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Biomedical subjects

L I Worthley

Publications and source records attributed to L I Worthley.

At least 19 recordsLinked to original sources
PubMed1995

Siggaard-Andersen algorithm-derived p50 parameters: perturbation by abnormal hemoglobin-oxygen affinity and acid-base disturbances.

The p50 and derived indexes, calculated by using the Siggaard-Andersen algorithm from a single measurement of arterial blood gas tensions and hemoglobin-oxygen saturation, are used to assess tissue oxygen availability in critical illness. We tested the accuracy of the Siggaard-Andersen p50 algorithm over a wide range of pathophysiologic conditions. Blood gases, cooximetry, and calculation of standard and in vivo p50 were performed at multiple saturations, CO2 tensions, and H+ concentrations on blood with normal (standard p50 of 26.1 and 26.7 mm Hg), increased (19.0 and 25.4), and reduced (33.9 and 38.2) hemoglobin-oxygen affinity, as well as on high-affinity blood from two patients with diabetic ketoacidosis (16.7 and 20.8). Log p50 in vivo/pH plots were constructed to determine the Bohr effect. Except in the normal affinity specimens (coefficient of variation < 1.7%), standard p50 values showed high variability (coefficient of variation > 5.9%), with saturation-linked bias and distortion of the Bohr effect. Standard p50 was overestimated by up to 11 mm Hg as saturation approached 97%. Although base deficit correction of the stored specimens (6.9 < pH < 7.1) restored the Bohr effect and improved the accuracy of standard p50 calculations (coefficient of variation = 4.4% and 2.9%), saturation-linked bias persisted. We conclude that Siggaard-Andersen p50 calculations may be misleading when there are disturbances of hemoglobin-oxygen affinity and acid-base balance, owing to changes in shape of the hemoglobin-dissociation curve. When metabolic acidosis occurs with high hemoglobin-oxygen affinity, as can occur in critical illness, indexes derived by the Siggaard-Andersen algorithm on arterial blood may greatly overestimate oxygen availability.

Acid-Base Imbalance↗
PubMed1994

Intensive care costing methodology: cost benefit analysis of mask continuous positive airway pressure for severe cardiogenic pulmonary oedema.

Costing data for intensive care admissions is important, not only for unit funding, but also for cost outcome analysis of new therapies. This paper presents an intensive care episode costing methodology using the example of a cost-benefit analysis of mask CPAP for severe cardiogenic pulmonary oedema (CPO). This analysis examines the intervention of admitting all patients with severe CPO to the intensive care unit for mask CPAP, compared with the previous practice of admitting only patients failing conventional non-CPAP treatment and requiring mechanical ventilation. The episode costs were determined from a prospective study which showed mask CPAP reduced the need for mechanical ventilation from 35% to 0%. The mean cost of a mask CPAP episode was $1,156, with a mean stay of 1.2 days, compared with ventilated patients, $5,055 and 4.2 days. The major contributors to cost in both groups were nursing and medical salaries, and hospital overheads. The cost of previous estimated yearly caseload of 35 ventilated patients ($176,925) was greater than the cost associated with an increased caseload of 100 mask CPAP patients ($115,600). We conclude that, despite an increase in admissions, mask CPAP for severe CPO is cost-effective.

Cost-Benefit Analysis↗
PubMed1993

Bronchial electrocardiography to determine left or right main bronchial placement of an endotracheal suction catheter tip.

OBJECTIVE: To assess the utility of a blue lined angle tipped and electrode tipped catheter, to guide left and right main bronchus cannulation. DESIGN: A prospective study. SETTING: An 11-bed general intensive care unit in a 900-bed teaching hospital. PATIENTS: 50 intubated intensive care patients, in sinus rhythm with normal P and QRS mean frontal axis, who required endobronchial suctioning for routine respiratory management. INTERVENTIONS: Endobronchial electrocardiography was used to position a blue lined angle tipped and electrode tipped suction catheter into the right and left main bronchi. RESULTS: Selective cannulation of the left main bronchi was determined by observing a biphasic or inverted P wave in 42 patients, or biphasic or inverted QRS complex in 31 patients. In 8 patients in whom no changes in the ECG were found, bronchoscopic placement of an ECG electrode into the left main bronchus demonstrated a biphasic or inverted P wave in 8 patients and a biphasic QRS complex in 3 patients, confirming the failure to cannulate the left main bronchus in these 8 patients. CONCLUSIONS: Using a blue lined, angle tipped and electrode tipped catheter for endotracheal suctioning, endobronchial electrocardiography may be a simple method to signal left or right main bronchus cannulation.

