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Biomedical subjects

D H Birkett

Publications and source records attributed to D H Birkett.

At least 19 recordsLinked to original sources
PubMed1997

Minimally invasive management of low-grade and benign gastric tumors.

BACKGROUND: Benign gastric tumors and tumors of low-grade malignancy can be safely removed laparoscopically. METHODS: Seven patients were considered candidates for laparoscopic resection of gastric tumors. Inclusion criteria included small tumor size (less than 6 cm), exophytic or endophytic tumor morphology, and benign characteristics. Indications for surgical intervention included bleeding, weight loss, and need for tissue diagnosis. Patients ranged in age from 38 to 70. There were five female and two male patients. All patients underwent preoperative upper GI endoscopy. The procedures were performed using a four- or five-port technique. An Endo-GIA (US Surgical Company, Norwalk, Connecticut) was used to amputate those tumors located on the serosal surface of the stomach. Tumors on the mucosal surface were exposed via a gastrotomy, then likewise amputated using an Endo-GIA. The gastrotomy closure was then either hand sewn or stapled. Operating time ranged from 95 to 225 min. RESULTS: Final pathologic diagnoses included lipoma, lymphoma, leiomyoma, and leiomyosarcoma. There was a 28% conversion rate. There were no complications. Length of postoperative stay ranged from 4 to 7 days. There have been no tumor recurrences in 6-38-month follow-up. CONCLUSIONS: Minimally invasive management of benign and low-grade gastric tumors can be performed safely with excellent short- and long-term results.

Adult↗
PubMed1996

A porcine model for renal hemodynamic study during laparoscopy.

Laser Doppler flowmetry (LDF) is a sensitive method for the measurement of microvascular blood flow in tissue. The method has been found useful for estimating skin, liver, or gastrointestinal blood flow. Whether it can be applied laparoscopically and whether it is able to measure the intraparenchymal blood flow of an intraabdominal organ is still unknown. In a pilot study, 6 pigs received a laparotomy for placement of a 19-gauge LDF needle probe into the renal parenchyma. Three different locations of the lower pole kidney were chosen for the blood flow measurement. The reliability of using the instrument to measure the renal tissue blood flow was assessed by comparison of the results of renal arterial blood flow obtained from a well-established methodology--ultrasonic Doppler flowmetry. Recordings were taken following (a) intravenous administration of 0.005 mg/kg norepinephrine, (b) manual compression of the suprarenal aorta, and (c) intravenous injection of a lethal dose of phenobarbital (50 mg/kg). Measurements of LDF were possible in all kidney units. The renal tissue perfusion detected by LDF correlated excellently with the renal arterial blood flow under different renal perfusion pressures. The feasibility of using LDF probe to measure the renal tissue perfusion in a laparoscopic model was then assessed in 15 pigs. Under pneumoperitoneum, the right kidneys were approached transperitoneally with the animal in the decubitus position. A total of three trocars were used. The peritoneum and Gerota's fascia were incised and the LDF needle probe was manipulated and inserted by an endoforceps into the renal tissue via a 5-mm trocar. The insertion of the LDF needle probe was technically feasible in all 15 kidney units, and the depth of insertion could be adjusted under direct vision. Baseline values for the renal cortical and renal medullary blood flow were 50.1 +/- 17.7 and 8.8 +/- 3.3 ml/min/100 g tissue, respectively. Spatial variations of the LDF measurements averaged 6%, and temporal variations over 15 min averaged 5%. Four additional hemodynamic parameters were simultaneously recorded, including left carotid artery blood flow, aortic blood pressure, inferior vena caval pressure, and intraabdominal pressure. It appears that systemic and renal hemodynamic parameters can be monitored reliably and continuously in the porcine model. This method allows further information concerning hemodynamic changes and safety of laparoscopy to be obtained.

Animals↗
PubMed1996

Changes in urinary output and electrolytes during gaseous and gasless laparoscopy.

