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Biomedical subjects

A W Holt

Publications and source records attributed to A W Holt.

16 recordsLinked to original sources
PubMed1998

Haemolysis associated with continuous venovenous renal replacement circuits.

Extracorporeal circuits can cause haemolysis resulting in an increase in plasma-free haemoglobin (PFHb). High pressures and clots within the circuit have been identified as factors increasing the likelihood of haemolysis. Continuous venovenous haemodiafiltration (CVVHD) is associated with high circuit pressures as the pump-driven circuit clots over a period of time. PFHb was measured during CVVHD to determine if circuit life, maximum circuit pressure or the clotting of the haemofilter was associated with evidence of haemolysis. Circuit life up to 50 hours, circuit pressures or haemofilter clotting had no significant effect on PFHb. There was a small rise in PFHb in the circuits lasting beyond 50 hours. CVVHD circuits can be run up to 50 hours without concern for haemolysis.

Acute Kidney Injury↗
PubMed1997

Treatment of a giant haemangioma of the liver with Kasabach-Merritt syndrome by orthotopic liver transplant a case report.

We describe a case of giant cavernous haemangioma of the liver with disseminated intravascular coagulopathy (Kasabach-Merritt syndrome) which was cured by orthotopic liver transplant. A 47 year old man presented with bleeding and tender massive hepatomegaly after tooth extraction. Investigations showed disseminated intravascular coagulopathy and a giant hepatic haemangioma involving both lobes of the liver. Initial treatment failed to resolve the coagulopathy and liver resection was attempted. At laparotomy the tumour was unresectable and the only option for cure was to offer a liver transplantation. The orthotopic liver transplant was performed 20 days after initial laparotomy. Subsequently, all coagulation parameters returned to normal and the patient remains well after 12 months. Orthotopic liver transplant can be considered for giant hepatic haemangioma with Kasabach-Merritt syndrome when resection is necessary and a partial hepatectomy is not technically feasible.

Disseminated Intravascular Coagulation↗
PubMed1996

Coordination of biliary and upper gastrointestinal motility in the fasted conscious pig.

A chronic pig model was developed which permits the simultaneous measurement of integrated biliary motility as resistance to flow (CBD inflow), gallbladder, duodenal and gastric motility in addition to collection of venous blood samples for gut hormones estimations. Animals displayed a duodenal interdigestive cycle of 55.4 +/- 3.4 min (mean +/- SEM, n = 6), consisting of phase I, II and III (21.2 +/- 2.1, 70.5 +/- 2.0, 8.7 +/- 0.5% of the cycle, respectively). A gastric interdigestive cycle of 60.2 +/- 6.5 min (n = 4) was similarly demonstrated consisting of three phases which corresponded to the three duodenal phases. The gastric phases I, II and III comprised 26.3 +/- 3.0, 71.2 +/- 2.7 and 2.5 +/- 0.8% of the cycle, respectively. The gastric phase III immediately preceded the onset of the duodenal phase III. The gallbladder likewise displayed an interdigestive cycle of 54.5 +/- 7.2 min (n = 6) consisting of a quiescent period (37.2 +/- 3.7% of the cycle) corresponding temporally to duodenal phase III and phase I. This quiescent phase was followed by a period of rhythmic contractions (64.5 +/- 4.1% of the cycle) which corresponded temporally to duodenal phase II. The onset of the gallbladder quiescent period coincided with the onset of duodenal phase III. The CBD inflow similarly demonstrated an interdigestive cycle of 53.4 +/- 9.6 min (n = 4) duration, consisting of three phases. The initial phase was evident as a period of rapid inflow, the onset of which coincided with the onset of duodenal phase III and the gallbladder quiescent period, and occupied 12.0 +/- 0.8% of the cycle. The second phase which occupied 18.0 +/- 7.4% of the cycle, was typified as a period of declining inflow which reached a relatively stable level at a time corresponding to the end of duodenal phase I. The third phase consisted of the maintenance of the inflow rate achieved at the end of the previous phase (60% of maximum inflow), corresponding in onset and duration with duodenal phase II and occupied 70.0 +/- 8.6% of the cycle. Plasma motilin levels fluctuated in relation to the duodenal interdigestive cycle, peaking during phase III relative to phase I (36.9 +/- 8.5 vs 25.4 +/- 7.7 pg mL-1, respectively, n = 5, P < 0.05). Cholecystokinin levels did not fluctuate, remaining low (2.3 +/- 2.1 pM cholecystokinin octapeptide equivalents, n = 5) throughout the duodenal interdigestive cycle, but increased about two fold after ingestion of solid food. Feeding disrupted the gastric, duodenal, gallbladder and CBD inflow cycles.

