Detection of Hyponatremia in the PACUJeffrey Eaton, MS, MA, PhD(c), RN, ARNP

Fluid and electrolyte management is an important part of PACUnursing care. Any alteration in fluid and electrolytes, especially in thevulnerable elderly population, can be catastrophic. An assessment ofhyponatremia following transurethral resection of the prostate re-quires that the PACU nurse be diligent in discovering the etiology ofunexpected mental status changes.

© 2003 by American Society of PeriAnesthesia Nurses.

Objectives—Based on the content of this article, the reader should be able to (1) describe theetiology of hyponatremia following transurethral resection of the prostate (TURP); (2) discuss thechanges in the intracellular and extracellular fluid compartments causing dilutional hyponatremia; (3)identify 5 signs and symptoms that can be identified during the postanesthesia period that occur asa result of dilutional hyponatremia; and (4) differentiate the treatment of stable, symptomatic, andchronic hyponatremia.

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AN 80-YEAR-OLD MALE is admitted to thePACU following a transurethral resection of theprostate (TURP) for benign prostatic hyperpla-sia (BPH). Anesthesia consisted of a tetracainespinal and 2 mg of midazolam for sedation.Surgery was prolonged and complicated by adifficult resection of the 30-g prostate gland. Onadmission, the PACU nurse notes the patientresponds to verbal stimuli but is sleepy. Spinallevel using sensory stimuli is at T 7. Vital signsare all within the preoperative range. Oxygensaturation on a 2 L/M nasal cannula is 100%. Theanesthesia provider notes that 1,200 mL of in-travenous fluid were infused during the surgerywith 250 mL of estimated blood loss; lactatedRinger’s is infusing at 75 mL/hr. A 3-way Foleycatheter is in place with a continuous normalsaline irrigation. Drainage is light pink with noclots.

Jeffrey Eaton, MS, MA, PhD(c), RN, ARNP, is a ClinicalAssociate Professor at the University of New Hampshire,Durham, NH.

Address correspondence to Jeffrey Eaton, MS, MA, PhD(c),RN, ARNP, 253 Hewitt Hall, University of New Hampshire,Durham, NH 03824; e-mail address: jeff.eaton@unh.edu.

© 2003 by American Society of PeriAnesthesia Nurses.1089-9472/03/1806-0004$35.00/0

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orty-five minutes after PACU arrival, the pa-ient is more alert, but he responds to voice andouch with agitation. He tries to pull himself offhe stretcher but is unable to move his lowerody. He curses loudly and is not easily calmed.e continually throws off the nasal cannula andlaims that his “glasses” aren’t working veryell. By checking the preoperative nurse’s da-

abase, the PACU nurse knows that the patientoes not wear glasses. Vital signs are BP 110/62;ulse 72; temperature 37.2°C; respiratory rate6 with oxygen saturation on room air of 94%.he PACU nurse assesses diminished lungounds bilaterally but does not auscultate crack-es. The patient remains irritated and somewhatombative over the next 15 minutes. After no-ifying the anesthesia provider of the patient’shange in behavior, the PACU nurse consultshe urologist. Laboratory work, including a statemoglobin, hematocrit, and electrolyte panel,

s ordered. The patient remains confused andombative.

he laboratory calls to alert the nurse that theatient’s serum sodium is 125 mmol/L, with allhe other values normal and consistent withreoperative levels. The PACU nurse notifies

doi:10.1016/j.jopan.2003.08.004

he urologist who changes the postoperative IV

al of PeriAnesthesia Nursing, Vol 18, No 6 (December), 2003: pp 392-397

fluid to normal saline, admits the patient to thetelemetry unit overnight, and orders an electro-lyte panel for the morning. The admitting diag-nosis is hyponatremia.

TUR Syndrome

Hyponatremia, an abnormally low concentra-tion of sodium in the blood, occurs in approx-imately one in every 50 men having a transure-thral resection of the prostate (TURP).1 Theetiology of hyponatremia is the dilutional effectof the solution used for intraoperative irrigationduring the prostate resection. When hyponatre-mia can be traced to the use of urological irri-gation, the associated signs and symptoms arereferred to as TUR syndrome.

