Biomedical subjects
Publications and source records attributed to B M Power.
We tested the utility of intratracheal carbon dioxide monitoring (IT-CO2) in 10 patients undergoing percutaneous dilatational tracheostomy (PDT). We have found IT-CO2 monitoring reliable in confirming the correct position of the tracheal cannula prior to tracheal dilatation using the Portex technique.
Tu's cardiac surgical risk prediction index for a Western Australian population was examined in a prospective observational cohort study. Risk score and outcome data were collected for 367 consecutive patients. Logistic regression analysis for Tu score prediction of hospital mortality and linear regression analysis for prediction of ICU and hospital stays were performed. The Tu index accurately predicted mortality rates (P = 0.002, odds ratio 1.46). The linear regression analyses of Tu score on ICU and hospital stays showed an excellent fit (P = 0.0001). The area under the receiver-operating characteristic curve for prolonged ICU stay was 0.75. The Tu risk index is valid for a Western Australian cardiac surgical population and practice.
The pulmonary circulation and the mechanisms which generate pulmonary hypertension are reviewed. The role of these mechanisms in the common pulmonary hypertensive states are analysed, particularly those in acute lung injury. Management options are discussed, with particular emphasis on the use of selective pulmonary vasodilators.
Critically ill patients exhibit a range of organ dysfunctions and often require treatment with a variety of drugs including sedatives, analgesics, neuromuscular blockers, antimicrobials, inotropes and gastric acid suppressants. Understanding how organ dysfunction can alter the pharmacokinetics of drugs is a vital aspect of therapy in this patient group. Many drugs will need to be given intravenously because of gastrointestinal failure. For those occasions on which the oral route is possible, bioavailability may be altered by hypomotility, changes in gastrointestinal pH and enteral feeding. Hepatic and renal dysfunction are the primary determinants of drug clearance, and hence of steady-state drug concentrations, and of efficacy and toxicity in the individual patient. Oxidative metabolism is the main clearance mechanism for many drugs and there is increasing recognition of the importance of decreased activity of the hepatic cytochrome P450 system in critically ill patients. Renal failure is equally important with both filtration and secretion clearance mechanisms being required for the removal of parent drugs and their active metabolites. Changes in the steady-state volume of distribution are often secondary to renal failure and may lower the effective drug concentrations in the body. Failure of the central nervous system, muscle, the endothelial system and endocrine system may also affect the pharmacokinetics of specific drugs. Time-dependency of alterations in pharmacokinetic parameters is well documented for some drugs. Understanding the underlying pathophysiology in the critically ill and applying pharmacokinetic principles in selection of drug and dose regimen is, therefore, crucial to optimising the pharmacodynamic response and outcome.
We report a survey of 196 consecutive central venous catheters (CVCs) placed in 151 patients in the Intensive Care Unit (ICU) over a ten-month period. Over this time the use of a new antiseptic-impregnated triple lumen CVC (Arrowgard Blue, Arrow International Inc., Pennsylvania, U.S.A.) was alternated on a bimonthly basis with the standard triple-lumen CVC (Arrow International Inc., Pennsylvania, U.S.A.). The overall rate of CVC tip infection was lower in the impregnated CVC group (15.6% vs 30.9%, P < 0.05). The impregnated CVC group had a much lower cumulative infection rate when the dwell time in patients was five days or less (3.3% vs 26.9%, P < 0.05). However, the difference between the cumulative infection rate was not statistically significant (P > 0.05) for dwell times of 6, 7 or 8 days respectively. There was no difference in the CVC related bacteraemia rates between the two groups (3.9% vs 3.7%, P > 0.05).