Animals↗
PubMed1996

Continuous renal replacement therapy in critically ill patients: monitoring circuit function.

There is currently no universally accepted method to monitor circuit function or guidelines for circuit replacement during continuous renal replacement therapies (CRRT). The objectives of this study were to diagnose the causes of circuit failure, identify factors responsible for circuit clotting and determine a predictive monitor of circuit function. The CRRT technique used in this study was continuous venovenous haemodialysis (CVVHD). Continuous monitoring of circuit pressures (pre- and post-haemofilter and their difference: the transfilter pressure gradient) was used to diagnose the causes of circuit failure. In circuits ceasing due to clotting, the factors thought to contribute, anticoagulation, haematocrit and platelet count, were measured at the commencement of CVVHD and every eight hours thereafter until circuit failure. Monitors of circuit function, creatinine clearance and plasma to diafiltrate urea ratio were measured every eight hours and compared to the transfilter pressure gradient. During a three-month period data was collected on five consecutive patients (41 consecutive haemofilters). Clotting of the haemofilter (63%) and air detection chamber (7.5%) were the most common identifiable causes of circuit failure. The duration of their circuit life was described using multiple regression analysis, i.e. hours of filter life = -82.8 + (delta platelet count x 0.25) + (delta haematocrit x 3.6) + (circuit flow [ml/min] x 4) R2 = 0.77. A rise in transfilter pressure gradient and a fall in haemofilter function discriminated clotted filters with falling function (decrease in creatinine clearance and urea ratio) from unclotted filters. In any circuit an increase of 26 mmHg or more in the transfilter pressure gradient accurately predicted circuit failure due to clotting and imminent cessation of function. Increases in platelet count, haematocrit, and low circuit flows are important determinants of haemofilter life. The measurement of transfilter pressure gradient across the haemofilter is an accurate bedside monitor of circuit function.

Acute Kidney Injury↗
PubMed1995

Vasoactive drugs and the importance of renal perfusion pressure.

Despite the often multifactorial nature of renal insults in critically ill patients, inadequate renal blood flow (RBF) is common and frequently causes a reduction in the glomerular filtration rate (GFR). Renal autoregulation acts to maintain both the RBF and GFR constant across a broad range of renal perfusion pressure (RPP) levels; however, the lower limit of this range (approximately 80 mm Hg for RBF, and 10-15 mm Hg higher for GFR) is often above the RPP achieved in critically ill patients. Furthermore, renal autoregulation is often lost, resulting in a linear pressure-flow relationship in the "at-risk" kidney. Consequently, maintenance of an adequate RPP level is needed to optimize RBF. While this may require the use of vasopressor catecholamines with their attendant risk of renal vasoconstriction and a reduction in RBF, both laboratory studies and clinical data suggest that such reactions rarely occur with intravenous infusions of these drugs, and that RBF and renal function usually improve when RPP is augmented during shock. Preliminary data, using nitric oxide (NO.) synthase inhibitors to augment blood pressure, showed a detrimental effect on renal perfusion, perhaps due to the central role of NO. in the normal vasoregulation of the kidney. Dopaminergic agonists have been commonly used as renal vasodilators; however, their actions are complex and include a proximal tubular diuretic effect, renal vasodilation, and systemic hemodynamic effects. Their specific action to increase RBF and GFR has not been demonstrated in clinically relevant studies and no prospective randomized study has shown a reduction in the incidence of renal impairment or acute renal failure.

Acute Kidney Injury↗
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↗
PubMed1992

Prospective evaluation of residents and nurses as severity score data collectors.

OBJECTIVES: To determine the interobserver reliability of residents and nurses collecting Acute Physiology and Chronic Health Evaluation (APACHE II) data and the subsequent effect of these data collections on individual patient mortality prediction. DESIGN: In a prospective study, residents and nurses independently collected data to derive APACHE II scores. When their scores differed, a standard score was determined by one of the investigators. SETTING: A general medical and surgical ICU. PATIENTS: A total of 120 consecutive patients were included; of these patients, 79 had standard scores determined because resident and nurse scores differed. MAIN RESULTS: There was overall agreement between the residents and nurses with no significant difference between mean APACHE II scores or mean predicted mortality rates. Intraclass correlation coefficients confirmed good overall agreement between observer groups for predicted mortality rate: resident vs. nurse r2 = .94, resident vs. standard r2 = .94, and nurse vs. standard r2 = .90. However, clinically significant lack of agreement was demonstrated in 5% of the patients by the 95% confidence limits of agreement: resident vs. nurse -14 to +14%, resident vs. standard -10 to +14%, and nurse vs. standard -14 to +20%. CONCLUSIONS: While interobserver variability between resident and nurse data collection has minimal effect on derived predicted mortality rate with large patient groups, significant variability may occur in individual patients. Residents were more accurate data collectors than nurses.