Arrhythmias, Cardiac↗
PubMed1992

Ventilation/perfusion indices do not correlate with the difference between oxygen consumption measured by the Fick principle and metabolic monitoring systems in critically ill patients.

OBJECTIVE: To determine whether the difference between oxygen consumption (VO2) measured by metabolic gas monitoring systems and by the Fick principle is related to venous admixture, deadspace/tidal volume ratio, or alveolar-arterial oxygen tension gradient in critically ill patients. DESIGN: A prospective study. SETTING: An 11-bed general ICU in a 900-bed teaching hospital. PATIENTS: Twenty critically ill patients admitted to the ICU who required mechanical ventilation, right heart catheterization, and arterial and mixed venous gas measurements for normal clinical management. RESULTS: Thirty-three recordings were analyzed. The mean VO2 measured by the metabolic gas monitoring system was 308 +/- 63.9 (SD) mL/min and was significantly greater than the mean VO2 measured by the Fick principle of 284 +/- 72.0 mL/min. The difference between the two measurements of 24.3 +/- 47.6 mL/min correlated poorly with venous admixture (r2 = .0009), dead-space/tidal volume ratio (r2 = .0064) and alveolar-arterial oxygen tension gradient (r2 = .017). CONCLUSIONS: If the difference in VO2 measured by metabolic gas monitoring systems and the Fick principle is due to intrapulmonary VO2 then in critically ill patients the ventilation/perfusion indices of venous admixture, deadspace/tidal volume ratio and alveolar-arterial oxygen tension gradient correlate poorly with intrapulmonary VO2.

Adult↗
PubMed1991

A prospective comparison of a percutaneous tracheostomy technique with standard surgical tracheostomy.

A prospective non-randomized study was undertaken to compare, in intensive care patients, the safety and utility of a percutaneous tracheostomy technique performed at the bedside with a surgical tracheostomy technique performed in the operating room. During a 21 month period, 153 percutaneous tracheostomies were performed. Complications occurred in 6 patients (3.9%). Secondary wound haemorrhage occurred in 4 patients and primary wound haemorrhage occurred in 2 patients. During the same period, 74 surgical tracheostomies were performed. Complications occurred in 14 patients (18.9%) which included tracheal obstruction, haemorrhage, pneumothorax, wound infection, wound breakdown and one death. In comparison to surgical tracheostomies, percutaneous tracheostomies were rapidly and easily performed at the bedside and were associated with significantly fewer complications.

Adolescent↗
PubMed1991

The P50 is reduced in critically ill patients.

A prospective study was designed to measure the P50 in 20 critically ill patients, and compare it with the P50 measured in 20 normal individuals. Arterial blood gases, lactate, haemoglobin (Hb) and phosphate (PO4) levels were also measured and compared with the P50 in the critically ill patients. The mean P50 of the critically ill patients was 24.5 mmHg (SD +/- 2.9) and was significantly lower than the mean P50 of 26.2 (SD +/- 2.2) in the normal individuals (p less than 0.05). In the critically ill patients, strong correlations were observed between the P50 and the arterial pH and base excess (BE) levels, with coefficients of 0.79 and 0.69 respectively whereas correlations between the P50 and arterial oxygen tension (PO2), carbon dioxide tension (PCO2), lactate, Hb and PO4 levels were poor, with correlations of 0.001, 0.008, 0.07, 0.13 respectively. It is concluded that the P50 is commonly reduced in critically ill patients, and has a strong correlation with arterial pH and BE.

Adult↗
PubMed1990

A simple percutaneous tracheostomy technique.

PCT techniques have significant advantages when compared with the standard techniques of tracheostomy. We have developed an instrument that facilitates the operation of PCT, which we found increased the simplicity and safety of the procedure.

Equipment Design↗
PubMed1988

Treatment of resistant intracranial hypertension with hypertonic saline. Report of two cases.

