Increased activity of small GTP-binding protein-dependent phospholipase D during differentiation in human promyelocytic leukemic HL60 cells

In response to dibutyryl cyclic AMP (dbcAMP) and all-trans retinoic acid, human promyelocytic leukemic HL60 cells differentiate into granulocyte-like cells. In cell lysate and in vitro reconstitution system, phospholipase D (PLD) activity in response to guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS) was up-regulated by dbcAMP or all-trans retinoic acid treatment. In the present study, the mechanism(s) for increased PLD activity during differentiation was examined. Western blot analysis revealed that the contents of ADP-ribosylation factor, Rac2, and Cdc42Hs but not RhoA and Rac1 in the cytosolic fraction were elevated during differentiation. However, the cytosolic fraction from undifferentiated cells was almost equally potent as the cytosolic fraction from differentiated cells in the ability to stimulate membrane PLD activity. It was shown that the GTPgammaS-dependent PLD activity in membranes from differentiated cells was much higher than that in membranes from undifferentiated cells, suggesting that the increased PLD activity during differentiation was due to alterations in some membrane component(s). Clostridium botulinum ADP-ribosyltransferase C3 and C. difficile toxin B, which are known as inhibitors of RhoA and Rho family proteins, respectively, effectively suppressed PLD activity in membranes from differentiated cells. In fact, the amount of membrane-associated RhoA was increased during differentiation. Furthermore, the extent of GTPgammaS-dependent PLD activity partially purified from membranes from differentiated cells was greater than that from membranes from undifferentiated cells in the presence of recombinant ADP-ribosylation factor 1. The PLD (hPLD1) mRNA level was observed to be up-regulated during differentiation, as inferred by reverse transcription-polymerase chain reaction. Our results suggest the possibility that the increased Rho proteins in membranes and the changed level of PLD itself may be, at least in part, responsible for the increase in GTPgammaS-dependent PLD activity during granulocytic differentiation of HL60 cells.

[The differences of the cerebral and spinal vessels in sensitivity to PaCO2 and vasoconstrictors]

We investigated the differences in the response to arterial CO2 tension and vasoconstrictors between the cerebral and spinal vasculatures using cranial and spinal window technique which provided the direct observation of pial vessels. Pentobarbital anesthetized dogs (n = 18) (CO2 tension; n = 6 and vasoconstrictor; n = 12) were instrumented for measurement of pial vessel diameters by intravital microscopy in the cranial and spinal window preparation simultaneously. We achieved hypocarbia (20-25 mmHg) followed by adjusting CO2 levels for normocarbia (35-40 mmHg) and for hypercarbia (55-60 mmHg) using CO2 gas addition. After obtaining the desired PaCO2, the measurements were made. In the next experiment, we administered 2 different concentrations of epinephrine or phenylephrine solutions (1:2 x 10(6), 1:2 x 10(5)) through the window, and the measurement was made sequentially. The response of cerebral and spinal vasculature to change in PaCO2 was almost similar. Topical application of both drugs produced a significant constriction of spinal pial arterioles compared with the cerebral ones, while epinephrine but not phenylephrine constricted cerebral pial venules compared with spinal ones. These results suggest that the responses to vasoconstrictor of cerebral and spinal pial vessels are not similar, and high sensitivity of spinal arterioles to vasoconstrictors may possibly contribute to a risk of ischemic damage of the spinal cord.

[Usefulness of alpha 2-adrenoceptor agonists and practical problems associated with their use in clinical anesthesia--II. Effects in regional anesthesia and analgesic effects for pain relief]

In the second part of this review, we summarized the effects of alpha 2-adrenoceptor agonists (clonidine and dexamedetomidine) in regional anesthesia and pain control, and evaluated their usefulness as anesthetic adjuvants and analgesics in the clinical settings. In addition, we referred to practical problems associated with their use.

