Positive airway pressure

Positive airway pressure (PAP) includes continuous positive airway pressure (CPAP) and expiratory positive airway pressure (EPAP). Application of PAP increases intraluminal pressure and prevents the collapse of the bronchioles and alveoli. The increased pressure provides better conditions for the functioning of the diaphragm. The optimum level of PAP has not been clearly defined. EPAP (exhalation against a threshold resistor) increases the work of the diaphragm, permitting the patient to...

Ventilatorinduced pulmonary edema lung injury and volutrauma

In excess of 20 000 tidal ventilatory cycles are undertaken daily. Ventilatory patterns that apply high transalveolar stretching forces cause or extend tissue edema and alveolar damage in experimental animals, even when alveolar rupture does not occur. Maximum alveolar pressures above 30 cmH 2O commonly produce regional overdistension in patients with acute respiratory distress syndrome. Peak tidal pressures of this magnitude cause tissue damage in experimental animals when ventilation is...

Posthypoglycemic coma

Prolonged hypoglycemia, particularly in association with hypoxemia and hypotension, leads to cerebral edema. Recovery may be delayed despite the attainment of normoglycemia, a condition historically termed 'irreversible hypoglycemic coma' but better described as 'post-hypoglycemic coma'. The delay probably reflects the severity of underlying brain damage. In addition to the measures outlined above to restore normoglycemia, additional interventions to reduce cerebral swelling are required, such...

Central nervous system effects

Autoregulation is highly prominent in vascular beds of the heart, kidneys, and lungs, but is most important in the cerebral circulation. In the normal state, cerebral autoregulation maintains a stable cerebral blood flow rate despite fluctuations in mean arterial pressure over a range of 60 to 150 mmHg. When the upper limit of cerebral autoregulation is exceeded for a period of time, hypertensive encephalopathy results, with cerebral edema, petechial hemorrhages, and microinfarcts. This is...

Increased anion gap metabolic acidoses

The major causes of increased anion gap acidosis are lactic acidosis, ketoacidosis, uremia, salicylate overdose, and poisoning by methanol, ethylene glycol, and other toxins. Lactic acidosis is an important cause of increased anion gap acidosis in the critically ill. The pathway of lactate metabolism is shown in Fig 2 Under normal conditions, lactate is produced by a variety of tissues and is metabolized in the liver and kidneys, where it may be converted back to glucose. Hyperlactatemia occurs...

Changes in drug metabolism

In hypothyroidism, there is a general slowing down of most metabolic processes, particularly those of drugs, whose tolerance is therefore reduced ( Nicoloff and LoPresti 1993). 1. Digoxin the half-life is longer because of a slowing down of the rate of peripheral metabolism and reduced glomerular filtration. A high risk of digoxin intoxication is present in myxedema coma. 2. Diuretics overdosage is frequent, aggravating hypovolemia in myxedema coma. 3. Tranquilizing agents, sedatives,...

Cytokines and the classical stress hormone system

Current evidence points to a significant interdependence of the neuroendocrine axis and the cytokine mediator systems. For example, the exogenous administration of tumor necrosis factor elicits increased secretion of ACTH, cortisol, catecholamines, and growth hormone. These interdependent mediator systems also exhibit negative feedback. For example, glucocorticoids reduce tumor necrosis factor and IL-1 transcription. The cytokines may also serve to attenuate the magnitude of the postinjury...

Cardiovascular assistance

Continuous cardiac monitoring is vital (Table2). Table 2 Safety of methods of cardiovascular assistance Hypotension indicates an unfavorable prognosis (Tabje.3) and is sometimes a sign of an irreversible phase of the illness, since hypothyroid patients usually have mild diastolic hypertension (HyJ. nd IaDd Rosengvj.stlll1985 Roti e.L L 1993). Several other factors, such as blood loss by gastrointestinal bleeding (which should be sought and treated), aggressive warming, and overuse of diuretics,...

Ihe neurological system

7.4 Raised intracranial pressure and cerebral edema 7.4.1 Pathophysiology of generalized cerebral edema 7,4,2lllP.ath0P,h.ys,il0.l0.gyll oLs a.ce-oc.cupyingi lesions 7.4.3 Diagnpsis, .pfraised intracranial pressure 7 l4l.l4 M.a.nag.e.m.e n.t , ofcerebrall .edema 7.5 Npn-traumatic intracranial hemprrhage 7 5.3 Xh.e.M rp.l.e ofsurgical management 7 6.1 Path.pphysiolpgynand .causes 7.6.2 Ih.erafi.eutic approach M. Levin and S. Nadei 7 l7l 1.P.ath.pp.h.ys,ilPlpg.y., and .causes R. P. Paczynski and...

Torsemide torasemide Miscellaneous cardiac drugs

Amrinone Dobutamine Dopamine Milrinone Nitroglycerine Nitroprusside Barbiturates Pentobarbital (pentobarbitone) Phenobarbital (phenobarbitone) Secobarbital (quinalbarbitone) Benzodiazepinesm Chlordiazepoxide Diazepam Lorazepam 15-75 pg kg IV Many routes and methods 0 Three times daily Twice daily Every 24 h Twice daily Three to four times daily Two to three times daily Three to four times daily GFR, glomerular filtration rate ACE, angiotensin-converting enzyme IV, intravenous. Performing...

Physiology of normal sleep

Observation and electrophysiological (EEG) examination of sleep have led to the recognition of two distinct phases of sleep slow-wave or non-rapid eye movement (NREM) sleep (approximately 80 per cent of total sleep time), and rapid eye movement (REM) sleep (20 per cent of total sleep time). Following a period of 10 to 20 min of sleep latency, individuals enter NREM sleep which is divided into four stages, each characterized by its EEG pattern. Stage I NREM, which accounts for 10 per cent of...

