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Biomedical subjects

A M Lam

Publications and source records attributed to A M Lam.

At least 37 records · Page 2Linked to original sources
PubMed2000

Femoral venous flow during laparoscopic gynecologic surgery.

The lower-limb venous return, assessed by the peak systolic venous velocities (PSVV) of the left common femoral vein, was recorded at different stages of operation for five patients undergoing major gynecologic operative laparoscopy. The average baseline PSVV was 23.1 cm/s. After positioning the patient in the Trendelenburg position, the PSVV increased to an average of 31.5 cm/s; this was a statistically significant increase. Creation of the pneumoperitoneum changed the waveform from a normal phasic pattern to a dampened, continuous, monophasic waveform. The average PSVV was reduced to 15.9 cm/s; this dampening was statistically significant. Further dampening was evident 1 hour intraoperatively, and the flow became intermittent, with cycles of dampened flow followed by periods of absent flow; these changes in PSVV were not statistically significant. Calf compressors did not increase the femoral PSVV at the beginning of operation, nor at I hour intraoperatively; the decrease was not statistically significant. After release of the pneumoperitoneum, the baseline waveform pattern and velocity returned. The Trendelenburg position used for gynecologic operative laparoscopy was associated with a statistically significant increase in the lower-limb PSVV. This increase did not fully counteract the dampening effect of a pneumoperitoneum on lower-limb PSVV. The authors' study did not support the benefit previously reported on the use of pneumatic calf compressors. The authors therefore recommend continuing the practice of antithrombotic measures for patients undergoing gynecologic operative laparoscopy.

Adult↗
PubMed1999

Stabilized plasmid-lipid particles: factors influencing plasmid entrapment and transfection properties.

Previous work has shown that plasmid DNA can be encapsulated in small 'stabilized plasmid-lipid particles' (SPLP) composed of 1, 2-dioleyl-3-phosphatidylethanolamine (DOPE), the cationic lipid N, N-dioleyl-N,N-dimethylammonium chloride (DODAC) and poly(ethylene glycol) (PEG) conjugated ceramides (PEG-Cer), employing a detergent dialysis procedure. These SPLP have potential as vectors for in vivo gene therapy. This study is aimed at characterizing the influence of the cationic lipid and PEG-Cer species on SPLP formation and in vitro transfection properties. It is shown that the transfection potency of SPLP is sensitive to the cationic lipid species employed, the size of the PEG polymer incorporated in the PEG-ceramide and the length of the acyl chain contained in the ceramide anchor. With regard to the influence of cationic lipid, the transfection levels achieved were highest for SPLP containing N-[2, 3-(dioleyloxy)propyl]-N,N-dimethyl-N-cyanomethylammonium chloride (DODMA-AN) and lowest for SPLP containing 3-beta-[N-(N', N'-dimethylaminoethyl)carbamoyl]-cholesterol (DC-CHOL), according to the series DODMA-AN>N-[2,3-(dioleyloxy)propyl]-N,N, N-trimethylammonium chloride (DOTMA)>DODAC>N,N-distearyl-N, N-dimethylammonium chloride (DSDAC)>DC-CHOL. Incorporation of short (PEG(750)) PEG polymers in the PEG-ceramide components resulted in modest improvements in transfection levels over PEG(2000) and PEG(5000) polymers, however variation of the length of the acyl chain contained in the hydrophobic ceramide anchor from octanoyl (PEG-CerC(8)) to myristoyl (PEG-CerC(14)) to arachidoyl (PEG-CerC(20)) had the most dramatic effects. Transfection levels achieved for SPLP containing PEG-CerC(8) were substantially larger than observed for SPLP containing PEG-CerC(14) or PEG-CerC(20), consistent with a requirement for the PEG-ceramide to dissociate from the SPLP surface for maximum transfection potency. It is also shown that the ability of SPLP to be accumulated into cells is a dominant factor influencing transfection potency, and that the transfection potency of SPLP that are accumulated is at least equivalent to that of cationic lipid-plasmid DNA complexes.