[Usefulness of alpha 2-adrenoceptor agonists and practical problems associated with their use in clinical anesthesia--1. Premedication, anesthetic adjuvants, and hemodynamic effects]

A great deal of new information on alpha 2-adrenoceptor agonists has recently been accumulated in humans; alpha 2-agonists have several beneficial actions in clinical anesthesia including sedative, anxiolytic as well as analgesic effects, improved hemodynamic stability, and etc. In the first part of this review, we summarized the structure, signal transmission and basic pharmacology of alpha 2-adrenoceptor agonists (clonidine and dexamedetomidine), and evaluated their usefulness for premedication, and as anesthetic adjuvants as well as agents for stabilizing circulation in the clinical settings. In addition, we referred to practical problems associated with their use.

[Effects of continuous epidural administration of fentanyl and morphine on postcesarean pain]

We studied the effects of continuous epidural administration of fentanyl and morphine with bupivacaine for management of postcesarean pain. Eighteen patients received either bolus epidural administration of fentanyl 100 micrograms or morphine 3 mg with 0.5% bupivacaine 4 ml, followed by continuous infusion of fentanyl 33 micrograms.ml-1 with 0.17% bupivacaine or morphine 0.21 mg.ml-1 with 0.17% bupivacaine for 48 hours, respectively. Pain score was assessed at 0 h, 12h, 24h and 48h after leaving the operating room. Pain score increased significantly and progressively in the fentanyl group. In all cases pruritus was noted. Severe pruritus was observed in the morphine group significantly more than in the fentanyl group. The current results indicate that morphine may be preferable to fentanyl for postcesarean pain control using the present opioid doses.

[Postoperative continuous epidural infusion of morphine in a patient with myotonic dystrophy]

Patients with myotonic dystrophy present potential problems during and after anesthesia, especially respiratory dysfunction. A 42-year-old female with myotonic dystrophy associated with slight impairment of respiratory functions and muscular power, underwent abdominal total hysterectomy under epidural anesthesia uneventfully. To relieve pain after the surgery, a bolus of epidural morphine 2 mg was administered through an indwelling lumbar (L1-2) epidural catheter 30 minutes prior to the end of the surgery and followed with continuous epidural infusion of morphine at a rate of 0.083 mg.h-1 using a balloon (Multiday Infuser, Baxter) for three days. She obtained adequate analgesia after the surgery without respiratory depression or other major complications. We demonstrated that the continuous epidural infusion of morphine in a patient with myotonic dystrophy is safe and adequate for postoperative pain relief.

[Nicorandil, as ATP-sensitive K+ channel opener, potentiated morphine analgesia]

Recent reports demonstrated that K+ channels could contribute to signal transmission in the brain and spinal cord, and opioids' action may be related to K+ channels' functions. We investigated the antinociceptive effect of epidurally injected ATP-sensitive K+ channel opener, nicorandil, using tail flick test in rats. Epidural nicorandil (100 micrograms.rat-1) increased % maximum possible effect (%MPE) of epidural morphine (1, 10 micrograms.rat-1) from -3% to 40% (P < 0.05) and 46% to 65%, respectively. Epidural glibenclamide (10 micrograms.rat-1), ATP-sensitive K+ channel blocker, antagonized this effect. Epidural nicorandil alone (10 approximately 100 micrograms.rat-1) showed no antinociceptive effects. Systemic nicorandil (100 micrograms.rat-1, i.m.) did not increase the epidural morphine analgesia. These data suggest that the K+ channel opener could point the way to a new approach to pain treatment.

[Prostaglandin E1 at low-doses improved right ventricular ejection fraction in anesthetic management for CABG]

A 52-year-old male for CABG developed a severe right heart failure, because of the direct injury to the right ventricular wall, after cardiopulmonary bypass. The volume loading therapy could not improve the cardiac function, then we used an infusion of low-dose prostaglandin E1 (0.02-0.04 micrograms.kg-1.min-1) for the acute right heart failure with increased pulmonary vascular resistance. After continuous infusion of this dose, the pulmonary vascular resistance decreased quickly, the right ventricular ejection fraction increased, and the stroke volume index also improved. These hemodynamic changes are the result of the potent vasodilating effect of PGE1, that especially could decrease selectively the pulmonary vascular resistance, and increase the preload of the left ventricle. This dose of PGE1, did not cause a severe systemic hypertension that is a serious complication during vasodilating therapy with any vasoactive drugs. In the present case, we speculated that the low-dose PGE1, is effective to improve the right ventricular function during the acute right heart failure which resulted from the intrinsic right ventricular dysfunction.

