can, however, exacerbate hypovolemia. Our patient was admitted 2 days preoperatively on oral potassium chloride 60 meq (SI: 60 mmol) daily. On this intake ...
CASE REPORT
Anesthetic Management of a Patient with Bartter's Syndrome Undergoing Orthognathic Surgery James A. Roelofse, MBChB, MMed, PhD, and Albert J. Van der Westhuijzen, BChD, MChD, FFD (SA) MFOS, FDSCRS (Eng.) Faculty of Dentistry, University of Stellenbosch, Private Bag Xl, Tygerberg 7505, South Africa
Bartter's syndrome is a rare disorder characterized by severe hypokalemic alkalosis, marked elevation in plasma renin activity, pressor insensitivity to angiotensin II, and normal or low values of plasma sodium, plasma chloride, and blood pressure. Many of the clinical features and biochemical abnormalities appear to be secondary to chronic hypokalemia. We managed a 22-yr-old man requiring orthognathic surgery for correction of facial asymmetry under general anesthesia. Key Words: Anesthetic management; Bartter's syndrome; Orthognathic surgery.
W e recently managed a patient with a rare disease, Bartter's syndrome,' who required a bilateral sagittal split osteotomy to correct facial asymmetry. The syndrome is characterized by hypokalemic hypochloremic alkalosis, hyperreninemia, hyperaldosteronism, and hyperplasia of the juxtaglomerular apparatus of the kidneys. The patients have normal blood pressure and show marked resistance to the pressor actions of angiotensin II and norepinephrine.2 Bartter's syndrome is often congenital, and sometimes familial. It can also result from chloride-deficient diets,3 from renal complications of chemotherapy,4 and rarely, from cystic fibrosis.5 We were unable to find a report in the literature dealing with the anesthetic management of patients with this syndrome, undergoing orthognathic surgery.
discrepancy. Preoperative (Figure 1) and postoperative photographs (Figures 2 and 3) are shown. The patient was a 22-yr-old, 60 kg male, admitted to the hospital 2 days preoperatively for a bilateral sagittal split mandibular osteotomy under general anesthesia. He had been diagnosed with Bartter's syndrome at the age of 5 yr. On admission, physical examination was normal, and blood pressure was 130/70 mm Hg. The electrocardiogram demonstrated only nonspecific ST-T changes. There were no arrhythmias or U waves. Pertinent laboratory data included serum potassium and chloride levels of 2.4 meq/L (SI: 2.4 mmol/L) and 94 meq/L (SI: 94 mmol/L), respectively, and a total CO2 of 32.7 meq/L (SI: 32.7 mmol/L). Blood urea nitrogen and serum creatinine levels were 7.8 mg/dl (SI: 2.8 mmol/L) and 0.89 meq/dL (SI: 79 mmol/L). The magnesium level was 1.6 meq/L (SI: 1.6 mmol/L). The patient's medications included indomethacin, 25 mg, and oral potassium chloride, 15 mmol, both taken four times a day, and spironolactone, 50 mg, taken three times daily. The oral potassium chloride was increased to 80 meq a day (SI: 80 mmol per day) preoperatively, and an intravenous infusion of potassium chloride was started with the patient receiving 40 meq (SI: 40 mmol) every 6 hr. Laboratory data 24 hr after starting the infusion of potassium chloride demonstrated serum potassium and chloride levels of 3.0 meq/L (SI: 3.0 mmol/L) and 94 meq/L (SI: 94 mmol/L), respectively, and a total CO2 of 37.5 meq/L (SI: 37.5 mmol/L). Blood urea and se-
CASE REPORT The patient had mandibular prognathism, dental malocclusion, and facial asymmetry and a strong desire to have this corrected. Orthodontic compensation in preparation for surgery had already been completed prior to the initial surgical consultation. Only after careful consideration and a frank discussion with the patient did we decide to proceed with surgery to correct his skeletal Received August 20, 1995; accepted for publication May 15, 1997. Address correspondence to Dr. James A. Roelofse, Faculty of Dentistry, University of Stellenbosch, Private Bag Xl, Tygerberg 7505, South Africa. Anesth Prog 44:71-75 1997 © 1997 by the American Dental Society of Anesthesiology
ISSN 0003-3006/97/$9.50 SSDI 0003-3006(97)
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Figure 1. Preoperative intraoral view.
