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Biomedical subjects

P W Lui

Publications and source records attributed to P W Lui.

At least 37 records · Page 2Linked to original sources
PubMed1999

Postoperative pulmonary edema after cervical spine surgery--a case report.

Injury of the cervical spine may cause serious complications and neurological sequelae. Recently, a patient with C1-2 spinal cord compression developed pulmonary edema postoperatively associated with unstable hemodynamics, which might result from overzealous fluid administration in order to correct neurogenic shock during anesthesia. Therefore, early recognition and timely use of vasoconstrictors, together with judicious fluid replacement are important in the anesthetic management of patients with cervical spine injury undergoing surgery. In addition, the placement of pulmonary artery catheter is crucial for assessing the cardiac function and fluid status.

Adult↗
PubMed1999

Postoperative right atrial and pulmonary embolism after prolonged spinal surgery.

Perioperative pulmonary thromboembolism can proceed rapidly with grave prognosis, in which immediate or accurate diagnosis and management is not easy. According to the literatures, patients receiving spinal surgery are at relatively lower risk of developing thromboembolism. We would like to present a case of postoperative pulmonary thromboembolism which developed after a prolonged lumbar spinal surgery. Tachycardia and unstable hemodynamics were noted postoperatively. Pulmonary and right atrial thrombi were disclosed by transesophageal echocardiography. Although cardiotomy and thrombectomy were immediately performed, the patient finally died 3 days after the operation. The pathogenesis of venous thromboembolism (VTE) in the surgical patients, the risk factors which predispose a patient to VTE, diagnosis, and treatment as well as the prophylactic measures of VTE are herein reviewed and discussed.

Aged↗
PubMed1998

Wavelet analysis of embolic heart sound detected by precordial Doppler ultrasound during continuous venous air embolism in dogs.

UNLABELLED: The spectrum of the embolic heart sounds (EHS) detected by precordial Doppler ultrasound has been previously characterized, but only on small volumes of venous air embolism (VAE). We sought to determine whether real-time wavelet analysis is useful in analyzing the signals of EHS and whether the embolic power of the EHS for larger volumes of air is proportionate to the volume of VAE that has been reported for small volumes of VAE. A series of small air boli (0.01, 0.02, 0.05, 0.07, 0.1, 0.15, 0.2, 0.3, 0.4, and 0.8 mL), followed by continuous infusion of larger volumes of air (0.8, 1.6, 2.4, 4.8, and 9.6 mL), was injected into the external jugular vein through a central catheter in seven pentobarbital-anesthetized dogs. We measured the spectrum of the Doppler heart sound (DHS) in a real-time manner by using wavelet analysis at different scales. Wavelet analysis at scale = 1 yielded satisfactory results in distinguishing abnormal EHS from normal DHS with high sensitivity (100%) and good positive predictive value (100%) compared with the conventional method, which requires an anesthesiologist to listen to the audio DHS signals in a real-time manner. There was a linear relationship (y = 1.08x + 7.89, r = 0.75, P < 0.001) between the cumulative embolic power of the EHS and the air volume introduced in the form of either bolus or continuous infusion. The 95% confidence intervals for slope and intercept were 0.89-1.27 and 7.65-8.13, respectively. Our results suggest that wavelet analysis is effective as a real-time monitor and that it is possible to distinguish larger volumes of air emboli based on previous injections of small volumes of air. IMPLICATIONS: The real-time wavelet analysis of the heart sound detected by precordial Doppler ultrasound may be useful in estimating larger volumes of air emboli based on previous injections of small volumes of air in anesthetized dogs.

Animals↗
PubMed1997

Involvement of spinal adenosine A1 and A2 receptors in fentanyl-induced muscular rigidity in the rat.

In the present study, using hydrophilic adenosine antagonists either selective to A1 or A2 receptors, we investigated the central and spinal adenosinergic participation in fentanyl-induced muscular rigidity. Adult Sprague-Dawley rats were anesthetized with ketamine and were under mechanical ventilation. Fentanyl (100 micrograms/kg, i.v.) consistently elicited electromyographic (EMG) activation in the sacrococcygeal dorsalis lateralis muscle. This implied muscular rigidity was not blocked by i.c.v. administration of the adenosine A1 antagonist, 1-allyl-3,7-dimethyl-8-p-sulfophenyl-xanthine (ADSPX; 20 or 40 nmol/2.5 microliters), except at higher dose (80 nmol). Equimolar doses of the adenosine A2 antagonist, 3,7-dimethyl-1-propargylxanthane (DMPX), did not exert any inhibitory effect on fentanyl-induced rigidity. Intrathecal (i.t.) administration of the same doses of ADSPX (20, 40 or 80 nmol/10 microliters) appreciably suppressed the EMG activation. However, the rigidity was only inhibited by 40 or 80 nmol (i.t.) of DMPX, but not by the lowest dose. High-dose (80 nmol, i.t.) adenosine A1 or A2 antagonist per se did not induce motor impairment or hindlimb paralysis in conscious animals. These results suggest that adenosine A1 and A2 receptors in the spinal cord may play a more crucial role than those in the central nervous system (CNS) in fentanyl-induced muscular rigidity in rats.

