Oxidative stress in critical care and vitamins supplement therapy: "a beneficial care enhancing".

OBJECTIVE: Critical illnesses are a significant public health issue because of their high rate of mortality, the increasing use of the Intensive Care Units and the resulting healthcare cost that is about 80 billion of dollars per year. Their mortality is about 12% whereas sepsis mortality reaches 30-40%. The only instruments currently used against sepsis are early diagnosis and antibiotic therapies, but the mortality rate can also be decreased through an improvement of the patient's nutrition. The aim of this paper is to summarize the effects of vitamins A, B, C and E on the balance between pro-oxidants and anti-oxidants in the critical care setting to confirm "a beneficial care enhancing". MATERIALS AND METHODS: The peer-reviewed articles analyzed were selected from PubMed databases using the keywords "critical care", "intensive care", "critical illness", "sepsis", "nutritional deficiency", "vitamins", "oxidative stress", "infection", and "surgery". Among the 654 papers identified, 160 articles were selected after title and abstract examination, removal of duplicates and of the studies on pediatric population. Finally, only the 92 articles relating to vitamins A, C, E and the B complex were analyzed. RESULTS: The use of vitamins decreased morbidity and mortality in perioperative period and critically ill patients, especially in ICU. Among the most encouraging results, we found that the use of vitamins, both as monotherapy and in vitamins combinations, play a crucial role in the redox balance. Vitamins, especially vitamins A, C, E and the B complex, could help prevent oxidative damage through the breakdown of the oxidizing chemical chain reaction. CONCLUSIONS: Even if the results of the studies are sometimes discordant or inconclusive, the current opinion is that the supplementation of one or more of these vitamins in critically ill patients may improve their clinical outcome, positively affecting the morbidity and the mortality. Further, randomized studies are required to deeply understand the potentiality of a vitamin supplementation therapy and develop homogeneous and standardized protocols to be adopted in every critical care scenario.

Non-infarctual ST elevation and acute cardiopulmonary failure in carbon monoxide poisoning: a case report.

OBJECTIVE: Carbon monoxide is produced by the incomplete combustion of organic fuel. In the United States, it is responsible for about 500 deaths annually. Increased carboxyhemoglobin concentration and hypoxia disrupt cardiac myocyte integrity and cause dysrhythmias, acute cardiac failure and coronary artery disease. We described a case of a patient with CO-poisoning and ST elevation at ECG precordial leads who developed severe transient heart failure. CASE PRESENTATION: A 57-year-old man was admitted to the emergency department for acute carbon monoxide poisoning that led to respiratory and cardiac failure. The electrocardiogram showed ST elevation in precordial leads, but the coronary angiography was normal. The patient was successfully treated and discharged. Three days later he was readmitted for similar symptoms and subsequently died. We hypothesize that the ECG findings were related to transient coronary vasospasm due to CO poisoning and that acute respiratory and cardiac failure related to carbon monoxide toxicity caused death. CONCLUSIONS: The management of patients poisoned by carbon monoxide requires early identification and intensive treatment and a careful evaluation of the home environment prior to discharge. ST elevation in such patients may be related to coronary vasospasm.

A survey of the management of spinal-induced hypotension for scheduled cesarean delivery.

BACKGROUND: Intravenous fluids and vasopressors are used for managing spinal-induced hypotension during cesarean delivery, but the choice of vasopressor and the type and timing of fluid administration remain controversial. METHODS: We conducted an electronic survey of all members of the Society for Obstetric Anesthesia and Perinatology between February and March 2007 to determine their preferences for preventing and treating spinal-induced hypotension with respect to fluid and vasopressor administration. RESULTS: The response rate was 292/746 (39%). Fifty percent worked in academic institutions and 56% had >50% of their clinical responsibility to obstetric anesthesia. For prophylaxis, 35% used fluid preloading, 30% fluid preloading with vasopressors, and 12% fluid co-loading with vasopressors. Of those using vasopressors for prophylaxis, 32% used ephedrine, 26% used phenylephrine, and 33% based their choice on heart rate. For treatment, 32% used ephedrine, 23% used phenylephrine, and 41% used either agent based on heart rate. Anesthesiologists in academic practice were less likely to use fluid preloading only (P=0.028) and more likely to use fluid co-loading and vasopressors (P=0.003). They were also more likely to administer phenylephrine for prophylaxis compared with those in private practice (P=0.042). CONCLUSION: Significant variations in practice exist in the prevention and treatment of spinal-induced hypotension. Fluid preloading and the prophylaxis and treatment of hypotension with ephedrine continue to be common practices.