Physiology of Hyponatremia

Fluid contents and cell structures provide anormal cell size and shape. If the amount ofcellular fluid increases, the cell swells and cellfunction can be impaired. Similarly, if the cellloses fluid, the cell shrinks, a condition that alsointerferes with normal cell processes. Extracel-lular fluid (ECF) and intracellular fluid (ICF) areisotonic, meaning that they have the correctamount of solutes or particles to maintain cel-lular fluid balance.

The ECF is normally high in sodium (150mmol/L of water) and relatively low in potas-sium (5.5 mmol/L). The ICF is almost the oppo-site, with 15.0 mmol/L of sodium and 150mmol/L of potassium.2 These inverse concen-trations, necessary for normal cell function, arefacilitated by a hypothesized sodium-potassiumpump.

Hyponatremia can occur in two ways. First,when the body has too much fluid relative to anormal amount of sodium, the condition iscalled a dilutional hyponatremia. The secondway is when there is too little body sodiumrelative to a normal amount of fluid, a conditionreferred to as sodium deficit hyponatremia. Inthe first case, the patient will have signs of fluidoverload, but in the second case, the patient

may actually have signs of dehydration. TURsyndrome is an example of dilutional hypona-tremia.

In dilutional hyponatremia, the ECF becomesdramatically different from the ICF in its com-position. The ECF has lost sodium. Osmotic andcellular processes attempt to maintain a similaroverall concentration inside the cells. If sodiumin the ECF is proportionately low, then cells willtry to draw water into the cell in an effort todilute the ICF. This response makes the ICF lessconcentrated and, therefore, will more closelyresemble the concentration of the ECF. Thiscompensatory mechanism will cause cells toswell. Brain cells are particularly sensitive to thedilution of the ICF. Other cells, such as skeletalmuscle cells and smooth muscle cells in the gut,will also be affected.

TUR-Induced Hyponatremia

It seems logical to use an isotonic solution forirrigation during a TUR so that electrolytes andwater would not need to shift between the ICFand ECF. Unfortunately, normal saline cannotbe used for intraoperative irrigation because ofits electroconductive properties.3 Saline irriga-tion is contraindicated with electrocautery, amethod used for coagulation during the TUR.For irrigation during this surgery, a glycine,mannitol, or sorbitol solution is used.

Glycine is an amino acid–based solution and ishypotonic.4 During the surgical irrigation, gly-cine can be absorbed through the open vascularbed of the prostate. During a typical TURPsurgery lasting 40 minutes, 1 to 2 liters can beabsorbed. However, if the surgery is prolongedor large venous channels are opened during theprocedure, the absorption may be significantlygreater.1 Excessive absorption of the irrigatingsolution causes a shift of fluid into the cells withthe ICF attempting to create a concentration-similar to the ECF. The result is cellular edemaand impaired cellular functions.

DETECTION OF HYPONATREMIA IN THE PACU 393

Other Sources of Hyponatremia

Hyponatremia is a common finding in manyother diseases (Table 1) and an untoward sideeffect of several drug therapies (Table 2). Manyof these diseases create a tendency of the bodyto retain water that results in dilutional hypona-tremia. Other diseases can create a sodium def-icit. One common syndrome that creates a hy-ponatremia is the syndrome of inappropriateantidiuretic hormone (SIADH).

SIADH is characterized by an excess of antidi-uretic hormone (ADH). ADH acts to stimulatewater reabsorption in the collecting ducts ofthe kidney, a homeostatic process that seeks tomaintain normal fluid balance. SIADH usuallyoccurs for 1 of 2 reasons. In some cases, theposterior pituitary, the normal site of ADH pro-duction, receives incorrect information fromthe body’s normal feedback mechanisms. Tu-mors, hormones, or inadequate cellular func-tion seem to interfere with the normal feedbackmechanisms, creating an increased productionof ADH. In other cases, tumors will actuallyproduce the ADH substance themselves. Oneexample of this ectopic production of ADH issmall cell carcinoma of the lung, which has avery high incidence of SIADH. A patient with an

acute form of SIADH may present similarly to apatient with TUR syndrome.

The stress of surgery, especially when generalanesthesia is used, can trigger the release ofADH by the posterior pituitary,5 creating anacute form of SIADH. The ADH release results inwater retention. It is estimated that between 1%and 5% of all patients experience hyponatremiain the postoperative period. This form of SIADHis more common among women than men, andwomen are more likely to develop complica-tions such as coma and seizures.6 During thepostoperative period, premenopausal womenare at particular risk.7 Acute SIADH also occursin men. Although assessment and treatmentissues may not differ significantly from the pa-tient with TUR syndrome, acute SIADH must beconsidered.