Animals↗
PubMed1997

Involvement of cerulospinal glutamatergic neurotransmission in fentanyl-induced muscular rigidity in the rat.

BACKGROUND: Investigators in the authors' laboratory previously established the critical participation of the cerulospinal noradrenergic pathway in muscular rigidity elicited by fentanyl. The identification of colocalization of glutamate with tyrosine hydroxylase in most locus ceruleus neurons suggests a role for cerulospinal glutamatergic neurotransmission in fentanyl-induced muscular rigidity. This suggestion and the subtype(s) of glutamate receptors involved were investigated here. METHODS: Electromyographic signals activated by bilateral microinjection of 2.5 microg fentanyl into the locus ceruleus were recorded differentially from the left sacrococcygeus dorsi lateralis muscle of adult male Sprague-Dawley rats. The effect of intrathecal administration at the lower lumbar spinal cord of various N-methyl-D-aspartate (NMDA) and non-NMDA receptor antagonists or agonists on this index of muscular rigidity was studied. Rats were under mechanical ventilation, and intravenous infusion of ketamine (30 mg x kg(-1) x h(-1)) was maintained until 10 min before fentanyl was administered. RESULTS: Microinjection of fentanyl bilaterally into the locus ceruleus increased the root mean square and decreased the mean power frequency values of electromyographic signals. The efficacy of fentanyl to elicit muscular rigidity in this manner was significantly reduced by previous intrathecal administration of either 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate (MK-801), D-(-)-2-amino-5-phosphonovaleric acid (AP5), or (+/-)-3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP). Intrathecal administration of kainic acid or NMDA also resulted in significant electromyographic activation. CONCLUSIONS: In addition to the cerulospinal noradrenergic mechanism, the cerulospinal glutamatergic pathway and both NMDA and non-NMDA receptors in the spinal cord may mediate fentanyl-induced muscular rigidity in the rat.

Analgesics, Opioid↗
PubMed1997

Fast detection of venous air embolism in Doppler heart sound using the wavelet transform.

The introduction of air bubbles into the systemic circulation can result in significant morbidity. Real-time monitoring of continuous heart sound in patients detected by precordial Doppler ultrasound is, thus, vital for early detection of venous air embolism (VAE) during surgery. In this study, the multiscale feature of wavelet transforms (WT's) is exploited to examine the embolic Doppler heart sound (DHS) during intravenous air injections in dogs. As both humans and dogs share similar physiological conditions, our methods and results for dogs are expected to be applicable to humans. The WT of DHS at scale 2j (j = 1, 2) selectively magnified the power of embolic, but not the normal, heart sound. Statistically, the enhanced embolic power was found to be sensitive (P < 0.01 at 0.01 ml of injected air) and correlated significantly (P < 0.0005, r = 0.83) with the volume of injected air from 0.01 to 0.10 ml. A fast detection algorithm of O(N) complexity with unit complexity constant for VAE was developed (processing speed = 8 ms per heartbeat), which confirmed the feasibility of real-time processing for both humans and dogs.

Algorithms↗
PubMed1996

Terbutaline inhalation suppresses fentanyl-induced coughing.

PURPOSE: To study the suppressive effect of inhalation of a selective beta 2-adrenergic bronchodilator terbutaline, and the effect of an intravenous anticholinergic, atropine, on fentanyl-induced coughing. METHODS: We studied 131 ASA class I patients, aged 16-45 yr, scheduled for elective surgery, randomized into four groups. Fifteen minutes before bolus fentanyl (5 micrograms.kg-1, iv), patients inhaled either normal saline (4 ml; Group I, n = 30) or terbutaline (5 mg in 2 ml normal saline; Group 2, n = 34) via a jet nebulizer. After inhalation of normal saline, patients in Group 3 (n = 32) received sterile water iv instead of fentanyl. Patients in Group 4 (n = 35) were pretreated with atropine (0.01 mg.kg-1, iv) 10 min before iv fentanyl bolus. The onset, frequency and intensity of cough were observed immediately by an anaesthetist blinded to the study. RESULTS: The cough frequency was higher in Groups I (43%) and 4 (46%) than in Groups 2 (3%) and 3 (0%) (P < 0.05). The onset time and intensity of cough showed no difference among groups. No truncal rigidity was observed in patients receiving fentanyl bolus iv. The blood pressure, heart rate, and peripheral oxygen saturation did not change in Groups 1, 2, and 3, while patients in Group 4 showed an increase in heart rate (25.5 +/- 15.2%). CONCLUSIONS: The inhalation of a selective beta 2-adrenergic bronchodilator, terbutaline, effectively inhibited fentanyl-induced cough, whereas atropine, an antimuscarinic vagolytic, had no efficacy. Our results suggest that bronchoconstriction may underlie the mechanism on fentanyl-induced cough.