Multidisciplinary management of placenta percreta complicated by embolic phenomena.

Hemorrhage and thrombosis are major causes of maternal mortality. This case discusses the management of a woman with placenta percreta complicated by intraoperative pulmonary embolism. A 39-year-old gravida 3 with two previous cesarean deliveries presented at 34 weeks of gestation with an antepartum hemorrhage. Magnetic resonance imaging confirmed placenta percreta. The multidisciplinary group including obstetricians, gynecological oncologists, interventional radiologists and anesthesiologists developed a delivery plan. Cesarean delivery was performed with internal iliac artery occlusion and embolization catheters in place. After the uterine incision our patient experienced acute hypotension and hypoxia associated with a drop in the end-tidal carbon dioxide and sinus tachycardia. She was resuscitated and the uterus closed with the placenta in situ. Postoperatively, uterine bleeding was arrested by immediate uterine artery embolization. With initiation of embolization, hypotension and hypoxia recurred. Oxygenation and hemodynamics slowly improved, the case continued and the patient was extubated uneventfully at the end of the procedure. Computed tomography revealed multiple pulmonary emboli. The patient was anticoagulated with low-molecular-weight heparin and returned six weeks later for hysterectomy. Placenta percreta with invasion into the bladder can be catastrophic if not recognized before delivery. The chronology of events suggests that this may have been amniotic fluid emboli. An intact placenta with abnormal architecture, such as placenta percreta, may increase the risk of amniotic fluid embolus. The clinical findings and co-existing filling defects on computed tomography may represent a spectrum of amniotic fluid embolism syndrome.

Reversible nitrous oxide myelopathy and a polymorphism in the gene encoding 5,10-methylenetetrahydrofolate reductase.

We present a case of a patient who received nitrous oxide on two occasions within a period of 8 weeks and who subsequently developed a diffuse myelopathy, characterized by upper extremity paresis, lower extremity paraplegia and neurogenic bladder. Laboratory testing revealed hyperhomocysteinaemia and low levels of vitamin B(12). Because of this uncommon clinical presentation, we analysed the patient's DNA, and found a polymorphism in the MTHFR gene that is associated with the thermolabile isoform of the 5,10-methylenetetrahydrofolate reductase enzyme, which explained the myelopathy experienced by the patient after being exposed to nitrous oxide. Soon after initiating supplementary therapy with folic acid and vitamin B(12), the neurological symptoms subsided.

Dural ectasia: a likely cause of inadequate spinal anaesthesia in two parturients with Marfan's syndrome.

We report two cases of Caesarean section in patients with Marfan's syndrome where continuous subarachnoid anaesthesia failed to provide an adequate surgical block. This was possibly because of dural ectasia, which was confirmed by a computed tomography scan in both cases.

Chondrocyte phenotype and cell survival are regulated by culture conditions and by specific cytokines through the expression of Sox-9 transcription factor.

OBJECTIVE: To investigate the effects of culture conditions, serum and specific cytokines such as insulin-like growth factor (IGF) 1 and interleukin (IL) 1alpha on phenotype and cell survival in cultures of Syrian hamster embryonic chondrocyte-like cells (DES4(+).2). METHODS: Proteins and RNA extracted from subconfluent and confluent early- and late-passage DES4(+).2 cells cultured in the presence or absence of serum and IL-1alpha or IGF-1 or both cytokines together were analysed for the expression of chondrocyte-specific genes and for the chondrogenic transcription factor Sox-9 by Western and Northern blotting. Apoptosis was assessed by agarose gel electrophoresis of labelled low-molecular weight DNA extracted from DES4(+).2 cells and another Syrian hamster embryonic chondrocyte-like cell line, 10W(+).1, cultured under the different conditions and treatments. RESULTS: Early passage DES4(+).2 cells expressed chondrocyte-specific molecules such as collagen types alpha1(II) and alpha1(IX), aggrecan, biglycan and link protein and collagen types alpha1(I) and alpha1(X) mRNAs, suggesting a prehypertrophic chondrocyte-like phenotype. The expression of all genes investigated was cell density- and serum-dependent and was low to undetectable in cell populations from later passages. Early-passage DES4(+).2 and 10W(+).1 cells survived when cultured at low cell density, but died by apoptosis when cultured at high cell density in the absence of serum or IGF-1. IGF-1 and IL-1alpha had opposite and antagonistic effects on the chondrocyte phenotype and survival. Whereas IL-1alpha acting alone suppressed cartilage-specific gene expression without significantly affecting cell survival, IGF-1 increased the steady-state mRNA levels and relieved the IL-1alpha-induced suppression of all the chondrocyte-specific genes investigated; it also enhanced chondrocyte survival. Suppression of the chondrocyte phenotype by the inflammatory cytokine IL-1alpha correlated with marked down-regulation of the transcription factor Sox-9, which was relieved by IGF-1. The expression of the Sox9 gene was closely correlated with the expression of the chondrocyte-specific genes under all conditions and treatments. CONCLUSIONS: The results suggest that the effects of cartilage anabolic and catabolic cytokines IGF-1 and IL-1alpha on the expression of the chondrocyte phenotype are mediated by Sox-9. As Sox-9 appears to be essential for matrix production, the potent effect of IL-1alpha in suppressing Sox-9 expression may limit the ability of cartilage to repair during inflammatory joint diseases.

