Association of Anaesthetists of Great Britain and Ireland: Safe vascular access 2016.

Safe vascular access is integral to anaesthetic and critical care practice, but procedures are a frequent source of patient adverse events. Ensuring safe and effective approaches to vascular catheter insertion should be a priority for all practitioners. New technology such as ultrasound and other imaging has increased the number of tools available. This guidance was created using review of current practice and literature, as well as expert opinion. The result is a consensus document which provides practical advice on the safe insertion and removal of vascular access devices.

Haploidentical peripheral blood stem cell infusion in combination with chemotherapy for acute myeloid leukaemia in elderly patients.

Elderly patients with acute myeloid leukaemia (AML) have a poor prognosis with standard chemotherapy. Two elderly AML patients treated with infusion of family-derived partially human leukocyte antigen (HLA)-matched peripheral blood stem cells following each cycle of chemotherapy entered morphological complete remission without graft versus host disease or major toxicity. Our results support this as a non-toxic approach for inducing a graft versus leukaemia effect in patients not suitable for allogeneic transplantation. Additional resources required for donor assessment and harvest may be reduced by using banked partially HLA-matched mononuclear cells from unrelated donors.

Evaluation of the Sherlock 3CG Tip Confirmation System on peripherally inserted central catheter malposition rates.

Peripherally inserted central catheters are often positioned blindly in the central circulation, and this may result in high malposition rates, especially in critically ill patients. Recently, a new technology has been introduced (Sherlock 3CG Tip Positioning System) that uses an electro-magnetic system to guide positioning in the superior vena cava, and then intra-cavity ECG to guide positioning at the cavo-atrial junction. In this observational study, we investigated how the Sherlock 3CG Tip Positioning System would affect peripherally inserted central catheter malposition rates, defined using a post-insertion chest radiograph, in critically ill patients. A total of 239 catheters positioned using the Sherlock 3CG Tip Positioning System were analysed. When an adequate position was defined as low superior vena cava or cavo-atrial junction, 134 catheters (56.1%; 95% CI 50-62%) were malpositioned. When an adequate position was defined as mid/low superior vena cava, cavo-atrial junction or high right atrium (≤ 2 cm from cavo-atrial junction), 49 (20.5%; 95% CI 16-26%) catheters were malpositioned. These malposition rates are significantly lower than our own historical data, which used a 'blind' anthropometric technique to guide peripherally inserted central catheter insertion.

Clinical and economic impact of a switch from high- to low-volume renal replacement therapy in patients with acute kidney injury.

High-intensity renal replacement therapy protocols in intensive care patients with acute kidney injury have failed to translate to improved patient outcomes when compared with lower-intensity protocols. This retrospective study explored the clinical and economic impacts of switching from a 30-35 ml.kg(-1) .h(-1) (high-volume) to a 20 ml.kg(-1) .h(-1) (low-volume) protocol. Patients (n = 366) admitted 12 months before (n = 187) and after (n = 179) the switch were included in the study. There was no difference in in-hospital mortality (77/187 (41%) vs 75/179 (42%), respectively, p = 0.92), intensive care unit mortality (55/187 (29%) vs 61/179 (34%), respectively, p = 0.40), duration of organ support or extent of renal recovery between the high- and low-volume cohorts. A 25% reduction in daily replacement fluid usage was observed, equating to a cost saving of over £27 000 per annum. In conclusion, a switch from high- to low-volume continuous haemodiafiltration had minimal effects on clinical outcomes and resulted in marked cost savings.

Defining peripherally inserted central catheter tip position and an evaluation of insertions in one unit.

Peripherally inserted central catheters are increasingly used to provide access to the central venous circulation. They are commonly positioned 'blind' using a variety of anthropometric techniques and operator experience to direct insertion length. Malposition rates are poorly defined because of differing insertion techniques, difficulties defining anatomical tip position on chest radiographs, controversy over what constitutes an adequate catheter position and possible differences between patient groups. We have developed a reproducible method to define catheter positions on chest radiograph and have applied this in a retrospective analysis of 256 ICU and 243 non-ICU catheter insertions over a 6-month period. Two different definitions were used for adequate position. 'Blind' positioning of peripherally inserted central catheters was associated with a definition-dependent malposition rate of 42-76%. Malposition rates were significantly higher in ICU patients. Emerging technologies may assist in reducing these high rates.

Fibular lengthening by Ilizarov method secondary to shortening by osteochondroma of distal tibia.