SIADH can exist in a chronic form. In thesepatients, hyponatremia has a more insidiousonset than in patients with TUR syndrome.Patients with chronic SIADH will often useother mechanisms to adjust their ICF/ECF fluidbalance and fluid volume. Even though thesepatients are hyponatremic, they may be eu-volemic or have a normal body fluid volume. Itis even a greater challenge when a patient whohas a preexisting chronic SIADH develops post-operative hyponatremia. The importance ofcomparing postoperative sodium levels to thosedrawn preoperatively cannot be overempha-sized.

Table 2. Medications That Can CauseHyponatremia

DiureticsNSAIDsChlorpropamideNicotineCyclophosphamideHaloperidolThioridazineCarbamazepineTricyclic antidepressantsPhenothiazines

Table 1. Diseases/Conditions That Can CauseHyponatremia

Renal diseaseCongestive heart failureCirrhosisHypothyroidismAdrenal insufficiencyPneumoniaTuberculosisLung cancerMeningitisBrain tumorsHead traumaMarkedly elevated glucoseHyperlipidemia (pseudohyponatremia)Psychogenic polydipsia (excessive water intake)Excessive use of tap water enemasHypotonic irrigating solutions

JEFFREY EATON394

Assessment of TUR SyndromePhysical Assessment

The signs and symptoms of hyponatremia aredifficult to discriminate from commonly foundcomplications following anesthesia (Table 3).However, signs and symptoms of fluid overloadin the TUR patient should alert the PACU nurseto nonanesthetic complications. On physicalassessment, the patient exhibits signs of exces-sive hydration, including an increased respira-tory rate, lung crackles on auscultation, andperipheral edema. Anorexia, nausea, and vom-iting are common signs of hyponatremia due tothe impaired cellular functions of the gastroin-testinal system. Diarrhea may also be present.

The neuromuscular system depends on sodiumions for action potential depolarization andmuscle contraction. Hyponatremia results in al-tered neuromuscular function manifested bymuscle cramps, weakness, lethargy, and generalmalaise. Visual disturbances may also occur andare related to the edema of the ocular lenscreated by ICF fluid shifts.

Patients undergoing TURP surgery often havecomorbidities, with up to 24.9% having knowncardiac disease.1 The cardiac effects of hypona-tremia are related to the patient’s overall fluidvolume status. Patients who are overhydrated

can exhibit tachycardia and high blood pres-sure. For the patient with preoperative, chronicatrial fibrillation, these findings can create theneed for postoperative cardiac monitoring.

Mental Status Assessment

During the immediate postoperative period, pa-tients may be under the influence of medica-tions that alter cognitive processes. Any ten-dency toward disordered thought prior tosurgery can make the postoperative mental sta-tus assessment that much more challenging. It isimportant that the PACU nurse recognize thatpostoperative confusion is not acceptable in anelderly patient without strong evidence or aprevious report of dementia. Even in patientswith a history of dementia, hyponatremia canexacerbate their confusion. When brain cellsrespond to hyponatremia, they swell. Cerebralswelling is manifested as confusion or a person-ality change.

Laboratory Assessment

Although hyponatremia is defined as serum so-dium lower than 135 mmol/L, the absolute levelof serum sodium is less important than howrapid the level changed.8 When the sodiumlevel has been declining slowly over a longperiod of time, the body adjusts by process,producing amino acids to maintain adequatecellular concentrations.3

When serum sodium is measured, the analysisof serum osmolality is important. Serum osmo-lality provides information on the dilution of theserum. A decrease in serum osmolality will oc-cur in cases of true hyponatremia. A urine spotsodium may also be ordered to measure thesodium in the urine. If sodium levels in theurine are elevated, the kidneys are acting toalter serum sodium blood levels. High urinesodium is found in SIADH. Unfortunately, forthe postoperative TUR patient with signs andsymptoms of hyponatremia, urine sodium levelsmay not be diagnostic because of the continu-ous bladder irrigation therapy.