Detection of respiratory muscle fatigue

Diaphragmatic fatigue can be detected in various ways (DMrey I and, Aybi I 1988). Assessment of fatigue for the diaphragm is more difficult than for other skeletal muscles because the tension generated cannot be measured directly only the mechanical transformation of that tension into pressure can be measured. The transdiaphragmatic pressure (Pdi), defined as the difference between the gastric pressure and the esophageal pressure, closely reflects the tension produced by the contracting muscle....

Approach to increased anion gap metabolic acidosis

An approach to the assessment of increased anion gap acidosis is summarized in Table, . Table 2 Diagnosis of increased anion gap metabolic acidosis Table 2 Diagnosis of increased anion gap metabolic acidosis Ketoacidosis can be diagnosed by measurement of ketones in serum and urine blood glucose should also be measured. Ketoacidosis generates both acetone and b-hydroxybutyrate. However, only acetone is detected when measuring urine and serum ketones. If both acetone and b-hydroxybutyrate are...

Autonomic nervous system

The increased basal sympathetic tone may manifest as tachycardia and alteration of bladder function and bowel motility. Episodes of marked sympathetic overactivity occur, with increased vascular resistance, increased central venous pressure, increased cardiac output, hypertension, pallor, cyanosis of the digits, pyrexia, and sweating. These sympathetic crises are thought to be mediated by loss of spinal inhibition of the adrenal glands. Therefore epidural anesthesia may attenuate or eliminate...

Plugged telescoping catheter brush sampling

In 1979 Wimberley described a plugged telescoping catheter for use in sampling respiratory secretions ( Fagon et al 19.8.8.). This system was the most effective at resisting contamination in vitro when passed through a bronchoscope heavily contaminated with saliva. The bronchoscope is positioned at the appropriate bronchial orifice, the plugged telescoping catheter (e.g. Medi-Tech, Key-Med, United Kingdom) is advanced 2 cm into the segmental bronchus, and then the inner catheter is advanced a...

The effect on hepatosplanchnic circulation and function

This effect is difficult to evaluate because of the complex interactions between the forces generated by elevated intrathoracic pressure and the autoregulatory responses of the hepatic vasculature. Although understanding of hepatic circulatory physiology has considerably increased, mechanisms involved in the regulation of liver blood flow have yet to be fully elucidated. Mechanical ventilation with positive end-expiratory pressure (PEEP) decreases cardiac output by reducing venous return. The...

Adrenergic receptor agonism

Inotropic activity is mediated through cardiac b -,-adrenergic receptors. In addition to an enhanced force of contraction (inotropy), stimulation of the b rreceptor also results in a variable degree of increase in sinus node firing rate (chronotropy), an increase in atrioventricular conduction velocity (dromotropy), and a decrease in the Beta-2-receptors and a1-adrenergic receptors also exist in the myocardium and may mediate an important component of inotropic effect in the presence of chronic...

Diffusion impairment

The true clinical significance of impaired oxygen diffusion is debatable, except during exercise and other high-output states. The diffusing capacity is defined as DLq Qi uptake I' 'AOj mean pulnwnOTapilhry Yij). (4) The capillary transit time, which equals the pulmonary capillary blood volume divided by the pulmonary blood flow (or cardiac output), determines the mean pulmonary capillary PO2. Therefore the factors that contribute to a decreased oxygen diffusion capacity are shorter capillary...

Acute mucosal ulceration

Peptic ulcers may recur during critical illness. However, other forms of acute ulceration of the gastroduodenal mucosa are more commonly encountered in critically ill patients without actual association with peptic ulcer disease. This mucosal injury is often referred to as a stress ulcer. However, the pathological anatomical definition of this lesion is an erosion (a superficial lesion not penetrating the mucosa). In contrast, an ulcer by definition penetrates at least down to the muscular...

Thermodilution cardiac output

The thermodilution method for measuring cardiac output, after injection of the thermal indicator through the central venous port and registration of the temperature change by the thermistor at the distal port of the pulmonary artery catheter, has been extensively validated by comparison with the gold standard, i.e. the cardiac output calculated, using the Fick principle, from measurements of the oxygen uptake (indirect calorimetry, analysis of inspiratory and expiratory breath) and the arterial...

Transforaminal herniation

Displacement of one or both cerebellar tonsils through the foramen magnum ( Fig, 3) is a common occurrence in patients with posterior fossa mass lesions and usually precedes upward cerebellar herniation. Although the condition may be tolerated for considerable periods of time without noticeable symptoms, neck tilt or nucal rigidity is often evidence on physical examination. Such findings must be carefully distinguished from neck stiffness resulting from meningitis or subarachnoid hemorrhage....

Pseudomonas aeruginosa

Ps. aeruginosa is a motile aerobic Gram-negative bacillus that may appear singly, in pairs, or in short chains. It can be isolated from soil, water, plants, and animals, including humans. Since it thrives in a moist environment, human colonization often occurs in sites such as the perineum and external ear. Normal human colonization rates are as follows skin, zero to 2 per cent nasal mucosa, zero to 3 per cent throat, zero to 7 per cent stool, 3 to 24 per cent. Potential hospital reservoirs...

Indications for platelet transfusion

A. bone marrow failure (hematological malignancy, post-chemotherapy, aplastic anemia) b. disseminated intravascular coagulation (DIC) d. immune thrombocytopenia (only in severe bleeding). b. acquired (cardiopulmonary bypass surgery, drug induced (aspirin), uremia). Platelet transfusions are contraindicated in thrombotic thrombocytopenic purpura, hemolytic uremic syndrome, and heparin-induced thrombocytopenia because the underlying tendency is for thrombosis rather than bleeding.

