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Biomedical subjects

Y H Lam

Publications and source records attributed to Y H Lam.

At least 73 records · Page 4Linked to original sources
PubMed1998

Second-trimester maternal serum alpha-fetoprotein and human chorionic gonadotrophin screening for Down's syndrome in Hong Kong.

Second-trimester maternal serum screening for fetal Down's syndrome is well established in many Western countries. Its usefulness and acceptability is unknown in the Asian countries. Between June 1994 and December 1996, we offered second-trimester serum AFP and hCG screening to pregnant women in Hong Kong who were less than 35 years old and without other risk factors for chromosome abnormalities. Each woman was assigned a risk of having a Down's syndrome term pregnancy by using a computer software program that took into account her age. weight, AFP and hCG MOMs. All those with a risk of one in 250 or greater were designated screen-positive, subject to the revision of gestation by ultrasound examination. 9,177 women with singleton pregnancies (93 per cent were Chinese) were screened. The uptake of screening was 75 per cent. 281 women (three per cent) were initially classified to be screen-positive. After revision of the gestation by ultrasound examination, 183 women (two per cent) were 'true' screen-positive and 164 (90 per cent) accepted the offer of amniocentesis. Eight of these pregnancies were affected by Down's syndrome and all the women elected pregnancy termination. The odds of being affected, given a positive screening result, were one in 23. Six Down's syndrome pregnancies were missed by screening programme. The detection rate was 57 per cent. The study showed that second-trimester serum screening for fetal Down's syndrome was feasible and accepted in the Hong Kong population.

Adult↗
PubMed1997

Laser-assisted removal of a foreign body impacted in the esophagus.

BACKGROUND AND OBJECTIVE: We reported the use of Holmium-YAG laser in the management of a foreign body impacted in the esophagus. STUDY DESIGN/PATIENTS AND METHODS: Esophagoscopy was performed on a man with a denture impacted in the esophagus. The denture was disimpacted into the stomach and fractured with Holmium-YAG laser before removal. RESULTS: The denture was successfully removed in three pieces without complications. CONCLUSION: Holmium-YAG laser can be used to fragment foreign bodies to aid in their removal.

Adult↗
PubMed1997

Second-trimester hydrops fetalis in pregnancies affected by homozygous alpha-thalassaemia-1.

Homozygous alpha-thalassaemia-1 is the commonest cause of hydrops fetalis in South-East Asia. Ultrasonographic features of hydrops fetalis were said to be evident only after 20 weeks of gestation. We studied 111 pregnancies at risk of homozygous alpha-thalassaemia-1 at 12-14 gestational weeks and 101 pregnancies at 17-18 weeks by abdominal ultrasound examination. Ultrasonographic features of hydrops fetalis were seen in 3 out of 44 pregnancies affected by homozygous alpha-thalassaemia-1 at 12-14 weeks [7 per cent; 95 per cent confidence interval (CI) 1-19 per cent] and in 7 out of 21 affected pregnancies at 17-18 weeks (33 per cent; 95 per cent CI 15-57 per cent). In conclusion, homozygous alpha-thalassaemia-1 can cause hydrops fetalis in the early second trimester. It should constitute one of the differential diagnoses in the work-up of second-trimester hydrops fetalis.

Diagnosis, Differential↗
PubMed1997

Prenatal diagnosis of haemoglobin Bart's disease by cordocentesis at 12-14 weeks' gestation.