rum creatine levels were 17.7 mg/dl (SI: 6.3 mmol/L) and 1.3 mg/dl (SI: 118 ,umol/L). The intravenous infusion of potassium chloride was administered until immediately before surgery the following morning. On the morning of surgery, the patient was premedicated 60 min preoperatively with diazepam, 10 mg orally, and papaveretum, 10 mg, intramuscularly. Before induction of anesthesia, percutaneous radial arterial and internal jugular venous pressure catheters were in-
Figure 2. Postoperative intraoral view.
serted. Arterial blood pressure before induction of anesthesia was 122/70 mm Hg and heart rate 90 beats/ min. Preinduction central venous pressure was 8 cm H20. Urinary output and neuromuscular function were monitored using a Foley catheter and a peripheral nerve stimulator. Other monitors used were an ECG, a pulse oximeter, and a capnograph, to ensure normoventilation. Etomidate 0.3 mg/kg, vecuronium 0.1 mg/kg, and
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138/38 to 100/62 mm Hg; heart rate from 60 to 95 beats/min. Vasopressors to maintain the blood pressure were not required. The central venous pressure was kept between 4 and 10 cm H20; if necessary, lactated Ringer's solution was infused during anesthesia, which lasted 4 hr. Serum electrolyte and blood gas levels pre-, peri-, and postoperatively are shown in Table 1. With induction of anesthesia, the serum potassium level was 3.1 meq/L (SI: 3.1 mmol/L). Over the next 2 hr, it decreased to 2.6 meq/L (SI: 2.6 mmol/L). A total of 40 meq/L (SI: 40 mmol) of potassium chloride was given over 4 hr, the serum potassium level being 3.4 meq/L (SI: 3.4 mmol/L) at the end of the operation.
~~~~~~~~.
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w*s,t_1 r.
.... ...
Figure 3. Postoperative frontal view.
alfentanil 0.1 mg were given for induction of anesthesia, and the trachea was intubated. Blood pressure increased transiently to 140/88 mm Hg after intubation. During the operation, the patient received 50% nitrous oxide in oxygen, a further 0.2 mg of alfentanil, and isoflurane 1 to 2%. Ventilation was controlled mechanically. Preoperative blood gas analysis after induction of anesthesia with an inspired oxygen concentration of 0.5 showed a pH of 7.50; PaO2 of 306.8 mm Hg (SI: 40.9 kPa); PaCO2 of 34.5 mm Hg (SI: 4.6 kPa); and bicarbonate of 27.4 meq/L (SI: 27.4 mmol/L) with no base excess. The blood pressure during surgery ranged from
During surgery, the patient had a brisk continuous diuresis averaging 387 ml/hr; it was 281 ml/hr after surgery for 18 hr. The patient was kept in the intensive care unit the following day, and the remainder of his postoperative course was uneventful. The patient was discharged 3 days postoperatively on the same treatment he had received preoperatively. A serum potassium level done 3 wk after the operation was 3.7 meq/L (SI: 3.7 mmol/ L). About 8 wk postoperatively, the patient developed a gastric ulcer, which responded well to antacids. At that time, an endocrinologist reviewed his maintenance therapy and recommended that the indomethacin be stopped. The patient was to continue with the potassium chloride and spironolactone as before. DISCUSSION The pathophysiology of Bartter's syndrome and its treatment present the anesthetist with numerous deci-
Table 1. Electrolytes-Blood Gas Analysis Parameters (SI Units) Normal Ranges in Parenthesis Sodium (136-144 mmol/A) Potassium (3.5-5.5 mmol/A) Chloride (97-107 mmol/A) Magnesium (0.75-1.25 mmol/l) Creatinine: (60-120 tLmol/l) BUN (2.9-8.9 mmol/A) pH (7.36-7.44) PaO2 (83-112) mm Hg (11-15) kPa PaCO2 (33-45) mm Hg (4.5-6.1) kPa
On PreAdmission operative 138 2.4 3.1 94 107 0.66 79 2.8 7.50
Bicarbonate (22-26 mmol/A) 40% oxygen. Room air. Note: Normal values are given in parenthesis.
