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Chapter 14 – General surgery

General principles of anaesthesia for laparotomy
Laparotomy is a major physiological insult. Perioperative complications are common and often unpredictable. Even after ensuring that the patient’s physiological status is optimized, fluid replacement and analgesia are adequate, and appropriate monitoring is carried over into the postoperative period, complications may still occur. High dependency or intensive care is often appropriate.
General considerations
Anaesthesia is usually straightforward in the young patient having simple bowel resection. However, abdominal surgery is more common in elderly people compromised by underlying disease, undergoing prolonged procedures associated with major fluid shifts and cardiorespiratory stress. Recent studies on optimization have shown that close attention to anaesthetic detail, particularly ensuring an adequate circulating volume and cardiac output, is associated with an improved outcome. In some hospitals a proportion of these patients are admitted to HDU/ICU prior to surgery, although this is not routine in the United Kingdom.
Preoperative
  • Ischaemic heart disease and cardiac failure increases the risk of surgery and should be optimally controlled.
  • Respiratory function should be optimized and physiotherapy commenced before surgery. Examine the chest radiograph if available.
  • Consider overnight IV fluids prior to operation if creatinine is high, patient is jaundiced or dehydrated, or if fluid intake inadequate. Bowel preparation can result in significant hidden dehydration.
  • Exclude contraindications to regional anaesthesia, e.g. patient refusal, infection around proposed site of epidural, coagulation disorders.
  • Discuss analgesia options and obtain at least verbal consent if a central neuraxial block considered.
  • Check the thromboprophylaxis regimen (ensure low molecular weight heparins are given at least 12 h in advance of neuraxial block).
  • Discuss rapid sequence induction, if this is required. Consider ranitidine or omeprazole premedication.
  • Consider whether HDU/ICU care is indicated perioperatively and book bed if appropriate.
Perioperative
  • Large bore IV access. Gaining extra IV access during surgery may be difficult especially if the patient is in the lithotomy position.
  • Start IV infusion as soon as the patient arrives in the anaesthetic room/theatre if it has not been started preoperatively. Long extension sets may be required.
  • Hypotension is common following induction (relative dehydration) and may require the use of vasopressors.

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  • Check if a nasogastric tube is required—ask the surgeon to check the position during surgery.
  • Prophylactic antibiotics (p. 896).
  • Establish appropriate invasive monitoring.
  • Establish active patient warming, e.g. fluid warmer, hot air blanket, insulation.
  • Postoperative nausea and vomiting are common, consider an antiemetic in theatre, and prescribe postoperatively.
  • Keep one arm out on an arm support to allow vascular access and neuromuscular monitoring.
  • Be prepared for the lithotomy position and head down tilt—may need PEEP to maintain oxygenation.
  • Muscle relaxation is essential until the abdomen is closed (this helps the surgeon).
  • Empty stomach if appropriate by aspirating the nasogastric tube before waking up and extubating.
Postoperative
  • Continue active patient warming.
  • Prescribe postoperative supplemental oxygen for up to 72 h.
  • Arrange a check chest radiograph if a CVP line sited intra-operatively.
  • Continue close monitoring of fluid status. Frequent monitoring of pulse, blood pressure, urine output, CVP (if appropriate), fluid loss (urine, drains, ileostomy, blood, etc.), and conscious level. In high-risk patients and following major surgery measure urine output hourly for at least 48 h.
  • Consider daily FBC and U+E until normal bowel function returns. Correct electrolyte abnormalities and anaemia.
  • Monitor and treat pain.
Perioperative mortality and morbidity
Surgery and anaesthesia for intra-abdominal procedures carries a high risk of complications. Upper abdominal procedures have an increased risk compared with lower gastrointestinal procedures. Significant complications primarily affect the respiratory, cardiovascular, and renal systems. Mortality rates associated with intra-abdominal procedures may be as high as 5%, with upper abdominal surgery twice as likely to result in death than lower abdominal procedures. In studies on postoperative mortality, deaths following cardiac, vascular, and abdominal surgery represent 60–80% of all deaths reported. Predictors of severe adverse perioperative outcome (including death) include a history of CCF/MI less than 1 year ago, ASA 3 or 4 and age >50 years.
Intra-operative invasive monitoring
When to use invasive monitoring is controversial. Consider the extra information it will provide against the possible risks involved.
Postoperative paralytic ileus
Bowel function begins to return 24–36 h postoperatively, but does not return to normal until 48–72 h. Prolonged ileus leads to collection of fluid and gas in