The basis for the development of a fuselage evacuation time for a ditched helicopter.

HYPOTHESIS: When a helicopter ditches or crashes in water, unless the buoyancy bags are inflated, it commonly sinks inverted. Thus, crew and passengers must make an underwater escape. It is postulated that later passengers in the escape sequence do not have the breath-holding ability to conduct a successful escape, particularly if the water is cold. This contributes to the 20-50% mortality rate in survivable accidents. METHODS: There were 132 immersed subject evaluations which were conducted in daylight and darkness to measure escape times from a helicopter underwater escape trainer, configured to the Super Puma, seated for 15 and 18 passengers. The subjects were highly experienced instructors or Navy clearance divers. RESULTS: The time from when each subject's head disappeared underwater until each subject surfaced and total fuselage evacuation time were measured and any problems hampering escape were noted. Breath-holding for the last subject out ranged from 28 to 92 s. An emergency breathing system was used by a minimum of four subjects each time and a maximum of 11 subjects in one condition. The buoyancy of the survival suit was the principal component that hampered escape. CONCLUSION: Breath-holding times were too long for the later subjects to escape without resorting to an EBS, in spite of the fact that they were highly trained. For regular crew and passengers flying over water, this would explain the high mortality, etc. Therefore, a new helicopter standard should be developed requiring fuselage design to accommodate total evacuation within 20 s from underwater. For current helicopters, where this cannot be achieved, passengers should be provided with some form of air supply, or, after ditching, the helicopter should be modified so that it will stay afloat on its side and retain an air space in the cabin.

The unanticipated difficult airway with recommendations for management.

PURPOSE: To review the current literature and generate recommendations on the role of newer technology in the management of the unanticipated difficult airway. METHODS: A literature search using key words and filters of English language and English abstracted publications from 1990-96 contained in the Medline, Current Contents and Biological Abstracts databases was carried out. The literature was reviewed and condensed and a series of evidence-based recommendations were evolved. CONCLUSIONS: The unanticipated difficult airway occurs with a low but consistent incidence in anaesthesia practice. Difficult direct laryngoscopy occurs in 1.5-8.5% of general anaesthetics and difficult intubation occurs with a similar incidence. Failed intubation occurs in 0.13-0.3% general anaesthetics. Current techniques for predicting difficulty with laryngoscopy and intubation are sensitive, non-specific and have a low positive predictive value. Assessment techniques which utilize multiple characteristics to derive a risk factor tend to be more accurate predictors. Devices such as the laryngeal mask, lighted stylet and rigid fibreoptic laryngoscopes, in the setting of unanticipated difficult airway, are effective in establishing a patient airway, may reduce morbidity and are occasionally lifesaving. Evidence supports their use in this setting as either alternatives to facemask and bag ventilation, when it is inadequate to support oxygenation, or to the direct laryngoscope, when tracheal intubation has failed. Specifically, the laryngeal mask and Combitube have proved to be effective in establishing and maintaining a patent airway in "cannot ventilate" situations. The lighted stylet and Bullard (rigid) fibreoptic scope are effective in many instances where the direct laryngoscope has failed to facilitate tracheal intubation. The data also support integration of these devices into strategies to manage difficult airway as the new standard of care. Training programmes should ensure graduate physicians are trained in the use of these alternatives. Continuing medical education courses should allow physicians in practice the opportunity to train with these alternative devices.