Assessment of disorders of coagulation in critical care medicine

Bleeding, thrombosis, or a combination of bleeding and thrombosis, as seen in DIC, are the three major presentations of coagulation disorders in critical care medicine. Clinical history is the mainstay for recognition and diagnosis of a clinically significant bleeding state or predisposition for developing thrombosis. History should be verified for bleeding complications after previous surgical procedures, trauma, or tooth extraction. Family history may raise uspicion of a hereditary...

Hemostasis and rheology

The prothrombin and activated partial thrombin times should normalize by the third postoperative day if the graft is working. Preoperative thrombocytopenia does not always respond to platelet transfusion and usually takes longer (up to a week or more) to recover. Hemoglobin concentration should not exceed 10 g dl to avoid increasing blood viscosity and the risk of portal or hepatic arterial occlusion. Clotting factors should not be given routinely because the prothrombin time is a valuable...

Assessment of individual organ failure

The degree of failure of six main organs can be assessed as follows, although the gastrointestinal tract is an elusive organ to evaluate. 1. Respiratory function is best assessed by the evaluation of gas exchange, most commonly using the Pao2 Fio2 ratio. The need for mechanically assisted ventilation may be taken into account. 2. Renal function urea (or blood urea nitrogen), and creatinine levels can adequately assess the degree of renal dysfunction. The creatinine clearance may be a more...

Chapter References

Magann, E.F., Bass, D., Chauhan, S.P., Sullivan, D.L., Martin, R.W., and Martin, J.N. (1994 a). Antepartum corticosteroids disease stabilization in patients with the syndrome of hemolysis, elevated liver enzymes, and low platelets (HELLP). American Journal of Obstetrics and Gynecology, 171, 1148-53. Magann, E.F., Perry, K.G., Meydrech, E.F., Harris, R.L., Chauhan, S.P., and Martin, J.N. (1994 b). Postpartum corticosteroids accelerated recovery from the syndrome of hemolysis, elevated liver...

Maternal and fetal outcome

The most feared, but fortunately rare, complications of HELLP are liver subcapsular hematoma and rupture with shock. Other maternal complications include aggravation of thrombocytopenia with coagulation disorders or disseminated intravascular coagulation (DIC). Depending on definition, DIC occurs in up to 21 per cent of cases, but seems mainly related to the presence of abruptio placentae which represents the second most common complication (Table,1). Acute renal failure, congestive heart...

Complications of massive transfusion

Hemostasis may already be abnormal due to the underlying condition. During massive transfusion of red cells, platelet numbers fall as few functioning platelets exist in whole blood that has been stored for more than 48 h. Factors V and VIII are reduced after storage for a few days, and remaining levels may be diluted if large volumes of intravenous crystalloid or colloid are given. In addition, DIC may be provoked by release of thromboplastin-like material from platelets, white cells, and red...

Microvascular thrombosis

Microvascular thrombosis is a characteristic of a variety of conditions (T.able ,.3)> including DIC, thrombotic thrombocytopenic purpura, and the purpura ulminans syndrome. These conditions may also be associated with large-vessel thrombotic manifestations, both arterial and venous. In DIC clinical attention is often directed towards the bleeding manifestations microvasular thrombosis causing endorgan damage may go unrecognized unless it is overt. The microangiopathic process in thrombotic...

Management of venous thromboembolism in the ICU

In the ICU patient both deep vein thrombosis and pulmonary embolism are likely to be silent and may therefore go unrecognized. Clinical suspicion of venous thromboembolism merits urgent consideration of therapeutic anticoagulation with intravenous heparin. Objective testing for thromboembolic disease, although necessary, may be logistically problematic and therefore restricted, limiting precise definition of the incidence of thromboembolic events. Prior to the commencement of anticoagulation, a...

Class Ia drugs quinidine procainamide disopyramide

Quinidine used to be popular as an effective antiarrhythmic agent against both supraventricular and ventricular arrhythmias, but has fallen into disuse after a large meta-analysis suggested excess mortality due to drug-induced torsade de pointes. Quinidine directly suppresses sinus node and atrioventricular node conduction and increases the refractory period of atrial, ventricular, and His-Purkinje tissue, although an anticholinergic action may increase atrioventricular nodal conduction. The...

Thromboprophylaxis for the ICU patient

Critically ill patients frequently have several coexistent risk factors for thromboembolic disease, in particular prolonged immobility, surgery, and indwelling vascular access catheters. Therefore they may benefit from thromboprophylaxis. However, they may also be at increased risk of hemorrhage due to recent surgery, hemostatic dysfunction secondary to renal failure (which also reduces heparin clearance), severe hepatic disease, or thrombocytopenia. These factors are relative contraindications...

Differential diagnosis

DIC needs to be differentiated from various other medical conditions. Prolongation of the prothrombin and partial thromboplastin times, thrombocytopenia, hypofibrinogenemia, and a raised level of fibrin degradation products all may occur in liver disease in difficult cases, assay of factor VIIIc may be helpful (low in DIC but normal or raised in liver disease). Critically ill patients may develop a coagulopathy due to vitamin K deficiency a therapeutic trial of the vitamin may clarify whether...

Treatment of fulminant hepatic failure

The management of fulminant hepatic failure resulting from acetaminophen overdose is based on good intensive care. Optimum management should be directed towards resuscitation and preparation for urgent and safe transfer. Control and protection of the airway is fundamental, particularly as these patients can rapidly become deeply encephalopathic. Sedatives are contraindicated, and patients who cannot be managed safely should be ventilated. Intravenous fluid resuscitation is always necessary and...

Peep Cpap and autoPEEP

Passive expiratory airflow dynamics and the necessity for long expiratory times have lead to the concept of 'auto-PEEP' and to consideration of the potential gains that might be achieved by the addition of PEEP or continuous positive airways pressure (CPAP). Although there is anecdotal evidence supporting the use of PEEP and CPAP, undesirable effects on the cardiovascular system, particularly in a volume-depleted patient, represent a significant hazard. If one of the major goals is to avoid...

