Anaesthesia and Intensive Care

The acute inflammatory response to sepsis gives rise to significant morbidity and mortality. The mechanisms underlying this form of tissue injury are poorly understood. This review examines the evidence that tissue ischaemia due, to generalized microvascular thrombosis may play an important role.

Microvascular thrombosis is probably an adaptive response that prevents bacteria in the tissues reaching the systemic circulation via the capillaries. In time, a definitive response by leucocytes removes the bacteria and repairs the damaged tissues. There is however evidence that if microvascular thrombosis becomes generalized, then extensive tissue ischaemia may precipitate organ failure and death.

Post-mortem studies of patients with sepsis demonstrate microvascular thrombi in many organs including the kidney, liver, lung, gut, adrenals and brain, and the degree of organ injury is related to the quantity of thrombi. Furthermore studies in human and animal models of sepsis demonstrate therapies that inhibit coagulation or promote fibrinolysis reduce organ failure and mortality.

In view of the personal and economic burdens that tissue injury associated with the acute inflammatory response places on the community, further studies to establish the role of microvascular thrombosis are clearly required. Such studies may lead to new therapies to limit or prevent this form of injury.

A retrospective analysis of 413 patients who received postoperative epidural analgesia under a standardized protocol found that 84 (20%) had a duration of epidural catheterization of greater than four days. The most common reasons were significant pain (n=64, 15%) and coagulopathy (n=26, 6%). Risk factor analysis for coagulopathy showed an odds ratio of 10.1 (95% confidence interval 4.2-24.5) for prolonged epidural catheterization among patients undergoing hepatectomy. Magnetic resonance imaging, performed in four patients with clinical signs suggestive of epidural haematoma, was negative for a space-occupying lesion in all cases. Eleven patients developed fever and clinical signs suggestive of epidural catheter-related infection, necessitating early catheter removal. Sixteen patients had persistent lower limb weakness at 24 hours after catheter removal. The signs soon resolved in all except two, one of whom had neuropathy related to intraoperative positioning and the other preoperative weakness. Accidental epidural catheter dislodgement occurred in 29 patients (7%) and is potentially hazardous if coagulopathy is unresolved. The risk-benefit ratio and factors complicating catheter removal, especially coagulopathy, should be considered when deciding whether to use epidural techniques.

Intensive care is not a medical priority for developing nations. Vila Central Hospital is the major referral centre for the developing Pacific island nation of Vanuatu and runs an ‘as-needed’ intensive care service. Between January 1999 and January 2004, fifty-seven patients were ventilated at Vila Central Hospital. Twenty-two patients survived and 35 died. Eleven patients were declared brain dead, eight died from renal failure, six from overwhelming respiratory failure, three from sepsis, four due to equipment or technical failure, two of unknown causes and one died after transfer to Australia. The patient age range extended from newborns to 80 years. Survivors were ventilated for durations of four hours, (postoperative), to 14.5 days, (ARDS), the median being two days.

This prospective clinical study was performed to determine acid-base regulating variables during abdominal lavage treatment for patients with severe peritonitis or after abdominal surgery. Arterial blood was sampled from twelve patients with secondary peritonitis and nine patients after abdominal surgery without peritonitis at three time points: immediately before, immediately after and 15 minutes after abdominal lavage with normal saline solution. The total₊₊ – amount of irrigant fluid, the strong ion difference [(Na⁺ +K⁺)-(Cl^- +lactate^-)], and total protein concentrations were determined and standard bicarbonate, standard base excess were calculated from pH and P_aCO₂. Peritonitis patients developed a moderate alkalaemia (pH 7.440-7.485). The alkalaemia was unmasked after optimization of mild hypoventilation, but was supported by a decrease in protein concentration of about 3.4 mEql/l in the first 15 minutes after the lavage. There was no marked increase in chloride concentration in either the peritonitis or the control group. The data indirectly exclude major fluid absorption during abdominal lavage with 3000 to 6000 ml normal saline, given that we found no clinically relevant electrolyte and acid-base changes that might be expected after rapid fluid absorption. The factors of major influence in acid-base regulation were ventilation and protein loss in the course of abdominal lavage. Monitoring of the Stewart variables is an easily applicable method of monitoring acid-base regulating variables in the perioperative course of patients undergoing abdominal lavage therapy.

