Anaesthesia and Intensive Care

The challenge to achieve a gestalt understanding of general anaesthesia is really dependent upon an understanding of the elusive concept of consciousness. Until very recently, anaesthesia has been understood to depend fundamentally on the lipid solubility of anaesthetic agents, unsurprisingly a misleading view which has followed from the greater simplicity of lipid chemistry compared with protein chemistry and, it is contended here, from a serious misunderstanding of the older experimental data. Nonetheless, because an over-simplistic view of lipids pertains in much pharmacological thinking about anaesthesia, this paper devotes some attention to potentially relevant aspects of lipid function and also to concepts of anaesthesia which are based on the properties of intracellular and extracellular water. It is argued that the more correct pharmacological explanation is likely to be action at hydrophobic sites of crucial functional molecules, most plausibly protein molecules: empirical data which support such actions are presented and considered.

Anaesthetic actions on a range of such proteins are discussed, with the emphasis on general neurophysiological principles, with the intent of avoiding the mire into which detailed consideration of actions at specific sites of putative function in the central nervous system can lead. Those experimentally-documented actions include influences on the proteins which constitute the Na⁺-ion conductance channels in axonal membranes (which are the basis for action potentials); on the Ca²⁺-ion channels which are crucial for neurotransmitter secretion from nerve terminals; on the properties of the ion channels in the post-synaptic membranes of the neurons which are the targets for transmitter action; on components of the “second messenger” systems of target neurons; as well as actions on metabolically significant enzymes (notably cytochrome P450).

The overall argument is that the concept of anaesthetic actions on lipids should be abandoned in favour of one which is consistent with the general pharmacological principle of drug action at specific receptor sites, i.e. a targeted action at unique loci on relevant proteins.

Acute pancreatitis is an inflammatory process of the pancreas with variable involvement of regional tissues and remote organs. This review gives a comprehensive overview of the aetiology, pathophysiology, diagnosis and therapy of acute pancreatitis relevant to the intensivist. Recent international guidelines on the management of acute pancreatitis are summarised.

Eighty percent of acute pancreatitis episodes are related either to gallstones or to alcohol abuse. Independent of its aetiology, the pathophysiologic hallmark of acute pancreatitis is the premature activation of trypsin, which leads to massive pancreas inflammation, systemic overproduction of pro-inflammatory mediators and ultimately remote organ dysfunction. All guidelines agree that the diagnosis of acute pancreatitis should include clinical symptoms, increased serum amylase or lipase levels and/or characteristic findings on computed tomography. Endoscopic retrograde cholangiopancreatography is recommended as a causative therapy in patients with acute cholangitis or a strong suspicion of gallstones. All guidelines underline the importance of vigorous fluid resuscitation and supplemental oxygen therapy and prefer enteral over parenteral nutrition, with the majority favouring the nasojejunal route. In view of lacking scientific evidence, antibiotic prophylaxis to prevent infection of pancreatic necroses is discouraged by most guidelines. Computed tomography-guided fine needle aspiration is the technique of choice to differentiate between sterile and infected pancreas necrosis. While sterile pancreatic necrosis should be managed conservatively, infected pancreatic necrosis requires debridement and drainage supplemented by antibiotic therapy. Surgical necrosectomy is the traditional approach, but less invasive techniques (retroperitoneal or laparoscopic necrosectomy, computed tomography-guided percutaneous catheter drainage) may be equally effective.

Physiological and pharmacological differences exist between men and women. Women wake faster than men following general anaesthesia. Women also differ from men in their postoperative recovery as reflected by differences in postoperative pain, nausea and vomiting and overall quality of recovery. These gender differences seem to be more pronounced in premenopausal women, suggesting hormonal mechanisms are a major contributing factor.

With advances in technology, videoscopy and optic intubation have been gaining popularity, particularly in patients with difficult airways or as rescue devices in failed intubation attempts. Their routine use is, however, an uncommon occurrence. This review paper will summarise some of those newly developed devices currently available to assist tracheal intubation, their advantages, disadvantages when compared with the conventional laryngoscope and finally, evidence to support their use in both elective and emergency airway management.