Couples with alpha-thalassaemia-1 face a 25 per cent risk of having fetuses with haemoglobin (Hb) Bart's disease. Prenatal diagnosis is conventionally performed by DNA studies of chorionic villi or amniocytes obtained from chorionic villus biopsy or amniocentesis. DNA studies are expensive and time-consuming. We identified 11 affected pregnancies on abdominal ultrasound examination at 12-14 weeks when the placental thickness exceeded the mean plus 2 SD measurement for the gestational week and the cardiothoraic ratio was more than 0.5. Cordocentesis was then performed with a free hand technique. The procedures were successful in ten cases using a 26-gauge spinal needle with a 20-gauge introducer. Hb Bart's disease was confirmed in all cases by Hb electrophoresis. The procedure was unsuccessful in one case when a 22-gauge spinal needle was used. Hb study of fetal blood collected at abortion also confirmed Hb Bart's disease. In conclusion, ultrasound findings of concomitant placentomegaly and cardiomegaly at 12-14 weeks is highly specific of disease in pregnancies at risk of Hb Bart's disease. Cordocentesis and Hb study in pregnancies with these sonographic manifestations may be an alternative prenatal diagnostic approach. This diagnostic approach is of particular value in areas where resources for molecular studies are limited.

Cordocentesis↗
PubMed1997

Prevention of hypotension during spinal anaesthesia for caesarean section: ephedrine infusion versus fluid preload.

We compared the efficacy of prophylactic ephedrine infusion over fluid preloading in prevention of maternal hypotension during spinal anaesthesia for Caesarean section. Forty-six women undergoing elective Caesarean section at term were allocated randomly to receive either intravenous fluid preloading with Hartmann's solution 20 ml.kg-1 (fluid group) or prophylactic intravenous ephedrine 0.25 mg.kg-1 (ephedrine group). Moderate hypotension was defined as > or = 20% reduction in systolic blood pressure and severe hypotension as > or = 30% reduction in systolic blood pressure. Maternal uterine circulation was measured using Doppler ultrasound in 11 parturients before and after spinal anaesthesia. There was a lower incidence of severe hypotension in the ephedrine group compared with the fluid group (35% vs. 65%, p = 0.04), although the incidence of moderate hypotension was similar. Mean umbilical venous pH was higher in the ephedrine group than in the fluid group (7.33 vs. 7.29, p = 0.02) and the number of patients shivering was lower in the ephedrine group (2 vs. 9, p = 0.02). No difference was found between pre- and postspinal uterine artery pulsatility indices in either group. We conclude that prophylactic ephedrine infusion alone is at least as good as fluid preload alone in combating the hypotension associated with spinal anaesthesia for Caesarean section.

Anesthesia, Obstetrical↗
PubMed1997

Early ultrasound prediction of pregnancies affected by homozygous alpha-thalassaemia-1.

Homozygous alpha-thalassaemia-1 is conventionally diagnosed by invasive testing on all at-risk pregnancies. We evaluated the diagnostic efficacy of non-invasive abdominal ultrasonographic cardiothoracic ratio measurement in 62 pregnancies at 13-14 weeks and 75 pregnancies at 17-18 weeks. This performed better than placental thickness measurement. Using a cardiothoracic ratio cut-off level of > or = 0.5, 75 per cent of affected pregnancies were detected at 13-14 weeks and all cases were detected at 17-18 weeks. False-positive rates were 7 and 8 per cent, respectively. There was no false-positive diagnosis if the cardiothoracic ratio was > or = 0.53. With this approach, invasive procedures can be selectively performed and fewer pregnancies will be lost unnecessarily. The reduction in medical expenses is likely to be substantial.

False Positive Reactions↗
PubMed1997

The risk of alpha-thalassaemia in offspring of beta-thalassaemia carriers in Hong Kong.

Couples in whom one is heterozygous for alpha-thalassaemia-1 and the other is heterozygous for beta-thalassaemia are assumed not to be at risk of having offspring with homozygous alpha-thalassaemia-1 or homozygous beta-thalassaemia. We retrospectively reviewed the genetic outcome of 189 pregnancies of 178 couples in whom the partners were diagnosed to be discordant heterozygotes of alpha-thalassaemia and beta-thalassaemia on haematological tests. Zeta gene mapping was performed on 158 beta-thalassaemia carriers to diagnose the presence of co-existing alpha-thalassaemia-1. Eleven patients (7 per cent) were found to be compound alpha- and beta-thalassaemia heterozygotes. They accounted for 16 pregnancies, of which five were diagnosed to be affected by homozygous alpha-thalassaemia-1. Our results show that couples presumed to be discordant heterozygotes of alpha- and beta-thalassaemia on haematological testing are at risk of having offspring with homozygous alpha-thalassaemia-1 if the zeta gene mapping of the heterozygous beta-thalassaemia partner shows co-inheritance of alpha-thalassaemia-1. Prenatal diagnosis of homozygous alpha-thalassaemia-1 should be performed on these at-risk pregnancies.

