Sodium and potassium are essential for human health. They are important ions in the body and are associated with many physiologic and pathophysiologic processes. The chapter summarizes the basic physiologic actions of sodium and potassium on membranes of the neurologic and muscular systems. It provides information regarding the kinetics, i.e., absorption, distribution, and excretion of these ions and their movement between the intracellular and extracellular compartments. It also explains the physiologic systems that can influence proper homeostasis between sodium and potassium. Concentrations of sodium in the blood that exceed or do not reach the normal value range are called hypernatremia or hyponatremia, respectively. Similarly, the clinicians recognize hyperkalemia and hypokalemia. Pathologies associated with these states are described and examples of some of the diseases are presented here.

Detrusor hyperreflexia causing voiding dysfunction in spinal cord injury patients is a difficult problem and is not always treated effectively by anticholinergic agents. We have been investigating electrical stimulation methods to inhibit hyperreflexia and dorsal penile nerve stimulation is the most promising. Six chronic suprasacral spinal cord injury men (average age 36 years) underwent stimulation testing with water cystometry before, during and after stimulation. Dorsal penile stimulation was done with carbon rubber butterfly electrodes (Medtronic) with parameters of 5 pulses per second, 0.35 msec. pulse duration, and current at a level above the threshold for pelvic twitching activity and adjusted for optimal bladder effect (range 25 to 70 mamp.). In all 6 patients the cystometrogram during stimulation showed an increase in bladder volume over the prestimulation cystometrogram (range 27 to 150%). In 2 patients there was no detrusor activity after filling to 500 cc. Stimulation was then stopped and a spontaneous contraction occurred. The cystometrogram conducted after the stimulus also had less volume than that performed during stimulation but it was larger than the prestimulation volume. Penile nerve stimulation was painless with no side effects. Penile nerve electrical stimulation is effective for inhibiting bladder hyperreflexia and should be easily adaptable for chronic home use as an alternative to current therapy.

A total of 8 cases of bladder cancer in spinal cord injury men (4 quadriplegics and 4 paraplegics) was seen at 3 medical centers since 1985. All 8 men had a hyperreflexic bladder and 3 of them had associated detrusor-sphincter dyssynergia. Upper tract changes were noted in 4 patients: 2 with distal ureterectasis and 2 with mild hydronephrosis. Only 1 of these men did not have historical films with which to compare results. Histology was transitional cell carcinoma in 6 men and squamous cell carcinoma in 2. Four patients presented with muscle invasion and 1 presented with diffuse carcinoma in situ involving the penile urethra. Three patients presented with superficial transitional cell carcinoma and 2 of them had progression to muscle invasion within 6 and 11 months. All but 2 of the patients with invasive disease underwent a radical operation and urinary diversion. Although followup is short (range 6 to 17 months), 5 patients are well with no evidence of disease and of the 3 who died 2 had no evidence of disease. We found a lower incidence of bladder cancer and a decreased percentage of squamous cell carcinoma than in previous reports, which may reflect an improvement in the lower tract management of these patients. Survival with appropriate bladder cancer treatment appears to correlate well with that of the ambulatory population.