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the bowel resulting in distension, increased pain, nausea, vomiting, and delayed discharge. The aetiology of ileus is multifactorial and includes:

  • manipulation of the bowel
  • hormonal stress response
  • increased sympathetic activity
  • postoperative pain
  • immobility
  • opioids
  • hypokalaemia.
Suggested indications for invasive monitoring
Central venous pressure large fluid shifts, major blood loss, CVS or renal compromise, inotropes, prolonged surgery
Arterial line Major blood loss, unstable patient, arrhythmias, CVS compromise, blood gas sampling
Oesophageal Doppler Monitors beat by beat pulse waveform and can indicate inadequate filling, pump performance, and afterload. Will determine whether fluids, inotropes, vasodilators, or vasoconstictors are needed
Pulmonary artery catheter Where difference is expected with performance between left and right side of heart, cardiac failure
Analgesia
Abdominal incisions are extremely painful for several days following the operation and can be associated with changes in FRC and ability to cough. In general three levels of analgesia are used:
  • Simple IM/SC opioids for less invasive procedures, e.g. appendicectomy, reversal of colostomy.
  • Opioids by continuous intravenous infusion or PCA can be used, particularly for lower abdominal procedures. Continuous infusion techniques can be particularly effective in the elderly population who may be confused postoperatively and unable to utilize a PCA (ensure additional oxygen therapy and hourly sedation/pain scoring).
  • Epidural techniques, which may be particularly beneficial for upper abdominal surgery, prolonged procedures, and high-risk patients
Regular paracetamol (PO/PR) and NSAIDS when appropriate should also be prescribed.
Epidural analgesia
This is commonly used for patients undergoing laparotomy. Advantages include:
  • Improved pain relief. Thoracic epidurals using local anaesthetic and/or epidural opioids provide superior analgesia compared with systemic opioid analgesia. Epidural opioids improve analgesia compared with local anaesthetic alone. Effectiveness relies on appropriate placement. The catheter

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    should be placed at a level corresponding to the dermatome innervating the middle of the abdominal incision. The range for abdominal incisions is usually T6–T12. Failure of analgesia is common if the catheter is placed too low.

  • Improved postoperative gastrointestinal motility. Improved recovery of bowel motility is seen with appropriately used epidural catheters due to reduced inhibitory gastrointestinal tone and increased intestinal blood flow. Low-dose epidural opioids do not seem to decrease intestinal motility. Improved postoperative patient mobilization.
  • Improved postoperative respiratory function resulting in a reduced incidence of pneumonia, respiratory failure, and radiological markers of pulmonary complications, e.g. atelectasis.
  • Potentially improved myocardial oxygenation. Pain, activation of the sympathetic nervous system, and the stress response can increase heart rate, coronary vasoconstriction, and myocardial workload, increasing the risks of myocardial ischaemia and infarction.
  • Reduction in thromboembolism.
  • Reduced sedation and postoperative nausea/vomiting.
  • Possible reduction in overall mortality.1
Disadvantages associated with the use of epidurals include:
  • Risks related to placement of the epidural catheter.
  • Epidural failure (can be as high as 30% for postoperative analgesia).
  • Perioperative hypotension. This should be treated aggressively depending on the aetiology.
  • Postoperative motor blockade impeding patient mobilization.
  • Itching associated with epidural opioids.
Practical considerations for epidural analgesia
  • The catheter should be sited at an appropriate level to provide analgesia to the site of the skin incision (T10–T11 for lower abdominal procedures, T8–T9 for upper abdominal procedures). Siting the epidural awake is probably safer—patient feedback during insertion can be useful in alerting the anaesthetist to potential problems.
  • Intra-operatively. Epidural loading dose 50–100 µg fentanyl in 8–10 ml 0.5% bupivacaine (divide into 4–5 ml boluses) and assess response. Top up with 3 ml 0.25% bupivacaine as needed. Bupivacaine takes 15–20 min to achieve its maximum spread and top ups should be performed cautiously. Intravenous supplementation with a short-acting opioid or an increase in the volatile agent may be required until the block is sufficient. An extensive sympathetic block may develop with relatively low volumes of local anaesthetic.