Data Collection↗
PubMed1991

Treatment of severe cardiogenic pulmonary edema with continuous positive airway pressure delivered by face mask.

BACKGROUND: Severe cardiogenic pulmonary edema is a frequent cause of respiratory failure, and many patients with this condition require endotracheal intubation and mechanical ventilation. We investigated whether continuous positive airway pressure delivered by means of a face mask had physiologic benefit and would reduce the need for intubation and mechanical ventilation. METHODS: We randomly assigned 39 consecutive patients with respiratory failure due to severe cardiogenic pulmonary edema to receive either oxygen alone or oxygen plus continuous positive airway pressure delivered through a face mask. It was not possible to blind the investigators to the assigned treatment. Physiologic measurements were made over the subsequent 24 hours, and the patients were followed to hospital discharge. RESULTS: After 30 minutes, both respiratory rate and arterial carbon dioxide tension had decreased more in the patients who received oxygen plus continuous positive airway pressure. The mean (+/- SD) respiratory rate at 30 minutes decreased from 32 +/- 6 to 33 +/- 9 breaths per minute in the patients receiving oxygen alone and from 35 +/- 8 to 27 +/- 6 breaths per minute in those receiving oxygen plus continuous positive airway pressure (P = 0.008); the arterial carbon dioxide tension decreased from 64 +/- 17 to 62 +/- 14 mm Hg in those receiving oxygen alone and from 58 +/- 8 to 46 +/- 4 mm Hg in those receiving oxygen plus continuous positive airway pressure (P less than 0.001). The patients receiving continuous positive airway pressure also had a greater increase in the arterial pH (oxygen alone, from 7.15 +/- 0.11 to 7.18 +/- 0.18; oxygen plus continuous positive airway pressure, from 7.18 +/- 0.08 to 7.28 +/- 0.06; P less than 0.001) and in the ratio of arterial oxygen tension to the fraction of inspired oxygen (oxygen alone, from 136 +/- 44 to 126 +/- 47; oxygen plus continuous positive airway pressure, from 138 +/- 32 to 206 +/- 126; P = 0.01). After 24 hours, however, there were no significant differences between the two treatment groups in any of these respiratory indexes. Seven (35 percent) of the patients who received oxygen alone but none who received oxygen plus continuous positive airway pressure required intubation and mechanical ventilation (P = 0.005). However, no significant difference was found in in-hospital mortality (oxygen alone, 4 of 20 patients; oxygen plus continuous positive airway pressure, 2 of 19; P = 0.36) or the length of the hospital stay. CONCLUSIONS: Continuous positive airway pressure delivered by face mask in patients with severe cardiogenic pulmonary edema can result in early physiologic improvement and reduce the need for intubation and mechanical ventilation. This short-term study could not establish whether continuous positive airway pressure has any long-term benefit or whether a larger study would have shown a difference in mortality between the treatment groups.

Aged↗
PubMed1989

Hemodynamic responses to amiodarone in critically ill patients receiving catecholamine infusions.

The hemodynamic response after an iv loading dose of amiodarone for resistant supraventricular tachyarrhythmias was studied in ten critically ill patients receiving a catecholamine infusion for shock. A loading dose of amiodarone, 3.7 to 5.0 mg/kg, was infused over 2 h while the catecholamine infusion dose requirements were monitored. There was a significant decrease in heart rate (mean 16%, p less than .01), and an increase in stroke volume index (mean 29%, p less than .01) and left ventricular stroke work index (mean 34%, p less than .01). Cardiac index, oxygen availability index, and mean arterial pressure were not changed significantly. The reported adrenoreceptor antagonism of amiodarone did not change catecholamine dose requirements in this study. In nine of ten patients, sinus rhythm was achieved and maintained. The loading dose of amiodarone had no significant acute effect on plasma digoxin concentrations. Despite good arrhythmia control, mortality was high.

Aged↗