Biomedical subjects

M W Yang

Publications and source records attributed to M W Yang.

At least 37 records · Page 2Linked to original sources

PubMed1995

Continuous, on-line, real-time spectral analysis of SAP signals during cardiopulmonary bypass.

We communicated the application of continuous, on-line, real-time power spectral analysis of systemic arterial pressure (SAP) signals during cardiopulmonary bypass when the heart was functionally but reversibly disconnected from the blood vessels. Based on observations from 15 cases of successfully completed coronary artery bypass grafting procedures, we found that the very low (0.00-0.08 Hz), low (0.08-0.15 Hz)-, high (0.15-0.25 Hz)-, and very high (0.80-1.60 Hz) frequency components of SAP signals exhibited differential changes before, during, and after cardiopulmonary bypass. In particular, the very low-frequency component, which purportedly represents the contribution of vasomotor activity to SAP, presented only a mild decrease in power during hypothermic cardioplegia. Interestingly, the total peripheral resistance also manifested only a slight reduction during the same period. On the other hand, the low-, high-, and very high frequency components were essentially eliminated. These results unveiled an active role for the blood vessels in the maintenance of SAP during cardiopulmonary bypass, possibly as a result of a maintained vasomotor tone as reflected by the sustained very low frequency component of the SAP signals.

Aged↗

PubMed1995

Power spectral analysis of systemic arterial pressure signals during open heart surgery.

BACKGROUND: The close relationship between the balance of sympathetic and parasympathetic tones and the results of power spectral analysis (PSA) of systemic arterial pressure (SAP) has been suggested recently. The purpose of this study was to further describe the changes of balance between the two autonomic nervous components during open heart surgery for coronary arterial disease (CAD) or valvular heart disease (VHD) with the PSA technique of SAP. METHODS: By relaying the SAP signals to a personal computer utilizing a power spectral analysis algorithm, radial arterial pressure signals of 27 patients (11 with CAD for coronary artrial bypass graft, as CAD groups; 16 with VHD, as VHD group, including 8 for aortic valve replacement and 8 for mitral valve replacement) during open heart surgery were monitored in a continuous, on-line and real-time manner. On-line power spectral analysis was performed according to the five different stages of the operation. RESULTS: Power density tended to increase in the high frequency (HF) band during the ventilator-supported stages of the open heart procedures, i.e., the pre-cardiopulmonary bypass (CPB) and the off-CPB periods. The power density in other frequency bands during the whole course of general anesthesia otherwise decreased significantly, with the lowest values occurring during CPB. The power density in very low frequency (VLF) band was much higher than in other bands during CPB, and became the major component of total power density in this period. CONCLUSIONS: The balance between sympathetic and parasympathetic components of autonomic nervous system changes rapidly during open heart surgery and needs careful monitoring. By utilizing PSA of SAP, mathematical error might be an obstacle of using LF:HF ratio as an index of autonomic balance during the CPB period when the HF density approaches zero.

Aged↗

PubMed1994

Effects of zaizhang-I, a traditional Chinese herbal medicine, on hematopoietic recovery from radiation injury in mice.

Effects of Zaizhang-I (ZZ-I) on the recovery of hemopoietic systems from radiation injury were investigated. Mice, irradiated with 6.0 Gy-rays, were injected i.p. once daily for 7 consecutive days with either ZZ-I or saline (0.01 ml/g body wt.). The experiments showed that ZZ-I significantly promoted the recovery of not only peripheral WBC, BMC, CFU-S and CFU-GM but also the abnormal femur micro-vessel system such as blood vessels and sinus ectasia, hyperemia and hemorrhage etc. These results suggest that ZZ-I could accelerate hemopoietic recovery from radiation injury in mice by stimulating hemopoietic stem cells and improving hemopoietic inductive microenvironment (HIM).

Animals↗

PubMed1994

The interaction of diazepam with vecuronium: a clinical study.