Administration, Inhalation↗
PubMed1996

EMG spike trains of succinylcholine-induced fasciculations in myalgic patients.

Single spike activity from the surface electromyogram (EMG) of fasciculations induced by succinylcholine (Sch) were studied from limb muscles (biceps, triceps, anterior tibialis and gastrocnemius) in 100 female patients. About 2/3 of them (n = 72) also received nondepolarizing neuromuscular pretreatment (atracurium or vecuronium). We observed from 20% of EMG records in the myalgic (but not in the nonmyalgic) patients, sustained spike trains (mean duration 1.47 s) that resembled motor units firing at physiologically high rates (mean 21.7 spikes/s). The finding reflects Sch's distal actions at the muscle spindle. The implications for myalgia and the possible involvement of micro damage at the extrafusal muscles are discussed.

Action Potentials↗
PubMed1996

Incidence and risk factors of guidewire-induced arrhythmia during internal jugular venous catheterization: comparison of marked and plain J-wires.

STUDY OBJECTIVES: To compare the incidence and risk factors of guidewire-induced arrhythmia (GIA) during internal jugular venous catheterization (IJV). DESIGN: Prospective study. SETTING: Operating rooms at a medical center. PATIENTS: 303 ASA physical status I, II, III, and IV patients undergoing elective surgery. INTERVENTIONS: All patients were cannulated with the central venous catheters placed via the right internal jugular vein after induction of anesthesia. They were randomly divided into two groups. In one group, we used a marked J-wire and inverted up to, but not beyond 20 cm (Group M, n = 127). In the other group, a plain unmarked J-wire was used and inserted at will (Group UM, n = 176). All IJV catheterizations were performed by residents, and the length of J-wire inserted was then measured. MEASUREMENTS AND MAIN RESULTS: Types of arrhythmia [eg, premature atrial contraction (PAC) or premature ventricular contraction (PVC)] were interpreted by attending anesthesiologists on lead II ECG. Patients in Group UM had a significantly greater incidence of GIA than those in Group M (28.4% vs. 3.9%; p < .005). However, in both groups, PAC occurred more frequently than PVC. Factors such as the inserted length of guidewire longer than 20 cm, body height less than 170 cm, and female gender were significantly associated with GIA (p < 0.005). CONCLUSIONS: Limiting the length of the guidewire insertion to less than or equal to 20 cm for right IJV catheterization by using a marked J-wire will reduce the incidence of GIA. We recommend the use of a marked J-wire for IJV catheterization.

Adolescent↗
PubMed1996

Spectral analysis of arterial pressure variability during induction of propofol anesthesia.

We studied the effect of continuous infusion of propofol on spectral components in systemic arterial pressure (SAP) signals in 35 consenting patients undergoing abdominal surgery. Anesthesia was induced with intravenous bolus administration of propofol (2.0 mg/kg), followed by infusion at either 5 mg.kg-1.h-1 (Group 1, n = 18) or 10 mg.kg-1.h-1 (Group 2, n = 17). Tracheal intubation was facilitated by administration of vecuronium (0.1 mg/kg). The SAP signal was subjected to off-line spectral analysis to obtain changes in power of the very low frequency (VLF; 0.00-0.08 Hz), low frequency (LF; 0.08-0.15 Hz), high frequency (0.15-0.25 Hz); and very high frequency (VHF; 0.80-1.60 Hz) components. Venous blood for the measurement of plasma concentration of propofol was collected at 5 min before bolus injection of propofol; at 5, 10, and 15 min after infusion of propofol; and immediately after endotracheal intubation. Infusion of propofol significantly decreased the total power of SAP spectrum in both groups, especially the VLF, LF, and VHF components at all intervals except postintubation. Immediately after tracheal intubation, patients in Group 1 showed a significant increase in mean arterial pressure when compared with those in Group 2 (118 +/- 5 mm Hg vs 102 +/- 5 mm Hg, P < 0.05). Similar change was also seen in the VLF component (7.4 +/- 0.7 mm Hg2 vs 4.4 +/- 0.5 mm Hg2, P < 0.05). After tracheal intubation, patients in Group 1 showed 15.7-, 3.3-, and 4.4-fold increase in the VLF, LF, and VHF components, respectively. There were 14.1-, 2.8-, and 2.8-fold increases in the respective components of the SAP signal in Group 2. At all intervals, the spectral components of SAP, however, did not correlate well with the plasma concentration of propofol in either group. These results suggest that spectral analysis of SAP signals may provide an alternative for assessing autonomic activities, such as the sympathetic response, to tracheal intubation during propofol anesthesia.