Additional evaluation

Additional evaluation may be of aid in the diagnosis of acute uremia. Severe hypocalcemia at the onset of oliguria occurs in rhabdomyolysis and pancreatitis. Very high levels of uric acid accompany tumor lysis, trauma, or muscle damage. Eosinophilia is frequent in acute interstitial nephritis. Hemolytic uremic syndrome and thrombotic thrombocytopenic purpura are characterized by hemolytic anemia, thrombocytopenia, and the presence of schistocytes, and disseminated intravascular coagulation is...

Hemodynamic stabilization

Two large-bore intravenous cannulas should be placed to allow fluid access and administration of medication. In a few patients, survival is threatened by the actual volume of blood lost through hemoptysis. Intravenous fluid should be administered commensurate with the vital signs. Routine laboratory analysis should include a hematocrit, platelet count, coagulation profile, arterial blood gases, and renal function studies. Blood should also be typed and cross-matched in case transfusion is...

The cerebrospinal fluid inflammatory response

Once the organism has invaded the cerebrospinal fluid, a number of bacterial components, particularly lipopolysaccharide or lipo-oligosaccharide of Gram-negative organisms and peptidoglycan are the major determinants of meningeal inflammation. The techoic acid of Gram-positive organisms and the peptidoglycan components of both Gram-positive and Gram-negative organisms have been shown to be potent inducers of inflammation in the cerebrospinal fluid and to impair blood-brain barrier function on...

Hepatic pressureflow relationships

Liver perfusion must be maintained in a wide variety of clinical conditions characterized by either low downstream right atrial pressures (e.g. during hypovolemic shock) or high downstream pressures (e.g. pulmonary hypertension). The existence of hepatic vascular waterfalls then represents a protective mechanism for the liver against high increases in central venous and hepatic venous pressures. By using an extracorporeal bypass from the right atrium to the pulmonary artery, flow can be...

Communication

Inability to communicate with the patient can also cause frustration. Nurses may feel incompetent because their patients cannot communicate seemingly important messages to them (Bergbom-EDgberg aDd H.,a.lja.,m ai 1993). Talking with relatives is a skill usually learned from experience rather than training. At times this can be stressful since the ICU staff have to remain calm and objective even when relatives or patients are rude, abusive, or aggressive. Death and dying are a common fate of...

Alterations at cellular level

Many of the enzymatic reactions of neurons, glial cells, and specialized cerebral capillary endothelium in the brain must be catalyzed by the energy-yielding hydrolysis of adenosine triphosphate (ATP) to adenosine diphosphate (ADP) and inorganic phosphate. Without a constant and generous supply of ATP, cellular synthesis slows or stops, neuronal functions decline or cease, and cell structures quickly fall apart. The brain depends entirely on the process of glycolysis and respiration within its...

Amniotic fluid embolism

The mainstay for diagnosis of amniotic fluid embolism should be a typical clinical picture such as cardiorespiratory failure of abrupt onset that occurs during the third trimester of pregnancy or around delivery, and which is followed by the development of pulmonary edema and coagulopathy. Demonstration of trophoblastic and squamous cells in the pulmonary artery vasculature is by no means pathognomonic of this condition. Similar cells have been recovered in the peripheral blood of normal...

Psychological effects

Psychological distress can easily derive from unrelieved pain and plays a major role in the initiation and maintenance of the stress response. Pain can promote anxiety and fear. Anxiety stimulates the fight or flight response that focuses an individual's attention on avoiding further injury. Anxiety by itself can initiate the neuroendocrine stress response. Both anxiety and pain can lead to insomnia. Pain, anxiety, and sleep deprivation increase the perception of each other, resulting in a...

Inflammatory mediators

Tumor necrosis factor-a, IL-1b, and IL-6 are the archetypal proinflammatory cytokines, and they can all influence immune cell function, inhibit lymphocytes, and alter normal phagocyte function (Mannick 19.9.3). IL-6 has a role in the immune response to infection and is synergistic with platelet activating factor in neutrophil priming, possibly leading to an inappropriate inflammatory response. IL-10, the classic anti-inflammatory cytokine, suppresses T cells. IL-4 promotes T- and B-cell...

Acute adrenal insufficiency adrenal crisis

Acute adrenal insufficiency is a true endocrinological emergency. It usually presents as shock in a previously undiagnosed patient with (primary) hypoadrenalism who has been subjected to major stress or in a patient with established hypoadrenalism who does not or is not able to increase glucocorticoid replacement during an intercurrent illness or injury. A febrile illness, bacterial infection, trauma, surgery, dehydration, or any other intercurrent illness in these patients can trigger acute...

Ventilatory modes of weaning

Ventilatory modes of weaning are based on a progressive reduction in the contribution of the ventilator and a progressive increase in the patient's contribution to ventilation. While moderate muscle activity is desirable for successful weaning, the extent of muscle exertion required and the value of muscle training remain unknown. The ventilatory modes commonly used for weaning are T-tube breathing and the two patient-assisted modes, intermittent mandatory ventilation and pressure support...

Growth hormone deficiency

Growth hormone is a polypeptide with anabolic effects on protein metabolism and with lipolytic and immunostimulating properties ( Ihornerefal 199.2). It is secreted by pituitary somatotropes in a pulsatile fashion that is believed to result principally from a dynamic interaction between two hypothalamic neuropeptides, the stimulatory growth-hormone-releasing hormone and the inhibitory somatostatin. Growth hormone has direct and indirect anabolic actions the principal mediator of the latter is...

Incentive spirometry

Incentive spirometry, which is also known as sustained maximal inspiration, is the most widely used method of bronchial hygiene therapy, but it requires the co-operation of the patient. It attempts to mimic the natural sighing or yawning that a healthy subject performs nine or ten times every hour. The patient is encouraged to take long slow deep breaths. Maximum inspiration is facilitated by using an indicator (usually visual) that informs the patient that he or she has produced sufficient...