[Tizanidine for preanesthetic medication]

The effect of tizanidine given as a premedication on perioperative hemodynamics (mean blood pressure, heart rate), sedation, hypnosis and midazolam requirements for induction were assessed in 68 patients scheduled for elective surgery under general anesthesia. Patients were assigned to three groups. Group 1 was premedicated 90 min prior to induction with tizanidine 4 mg po (n = 28); group 2 was premedicated with tizanidine 2 mg po (n = 12); group 3 received no premedication (n = 28). In group 1, increase of mean blood pressure on anesthesia induction was attenuated significantly and sedative and hypnotic effects were stronger significantly compared with other groups. We also found that the amounts of midazolam necessary for loss of consciousness were significantly less in patients who had received tizanidine 4 mg. In conclusion, tizanidine is a useful drug as preanesthetic medication for general anesthesia.

[Anesthetic management of a patient with renal cell carcinoma extending into the right atrium]

A 60-year-old man with renal cell carcinoma extending through inferior vena cava into the right atrium was scheduled for the removal of the right kidney under general anesthesia and the cardiopulmonary bypass technique. In order to obtain a clear operative field and to minimize the risk for pulmonary embolism of necrotizing tumor, total circulatory arrest under profound hypothermia (20 degrees C) was performed. Anesthesia was maintained with high doses of fentanyl (62 micrograms.kg-1), midazolam and supplemented with enflurane. We attempted to prevent circulatory collapse due to acute pulmonary embolism by tumor fragments during operation. The body temperature of the patient was decreased down to 20 degrees C for protecting central nervous system with the minimal damage. No complications occurred during anesthesia and the post-operative period. For the safe anesthetic management of the patient such as our case, adequate monitoring of circulation and protection of central nervous system are essential.

[Intraoperative acute myocardial infarction during total gastrectomy under general anesthesia combined with thoracic epidural anesthesia]

A 61-year-old, 54-kg man with gastric cancer was scheduled for total gastrectomy under general anesthesia combined with thoracic epidural anesthesia. Approximately 20 minutes after the start of the operation, the patient developed sudden hypotension and ventricular fibrillation. The cardiac rhythm returned to normal after 38 minutes of cardiopulmonary resuscitation. The operation was discontinued and the patient was transferred to an intensive care unit. A 12-lead electrocardiogram (ECG) revealed complete right bundle branch block and elevation of the ST-segment from leads II, III, aVF, V1, and V2 which indicated an inferior myocardial infarction. Laboratory data showed elevated levels of enzymes such as glutamic oxaloacetic transaminase (495 IU.l-1), lactic dehydrogenase (1781 IU.l-1), and creatine kinase-MB (112 IU.l-1). The mildly elevated levels of the enzymes decreased around 10 hours after the termination of the operation, but they increased markedly again without any change in ECG on the second postoperative day. Elevation in serum myoglobin and glutamic pyruvic transaminase and decline in arterial ketone body ratio were also detected. Furthermore, renal failure developed with increase in blood urea nitrogen and creatinine. Because of hepatic failure and renal failure which might have been caused by rhabdomyolysis, the patient needed inotropic support with dopamine, dobutamine, and epinephrine to maintain the circulation. The patient died of reinfarction of the 20th postoperative day despite intensive care such as intraaortic balloon pumping, hemodiafiltration, and continuous intravenous infusion of prostaglandin E1.

