ANAESTHESIA FOR TRANSURETHRAL RESECTION OF THE PROSTATE (TURP)

Mark Porter, Royal United Hospital, Bath, Bruce McCormick, Bristol Royal Infirmary, Bristol

INTRODUCTION

TURP is a cystoscopic procedure used to alleviate the symptoms of bladder outflow obstruction, usually caused by benign prostatic hypertrophy (BPH). BPH affects 50% of males at 60 years and 90% of 85-year-olds and so TURP is most commonly performed on elderly patients, a population group with a high incidence of cardiac, respiratory and renal disease. The mortality rate associated with TURP is 0.2-6%, with the commonest cause of death being myocardial infarction. Safe anaesthesia depends on the detection and optimisation of co-existing diseases, and on weighing up the relative risks and benefits of regional and general anaesthesia for each patient.

The operation is performed under direct vision using a diathermy current passed through a loop of wire at the tip of a resectoscope, which is inserted into the bladder through the patient's urethra. This enables the hypertrophied prostate to be resected in pieces and washed out using an irrigation solution. The most commonly used irrigation fluid is 1.5 % glycine solution, which has the advantages of being optically clear and non-electrolytic (and therefore does not conduct electric current). It has an osmolarity of 200mOsm/L which is much lower than that of blood, and large amounts of this hypotonic irrigation fluid, required to facilitate the procedure, may be absorbed systemically through the vascular prostate bed. This may cause several serious complications, which are discussed in this article.

PREOPERATIVE ASSESSMENT

Reduced functional reserve should be quantified, and the presence of any organ failure noted. If the patient has ongoing medical problems that can be improved before surgery, then TURP may need to be delayed.

A decision can then be made with the patient between regional and general anaesthesia, based on consideration of the advantages and disadvantages of each technique in their particular case. For some patients the risks of anaesthesia and surgery may outweigh the potential benefits of an elective procedure such as TURP.

History and examination

• Cardiovascular - Hypertension, ischaemic heart disease (IHD) and arrhythmias (particularly atrial fibrillation) are common. Patients with recent onset or poorly controlled heart failure have the highest perioperative mortality. Major risk factors for IHD (hypertension, diabetes, smoking, hypercholesterolaemia and family history) will raise the likelihood of silent perioperative myocardial ischaemia.
• Respiratory - Marked decrease in functional ability (e.g. inability to climb one flight of stairs) suggests severe disease. Inability to lie flat because of dyspnoea from cardiac or respiratory causes will make awake spinal anaesthesia poorly tolerated.
• Neurological - Confused patients may be not lie still during spinal anaesthesia.
• Musculo-skeletal - Degenerative changes in the vertebral column may make subarachnoid block (SAB) technically difficult. Arthritic joints or joint replacements are susceptible to damage or dislocation when the patient's legs are placed in the lithotomy position for the procedure.
• Renal impairment may occur due to obstructive uropathy
• Airway - Even if SAB is planned perform a full anaesthetic assessment (e.g. anticipated airway difficulties) in case the regional technique fails or is inadequate.
• Drug history - A high proportion of elderly patients take cardiovascular medications. Beta-blockers suppress the compensatory tachycardic response to hypotension associated with SAB or haemorrhage, but should generally be continued for prevention of perioperative myocardial ischaemia. ACE- inhibitors limit the renin-angiotensin mediated response to hypovolaemia that may be further impaired by SAB, and most anaesthetists omit them for 24 hours preoperatively. Alpha- blockers are commonly encountered as first-line medical treatment for BPH. The combined hypotensive effects of these drugs may precipitate severe hypotension after SAB. Warfarin has implications for both the anaesthetist (regarding SAB) and the surgeon (intra- and postoperative haemorrhage). If the INR is greater than 1.4 the procedure should be postponed until the INR is acceptable.

Investigations

Most patients are elderly and should have as routine:

• Full blood count or haemoglobin level
• Creatinine and electrolytes - this will detect renal impairment or overt renal failure, commonly secondary to obstructive uropathy.
• ECG for symptomatic patients, and routinely over 60 years
• Group and save - consider cross-matching blood for anaemic patients and those suspected of having large prostates on examination or ultrasound scan.

Other tests may be indicated in particular circumstances:

• Clotting studies (prothrombin time if on warfarin)
• Blood gas and pulmonary function tests (severe respiratory disease)
• Chest radiograph (worsening cardiac or chest disease / suspicion of metastases)
• Urinalysis (for glucose, protein, blood, white blood cells)
• Blood glucose
• Test for sickle cell disease or haemoglobinopathies in patients of African or Mediterranean extraction respectively.