Toxicokinetic antidotes

Antidotes work by two different global mechanisms, i.e. by affecting either the toxicodynamic properties of the intoxicant (hemodynamics, binding at tissue sites) or the toxicokinetic properties (absorption, distribution, elimination) ( Baud ef a 1995). Because the latter group of antidotes may affect elimination, several examples are Digitalis antigen-binding fragments (Fabs) have very rapid pharmacodynamic effects (reduction of tissue binding and improvement in hemodynamics with reduction in...

Methylated xanthines theophylline and aminophylline

Theophylline is inferior to b-agonists as first-line treatment of acute asthmatic attacks, although it may have a synergistic action with b-agonists. It can be combined with ethylenediamine (aminophylline) to become 20 times more soluble than theophylline alone. The mode of action of theophylline is unclear, but it is known to inhibit the enzyme phosphodiesterase to decrease the metabolism of cyclic AMP. The dose necessary for this action is much higher than that used clinically. Theophylline...

Status epilepticus

Attention to basic life-support issues (airway, breathing, and circulation) is central to the management of generalized convulsive status epilepticus. While the rapid termination of this condition is often the best way to deal with airway problems, emergent endotracheal intubation may be necessary for the patient unable to ventilate adequately or if treatment to terminate status epilepticus causes respiratory depression. Blind nasotracheal intubation is preferable for patients able to move air...

Intracranial pressure monitoring

Intracranial pressure (ICP) data form the basis for guiding the management of comatose head injury patients whose clinical examination is usually compromised by sedation and or chemoparalysis. The Guidelines for the Management of Severe Head Injury published by the American Association of Neurological Surgeons recommend that ICP monitoring be undertaken in patients with a head injury and an abnormal CT scan on admission. ICP monitoring may also be undertaken in patients with severe head injury...

Paroxysmal junctional tachycardia

This may occur and is identical to paroxysmal supraventricular tachyarrhythmia in rate and configuration. Ventricular tachyarrhythmias Ventricular premature complexes Ventricular premature complexes arise below the bundle of His, prematurely depolarizing the ventricular myocardium and resulting in wide complexes with no preceding P wave. These beats are usually blocked in the atrioventricular node and there is no retrograde depolarization of the atrium. The sinus node continues to fire at its...

Initial assessment

The prognosis for patients with burn injuries is determined by the size, depth, location, and type of burn as well as related factors such as age, pre-existing conditions, and associated injuries (Djmjcki.,1994.). The size of a burn injury is usually expressed in terms of the percentage of the body surface area involved. This measurement is utilized to predict resuscitation fluid volumes and to assess prognosis. Unfortunately, this number is not readily apparent on inspection of the patient....

Burns and electroporation

With high-voltage injuries there is charring and loss of tissue at the contact points this is due to the current encountering high skin resistance (heat amperage 2 * resistance * time). A low current contact may leave no evidence on the skin. Once penetration of the skin has occurred, current will flow along unpredictable routes through the body according to the resistances encountered. Any organ in the current path may be severely damaged as joule heating causes intolerable rises in...

COP measurement in the critically ill

The ability of the capillary to impede transfer of plasma proteins is impaired in the critically ill ( Fleck ef a 1985). The reflection coefficient of the capillary wall is reduced and the COP difference becomes less effective. The COP is commonly less than 20 mmHg in the critically ill as albumin leaks out of the circulation. Formulas to calculate COP are reasonably accurate in health. However, formulas based upon albumin concentration severely underestimate measured COP in the critically ill...

Aminophylline

Intravenous aminophylline is usually regarded as a second-line drug because of its narrow therapeutic range and the high incidence of side-effects the most serious of these are cardiac arrhythmias and seizures. The value of aminophylline in acute severe asthma is uncertain. Its mechanism of action is unclear at therapeutic concentrations the inhibition of phosphodiesterase is minimal and it is a relatively weak bronchodilator, providing a third of the bronchodilatation of sympathomimetics....

Hyperglycemia in the critically ill

Hyperglycemia can be either the primary problem, as in diabetic emergencies, or a result of other processes, such as hyperglycemia secondary to sepsis. Diabetic emergencies Diabetic ketoacidosis Diabetic ketoacidosis is the most common form of diabetic emergency. It is part of the spectrum of diabetic emergencies (Table 1) which have varying degrees of hyperglycemia, acidosis, and ketosis. Table 1 A comparison of clinical and biochemical indices in the spectrum of diabetic emergencies Diabetic...

Herpes simplex encephalitis

The herpes family (herpes simplex I and II, cytomegalovirus, varicella zoster, Epstein-Barr) deserves special emphasis because of both the high rates of morbidity and mortality associated with these infections and the availability of effective pharmacotherapy for some. All herpes group viruses contain double-stranded DNA, and drugs of proven efficacy specifically target the viral encoded thymidine kinase enzyme that catalyzes viral DNA replication. Herpes simplex encephalitis is the most common...

Diagnosis of pleural effusions

Upright posterior-anterior chest radiography is the most commonly used diagnostic modality for pleural effusions. Accumulation of pleural fluid occurs first under the lung at the base of the hemithorax. Pleural effusions greater than 300 ml will usually obliterate the costophrenic angle. Larger effusions will cause opacification of the hemithorax. Lateral decubitus views confirm the presence of free pleural fluid and are more sensitive than upright films for the detection of effusions....

Effect on cerebral hemodynamics and brain function

Elevated intrathoracic pressure caused by mechanical ventilation with PEEP may influence cerebral hemodynamics by several mechanisms, particularly if cerebral blood flow regulation is impaired and pressure dependent. PEEP-related changes in the systemic circulation (decreased venous return, decreased mean arterial pressure (MAP)) will decrease cerebral arterial inflow. Moreover, application of PEEP may increase cerebral venous pressure and intracranial pressure (ICP), and thus further decrease...