a b
307 40.9 34.5 4.7 27.4
Perioperative
Postoperative
1000 hr 140 2.6 100
1130 hr 138 3.4 101
1800 hra 142 2.4 101
2400 hra 136 3.4 106
0800 hrb 136 3.4 103
7.50 281 37.4 33.8 4.6 26.5
7.44 291 38.8 37.4 5.1 25.8
7.38 165 22 40.4 5.5 26.9
7.37 165 22 38.9 5.3 26.7
7.44 106 14.1 41 5.6 27.9
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sions regarding the anesthetic technique. Anesthetic management may be complicated by preoperative medication, electrolyte disturbances, renal dysfunction, the presence of hypovolemia, and the danger of hypotension. Very few cases of the anesthetic management of this syndrome are reported in the literature. Higa6 et al reported the anesthetic technique in a 44-yr-old Japanese man with Bartter's syndrome complicated by renal dysfunction. General anesthesia was maintained with 50% nitrous oxide in oxygen, 0.5 to 0.8% isoflurane, supplemented with intravenous midazolam and butorphanol. There were no profound peri- or postoperative hemodynamic derangements. The treatment for Bartter's syndrome is usually directed toward the manifestations of the disease. All efforts are aimed at normalizing the serum potassium level. Various preparations are available. Oral potassium supplementation is not always effective, because most patients react by a proportionate increase in renal potassium excretion. Potassium is preferably administered in a slow-release form, which minimizes irritation and ulceration of the esophagus, stomach, and small bowel. Very high doses of potassium chloride used alone are usually well tolerated, and patients may routinely take eight to 15 of these tablets three times daily with meals, giving a total of 192 to 360 meq (SI: 192-360 mmol) supplemental potassium daily. Potassium-sparing diuretics, eg, spironolactone, can also be administered, as they raise the potassium and magnesium levels. They can, however, exacerbate hypovolemia. Our patient was admitted 2 days preoperatively on oral potassium chloride 60 meq (SI: 60 mmol) daily. On this intake, he had a serum potassium level of 2.4 meq/L (SI: 2.4 mmol/L). The next day, his daily intake of potassium chloride was increased to 80 meq (SI: 80 mmol). Additionally, an intravenous infusion of potassium chloride of 240 meq (SI: 240 mmol) given over 24 hr was started. After receiving a total of 320 meq (SI: 320 mmol) of potassium chloride over 24 hr, his serum potassium level was 3.0 meq/L (SI: 3.0 mmol/ L). Since sodium wasting is a constant feature of Bartter's syndrome, oral supplements should be helpful, as hypovolemia is probably invariable and symptomatic hypotension can be a problem. Angiotensin-converting enzyme inhibitors (ACE) have been given to inhibit angiotensin II production.7 Treatment with captopril has also been associated with a substantial increase in plasma potassium and a relief of hypokalemia-related symptoms. Administration of the ACE inhibitor enalapril in the rather low dose of 10 mg daily to patients with Bartter's syndrome has led to almost normal serum potassium levels.8 It is not considered necessary to withdraw ACE inhibitors before sur-
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gery, but significant perioperative hypotension has been reported in patients taking them. Meticulous monitoring by using a central venous catheter is essential, particularly if there is significant hypovolemia. Two major pathophysiological and biochemical abnormalities are to be found in patients with Bartter's syndrome-sodium chloride wasting with hypovolemia and hypokalemic alkalosis. Patients treated with spironolactone, a potassium-sparing diuretic, and popranolol may also be hypovolemic. However, because of myocardial beta-adrenergic blockade, there may be no chronotropic response in the hypovolemic patient. Patients with Bartter's syndrome may be on ACE inhibitors, and significant hypotension may follow when there is fluid loss during anesthesia.9 Because of the possibility of hypovolemia and the brisk diuresis peri- and postoperatively, the placement of a central venous pressure line becomes mandatory when managing these patients. Elective operations have been cancelled in the past in patients with hypokalemia. Alternatively, anesthetists have tried to correct serum potassium