Percutaneous dilational tracheostomy (PDT), first described in the 1950s, has become a common bedside technique in the Intensive Care Unit (ICU). This study compares the early complications associated with the use of the Ciaglia PDT (Cook Critical Care, Bloomington, USA) technique, with the newly available Portex PDT technique (Portex Ltd., UK). The Ciaglia technique was adopted in this ICU in July 1994 and twenty-nine patients had a tracheostomy using this set until January 1995. Complications during the procedure were collected prospectively. When the Portex PDT set became available in January 1995, it was decided to assess the complication rate of this technique and compare them to the previously-collected data using the Ciaglia PDT set. Twenty-five patients have had a tracheostomy using the Portex PDT set. There has been no mortality associated with either PDT set. Bleeding requiring intervention occurred in two patients in the Ciaglia group and three patients in the Portex Group. All these patients had a bleeding diathesis. Loss of airway control occurred on one occasion in the Ciaglia group due to premature removal of the endotracheal tube. The first routine tracheostomy tube change at day 7 was complicated in four cases in the Ciaglia group. One infected stoma was noted in the Ciaglia group at day 7. Both techniques result in rapid, safe placement of a tracheostomy tube in critically ill patients in the ICU, obviating the need for surgical referral and transport to the operating room.
Explore the source record for details and available documents.
In a randomized, double-blind, controlled study of 98 patients with atrial fibrillation (AF) (present for > or = 30 minutes, < or = 72 hours, and a ventricular response of > or = 100 beats/min), intravenous flecainide (2 mg/kg, maximum 150 mg) was compared with intravenous amiodarone (7 mg/kg) and placebo. Exclusion criteria included significant left ventricular dysfunction, inotrope dependence, recent antiarrhythmic therapy, hypokalemia, and pacemaker dependence. Reversion to stable sinus rhythm within 2 hours of starting medication was considered likely to be due to drug effect. Twenty of 34 patients (59%) given flecainide, 11 of 32 (34%) given amiodarone, and 7 of 32 (22%) given placebo reverted to stable sinus rhythm in < or = 2 hours after starting medication (chi-square 9.87, p = 0.007). More patients reverted to stable rhythm with flecainide than with placebo (p = 0.005; odds ratio 5.1, 95% confidence interval 1.54 to 17.5). There was no significant difference between amiodarone and placebo or between flecainide and amiodarone. However, after 8 hours there were no significant differences in reversion between the treatment groups: flecainide (n = 23, 68%), amiodarone (n = 19, 59%), and placebo (n = 18, 56%). Amiodarone promptly reduced the ventricular rate, and this effect was maintained for 8 hours in those whose reversion to stable sinus rhythm was unsuccessful: flecainide was no more effective than placebo in controlling ventricular rate. Adverse effects were not significantly different in the 3 groups. Thus, intravenous flecainide results in earlier reversion of AF than does intravenous amiodarone or placebo. Amiodarone, although less effective in reverting AF, slows the rapid ventricular response.(ABSTRACT TRUNCATED AT 250 WORDS)
The profound physiological disturbances associated with severe intracerebral pathology have long been recognized. These changes have also been described in the brain dead potential organ donor but have only been studied since the early 1980s. Physiological disturbances in the brain dead organ donor result in a diffuse vascular regulatory injury and a diffuse metabolic cellular injury. The net result of these changes is an inexorable deterioration of all organs and eventual "cardiovascular death" of the patient. This paper reviews these physiological changes and the effect they may have on solid transplantable tissues, and discusses the management of brain dead organ donor with regard to these changes. Current concepts of brain death and how they may affect the interpretation of the observed physiological changes are also reviewed.
Explore the source record for details and available documents.
