Closed-loop control of blood glucose levels in critically ill patients

A closed-loop control system was constructed for automatic intravenous infusion of insulin to control blood sugar levels (BSL) in critically ill patients. We describe the development of the system. A total of nine subjects were recruited to clinically test the control system. In the patients who underwent closed-loop control of BSL, the controller managed to control only one patient's glycaemia without any manual intervention. The average BSL attained during closed-loop control approached the target range of 6-10 mmol/l, and had less deviation than when BSL had been maintained manually. We conclude that closed-loop BSL control using a sliding scale algorithm is feasible. The main deficiency in the current system is unreliability of the subcutaneous glucose sensor when used in this setting. This deficiency mandates high vigilance during use of the system as it is being developed.

Elective awake intubation in a patient with massive multinodular goitre presenting for radioiodine treatment

We present the management of the potential airway complications in a case of massive multinodular goitre treated with radioactive iodine. The patient's trachea was prophylactically intubated, using a fibreoptic technique, to prevent further airway compromise due to thyroid oedema following radioactive iodine treatment. He remained awake and intubated for five days and was extubated when there was no clinical evidence of thyroid oedema as a consequence of his treatment. This approach avoided the considerable risk of thyroidectomy in a morbidly obese patient with airway obstruction. To the authors' knowledge this approach has not been previously described.

Adult-to-adult living donor liver transplantation for fulminant hepatic failure

The outcome of fulminant hepatic failure without timely liver transplantation is poor. We describe a 19-year-old woman with fulminant hepatic failure due to acute hepatitis B infection who received a living donor liver transplant from her sister. The donor's recovery was uneventful, allowing hospital discharge on Day 6. Two months after transplantation the recipient developed a biliary stricture requiring surgery. One year after transplantation, her liver function was normal.

Clinical evaluation of the non-invasive cardiac output (NICO) monitor in the intensive care unit

The Non-invasive Cardiac Output (NICO) monitor (Novametrix Medical Systems Inc., Wallingford, CT, U.S.A.) utilizes a minimally-invasive partial rebreathing method to determine cardiac output by means of a differential form of the Fick equation. We evaluated the NICO monitor by comparing its output to paired measurements obtained by the standard thermodilution (TD) technique in patients who had recently undergone cardiac surgery. Forty-two paired measurements were carried out in 12 patients. The correlation between the two methods was moderate with a correlation coefficient of 0.691. Repeated measures ANOVA showed that TD measures of cardiac output were significantly higher than those obtained by the NICO monitor (P = 0.0003). Comparison of the two techniques using the method described by Bland and Altman showed decreased correlation at higher values of cardiac output. We conclude that the NICO monitor may well have a place in intensive care monitoring, provided patients are not breathing spontaneously and are able to tolerate a 4 mmHg rise in PaCO2. It is less suitable for use in patients with a high cardiac output state.

Pulmonary toxicity of inhaled aerosolized prostacyclin therapy--an observational study

Large white/landrace piglets (mass 11 to 21 kg) were exposed to aerosolized alkaline glycine diluent (n = 2) or inhaled aerosolized prostacyclin (n = 2) for five to eight hours. Pigs receiving these aerosols developed mild acute sterile tracheitis, involving the superficial layers of the trachea, shown histologically and ultrastructurally. Pigs receiving the diluent aerosol also showed mild inflammatory changes in the bronchioles. These findings suggest caution with the use of high volumes of aerosolized alkaline glycine diluent during inhaled aerosolized prostacyclin therapy.

The use of end-tidal carbon dioxide monitoring to confirm intratracheal cannula placement prior to percutaneous dilatational tracheostomy

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.

Dose-response to inhaled aerosolized prostacyclin for hypoxemia due to ARDS

STUDY OBJECTIVES

This study was carried out to determine the efficacy of and dose-response relationships to inhaled aerosolized prostacyclin (IAP), when used as a selective pulmonary vasodilator (SPV) in patients with severe hypoxemia due to ARDS.

DESIGN

Unblinded, interventional, prospective clinical study.

SETTING

A general ICU in a university-affiliated, tertiary referral center.

PATIENTS

Nine adult patients with severe ARDS (lung injury score, > or = 2.5).

INTERVENTIONS

All patients received IAP over the dose range 0 to 50 ng/kg/min. The IAP was delivered via a jet nebulizer placed in the ventilator circuit. Dose increments were 10 ng/kg/min every 30 min.

MEASUREMENTS AND RESULTS

Cardiovascular parameters (cardiac index and mean pulmonary and systemic pressures), indexes of oxygenation (PaO(2)/fraction of inspired oxygen [FIO(2)] ratio and alveolar-arterial oxygen partial pressure difference [P(A-a)O(2)]) and shunt fraction were measured or calculated at each dose interval, as were platelet aggregation and systemic levels of prostacyclin metabolite (6-keto prostaglandin F1(alpha)). A generalized linear regression model was used to determine a dose effect of IAP on these parameters. The Wilcoxon rank sum test for related measures was used to compare the effects of various doses of IAP. IAP acted as an SPV, with a statistically significant dose-related improvement in PaO(2)/FIO(2) ratio (p = 0.003) and P(A-a)O(2) (p = 0.01). Systemic prostacyclin metabolite levels increased significantly in response to delivered IAP (p = 0.001). There was no significant dose effect on systemic or pulmonary arterial pressures, or on platelet function, as determined by platelet aggregation in response to challenge with adenosine diphosphate.