Abdomen↗
PubMed1996

A child of suspected malignant hyperthermia during general anesthesia for dental surgery.

Malignant hyperthermia is clinically an uncommon disorder characterized by acute hypercatabolic reactions in muscles in response to the triggering effects of certain drugs mainly used during anesthesia or to physical or emotional stress. We present a pediatric patient with multiple caries who was suspected to contract malignant hyperthermia while underwent the operative procedure of comprehensive restoration. Sinus tachycardia, hyperthermia, hypercapnia, metabolic acidosis, hyperkalemia and hypercalcemia developed unexpectedly during the operation. Fortunately, the patient survived the episode with early recognition and prompt management.

Anesthesia, General↗
PubMed1996

Comparison of diuretic effects of glycerol with furosemide after transurethral prostatectomy.

BACKGROUND: Diuretic therapy after transurethral prostatectomy (TURP) is primarily intended to induce diuresis against water intoxication and cystic clot retention. This study was undertaken to compare the diuretic effects of glycerol with furosemide after TURP. METHODS: Thirty patients (ASA I or II) undergoing TURP were studied. Spinal anesthesia was induced with bupivacaine. At the end of prostatic resection, the patients were randomly allocated into two groups. In one group (n = 15) the patients received furosemide 30 mg i.v., while in the other group (n = 15) they received glycerol 0.5 g/kg i.v. Blood samples were collected for measurements of osmolality, hematocrit, sodium and glucose concentration before anesthesia and after surgery. Urine output was also recorded after surgery in each group. RESULTS: Plasma osmolality in glycerol group was higher than furosemide group at 30 min (295.3 +/- 10.6 vs. 283.8 +/- 5.6 mOsm/kg, p < 0.01) and 1 h after operation (294.9 +/- 8.7 vs 286.3 +/- 6.7 mOsm/kg, p < 0.01). Blood glucose was higher in glycerol group than that in furosemide group at 2 h after operation (195.6 +/- 121.9 vs 152.9 +/- 70.1 mg/dl, p < 0.05). Measured urine output was significantly greater in furosemide group at 30 min after operation (904.6 +/- 491.5 vs. 248.4 +/- 143.4 ml, p < 0.05) but was greater in glycerol group at 12 h after operation. CONCLUSIONS: Since urine output is significantly less in glycerol group at 1 h after operation, glycerol is inferior to furosemide for preventing cystic clot retention after TURP. But glycerol may protect against water intoxication better for its merit of producing higher plasma osmolality.

Aged↗
PubMed1995

Inhibition by intrathecal prazosin but not yohimbine of fentanyl-induced muscular rigidity in the rat.

We evaluated the effect of intrathecally administered prazosin, alpha 1-adrenoceptor antagonist, or yohimbine, alpha 2-adrenoceptor antagonist, on fentanyl-induced muscular rigidity. Adult, male Sprague-Dawley rats were anesthetized with ketamine and were under mechanical ventilation. Fentanyl given intravenously (100 micrograms/kg) or microinjected into the bilateral locus coeruleus (LC) (2.5 microgram/50 nl) consistently evoked a significant increase in the electromyographic activity recorded from the sacrococcygeus dorsalis lateralis muscle. This implied muscular rigidity was appreciably antagonized by prior intrathecal (10 microliters) administration of prazosin (5 or 10 nmol), but not equimolar dose of yohimbine. These results suggest that the spinal alpha 1-adrenoceptors in the coerulospinal noradrenergic pathway play a key role in fentanyl-induced muscular rigidity.

Adrenergic alpha-Antagonists↗
PubMed1995

Involvement of potassium and calcium channels at the locus coeruleus in fentanyl-induced muscular rigidity in the rat.