Antidepressant drugs are among the most commonly encountered causes of self-poisoning. These drugs include tricyclics, tetracyclics, bicyclics and monocyclics, as well as monoamine oxidase (MAO) inhibitors and selective serotonin reuptake inhibitors (SSRIs). Of these, the tricyclic antidepressants (TCAs) are generally more toxic in overdose, with major toxicity usually manifesting within the first 6 hours after overdose. Various studies indicate that patients at risk of toxicity from TCA overdose may be identified by neurological, cardiovascular and electrocardiography status, together with a quantitative estimate of the plasma drug concentration. While there are various methods available for such chemical estimations, the most satisfactory appears to be fluorescence polarisation immunoassay which gives rapid quantitative results for a variety of TCAs. The selective MAO-A inhibitor antidepressants and the SSRIs are relatively nontoxic when taken alone. However, overdoses of combinations of MAO inhibitors and either SSRIs or TCAs with serotonin reuptake blocking activity may result in a serotonin syndrome with a severe or fatal outcome. Features of this syndrome include hyperpyrexia, disseminated intravascular coagulation, convulsions, coma and muscle rigidity, which may not develop until 6 to 12 hours after overdose. While quantitative chemical identification of these drugs following overdose is helpful in confirming the diagnosis, it is not mandatory. The increasing use of MAO-A inhibitors and SSRIs in the treatment of depression suggests that careful clinical observation is required when combination overdoses are suspected.
1. The in vivo disposition of lupanine and 13-hydroxylupanine was studied in subjects identified as poor metabolizers (PM, n = 4) and extensive metabolizers (EM, n = 7) phenotypes for cytochrome P4502D6 (CYP2D6). 2. After oral administration (40.26 mumol), the half-life (t1/2) of lupanine determined from urinary excretion rate studies in EM subjects was 6.2 +/- 0.5 h (mean +/- SEM) with 95.5 +/- 6.0% of the dose recovered unchanged within 72 h. Similarly, in PM subjects t1/2 = 6.5 +/- 0.9 h and recovery 89.9 +/- 4.5%. 3. For orally administered 13-hydroxylupanine (37.83 mumol) the t1/2 in EM subjects was 6.8 +/- 1.0 h with a recovery of 100.5 +/- 5.3%, and in PM subjects t1/2 = 5.9 +/- 1.6 h with a recovery of 102.5 +/- 4.8%. 4. The t1/2s of both lupanine and 13-hydroxylupanine respectively did not differ significantly between EM and PM phenotypes. In addition, total recovery of dose for both alkaloids was similar between phenotypes. 5. In most subjects, > 76% of lupanine and > 85% of 13-hydroxylupanine was recovered as the unchanged compound. Significant apparent partial dehydroxylation of 13-hydroxy-lupanine was observed in one EM (14% of dose) and one PM (34% of dose) subject. 6. Overall, the finding of a high urinary recovery of unchanged lupanine or 13-hydroxylupanine together with similar t1/2s for both alkaloids in EM and PM CYP2D6 phenotypes suggests that clinical toxicity is unlikely to result from the use of lupin seed in footstuffs.
OBJECTIVE: To assess the role of intravascular atrial electrograms in improving the diagnosis of complex cardiac arrhythmias in critically ill patients. DESIGN: Prospective, clinical study comparing the accuracy of cardiac rhythm diagnosis using standard surface electrocardiogram (EKG) and intravascular atrial electrograms. SETTING: Intensive care unit of a university teaching hospital. PATIENTS: A total of 57 critically ill patients (44 cardiothoracic surgery, five acute myocardial infarction, two septic shock, six miscellaneous) with 85 complex cardiac arrhythmias that were unable to be diagnosed with certainty using the surface EKG. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The intravascular atrial electrogram altered diagnosis based on the surface EKG in 11 (13%) patients and confirmed rhythm diagnosis in 60 (71%) of 85 patients with arrhythmia. Of 61 patients with wide complex tachycardia, 40 (66%) were diagnosed as ventricular tachycardia (atrioventricular dissociation demonstrated on the atrial electrogram), and 11 (18%) as supraventricular tachycardia with aberrant conduction. Ten (16%) wide complex tachycardias could not be diagnosed with confidence using both surface EKG and intravascular electrogram. There were no adverse effects with this technique. CONCLUSIONS: Intravascular atrial electrograms recorded via central venous catheters are useful in the diagnosis of complex cardiac arrhythmias, particularly ventricular tachycardia. The technique is safe, simple, and quick.
Explore the source record for details and available documents.
Explore the source record for details and available documents.