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Biomedical subjects

H S Ho

Publications and source records attributed to H S Ho.

At least 37 records · Page 2Linked to original sources

Gastrostomy for enteral access. A comparison among placement by laparotomy, laparoscopy, and endoscopy.

BACKGROUND: Access to the stomach for long-term enteral feeding can be achieved via laparotomy (open GT), laparoscopy (lap GT) or endoscopy (PEG). We compared the three methods of gastrostomy to determine whether any one has an advantage over the others. METHODS: A retrospective analysis was done of 356 gastrostomies performed between January 1990 and June 1995. RESULTS: Of these 356 gastrostomies, 214 were open GT, 60 were lap GT, and 82 were PEG. The completion rate was high, 98.1% to 100%. The perioperative mortality rates were low and similar among the 3 methods; 4.2% for open GT, 5.3% for lap GT, and 4.9% for PEG (p = 0.87, Chi square test). Cardiac arrest was the predominant immediate cause of all perioperative deaths (68.8%). Overall, none of the deaths was directly related to the gastrostomy procedure. Major complications occurred in 24.9% of patients receiving open GT, in 18.3% of patients with lap GT, and in 17.1% of patients with PEG. Long-term complications developed in 25.9% of open GT, 25.6% of lap GT, and 30. 4% of PEG. The revision rates were similar for all 3 methods, 6.7% for open GT, 10% for lap GT, and 6.1% for PEG. CONCLUSIONS: Gastrostomy can be performed safely by all three techniques, with similar outcomes. PEG is our method of choice. Lap GT is preferred in patients with head and neck carcinoma, patients with obstructing esophageal carcinoma, and patients who have problems with overlying liver or colon. Open GT is reserved for cases with extensive intraabdominal adhesions or those where the procedure is done during an ongoing laparotomy.

Adult↗

Laparoscopic Roux-en-Y gastric bypass for super/super obesity.

Laparoscopic gastric bypass has been recently introduced as an alternative method to conventional open gastric bypass. This procedure has been generally limited to patients with a BMI <60 kg/m2 due to the possible technical limitations of the laparoscopic instruments. In this article, we present a patient with super/super obesity (61 kg/m2) who underwent Rouxen-Y gastric bypass using the laparoscopic approach.

Adult↗

The use of magnesium sulphate in the intensive care management of an Asian patient with tetanus.

Tetanus, a potentially fatal but largely preventable disease through immunisation, is rare in Singapore. Timely diagnosis and appropriate intensive care management is essential to ensure survival. We aim to report the management of such a patient with magnesium sulphate. This has not been reported locally. By maintaining serum magnesium at 3 to 4 mmol/l we were able to control sympathetic overactivity by day 6, stop neuromuscular blockade by day 7 and wean off ventilator by day 11. Aminoglycoside-induced hypomagnesemia was also demonstrated, necessitating an increase in magnesium sulphate infusion rate to maintain serum magnesium at therapeutic level.

Adult↗

Effect of open and laparoscopic surgery on cellular immunity in a swine model.

Immune suppression associated with trauma has been demonstrated to be proportional to the magnitude of injury. Laparoscopic surgery has been shown to produce a diminished stress response compared to open surgery. Postoperative immune function, specifically cellular immunity, may be better preserved after laparoscopic surgery compared to open surgery. The aim of this study was to examine the effect of open versus laparoscopic surgery on cellular immunity in a swine model. Twenty domestic female pigs were randomly selected for laparoscopic cholecystectomy (LC) or open cholecystectomy (OC). Cellular immune functions were evaluated with delayed-type hypersensitivity (DTH) skin test and serial phytohemoagglutinin (PHA)-induced T-cell proliferation of the peripheral blood. There was a significant reduction in PHA-induced T-cell proliferation in both LC and OC groups on days 1 and 3 compared to preoperative values (p < 0.05). The reduction of mitogen-induced T-cell proliferation after LC was significantly less than after OC on day 1 (p = 0.03). The mean DTH reaction was 29.7 +/- 3.7 mm2 in the LC group compared to 13.9 +/- 1.2 mm2 in the OC group (p < 0.001). There was no difference in postoperative white blood count values between the two groups. Suppression of cellular immunity occurred after both LC and OC. The magnitude and duration of impaired cellular immunity after laparoscopic surgery was less than after open surgery as measured by T-cell proliferation and DTH response.