Cell Line↗
PubMed1999

Cerebrospinal fluid creatine kinase-BB isoenzyme activity and outcome after subarachnoid hemorrhage.

BACKGROUND: The brain is rich in creatine kinase-BB isoenzyme activity (CK-BB), which is not normally present in cerebrospinal fluid (CSF). Results of previous studies have shown that CK-BB can be detected in the CSF of patients with aneurysmal subarachnoid hemorrhage (SAH), but whether CK-BB levels correlate with patients' neurologic outcomes is unknown. OBJECTIVE: To evaluate the relationship between CSF CK-BB level and outcome after SAH. DESIGN: Prospective observational cohort. SETTING: University-affiliated tertiary care center. PATIENTS: Convenience sample of 30 patients seen for cerebral aneurysm clipping. INTERVENTIONS: We sampled and assayed CSF for CK isoenzymes a median of 3 days after SAH in 27 patients, and at the time of unruptured aneurysm clipping in 3 patients. MAIN OUTCOME MEASURES: Without knowledge of CK results, we assigned the Glasgow Outcome Scale score early (approximately 1 week) and late (approximately 2 months) after surgery. RESULTS: Higher CSF CK-BB levels were associated with higher Hunt and Hess grades at hospital admission (Spearman rank correlation, p = 0.69; P<.001), lower Glasgow Coma Scale scores at hospital admission (p = -0.72; P<.001), and worse early outcomes on the Glasgow Outcome Scale (p = -0.64; P<.001). For patients with a favorable early outcome (Glasgow Outcome Scale score, 3-5), all CK-BB levels were less than 40 U/L. With a cutoff value of 40 U/L, CK-BB had a sensitivity of 70% and a specificity of 100% for predicting unfavorable early outcome (Glasgow Outcome Scale score, 1-2). Having a CK-BB level greater than 40 U/L increased the chance of an unfavorable early outcome, from 33% (previous probability) to 100%, whereas a CK-BB level of 40 U/L or less decreased it to 13%. Similar findings were obtained when considering late outcomes. CONCLUSION: The level of CSF CK-BB may help predict neurologic outcome after SAH.

Adult↗
PubMed1999

Craniotomy procedures are associated with less analgesic requirements than other surgical procedures.

UNLABELLED: The conventional wisdom that neurosurgical patients experience minimal postoperative pain and require little analgesia has been challenged. To address this, we reviewed our anesthesia and postanesthesia care unit (PACU) records for 1995 and compared pain management in patients undergoing major intracranial and selected extracranial procedures. We recorded patient weight, operative time, time in the PACU, intraoperative and postoperative opioid use, PACU pain scores, and level of consciousness in patients who had undergone open fixation of mandible or maxilla (Group E), clipping of aneurysms or excision of tumors (Group I), or lumbar laminectomy (Group L). Group I (n = 78) patients received less fentanyl in the operating room (0.016 microg x kg(-1) x min(-1) versus 0.023 microg x kg(-1) x min(-1) for Group E [n = 134] and 0.023 microg x kg(-1) x min(-1) for Group L [n = 21]; P < 0.05), received less morphine in the PACU (0.0004 vs 0.0013 vs 0.0015 mg kg(-1) x min(-1); P < 0.005), reported lower pain scores (0.76 vs 2.5 vs 2.4; P < 0.05), and spent less time in the PACU (89.5 vs 109 vs 105 min; P < 0.05) than Group E or L patients. Our results were similar when only patients with Glasgow Coma Scale scores > or = 14 were used in a subset analysis. We conclude that patients suffer less pain and use fewer opioids in the PACU after intracranial surgery than after facial reconstruction or lumbar laminectomy. Our results confirm that the average craniotomy patient has less postoperative pain than patients who undergo other surgical procedures, although patients who undergo frontal craniotomy may require more aggressive pain management. IMPLICATIONS: This study compares the pain report and analgesic use in patients after intracranial versus extracranial surgery. The results confirm the commonly held but recently challenged belief that neurosurgery patients suffer less pain postoperatively than other patients. In this study, we found that most patients report minimal pain after intracranial surgery but that a small subset of patients, many of whom have undergone frontal craniotomies, require aggressive treatment of postoperative pain.