Magnesium

A loading dose of 70 mg kg magnesium sulfate followed by an infusion of 1 to 4 g h to keep serum levels between 2.5 and 4 mmol l reduces systemic vascular resistance, pulse rate, and to a small extent cardiac output. The release of epinephrine (adrenaline) from the adrenal gland and norepinephrine (noradrenaline) from peripheral nerve terminals is inhibited and the sensitivity of receptors to these neurotransmitters is reduced. Magnesium also has a marked neuromuscular blocking effect, and may...

Acute intrinsic renal failure

Between 25 and 40 per cent of cases of ARF are ascribed to intrinsic renal damage, predominantly induced by prolonged renal hypoperfusion (as for prerenal failure) or nephrotoxins (contrast, antibiotics, rhabdomyolysis), and most often by their combination ( Dinour and Brezis 1998). Acute intrinsic renal failure is synonymous with vasomotor nephropathy and acute tubular necrosis. Although acute intrinsic renal failure and the prerenal state represent two extremes of renal hypoperfusion,...

Conservative management

Much controversy surrounds whether, when, and why patients with severe acute pancreatitis should be subjected to surgery. Whatever the stage of the attack, two extremes of therapeutic strategy have been advocated, although neither has yet been substantiated by a controlled trial. The first strategy is early surgical removal of necrotic material (necrosectomy). Reported indications for surgery during either the early or the late phase of the attack are based on clinical, morphological, and or...

Approaches to the treatment of fever

Perhaps the most important aspect of pyrexia in the critical care setting is its 'indicator' function to alert the clinician to an underlying problem or new complication. Therefore fever should always be seen as a warning sign rather than a problem to be solved. However, fever is such a common phenomenon that it may not always have sinister significance, and a single elevated temperature reading should not be overinvestigated. Clearly, the strategy of choice in managing fever is to treat the...

Assessment of abdominal injury

Traumatic abdominal injuries are classified as penetrating or blunt injuries. Penetrating injuries are caused when an object, such as a bullet, crushes and tears the tissues it traverses. The energy transfer from the penetrating object to the tissues determines the degree of injury, and the wounding track determines the pattern of injury. In penetrating wounds to the upper abdomen the attending physician must be aware that abdominal injury can occur between the fifth intercostal space and the...

Cardiovascular disease

Vascular disease affecting coronary, cerebral, and peripheral circulations accounts for more than 50 per cent of overall morbidity and mortality in endstage renal failure. Hypertension, due to sodium retention, hyper-reninemia, and other factors, occurs early in renal failure and leads to the development of left ventricular hypertrophy. Hypertension (pressure overload), anemia, volume overload (including overdevelopment of arteriovenous fistula), and hyperparathyroidism have all been implicated...

Investigations

A careful sequence of investigations is mandatory in patients with jaundice ( Fig 1). Interpretation of patterns of liver blood test abnormality is problematic as such tests carry low sensitivity and specificity. Nevertheless, they are of use in certain specific diagnoses. Fig. 1 Investigations of jaundice in the critically ill patient TPN, total parenteral nutrition. A diagnostic strategy to exclude hemolysis is considered elsewhere but, in any patient with jaundice, the conjugated and...

Inodilators

Dobutamine is a synthetic derivative of dopamine and has been widely used for the past decade. It is a very potent b 1- and b2-agonist which provides direct inotropic action coupled with systemic vasodilation and afterload reduction. However, it is devoid of dopaminergic activity. In hypovolemic patients dobutamine may induce brisk hypotension and tachycardia, and tachyarrhythmias occur in the high-dose range. Dobutamine is generally used in the dose range from 5 to 20 g kg min. Dobutamine is...

Inspiratory and expiratory valves

Most modern mechanical ventilators have program-controlled gas delivery systems with either one inspiratory valve or a pair of inspiratory valves. These valves are almost always operated by an electromagnetic motor (Fig 2). Ventilators with one electromagnetic valve are supplied with gas from a reservoir which contains compressed gas at a specified oxygen concentration. Ventilators with a pair of inspiratory valves proportion compressed air and compressed oxygen independently to produce a...

Other measures for managing severe pneumonia

In some cases of severe pneumonia, the severe hypoxemia can only be adequately managed with oxygen administration and mechanical ventilation. Several therapeutic strategies, some of which are still under clinical investigation, have been suggested. 1. The administration of anti-inflammatory drugs such as aspirin or indomethacin may reverse the partial ablation of hypoxic pulmonary vasoconstriction that occurs in some cases of bacterial pneumonia owing to the local release of vasodilator...

Hemodynamic effects of changes in intrathoracic pressure

The heart within the thorax is a pressure chamber within a pressure chamber. Therefore changes in intrathoracic pressure will affect the pressure gradients for both systemic venous return to the right ventricle and systemic outflow from the left ventricle, independent of the heart itself ( BudaeLaL 1979 Pinsky,.et a 1985). Increases in intrathoracic pressure, by both increasing right atrial pressure and decreasing transmural left ventricular systolic pressure, will reduce these pressure...

Mechanical obstruction

Mechanical obstruction is an uncommon cause of intestinal distension in ICU patients. However, it is important to exclude this diagnosis through careful consideration of the common causes of small and large bowel occlusion. FigureJ presents an algorithm for the investigation of intestinal distension with the focus on distinguishing obstruction from ileus. Fig. 1 Algorithm for the approach to ileus versus obstruction in the ICU patient SIRS, systemic inflammatory response syndrome TPN, total...