BACKGROUND: Diazepam, known to possess myorelaxation property, has been widely used clinically to control muscular rigidity and spasticity. The interactions of diazepam with neuromuscular blocking agents have been extensively studied, yet the results reported are somewhat controversial and inconclusive. METHODS: The interaction of diazepam with one of the neuromuscular blocking agents, vecuronium, was studied in 20 ASA I-II patients undergoing elective surgery. They were randomly assigned to two groups with ten in each group. Anesthesia was induced with fentanyl, thiopental and vecuronium and maintained with 1% halothane and 70% N2O in O2. The experimental group received diazepam (0.2 mg/kg) 3 minutes prior to vecuronium (0.1 mg/kg) during induction while the control group received vecuronium (0.1 mg/kg) straight without diazepam. Control records of the integrated electromyography showed the response to train-of-four supramaximal stimulation by a Datex Relaxograph during induction. In no time when the first twitch (T1) recovered to 25% of the control, it was topped up again with another intraoperative dose of vecuronium (0.025 mg/kg). From the derived data, the following parameters were calculated and analysed: (1) onset time T10 (the time from the end of injection of vecuronium during induction to depression of T1 to 10% of control twitch height); (2) duration time T25 (the time from administering vecuronium during induction to the time when T1 recovered to 25% of the original twitch height); (3) topup time T25-25 (the time from administering the top dose of vecuronium to the time when T1 returned to 25% of control twitch height again) and (4) recovery time T25-50 (the time of recovery of T1 from 25% to 50% of the control twitch height at the end of the operation). RESULTS: Significant differences between both groups were found in T10 (221.8 +/- 62.2 vs 135.4 +/- 23.3 sec, p < 0.01) and T25 (41.9 +/- 10.2 vs 50.6 +/- 9.4 min, p < 0.05). The results of T25-25 and T25-50 did not differ much (26.6 +/- 6.9 vs 29.3 +/- 4.4 min, p > 0.05 and 15.0 +/- 8.9 vs 16.9 +/- 8.7 min, p > 0.05 respectively). CONCLUSIONS: The administration of diazepam (0.2 mg/kg) three minutes prior to vecuronium (0.1 mg/kg) during induction may hasten the onset of vecuronium and prolong its duration of action.

Aged↗

PubMed1994

Early detection of the tip position and complication of the intra-aortic balloon pump catheter by perioperative transesophageal echocardiography.

BACKGROUND: Intraoperative verification of the precise balloon position of intra-aortic balloon pump(IABP) is necessary and important. We introduced transesophageal echocardiogram (TEE) as one of our routine intraoperative image monitor to accomplish this identification fluently, conveniently and also precisely. METHODS: 56 patients who needed the hemodynamic support when weaning the cardiopulmonary bypass were introduced to receive IABP and the balloon position was verified by TEE. To confirm the accurate location, the position of balloon tip was rechecked with postoperative portable chest x-ray. RESULTS: The balloon tip was attempted to locate in the proximal descending aorta, which was verified via TEE to be successful in 98.1% of patients by postoperative chest x-ray. Five (8.9%) patients failed to pass the balloon catheter at the first time due to high arterial resistance. One iatrogenic aortic dissection (1.8%) and one case in the wrong lumen (1.8%) were detected by TEE. No early death was contributed to IABP insertion. CONCLUSIONS: The application of TEE in the perioperative period helps not only detect IABP complication early but also verify of balloon catheter position quickly. It can replace the conventional role of fluorography.

Catheters, Indwelling↗

PubMed1993

A comparison between vecuronium and atracurium in myasthenia gravis.

We evaluated the effect of vecuronium bromide and atracurium besylate on the train-of-four response in the management of muscle relaxation in 20 patients with myasthenia gravis (MG) who were undergoing thymectomy. We confirmed the safe use of these two non-depolarizing muscle relaxants in MG patients. Vecuronium (0.04 mg.kg-1) demonstrated a lesser clinical duration than did atracurium (0.2 mg.kg-1) (38 +/- 19 vs 50 +/- 21 min, mean +/- s.e.mean). The recovery time for vecuronium patients was shorter than that for atracurium patients (22 +/- 18 vs 38 +/- 18 min), but the time until onset of neuromuscular blockade was longer with vecuronium (246 +/- 105 vs 107 +/- 103 s). During spontaneous recovery from neuromuscular relaxation, at T1/C of 25% and 100%, the train-of-four fade with vecuronium was significantly greater than that with atracurium (0.04 +/- 0.02, 0.16 +/- 0.03 vs 0.17 +/- 0.01, 0.83 +/- 0.03), suggesting that vecuronium had a greater prejunctional effect than did atracurium.