Analgesics↗
PubMed1999

Surgical management of vaginal agenesis.

Vaginal agenesis is a rare anomaly that may result from a variety of different underlying diagnoses. The most important aspects of the surgical management of this condition are: correct diagnosis of both the underlying abnormality and its anatomy, documentation of any associated renal or skeletal anomalies, and proper psychological preparation of the young woman for any anticipated corrective surgery. Over the years, there have been many different techniques devised in an attempt to provide these women with a functioning vagina that approximates normal anatomy. The purpose of this article is to review the surgical options for the management of this anomaly.

Colon, Sigmoid↗
PubMed1999

Home within 24 hours of laparoscopic hysterectomy.

We assessed the feasibility of safe discharge home within 24 hours following laparoscopic hysterectomy in 30 patients who met the inclusion criteria and consented to be enrolled in the study group. Patients were admitted on the day of their surgery with the expectation of discharge within 24 hours. Appropriate home nursing follow-up and phone contact by the surgical team were organized preoperatively. Inclusion criteria were: age 30-65 years, absence of any major medical history that would require prolonged hospitalization, availability of home support for the first 48 hours after discharge and presence of a working telephone line and an address within the area of the Community Home Nursing service. All 30 operative procedures were completed without incident. Six patients underwent total laparoscopic hysterectomy (TLH) (all the procedures of hysterectomy being performed laparoscopically including the suturing of uterine arteries, colpotomy and closure of the vaginal vault. The uterus was removed vaginally) and 24 patients underwent laparoscopic hysterectomy (LH) (this techniques differs from TLH in that the colpotomy was performed laparoscopically but the uterosacral ligaments were divided vaginally and the vault also was closed vaginally after the uterus was removed vaginally). The average operating time was 115 minutes (range 85-150 minutes) and the average blood loss was 97 mL (20-250 mL). There were no intraoperative complications, no requirement for transfusion and no readmission to hospital for any of the patients in the study. Postoperative complications were minor (umbilical cellulitis (1), intestinal colic (1)) and both were treated with resolution of the symptoms. Ninety per cent of patients in the study were discharged within 24 hours of their surgery, the average duration of stay being 22.9 hours (20-24 hours). Three patients were not fit for discharge at 24 hours postoperatively due to general lethargy, migraine and nausea; their average discharge time was 53.5 hours. The study showed that laparoscopic hysterectomy can be associated with a reduction in length of in-patient stay compared to traditional laparotomy. Furthermore this reduction could be safely reduced to 24 hours following laparoscopic hysterectomy. There was also an associated cost saving in terms of inpatient bed days. Patient satisfaction with this protocol was high in this selected and motivated group.

Adult↗
PubMed1998

Accuracy of continuous jugular bulb oximetry in the intensive care unit.

OBJECTIVE: To address the accuracy of a bedside jugular bulb oxygen saturation (SjO2) catheter monitor (Baxter-Edwards, Santa Ana, CA) versus in vitro co-oximetry measurements in the intensive care unit (ICU). METHODS: By prospective protocol, we compared blood gas measurements with simultaneously recorded continuous bedside oximetric monitor values for 31 ICU patients with traumatic brain injury undergoing jugular bulb catheter monitoring. For suboptimal fiberoptic light signal quality indices, the catheter was repositioned, flushed, or both before drawing the sample for in vitro measurement. Laboratory and bedside monitor data were examined for association using the chi2 and paired t tests and a linear regression model. RESULTS: We assessed 195 samples (median, 5 per patient; range, 1-14) who were monitored an average of 3.4 (range, 1-6) days. The in vivo monitor (range, 32-94%) and in vitro co-oximetry (range, 38-93%) values had acceptable correlation (y = 0.94x + 4.4, r2 = 0.80). For bedside monitor detection of jugular bulb desaturation (SjO2 < 50% for 10 min), the kappa statistic was 0.35, the sensitivity was 45 to 50%, and the specificity was 98 to 100%. CONCLUSION: Continuous ICU SjO2 monitoring correlates significantly with in vitro values, but less so than previously described during intracranial surgery. Although sensitivity of the bedside monitor to detect confirmed desaturations remains an issue, the high specificity indicates that it is less of a concern that patients may be misdiagnosed as having desaturations resulting in unnecessary interventions. Nonetheless, suspected jugular bulb desaturation should be verified before taking therapeutic actions.