Urological laparoscopy has gained increasing acceptance recently. Alterations in renal water and electrolyte homeostasis by carbon dioxide peritoneal insufflation, retroperitoneal insufflation and abdominal wall lifting were measured in 30 well-hydrated pigs over a 2-h period. Oliguria was observed after gaseous insufflation but not alter lifting the abdominal wall. Return to normal urinary output was observed at 30 min after release of pneumoretroperitoneum, and 60 min after pneumoperitoneum. Creatinine clearance declined, while the clearance rates of potassium, sodium and urea remained unchanged during peritoneal and retroperitoneal insufflation. An elevated serum aldosterone concentration was found which may mediate the increased urinary excretion of potassium and decreased urinary excretion of sodium found during peritoneal insufflation. Renal function remained stable, despite an elevation of serum creatine kinase being elicited after lifting the abdominal wall. In conclusion, significant changes in water and electrolyte homeostasis occurred gaseous, not gasless, laparoscopy in pigs.

Animals↗
PubMed1996

One-stage retrograde approach to Nd:YAG laser palliation of esophageal carcinoma.

BACKGROUND AND STUDY AIMS: The aim of the present study was to determine the safety, efficacy, and feasibility of a one-stage retrograde approach to Nd:YAG laser palliation of esophageal carcinoma carried out under general anesthesia. PATIENTS AND METHODS: Endoscopic Nd:YAG laser therapy was used on 150 occasions in 62 consecutive patients with advanced malignant obstruction of the esophagus. All procedures were carried out under general anesthesia. The lesion was first dilated using a Savary-Gilliard dilator or balloon technique, and the endoscope was then passed beyond the lesion. Laser energy was applied to the lesion in a circumferential manner as the scope was withdrawn along the length of the lesion, until an adequate lumen was established. RESULTS: Ninety-three percent of the patients had symptomatic improvement, defined as reduction in the subjective dysphagia grade, and only 14% of the patients required repeat procedures within 30 days. Fifty percent of the patients experienced effective palliation with only one procedure over the entire course of their illness. In patients with recurrent dysphagia, the mean time between procedures was 100 days. Seventy-six percent of the patients were discharged on the day following the procedure. Complications included the development of pneumomediastinum or subcutaneous emphysema in five cases, and esophageal perforation in two cases. All cases of pneumomediastinum or subcutaneous emphysema or perforation were managed by conservative therapy. Hemorrhage requiring transfusion occurred in two cases. There were three apparently procedure-related deaths occurring within 30 days of the initial procedure. CONCLUSIONS: Effective palliation of obstructing esophageal carcinoma can be achieved in one session using a one-stage retrograde approach with the Nd:YAG laser under general anesthesia. When compared to other palliative modalities, this method produces a longer dysphagia-free interval, and patients with a terminal illness are therefore able to spend more time out of hospital.

Adult↗
PubMed1995

Changes in intracranial pressure associated with apneumic retractors.

OBJECTIVE: To investigate the effect of apneumic retraction on intracranial pressure (ICP) using a live porcine model. DESIGN: Five 25- to 30-kg pigs had a fiber-optic ICP bolt inserted under general endotracheal anesthesia and were monitored for ICP, mean arterial pressure, arterial blood gas measurements, and intra-abdominal pressure before, during, and after pneumoperitoneum, with each period 30 minutes long. These series of measurements were repeated after artificially raising ICP with an epidural balloon to create a head-injured model. The mean (+/- SE) ICP in the noninjured model at baseline was 13.46 +/- 1.01 mm Hg; during pneumoperitoneum, 18.72 +/- 1.50 mm Hg (P = .0001). Similarly, in the head-injured model, ICP was raised artificially to a new baseline of 22 +/- 1.75 mm Hg with an epidural balloon, and pneumoperitoneum increased ICP to 27.40 +/- 0.93 mm Hg (P = .0001). Pneumoperitoneum was then released, and an apneumic retractor was inserted while maintaining the inflated epidural balloon. MAIN OUTCOME MEASURE: Changes in ICP. RESULTS: Applying anterior wall retraction equivalent to 20 mm Hg was not associated with changes in ICP. These observations were independent of any changes in arterial PCO2 or arterial pH. Following the release of pneumoperitoneum, abdominal wall retraction, and epidural balloon, all measurements reverted to baseline. CONCLUSION: Pneumoperitoneum adversely affects ICP, while apneumic retraction may not affect animals with raised ICP. These findings suggest that pneumoperitoneum should be used with caution in patients with raised ICP, and apneumic retraction may be a safer alternative for laparoscopic evaluation in this population.