Theoretically, if the cardiac output were increased in the presence of a given intrapulmonary shunt, the arterial saturation should improve as the venous oxygen extraction per ml of blood decreases if the total oxygen consumption remains constant. Previous work demonstrated that this was not achieved with adrenaline or isoprenaline as increased shunting negated any benefit from improved cardiac output and mixed venous oxygen content. However, pharmacological stimulation of cardiac output and venous oxygen without any increase in shunt should achieve the goal of improved arterial oxygenation. To test this hypothesis, seven pigs were subjected to one-lung ventilation and infused on separate occasions, with dopamine and with dobutamine in random order to increase the cardiac output. The mixed venous oxygen content, shunt fraction, oxygen consumption and arterial oxygen saturation were measured.

With both dopamine and dobutamine there was a consistent rise in venous oxygen content. However, with dopamine, the mean shunt rose from 28% to 42% and with dobutamine, the mean shunt rose from 45% to 59% (both changes P<0.01). With dopamine, the mean arterial oxygen saturation fell by 4.7%, and with dobutamine by 2.9%, but neither fall was statistically significant.

It is concluded that any benefit to arterial saturation which might occur from a dopamine- or dobutamine-induced increase in mixed venous oxygen content during one-lung ventilation is offset by increased shunting. During one-lung anaesthesia, there would appear to be no benefit to arterial saturation in increasing cardiac output with an infusion of either dopamine or dobutamine.

This study investigated the effect of pyridostigmine administered at different levels of recovery of neuromuscular function after rocuronium during sevoflurane anaesthesia in children.

Fifty-one patients aged 3 to 10 years, ASA physical status 1 or 2 were randomized to 4 groups: a spontaneous recovery group; or, reversal with pyridostigmine 0.25 mg/kg with glycopyrrolate 0.01 mg/kg at one of three times: 5 minutes after rocuronium administration; at 1% twitch height (T₁) recovery; or at a 25% twitch height (T₂₅) recovery. Anaesthesia was induced with thiopentone (5-7 mg/kg) and maintained with 2-3% sevoflurane and 50% nitrous oxide. Atropine (0.015 mg/kg) and, after calibrating the TOF-Watch^®, rocuronium (0.6 mg/kg) were then administered.

Maximal block occurred 1.1±0.5 min (mean, SD) after rocuronium administration. In the spontaneous recovery group, the clinical duration (recovery to T₂₅) was 40.1±8.8 min and the recovery index (time between T₂₅ and T₇₅) 19.9±9.8 min. Recovery to TOF >0.9 from the time of rocuronium administration was reduced by approximately 30% in the pyridostigmine groups compared to the spontaneous recovery group. There was no significant difference among the three pyridostigmine groups.

When pyridostigmine was given at T₁ or T₂₅, the time from pyridostigmine administration to TOF >0.9 was shorter than for the group receiving pyridostigmine 5 minutes after rocuronium.

Propofol causes pain on intravenous injection in 28 to 90% of patients. A number of techniques have been tried to minimize propofol-induced pain, with variable results. In a randomized, double-blind, placebo-controlled trial, we compared the efficacy of ephedrine 30 μg/kg pretreatment to lignocaine 40 mg for prevention of propofol-induced pain. Ninety-three adult patients, ASA 1 and 2, undergoing elective laparoscopic cholecystectomy were randomly assigned to three groups of 31 each. Group 1 received normal saline, group 2 received lignocaine 2% (40 mg) and group 3 received 30 μg/kg ephedrine. All pretreatment drugs were made up to 2 ml. Pain at the time of propofol injection was assessed on a four-point scale: 0=no pain, 1=mild pain, 2=moderate pain, and 3=severe pain. Twenty-seven patients (87%) of ephedrine pretreatment patients had pain during intravenous injection of propofol as compared to 24 (77%) in the normal saline group. In the lignocaine group, propofol-induced pain was observed in only 13 (42%) when compared with other study groups (P<0.05). Pretreatment with ephedrine 30 μg/kg did not attenuate pain associated with intravenous injection of propofol, nor did it improve haemodynamic stability during induction. However, pretreatment with 2% lignocaine (40 mg) was effective in attenuating propofol-associated pain.