Adolescent↗
PubMed1998

Methods of creating pneumoperitoneum: a review of techniques and complications.

The existence of numerous techniques for the creation of pneumoperitoneum at laparoscopy indicates that none have been proven totally efficacious or complication free. These methods include the standard technique of insufflation after insertion of the Veress needle via the umbilicus or less commonly via the transfundal or transforniceal routes, open laparoscopy involving dissection through the linea alba and opening of the peritoneum under direct vision, and direct trocar insertion as well as variations on these techniques. After reviewing the methods available and surveying the existing data concerning the rates of failure and complications, we conclude that no single technique can claim to be overwhelmingly superior, and that laparoscopists should, therefore, acquaint themselves with at least two of these techniques. Finally, we recommend a large-scale combined survey by the colleges of obstetricians and gynecologists and surgeons on rates of failure and complications of the varied approaches of abdominal entry for laparoscopy.

Humans↗
PubMed1998

The safety of laparoscopic treatment for ovarian dermoid tumours.

Whilst laparoscopic surgery has largely replaced laparotomy as the standard surgical option for the management of benign ovarian cysts, concern remains regarding the safety of laparoscopy for benign cystic teratomas. This is based on a higher rate of cyst content spillage compared to laparotomy and the known sequelae of chemical peritonitis and granuloma formation. We present 18 cases of laparoscopic dermoid cystectomy with recommendations for specimen removal from the peritoneal cavity. Our findings together with evidence from the literature confirms the safety of laparoscopy for the treatment of ovarian dermoid cysts.

Adolescent↗
PubMed1998

Neuroprotective effects of NPS 846, a novel N-methyl-D-aspartate receptor antagonist, after closed head trauma in rats.

OBJECT: The authors sought to determine whether 3,3-bis (3-fluorophenyl) propylamine (NPS 846), a novel noncompetitive N-methyl-D-aspartate receptor antagonist, alters outcome after closed head trauma in rats. METHODS: The experimental variables were: presence or absence of closed head trauma, treatment with NPS 846 or no treatment, and time at which the rats were killed (24 or 48 hours). The NPS 846 (1 mg/kg) was administered intraperitoneally at 1 and 3 hours after closed head trauma or sham operation. Outcome measures were the neurological severity score (NSS), ischemic tissue volume, hemorrhagic necrosis volume, and specific gravity, water content, and concentrations of calcium, sodium, potassium, and magnesium in brain tissue. The following closed head trauma-induced changes in the injured hemisphere (expressed as the mean +/- the standard deviation) were reversed by NPS 846: decreased specific gravity of 1.035 +/- 0.006 at 24 hours was increased to 1.042 +/- 0.004; the decreased potassium level of 0.583 +/- 0.231 mg/L at 48 hours and at 24 hours was increased to 2.442 +/- 0.860 mg/L; the increased water content of 84.7 +/- 2.6% at 24 hours was decreased to 79.8 +/- 2%; the increased calcium level of 0.592 +/- 0.210 mg/L at 24 hours was decreased to 0.048 +/- 0.029 mg/L; and the increased sodium level of 2.035 +/- 0.649 mg/L was decreased to 0.631 +/- 0.102 mg/L. Administration of NPS 846 also lowered the NSS (improved neurological status) at 48 hours (7 +/- 3) and caused no significant changes in ischemic tissue or hemorrhagic necrosis volumes in the injured hemisphere at 24 or 48 hours. CONCLUSIONS: In this model of closed head trauma, NPS 846 improved neurological outcome, delayed the onset of brain edema, and improved brain tissue ion homeostasis.

Animals↗
PubMed1998

Anesthesia for cerebral aneurysm surgery.