Previous work from our laboratory suggested that Go alpha protein at the locus coeruleus (LC) may be involved in the signal transduction process that underlies muscular rigidity induced by fentanyl. The present study further evaluated the roles of K+ and L-type Ca2+ channels, gating of which is known to be associated with activation of Go alpha protein, in this process, using Sprague-Dawley rats anesthetized with ketamine. Bilateral microinjection into the LC of tetraethylammonium chloride (100 or 200 pmol), a K+ channel blocker, and S(-)-Bay K 8644 (0.5 nmol), a Ca2+ channel activator, produced significant antagonization of the EMG activation elicited by fentanyl (100 micrograms/kg, i.v.), as recorded from the sacrococcygeus dorsalis lateralis muscle. On the other hand, local application to the bilateral LC of diazoxide (10 or 20 nmol), an ATP-dependent K+ channel activator, and nifedipine (0.25 or 0.5 pmol), a L-type Ca2+ channel blocker, was ineffective in blunting fentanyl-induced muscular rigidity. These results suggest that activation of K+ channels and/or inhibition of L-type Ca2+ channels secondary to triggering of the Go alpha protein at the LC may underlie the signal transduction process in the mediation of fentanyl-induced muscular rigidity.

Animals↗
PubMed1995

Magnesium sulfate has negligible effect on middle cerebral artery blood flow velocity in response to endotracheal intubation.

BACKGROUND: Pretreatment of magnesium sulfate (MgSO4) attenuates pressor response associated with endotracheal intubation. Vasodilating effect of MgSO4 may increase cerebral blood flow, which upsets the known benefit to cardiovascular hemodynamic. In the present study, we evaluated the effect of MgSO4 on the changes of cerebral blood flow in response to endotracheal intubation. METHODS: Twenty four ASA class I or II patients who randomly received either normal saline 5 ml or MgSO4 (60 mg/kg, i.v.) 3 min before induction of anesthesia were included in the study. Mean blood flow velocity (VMCA) of the middle cerebral artery was obtained using a transcranial Doppler sonography (TCD) before and after endotracheal intubation. Anesthesia was induced with fentanyl (4 micrograms/kg) and thiopental (5 mg/kg) and endotracheal intubation was facilitated with succinylcholine (1.5 mg/kg). RESULTS: Before endotracheal intubation, MgSO4 caused a transient decrease in VMCA (98 +/- 6% vs. 76 +/- 3% of baseline) and increase in heart rate (132% vs. 114% of baseline) compared to saline group. However, VMCA and heart rate did not show significant difference in both groups after tracheal intubation. Also, systolic and diastolic blood pressure did not differ during the study. CONCLUSIONS: Our results suggest that MgSO4 appeared to have negligible effects on cerebral blood flow and hemodynamics in response to tracheal intubation. Its attenuating effect on pressor response induced by endotracheal intubation might be over emphasized.

Adult↗
PubMed1995

Mannitol increases cerebral arteriovenous oxygen difference in patients undergoing craniotomy.

BACKGROUND: Monitoring the jugular venous oxygen saturation (SjVO2) and cerebral arteriovenous oxygen difference (AVDO2) is valuable in detecting cerebral ischemia. In the present study, we investigated the effect of mannitol on SjVO2 and AVDO2 in patients undergoing craniotomy. METHODS: We studied 25 ASA class II-III patients undergoing craniotomy. Anesthesia was induced with thiopental, fentanyl and vecuronium. Immediately after induction, a 16-gauge central venous catheter was placed in the internal jugular vein, ipsilateral to the lesion side with cephalic insertion and anchorage in the jugular bulb. Anesthesia was maintained with continuous infusion of fentanyl (10 micrograms/kg/h), 0.5-1% isoflurane in 60% oxygen (oxygen/air) and supplemental dose of vecuronium for muscle relaxation as needed. Samples of arterial and jugular venous blood were obtained for the measurements of SjVO2 and AVDO2 in the following time intervals: (1) normocapnia (PaCO2 38-40 mmHg); (2) hypocapnia (PaCO2 28-30 mmHg); and (3) 30 min after mannitol (0.5 g/kg) infusion. RESULTS: Hyperventilation resulted in a significant decrease in SjVO2 (96% patients) and increase in AVDO2 (88% patients). Hypocapnia followed by mannitol administration led to a further decrease and increase of SjVO2 and AVDO2 in 72% and 68% patients, respectively. CONCLUSIONS: Mannitol may produce a further reduction in SjVO2 accompanied by an increase in AVDO2, suggesting a reduction of cerebral blood flow (CBF) during hyperventilation. Therefore, it should be given cautiously in neurosurgical patients under hyperventilation.

Adult↗