Animals↗

Cardiopulmonary responses to experimental venous carbon dioxide embolism.

BACKGROUND: Although the low-flow CO2 insufflation rate used to initiate pneumoperitoneum may reduce the severity of potential venous embolism, its safety is not established. METHODS: Anesthetized pigs were ventilated with room air at a fixed minute ventilation. After 1 h of baseline, they were intravenously infused with CO2 at the rate of 0.3, 0.75, or 1.2 ml/kg/min for 2 h (n = 5 for each group), followed by 1 h of recovery. RESULTS: All animals experienced pulmonary hypertension, depressed stroke volume, hypoxemia, hypercarbia, and acidemia during intravenous CO2 infusion. They had systemic hypertension at the low rate of hypotension at the highest rate of infusion. End-tidal CO2 levels briefly decreased, then increased in all cases. In the highest rate group, three of the five animals (60%) died at 50, 65, and 100 min of infusion. These three animals had severe hypotension and hypoxemia, with visible coronary gas embolism. There was no patent foramen ovale at necropsy in any animals. CONCLUSIONS: The low-flow insufflation rate exceeds the fatal rate of continuous intravenous CO2 infusion. End-tidal CO2 levels were increased in venous CO2 embolism, not decreased as seen in venous air embolism. Severe hypoxemia and hypotension are predictors of potentially fatal cases.

Acid-Base Imbalance↗

The impacts of experimental necrotizing pancreatitis on hepatocellular ion homeostasis and energetics: an in vivo nuclear magnetic resonance study.

BACKGROUND: Liver dysfunction may be an early event or the end result of multiple organ dysfunction (MOD) in necrotizing pancreatitis. This study measured the early changes in hepatocellular ions and energetics associated with such conditions. METHODS: Twenty-five rats, prepared with a 23Na and 31P double-tuned nuclear magnetic resonance surface coil secured over the dome of the liver, were randomized into 5 groups: control, 10 and 20 minutes of total inflow ischemia, pancreatitis induced by deoxycholic acid (DCA), and sham-DCA (saline injection). Dysprosium-TTHA3- solution was used to separate the intracellular and extracellular sodium peaks. RESULTS: In rat liver, 20 minutes of total inflow occlusion caused irreversible depletion of high-energy phosphates. Changes at 2 hours after the onset of DCA-pancreatitis are compared with changes after 20 minutes of ischemia (mean +/- SEM). Although the DCA-pancreatitis animals did not become hypotensive until 1 hour after the induction of pancreatitis, the changes in hepatic intracellular ions and energetics began soon after such an insult. At 2 hours after the onset of pancreatitis, hepatocellular pHi and [NA+]i were 6.99 +/- 0.16 and 78.4 +/- mmol/L, respectively (P < .01, compared with sham animals). A similar pattern of changes in hepatic bioenergetics also occurred. After the onset of pancreatitis, the hepatic cytostolic phosphorylation potential decreased with time (y = 0.654 - 0.004t, where t is time in minutes and r2 = 0.967 and the rate of hepatic hydrolysis of adenosine triphosphate increased progressively (y = 0.702t + 91.363, where t is time in minutes and r2 = 0.969. These changes correlated well with the accumulated [Na]i. CONCLUSIONS: Unresuscitated necrotizing pancreatitis caused severe hepatocellular acidosis, profound sodium accumulation, and bioenergy depletion early in its course. These effects were as severe as those induced by total liver ischemia. Liver dysfunction may be an early, not terminal, event of MOD in necrotizing pancreatitis.

Adenosine Triphosphate↗

The role of antibiotic prophylaxis in severe acute pancreatitis.