Colonization and penetration of the nasopharyngeal mucosa

Infection cannot occur until colonization of the host has taken place, usually in the upper respiratory tract. Pathogenic bacteria such as meningococci are usually transferred by droplet spread. Crowding facilitates transmission, and is considered to be an important factor in the high attack rates of meningococcal infection in military recruits. There is a suggestion that invasive meningococcal infection develops shortly after colonization of a new host. Most individuals are asymptomatic...

Renal failure

The main questions being asked of diagnostic imaging in the critically ill patient with impaired renal function are as follows. What size are the kidneys Can obstruction be detected or excluded with confidence The size of the kidneys and the depth of the parenchyma will give an indication of either acute, or acute on chronic, renal failure. Ultrasound will provide this information with simple accuracy. Since the apparatus is mobile, the examination can be performed in the intensive care unit...

Encephalopathy and encephalitis

The three main causes of encephalopathy and encephalitis in patients with advanced HIV disease and CD4 counts below 100 * 10 6 l are HIV encephalopathy, progressive multifocal leukoencephalopathy, and cytomegalovirus-related encephalitis. Less commonly, herpes simplex virus and varicella zoster virus infection may be implicated. Encephalopathy may also be metabolically induced by drugs or by liver or renal failure. Magnetic resonance imaging (MRI) of the brain will show cerebral atrophy and...

Interventions

Management of postoperative pulmonary dysfunction starts before surgery. Risk factors for pulmonary complications are identified. These include the anatomical site of surgery, general illness or debility, the presence of chronic obstructive pulmonary disease (COPD), obesity (over 120 kg), cigarette smoking, and hypercapnia. Lung expansion techniques reduce pulmonary complications. Ideally, these are started prior to surgery and then continued through the postoperative period. The goal is to...

Mechanisms underlying immune dysfunction in critical illness

No single mechanism can explain the many (often subtle) changes seen in the immune function of critically ill patients. A number of general factors need to be considered, including the patient's nutritional state, failure of other organs, and the influence of drugs. In addition, the inflammatory response itself, and particularly the balance of pro- and anti-inflammatory responses, is an important determinant of immune function ( Bone 1996). Malnutrition is the most common cause of secondary...

Ballisticsthe science Bullets

The science of ballistics is the study of the physical and flight characteristics of bullets. Internal ballistics refers to those characteristics immediately following the firing of the bullet while it remains within the gunbarrel. Once the projectile exits the weapon, a new set of variables are encountered (e.g. wind drag) and impart yet another array of properties upon the bullet. How the bullet reacts to these variables is known as external ballistics. The injury patterns caused by bullets...

Topical antimicrobial agents

Burn injury not only produces thermal necrosis of skin, but also causes microvascular thrombosis, leaving the burn avascular and inaccessible to systemic antimicrobials. Topical antimicrobials are designed for direct application to the wound, with the goal of slowing colonization by bacteria and delaying invasive infection. No topical agent is capable of sterilizing the wound. The ideal topical agent should have activity against organisms likely to be encountered on the wound, should not...

Pharmacology of eaminocaproic acid and tranexamic acid

Tranexamic acid has a six- to tenfold higher molar potency compared with e-aminocaproic acid and is generally preferred for clinical usage, although routes of administration, effectiveness, limitations, and side-effects of the two compounds are similar. Tranexamic acid is available as 500-mg tablets (Cyklokapron, Pharmacia, United Kingdom), a syrup, or a colorless solution (5 ml contains 500 mg tranexamic acid) for intravenous infusion. Tranexamic acid is rapidly absorbed from the...

Closedcircuit measurement of VO2

Closed-circuit spirometry excludes the patient from the outside air. The volume-loss type uses a volumetric reservoir of O 2. The exhaled CO2 is absorbed from the system with soda lime so that the loss of volume over time is a measure of oxygen consumption. The volume-replenishment variant uses a similar system which maintains a constant volume in an oxygen reservoir by adding measured increments of oxygen to the system. As the system is similarly scrubbed of CO 2 and water vapor, the volume of...

Gas exchange consequences

Distribution of ventilation is uneven due to different degrees of bronchial obstruction. Impairment of circulation may occur in overdistended areas. Some alveoli are poorly ventilated and normally perfused (low ventilation-perfusion ratio) and lead to hypoxemia. In completely obstructed areas, normal perfusion would constitute a true shunt. However, a small collateral ventilation of these alveoli accounts for the absence of true shunt. Other alveoli are overinflated, compress capillaries, and...

Spleen

Although the spleen is protected by the left lower ribs and is held in place by peritoneal ligamentous attachments, it is the most common solid organ injured in blunt trama. Its has a spongy structure, with little collagenous tissue, and the capsule is rather thin. Thus the spleen is easily injured, leading to considerable hemorrhage in a short time. The capsule may remain intact while the parenchyma is injured, although this occurs in only 2 per cent of cases. This leads to a subcapsular...

Clinical uses of SjO2 monitoring

Continuous monitoring of jugular venous oximetry has been performed in intensive care, the operating room, and the neuroradiology suite to monitor patients with brain trauma, intracranial aneurysms, and arteriovenous malformations. Episodes of jugular venous desaturation to below 50 per cent have been reported in neurosurgical patients in association with hyperventilation, vasospasm, and compromised cerebral perfusion pressure during intensive care ( Chanefa 1992)- In a study of 102 patients...

Factors affecting respiratory rate Acceptable Paco2

Many clinicians aim for a normal CO2 tension (4.3-6.5 kPa (32-49 mmHg)) in the arterial blood. A reduction in respiratory rate at constant tidal volume, physiological dead-space, and CO2 production leads to a rise in Paco2. If the CO2 tension is too low, this helps to restore it to normal. A further reduction in respiratory rate at this point leads to hypercapnia, which may be acceptable if maintaining eucapnia would result in a high possibility of ventilator-induced lung injury. This approach...