CHOICE OF ANAESTHETIC

In the UK, 75% of TURPs are carried out under regional anaesthesia. Although regional anaesthesia in an awake patient has theoretical advantages, such as earlier detection of TUR syndrome (see below), the procedure can be equally successfully accomplished using a general anaesthetic technique. Short-term morbidity and mortality and long-term outcome are similar irrespective of the technique used. The decision is made after consideration of the individual's medical status and detailed discussion of the relative advantages and disadvantages of each technique.

The advantages of the regional technique include:

• Early detection of complications such as TUR syndrome and bladder perforation
• Possible reduced blood loss, requiring fewer transfusions
• Avoids effects of general anaesthesia on pulmonary pathology
• Good early post-operative analgesia
• Reduced incidence of post-operative DVT/PE
• Lower cost

The advantages of general anaesthesia are:

• Patients with chest disease may not tolerate lying flat or be able to suppress their cough  
• No time constraints. Although the procedure should be kept as short as possible - see later.
• May be less haemodynamically challenging than SAB in patients with cardiac problems such as aortic stenosis (and other fixed output states) and IHD
• Allows better control of CO₂, which may reduce bleeding from the prostatic bed
• Patient preference.

Anaesthetic Technique

Premedication

Consider relevant premedication if indicated: 

• Analgesics - give pre-emptive analgesia (paracetamol +/NSAIDs if not contra-indicated)
• Anxiolytics - consider a short-acting benzodiazepine if clinically indicated. In the elderly these drugs may result in postoperative confusion.

All patients should be fully monitored with blood pressure, pulse oximetry and ECG for SAB, including capnography, volatile agent levels, and airway pressure for general anaesthesia. A reliable, large-bore intravenous cannulae (14-16G) should be placed.

Subarachnoid block / spinal anaesthesia. (See Update 12)

• Check for any contra-indications to SAB (see table).
• A fluid preload with 500-1000ml of warmed saline 0.9% or Hartmann's is commonly given. Patients are likely to be dehydrated for a number of reasons including fasting and use of diuretics. Preloading assists compensation of the spinal-induced vasodilation and hypotension, and provides a small sodium load to counter the hyponatraemia that often occurs with TURP (discussed later).
• A confirmed block to at least T10 (level of the umbilicus) is required prior to the start of surgery. 2.5 to 3ml of plain or heavy bupivacaine 0.5% reliably achieves this, and provides up to 3 hours of dense motor and sensory blockade. This level of block does not usually cause severe hypotension, but vasopressors (ephedrine 3- 6mg, or metaraminol 0.5-1mg) should be immediately available. As a general guide, use ephedrine if the pulse is less than 60 per minute, and metaraminol if the pulse is over 60 per minute.
• Heavy lignocaine 5% 1.2-1.4ml can also be used, although the duration of block is unlikely to be reliable after 90min. Do not use lignocaine from multi-dose vials as these contain potentially harmful preservatives. Adding adrenaline 0.2mg to hyperbaric lignocaine will extend the block duration.
• Isobaric plain 2% lignocaine (with 0.2mg adrenaline to extend the block duration) in a dose of 2-2.5mL is also an appropriate choice.
• Consider intra-operative sedation for anxious or confused patients (e.g. IV midazolam 0.5-1mg as needed), but bear in mind that confusion may also be an early manifestation of the TUR syndrome (see later).
• Ideally a thermometer, warming blanket and fluid warmer should be available for the detection and prevention of hypothermia caused by the infusion of cold fluids and the effects of the irrigation fluid.
• All patients should be given supplementary oxygen.

General Anaesthesia

• Either a spontaneously breathing technique using a facemask or laryngeal mask, or a relaxant technique is appropriate, depending on the patient.
• Elderly patients are very susceptible to the hypotensive effects of induction and maintenance agents and have reduced requirements for volatile anaesthetic agents.
• Analgesic requirements can usually be met with pre-operative paracetamol and NSAID and increments of an opioid such as fentanyl, alfentanil or morphine. Further morphine in recovery is seldom required.
• Remember to consider the patient's renal function when using drugs that are excreted renally (e.g. morphine and nondepolarising neuromuscular blocking drugs other than atracurium).

Other considerations

• Following the initial fluid infusion, i/v fluids should be given to replace blood loss. Since irrigation fluid is continually absorbed during the procedure, maintenance fluids are not required.
• Urologists often request antimicrobial prophylaxis to cover the gram-negative bacteraemia. A single intravenous dose of gentamicin 3- 4mg/kg is suitable.
• Where available, consider invasive blood pressure monitoring in patients with severe cardiac disease.