Chromosome Mapping↗
PubMed1997

Second-trimester maternal urinary gonadotrophin peptide screening for fetal Down syndrome in Asian women.

Maternal urinary gonadotrophin peptide (UGP) was recently found to be elevated in second-trimester Down syndrome pregnancies. There is controversy about its screening efficacy. Data in the Asian population are scanty. We measured the UGP levels in 29 Down syndrome pregnancies and 297 controls and expressed them as a ratio of the urine creatinine concentration. Median UGP MOM was elevated to 3.44 (95 per cent confidence interval 1.99-5.13) in cases, compared with controls. UGP values were widely scattered in cases and controls with extensive overlap such that only 35 per cent of Down syndrome cases were expected to be detected at a 5 per cent false-positive rate. The data of the present study and previous reports show that there is a wide variability of gestation-specific UGP median values. UGP alone does not appear to be an effective screening marker for fetal Down syndrome.

Adult↗
PubMed1997

Limb reduction defects in fetuses with homozygous alpha-thalassaemia-1.

Limb reduction defect is a rare event. Its exact pathogenesis is unknown. We retrospectively reviewed the outcome of 130 fetuses affected by homozygous alpha-thalassaemia-1 and found that 11 of them (8 per cent; 95 per cent confidence interval: 4-13 per cent) had terminal transverse limb reduction defects. Chromosome study was available in ten fetuses with limb defects and the results were normal. We postulate that the strong association between homozygous alpha-thalassaemia-1 and limb reduction is related to the hypoxic insult in early gestation. This may be the final common pathway in the pathogenesis of other forms of limb reduction defects.

Female↗
PubMed1996

High prevalence of Helicobacter pylori infection in duodenal ulcer perforations not caused by non-steroidal anti-inflammatory drugs.

There has been controversy regarding the relationship between Helicobacter pylori and perforated peptic ulcer, which is known to have a high recurrence rate if only simple patch repair is performed. The aim of this study was to evaluate the association between H. pylori infection and intake of non-steroidal anti-inflammatory drugs (NSAIDs) in patients with perforated duodenal ulcers. Of the 73 patients recruited over a 16-month period, 51 (70 per cent) had evidence of H. pylori infection by intraoperative gastroscopy and antral biopsies. The infection rate rose to 80 per cent if NSAID users were excluded. The H. pylori-infected group was significantly younger (mean 47.6 versus 62.5 years), with a male preponderance (49 of 51 versus 14 of 22 patients), and had significantly less NSAID consumption (three of 51 versus ten of 22) and more prolonged dyspepsia (40 of 51 versus ten of 22), compared with H. pylori-negative patients. H. pylori infection probably plays an important role in the causation of non-NSAID-induced duodenal ulcer perforation. Whether eradication of the bacteria can alleviate the strong ulcer diathesis in this subgroup of patients is unknown.

Aged↗
PubMed1996

Fetal cerebral Doppler studies as a predictor of perinatal outcome and subsequent neurologic handicap.