levels before anesthesia. It is still, however, being debated what the minimum safe recommended serum level of potassium before anesthesia should be. The general consensus of opinion used to be that the serum potassium should be at least 3.5 meq/L (SI: 3.5 mmol/L); however, there is sufficient evidence to suggest that 2.5 meq/L (SI: 2.5 mmol/L) may be acceptable.'0 Preoperative measurement and correction of hypokalemia is based on the widely held belief that hypokalemia predisposes to potentially life-threatening arrythmias" and/or prolonged paralysis after the use of nondepolarizing muscle relaxants.12 None of those complications were encountered during anesthesia in our patient. Since patients with Bartter's syndrome have low serum potassium, hyperventilation should be avoided, as hypocapnia increases blood pH and lowers serum potassium.'0 The effect of neuromuscular-blocking drugs during anesthesia should also be monitored with a nerve stimulator in patients with hypokalemia. The renal function of patients with Bartter's syndrome may affect the choice of the anesthetic technique. Elimination of volatile anesthetic agents is independent of renal function. There have been isolated reports of possible fluoride-induced nephrotoxicity with enflurane, which should probably be avoided. We used isoflorane and had no undesirable perioperative hypotension. Presumably, the markedly raised basal renin levels are the result of hypovolemia and a tendency to hypotension, causing baroreceptor-activated stimulation of the sympathetic nervous system.13 Nishikawa and Dohi investigated the baroreflex function in a 40-yr-old woman with Bartter's syndrome.14 They concluded that unstable
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baroreceptor responses exist in patients wAth this syndrome. The instability of reflex responses may be attributable to prostaglandins, hypovolemia, hypokalemia, and positive pressure ventilation. The use of an inhalational anesthetic agent and nitrous oxide may aggravate the instability. Careful attention must thus be paid to the ever-present possibility of hypotension in patients wAth Bartter's syndrome. Although anesthetic management may be difficult in Bartter's syndrome, our case shows that thorough preoperative planning, perioperative care, and meticulous postoperative management can lead to a complicationfree recovery after orthognatic surgery. REFERENCES 1. Abston PA, Prianno LL: Bartter's syndrome: anesthetic implications based on pathophysiology and treatment. Anesth Analg 1981;60:764-766. 2. Bartter FC, Pronove P, Gill JR, MacCardle RC: Hyperplasia of the juxtaglomerular complex with hyperaldosteronism and hypokalemic alkalosis. A new syndrome. Am J Med 1962;33:811-828. 3. Roy S, Arant BS: Alkalosis from chloride-deficient neomullsoy. New Engl J Med 1979;301:615.
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4. Lieber IH, Stoneburner SD, Floyd M, McGuffin NL: Potassium-wasting nephropathy secondary to chemotherapy simulating Bartter's syndrome. Cancer 1984;54:808-810. 5. Davison AG, Snodgrass GJAI: Cystic fibrosis mimicking Bartter's syndrome. Acta Pediatr Scand 1983;72:781-783. 6. Higa K, Istino H, Sato S, Dan K: Anesthetic management of a patient with Bartter's syndrome. J Clin Anesth 1993;5:321-324. 7. Jest P, Pederson KE, Klitgaard NA, et al: Angiotensinconverting enzyme inhibition as a therapeutic principle in Bartter's syndrome. Eur J Clin Pharmacol 1991;41:303-305. 8. Hene RJ, Koomans HA, Dorhout Mees EJ, et al: Correction of hypokalemia in Bartter's syndrome by enalapril. Am J Kidney Dis 1987;9:200-205. 9. Selbi DG, Richards JD, Marshman JM: ACE inhibitors. Anaesth Intensive Care 1989;17:110-111. 10. Vitez TS, Soper LE, Wong KC, Soper P: Chronic hypokalemia and intraoperative dysrhythmias. Anesthesiology 1985;63:130-133. 11. Katz RL, Bigger JT: Cardiac arrhythmias during anesthesia and operation. Anesthesiology 1970;33:193-213. 12. Vaughan RS: Potassium in the perioperative period. B J A 1991;67:194-200. 13. Gordon RD, Tunny TJ, Klemm SA: Indomethacin and atrial natriuretic peptide in Bartter's syndrome. New Eng J Med 1986;315:459. 14. Nishikawa T, Dohi S: Baro-reflex function in a patient with Bartter's syndrome. Can Anaesth Soc J 1985;32:646650.