Patients with subarachnoid hemorrhage from ruptured cerebral aneurysms frequently have systemic manifestations including hypovolemia and fluid and electrolyte disturbances in addition to neurologic symptoms. Anesthetic management therefore begins with proper preoperative evaluation and optimization. Anesthetic induction and maintenance are partly dependent on the patient's condition and seek to optimize cerebral perfusion, facilitate surgical exposure, and reduce the risk of intraoperative aneurysm rupture. Cerebroprotective strategy and adjunct monitors may be useful in some institutions.

Anesthesia, General↗
PubMed1997

Impaired cerebral autoregulation after mild brain injury.

BACKGROUND: Severe head injury may impair cerebral autoregulation, which can increase the risk of secondary neuronal injury. The likelihood of impairment in autoregulation is assumed to be low with mild head injury. We report here the absence of cerebral autoregulation in a patient who suffered a concussion from an automobile accident 6 days earlier. METHODS: The patient participated in a clinical study approved by the institutional human subjects review committee, investigating the dose-effect relationship of anesthetics on cerebral autoregulation. The patient was scheduled to undergo repair of a knee injury suffered during a motor vehicle accident, during which she had a concussion. The screening evaluation revealed no evidence of neurologic disease. The test was to be performed three times in each patient: baseline autoregulation measurements during stable fentanyl-nitrous oxide anesthesia, second and third measurements during low dose and high dose of the anesthetic to which the patient was assigned. Autoregulation was tested by increasing the mean systemic blood pressure from 80 mm Hg-100 mm Hg using a phenylephrine infusion while simultaneously recording flow velocity from a middle cerebral artery using transcranial Doppler ultrasonography. RESULTS: Static autoregulation testing during baseline testing demonstrated complete absence of this homeostatic mechanism and the study was canceled. Repeated testing in the recovery unit after the patient awoke showed identical results. CONCLUSIONS: Trivial mild head injury may result in loss of cerebral autoregulation. A clinical study of a larger series to document the incidence is warranted.

Adult↗
PubMed1997

Combined hemodilution and hypotension monitored with jugular bulb oxygen saturation, EEG, and ECG decreases transfusion volume and length of ICU stay for major orthopedic surgery.

STUDY OBJECTIVE: To assess the efficacy and safety of hemodilution combined with induced hypotension during surgery. DESIGN: Randomized, nonblinded, controlled study. SETTING: Operating room suite and intensive care unit (ICU) at a university hospital. PATIENTS: 16 ASA physical status I and II patients who underwent general or general plus epidural anesthesia for major orthopedic surgery. INTERVENTIONS: In Group 1 (n = 10), mean arterial blood pressure (MAP) was decreased to 50 mmHg by increasing the inspired concentration of isoflurane and injecting 75 mg of 0.5% bupivacaine into the epidural catheter. Hematocrit was decreased to 20% by phlebotomy and simultaneous infusion of crystalloid and colloid. In Group 2 (n = 6), isoflurane was adjusted to maintain MAP within 20% of baseline values, and no phlebotomy or hemodilution was used. MEASUREMENTS AND MAIN RESULTS: Efficacy of hemodilution combined with induced hypotension (Group 1) was compared to standard management of blood volume and pressure (Group 2) by measuring transfusion volume and length of ICU stay. Safety of hemodilution/hypotension was determined by measuring the electroencephalogram, internal jugular venous oxygen saturation, the electrocardiogram, and central venous oxygen saturation. In Group 1, both the volume of homologous blood (225 +/- 150 ml) and total blood (1440 +/- 286 ml) was significantly less than the volume of homologous blood transfused in Group 2 (2650 +/- 878 ml). No patients in Group 1, but all patients in Group 2 required ICU admission (3.5 +/- 1.6 days) for treatment to prevent sequelae from, or progression of, moderate-severe tissue edema and metabolic acidosis. Cerebral and myocardial measures were not significantly different between groups. CONCLUSIONS: Hemodilution combined with induced hypotension was safe and may reduce the need for transfusion and ICU admission.

Adult↗
PubMed1997

Intracranial pressure, middle cerebral artery flow velocity, and plasma inorganic fluoride concentrations in neurosurgical patients receiving sevoflurane or isoflurane.