This review aims to summarise the physiology of C-reactive protein (CRP), its possible roles and limitations as an inflammatory and infective marker in intensive care medicine, and also the emerging roles of CRP in the pathogenesis of cardiovascular and autoimmune diseases. Observational and animal studies on uses of CRP were retrieved from the PubMed database without any language restrictions. Quantitative data were not pooled because of the heterogeneity of patient characteristics and disparate ways in which CRP was studied. Serum CRP concentrations are determined by the synthetic rate of its production in the liver regulated predominantly by interleukin-6. It has a half-life of 19 hours and is relatively slow in its onset and offset in response to an acute inflammatory process when compared to procalcitonin. It has some favourable properties and limitations as an inflammatory marker. An elevated CRP concentration is not specific to infections and the absolute CRP concentrations cannot be used to differentiate between bacterial, fungal and severe viral infections. The dynamic response of CRP to therapy that aims to modify the underlying inflammatory process and the clinical context of a patient are of pivotal importance when CRP concentrations are interpreted. CRP is found to be a significant partaker and prognostic factor in a wide range of cardiovascular and chronic diseases. In summary, CRP concentration is an important prognostic factor of many acute and chronic diseases. Serial CRP measurements may be useful to reflect a patient's response to therapy that aims to modify the underlying inflammatory process.

This study was designed to evaluate different doses of hypobaric 0.15% bupivacaine administered to achieve unilateral orthopaedic surgery under subarachnoid block.

Using a randomised, double-blinded protocol, 150 ASA I to II patients scheduled for elective unilateral orthopaedic surgery were allocated to received a subarachnoid block with hypobaric bupivacaine 0.15% 4.5 mg (3 ml) (Group 1), 6.0 mg (4 ml) (Group 2) or 7.5 mg (5 ml) (Group 3). Measurements included cardiovascular and haemodynamic stability, incidence of unilateral anaesthesia, time to recover from motor block, postoperative urinary retention, transitory neurological symptoms and postdural puncture headache.

There was a dose-dependent increase in the duration of the block, from 1:55±00:20 hours (4.5 mg) to 2:15±00:22 hours (6.0 mg) and 3:15±00:31 hours (7.5 mg). The sensory block in the operated limb was significantly higher than that in the non-operated limb at all times. The increasing dose resulted in an increase of the motor block score. Seventy percent of patients had unilateral block. It was concluded that the spinal anaesthesia in all groups was suitable for single limb orthopaedic surgery. The smallest dose (4.5 mg) of hypobaric 0.15% bupivacaine resulted in more unilateral blocks, with narrower distribution and shorter duration.

We report the findings of a randomised controlled triple-blind pilot study of intraoperative ketamine infusion combined with spinal anaesthesia on the prevalence of persisting post surgical pain following total knee arthroplasty surgery. Twelve patients were randomised to receive either ketamine or placebo in association with spinal anaesthesia for total knee arthroplasty. All patients also received general anaesthesia. More patients were pain-free at six months in the ketamine group (three of five) compared to the control group (two of seven). Perioperative data collected during the study suggested that the addition of intraoperative ketamine might also improve the quality of recovery. Although no statistical analysis was undertaken due to the small numbers, these preliminary findings suggest that the use of intraoperative systemic ketamine in association with spinal anaesthesia for the reduction of persisting post surgical pain deserves further study.

Vitamin deficiency is believed to be common in critical illness. Water soluble and antioxidant vitamins are those most frequently used for supplementation in these patients. There are no data to confirm the prevalence of vitamin deficiencies in high-risk emergently admitted intensive care patients, nor their association with hospital mortality.

One hundred and twenty-nine consecutive, critically ill patients who were emergently admitted to intensive care were enrolled in this prospective observational cohort study. Patient data including diagnosis, source of admission and severity of illness scores were prospectively collected. Within the first 48 hours of admission, concentrations of C-reactive protein, Vitamins A, E, B₁, B₁₂ and folate were measured on arterial blood. Multivariate stepwise logistic regression modelling was performed to examine the association of vitamin concentrations with hospital mortality. Fifty-five patients (43%) had a biochemical deficiency of one of the five vitamins on admission to the intensive care unit. A total of 18 patients died (14%) during their hospital stay (15 of those in the intensive care unit). Moderate correlations with C-reactive protein concentrations were demonstrated for Vitamins B₁₂, A and E (Spearman's r=0.309, −0.541 and −0.299, P=0.001, 0.001 and 0.007 respectively). Hospital mortality was significantly associated with age, APACHE II score, admission and maximum Sequential Organ Failure Assessment scores and admission source in the univariate analyses. Multivariate analysis did not demonstrate an association between biochemical deficiency and mortality. Biochemical deficiencies of water-soluble and antioxidant vitamins are common on admission in unplanned or emergency admissions to the intensive care unit, but we could not demonstrate an independent association with hospital mortality.

Several studies have been conducted to evaluate the utilisation of the operating room, a fixed resource, in terms of conditions that prevent day-of-surgery cancellation due to deficient operative capacity. In this study, we surveyed the causes and overall rates of elective surgery cancellation and then compared the number of cancellations that occurred before and after the installation of additional operating rooms.