[Perioperative managements of a mentally retarded child with obstructive sleep apnea syndrome for adeno-tonsillectomy]

We describe a mentally retarded child with obstructive sleep apnea syndrome (OSAS) in whom it was difficult to maintain upper airway in the perioperative period. The child underwent awake intubation, because the preanesthetic evaluation of the airway with a direct fiberoptic visualization revealed a very narrow airway. Also we considered that if we used an anesthetic agent, a perioperative airway management would be very troublesome. Postoperatively we continuously monitored for apnea and arrhythmias. When the child was sleeping, we found frequently that her thoratic movements were getting weak and percutaneous oxygen saturation went down to about 70 percent. The preoperative direct fiberoptic visualization of the upper airway is effective for the evaluation of the degree of airway obstruction in this child. We also recommend the continuous intensive postoperative monitorings including pulse oximetry, ECG, and apnea monitor which are very important to avoid life-threatening complications such as upper airway obstruction and serious arrhythmias in patients with obstructive sleep apnea syndrome.

Mechanisms of dexmedetomidine-induced cerebrovascular effects in canine in vivo experiments

Dexmedetomidine decreases cerebral blood flow without significantly affecting cerebral oxygen consumption in anesthetized dogs. To assess the direct cerebrovascular effects of dexmedetomidine, we investigated the responses of vasomotor tone to topical application of dexmedetomidine to pial vessels in vivo, using a parietal cranial window. Forty-one dogs were anesthetized with pentobarbital. In 20 dogs, we topically applied six concentrations of dexmedetomidine solution (10(-8), 10(-7), 10(-6), 10(-5), 10(-4), 10(-3) M) and directly measured pial arterial and venous diameters. In 10 dogs, the inhibitory effects of pretreatment of pial vessels with 10(-5) M yohimbine were examined after the application of 10(-5) dexmedetomidine. In the remaining 11 dogs, the effects of 10(-3) M dexmedetomidine were evaluated in the presence of N omega-nitro-L-arginine methyl ester (L-NAME), glibenclamide, or propranolol. Dexmedetomidine significantly constricted pial arteries and veins in a concentration-dependent manner (10(-7) M to 10(-4) M; P < 0.05). Yohimbine blocked dexmedetomidine-induced constriction of pial vessels (both large and small arteries and large veins P < 0.0001; small veins P < 0.005). However, when the highest concentration of dexmedetomidine (10(-3) M) was administered under the window, pial vessel diameter was not significantly altered. In the presence of glibenclamide, 10(-7) and 10(-3) M dexmedetomidine induced a significant decrease in pial arterial diameter compared with 10(-7) and 10(-3) M dexmedetomidine solution alone, respectively (P < 0.05). L-NAME or propranolol did not affect the dexmedetomidine-induced constriction.(ABSTRACT TRUNCATED AT 250 WORDS)

[Opioid receptors altered binding nature in guinea-pig brain following the development of morphine dependence]

Morphine is well known to produce tolerance and dependence. The mechanisms for these phenomena are not clearly understood and there are a number of conflicting reports that chronic morphine administration decreases, increases, or leaves unchanged the number of opioid binding sites. We examined the potency of MScontin (oral controlled-release preparation of morphine) to induce morphine dependence and also determined the change of mu, delta and kappa opioid receptor types in brain homogenates obtained from morphine-dependent guinea-pigs. 1. Guinea-pigs were implanted subcutaneously with MScontin (300 mg.kg-1) and naloxone was employed to precipitate jumping behavior of withdrawal symptoms at various times. The highest degree of physical dependence was observed on the 2nd day after implantation. Therefore, this period was chosen to investigate opioid receptor binding assay. 2. Two days after implantation, the binding of 3H-DAGO (mu agonist), 3H-DPDPE (delta agonist) and 3H-U69593 (kappa agonist) to brain membranes prepared from morphine dependent and control guinea-pigs was determined. Scatchard plot of the saturation binding data revealed an increase in Bmax values (maximum specific binding) and no change in the Kd values (equilibrium dissociation constants) of 3H-opioid ligand bindings obtained from morphine-dependent animals as compared to controls. These results indicate that brain mu, delta and kappa opioid receptors are up-regulated in morphine dependent guinea-pigs.