Osteochondroma is the most common benign bone tumour. They most commonly affect the long tubular bones and almost half of osteochondromata are found around the knee. Osteochondroma arising from the distal metaphysis of the tibia typically result in a valgus deformity of the ankle joint secondary to relative shortening of the fibula. This case describes the use of Ilizarov technique for fibular lengthening following excision of a distal tibial osteochondroma. A 12-year-old girl presented with a 3-year history of a large swelling affecting the lateral aspect of the right distal tibia. Plain radiographs confirmed a large sessile osteochondroma arising from the postero-lateral aspect of the distal tibia with deformity of the fibula and 15 mm of fibular shortening. The patient underwent excision through a postero-lateral approach and subsequent fibular lengthening by Ilizarov technique. The patient made excellent recovery with removal of frame after 21 weeks and had made a full recovery with normal ankle function by 6 months. The Ilizarov method is a commonly accepted method of performing distraction osteogenesis for limb inequalities; however, this is mainly for the tibia, femur and humerus. We are unaware of any previous cases using the Ilizarov method for fibular lengthening. This case demonstrates the success of the Ilizarov method in restoring both fibular length and normal ankle anatomy.

Influence of improved teaching on medical students' acquisition and retention of drug administration skills.

BACKGROUND: Drug administration error is a major problem causing substantial morbidity and mortality worldwide. Lack of education about drug administration appears to be a causative factor. We devised an online teaching module for medical students and assessed its short- and long-term efficacy. METHODS: One hundred and thirty clinical medical students were invited to undertake additional, online, teaching about drug administration. Those participating were identified and the number of web pages viewed recorded. The students' knowledge retention was tested by means of drug administration questions incorporated into routine assessments and examinations over the next 6 months. Other indices of all students' performance were recorded to correct for confounding factors. RESULTS: Just over half (52%) responded to the invitation to participate. The amount of interest they showed in the teaching module correlated positively with their performance in questions about drug administration, although the latter waned over time. Surprisingly, correcting for students' general ability and keenness revealed that the less able students were most likely to undertake the teaching module. CONCLUSIONS: Additional online teaching about drug administration improves students' knowledge of the topic but clearly requires reinforcement; however, only about half the students took up the option. Medical students must acquire these fundamental skills, and online teaching can help. Medical educators must ensure that drug administration is taught formally to all students as part of the curriculum and must understand that it may require additional teaching.

Physiological thresholds for irreversible tissue damage in contusional regions following traumatic brain injury.

Cerebral ischaemia appears to be an important mechanism of secondary neuronal injury in traumatic brain injury (TBI) and is an important predictor of outcome. To date, the thresholds of cerebral blood flow (CBF) and cerebral oxygen utilization (CMRO(2)) for irreversible tissue damage used in TBI studies have been adopted from experimental and clinical ischaemic stroke studies. Identification of irreversibly damaged tissue in the acute phase following TBI could have considerable therapeutic and prognostic implications. However, it is questionable whether stroke thresholds are applicable to TBI. Therefore, the aim of this study was to determine physiological thresholds for the development of irreversible tissue damage in contusional and pericontusional regions in TBI, and to determine the ability of such thresholds to accurately differentiate irreversibly damaged tissue. This study involved 14 patients with structural abnormalities on late-stage MRI, all of whom had been studied with (15)O PET within 72 h of TBI. Lesion regions of interest (ROI) and non-lesion ROIs were constructed on late-stage MRIs and applied to co-registered PET maps of CBF, CMRO(2) and oxygen extraction fraction (OEF). From the entire population of voxels in non-lesion ROIs, we determined thresholds for the development of irreversible tissue damage as the lower limit of the 95% confidence interval for CBF, CMRO(2) and OEF. To test the ability of a physiological variable to differentiate lesion and non-lesion tissue, we constructed probability curves, demonstrating the ability of a physiological variable to predict lesion and non-lesion outcomes. The lower limits of the 95% confidence interval for CBF, CMRO(2) and OEF in non-lesion tissue were 15.0 ml/100 ml/min, 36.7 mumol/100 ml/min and 25.9% respectively. Voxels below these values were significantly more frequent in lesion tissue (all P < 0.005, Mann-Whitney U-test). However, a significant proportion of lesion voxels had values above these thresholds, so that definition of the full extent of irreversible tissue damage would not be possible based upon single physiological thresholds. We conclude that, in TBI, the threshold of CBF below which irreversible tissue damage consistently occurs differs from the classical CBF threshold for stroke (where similar methodology is used to define such thresholds). The CMRO(2) threshold is comparable to that reported in the stroke literature. At a voxel-based level, however (and in common with ischaemic stroke), the extent of irreversible tissue damage cannot be accurately predicted by early abnormalities of any single physiological variable.

Predicting the response of intracranial pressure to moderate hyperventilation.