OBJECTIVE: To study the use of middle cerebral arterial Doppler findings in a group of high-risk fetuses as a predictor of adverse perinatal outcome, including subsequent neurologic handicap. METHODS: A group of very high-risk fetuses was recruited over a 2-year period for study. Weekly fetal biometries and Doppler studies of the umbilical artery and middle cerebral arteries were carried out until delivery. Main outcome indices analyzed included birth weight ratio (ratio of observed birth weight to mean birth weight for gestation), days of ventilator requirement, neonatal intracranial hemorrhage or periventricular leukomalacia, necrotizing enterocolitis, and follow-up data on major neurologic handicap and death. RESULTS: Seventy-four patients were recruited. One hundred thirty-four sets of examinations were made and prospective follow-up data were available for up to 2 years. The ratio of the umbilical and middle cerebral arterial resistance index was found to be inversely proportional to the birth weight ratio. Fetuses who had a high prenatal umbilical-cerebral Doppler ratio had significantly lower birth weight ratios than those with normal findings (0.72 versus 0.92; P < .001). The ratio was a more sensitive marker for growth restriction (sensitivity 78%) than conventional fetal biometry and umbilical arterial systolic-diastolic ratio. However, fetuses with high ratios did not have higher incidences of perinatal complications or subsequent neurologic handicap. CONCLUSION: Prenatal cerebral vasodilation is a sensitive marker for growth restriction and it seems to be a physiologic response to hypoxia. Fetuses with intrauterine cerebral vasodilation do not have increased risk for subsequent gross neurologic damage.

Adult↗
PubMed1996

Mesh hernioplasty using a stapler.

BACKGROUND: The recent development of laparoscopic hernioplasty has evoked extensive re-examination of the safety and effectiveness of using synthetic mesh materials in hernia surgery. We have investigated the efficacy of anterior stapling mesh repair in the treatment of inguinal hernia. METHODS: From July 1993 to June 1994, a modified open mesh hernioplasty using staples for anchorage has been performed in 127 patients. RESULTS: The mean age of patients was 61.4 +/- 13.0 years. Over 90% of them were operated on under local anaesthesia. The operation time ranged from 30 to 95 min with a median of 39 min. Only sixteen patients (12.6%) required postoperative parenteral analgesics and the median time for resuming daily activities was 7 days. Apart from two patients with reactionary haemorrhage, there was no other significant complication observed. Only one recurrence was encountered over the 26-month median follow-up period. CONCLUSIONS: We conclude that the modified mesh hernia repair with a stapling device is a feasible, inexpensive and safe procedure that is well tolerated under local anaesthesia by most patients.

Adult↗
PubMed1996

An overview of laparoscopic and thoracoscopic vagotomy.

The development of laparoscopic surgery in the past few years has been truly explosive. Techniques developed in laparoscopic cholecystectomy are also applied to other operations in the abdomen. Vagotomy can be performed expediently laparoscopically. However, the advent of effective ulcer drugs has decreased the demand for elective surgery, especially since ulcer disease can now be cured with a short course of anti-Helicobacter treatment. We review the role of laparoscopic and thoracoscopic vagotomy in the light of these developments.

Humans↗
PubMed1995

Laparoscopic repair of perforated peptic ulcer.

A total of 100 consecutive patients with perforated duodenal or juxtapyloric ulcers were treated by: laparotomy and omental patch repair (group 1, n = 44); laparoscopic suture patch repair (group 2, n = 35); and laparoscopic fibrin glue repair (group 3, n = 21). The three groups were comparable in Acute Physiology And Chronic Health Evaluation II score and in other known operative risk factors such as shock on admission, delayed presentation and associated underlying medical illness. Operative mortality and morbidity data were identical in all groups. The mean operating time was 52.1, 101.3 and 61.1 min respectively in the three groups (group 1 versus group 2, group 2 versus group 3, and group 1 versus groups 2 and 3 combined, P < 0.001). The median number of doses of analgesia required after operation was 4, 3 and 1 respectively (group 1 versus groups 2 and 3, P < 0.05). Conversion to laparotomy was necessary in six patients in group 2 and in one in group 3 (P not significant). The median hospital stay was 5 days in all three groups. Patients who underwent laparoscopic repair of perforated peptic ulcer required fewer postoperative doses of analgesia than those who had open repair. Laparoscopic glue repair has the additional advantage over laparoscopic suture of being technically simpler; it also takes less time to perform.

Aged↗