a 15-year - old adolescent ( weight , 46 kg ; height , 162 cm ) had a medical history of hypertension , cyclic headache , and vomiting for 10 years without an awareness of his medical condition .
thereafter , he demonstrated a seizure with subcortical ich in the left frontal area 6 weeks before the surgery .
he was diagnosed with pheochromocytoma as confirmed by excessive catecholamine production in his serum and urine .
the computed tomography scan revealed two masses ( dimension , 4.0  3.5 cm , and 1.6  1.2 cm ) in the left adrenal gland .
preoperative preparation consisted of terazosin 1 mg , losartan 1.25 mg , atenolol 25 mg , and levetiracetam 1 g daily for 2 weeks , which resulted in symptomatic improvement , normotension and prevention of seizure . before entering the operating room , 2 mg of midazolam
was infused and dexmedetomidine was given 1 g / kg over 10 min at the waiting area , followed by a continuous intravenous infusion at 0.5 g / kg / hr . on arrival to the operating room ,
the intraoperative monitoring consisted of electrocardiogram ( lead ii ) , hr , pulse oximeter , end - tidal co2 , bispectral index , esophageal temperature , invasive measurement of bp with cardiac index , central venous pressure , central venous oxygen saturation , and urine output .
arterial blood gases , electrolytes , glucose , and serum catecholamines were planned to check before induction and after intubation , tumor manipulation , and removal of tumors .
general anesthesia was induced with propofol 100 mg , continuous infusion of dexmedetomidine , remifentanil 0.2 g / kg / min and sevoflurane 2.0 vol% by mask .
anesthesia was maintained with a 2.5% end - tidal concentration of sevoflurane in an oxygen - air mixture ( fio2 = 0.50 ) and infusion of remifentanil 0.1 g / kg / min and dexmedetomidine
however , when the surgeon began to manipulate it , bp and hr were abruptly increased ( fig .
those changes were controlled with bolus injection of remifentanil , nicardipine , esmolol , and sodium nitroprusside .
remifentanil , nicardipine , and sodium nitroprusside were also used to put back his vitals to baseline .
after tumor removal , bp decreased rapidly , which responded to ephedrine and phenylephrine to produce an increase in systolic bp of 80 - 100 mmhg .
dexmedetomidine and remifentanil were stopped at closure of peritoneum and at end of skin closure , respectively .
after extubation , the patient was mildly sedated but had good respiration and possible purposeful movement .
the total operation time was 200 min , and the total period of anesthesia was 285 min . estimated blood loss was about 200 ml and the total dose of infused dexmedetomidine was 144 g .
after the surgery , he stayed at the intensive care unit for 1 day and was discharged 10 days after the surgery with no noticeable complications and events .
the anesthetic management for maintaining stable cardiovascular response during the resection of pheochromocytoma is still an unsolved assignment to the anesthetist . during the operation , catecholamine level increase of up to 200,000 - 1,000,000 pg / ml ( normal catecholamine levels under stressful events : 200 - 2,000 pg / ml ) ,
because our patient had an episode of seizure and ich only 6 weeks before the surgery , we had to concentrate on keeping his bp under our control to avoid neurologic complications .
dexmedetomidine is a highly selective alpha-2 adrenoceptor agonist compared with clonidine , especially for the 2a subtype .
they are located on blood vessels , where they mediate vasoconstriction , and on sympathetic terminals , where they inhibit noradrenaline release .
alpha-2 adrenoceptors are also located within the central nervous system , and their activation leads to sedation , a 60 - 80% reduction of tonic levels of sympathetic outflow and catecholamines , and an augmentation of cardiac - vagal activity .
dexmedetomidine attenuates sympathoadrenal responses to tracheal intubation and surgical stimuli and has a significant anesthetic and analgesic sparing effect when used intraoperatively .
additionally , dexmedetomidine has recently been investigated for its potential in many other clinical scenarios , including neuroprotection , cardioprotection and renoprotection , with promising results .
the pharmacokinetics of remifentanil is characterized by small volume of distribution , rapid clearance , and short context - sensitive half - time .
prompt onset and short duration of action make remifentanil a useful selection for the suppression of the transient sympathetic nervous system response to tracheal intubation and noxious stimuli in at risk patients . although remifentanil is effective for blunting the sympathetic response , there were reports that even if remifentanil was being infused in pheochromocytoma excision to control intraoperative hemodynamic instability , the use of vasodilators was required during tumor manipulations . although our anesthetic team assumed that the combination of dexmedetomidine and remifentanil might produce additional hypotensive agents to be unnecessary , we actually infused low dose of esmolol , sodium nitroprusside and nicardipine when bp surges came up during tumor manipulation .
because one of masses was placed difficult to dissect , the surgeon had a hard time manipulating the tumors before ligation of the adrenal vein .
there are some reports on serum plasma catecholamine levels during the resection of pheochromocytoma , which show wide variation depending on what stimuli had been done to the patient . in comparison , our patient 's levels of catecholamine ( table 1 ) represented persistent decreasing trend except with epinephrine , which means that infusion of dexmedetomidine and remifentanil might interrupt the release of norepinephrine effectively during the procedure .
russell et al . , in a retrospective analysis of a group of adult patients , found a significant correlation between intraoperative cardiovascular instability and peak serum catecholamine levels measured at the time .
.   also showed a significant correlation between plasma norepinephrine concentration and mean arterial pressure during surgery .
bryskin and weldon   reported that the infusion of dexmedetomidine and magnesium sulfate in their case was effective for stable hemodynamics , with the pattern of steadily decreasing catecholamine levels following intubation .
therefore , we presume that the decreasing trend of catecholamine levels could help to diminish sudden fluctuating changes of hemodynamics . in conclusion , the levels of perioperative catecholamines demonstrate that the combination of dexmedetomidine and remifentanil was an effective manner to achieve safe anesthesia in our patient .
the optimal intra - operative dosing and timing of dexmedetomidine and remifentanil remain to be determined , and a further study in this setting is needed .
 a 15-year - old adolescent with unilateral multiple adrenal pheochromocytoma had an episode of subcortical intracerebral hemorrhage and seizure 6 weeks before the surgery . 
 he was pretreated with terazosin , losartan , atenolol and levetiracetam for 2 weeks . 
 dexmedetomidine was started in the preoperative waiting area , and a combination of dexmedetomidine and remifentanil was continuously infused for most of anesthetic time . to control blood pressure , bolus injection of remifentanil and low - dose infusion of sodium nitroprusside , nicardipine , and esmolol were administered during three adrenergic crises . 
 there was minimal post - resection hypotension , and his trachea was extubated safely 20 min after the surgery . 
 he was discharged without noticeable complication . 
 his catecholamine levels showed the steadily decreasing pattern during the operation in this case . 
 though a combination of dexmedetomidine and remifentanil may not prevent the hemodynamic instability impeccably during the tumor manipulation , this combination seems to be the way of interrupting release of catecholamines and minimizing hemodynamic fluctuations . 
Case Report
Discussion