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  • Where extensive bleeding is expected, or in patients who are cardiovascularly unstable, it is often wise not to use epidural local anaesthetic until postoperatively. Epidural opioids alone are often a safer option.
  • The effectiveness of epidurals varies during surgery. Surgeons manipulating organs or pulling on mesentery may cause stimulation, even with a good block. AP resection (which requires analgesia and anaesthesia across thoracic, lumbar, and sacral dermatomes) can prove problematic. Effectiveness of the epidural can be improved with the use of epidural opioids and larger volumes of weak anaesthetic solution, e.g. 0.125% bupivacaine. Despite this it can be difficult to effectively anaesthetize sacral dermatomes and it may be necessary to supplement with systemic analgesia/anaesthesia. Use shortacting opiates, e.g. remifentanil, alfentanil, fentanyl, to reduce postoperative complications. The epidural catheter should still be sited in the low thoracic region as the major source of pain relates to the abdominal incision.
  • Treat hypotension with fluids and vasopressors. Ensure renal perfusion is maintained and avoid prolonged periods of relative hypotension.
  • Postoperatively an appropriate regime consists of a mixture of local anaesthetic and opioid, e.g. bupivacaine 0.167% + diamorphine 0.1 mg/ml (2–8 ml/h), bupivacaine 0.125% + fentanyl 4 µg/ml (2–8 ml/h).
  • Epidural analgesia may not be appropriate in very sick/septic patients undergoing emergency laparotomy for intra-abdominal obstruction/catastrophe. Problems with persistent hypotension may limit the analgesic effect and compromise renal blood flow, plus increased risks of epidural haematoma/infection.
  • If an epidural is contraindicated use IV morphine in theatre and recovery and then PCA or a morphine infusion postoperatively.
Temperature control
Patients undergoing general anaesthesia become hypothermic due to:
  • anaesthetic-induced impairment of thermoregulatory control
  • a cool operating environment
  • surgical factors promoting heat loss.
Hypothermia develops with a characteristic three-phase pattern.
  • Phase 1: redistribution of body heat as the tonic vasoconstriction that normally maintains the core to periphery temperature gradient is inhibited. Occurs during the first hour and results in a reduction in core temperature of 1–1.5 °C.
  • Phase 2: core temperature then decreases linearly at a rate determined by the difference between heat production and heat loss. Patients undergoing an operation under general anaesthesia not only have increased losses (radiation, conduction, convection, evaporation) but also have a reduced metabolic rate and therefore reduced heat production. Lasts 2–3 h.
  • Phase 3: when core temperature drops to a sufficiently low value vasoconstriction is triggered and the temperature reaches a plateau phase of about 3–4 °C below normal.
Efforts to reduce operative hypothermia are aimed at preventing the linear decrease in phase 2 and increasing the total body heat to minimize the drop in core temperature seen with redistribution. This involves:
  • An HME filter which humidifies and warms inhaled gases reducing losses from the respiratory tract.

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  • A fluid warmer to prevent conductive heat loss associated with the administration of cold fluids.
  • A hot air warming blanket reducing radiation loss and increasing total body heat.
  • Insulation to exposed areas, e.g. the wrapping the head reduces heat loss.
Patients undergoing laparotomy have large increases in heat loss compared to those normally associated with anaesthesia. If a thoracic epidural is used, the compensatory vasoconstriction responsible for phase 3 is lost and severe hypothermia can occur. Every effort must be made to avoid hypothermia and its complications. In recovery the residual effects of general anaesthesia, continued epidural vasodilatation, inhibition of shivering, and continuing fluid administration can result in further hypothermia. The above techniques should be carried over into recovery.
Fluid management
Fluid loss occurs pre-, intra-, and postoperatively in patients undergoing laparotomy. Causes of fluid loss include:
  • Preoperative: reduced fluid intake secondary to the underlying disease process, increased fluid losses, e.g. ileostomy, vomiting, laxative use for bowel preparation, preoperative starvation.
  • Intra-operative: large evaporative losses from the peritoneal cavity through the abdominal incision, sequestration of fluid into the omentum and bowel lumen (third space loss), blood loss, evaporative loss from the respiratory tract, urine production, nasogastric losses.
  • Postoperative: ongoing sequestration of fluid into the omentum and bowel (paralytic ileus), ongoing losses from the nasogastric tube, urine production, ongoing blood loss.
These losses must be replaced with an individualized fluid regime. Those with large preoperative fluid deficits should have IV fluids preoperatively on the ward or HDU. Losses should be carefully charted on a regular basis particularly nasogastric drainage, blood loss, and urine output. During surgery, crystalloid maintenance rates are between 10 and 30 ml/kg/h. For prolonged procedures, requiring large volumes of crystalloid, Hartmann’s solution is preferable.
Nasogastric tubes
When deciding on which nasogastric tube to use consider:
  • duration of use
  • the indication
  • diameter.
Duration
With prolonged use, complications such as local tissue irritation/ necrosis/ perforation (nares, nasopharynx, oesophagus, stomach), and degradation of the nasogastric tube become more pertinent. The most important consideration in preventing these complications is the material that the nasogastric tube is made from. The maximum recommended durations of use for the various materials used in the manufacture of nasogastric tubes are:
  • PVC 1 week
  • polyurethane 2–4 weeks
  • silicone >4 weeks.