CONCLUSIONS

IAP is an efficacious SPV, with marked dose-related improvement in oxygenation and with no demonstrable effect on systemic arterial pressures over the dose range 0 to 50 ng/kg/min. Despite significant systemic levels of prostacyclin metabolite, there was no demonstrable platelet function defect.

Extracorporeal circulatory support in near-fatal flecainide overdose

Flecainide, a class 1c antiarrhythmic, has a high mortality associated with significant overdose. We report the case of a 20-year-old female who took approximately 4 grams of flecainide and a small amount of paracetamol as an impulsive gesture. Circulatory failure unresponsive to pacing, inotropes and sodium bicarbonate was successfully treated with cardiopulmonary bypass (CPB). Resolution of her myocardial failure occurred over 24 hours and she was weaned from CPB 30 hours after its initiation. Coagulopathy and intravascular haemolysis were apparent during bypass and necessitated substantial use of blood products. Ischaemic renal dysfunction manifested early in her admission and required haemodiafiltration. Despite a prolonged period of unresponsiveness and pupillary dilatation during resuscitation and CPB she made a full recovery. We believe this is the first reported case of flecainide overdose, requiring extracorporeal circulatory support, not resulting in neurological deficit.

Late outcome from percutaneous tracheostomy using the Portex kit

OBJECTIVE

To assess late outcome following percutaneous tracheostomy using the Portex kit (Hythe, Kent, UK).

DESIGN

Prospective observational cohort study.

SETTING

Teaching hospital.

PATIENTS

Forty-nine consecutive patients who underwent percutaneous tracheostomy in the ICU using the Portex kit and who survived 6 months after the procedure.

INTERVENTIONS

Questionnaires regarding six symptoms were sent to all 49 surviving patients; the 39 respondents were invited to attend for review. Thirteen patients underwent pulmonary function testing, of whom 10 also underwent fiberoptic laryngotracheoscopy under local anesthesia.

RESULTS

The most common symptom was a minor change in voice. One patient had required treatment for symptomatic tracheal stenosis by the time of review; one was referred for revision of a tethered scar. Pulmonary function testing was easily performed by all patients and revealed no evidence of upper airway obstruction. Tracheoscopy likewise showed no evidence of tracheal stenosis.

CONCLUSIONS

One of 49 patients had developed tracheal stenosis. None of the patients attending for detailed review showed any sign of late complications other than one tethered scar.

Validation of Tu's cardiac surgical risk prediction index in a Western Australian population

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.

Contamination of propofol infusions in the intensive care unit: incidence and clinical significance

Epidemics of bacteraemia and wound infection have been associated with the infusion of bacterially contaminated propofol administered during anaesthesia. We conducted an observational study to determine the incidence and clinical significance of administration of potentially contaminated propofol to patients in an ICU setting. One hundred patients received a total of 302 infusions of propofol. Eighteen episodes of possible contamination of propofol syringes were identified, but in all cases contamination was by a low-grade virulence pathogen. There were no episodes of clinical infection or colonization which could be attributed to the administration of contaminated propofol. During the routine use of propofol to provide sedation in ICU patients the risk of nosocomial infection secondary to contamination of propofol is extremely low.

Pharmacokinetics of drugs used in critically ill adults

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.

Systemic levels of 6-keto-prostaglandin F1 alpha following administration of inhaled aerosolized prostacyclin

A case is described where systemic levels of prostacyclin metabolite were measured during inhaled aerosolized prostacyclin (IAP) therapy for severe hypoxaemia in a patient with the acute respiratory distress syndrome. Comparable levels of prostacyclin metabolite have been associated with a marked platelet aggregation defect in vitro. A platelet aggregation defect was also demonstrated in vivo in this patient. Haemodynamic and gas exchange data during the IAP therapy are described.

Infection in central lines: antiseptic-impregnated vs standard non-impregnated catheters

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).

Effect of low concentrations of prostacyclin on platelet function in vitro

The study was performed to determine the possible direct effects of low concentrations of prostacyclin that might spill over into the systemic circulation during the administration of inhaled aerosolized prostacyclin. Platelet aggregation in response to adenosine diphosphate and collagen, as well as measurement of the maximum amplitude of the thrombelastograph (TEG), was undertaken in vitro using venous blood exposed to low concentrations of prostacyclin (0, 10, 100 and 500 pg/ml) from eight healthy volunteers. There were statistically significant reductions in parameters of platelet aggregation in response to the agonists adenosine diphosphate (1 mumol/l and 8 mumol/l) and collagen (10 mumol/l) following exposure to as little as 10 pg/ml of prostacyclin. The maximum amplitude of the TEG was unchanged over the entire range of prostacyclin concentrations studied. The results indicate that low concentrations of prostacyclin or prostacyclin metabolite such as may be observed during inhaled aerosolized prostacyclin therapy are likely to be associated with a marked platelet aggregation defect. This defect was not detected by the TEG.