Adult↗

PubMed1993

The use of transesophageal echocardiography to evaluate the effectiveness of patent ductus arteriosus ligation.

The ligation of patent ductus arteriosus (PDA) is a comparatively easy operation, but some complications are possible. The most common complication is incomplete ligation of the PDA; others include inadvertent ligation of the descending aorta or left pulmonary artery, transient rise in systemic blood pressure and increased left ventricular afterload, and acute right heart failure due to pulmonary hypertension. The completeness of the PDA ligation is usually determined only by the operating physician's experience, including the use of an esophageal stethoscope or a finger on the lesion to feel for vibration. These methods sometimes fail to detect an incomplete ligation. With transesophageal echocardiography (TEE), we have monitored the entire course of the PDA ligation directly without interrupting the surgical procedure, and precisely determined the completeness of the ligation. We also expect that TEE will enable us to avoid other complications as well.

Adolescent↗

PubMed1992

Thromboelastogram fails to predict postoperative hemorrhage in cardiac patients.

To determine the clinical usefulness of the thromboelastogram in the prediction of postoperative hemorrhage in cardiac patients, we related the results of routine coagulation tests (RCTs) and thromboelastography with the amount of chest tube drainage postoperatively in 101 patients requiring cardiopulmonary bypass. Our data indicated that there was no correlation between RCT results and thromboelastographic variables. No single variable of RCTs and thromboelastography correlated well with the amount of chest tube drainage postoperatively. Before the onset of cardiopulmonary bypass, the most frequent abnormalities detected by thromboelastograms were fibrinolysis and hypocoagulability resulting from factor deficiency. Hypercoagulability detected by thromboelastograms occurred in 13% of patients after cardiopulmonary bypass and usually was not detected by RCTs. The incidence of false-negative thromboelastograms and RCT results in patients who had excessive hemorrhage of unknown cause was 46% and 52%, respectively. The incidence of fibrinolysis as detected by thromboelastograms was similar before and after bypass, but only 2 of the 18 patients with fibrinolysis had excessive hemorrhage postoperatively. Our results indicate that neither RCTs nor thromboelastography predicts the likelihood of excessive hemorrhage in patients after cardiopulmonary bypass. The thromboelastographic results should be interpreted cautiously because of the high rate of unreliable results.

Blood Coagulation Tests↗

PubMed1992

[Mannitol reduces plasma hydrogen peroxide free radical in patients undergoing coronary artery bypass graft surgery].

During the procedure of coronary artery bypass graft surgery (CABG), the release of free oxygen radicals as a result of ischemia and reperfusion which plants the seeds of post-operative low cardiac output and arrhythmias has grave consequence on the reestablishment of cardiac function. A variety of chemical agents such as mannitol, allopurinol, catalase (Q-10) and superoxide dismutase (SOD) has proved to be considerably effective to improve the myocardial necrosis following ischemia and reperfusion. In this study we chose mannitol (0.2 gm/kg) as the free oxygen radicals scavenger and utilized mass spectrophotometric method to detect the variation of concentration of [H2O2], a by-product of free oxygen radical, in an attempt to evaluate the efficacy of mannitol in this regard in patients undergoing CABG. Patients were divided into experimental group (n = 19) and control group (n = 20). In the experimental group the concentration of [H2O2] changed from 61 +/- 24 microM/L pre-operatively to 77 +/- 18 microM/L post-operatively as against 75 +/- 31 microM/L and 99 +/- 31 microM/L respectively in the control group. In comparison, only the change in experimental group was statistically significant (p less than 0.05). We confirmed that mannitol functions considerably as a free oxygen radical scavenger since it reduces the production of [H2O2] in patients undergoing CABG.

