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...

Differential diagnosis

Multisystem anaphylaxis with urticaria, asthma, edema, and cardiovascular collapse leads to an obvious diagnosis. However, if symptoms are restricted to a single system such as angio-edema or cardiovascular collapse, the diagnosis may be difficult or not considered. Cases have been described where anaphylaxis was suspected only after the fifth episode of cardiovascular collapse. Anaphylaxis may only be considered as a cause of cardiovascular collapse when removal of drapes or clothing has...

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

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...

Vitamin D calcium and phosphorus homeostasis

Vitamin D is converted to its active form 1,25-dihydroxyvitamin D by hydroxylation in the kidney, stimulating bone, intestine, and kidney to raise calcium and phosphorus levels. Hypophosphatemia, elevated PTH output, and low 1,25-dihydroxyvitamin D levels increase vitamin D production, while the opposite effects decrease its synthesis. Progressive loss of renal tissue impairs the kidney's ability to generate activated vitamin D. The kidney plays a major role in calcium homeostasis, housing the...

Tricyclic and tetracyclic antidepressants

Maprotiline, a tetracylic compound, and the large group of tricylic antidepressants ( Table, 1) effectively treat the neurovegetative signs of depression. Potential sites of action are at the level of receptors (desensitization of presynaptic a 2-receptors, subsensitivity of b-adrenergic receptors), reuptake transporters (block of monoamine reuptake), and intracellular second-messenger systems. Table 1 Treatment indices and side-effect profiles of common antidepressants The cyclic compounds do...

Physiology of potassium balance

Plasma potassium levels are determined by the balance between absorption and excretion and by internal shifts between the extracellular fluid and cells. Normal daily intake is 50 to 150 mmol, of which 5 to 15 mmol appears in the stools and sweat. Potassium excesses are usually excreted rapidly however, if this is impossible, plasma potassium rises sharply, with each increase of 1 mmol l above 4 mmol l corresponding to an increase in total body potassium of 50 to 100 mmol. Plasma potassium...

Approach to normal anion gap metabolic acidosis

The approach to metabolic acidosis with a normal anion gap is shown in Fig 1. Note that it is first important to ensure that the anion gap is indeed normal and not spurious (i.e. not greater than normal when corrected for albumin). Note also that urinary electrolyte determinations in the intensive care unit (ICU) are often confounded by concomitant administration of medications, particularly diuretics. Fig. 1 Approach to normal anion gap metabolic acidosis. The mnemonic for normal anion gap...

Exclude potentially lifethreatening causes

The mnemonic WWHHHIMP can guide the clinician during the rapid assessment of serious and potentially life-threatening causes of delirium ( Fig 1). Wernicke's encephalopathy is strongly suggested by the triad of confusion, ataxia, and ophthalmoplegia. Additional support for this diagnosis can be derived from a history of alcohol dependence, by abnormal liver function tests, and by an elevated red blood cell mean corpuscular volume. Withdrawal states occur after discontinuation of illicit or...

Additional bronchodilators

Halothane, enflurane, and isoflurane can acutely reduce peak airway pressure and PaCO2 in ventilated patients and can supplement continued b-agonists and systemic corticosteroids. Halothane (0.5-2.0 per cent) is effective in most patients, but has a low therapeutic ratio in the acidotic hypovolemic patient. In addition, use of halothane for more than 24 h may be associated with bromide toxicity. Isoflurane in similar concentrations is safer than and probably as effective as halothane. Adequate...

Type II decompression sickness

Chest pain, cough, dyspnea, tachypnea, cyanosis, and cardiovascular collapse, collectively referred to as 'the chokes', are caused by significant pulmonary gas embolism. Intravascular bubbles may produce the adult respiratory distress syndrome by the activation of humoral and cellular blood elements ( James,.1993). If the lung filter is overwhelmed or acute pulmonary hypertension reopens a functionally closed foramen ovale, microbubbles may pass into the systemic circulation, leading to...

Postpartum HELLP

Postpartum HELLP syndrome occurs in up to 30 per cent of patients in the vast majority it appears within the first 48 h postpartum, although it can develop after a week (Sibai. etai 1993). Since delivery has been effected, treatment of maternal complications is the major priority (T.able.3). Pulmonary edema and congestive heart failure are more frequent in postpartum-onset HELLP (Sibai etaL 1993), indicating the need for close monitoring of fluid balance after delivery and careful hypertension...

Mode of transport

Hospital design should allow intramural transfer between departments, preferably with orderlies to move beds or trolleys, and nursing and medical staff to maintain care in transit. Manual lifts onto trolleys have the potential of injuring patients and staff, and aids such as sliding devices are advocated. Some protocols recommend using up to five people for major shifts if no physical aids are available. Supporting equipment should be attached to the bed, as trailing devices are hazardous...

Intrinsic control of Qha autoregulation and the hepatic arterial buffer response

Qha can also be modified by two specific intrinsic controls autoregulation of Qha and the hepatic arterial buffer response. The autoregulation of a given vascular bed is defined by its ability to modify its vasoactive status in response to changes in perfusion pressure so as to maintain blood flow relatively constant within given pressure limits. Beyond these limits, flow becomes linearly related to pressure. Such pressure-flow autoregulation has been described in the hepatic arterial bed,...

Eicosanoids lipid metabolites

Specific fatty acids derived from dietary lipids are incorporated into the structure of the phospholipid cell membranes. These phospholipids represent a reservoir of potential metabolic mediators, the nature of which depends on the fatty acids ingested (or infused). Under enzymatic action, the phospholipid membranes release fatty acid molecules which are converted to a number of eicosanoids. The intake of omega-6 fatty acids causes the release of arachidonic acid which produces thromboxane A2...