Comparison of epidural anaesthesia with ropivacaine 0.5% and bupivacaine 0.5% for caesarean section.

PURPOSE: To compare ropivacaine 0.5% with bupivacaine 0.5% for epidural anaesthesia for Caesarean section. METHODS: Healthy pregnant women, scheduled for elective Caesarean section were enrolled into this randomized, double-blind, parallel-group study. Epidural block was obtained with 20-30 ml of ropivacaine (group R) or bupivacaine (group B) and surgery started when anaesthesia was reached T6. Maternal heart rate and blood pressure and fetal heart rate were assessed before the test dose and at five minute intervals until the end of surgery. At the same intervals, sensory and motor block characteristics were determined. Apgar scores and Neurologic and Adaptive Capacity Scores (NACS) were determined after delivery. Adverse events were recorded. RESULTS: Sixty-five patients were enrolled and data from 61 were available for analysis; 30 ropivacaine and 31 bupivacaine. Time from the end of the last injection to the start of surgery was 46 +/- 13 min (mean +/- SD) in gp R and 53 +/- 25 min in gp B (P:NS). The median duration of analgesia varied between 1.7 and 4.2 hr in gp R and between 1.8 and 4.4 hr in gp B (P:NS). In patients who developed Bromage 4 block, it persisted longer in those in gp B (2.5 hr) than in gp R (0.9 hr) (P < 0.05). The quality of analgesia was satisfactory in 27/29 patients (93%) in gp R and 27/31 patients (87%) in gp B (P:NS), although supplemental i.v. opioid was required in ten and seven patients, respectively. The most common adverse events in the mother were hypotension (63% gp R and 61% in gp B) (NS) and nausea (30% and 58%, in group R and B, respectively) (P = 0.05). Apgar scores were 7 after five minutes in all neonates. CONCLUSION: Ropivacaine 0.5% and bupivacaine 0.5% provided effective epidural anaesthesia for Caesarean section although supplementation with i.v. opioid was commonly required.

Does epidural analgesia during labour affect the neonate?

Focus has changed from the immediate postpartum condition to the more long-term outcome of the neonate with respect to the use of epidural analgesia in labour. Anaesthesiologists have been slow to respond to the demand for this information. Newer analgesic agents and techniques may offer some advantage to the neonate; however, extensive study is still needed.

Double-blind comparison of epidural ropivacaine 0.25% and bupivacaine 0.25%, for the relief of childbirth pain.

PURPOSE: To evaluate the efficacy of ropivacaine 0.25% when administered epidurally for relief of labour pain and to compare it with bupivacaine 0.25%. METHODS: In a multicentre investigation, 60 ASA I and II labouring women were randomized in a double-blind fashion to receive either bupivacaine 0.25% or ropivacaine 0.25% administered epidurally by intermittent top-up for labour analgesia. Using a standardized technique, epidural analgesia was initiated after the woman received 10-15 ml-kg.1 crystalloid solution. Maternal blood pressure, heart rate, analgesia sensory level, degree of motor block and visual analogue pain scores were measured by the research nurse prior to, and at regular intervals, following the administration of analgesia. Total dose of local anaesthetic administered, duration of labour, mode of delivery, and maternal and fetal/neonatal side effects were noted. The fetus/neonate was assessed by the research nurse using the fetal heart rate tracing, Apgar scores at delivery and neonatal neurobehavioural assessments at 2 and 24 hr postnatally. Maternal and investigators' satisfaction with the analgesia achieved was assessed after delivery. RESULTS: No differences were found between the two agents in any of the variables studied. CONCLUSION: Ropivacaine 0.25%, when administered epidurally by intermittent top-ups for labour analgesia, was equally efficacious as bupivacaine 0.25%.

Continuous epidural ropivacaine 0.2% for analgesia after lower abdominal surgery.