Table 3. Signs and Symptoms ofHyponatremia

HeadacheAnorexiaNauseaVomitingDiarrheaTachycardiaGeneral malaiseMuscle crampsWeaknessLethargyPersonality changesDisorientationSeizuresDeath

DETECTION OF HYPONATREMIA IN THE PACU 395

Treatment of Hyponatremia

Although the treatment of hyponatremia de-pends on the etiology of the sodium loss, theobjective is the same: restoration of the extra-cellular and intracellular fluid balance. In thestable patient, the fluid balance restoration canoccur slowly.

The goal for hyponatremia therapy in the stablepatient is to gradually decrease body water andincrease serum sodium levels. The patient isplaced on fluid restrictions and normal saline isinfused intravenously. A slow and gentle returnto homeostatic levels allows the body to gradu-ally compensate.

Symptomatic but stable patients may also re-quire diuretics to aggressively decrease totalbody water. Furosemide is frequently used be-cause it causes greater excretion of body waterthan excretion of sodium. Intravenous salinewill also ordered.

When the patient is unstable due to suddenonset hyponatremia as evidenced by seizures, acoma, or serum sodium below 120 mmol/L,then more aggressive therapy is indicated. Forthese patients, treatment may include an intra-venous infusion of hypertonic sodium solution(3% saline). Patients diagnosed with TUR syn-drome may require hypertonic saline especiallyif the patient had a normal sodium level prior tosurgery.

Because chronic diseases, medical condi-tions, and medications can cause hyponatre-mia, treatment of the hyponatremia may notbe appropriate in all cases. Returning theserum sodium to normal levels in patientswho have a history of chronic hyponatre-mia can be dangerous. When an individualslowly develops hyponatremia over a longperiod of time, the body develops compen-satory mechanisms. Over time amino acidsare used to maintain the intracellular os-motic pressure, a process that cannot bereversed quickly. Giving hypertonic solu-

tions of sodium in these instances can actu-ally create an osmotic pressure that drawsfluid out of the cells, causing them toshrink. Certain brain cells, especially thosein the pons, are particularly sensitive toosmotic shifts, and permanent brain dam-age can occur.

A new surgical approach to prostatatic hy-perplasia is transurethral bipolar electrova-porization. Bipolar transurethral vaporiza-tion uses normal saline for an irrigationfluid, therefore eliminating the risk of dilu-tional hyponatremia. In a recent random-ized controlled study with 1-year follow-up,patient outcomes, including fluid absorp-tion, were similar.9

Nursing Implications

Nursing care of patients with TUR syn-drome requires knowledge of the patho-physiological process created by hyponatre-mia and the management of problemscaused by hyponatremia. Assessment of thepostoperative TUR patient requires that thenurse be aware of risk factors for the devel-opment of TUR syndrome and be vigilant inlooking for signs of hyponatremia.

The PACU nurse should be aware of theduration and extent of the TUR procedure.During report, the perioperative nurseshould be questioned as to any excessiverequirement for intraoperative irrigation.When the patient arrives in the PACU, thesurgical bladder irrigation solution shouldbe replaced with a normal saline-irrigatingsolution as soon as possible. Lung soundsshould be frequently assessed in high-riskpatients. Postoperative confusion due toamnesiacs and narcotics must be carefullydifferentiated from the confusion resultingfrom hyponatremia.

If a diagnosis of hyponatremia is made andtreatment is required, the nursing priority is toprovide a safe environment for the confused

JEFFREY EATON396

patient. If hypertonic saline is ordered, thenurse must be vigilant for signs of intracellularto extracellular fluid shifts. Pulmonary edemaand heart failure can occur quickly as fluidmoves back to the extracellular space. Infusingthe hypertonic saline using appropriate equip-ment and rates can decrease the probability ofcomplications.

ConclusionTUR syndrome, although a relatively uncom-mon occurrence, can be effectively managed byearly detection and intervention. Because manyTUR patients have preexisting diseases, hypona-tremia can be life-threatening. CompetentPACU nursing can reduce the risk of complica-tions and improve patient outcomes.

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9. Dunsmuir WD, McFarlane JP, Tan A, et al: Gyrus bipolarelectrovaporization versus transurethral resection of theprostate: A randomized prospective single-blind trial with 1year follow-up. Prostate Cancer Prostatic Disease 6:182-186,2003

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