[The mu, delta and kappa properties of various opioids]

Recently, the highly selective mu, delta and kappa radiolabeled opioid ligands, such as 3H-DAGO (mu ligand), 3H-DPDPE (delta ligand) and 3H-U69593 (kappa ligand) are available. Using the kappa-homogeneous preparations from human placenta and mu-enriched gerbil cerebellum membrane preparations with these highly selective radiolabeled opioid ligands, clinically used opioids were tested for their mu, delta and kappa properties. The mu agonists such as morphine and fentanyl display a very low affinity for delta and kappa receptor. Among the agonist-antagonist, buprenorphine and butorphanol appeared to be the most highly selective agonists for mu and kappa opioid receptors, respectively. Most ligands identified as specific agonists are in fact only selective and appear to interact at more than one receptor type.

[Calcitonin gene-related peptide and human atrial natriuretic hormone levels in response to cardiac operation under high dose fentanyl anesthesia]

To elucidate a role of calcitonin gene-related peptide (CGRP) in anesthesia and surgery with cardiopulmonary bypass (CPB), we measured CGRP which is reported to be a marker for fluid overload, simultaneously with HANP (human atrial natriuretic hormone) in 12 patients during high dose fentanyl anesthesia (50-70 microgram. kg-1). Plasma concentration of CGRP increased to 3 times of the value during preanesthetic phase at 30 min after initiation of CPB. A 3-fold increase compared with control in CGRP occurred 30 min after initiation of CPB. A 3-fold increase in HANP also occurred just before termination of CPB. But, there was no correlation between plasma levels of CGRP and HANP. The changes in CGRP did not relate with those of pulmonary capillary wedge pressure. The results of the present study suggest that the mechanism for the increase is unclear, and CGRP could be influenced during cardiac or coronary artery surgery using CPB.

[The effects of systemic bupivacaine on baroreflex sensitivity in dogs]

To evaluate the effects of systemic bupivacaine on the baroreflex control of heart rate, we investigated the baroreflex sensitivity assessed with a pressor and a depressor test using phenylephrine and nitroglycerin in pentobarbital anesthetized dogs (n = 12). Intravenous injection of bupivacaine (mean plasma concentration of 2.4 +/- 0.9 micrograms.ml-1) caused a significant suppression of the baroreflex sensitivity, defined by the slopes of regression line (in msec of RR interval change per mmHg increase or decrease in systolic blood pressure). The sensitivity obtained with the pressor and the depressor tests decreased from 6.0 +/- 2.3 to 3.5 +/- 1.7, from 2.4 +/- 1.3 to 1.3 +/- 0.8 msec.mmHg-1, respectively (P < 0.01). Suppression of the baroreflex sensitivity during epidural anesthesia with bupivacaine could be due not only to cardiac sympathectomy but also to a direct effect of bupivacaine on the reflex arch including the receptors, the afferent nerve pathways, the CNS, the efferent pathway, and the effector organs. Therefore, the hemodynamic responses to reduction of blood pressure are likely to be inhibited by epidural bupivacaine.

[Mediastinal abscess diagnosed after its rupture into the trachea in a patient after esophagectomy]

A 52-yr-old man with esophageal cancer underwent esophagectomy and retrosternal reconstruction using stomach under general anesthesia. In the postoperative period, the patient developed mediastinal abscess which failed to be diagnosed by daily routine chest X-rays, because of surgical alterations of mediastinal anatomy. On the 11th postoperative day, the abscess ruptured into the trachea and severe hypoxemia (PaO2 73 mmHg, FIO2 1.0) developed while the patient was still on mechanical ventilation. A chest X-ray on that day showed a radiolucent cavity with defined margins in the right superior mediastinum. Thoracic CT scanning on the 15th postoperative day disclosed a capsulated cavity which indicated abscess formation in the posterior mediastinum. Although surgical drainage was not undertaken, the patient's severe hypoxemia was resolved within 4 days by the supportive therapies including chest physiotherapy, postural drainage and administration of antibiotics and corticosteroids. Although mediastinal abscess after esophagectomy is a rare complication, it may rupture into the trachea and lead to severe hypoxemia. In this case thoracic CT scanning was useful to detect the mediastinal abscess which had not been diagnosed by routine chest X-rays.