Electroconvulsive therapy (ECT) under propofol anaesthesia induces relatively shorter seizures compared to barbiturate anaesthesia. Since significant correlation between seizure duration and bispectral index (BIS) value immediately before electrical stimulus has been reported among patients, adjustment of anaesthesia depth as determined by BIS may be effective in obtaining a longer seizure length. In the present study, we examined this hypothesis in those patients whose muscular seizure duration was less than 40s.

ECT was prescribed to 20 patients suffering from endogenous depression. General anaesthesia was induced with propofol 1 mg/kg. Succinylcholine chloride 1 mg/kg was then given. The efficacy of electrical stimulation was determined using a tourniquet technique, electromyogram, and electroencephalography. When a patient had a seizure less than 40s in their second ECT treatment, the subsequent treatment was modified such that the electrical stimulus was given after waiting for a higher BIS value (+10-20). Intensity of electrical stimulus and anaesthesia conditions were identical in the two treatments.

All 20 patients had longer seizures as determined by the electromyogram and/or electroencephalography when the stimulus was delivered at the higher BIS value. Seizure duration measured by muscle movement was 31±5s when the stimulus was delivered without waiting and 46±10s when delivered after waiting. There was a significant difference in seizure duration between the two treatments (P<0.01).

Waiting for a recovery in BIS value before electrical stimulation can prolong seizure duration.

The administration of magnesium sulphate is a proposed novel therapy for Irukandji syndrome¹. In this non-randomized, unblinded case series, data from ten patients who received magnesium salts are reviewed. Magnesium sulphate boluses of 10 to 20 mmol, in the six patients for which there was adequate data, reduced pain scores immediately after administration from 8.7±1.5 to 2.8±2.8 (Wilcoxon rank-sum test, P=0.03). In ten patients blood pressure decreased with a mean difference of −18 mmHg in mean arterial pressure. Magnesium requirements in individual patients varied markedly. Pain on injection occurred in four patients, three of whom had received peripherally administered magnesium chloride, and one patient reported transient ptosis after administration of magnesium sulphate 166 mmol over 18 hours in the setting of severe Irukandji syndrome.

Magnesium sulphate administration appears to attenuate pain and hypertension in Irukandji syndrome and warrants further evaluation in this setting.

Nasopharyngeal oxygen therapy, the delivery of supplementary oxygen into the nasopharynx via a fine catheter placed through the nose, is a simple technique used in postoperative anaesthetic care units and paediatric intensive care, but never described in the setting of adult intensive care. In a prospective crossover design, we compared nasopharyngeal oxygen therapy with semi-rigid plastic mask (Hudson Mask) in 50 unintubated adult patients receiving supplemental oxygen. We measured oxygen flow rate to achieve cutaneous saturations 93 to 96%, and patient comfort by visual analogue score. Nasopharyngeal oxygen therapy consumed significantly less oxygen than mask administration (3.0±0.9 vs 6.7±2.1 l/min, P<0.001) and was associated with significantly higher comfort than the mask (7.5± 1.6 cm vs 5.2±1.8, P<0.001).

The use of end-tidal carbon dioxide monitoring to assist in confirming endotracheal tube placement is currently not mandatory in intensive care units (ICUs) in Australia and New Zealand. Early detection of failed tracheal intubation is vital to optimize management and to prevent complications. Questionnaires were sent to the lead clinician/head of department of all 66 intensive care units approved for training purposes by the Joint Faculty of Intensive Care Medicine in Australia and New Zealand. The methods used to confirm correct endotracheal tube placement, the availability of end-tidal carbon dioxide monitoring and its role in confirming endotracheal tube placement in the intensive care unit were explored. Completed questionnaires were received from 61 of the 66 centres (92.4%). Wide variation in the method of confirmation of endotracheal tube position was demonstrated, with 23 (37.7%) of units using sub-optimal methods. Sixty (98.3%) of units had end-tidal carbon dioxide monitoring available. Thirty-eight (62%) units shared monitors between several beds; and 22 (36%) had one monitor per bed. End-tidal carbon dioxide monitoring was used routinely to confirm endotracheal tube placement in 42 (68.8%) units. Fifty-two respondents (83.3%) felt that end-tidal carbon dioxide monitoring was superior to other methods for confirming endotracheal tube placement in critically ill patients. Thirty-eight respondents (62.3%) thought that end-tidal carbon dioxide monitoring should be mandatory to confirm tracheal intubation in the intensive care unit. If it were available, 42 respondents (68.8%) would use end-tidal carbon dioxide monitoring for confirmation of every intubation. Mandatory end-tidal carbon dioxide confirmation of endotracheal tube placement was policy in 33 (54.1%) of the intensive care units.