OBJECTIVE: To assess the impact of intravenous (IV) antibiotic prophylaxis on the incidence of pancreatic infection and the mortality rate in severe acute pancreatitis. DESIGN: Restropective review of a cohort of 180 patients with severe acute pancreatitis. SETTING: A tertiary referral center in Sacramento, Calif. INTERVENTION: The use of IV antibiotic prophylaxis evolved during 3 periods from no antibiotics in 50 patients (1982-1989), to nonprotocol use in 55 patients (1990-1992), to a 4-week course of imipenem-cilastatin sodium (1993-1996) given to 75 patients having Acute Physiology and Chronic Health Evaluation (APACHE) II scores greater than 6 and pancreatic necrosis (> 15% of the gland), peripancreatic necrosis, or peripancreatic collection. MAIN OUTCOME MEASURES: Pancreatic infection and mortality. RESULTS: Without antibiotic prophylaxis, the incidence of pancreatic infection was 76% (38/50). Intravenous antibiotic prophylaxis reduced the infection rate of 45% (25/55) (P = .03). The imipenem-cilastatin protocol further reduced the infection rate to 27% (20/75) (P = .04). The mortality rates showed only a decreasing trend, from 16% (1982-1989) to 7% (1990-1992) to 5% (1993-1996) (P = .11). Patients with sterile severe acute pancreatitis had a mortality rate of 2% (2/97); whereas 17% (14/83) of patients with infection succumbed to the disease. Patients developing infection within the first 4 weeks from the onset of illness had mortality rates ranging from 19% to 40%, compared with 0% to 8% for those who became infected after 4 weeks. No patient with pancreatic infection developing after 4 weeks died with the imipenem-cilastatin protocol. CONCLUSIONS: Intravenous antibiotic prophylaxis significantly reduced the infection rate in severe acute pancreatitis, with only a trend toward improved survival. A prospective, randomized, double-blind multicenter trial comparing the efficacy of different types and/or combinations of antibiotic prophylaxis in severe acute pancreatitis is indicated.

Acute Disease↗

Cardiopulmonary responses to intravenous infusion of soluble and relatively insoluble gases.

BACKGROUND: Carbon dioxide is the current gas of choice for pneumoperitoneum, but hemodynamic and acid-base effects secondary to its systemic absorption have been reported. Various studies have suggested inert gases as alternatives. METHODS: We studied the cardiopulmonary responses to intravenous infusion of carbon dioxide, nitrous oxide, argon, helium, and nitrogen in anesthetized swine. The gas was infused into the femoral vein at a rate of 0.1 ml . kg-1 . min-1 for 30 min. The changes in end-tidal CO2, mean arterial pressure, hemodynamics, and arterial blood gases were compared to baseline values. RESULTS: No animals died during infusion of the soluble gases (CO2 and N2O). Three of the five pigs infused with nitrogen died suddenly at 20 and 30 min of infusion. The animals in the insoluble gas groups (Ar, He, N2) experienced clinical pulmonary gas embolism and severe acidemia, hypercapnea and tachycardia. CONCLUSIONS: Venous gas embolism is poorly tolerated when the gas is relatively insoluble. Insoluble gases should not be used for pneumoperitoneum when there is any risk of venous gas embolism.

Animals↗

Current approach to the surgical management of chronic pancreatitis.

The indications for surgical intervention in chronic pancreatitis are suspicion of malignancy, local complications, and intractable pain. Chronic pancreatitis is a risk factor for development of pancreatic carcinoma, and carcinomas may present, initially with a clinical picture of chronic pancreatitis. Local complications of chronic pancreatitis such as common bile duct or duodenal obstruction and enlarging or symptomatic pseudocyst also mandate surgical intervention. Thrombosis of the splenic vein with left-sided portal hypertension is common and associated with a 10% incidence of gastric variceal hemorrhage, which requires splenectomy. The role of surgery in the management of pain associated with chronic pancreatitis is to provide relief. When the pain interferes substantially with the patient's quality of life or narcotics are required for pain relief, surgical intervention is indicated. Other factors that should be incorporated in assessing the need for surgical intervention are malnutrition due to the inability to eat or malabsorption, the need for frequent hospitalization, and the inability to work. The operation selected for chronic pancreatitis should correct or deal with all structural abnormalities, provide long-term pain relief, have a low mortality and morbidity rate, minimize subsequent exocrine and endocrine insufficiency, and have results independent of abstinence from alcohol. No single operation can provide an optimal solution to the management of pain or these diverse complications of chronic pancreatitis. The operation chosen must be individualized to treat the patient's needs.

Abdominal Pain↗

The impact of laparoscopic cholecystectomy on the treatment of symptomatic cholelithiasis.