Treat anxiety pain and inadequate coping skills

Anxiety is a common reaction to physical or psychological trauma and to treatment in intensive care units (ICUs). It can be seen as a transient reaction in a previously healthy individual or as a manifestation of a pre-existing anxiety disorder. The treatment team should make every effort to put the patient at ease to avoid potentially harmful reactions (e.g. pulling out intravenous lines, refusing treatment, and leaving against medical advice). Direct discussion of the patient's medical...

Respiratory muscles

The respiratory muscles are responsible for maintaining ventilation despite factors affecting pulmonary mechanics. As a result, if the muscular reserve can afford increasing loads, patients will maintain ventilation and avoid respiratory insufficiency. Nevertheless, COPD patients are at a disadvantage in coping with extra loads for the following reasons. First, chronic hyperinflation forces the inspiratory muscles to work in a less efficient position of their length-tension relationship....

Specific infections

Immediate treatment of meningitis is important in reducing mortality and is of greatest benefit when a petechial or purpuric rash, suggestive of meningococcal disease, is present. Penicillin G will often have been administered intramuscularly before the patient is admitted. Use of penicillin should override concerns of penicillin allergy unless there is a proven history of immediate-type hypersensitivity, in which case chloramphenicol should be given intravenously. Otherwise, empirical...

Severe infectious diarrhea

It is estimated that in some countries between a quarter and a half of childhood mortality is related to diarrheal disease. The risk to adults from associated dehydration, electrolyte imbalance, and weight loss is less, but nevertheless can be life threatening. Intercurrent infection with pneumonia or septicemia is common. Opportunistic infections in patients with AIDS are an increasing cause of severe diarrhea but rarely require intensive care. Common causes of food poisoning in developed...

Flow in blood vessels

Fluid does not flow as one uniform mass through a tube, and neither does blood flowing through the circulation. Blood flow varies according to the size of the vessel. In the arteries, arterioles, venules, and veins flow is laminar. Flow through the capillaries is single file. In the ventricles there is turbulent flow which allows mixing of saturated and unsaturated blood. Laminar flow occurs in cylindrical tubes. The fluid behaves as if it were a set of concentric shells or laminas moving at...

Prevention

The main aim of treatment is prevention. This requires good anesthetic practice for those patients undergoing general anesthetic and attention to detail for patients in the intensive care unit (ICU). Patients at risk must be identified, including emergency cases, pregnant women, and diabetics. An experienced anesthetist is required for these cases, and regional anesthesia should be considered. For safe intubation patients need to be fasted thus in emergencies rapid-sequence induction with...

Causes of hypernatremia

The many important causes of hypernatremia (Fig 1) include nasogastric hyperalimentation, diabetic coma, acute renal failure, improper mixture of dialysis fluid, dehydration secondary to either fever or elevated ambient temperature, and diabetes insipidus ( S,n.y.d,e.LeLal 1987 E l,e.v ky,et,a 1996). In the elderly, hypernatremia is often associated with infirmity and inability to obtain water, leading to gradual desiccation ( SD,yder,et,a 1987). Diabetes insipidus is associated with...

Fluid requirements

Fluid loss is almost inevitable in diabetic emergencies. The average loss for diabetic ketoacidosis is between 5 and 10 liters, and it is even higher for hyperosmolar non-ketotic coma. The loss is due to an osmotic diuresis caused by glycosuria. The resulting urine is isotonic with plasma, and therefore urine osmolality is not a guide to the state of dehydration. The urinary fluid losses come from all body fluid compartments in relatively equal proportions, resulting in generalized dehydration....

Hemodynamic effects of changes in lung volume

Lung hyperinflation can occur during weaning from mechanical ventilation if expiratory time is inadequate. This scenario is common in patients with chronic obstructive pulmonary disease and acute bronchospasm. To the extent that respiratory rate increases during weaning trials, inadequate time of exhalation may occur. Acute hyperinflation may occur in patients with chronic obstructive pulmonary disease because of airway collapse during expiration. Hyperinflation can occur at any time in the...

Mechanisms of airway colonization and infection

The understanding of the pathogenesis of nosocomial pneumonia is absolutely necessary for the rational comprehension of risk factors involved with this intrahospital infection. The pathogenic scheme recently recommended by the Centers for Disease Control ( T.ab. iD .L. 1994) is shown in Fig 1. 'Abnormal' colonization of the oropharynx and the gastric reservoir and the subsequent aspiration of their contents to lower airways in patients whose mechanical, cellular, and humoral defenses are...

Cardiovascular evaluation

Pulmonary hypertension is the hallmark of pulmonary microvascular occlusion. Hence pulmonary artery pressure (PAP) provides a rough measure of disease severity. It is not ideal as it will not distinguish between micro- and macrovascular occlusion. Furthermore, PAP does not rise unless more than 50 per cent of pulmonary vessels are occluded and hence may fail to detect significant microvascular occlusion. In addition, it is affected passively by intrathoracic pressure, pulmonary blood flow, and...

Thrombocytopenia

Thrombocytopenia is secondary to increased consumption which is likely to occur by adherence to collagen exposed on damaged endothelium. Martin et al. (1990) suggested three categories based on the platelet count class 1 when the platelet count is below 50 10 9 ml, class 2 when it is between 50 and 100*109 ml, and class 3 when it is between 100 and 150*109 ml. Class 1 patients had a higher mean value of lactate dehydrogenase, serum-glutamic oxaloacetic transaminase, serum glutamate-pyruvate...

Intracranial hypertension and cerebral edema

How Correct Intracranial Pressure

Increases in intracranial pressure, as occur in the later stages of ALF, could be the result of increases in volume of any of the three main components within the skull, namely brain tissue, cerebrospinal fluid, and the cerebral vessels. The ventricular system is usually collapsed at CT scanning, and cerebral edema is reported to develop in up to 80 per cent of ALF patients progressing to grade IV encephalopathy. The development of cerebral edema which underlies the rise in intracranial...