Clinical hypnosis is a skill of using words and gestures (frequently called suggestions) in particular ways to achieve specific outcomes. It is being increasingly recognised as a useful intervention for managing a range of symptoms, especially pain and anxiety. We surveyed all 317 South Australian Fellows and trainees registered with ANZCA to determine their use, knowledge of, and attitudes towards positive suggestion, hypnosis and hypnotherapy in their anaesthesia practice. The response rate was 218 anaesthetists (69%). The majority of respondents (63%) rated their level of knowledge on this topic as below average. Forty-eight per cent of respondents indicated that there was a role for hypnotherapy in clinical anaesthesia, particularly in areas seen as traditional targets for the modality, i.e. pain and anxiety states. Nearly half of the anaesthetists supported the use of hypnotherapy and positive suggestions within clinical anaesthesia. Those respondents who had experience of clinical hypnotherapy were more likely to support hypnosis teaching at undergraduate or postgraduate level when compared with those with no experience.

We tested the hypothesis that gum elastic-bougie-guided insertion of the ProSeal^™ Laryngeal Mask Airway is more frequently successful than introducer tool guided insertion after failed digital insertion. One hundred anaesthetized patients (ASA 1-2, aged 18 to 80 years) were randomized for the second insertion attempt using either the gum elastic bougie-guided or introducer tool techniques. The bougie-guided technique involved priming the drain tube with the bougie, placing the bougie in the oesophagus using laryngoscope guidance, digital insertion along the palato-pharyngeal curve, and bougie removal. The introducer tool technique involved attaching the introducer tool, single-handed rotation along the palatopharyngeal curve, and introducer tool removal. Failed insertion was classified as (i) failed passage into the pharynx, (ii) malposition, or (iii) ineffective ventilation. Any blood staining was documented. Insertion was more frequently successful (50/50 vs 15/50, P=0.0002) and faster (35±17s vs 54±45s, mean±SD, P=0.006) with the bougie-guided technique. All failed insertions with the introducer tool technique were successful with the bougie-guided technique. The aetiology of failed insertion was similar for the digital and introducer tool techniques in 94% (33/35) of patients. There was no blood staining on the bougie, laryngoscope or introducer tool at removal, but blood staining was more common on the Proseal laryngeal mask airway with the introducer tool technique (9/50 vs 2/50, P=0.03). We conclude that the gum elastic bougie-guided insertion has a higher success rate and causes less trauma than the insertion tool insertion technique after failed digital insertion of the Proseal Laryngeal Mask Airway.

Due to the presence of major lung or extra-pulmonary pathology, which may be unilateral or bilateral, the initial placement of a double-lumen tube is not always straightforward. Although fibreoptic bronchoscopy is often used to confirm “correct” placement, a “blind” technique is frequently used for the initial insertion. The currently widely taught blind technique involves tracheal cuff inflation and ventilation of both lungs as a first manoeuvre, with a subsequent assessment of single-lung ventilation by clamping off, in turn, the two limbs of the double-lumen tube double-connector. An alternative approach involves the bronchial cuff being inflated first, and then using a single-connector to transfer ventilation from one lung to the other. In this paper this technique is described and compared to the more traditional method. On a purely “number of steps” basis, the single-connector approach has several advantages. Furthermore, use of a technique that involves bronchial cuff inflation and single-lung ventilation as a first manoeuvre may reduce the risk of a temporarily malplaced double-lumen tube creating a potentially harmful ball-valve effect in a partially obstructed lobe or lung.