BACKGROUND: There has been a debate about the cost-effectiveness of laparoscopic cholecystectomy (LC), as well as a concern regarding its possible overutilization and changes in the indication for surgery. METHODS: A retrospective analysis of all cholecystectomies performed at UCDMC from 1988 to 1994 was done. The annual rate of cholecystectomy increased by 50% in 1990 when LC was introduced but has since stabilized at a rate 11% higher than the rate before LC. The disease status and severity did not change. RESULTS: The incidence of nonelective surgery remained stable at 31.2% to 37.5%. Elective cholecystectomy had lower mortality (0.16% vs 1.8%, P = 0. 029), morbidity (2.6% vs 11.2%, P = 0.0001), and conversion rate (2. 6% vs 16%, P = 0.0001) and a shorter length of stay (2.1 days vs 5.4 days), compared with nonelective procedure. CONCLUSIONS: The indication for surgery in cholelithiasis has not changed since the introduction of LC. In patients with symptomatic gallstones, early elective surgery is recommended and may be more cost-effective.

Adult↗

The renal effects of 7.5% NaCl-6% dextran-70 versus lactated Ringer's resuscitation of hemorrhage in dehydrated sheep.

A small volume of 7.5% NaCl/6% Dextran-70 (HSD) can rapidly expand the plasma volume, but concerns exist regarding its adverse effects on renal function in the dehydrated state. Sheep were thirsted for 4 days (13% plasma volume contraction), and subjected to a fixed-pressure shock model (mean arterial pressure of 50 mmHg for 2 h), followed by resuscitation with either HSD (4 mL/kg) or lactated Ringer's solution (LR; 37 mL/kg). Mean arterial pressure was restored to 90%, cardiac output to 125% and 120%, and plasma volume to 78% and 72% of baseline in LR and HSD groups, respectively. Glomerular filtration rate improved to 100% of baseline following HSD compared with 82% following LR. No significant urinary 70,000 molecular weight dextran was observed, suggesting an intact renal glomerular membrane. These data suggest that small volume HSD resuscitation is effective, even with pre-existing dehydration. In addition, renal function is not compromised by HSD resuscitation of hemorrhaged, dehydrated animals.

Animals↗

Gastrointestinal and pancreatic complications associated with severe pancreatitis.

OBJECTIVE: To study the outcomes of gastrointestinal fistulas and pancreatic ductal disruption in severe pancreatitis. SETTING: University tertiary referral center. PATIENTS: One hundred thirty-six patients from 1982 to 1994. INTERVENTION: Diversion followed by resection and ostomy closure for gastrointestinal fistulas, pancreaticojejunostomy for pancreatic fistulas, and excision, external drainage, or internal drainage for pseudocysts. RESULTS: The incidence of infection was 24% (8/33) for peripancreatic fluid collections and 59% (61/103) for patients with necrosis plus fluid collections or necrosis without fluid. Sixty-nine patients developed 25 gastrointestinal fistulas and 51 complications caused by pancreatic ductal disruption. Necrosis and infection but not the open packing technique were associated with increased risk of gastrointestinal fistulas. In patients with pancreatic ductal disruption, pancreatic fistulas developed following necrosectomy and external drainage, while pancreatic pseudocysts evolved from undrained peripancreatic fluid collections. Gastrointestinal fistulas required prompt operative intervention, whereas pancreatic ductal disruption was treated nonoperatively initially. The mortality rate was 13% (3/23) in patients with gastrointestinal fistulas, similar to the overall mortality rate of 10.3% (14/136). There was no mortality in patients with pancreatic fistulas or pseudocysts. Length of hospital stay was prolonged by the presence of necrosis and infection, not by gastrointestinal fistulas or ductal disruption. Thirty-eight of the 69 patients with these complications required readmission for operative management of their complications. To date, only 18 (13.2%) of 136 patients with severe pancreatitis have not required surgical intervention. CONCLUSIONS: Gastrointestinal fistulas and pancreatic ductal disruption are common in severe pancreatitis. Although these complications are not associated with increased mortality or prolonged initial length of stay, readmission for elective surgical correction is necessary in most patients. Severe pancreatitis is a surgical disease, requiring both acute and long-term surgical care.

APACHE↗

Effector of hemodynamics during laparoscopy: CO2 absorption or intra-abdominal pressure?