[The catecholamine concentrations of collected autologous blood during adrenalectomy for pheochromocytoma]

We studied the catecholamine concentrations in collected autologous blood of a patient undergoing adrenalectomy for pheochromocytoma. In the preoperative laboratory data, plasma concentrations (normal ranges) of epinephrine, norepinephrine and dopamine were 60180 pg.ml-1 (< 100), 11090 pg.ml-1 (100-450) and 104 pg.ml-1 (< 20), respectively. The catecholamine levels of collected blood were epinephrine 2490000 pg.ml-1, norepinephrine 352300 pg.ml-1 and dopamine 6100 pg.ml-1 before wash. Wash of collected blood with 1000 ml saline diluted the catecholamines to epinephrine 212000 pg.ml-1, norepinephrine 18700 pg.ml-1 and dopamine 4900 pg.ml-1. Platelet activation by contact with tissue collagen or thrombin results in the release of catecholamine concentrated in the dense body. The mechanical stimulation by suction, roller pump and centrifugation during blood collection may accelerate the catecholamine release from platelets. Thus, saline wash hardly reduces catecholamine concentrations of collected blood from a patient with pheochromocytoma. In this particular case, plasma catecholamines seem to exceed the potential capacity of platelets in amount. The dilution effect for epinephrine and norepinephrine probably reflects the washout of greater amount of plasma catecholamines. However, saline wash was unable to reduce catecholamines contained in the collected blood to a safe level, and hypertension following autotransfusion was predictable. We conclude that hemodynamic change should be monitored carefully during intraoperative autotransfusion in a case of pheochromocytoma.

Engraftment of precursor lesions of human cutaneous neoplasms onto C.B-17 SCID mice: a useful in vivo experimental model of carcinogenesis in human skin

Using a full-thickness skin grafting technique, lesional skin from various human neoplastic and preneoplastic skin diseases was transplanted onto SCID (severe combined immunodeficiency) mice. Of 27 grafted lesions, 21 were successfully accepted by the mice and maintained in good condition. All these accepted grafts were finally excised 10-101 days after transplantation for histological examination. In most grafts, the characteristic histological configurations of each disease were well preserved. Immunohistochemical study using monoclonal antibodies to human blood group antigens ABH revealed that some elements of the grafts such as sweat glands were clearly positive, confirming that the tissue was from human skin. Neoplastic (atypical) cells were detected in 9 of 17 accepted grafts containing neoplastic cells from the beginning. The detection rates for neoplastic cells were very high (90%) in grafts from precursor lesions of squamous cell carcinomas such as Bowen's disease (5/5 specimens) and thermal keratosis (2/3). In contrast, no definite neoplastic cells were found in two grafts from extramammary Paget's disease and five grafts from the radial growth component of malignant melanoma. In most of the grafts from latter two diseases, characteristic histological configurations such as elongation of the rete ridges were maintained, suggesting that the neoplastic cells were selectively eliminated from the grafts. Split-thickness grafts of normal human skin were accepted and remained in a good condition for as long as 6 months. Engraftment of human lesional and non-lesional skin onto SCID mice therefore may well provide a useful in vivo experimental model of human skin diseases.

[The concentration effects of isoflurane-N2O anesthesia on cardiovascular responses to skin incision]

To investigate the concentration effects of isoflurane-nitrous oxide anesthesia on cardiovascular responses to skin incision, we studied 24 non-premedicated patients undergoing lower abdominal operation. Anesthesia was induced with inhalation of 70% nitrous oxide and isoflurane, and maintained with 70% nitrous oxide and three different concentrations of isoflurane (1.25, 1.6, 1.95 MAC). Blood pressure and heart rate were recorded continuously before and after skin incision. Because more than half the patients with 1.95 MAC became hypotensive with systolic blood pressure of less than 80 mmHg just before the skin incision, it was difficult to define the values of MAC BAR (blocking adrenergic responses) in the present study. Cardiovascular responses at skin incision were not completely suppressed at 1.6 MAC isoflurane-N2O anesthesia and no further blocking effects were obtained at 1.95 MAC isoflurane-N2O anesthesia. These results suggest that higher concentration of isoflurane does not guarantee stronger protective effects on stimulation like skin incision.

