Anaesthesia and Intensive Care

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 + (Δ platelet count x 0.25) + (Δ 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.

The cytokine cascade which is triggered by severe sepsis may contribute to progressive organ dysfunction and death from sepsis. This cascade may be accentuated by surgery for sepsis and pre-treatment with cytokine blockers could possibly ameliorate the response. This prospective controlled study determined the effect of surgery in 11 haemodynamically stable patients undergoing laparotomy for intra-abdominal sepsis. Serum levels of endotoxin, IL-1, IL-6, IL-8 and TNF-α were determined; blood cultures, features of systemic inflammatory response, and organ dysfunction were monitored over the perioperative period. There was considerable variation in the serum cytokine levels. The preoperative IL-6 levels were significantly elevated in the septic patients and a threefold increase in IL-6 levels occurred in both groups postoperatively. An increase in TNF-α did not achieve significance because of high levels in control patients with cancer. Cytokine release which occurs during abdominal surgery is increased in patients with intra-abdominal sepsis.

Dopexamine hydrochloride, a synthetic dopamine analog with predominantly beta and delta agonist properties, has been shown to improve cardiac performance and renal function in adults with heart failure. This study was designed to investigate the haemodynamic and renal effects of dopexamine in children after cardiac surgery. Seven children were selected in whom a need for postoperative vasodilation after cardiac surgery was anticipated. Haemodynamics and renal function were determined under baseline conditions and during a continuous infusion of dopexamine at 2 and 6 μg.kg^-1.min^-1 for 90 minutes, the sequence being randomized for the initial dose. Cardiac output was measured by thermodilution and glomerular filtration rate (GFR) and renal plasma flow (RPF) by the clearances of inulin and para-aminohippurate respectively. Dopexamine induced a dose-related increase in cardiac index (CI) expressed as mean (SD) from 3.5 (0.7) to 3.9 (0.76) and 4.5 (0.8) l.min.^-1m^-2 (both P<0.05), and in heart rate (HR) from 107 (17) to 122 (17) and 136 (17) beats.min^-1 (P<0.05). Stroke volume index (SVI) and mean systemic pressure were unchanged, but pulmonary wedge pressure decreased from 14 (3) to 11 (4) and 12 (3) mmHg (both P<0.05). Systemic vascular resistances (SVR) decreased from 24 (7) to 20 (5) mmHg.l^-1.min^-1.m^-2 (P<0.05), with dopexamine 6 μg.kg^-1.min^-1. Renal blood flow (RBF) increased from 319 (113) to 441 (230) and 410 (138) ml.min^-1.m^-2 (both P<0.05), GFR from 115 (32) to 142 (34) and 146 (29) ml.min^-1.1.73m^-2 (both P<0.05), urine output and fractional excretion of sodium respectively from 3.12 (2) to 7.16 (8) and 7.21 (6) ml.kg^-1 (both P<0.05) and from 2.24 (1) to 4.25 (3.4) (P<0.05) and 3.15 (3.1)% (n.s.). The fraction of CI delivered to the kidneys, the fraction of RBF filtered in the kidneys, plasma renin activity and aldosterone levels remained unchanged. In children after cardiac surgery, dopexamine increases CI at the expense of a concomitant increase in heart rate and demonstrates few selective vascular systemic or intrinsic renal actions.

We describe an outbreak of hepatitis A that occurred in an Intensive Care Unit (ICU) in a regional hospital in North Queensland. Seven people were infected including two patients, two close contacts of the index patient and three ICU nursing staff. The index case was admitted with an overdose and multiple trauma; he was not suspected to be incubating hepatitis A. The outbreak was initiated as a result of inadequate precautions taken whilst handling the index patient's bile. Problems identified upon reviewing the outbreak were inadequate terminal cleaning of equipment, food consumption in the ICU and inadequate handwashing practices. Implementation and maintenance of standard infection control practices is vital if further outbreaks of hospital-acquired hepatitis A and other enteric infections are to be avoided. We also suggest that the inactivated hepatitis A vaccine be considered for ICU staff.