The purpose of this study was to determine whether a lumbar epidural infusion of ropivacaine 0.2% would provide effective analgesia with an acceptably low incidence of motor blockade and side effects after lower abdominal surgery. After combined general and epidural anesthesia and surgery, 125 patients were randomly assigned to receive either saline or ropivacaine 0.2% at a rate of 6, 8, 10, 12, or 14 mL/h (Groups R6, R8, R10, R12, and R14, respectively) for 21 h. Supplemental analgesia, if required, was provided with intravenous patient-controlled analgesia with morphine. Data were collected at 4, 8, and 21 h, and included morphine consumption, pain scores at rest and with coughing, motor and sensory block, and adverse events. Cumulative morphine consumption was less in Groups R10, R12, and R14 compared with the saline group. At 4 h analgesia was better among patients receiving ropivacaine, but at 21 h pain scores were identical. Sensory blockade at 8 and 21 h was greater in the ropivacaine groups compared with the saline group. Approximately 30% of R8, R10, and R12 patients, and 63% of R14 patients had demonstrable motor block of the lower limbs at 21 hours. We conclude that lumbar epidural ropivacaine 0.2% reduces parenteral morphine requirements but has little effect on pain scores and may be associated with motor blockade.

Nutrient digestion by ileal cannulated dogs as affected by dietary fibers with various fermentation characteristics.

We studied the effects of dietary fibers with various fermentation characteristics on nutrient digestion at the distal ileum and in the total tract of dogs. The following high-protein (34%), high-fat (23%) diets were fed: 1) a control treatment (CON) with 0% supplemental fiber; 2) beet pulp (BP), 7.5%; 3) low-cellulose mixture (LCM), 2.5% cellulose + 5.0% pectin; 4) high-cellulose mixture (HCM), 5.0% cellulose + 2.5% pectin; or 5) Solka Floc (SF), 7.5% cellulose. Nutrient intakes by fiber-supplemented dogs were similar among treatment groups but greater (P < .05) than for dogs fed the control diet. Digestion of nutrients at the distal ileum was similar among groups except for fat: the dogs fed BP digested less fat than those fed the other sources of dietary fiber. Digestion of amino acids at the distal ileum was similar for all groups, except for lysine, which increased (P < .05) in digestibility as dietary cellulose concentration increased. Dogs consuming LCM had lower apparent ileal digestibility values for all nutrients, including most amino acids, than dogs consuming HCM or SF. Total tract digestion of DM and OM by dogs fed supplemental fiber was less (P < .05) than for dogs fed the control diet. The BP treatment was higher than other fiber treatments in total tract digestion of OM (P < .10) and total dietary fiber (P < .05). Total tract digestibilities of all nutrients exhibited either linear or quadratic responses to dietary cellulose concentrations. Apparent ileal and total tract nutrient digestion was influenced by the source of dietary fiber consumed.

Perioperative management of drug therapy, clinical considerations.

The objectives for the provision of a safe anaesthetic include rendering the patient analgesic for the procedure (amnesic if appropriate), with control of adverse haemodynamic perturbations, and muscle relaxation to facilitate surgery as necessary. This must be done with an understanding of the patient's pre-existing pathophysiology and drug therapy. This article focuses on the management of medications in the perioperative period from the practitioner's perspective. Areas of drug therapy examined include drugs affecting the cardiovascular, central nervous, haemostatic and endocrine systems. Review of the limited data available suggests that the safest course of action for the preoperative management of the vast majority of drug therapy is to continue such therapy until the time of surgery, particularly agents in which a withdrawal syndrome has been described, e.g. beta-adrenoceptor blocking agents, alpha 2-adrenoceptor agonists. Exceptions to this generalisation might include discontinuing ACE inhibitors prior to surgery as these agents may be associated with adverse haemodynamic changes during surgery. The management of drug therapy for patients receiving monoamine oxidase inhibitors (MAOIs) continues to be challenging due to the potential for drug interactions, e.g. severe hypertension with use of indirect-acting vasopressors and excitatory/depressive reactions with administration of pethidine (meperidine) or dextromethorphan. However, recent clinical experience has demonstrated the relative safety of continuing MAOIs prior to surgery by use of specific 'MAOI safe' anaesthetic techniques and/or substitution of short-acting MAOIs which do not irreversibly inhibit the enzyme. For drugs affecting the coagulation system, such as heparin and warfarin, prudence dictates discontinuing these agents whenever possible prior to surgery where it can be anticipated that haemorrhage will occur, e.g. vascular surgery, or where the consequences of even minor bleeding could be catastrophic, e.g. eye surgery. Controversy exists as to the management of patients receiving prophylactic low dose heparin for deep vein thrombosis prophylaxis or in whom intraoperative or postoperative anticoagulation is planned, e.g. aortic surgery, and in whom a regional anaesthetic technique is planned as part of the anaesthetic management. The data available suggest that, where prophylactic use of heparin is concerned, and provided the administration of the last dose of heparin and the institution of a regional anaesthetic nerve block does not occur at the same time, use of regional anaesthesia is not contraindicated in such circumstances. Where therapeutic anticoagulation is planned as part of the surgical management, there is a very small risk of the development of epidural or spinal haematoma when major central conduction nerve block is employed for anaesthesia, with resultant spinal cord compression and paralysis. These precautions do not apply to patients receiving aspirin or other nonsteroidal anti-inflammatory agents as there is a large clinical and published experience of the safety of regional anaesthesia in this group of patients. Patients treated with fibrinolytic agents are at increased risk for bleeding should surgery be required. For these patients, pre- and intraoperative use of agents with antifibrinolytic activity, e.g. aprotinin, has been demonstrated in case reports to be beneficial. Finally, recommendations for the management of patients who have received or are receiving glucocorticoids are given. Throughout the review, areas of uncertainty where further research is required are identified.