BACKGROUND: Hyperventilation may cause brain ischaemia after traumatic brain injury. However, moderate reductions in PaCO(2) are still an option in the management of raised intracranial pressure (ICP) under some circumstances. Being able to predict the ICP-response to such an intervention would be advantageous. We investigated the ability of pre-hyperventilation ICP and cerebrospinal compensatory reserve to predict the reduction in ICP achievable with moderate hyperventilation in head injured patients. METHODS: Thirty head injured patients requiring sedation and mechanical ventilation were investigated. ICP was monitored via an intraparenchymal probe and intracranial cerebrospinal compensatory reserve was assessed using an index (R(ap)) based on the relationship between mean ICP and its pulse amplitude. Measurements were made at a constant level of PaCO(2) during a 20-minute baseline period. The patients were then subjected to an acute decrease in PaCO(2) of approximately 1 kPa and, after an equilibration period of 10 minutes, measurements were again made at a constant level of PaCO(2) for a further 20 minutes. A multiple linear regression model, incorporating baseline PaCO(2), ICP, and R(ap) was used to identify the relevant predictors of ICP reduction. FINDINGS: Baseline ICP and R(ap) were both significant predictors of ICP-reduction (p=0.02 and 0.001 respectively) with R(ap) being the more powerful parameter. CONCLUSIONS: A model based on cerebrospinal compensatory reserve and ICP can predict the achievable ICP-reduction and may potentially be used to optimise patient selection and intensity of hyperventilation.

Effects of moderate hyperventilation on cerebrovascular pressure-reactivity after head injury.

In volunteers, hyperventilation improves autoregulation. However, in head-injured patients, hyperventilation-induced deterioration and improvement of autoregulation have been reported. We have re-examined this question using an index of pressure reactivity. Thirty patients with severe or moderate head-injury were studied. Arterial blood pressure, cerebral perfusion pressure (CPP), and intracranial pressure (ICP) were recorded over 20 minute epochs separated by ten minutes of equilibration at baseline and during moderate (>3.5 kPa) hyperventilation. End-tidal CO2 was constant during each phase of data acquisition. Pressure reactivity was assessed using an index 'PRx' based on the response of ICP to spontaneous blood pressure changes. Hyperventilation decreased PaCO2 from 5.1 +/- 0.4 to 4.4 +/- 0.4 kPa (p < 0.0001). ICP decreased by 3.7 +/- 2.2 mmHg (p < 0.001). CPP increased by 5.9 +/- 8.2 mmHg (p < 0.001). Overall, PRx did not change significantly with hyperventilation. However, there was a significant negative correlation between baseline PRx and the change in PRx (r = -0.71, p < 0.0001). This suggests that patients with disturbed pressure-reactivity may improve, whereas patients with intact pressure reactivity remain largely unchanged. Our data suggest that the response of pressure reactivity to hyperventilation is heterogeneous. This could be due to hyperventilation-induced changes in cerebral metabolism, or the change in CPP.

Imaging of cerebral blood flow and metabolism in brain injury in the ICU.

The heterogeneity of the initial insult and subsequent pathophysiology has made both the study of human head injury and design of randomised controlled trials exceptionally difficult. The combination of multimodality bedside monitoring and functional brain imaging positron emission tomography (PET) and magnetic resonance (MR), incorporated within a Neurosciences Critical Care Unit, provides the resource required to study critically ill patients after brain injury from initial ictus through recovery from coma and rehabilitation to final outcome. Methods to define cerebral ischemia in the context of altered cerebral oxidative metabolism have been developed, traditional therapies for intracranial hypertension re-evaluated and bedside monitors cross-validated. New modelling and analytical approaches have been developed.

Effects of propofol on cerebral oxygenation and metabolism after head injury.

BACKGROUND: Flow-metabolism coupling is thought to be deranged after traumatic brain injury, while the effects of propofol on flow-metabolism coupling are controversial. We have used a step increase in target plasma propofol concentration in head injured patients to explore flow-metabolism coupling in these patients. METHODS: Ten patients with a moderate to severe head injury received a step increase in propofol target controlled infusion of 2 microg x ml(-1). Cerebral tissue gas measurements were recorded using a multimodal sensor, and regional chemistry was assessed using microdialysis. Arterial-jugular venous oxygen differences (AVDO(2)) were measured and all patients had cortical function monitoring (EEG). RESULTS: The step increase in propofol led to a large increase in EEG burst-suppression ratio (0% (range 0-1.1) to 46.1% (range 0-61.7), P<0.05); however, this did not significantly change tissue gas levels, tissue chemistry, or AVDO(2). CONCLUSIONS: Flow-metabolism coupling remains intact during a step increase in propofol after traumatic brain injury. The EEG burst-suppression induced by propofol after traumatic brain injury does not appear to be a useful therapeutic tool in reducing the level of regional ischaemic burden.

Cerebral oxygen vasoreactivity and cerebral tissue oxygen reactivity.