We surveyed all patients undergoing elective surgery for 100 days prior to and after the installation of additional operating rooms. The causes for cancellations were divided into six categories: departmental issues, abnormal laboratory results, patient denial, inadequate preparation, over-booking and other issues. The departmental causes were further divided into four categories: ward overflow, scheduling date errors, unavailable surgeons and other issues.

The number of overall cancelled cases and scheduled cases increased following the increase in operating room capacity, although this increase was not statistically significant. However, the cancellation ratio rose significantly after the operating room capacity was increased. The primary reasons for cancellation prior to the increase in operating room capacity were departmental issues, over-booking and abnormal laboratory data, in that order. After the operating room capacity was increased, the primary reasons for cancellation were departmental issues, abnormal laboratory data and over-booking, in that order. Taken together, the results of this study indicate that increased operating room capacity can prevent cancellation due to over-booking. However, the numbers of cancellations due to ward overflow exceeded the numbers of cancellations that occurred as a result of over-booking.

In conclusion, increasing the operating room capacity is not an appropriate option for preventing the cancellation of operations.

A study was undertaken to describe the practice and outcomes of mechanical ventilation throughout Korea. This prospective cohort study was conducted over a three-month period enrolling patients (n=519) who received mechanical ventilation for more than 72 hours in 21 university hospital intensive care units throughout Korea.

The most common indication for mechanical ventilation was acute respiratory failure. The most common cause of acute-on-chronic respiratory failure was tuberculous lung disease. The most common initial mode for ventilation was volume-controlled ventilation. The mean tidal volume of acute respiratory distress syndrome patients was 7.6 ml/kg of the predicted body weight and the mean positive end-expiratory pressure was 9.4 cmH₂O. The weaning success rate at 28 days was 50.3%. Pressure support and the T-piece were most commonly used as initial and final weaning modes respectively. Preventive measures against deep vein thrombosis during mechanical ventilation were performed more frequently in intensive care units with full-time critical care physicians than those without such physicians. Multivariate analysis showed that the APACHE II score, indication for mechanical ventilation, respiratory rate at 72 hours, enteral feeding and prophylaxis of deep vein thrombosis were prognostic factors for survival.

In Korean intensive care units, tuberculous lung disease remains an important cause for mechanical ventilation. The practice of mechanical ventilation in Korean intensive care units in general appeared to comply with the current international recommendations with regard to lung protection and weaning. However, intensive care units lacking critical care physicians seemed to be adopting fewer ancillary measures, such as deep vein thrombosis prophylaxis.

Hepatocellular toxicity is a putative side-effect of amiodarone. The hepatic detoxification enzyme glutathione S-transferase-A1-1 (GSTA1-1) is a sensitive indicator of hepatocellular damage. We investigated the occurrence of subclinical liver injury, as measured by plasma GSTA1-1 in intensive care unit patients with atrial fibrillation receiving amiodarone.

Sixteen haemodynamically stable intensive care unit patients with atrial fibrillation were treated with amiodarone intravenously. Patients were given a loading dose of 150 mg followed by another 150 mg followed by a continuous infusion of 1200 mg/hour if atrial fibrillation persisted. Blood samples for GSTA1-1 (measured by an enzyme-linked immunosorbent assay) were taken at zero, one, three, six, 12 and 24 hours, transaminases and bilirubin at zero, six, 12 and 24 hours. Blood pressure and heart rate were continuously monitored. Effects were analysed for time-dependent changes (one-way analysis of variance for repeated measures).

Blood pressure increased from 125±8/60±3 mmHg at t=0 to 144±9/66±4 mmHg at t=24 hours (P <0.05), heart rate decreased from atrial fibrillation 124±5 to sinus rhythm 86±6 beats per minute (P <0.05). There was no significant elevation of GSTA1-1, transaminases or bilirubin during the observation period of 24 hours.

Amiodarone does not cause elevation of GSTA1-1 as a marker of subclinical liver injury in haemodynamically stable intensive care unit patients with atrial fibrillation.

The aim of this study was to determine the hospital survival of patients receiving high doses of catecholamines.

