency might be to apply another dressing in an attempt to achieve control by pressure. A more positive approach is to remove the dressing and inspect the wound. In most instances, a single bleeding point can be identified and controlled. In the next case, the patient has a major bleed and this is probably from a bleeding vessel within the operative site. Return to the operating room and formal reexploration must be seriously considered. In the third case, the prime problem is one of an anticoagulation defect requiring urgent correction.

The diagnosis of post-operative haemorrhage is a clinical one, based on knowledge of the surgical procedure, the post-operative progress and an assessment of the patient's vital signs. The blood loss may not always be visible and could be concealed at the operative site or within the digestive tract. The treatment of post-operative haemorrhage depends on the severity of the bleed and the underlying cause. Hypovolaemia and circulatory failure will demand urgent fluid replacement and consideration of the likely cause and site of bleeding. Careful consideration must be given to control of localised haemorrhage and whether re-operation is warranted.

Vomiting

The causes of vomiting after surgery are many, and can be best determined by establishing the relationship between onset of vomiting and the time of the operation. The two most common causes of post-operative vomiting are drug-induced and gut atony.

Vomiting that occurs in the immediate post-operative period is usually drug related. If it is due to the effects of anaesthesia, vomiting will usually settle within 24 hours. Current anaesthetic techniques and modern anti-emetics have rendered nausea and vomiting a relatively minor post-operative problem for most patients.

Vomiting that occurs several days after operation may still be drug related, but in this instance is usually due to an opiate rather than an anaesthetic agent. Vomiting may be secondary to gut stasis, and this atony is usually self-limiting. If prolonged, a prokinetic agent can be effective.

If vomiting starts 7 days or so after abdominal surgery, a mechanical cause for the problem should be considered.
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