The authors describe two patients with traumatic cerebral edema and intracranial hypertension in whom the continued use of mannitol and furosemide resulted in a progressive lessening of the effect of these agents on the intracranial pressure (ICP) and caused prerenal failure. Intravenous administration of hypertonic saline (50 ml and 20 ml of a 5-mmol/ml saline solution over 10 minutes in Cases 1 and 2, respectively) produced a prolonged reduction in the ICP and improved renal function in both cases. It is suggested that if a reduction in ICP without diuresis is required in patients with traumatic cerebral edema, treatment with intravenous hypertonic saline should be considered.

Adolescent↗
PubMed1987

Adverse haemodynamic effects of sodium bicarbonate in metabolic acidosis.

In a patient with viral pneumonia, acute respiratory and renal failure and metabolic acidosis, a reduction in left ventricular stroke work was observed on the three occasions that 100 ml of 8.4% sodium bicarbonate was infused. Blood pressure and cardiac output decreased on two of the occasions. Since intravenous sodium bicarbonate may produce adverse cardiovascular effects, a right heart catheter should be inserted to monitor these effects when alkali therapy is administered to an acutely ill patient with metabolic acidosis.

Acidosis↗
PubMed1987

For calculating osmolality, the simplest formula is the best.

Plasma osmolalities were measured in 100 normal, 100 general hospital and 100 intensive care patients, and compared with the osmolalities calculated from the plasma concentrations of sodium, potassium, glucose and urea, using five different published formulae. The mean osmolar gaps in the 100 consecutive intensive care patients and the 100 general hospital patients were not significantly different from the mean osmolar gap in the 100 normal individuals. The formula which gave the least difference between the measured and calculated osmolality was 2 X Na + urea + glucose, where the concentrations of sodium, urea and glucose were measured in mmol/l.

Adult↗
PubMed1986

Treatment of hyponatraemic seizures with intravenous 29.2% saline.

Five patients with severe hyponatraemia and epileptiform seizures were given 50 ml of 29.2% saline (250 mmol) through a central venous catheter over 10 minutes to control seizures rapidly, reduce cerebral oedema, and diminish the incidence of permanent neuronal damage. The saline controlled seizures in all patients, increasing the mean serum sodium concentration by 7.4 (SD 1.14) mmol(mEq)/l and decreasing the mean serum potassium concentration by 0.62 (0.5) mmol(mEq)/l. Further saline and frusemide were then administered over 10 (2) hours, raising the serum sodium concentration by 2.14 (0.49) mmol/l/h until it reached 133 (2.35) mmol/l. A total of 790 (139) mmol saline was infused and a negative fluid balance of 3.34 (0.75) litres achieved. Four patients survived without neurological abnormality. One patient, who was not treated immediately and suffered a prolonged episode of status epilepticus, was left with a permanent neurological defect.

Adult↗
PubMed1986

Intravenous hydrochloric acid in patients with metabolic alkalosis and hypercapnia.

During a seven-year period, 15 patients admitted to an intensive care unit with a metabolic alkalosis resistant to saline and potassium chloride infusions and with an arterial pH of greater than 7.44 and arterial carbon dioxide pressure (PaCO2) of greater than 50 mm Hg, while breathing spontaneously, were given hydrochloric acid at 200 mmol/24 h through a central venous line until the arterial pH had decreased to less than 7.36 or PaCO2 had decreased to less than 40 mm Hg. Five patients without respiratory failure had a significant decrease in PaCO2, pH, bicarbonate Ion (HCO3-), and base excess (BE). Four patients with acute respiratory failure had a significant decrease in PaCO2, HCO3-, and BE and an increase in arterial oxygen pressure, indicating that in both of these patient groups alveolar ventilation had improved. Six patients with chronic respiratory failure had a significant decrease in pH, HCO3-, and BE, although there was no significant change in PaCO2, indicating that in this patient group alveolar ventilation could not be consistently increased in response to a reduction in arterial pH.

Acute Disease↗
PubMed1986

Hyperosmolar coma treated with intravenous sterile water. A study of three cases.

Three patients with hyperosmolar coma were treated with intravenous isotonic saline, dextrose, and hypotonic saline solutions. The development of pulmonary edema and increasing hypernatremia precluded the further use of sodium solutions, and the presence of severe hyperglycemia made the further use of dextrose solutions undesirable. To provide further solute-free fluid, intravenous sterile water was administered through a central venous catheter. The hyperosmolar state improved, and all patients survived without biochemical evidence of hemolysis or clinical evidence of cerebral edema.

Aged↗