UNLABELLED: This study examined the concentration-related effects of sevoflurane and isoflurane on cerebral physiology and plasma inorganic fluoride concentrations. Middle cerebral artery flow velocity (Vmca), intracranial pressure (ICP), electroencephalogram (EEG) activity, and jugular bulb venous oxygen saturation were measured, and cerebral perfusion pressure (CPP) and estimated cerebral vascular resistance (CVRe) were calculated at baseline and at 0.5, 1.0, and 1.5 minimum alveolar anesthetic concentration (MAC) sevoflurane (n = 8) or isoflurane (n = 6). Mannitol 0.5-0.75 g/kg was given before dural incision, and blood was sampled for plasma inorganic fluoride during surgery and for up to 72 h postoperatively. Both sevoflurane and isoflurane decreased Vmca (to 31 +/- 12 - 36 +/- 14 cm/s, mean +/- SD), did not significantly alter ICP (13 +/- 9 - 15 +/- 11 mm Hg), and did not cause epileptiform EEG activity. With sevoflurane, decreased Vmca was accompanied by decreased CPP and unchanged CVRe at 0.5 MAC, and unchanged CPP and increased CVRe at 1.0 and 1.5 MAC. Plasma inorganic fluoride was 39.0 +/- 12.9 microM at the end of anesthesia (3.2 +/- 2.0 MAC hours) with sevoflurane, similar to the value (36.2 +/- 3.9 microM) for 3.7 +/- 0.1 MAC hours sevoflurane in patients not receiving mannitol. Decreased Vmca during sevoflurane presumably results from decreased cerebral metabolic rate, with CVRe changing secondarily in accord with CPP. Plasma inorganic fluoride does not seem to be altered by mannitol-induced diuresis. IMPLICATIONS: In neurosurgical patients, sevoflurane decreased middle cerebral artery flow velocity and caused no epileptiform electroencephalogram activity and no increase of intracranial pressure or plasma inorganic fluoride. These effects are suitable for neurosurgery. Two other possible effects of sevoflurane, i.e., increased cerebrospinal fluid volume and/or intracranial elastance, may not be suitable for neurosurgery and warrant further study.

Anesthetics, Inhalation↗
PubMed1997

The rate of blood withdrawal affects the accuracy of jugular venous bulb. Oxygen saturation measurements.

BACKGROUND: Accuracy of jugular venous oxygen saturation (SjvO2) measurement depends on sampling of cerebral venous outflow blood not contaminated by systemic venous blood. The influence of the rate of blood withdrawal has not been determined. METHODS: The authors examined the effect of withdrawing blood at different rates from jugular venous bulb catheters (JVBC) on SjvO2 in 10 mechanically ventilated patients undergoing neurosurgical procedures. All patients received a standardized anesthetic consisting of propofol, fentanyl, vecuronium, and isoflurane. Routine monitors included electrocardiograph (ECG), invasive blood pressure, pulse oximetry, and a JVBC. During a period of stable anesthetic and surgical conditions, JVBC blood samples were drawn at 2, 4, and 10 ml/min using a calibrated pump (Harvard Pump model 900, Harvard Apparatus, South Natick, MA) during mild and moderate hypocapnia (arterial carbon dioxide tension [PaCO2], 26.0 +/- 0.5 and 33.0 +/- 0.5 mmHg). RESULTS: Faster rates of withdrawal (10 and 4 ml/min vs. 2 ml/min) resulted in significantly higher SjvO2 values at both levels of PaCO2 (66.0 +/- 3% and 61.2 +/- 3% vs. 56.9 +/- 3% at PaCO2 = 26.0 +/- 0.5 mmHg, and 75.0 +/- 3% and 71.3 +/- 3% vs. 68.0 +/- 3% at PaCO2 = 33.0 +/- 0.5 mmHg, respectively; P < 0.01). CONCLUSIONS: The authors conclude that the SjvO2 values measured with intermittent sampling are affected by the rate of withdrawing blood from JVBC, probably as a result of extracranial contamination. They recommend blood samples should be drawn slowly.

Adult↗