A retrospective observational study was conducted in a 22-bed multidisciplinary adult intensive care unit of a tertiary referral university hospital. All patients (n = 64) receiving >100 μg/min of adrenaline or noradrenaline or adrenaline and noradrenaline combined over a one-year period were studied to determine survival to intensive care unit and hospital discharge. Four patients survived to intensive care unit discharge and hospital discharge (6.25%, 95% CI 0.3 to 12.2%). Survival was 3.3% (95% CI 0 to 7.9%) in the subgroup of 60 patients who received >100 μg/min noradrenaline and 3.6% (95% CI 0 to 8.6%) in the 55 patients who received >2 μg/kg/min noradrenaline. None of the 32 patients who received >200 μg/min noradrenaline survived.

We conclude that the survival of patients requiring high doses of catecholamines is poor, but the use of such doses is probably not futile. It remains for individual clinicians, patients and their surrogates to decide whether use of high doses of vasopressor is appropriate, given the low probability of survival.

The use of sterile plastic sleeves to protect pulmonary artery catheters (PAC) may decrease infection risk. The catheter may require manipulation but contamination of the sleeve risks inoculating organisms into the patients. We sought to determine whether the sleeve remains sterile and for how long.

We conducted a prospective observational study to culture the components of the PAC in a critically ill population. Upon removal we cultured 1) the PAC tip, 2) the PAC introducer exit site, 3) the PAC introducer hub and 4) a sterile irrigant solution which ran down the inside of the protective sleeve. Demographic, catheter and disease variables were also collected.

There were 102 PAC episodes amounting to 3952 catheter hours with a mean duration of catheterisation of 39.1 (24.2) hours. There were 17 positive culture results, of which six were positive sleeve fluid cultures. In three of these patients the exit site was culture positive, and the same organism was isolated as within the sleeve. No patient had a positive blood culture. There was no difference between those with and without a positive sleeve culture in terms of demographic or disease variables.

The protective sleeve of the pulmonary artery catheter does not remain sterile and should not be considered as a sterile barrier. We believe that manipulating the PAC within the sleeve carries the risk of inoculating the patient with pathogenic organisms. The duration of sterility remains to be determined.

A novel technique for management of the difficult airway is described. The case report describes fibreoptic intubation of a patient who refused awake intubation. An endotracheal tube was advanced as far as the nasopharynx via the nostril of the patient, under anaesthesia. Connection of the anaesthetic circuit allowed maintenance of anaesthesia, oxygenation and assisted ventilation while flexible bronchoscopy was performed through the tube via a bronchoscopy connector. The endotracheal tube was subsequently advanced over the bronchoscope into the trachea. This technique uses readily available materials and can be used where the placement of a laryngeal mask is contraindicated or impossible.

We present a case of a 40-year-old woman requiring elective surgery who had an unexpected Grade 4 Cormack and Lehane laryngoscopy view. Both curved and straight laryngoscope blades in the sniffing and hyperextended head and neck positions were used. Endotracheal intubation was accomplished with some difficulty using a No. 3 Macintosh blade and Frova intubating catheter in the sniffing position. The cause of the difficult laryngoscopy was a lingual tonsil as shown in postoperative magnetic resonance scans.

We feel that a comprehensive postoperative evaluation should be conducted after every difficult laryngoscopy (Cormack and Lehane Grade 3b and 4). The use of magnetic resonance imaging may provide important objective information for both the anaesthetist and the patient, allowing a better understanding of causes and possible solutions for future airway management.

Carnitine palmitoyl transferase (CPT) type 2 deficiency is a disorder of mitochondrial fatty acid oxidation. In situations where energy stores are inadequate, such as may occur during labour, women with CPT type 2 deficiency are at risk of rhabdomyolysis. There is limited experience in the management of women with this condition in labour. We report a case of successful labour management of a woman with CPT type 2 deficiency, together with a brief review of the published case reports and a discussion of the issues surrounding anaesthetic management.

We describe a case of airway obstruction secondary to a large pre-vertebral cervico-mediastinal haematoma following failed attempts at insertion of an internal jugular central venous line. The need for a high index of suspicion to diagnose this injury and early aggressive intervention to manage it are outlined. The role of ultrasound guidance in preventing such a complication is reviewed, as well as other possible mechanisms of haematoma development.

Posthypoxic myoclonus is a rare and devastating complication of near-fatal cardiopulmonary arrest. Despite treatment with available anti-myoclonic agents, some patients may recover cognitively but remain completely disabled by severe myoclonus. We report a 16-year-old patient with severe treatment-refractory posthypoxic myoclonus, which improved markedly with administration of the drug sodium oxybate.

We report the case of a patient who presented with coma in the context of baclofen and quetiapine overdose. While the clinical picture was largely in keeping with previous descriptions of baclofen and quetiapine toxicity, the patient went on to exhibit clinical and biochemical features of cranial diabetes insipidus, a finding which has not previously been described in this context.