Case Summary

A 77-year-old male with a history of coronary artery disease (CAD) presented for transurethral resection of the prostate (TURP) for a markedly enlarged prostate gland measuring 128 cc. The surgical duration was 45 minutes. Pre-induction serum sodium was 142 mmol/L.

Rationale for General Anesthesia

General anesthesia was chosen to maintain hemodynamic stability in a patient with CAD, allow better control of ventilation and oxygenation, and avoid the risk of sympathetic blockade-induced hypotension associated with spinal anesthesia. In addition, airway protection was prioritized in case of fluid overload or neurologic complications.

At the molecular level, propofol acts on GABA-A receptors by enhancing chloride conductance, leading to neuronal inhibition and rapid-onset hypnosis. Fentanyl, a mu-opioid receptor agonist, attenuates sympathetic responses and provides analgesia.

References

Hahn RG. Acta Anaesthesiol Scand. 2006;50(10):1178–87.

Goyal R, Singh S, Shukla RN, Srivastava D. Comparative evaluation of general anesthesia and spinal anesthesia in high-risk geriatric patients undergoing TURP. J Anaesthesiol Clin Pharmacol. 2012;28(1):71–75.

Zisapel N. New perspectives on the role of melatonin in human sleep, circadian rhythms and their regulation. Br J Pharmacol. 2018;175(16):3190–3199.

Medications Administered

The patient received glycopyrrolate 0.2 mg IV, an anticholinergic muscarinic antagonist used to reduce vagal tone and secretions without crossing the blood-brain barrier. Midazolam 1 mg IV, a benzodiazepine that enhances GABA-A activity, was administered for anxiolysis. Fentanyl 100 mcg IV, a mu-opioid receptor agonist, was given to blunt pain and hemodynamic responses. Dexamethasone 8 mg IV, a glucocorticoid, provided anti-inflammatory and antiemetic benefits through suppression of prostaglandins and cytokines. Induction was performed with propofol 150 mg IV, which potentiates GABA-A receptor-mediated chloride influx, causing hypnosis and reducing myocardial oxygen demand. Atracurium 40 mg IV was administered as a non-depolarizing neuromuscular blocker, with maintenance at 10 mg/hr; this drug undergoes Hofmann degradation and is suitable for elderly patients with variable organ function.

Reference

Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail's Clinical Anesthesiology. 6th ed. New York: McGraw-Hill; 2018.

Airway Management

Airway control was achieved with an 8.0 mm endotracheal tube. The laryngoscopic view was Cormack-Lehane grade 2. General anesthesia with endotracheal intubation ensured airway protection, controlled ventilation, and preparedness for potential complications such as seizure or pulmonary edema.

Reference

Aziz MF, et al. A comparative study of the C-MAC video laryngoscope and direct laryngoscope for tracheal intubation in patients with difficult airways. Anesthesiology. 2012;116(3):629–36.

Intraoperative Fluids and Irrigation

Bipolar saline irrigation was used, which is isotonic and reduces the risk of TURP syndrome compared to glycine-based irrigants. Hypertonic saline (3%) was started at induction at 8 ml/hr and continued postoperatively as a preventive measure against dilutional hyponatremia. Normal saline 500 mL IV was given intraoperatively. One unit of packed red blood cells was transfused preoperatively. Furosemide 10 mg IV was administered after 45 minutes of resection to promote diuresis.

Pathophysiological Basis

During TURP, venous sinuses are opened, allowing irrigation fluid to enter systemic circulation, a process termed the "open vein" phenomenon. This fluid absorption can cause dilutional hyponatremia when large volumes of hypotonic fluid are absorbed, leading to hypo-osmolality. The resulting osmotic gradient drives water into neurons through aquaporin channels, predisposing to cerebral edema, increased intracranial pressure, and seizure activity.

Furosemide Pharmacology

Furosemide inhibits the Na⁺-K⁺-2Cl⁻ symporter in the thick ascending loop of Henle, promoting natriuresis and diuresis. It was used to enhance excretion of absorbed irrigation fluid, reduce volume overload, and assist in sodium correction.

Reference

Rassweiler J, Teber D, Kuntz R, Hofmann R. Complications of transurethral resection of the prostate (TURP)—incidence, management, and prevention. Eur Urol. 2006;50(5):969–980.

Sodium Shifts and Neurological Complications

The patient’s sodium levels and clinical status were closely followed. Pre-induction sodium was 142 mmol/L. At four hours postoperatively, sodium fell to 135 mmol/L, with no clinical symptoms. At eight hours postoperatively, sodium was not measured, but the patient developed a generalized tonic-clonic seizure. At 18 hours postoperatively, sodium was measured at 137 mmol/L, with the patient in postictal recovery.

Biochemically, hyponatremia reduces plasma osmolality, leading to water movement into brain cells via aquaporin-4 channels. Neuronal swelling and cortical irritability predispose to seizure activity.

Reference

Sterns RH. Disorders of plasma sodium—causes, consequences, and correction. N Engl J Med. 2015;372(1):55–65.

Seizure Management and Recovery

The seizure was treated with midazolam 2 mg IV, which enhanced GABA-A receptor activity and terminated the event. Levetiracetam 1 g IV was subsequently given for seizure prophylaxis via synaptic vesicle protein SV2A modulation. The patient entered a postictal state characterized by confusion and lethargy, followed by gradual recovery.

Reference

Abou-Khalil B. Levetiracetam in the treatment of epilepsy. Neuropsychiatr Dis Treat. 2008;4(3):507–23.

Pharmacological Strategies

Preventive and therapeutic pharmacologic strategies in this case included the use of hypertonic saline as osmotherapy to mitigate hyponatremia, furosemide to enhance urinary free water excretion, and midazolam with levetiracetam to abort and prevent seizures.

Clinical Lessons

This case highlights several important lessons. Despite the use of bipolar resection and prophylactic hypertonic saline infusion, elderly patients with large prostates remain at risk of delayed-onset TURP syndrome. Furosemide promotes diuresis but is insufficient to fully prevent dilutional hyponatremia. Continuous postoperative electrolyte monitoring for at least 24 hours is essential. Sudden drops in serum sodium greater than 10 mmol/L over a few hours can precipitate seizures, particularly in elderly patients with reduced cerebral reserve.

Reference

Verbalis JG, Goldsmith SR, Greenberg A, Korzelius C, Schrier RW, Sterns RH, Thompson CJ. Diagnosis, evaluation, and treatment of hyponatremia: expert panel recommendations. Am J Med. 2007;120(11 Suppl 1):S1–S21.

Conclusion

This case demonstrates the integration of molecular pharmacology, pathophysiological mechanisms, and anesthetic strategies in the management of a high-risk geriatric patient undergoing TURP. Despite careful preventive measures, a delayed-onset seizure due to dilutional hyponatremia occurred. The case underscores the importance of extended postoperative vigilance, judicious fluid management, and continuous electrolyte monitoring in elderly patients with large prostatic resections.