Abdominal Muscles↗
PubMed1995

The impact of pneumoperitoneum, pneumoretroperitoneum, and gasless laparoscopy on the systemic and renal hemodynamics.

BACKGROUND: The use of therapeutic laparoscopy has become widespread recently. It is important to assess the effects of gaseous and gasless laparoscopy on systemic and renal hemodynamics. STUDY DESIGN: A prospective controlled animal study was performed on 40 well-hydrated pigs. Systemic and renal hemodynamics were monitored during peritoneal insufflation, retroperitoneal insufflation, and abdominal wall lifting for a period of two hours. A laser Doppler flow meter was applied laparoscopically to measure the renal cortical tissue perfusion. RESULTS: Peritoneal insufflation of carbon dioxide to a pressure of 15 mm Hg elicited transient elevations of the aortic pressure and carotid arterial blood flow. Unilateral pneumoretroperitoneum caused a smaller change on systemic hemodynamics. Pneumoperitoneum and pneumoretroperitoneum caused oliguria. Superficial renal cortical blood flow reduction decreased by an average of 60 percent in the compressed kidney, and blood flow returned to the pre-insufflation level after the pressure was released. A gradual decrease of tissue perfusion in the contralateral kidney and a concomitant gradual increase of the intra-abdominal pressure were observed when pneumo-retroperitoneum was maintained for two hours. No significant changes in urinary output and in systemic and renal hemodynamics were found when the abdominal wall was lifted up with a force equivalent to 15 mm Hg. CONCLUSIONS: Significant systemic and renal hemodynamic changes were elicited in gaseous but not in gasless laparoscopy, which may explain the decreased urinary output observed during gaseous laparoscopy. Pneumoperitoneum caused greater systemic and renal hemodynamic alterations than pneumoretroperitoneum; however, the effects were transient and reversible after a period of two hours.

Animals↗
PubMed1994

A new 3-D laparoscope in gastrointestinal surgery.

This study was set up to compare three-dimensional imaging of a new three-dimensional laparoscope with two-dimensional imaging in the inanimate and clinical settings. In the clinical setting the laparoscope was used in a total of 50 different laparoscopic operations. It provided excellent depth perception, definition, and resolution. The relationships of structures were more easily defined, and instrument manipulation was easier, doing away with the need for "touch and feel" to determine instrument position. Three-D imaging made cannulation of the cystic duct for cholangiography or with a flexible choledochoscope easier. In the inanimate setting basic simple tasks took the same time in 2-D as in 3-D, whereas a more complicated procedure of passing a needle and suture through a series of hoops was 25% faster when performed in 3-D compared to 2-D. Three-D imaging may reduce operative time for laparoscopic procedures, particularly the more complicated operations.

Cholangiography↗
PubMed1994

Clinical and laboratory evaluation of an electrosurgical laparoscopic trocar.

Electrosurgical energy may be utilized as an adjunct to mechanical force for insertion of laparoscopic trocars. The advantage of this approach may be better operator control of insertion, with less risk of intraperitoneal and retroperitoneal injury. To assess the safety and efficacy of electrosurgical trocars, we compared them to mechanical trocars in clinical and animal trials. During 100 trocar introductions in 25 laparoscopic cholecystectomies, insertion force was measured. In contrast to mechanical trocars, which required progressively more force to insert as size increased, electrosurgical trocars required the same low insertion force regardless of size. No wound complications occurred. In animal experiments, wound healing (measured histologically and by bursting strength) was normal and equivalent for mechanical and electrosurgical insertions. We conclude that electrosurgical trocars require less force for insertion and do not impair wound healing. Electrosurgical trocars may thus offer important safety advantages over mechanical trocars.