The time-course of propofol concentrations in the blood and brain following rapid administration of three doses were examined using a sheep preparation and regional pharmacokinetic techniques. These were compared to the time-course of cerebral effects of propofol reported previously. There were marked differences between the time-course of propofol concentrations in arterial blood and the brain, with a close relationship between the time-course of brain concentrations and effects on depth of anaesthesia and CBF. There was evidence that the effect of propofol on cerebral blood flow altered its own rate of elution from the brain. Hysteresis between arterial propofol concentrations and cerebral effects following rapid IV administration therefore appears to have a pharmacokinetic basis, and conventional compartmental pharmacokinetic analysis using blood concentrations alone may fail to accurately predict the time-course of both brain propofol concentrations and depth of anaesthesia.

Two hundred consecutive, minimally-sedated patients presenting for upper limb surgery were audited prospectively to determine the overall clinical success rate, extent of cutaneous neural blockade, reliability and complication rate of each indicator of axillary sheath entry, and degree of patient satisfaction. The axillary sheath was identified, using a 22 gauge, short-bevelled needle, by one of four indicators, whichever was elicited first (paraesthesia, arterial or venous puncture, or tethering by the axillary sheath). Alkalinized mepivacaine 1.2%, 50 ml then was injected. The cutaneous distribution of the block was mapped in the presence of minimal sedation. Anaesthesia was supplemented with peripheral nerve blocks where necessary. Patients were followed up with a mailed questionnaire and surgeon interview. The overall clinical success rate was 92.5%, improving to 99% with supplementary nerve blocks. Complete anaesthesia distal to the elbow was achieved in 85% of patients. Complications were common, but generally mild and transient: mild acute local anaesthetic toxicity, 3.5%; axillary tenderness and bruising, 12%; and dysaesthesias, 12.5%. Despite this, patient satisfaction was high (97%).

The mucopolysaccharidoses are a group of inherited disorders of metabolism, with varying clinical manifestations. A number of them present anaesthetic difficulties. This paper presents a summary table of the syndromes and reviews our experience over ten years with patients with these diagnoses. The clinical presentations, anaesthetic management, and complications are described. The effect of age and diagnosis on airway difficulties was studied. There were 31 patients, 28 of whom required anaesthesia, on a total of 99 occasions, for 115 procedures. The patients with Hunter, Hurler and Maroteaux-Lamy syndromes had significantly more airway difficulties as they grew older, and compared with patients in this group with other syndromes. Patients with Hurler's syndrome may have coronary artery involvement and one patient was given fentanyl and pancuronium for this reason. He proved impossible to intubate and an emergency tracheostomy was performed.

We performed an audit of booked and unbooked admissions to a paediatric intensive care unit (PICU) after anaesthesia over a 19 month period in order to determine whether unbooked admissions were predictable, or whether there were any preventable anaesthetic factors responsible for PICU admission, and to evaluate the necessity of PICU admission in all study patients. Data was collected from the PICU database and from the medical records, especially the anaesthesia records, of unbooked admissions. There were 640 admissions to the PICU from the operating theatres, with 35 (5%) unbooked. Of the unbooked admissions, 71% were considered predictable and 20% had preventable features. There was an appropriate use of intensive care resources by these unbooked patients, with 77% having PICU-specific therapies (compared with 88% of booked cases). This quality assurance tool was relatively easy to perform, however it has numerous limitations hampering future routine use.

This study compared two bedside methods recommended for the detection of low concentrations of heparin and the activated partial thromboplastin time (APTT), with reference to a laboratory measure of heparin concentration. Patients undergoing cardiopulmonary bypass had blood drawn at four stages when low levels of heparin could be expected. At each stage four tests were performed: whole blood clotting time using a Hemochron analyser with a Saline-Rinsed test cartridge, whole blood clotting time using a Hemotec analyser with a High Range Heparinase test cartridge, APTT, and heparin concentration by polybrene neutralization. Thirty patients were studied. The sensitivity of the Saline-Rinsed Hemochron, Hemotec High Range Heparinase, and APTT in detecting concentrations of heparin less than 1 U/ml was 38%, 40% and 97%, respectively, while specificities were 87%, 90%, and 30%, respectively. Neither the Saline Rinsed Hemochron, nor the Hemotec Heparinase cartridge reliably detected concentrations of heparin less than 1 U/ml.

Patients sometimes notice an onion or garlic taste before losing consciousness with thiopentone. An assessment of 113 patients revealed that 42% of patients noticed this taste. The effect was observed less in older patients. There was no statistically significant difference in the incidence between men and women. Premedicated patients had a lower incidence, but this was explained by the greater proportion of older patients receiving a premedication. If the taste effect of thiopentone is genetically determined then it is a different gene to thiocarbamate which has about 75% tasters.