We performed an audit of the insertion of the Single Use Portex Laryngeal Mask in 400 patients. Insertion was successful at first attempt in 335 out of 400 patients (83.8%). However in 15 patients (3.8%), the Portex laryngeal mask could not be placed despite repeated attempts. In 12 of these 15 patients (80%), a standard Laryngeal Mask Airway (LMA) was successfully placed. After the completion of the audit, 22 out of 29 anaesthetists (75.9%), who had inserted 5 Portex laryngeal masks, considered it inferior to the standard LMA. It would appear to us that the Portex laryngeal mask might need some design modifications to be a real alternative to the standard LMA.

Intensive Care (ICU) survivors discharged from ICU to the general ward at night have a higher mortality^1,2. We sought to clarify which factors, including night-shift discharge, influence outcome following ICU discharge in a metropolitan hospital, using a cohort study of critically-ill patients between 1/1/1999-30/4/2003. Patients were excluded from analysis if they (a) died in ICU, (b) were transferred to another hospital, (c) had an ICU length of stay <8 hours, or (d) age <16 years.

Logistic regression was used to derive a predictive model based on the following variables: patient demographics, severity of illness following ICU admission (APACHE II mortality-risk, p_m), final diagnosis, discharge timing including premature or delayed (>4 hours) ICU discharge, and “limitation of medical treatment” orders. The outcome measures were patient status at hospital discharge and ICU readmission rate.

Of the 1870 ICU survivors, 92 (4.9%) died after discharge from ICU. Patients discharged to the ward during the night-shift (2200-0730 hours) had a higher APACHE II score and crude mortality. The difference in APACHE II p_m did not reach statistical significance. No significant calendar or seasonal pattern was identified. Logistic regression identified night-shift discharge (RR=1.7; 95% CI 1.03-2.9; P=0.03), limited medical treatment order (RR=5.1; 95% CI 2.2-12) and admission APACHE II p_m (RR=3.3; 95% CI 1.3-7.6) as independent predictors of patient outcome following ICU transfer to the ward.

Conclusion: At the time of ICU discharge to the ward three factors are predictive of hospital outcome: timing of ICU discharge, limited medical treatment orders and initial illness severity.

We undertook a three-month prospective cohort study of critically ill adult patients referred to the Intensive Care Units 7(ICUs) of public hospitals in metropolitan Melbourne and Geelong, Victoria. The aim was to ascertain the prevalence and immediate consequences of “refused” admission amongst patients appropriately referred to the ICU of first choice.

Between August 1 and October 31, 1999, 10 (out of 12) public hospitals collected data. Three thousand and four patients were referred to these ICUs, and “refusals” were reported by all hospitals. A total of 282 (9.4%) patients were unable to be admitted to the ICU of first choice, giving a rate of 3.1 “refusals” per day. The reasons for “refusal” were limited staffing (52%) and shortage of beds (46%.) Acute inter-hospital transfer (1.7 per day) was the most common immediate triage outcome (57%). These rates are higher than previously reported figures.

We conclude that refused admission to the ICU of first choice, and acute inter-hospital transfer in this region and time period, were common events.

Two cases of critically ill patients who received extracorporeal membrane oxygenation (ECMO) using different forms of circuitry and for different indications are presented. Both patients had life-threatening infections with septic shock and were not able to be supported by conventional means. The first patient had staphylococcal septicaemia and received venoarterial ECMO for circulatory failure. The second patient had psittacosis and received venovenous ECMO for respiratory failure. We discuss the expanding indications for this technology and the role it has to play in adult intensive care.

Massive upper gastrointestinal bleeding from Dieulafoy's lesion in the gastrointestinal tract is uncommon. The use of the Sengstaken-Blakemore tube in acute gastrointestinal bleeding has become less common since endoscopic sclerotherapy and banding procedures have become widely available. The successful use of a Sengstaken-Blakemore tube to control acute massive upper gastrointestinal bleeding from a Dieulafoy's lesion in the lower oesophagus in an elderly man with severe coronary artery disease and heart failure is described.

Rate-dependent left bundle branch block during general anaesthesia is rare. Its occurrence makes electrocardiographic diagnosis of acute myocardial ischaemia or infarction difficult. It can also be confused with a slow rate ventricular tachycardia. We present a case of rate-dependent left bundle branch block in a patient with no previous history of ischaemic heart disease. Carotid sinus massage resulted in a decrease in heart rate and reversion to normal sinus rhythm.