Abdominal Muscles↗
PubMed1994

Diagnostic laparoscopy increases intracranial pressure.

There are numerous reports in the literature concerning the use of laparoscopy for evaluation of abdominal trauma victims. The safety of laparoscopic evaluation in trauma patients with potentially severe intracranial injuries has not yet been analyzed. This study investigates the effect of pneumoperitoneum on intracranial pressure (ICP) and cerebral perfusion pressure. Five 30-kg pigs were monitored for ICP, mean arterial pressure (MAP), arterial blood gases (ABGs), and intra-abdominal pressure (IAP) for 30 minutes before, during, and after pneumoperitoneum. These series of measurements were repeated after artificially elevating the ICP with an epidural balloon. The mean ICP at baseline was 13.46 +/- 1.01 mm Hg. The mean ICP during pneumoperitoneum was 18.72 +/- 1.50 mm Hg (p = 0.0001). The ICP increased to 27.40 +/- 0.93 mm Hg (p = 0.0001) after the ICP was raised artificially to a new baseline of 22 +/- 1.75 mm Hg with the epidural balloon. These increases were independent of changes in arterial PCO2 or arterial pH. Pneumoperitoneum during laparoscopy may increase ICP and must be used cautiously in evaluating patients with severe head injuries.

Animals↗
PubMed1992

Laser lithotripsy for the management of retained stones.

The morbidity of reoperation for retained biliary stones is not significant. Many techniques have been developed to avoid reoperation. This study analyzes T-tube tract choledochoscopy and lithotripsy using a 504-nm pulsed dye laser for treatment of retained stones. A flexible choledochoscope is passed into the biliary tract and laser energy is delivered under endoscopic visualization after passing a 320-microns laser fiber through the instrument channel. Eight patients were treated in nine sessions. The mean number of pulses was 1512.33, delivered at 3 to 5 Hz with an energy of 100 to 120 mJ. In all patients, the biliary tract was cleared. A single patient's treatment was complicated by transient bacteremia. Mean follow-up was 10 months. Choledochoscopic laser lithotripsy is a safe, effective technique that may also play a major role in laparoscopic common duct surgery.

Boston↗
PubMed1992

Comparison of a pulsed dye laser and electrohydraulic lithotripsy on porcine gallbladder and common bile duct in vitro.

With the advent of minimal access biliary procedures there is a need for a safe intracorporal lithotripsy technique that can be used through small flexible endoscopes. Currently, the two techniques available are electrohydraulic lithotripsy and laser induced shock wave lithotripsy. In this study we compare the effect of a 504 nm coumarin pulsed dye laser and electrohydraulic lithotripsy on in vitro porcine gallbladder and common bile duct. Electrohydraulic lithotripsy at the lowest energy the generator would deliver caused perforation of both tissues in only a few pulses when a 1.9-F probe was placed in direct contact with the tissue. Energy from a 504 nm coumarin pulsed dye laser delivered through a 320-microns fiber placed in light contact with the tissue caused an energy-dependent perforation after 50 pulses in from none to 44% of tissues. It was also found that there was a higher incidence of perforation in more vascular than non-vascular tissue. When the EHL probe and the laser fiber were held 1-2 mm from the tissue surface, discharge of each resulted in no perforation. On histological examination of the tissues, the perforations were found to be very small with laser lithotripsy and considerably larger with the electrohydraulic lithotripsy. It was felt that laser lithotripsy in the clinical situation was likely to be much safer than electrohydraulic lithotripsy.

Animals↗
PubMed1992

Primary adenosquamous and squamous cell carcinoma of the colon and rectum.