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Indication
There are four basic types of nasogastric tube:
  • Gastric tube: approximately 100 cm long with an open-ended, nonweighted tip. This is the most basic type of tube. The open-ended tip allows easier aspiration and wash out of the stomach but at the expense increased risk of trauma to the stomach wall, i.e. ‘tissue grab’ during process of aspiration.
  • Leven gastro-duodenal tube: approximately 125 cm long with closed nonweighted tip. Reduces the risk of tissue grab and is long enough to pass into the duodenum/jejunum if nasogastric feeding is likely.
  • Ryles tube: approximately 125 cm long with the same characteristics as Leven tube except that the tip is weighted using tungsten. The tungsten weight makes passage of the tube into the stomach easier and aids peristalsis in moving the tube tip out of the stomach and into the small intestine.
  • Salem sump tube: approximately 100 cm long with a closed non-weighted tip. At the proximal end there is a sump tube, which if left open to reduces tissue grab even when negative pressure is applied to the nasogastric tube. These tubes are designed for active decompression of the GIT using continuous gentle aspiration.
Diameter
Nasogastric tubes come in a range of diameters from 8–18 FG. The bigger gauge the easier it is to drain and decompress the stomach but the greater risk of tissue grab and patient discomfort. One of the main complaints patients following laparotomy is discomfort and pain related to the nasogastric tube.
For most laparotomies a PVC/polyurethane 16 FG Ryles or Salem tube adequate. For procedures such as a laparoscopic cholecystectomy, where decompression of the stomach aids surgical access or where active decompression of the GIT is anticipated postoperatively, then the Salem tube is preferable.
Operation Description Time (h) Pain Position Blood loss (litres) Notes
Hemicolectomy Resection of right or left hemicolon 1–3 ++++ Supine 0.5 Low thoracic epidural or opioid infusion/PCA
Sigmoid colectomy Resection of sigmoid colon with bowel anastomosis 1–3 ++++ Supine. Head down. May need Lloyd-Davies 0.5–1.0 Low thoracic epidural or opioid infusion/PCA
Hartmann’s procedure Resection of sigmoid colon with colostomy 1–3 ++++ Supine. Head down. May need Lloyd-Davies 0.5–1.0 Low thoracic epidural or opioid infusion/PCA
Anterior resection Resection of rectum 2–3 ++++ Head down. Lloyd Davies 0.5–1.5 Low thoracic epidural
AP resection Resection of rectum and anus 2–4 +++++ Head down. Lloyd Davies 0.5–2.0 Low thoracic epidural. Can be difficult to block sacral nerve roots. CVP line
Gastrectomy Resection of gall bladder 2–3 +++++ Supine 0.5–1.0 High thoracic epidural, Consider CVP/art line
Cholecystectomy Resection of gall bladder 1 +++ /++++ Supine 0.5 Right upper quadrant incision. PCA
Closure of loop colostomy or loop ileostomy Local closure of colostomy or loop ileostomy 0.5–1 ++ Supine ns Still requires muscle relaxation. May need PCA. If difficulties arise can proceed to more extensive procedure
Reversal of Hartmann’s Laparotomy. Bowel ends re-anastomosed 1–2.0 ++++ Supine. Head down. May need Lloyd Davies 0.5–1.5 Low thoracic epidural
Footnote
1

Rodges A et al. (2000). Reduction of postoperative mortality and morbidity with epidural or spinal anaesthesia: results from overview of randomised trial. British Medical Journal, 321, 1493.
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