Central venous catheters revisited--infection rates and an assessment of the new Fibrin Analysing System brush

Sixty-one consecutive patients in the Intensive Care Unit requiring central venous lines (CVC) for five or more days were randomized to receive either a standard triple lumen CVC (STD/CVC) or a silver sulphadiazine and chlorhexidine impregnated CVC (SSD/CVC). Data from the 54 patients who completed the trial show a reduced infection rate (positive tip culture) in the SSD/CVC group (4 out of 28) compared to the STD/CVC group (10 out of 26) (P < 0.05). In addition, the new Fibrin Analysing System (FAS) brush was evaluated and used to determine the presence of infection in all the CVCs (STD/CVC and SSD/CVC combined, n = 54) at day 3 (i.e. early warning of CVC colonization/infection) and at the time of removal of the CVC. The FAS brush was able to detect an infected CVC on only one occasion on day 3 out of the 14 CVC tips which were later found to be colonized/infected at the time of removal. The sensitivity of the FAS brush in detecting colonized/infected CVCs at the time of CVC removal compared with CVC tip culture was 21% with a specificity of 100%. These findings would currently not support the routine use of the FAS brush in determining CVC infection/colonization.

The use of inhaled aerosolized prostacyclin (IAP) in the treatment of pulmonary hypertension secondary to pulmonary embolism

OBJECTIVE

To describe the use of inhaled aerosolized prostacyclin (IAP) in a patient with life-threatening pulmonary hypertension secondary to pulmonary embolism and to discuss the possible use of inhaled prostacyclin in the management of pulmonary embolism.

DESIGN

Case report.

SETTING

Intensive care unit of a university teaching hospital.

PATIENTS

One patient with severe pulmonary hypertension secondary to acute-on-chronic pulmonary embolism.

INTERVENTIONS

Conventional medical management of massive pulmonary embolism and inhaled aerosolized prostacyclin (IAP).

MEASUREMENTS AND RESULTS

Description of clinical course, haemodynamic data and gas exchange data.

CONCLUSIONS

We describe a patient with massive pulmonary embolism for whom the addition of IAP to his therapy appeared to result in a transient improvement in pulmonary haemodynamics and gas exchange.

Bronchoscopic insufflation of room air for the treatment of lobar atelectasis in mechanically ventilated patients

Segmental and lobar pulmonary atelectasis is a common occurrence in mechanically ventilated patients. Standard therapy for atelectasis relies on positive pressure ventilation, positive and expiratory pressure (PEEP), tracheobronchial toilet and regular chest physiotherapy. Various adjuncts to physiotherapy such as bronchoscopic clearance of secretions have not proved to be of additional benefit. Bronchoscopic clearance of secretions followed by insufflation of room air at 30 cm H2O into the atelectatic segment was employed on ten occasions in mechanically ventilated patients. Rapid re-expansion of the collapsed segment or lobe occurred in seven out of the ten treatments.

Death by tanning--a case of fatal basic chromium sulphate poisoning

A woman ingested 400 ml of leather tanning solution containing 48 g of basic chromium sulphate (CrOHSO4). This substance forms hydrogen ions and trivalent chromium when it reacts with tissue proteins. The patient died of cardiogenic shock, complicated by pancreatitis and gut mucosal necrosis and haemorrhage. There are no reported cases of toxicity due to oral ingestion of trivalent chromium. Toxicity of hexavalent and trivalent chromium is discussed and suggestions made for management of future cases.

Rapid inhalational induction of anaesthesia with isoflurane or halothane in humidified oxygen

This study was designed to determine the relative speeds of induction and complication rates using either halothane or isoflurane for rapid inhalational induction of anaesthesia. Forty ASA physical status 1 and 2, unpremedicated patients presenting for day-care dental surgery received a rapid inhalational induction (RII) with either halothane 3.5% or isoflurane 5% in humidified oxygen. The carrier gas was humidified in order to limit airway irritation caused by the pungency of the volatile agents. Isoflurane produced a faster induction than halothane-121(50) (SD) sec vs 176(36) sec (P less than 0.01). Complication rates during induction (coughing, secretions, excessive movement and abandoned inductions) were similar for the two groups. The majority of patients in both the isoflurane group (17/20) and the halothane group (14/20) found the technique of RII to be acceptable. The incidences of headache, nausea and vomiting were low and not significantly different for the two groups. Isoflurane 5% in humidified oxygen is as acceptable for RII as halothane 3.5% and has a similar complication rate. Isoflurane may be used for RII in cases where it is deemed necessary to avoid halothane, or when a more rapid inhalational induction is required than is possible with halothane. The technique of RII with either agent in unpremedicated patients is well suited to day-care anesthesia.