Controversy has been raised about the effects of systemic carbon dioxide accumulation versus the intra-abdominal pressure on hemodynamics during laparoscopy. We compared the acid-base and hemodynamic changes during pneumoperitoneum in a randomized cross-over study between CO2 and nitrogen gases to test the hypothesis that the CO2 absorbed during laparoscopy, rather than the 15 mmHg intra-abdominal pressure created, accounted for these changes. Eight adult pigs were anesthetized and ventilated with a fixed minute ventilation. Metabolic function was measured from analysis of expired flow by a metabolic measurement cart. After baseline periods, animals were randomized into two groups, for 2 hr of either CO2 or nitrogen pneumoperitoneum at 15 mmHg intra-abdominal pressure, followed by 1 hr of recovery. After at least a 48-hr recovery period, the experiment was repeated with the other gas. Metabolic data revealed that there was a significant absorption of CO2 gas across the peritoneal epithelium during CO2 pneumoperitoneum. Animals insufflated with CO2 gas experienced a 75% increase in pulmonary CO2 excretion, with significant acidemia and hypercapnia, whereas there were no acid-base disturbances in those with nitrogen insufflation. Oxygen consumption remained essentially unchanged in both groups, even during pneumoperitoneum. CO2 pneumoperitoneum was also associated with systemic and pulmonary arterial hypertension and a reduction in stroke volume of up to 15%. Pneumoperitoneum alone did not compromise hemodynamics. Pneumoperitoneum using CO2 gas during laparoscopy resulted in systemic CO2 absorption across the peritoneum. This led to acidemia, hypercapnea, and depressed hemodynamics. The intra-abdominal pressure routinely used during laparoscopic surgery did not affect metabolic function, acid-base balance, or hemodynamics in the experimental model.

Acid-Base Equilibrium↗

Hemodynamic effects of argon pneumoperitoneum.

The hemodynamic effects of argon pneumoperitoneum were studied to define its possible role as an alternative gas for intraperitoneal insufflation during minimally invasive surgery. Adult pigs were anesthetized and placed on mechanical ventilation. Parameters measured or determined included mean arterial (MAP), pulmonary arterial (PAP), pulmonary arterial wedge (PAWP), right atrial (CVP), and inferior vena cava venous (IVC) pressures, total excretion of CO2 (VCO2), oxygen consumption (VO2), minute ventilation, and arterial blood gases. Also determined were cardiac output, stroke volume, and systemic vascular resistance all indexed to weight (CI, SVI, SVRI). Data were recorded during a 1-h baseline, 2 h of insufflation with argon gas at a constant pressure of 15 mmHg, and 1 h recovery after desufflation. There was no significant change from baseline in VCO2, VO2, MAP, PAP, PAWP, CVP, PaCO2, or arterial pH. Argon pneumoperitoneum significantly increased systemic vascular resistance index and exerted a depressant effect on stroke volume index and cardiac index by 25% and 30% from baseline values, respectively (P < 0.05). Inferior vena cava pressure increased as a reflection of the intraabdominal pressure. Argon insufflation had no effect on respiratory function. Argon gas may not be physiologically inert, and in patients with cardiovascular disease its effects may be clinically important.

Animals↗

The effects of selected stimulus waveforms on pulse and phase characteristics at sensory and motor thresholds.

BACKGROUND AND PURPOSE: The purposes of this investigation were to determine the effect of five commonly used voltage waveforms (four pulsed and one sinusoidal) on excitation of sensory and motor nerves and to characterize variables associated with reaching threshold. SUBJECTS: Eighteen healthy subjects were stimulated during one session via surface electrodes placed over the forearm and leg. METHODS: Stimulation amplitude was increased at a constant rate, and the threshold of sensory and motor excitation was determined. Measured variables included peak voltage, peak current, phase charge, and total pulse charge. RESULTS: Three-factorial, repeated-measures analysis of variance and Newman-Keuls tests revealed that phase charge varied the least during excitation induced by the five waveforms. Total pulse charge markedly increased when bursts of 10 symmetrical pulses, 25 symmetrical pulses, or amplitude-modulated waveforms were used. Monophasic and symmetrical biphasic waveforms required the least amount of total pulse charge. All measurements were higher during motor threshold than during sensory threshold, and the measurements were higher in the leg than in the forearm. CONCLUSION AND DISCUSSION: The authors concluded that all five studied waveforms were effective at threshold excitation of peripheral sensory and motor nerves. Of the five waveforms, the symmetrical biphasic waveform, having a low total pulse charge, may be the preferred waveform, and the 25 symmetrical pulses and amplitude-modulated waveforms may be considered the least preferred due to high total pulse charge.