There has long been an appreciation that cerebral blood flow is modulated to ensure adequate cerebral oxygen delivery in the face of systemic hypoxaemia. There is increasing appreciation of the modulatory role of hyperoxia in the cerebral circulation and a consideration of the effects of such modulation on the maintenance of cerebral tissue oxygen concentration. These newer findings are particularly important in view of the fact that cerebrovascular and tissue oxygen responses to hyperoxia may change in disease. Such alterations provide important insights into pathophysiological mechanisms and may provide novel targets for therapy. However, before the modulatory effects of hyperoxia can be used for diagnosis, to predict prognosis or to direct therapy, a more detailed analysis and understanding of the physiological concepts behind this modulation are required, as are the limitations of the measurement tools used to define the modulation. This overview summarizes the available information in this area and suggests some avenues for further research.

Validation of a tonometric noninvasive arterial blood pressure monitor in the intensive care setting.

Intra-arterial measurement is considered the gold standard for continuous, beat-to-beat arterial blood pressure monitoring. However, arterial cannulation can be difficult and may cause complications such as thrombosis and ischaemia. Recently, a tonometric system, the Colin CBM-7000 has been developed for noninvasive beat-to-beat measurement of arterial blood pressure from the radial artery. We assessed the level of agreement between the CBM-7000 and invasive radial artery measurements in 15 patients on a neuro-intensive care unit. Agreement of systolic, diastolic and mean arterial pressure values was limited, with approximately 34% of mean arterial pressures differing by over 10 mmHg. In many cases, this was due to a downward drift of the noninvasive measurements over time. Furthermore, there was a tendency to underestimate low pressures and overestimate high pressures. In our opinion, the Colin CBM-7000 cannot be recommended for continuous blood pressure monitoring in the intensive care setting.

Hyperoxia and the cerebral hemodynamic responses to moderate hyperventilation.

BACKGROUND: A reduction in the arterial partial pressure of CO2 (PaCO2) leads to a rapid reduction in cerebral blood flow (CBF). However, despite continuing hypocapnia there is secondary recovery of CBF over time as a result of increases in lactic acid production. Hyperoxia is thought to modulate the production of lactic acid. This study examined the kinetics of middle cerebral artery flow velocity (MCA FV) reduction during hyperventilation, and its modulation by hyperoxia. METHODS: Cerebral blood flow was assessed using transcranial Doppler ultrasound in nine healthy, awake human volunteers. Subjects were ventilated, via a mouthpiece, to achieve a stable end-tidal CO2 (PETCO2). After a 20-min baseline period the minute volume on the ventilator was passively increased by approximately 20% to reduce PETCO2 by 0.75-1 kPa. After a 10-min stabilization period the new PETCO2 level was maintained at a constant level for 20 min, and MCA FV recovery was measured during this 20-min period. Subjects undertook the protocol breathing air and breathing 100% oxygen. RESULTS: The PETCO2 level was (mean +/- SD) 4.9 +/- 0.4 kPa (normoxia baseline), 4.0 +/- 0.3 kPa (normoxia hyperventilation), 4.6 +/- 0.4 kPa (hyperoxia baseline) and 3.9 +/- 0.4 kPa (hyperoxia hyperventilation). CO2 reactivity was significantly lower with normoxia than hyperoxia (16.5 +/- 3.8 vs. 21.2 +/- 4.6 % kPa-1; P< 0.05). Middle cerebral artery FV recovery was significantly more rapid with normoxia than hyperoxia (0.23 +/- 0.17 vs. 0.08 +/- 0.1 % baseline min-1; P< 0.01). CONCLUSIONS: Our results suggest that cerebral hemodynamic responses to moderate hyperventilation are different in normoxic and hyperoxic conditions. Clinical assessment of CO2 reactivity and CBF recovery during hyperventilation should take the degree of arterial oxygenation into account.

Anaesthesia with remifentanil and rocuronium for caesarean section in a patient with long-QT syndrome and an automatic implantable cardioverter-defibrillator.

A 24-year-old woman with congenital long-QT syndrome (LQTS) required caesarean section at 32 weeks' gestation. Her risk of premature death from malignant ventricular tachyarrhythmias had necessitated implantation of an automatic cardioverter-defibrillator (AICD) with pacemaker capability. The patient expressed a preference for general anaesthesia. To minimise the risk of increased serum catecholamine concentrations and consequent ventricular arrhythmias, an analgesia-based regimen was chosen. With cardioversion, defibrillation, and antitachycardia pacing functions of the AICD selectively deactivated, anaesthesia was induced with bolus doses of thiopentone and remifentanil. Rocuronium was used for neuromuscular block. Anaesthesia was maintained with nitrous oxide and isoflurane, supplemented by a remifentanil infusion. We outline the pathophysiology and treatment of LQTS, and discuss the anaesthetic management of an obstetric patient with the congenital syndrome. This is the first reported case of caesarean section in a patient with an AICD, and the first description of the use of either remifentanil or rocuronium in LQTS.