[Strategies of general anesthesia for cleft palate surgery in Cambodia]

Hare lip and cleft palate surgery team activities in Cambodia were launched in 1989 by a non-governmental Japanese organization, Operations Unies. The objectives of the project are to provide appropriate surgical treatment and safe general anesthesia for local patients and also to conduct technology transfer of general anesthesia and surgery to the local medical staffs. From June 1991 to January 1993, a surgery/anesthesia team was dispatched 4 times and a total of 130 patients received surgical treatments under general anesthesia. Anesthesia techniques employed included total intravenous anesthesia in 70 patients (54%) and intravenous anesthesia with 0.3-0.7% of halothane in 60 patients (46%). There were no major complications, such as airway obstruction and apnea, in the recovery room and in the ward. The reasons why we chose intravenous agents are difficulty in obtaining inhaled agents in Cambodia and lack of scavenging system in a operating room. Although halothane anesthesia with spontaneous breathing has been recommended in developing countries, total intravenous anesthesia could be one of the applicable techniques in these countries. In Cambodia, shortage of medical doctors and the absence of anesthesiologist constitute a major barrier to technology transfer in clinical anesthesia.

Diuretic effect of clonidine during isoflurane, nitrous oxide, and oxygen anesthesia

BACKGROUND

Because clonidine, a relative selective alpha 2-agonist, inhibits the action of arginine vasopressin (AVP), the authors examined whether clonidine as an oral preanesthetic medication would induce diuresis and also would affect AVP release and its action during general anesthesia.

METHODS

Fifty-seven patients (aged 18-65 yr) randomly received oral clonidine either approximately 5 micrograms.kg-1 (n = 19), approximately 2.5 micrograms.kg-1 (n = 19), or none (n = 19) in addition to oral famotidine 20 mg, 90 min before arrival at operating room. Urine volume, urine osmolality, and amount of sodium and potassium excreted into urine were examined every hour for 3 h during minor surgery under general anesthesia with isoflurane and nitrous oxide in oxygen. For 5 patients of each group, plasma AVP and atrial natriuretic peptide concentrations and urine cyclic adenosine monophosphate concentrations as an index of AVP action were also assayed.

RESULTS

Urine output indices (calculated as hourly urine output [milliliters per hour] divided by body weight [kilograms]) were significantly greater in the all periods (P < or = 0.035) after the initiation of anesthesia in the patients receiving clonidine 5 micrograms.kg-1 and only in the 3rd h in those receiving clonidine 2.5 micrograms.kg-1 (P = 0.047) as compared with those in the patients given famotidine alone. The peak effects of diuresis and natriuresis induced by oral clonidine 5 micrograms.kg-1 were both observed at the 2nd h (mean +/- SEM, 2.4 +/- 0.4 ml.kg-1.h-1 and 5.7 +/- 1.5 mEq.h-1 vs. 0.6 +/- 0.1 ml.kg-1.h-1 and 2.2 +/- 0.5 mEq.h-1 in the control subjects; P = 0.001 and P = 0.049). Kaliuresis also increased in the patients receiving clonidine 5 micrograms.kg-1 in the 2nd and 3rd h (P < or = 0.003). Urine osmolality showed a significant reduction over time in patients given clonidine but not in the control subjects. However, plasma AVP and atrial natriuretic peptide levels, and urine cyclic adenosine monophosphate concentrations did not significantly differ among the three groups.

CONCLUSIONS

Oral preanesthetic medication of clonidine 2.5 or 5 micrograms.kg-1 caused a significant diuretic effect during surgery under general anesthesia, though it did not apparently relate to AVP action. This effect of clonidine could be related to its pharmacological action as an alpha 2-adrenoceptor agonist not necessarily restricted to the kidney. The diuretic effect of clonidine implicates its clinical importance in the management of patients during anesthesia.