Adult↗

High level of arginine vasopressin and 7.5% NaCl/6% dextran-70 solution: cardiovascular and renal effects.

A marked diuresis has been observed following resuscitation of hypotensive hemorrhaged animals with small volume hypertonic saline/dextran (HSD), 7.5% NaCl/6% dextran-70. We tested the hypothesis that high arginine vasopressin (AVP) levels associated with severe hemorrhage may exacerbate the diuretic effect of HSD infusion in euvolemic sheep. Following AVP infusion, a significant bradycardia (55% of baseline) and decreased cardiac output (62% of baseline) was observed (p < or = .05). Urine output increased during AVP infusion (25.4 +/- 2.3 ml/20 min) compared to control group (10.5 +/- 1.0 ml/20 min) (p < or = .0001). With HSD volume expansion, urine flow in the AVP group was initially 1.7 times greater than the control group (104.8 +/- 10 ml/20 min vs. 60.2 +/- 15 ml/20 min) (p < or = .05). High serum levels of AVP (600 +/- 33 pg/ml) may contribute to the diuresis seen with HSD resuscitation and possibly contribute to the bradycardia observed with severe hemorrhage.

Animals↗

Effects of electrode size on basic excitatory responses and on selected stimulus parameters.

Recent data have implicated the size of surface electrodes as an important factor affecting peripheral nerve excitation. Therefore, we studied the effects of electrode size on the basic excitatory responses and on stimulus characteristics. Four different sizes of self-adhesive surface electrodes were applied over the medial and lateral gastrocnemius muscle of 20 healthy subjects. The excitatory levels were sensory threshold, motor threshold, pain threshold, and maximally tolerated painful stimulation. Stimulus parameters included a symmetric biphasic waveform, 200 microseconds phase duration, and a pulse repetition rate of 50 pps. Amplitude was increased until the appropriate excitatory response was achieved. At this amplitude level, the computerized recording system collected data of stimulus peak current, peak voltage, and phase charge as well as isometric plantar flexion force. Repeated measure analysis of variance and Newman-Keuls post hoc tests revealed that increasing electrode size significantly decreased voltage but increased current and phase charge magnitudes. With increasing electrode area, the ratios of voltage/current decreased nonlinearly, while the ratios of charge/voltage increased nonlinearly. The comfort of stimulation for the same amount of plantar flexion force improved significantly as electrode size became larger. We concluded that electrode size affects the stimulus parameters, comfort, and force generation associated with electrically induced excitatory responses. Electrode size should be considered an integral part of the attempt to improve subject response to transcutaneous electrical stimulation.

Adult↗

Splenic abscess in the intensive care unit.

BACKGROUND AND METHODS: From 1980 through 1990, nine patients developed de novo splenic abscess during their stay in our intensive care unit (ICU), representing the first series of such reported cases. RESULTS: All nine patients were septic prior to the diagnosis of splenic abscess. The signs and symptoms of splenic abscess commonly described in the literature were of little help in detecting this pathology in ICU patients. Mean +/- SD platelet count, however, increased significantly, from 274 x 10(9)/L +/- 50 x 10(9)/L at admission to 647 x 10(9)/L +/- 94 x 10(9)/L at diagnosis. At diagnosis, left pleural effusion was present in all patients. Only three patients had detectable left upper quadrant tenderness. Abdominal computed tomographic scans, when used, were diagnostic in all cases. All patients were treated by splenectomy; eight had a solitary abscess. Six abscesses were caused by enteric organisms, two by Staphylococcus aureus, and one by Streptococcus epidermidis. Eight patients (89%) had had the offending organism previously isolated from their blood or from another infected site. Mortality was 45%. CONCLUSIONS: Splenic abscess, although a rare clinical entity, does occur de novo in ICU patients and is associated with significant mortality. Unexplained thrombocytosis in a septic ICU patient with persistent left pleural effusion is suggestive of splenic abscess. Previous culture and sensitivity results are useful in guiding perioperative antibiotic choices.

Abscess↗