Three new cases of squamous cell and adenosquamous carcinoma of the rectum are reported, bringing the total number of cases in the English medical literature to 72. Each of the three patients presented with painless hematochezia. Therapy was by surgical resection followed by chemoradiation therapy in two patients. The incidence, presentation, diagnostic criteria and methods, tumor location, natural history, theory of etiology and management of this unusual tumor are discussed.

Adenocarcinoma↗
PubMed1992

Postoperative T-tube tract choledochoscopy.

One hundred twenty-six patients underwent postoperative fiberoptic T-tube tract choledochoscopy for the management of retained biliary calculi as demonstrated by T-tube cholangiography. Extraction was successful in 94% of patients with retained stones. Thirty-nine patients had more than 1 stone, 20 patients had heptic duct stones, and 14 patients had large stones requiring electrohydraulic lithotripsy or laser fragmentation. Stone removal was not possible in six patients, secondary to either slippage of the T-tube with obliteration of the tract, inability to remove the stones with available instruments, a tortuous tract, or choledochoscope malfunction. Minor complications, most commonly transient fever, occurred in 12 patients. No serious complications or deaths occurred. The advantages of T-tube tract choledochoscopy include direct visualization of the biliary tree, avoidance of radiation exposure, and easy access to hepatic duct stones. This is the preferred method for treating retained biliary calculi in patients with a T-tube in situ.

Adult↗
PubMed1992

Biliary laser lithotripsy.

Laser lithotripsy is an excellent method of fragmenting those biliary stones that cannot be removed easily by less technically advanced methods such as basket extraction. The energy can be delivered through fine flexible fibers, around 200 to 320 microns in diameter, that can be passed through the channels of a variety of small endoscopes. Currently, the optimal laser seems to a pulsed system because of the conversion of light to acoustic energy with minimal heating of the surrounding tissues, thus avoiding the chance of tissue injury and perforation. The best wavelength seems to be 504 nm, because at this wavelength, there is maximum absorption of laser energy by pigment stones, resulting in fragmentation using low-energy pulses. With further research, optimal wavelengths and pulse durations may emerge.

Cholelithiasis↗
PubMed1992

Nutritional outcome and pneumonia in critical care patients randomized to gastric versus jejunal tube feedings. The Critical Care Research Team.

OBJECTIVE: To compare nutritional status, gastric colonization, and rates of nosocomial pneumonia in ICU patients randomized to gastric tube feeding vs. patients fed by an endoscopically placed jejunal tube. DESIGN: Randomized, prospective study. SETTING: Medical and surgical ICUs at Boston City Hospital; surgical ICU at University Hospital. PATIENTS: Of the 38 study patients, 19 were randomized to gastric tube feeding and 19 were randomized to an endoscopically placed jejunal tube. The two groups were similar in age, sex, race, underlying disease, and type of surgery. RESULTS: The two patient groups were similar in number of days fed, duration of ICU stay, duration of mechanical ventilation, days of antibiotic therapy, and days with fever. Compared with the gastric group, the jejunal group had more patients with circulatory shock on admission (79% vs. 68.4%), higher admission Acute Physiology Score (24.0 vs. 21.7), and fewer patients with pneumonia at randomization (26.3% vs. 31.6%). The jejunal group received a significantly higher percentage of their daily goal caloric intake (p = .05), and had greater increases in serum prealbumin concentrations (p < .05) than the patients with gastric tube feeding. Although the jejunal tube group had more days of diarrhea (3.3 +/- 6.6 vs. 1.8 +/- 2.9), this difference was not statistically significant. Nosocomial pneumonia was diagnosed clinically in two (10.5%) patients in the gastric tube group and in no patients in the jejunal tube group. CONCLUSIONS: Patients fed by jejunal tube received a significantly higher proportion of their daily goal caloric intake, had a significantly greater increase in serum prealbumin concentrations, and had a lower rate of pneumonia than patients fed by continuous gastric tube feeding.

Adult↗