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TURP Syndrome

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I now have comprehensive information from two authoritative anesthesiology textbooks. Here is a thorough overview of TURP Syndrome.

TURP Syndrome

Definition

TURP syndrome describes a constellation of symptoms caused by systemic absorption of large volumes of hypotonic, electrolyte-free irrigating fluid during transurethral resection of the prostate (or similar endoscopic procedures). The result is a combination of hypervolemia, dilutional hyponatremia, hypoosmolality, and solute toxicity from the irrigant itself. — Miller's Anesthesia, 10e

Why It Happens

During monopolar TURP, isotonic saline cannot be used as irrigation (it disperses the electrocautery current). Instead, slightly hypotonic nonelectrolyte solutions are used:
  • Glycine 1.5% (230 mOsm/L) — most common
  • Sorbitol 2.7% + mannitol 0.54% (195 mOsm/L)
  • Others: sorbitol 3.3%, mannitol 3%, dextrose 2.5–4%, urea 1%
Resection opens prostatic venous sinuses, allowing direct intravascular absorption. On average, 10–30 mL of fluid is absorbed per minute of resection time — procedures lasting 2 hours may result in 6–8 L of absorption. — Miller's Anesthesia, 10e
Factors governing absorption rate:
  1. Height of irrigating fluid above the surgical table (hydrostatic pressure)
  2. Degree of bladder distension
  3. Extent of open venous sinuses
  4. Duration of resection

Pathophysiology

TURP Syndrome Pathophysiology Flowchart
There are three main pathophysiologic axes:

1. Hypervolemia

Rapid intravascular volume expansion leads to:
  • Early hypertension + bradycardia (reflex)
  • Progression to ventricular failure → cardiovascular collapse
  • Pulmonary edema
  • Later, hypertension + hyponatremia causes a net outward osmotic/hydrostatic water shift → intravascular hypovolemia → hypotensive shock

2. Hyponatremia ± Hypoosmolality

The dilutional drop in serum sodium is the central problem. Severity of symptoms correlates with rate of fall, not just absolute level:
Serum Na⁺Clinical Features
< 120 mEq/LRestlessness, confusion, CNS symptoms, hypotension, pulmonary edema, CHF
< 115 mEq/LECG changes: wide QRS, ventricular ectopy, ST elevation
< 110 mEq/LSeizures, loss of consciousness
~100 mEq/LRespiratory and cardiac arrest
CNS signs are primarily driven by acute serum hypoosmolality (not hyponatremia per se), causing cerebral edema. — Miller's Anesthesia, 10e

3. Solute Toxicity (Glycine, Ammonia, Others)

  • Glycine is an inhibitory retinal neurotransmitter → transient blindness (sluggish/nonreactive pupils — distinguishing it from cerebral edema where pupillary reflexes are preserved)
  • Glycine also activates NMDA receptors → seizures
  • Glycine can cause T-wave changes and elevated CK-MB (without MI criteria) for up to 24 hours
  • Ammonia: glycine is hepatically deaminated to ammonia → encephalopathy; nausea/vomiting typically within 1 hour post-op; coma at high levels (10–12 hours duration)
  • Sorbitol → hyperglycemia
  • Mannitol → additional intravascular volume expansion

Incidence & Mortality

  • Incidence of mild-to-moderate TURP syndrome: 0.78–1.4%
  • Incidence across all TURP procedures: up to 10–15% (including subclinical)
  • Mortality with severe TURP syndrome (Na⁺ < 120 mEq/L): up to 25%
Risk factors: large prostate gland, resection > 90 minutes, large volumes of irrigation fluid, extensive venous sinus opening. — Miller's Anesthesia, 10e; Morgan & Mikhail, 7e

Clinical Presentation

Onset can be intraoperative or up to several hours postoperatively. Symptoms include:
  • Headache, restlessness, confusion
  • Nausea, vomiting
  • Cyanosis, dyspnea
  • Hypertension (early) → hypotension (late)
  • Arrhythmias
  • Visual disturbances / transient blindness
  • Seizures
  • Pulmonary edema

Diagnosis

High clinical suspicion is key. Workup when TURP syndrome is suspected:
  • Serum electrolytes (confirm hyponatremia)
  • Serum osmolality
  • Arterial blood gas
  • Blood glucose
  • 12-lead ECG
  • Consider serum ammonia if encephalopathy present

Treatment

Mild (Na⁺ > 120 mEq/L, minimal symptoms)

  • Fluid restriction
  • Loop diuretic (furosemide) — to eliminate absorbed free water
  • Supplemental oxygen, cardiovascular support

Severe (Na⁺ < 120 mEq/L, significant CNS/cardiovascular compromise)

  • IV hypertonic saline (3% NaCl) — correct cautiously to avoid central pontine myelinolysis
  • Rate of correction: generally no faster than 8–12 mEq/L per 24 hours
  • Stop the procedure as rapidly as possible

Novel Prevention

  • Tolvaptan 15 mg orally 2 hours preoperatively (selective vasopressin V2 receptor antagonist → free water excretion) has been proposed, especially for long or combined cystoscopic procedures. — Miller's Anesthesia, 10e

Prevention

  1. Use bipolar TURP with isotonic saline irrigant (eliminates hyponatremia risk)
  2. Limit resection time (< 90 minutes preferred)
  3. Limit irrigation fluid bag height
  4. Monitor fluid balance (input vs. output)
  5. Use spinal (neuraxial) anesthesia — allows real-time monitoring of mental status changes; also associated with lower 30-day mortality than general anesthesia
  6. Use ethanol-tagged irrigation fluid and exhaled breath ethanol monitoring (to detect absorption)

Analogous Syndromes

TURP syndrome has also been reported with:
  • Transurethral resection of bladder tumors
  • Ureteroscopy
  • Hysteroscopy (transcervical resection of endometrium)
  • Arthroscopy
All share the same mechanism: absorption of large volumes of hypotonic irrigant through open vascular sinuses.
Sources: Morgan & Mikhail's Clinical Anesthesiology, 7e, pp. 1302–1305 | Miller's Anesthesia, 10e, pp. 8471–8478 & 6372–6374
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