Aged↗

PubMed1992

Interpleural administration of bupivacaine for postoperative analgesia after thoracotomy in patients with patent ductus arteriosus.

Interpleural analgesia for postoperative pain with bupivacaine 0.25%, 0.375% and 0.5% at dosage of 1.5 mg/kg was evaluated in three randomized groups (A, B and C) of 22 children having triple ligation for patent ductus arteriosus (PDA). Complete pain relief was obtained within 30 min irrespective of the concentration of bupivacaine. The duration of pain relief significantly varied with the concentrations of the drug used, respectively 5.02 +/- 0.4 h, 6.88 +/- 0.7 h and 8.24 +/- 1.08 h (mean +/- SD) for 0.25%, 0.375% and 0.5% bupivacaine (p less than 0.05). No side effects were observed and no other supplemented narcotics were given. We concluded that 0.5% bupivacaine at the dose of 1.5 mg/kg was effective in postoperative pain relief after thoracotomy in patients undergoing PDA ligation surgery.

Adolescent↗

PubMed1991

Influence of controlled hypotension by adenosine triphosphate or nitroglycerin on the neuromuscular blocking effect of atracurium in dogs.

The neuromuscular blocking effect of atracurium under the influence of controlled hypotension by adenosine triphosphate (ATP) or nitroglycerin (NTG) was studied in mongrel dogs under halothane anesthesia. Under hypotensive state (60 +/- 5 mmHg) elicited by ATP (0.5 mg/kg/min) or NTG (1 microgram/kg/min), the neuromuscular blockade produced by atracurium (30 micrograms/kg, i.v.) was significantly potentiated and prolonged. The maximal depression of twitch contraction of the gastrocnemius-soleus muscle increased from 10 +/- 3% to 36 +/- 10% (ATP group) and 56.0 +/- 2.4% (NTG group), while the duration of neuromuscular blockade was prolonged from 663 +/- 96 s to 1060 +/- 277 s (ATP group), and 1375 +/- 441 s (NTG group). The potentiation and prolongation of neuromuscular blockade by atracurium was still apparent upon reversal of the hypotensive effect of ATP, but not of NTG, by dopamine infusion. We suggest that ATP may prolong and augment the effect of atracurium by reducing the presynaptic release of acetylcholine at the neuromuscular junction.

Adenosine Triphosphate↗

PubMed1991

Acute normovolemic hemodilution in coronary artery bypass graft surgery.

Twenty patients undergoing coronary artery bypass graft (CABG) surgery in April through May, 1990 in our hospital were included in this study to evaluate the merits and practicability of autologous blood transfusion. About 1,000 ml of arterial blood were collected via a radial arterial line and stored in a plastic bag containing CPD solution immediately after induction of anesthesia. Colloid or crystalloid solution was used to replace the volume deficit after the blood sampling. At the end of cardiopulmonary bypass and after adequate reversal of heparinization by protamine, the blood previously sampled was re-transfused to the patient via a peripheral venous line. Thirty patients undergoing CABG surgery, who did not receive autologous blood transfusion from February to June, 1990 save April and May were assigned as control. Comparison of the data between the two groups was made using the Student's t-test. It was found that the intraoperative acute normovolemic hemodilution could lower the hematocrit by approximately 12%. Packed red blood cells (PRBC) given intraoperatively in the autologous group was only 2.0 +/- 0.4 units whereas it was 5.3 +/- 0.7 units in the control group (p less than 0.001). Fresh frozen plasma (FFP) given intraoperatively in the autologous group was only 1.8 +/- 0.5 units whereas it was 6.6 +/- 0.7 units in the control group (p less than 0.001). The amount of platelets given intraoperatively in the autologous group was 1.9 +/- 1.0 units against 9.3 +/- 1.4 units in the control group (p less than 0.001). Thus, acute normovolemic hemodilution in CABG surgery decreased intraoperative requirement of bank blood components including PRBC, FFP and platelets.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Platelets↗

PubMed1988