The chondrocyte, architect of cartilage. Biomechanics, structure, function and molecular biology of cartilage matrix macromolecules.

Chondrocytes are specialised cells which produce and maintain the extracellular matrix of cartilage, a tissue that is resilient and pliant. In vivo, it has to withstand very high compressive loads, and that is explicable in terms of the physico-chemical properties of cartilage-specific macromolecules and with the movement of water and ions within the matrix. The functions of the cartilage-specific collagens, aggrecan (a hydrophilic proteoglycan) and hyaluronan are discussed within this context. The structures of cartilage collagens and proteoglycans and their genes are known and a number of informative mutations have been identified. In particular, collagen fibrillogenesis is a complex process which can be altered by mutations whose effects fit what is known about collagen molecular structural functions. In other instances, mutations have indicated new functions for particular molecular domains. As cartilage provides the template for the developing skeleton, mutations in genes for cartilage-specific proteins often produce developmental abnormalities. The search for mutations amongst such genes in heritable disorders is being actively pursued by many groups, although mutation and phenotype are not always well correlated, probably because of compensatory mechanisms. The special nature of the chondrocyte is stressed in connection with its cell involvement in osteoarthritis, the most widespread disease of diarthrodial joints.

Expression of cartilage-specific molecules is retained on long-term culture of human articular chondrocytes.

Normal human adult articular chondrocytes were used to determine how the chondrocyte phenotype is modulated by culture conditions following long-term culture. We report here for the first time that human articular chondrocytes have a lifespan in the range of 34-37 population doublings. While chondrocytes cultured as monolayers displayed a fibroblastoid morphology and grew faster, those cultured as suspensions over agarose adopted a round morphology and formed clusters of cells reminiscent of chondrocyte differentiation in intact cartilage, with little or no DNA synthesis. These morphologies were independent of the age of the culture. Despite, these morphological differences, however, chondrocytes expressed markers at mRNA and protein levels characteristic of cartilage: namely, types II and IX collagens and the large aggregating proteoglycans, aggrecan, versican and link protein, but not syndecan, under both culture conditions. However, they also expressed type I collagen alpha 1(I) and alpha 2(I) chains. It has been suggested that expression of collagen alpha 1(I) by chondrocytes cultured as monolayers is a marker of the loss of the chondrocyte phenotype. However, we show here, using reverse transcriptase/polymerase chain reaction, that normal fresh intact human articular cartilage expresses collagen alpha 1(I). The data show that following long-term culture human articular chondrocytes retain their differentiated characteristics and that cell shape does not correlate with the expression of the chondrocyte phenotype. It is proposed that loss of the chondrocyte phenotype is marked by the loss of one or more cartilage-specific molecules rather than by the appearance of non-cartilage-specific molecules.

A psychophysiological approach to the assessment of work underload.

The findings of a laboratory investigation of the relationship between the subjective and physiological components of work underload are reported. The subjective component is described in terms of the subjective work underload checklist, mental effort, and cognitive arousal. The physiological component is defined in terms of heart rate and heart rate variability. Evidence for an increase in work underload with a decrease in heart rate is provided. The relevance of this research to the aerospace environment is discussed and the need to investigate the behavioural component of work underload emphasized.