Control of metabolic supply and demand

As the supply of metabolic substances to the brain is reduced during ischemia, it should follow that drugs which decrease metabolic demand might favorably influence the supply-demand relationship. Therefore they might be expected to produce prolonged tolerance to, and improved outcome from, a temporary ischemic insult. Barbiturates have been used in the protection of the brain since 1937, when Horsley first described their effect on cerebrospinal fluid pressure. The exact way in which...

Cardiovascular nuclear imaging

Scintigraphic imaging procedures record the spatial or temporal distribution of radioactive isotopes within the body using a gamma camera for the detection of radiation. Image acquisition can be performed in the planar or tomographic mode. In planar imaging, projection images of the tracer distribution are recorded from selected angles to image the heart from different views. Planar imaging is a simple technique that can be performed with a mobile gamma camera and thus is available at the...

Control of ventilation

Breathing requires the integrity of both the central and peripheral nervous systems at multiple levels ( Bergerefa 1977). Peripheral receptors located in aortic and carotid bodies are activated by decreased arterial oxygen, pH, or blood pressure, and by increased carbon dioxide tension. This leads to increased central ventilatory drive. In addition, mechanical receptors along the respiratory tract can facilitate or inhibit breathing, or affect the breathing cycle in a reflex fashion (e.g....

Do2 [Hb x Sao2 x 134 00031 x Pao2 x CO

It is necessary to secure the airway in patients with neurological compromise. Positive-pressure mechanical ventilation is indicated in the presence of pulmonary edema, acute lung injury or acute respiratory distress syndrome, severe bronchospasm, or therapeutic hyperventilation. Ventilatory support is titrated to minimize the work of breathing and ensure adequate arterial oxygen saturation ( SaO2) and PaCO2. In spontaneously breathing patients continuous positive airway pressure with...

Fluid and intracranial pressure management

The documented association of increased ICP with poor outcome from herpes simplex encephalitis may simply indicate that elevated ICP is a marker of disease severity rather than a specific mechanism of secondary injury requiring active management. Nevertheless, simple measures to reduce or prevent further elevations of ICP and prevent complications (brain ischemia) are central to supportive management. Recommended practices include the following. 1. Elevate the patient's head by 20 to 30 to...

Comparisons of different forms of mechanical ventilation

In patients with a markedly increased work of breathing, volume overload, or impaired left ventricular function, the application of mechanical ventilation can be lifesaving because of its ability to unload a weakened cardiovascular system while reducing both global and myocardial oxygen consumption. These effects will be independent of any beneficial effects that mechanical ventilation may have on gas exchange. In patients with decreased pulmonary elastic recoil, increased pulmonary vascular...

Assessment and correction of hypercapnia

Knowledge of the previous respiratory status is of paramount importance in determining the goal of respiratory support. A reasonable goal in a previous healthy subject could be normal blood gases ( PaCO2 40 mmHg (5.33 kPa), PaO2 > 80 mmHg (10.66 kPa)). In a subject with previous chronic respiratory impairment, the goal should be the blood gas values present before the superimposed acute derangement (e.g. PaO2 60 mmHg (8 kPa), PaCO2 50 mmHg (6.66 kPa)). An accurate history is essential for...

Diarrhea as a complication of treatment

Many different classes of drugs have diarrhea as a side-effect. The list in Table. is not exhaustive. Cumulative effects of laxatives given during hospital admission and antibiotics are amongst the most common drug-induced causes of diarrhea. When drugs are administered as elixirs, the amount of sorbitol given with an adult dose is often enough for it to act as an osmotic purgative (Edes etal 1990). Table 2 Drugs associated with diarrhea Table 2 Drugs associated with diarrhea Diarrhea occurring...

Pharmacological treatment

Neuroleptics and benzodiazepines are the primary drugs used to manage the agitated and or confused patient. If the patient's agitation cannot be controlled by these two classes of medications, narcotics and paralyzing agents can be used as a last resort (Table 1). Table 1 Drugs used to treat delirium and agitation Haloperidol, a high-potency neuroleptic of the butyrophenone class that blocks postsynaptic D 2 dopamine receptors, has an extensive record of safety and efficacy in critically ill...

Hemofiltration andor hemodialysis

This is usually unnecessary in patients with intact renal function. Patients with predictably transient hyperkalemia can usually be maintained at acceptable potassium levels by using a combination of glucose-insulin, sodium bicarbonate, and forced diuresis, possibly supplemented with b 2 agonists. In patients where these methods fail and in those with established acute or acute-on-chronic renal failure, hyperkalemia usually reflects a generalized metabolic disturbance and is an indication to...

Dialysate composition Electrolytes

The sodium content of the dialysate is an important determinant of intradialytic symptoms. Diffusive removal of small solutes entails a reduction of extracellular osmolality, leading to the loss of extracellular fluid into the intracellular compartment. These fluid shifts are reduced by maintaining dialysate sodium at or above the serum concentration. Dialysate sodium concentrations below 140 mmol l should be avoided in hemodynamically unstable patients. Rapid and efficient potassium removal...

Inspiratory valves

Most mechanical ventilators do not incorporate a mechanism dedicated to providing gas for spontaneous breathing, i.e. a 'demand valve'. Typically, a single gas delivery system is used for all modes of ventilatory support. The difference between the various modes is the algorithmic control of the inspiratory valve(s). Therefore performance of mechanical ventilators during spontaneous breathing is determined by factors similar to those discussed for patient-triggered pressure-controlled...

CPAP and intracranial pressure regulation

Some concern may arise when CPAP is delivered to patients with increased intracranial pressure. Positive intrathoracic pressure may indeed decrease venous return and act as a resistive component to venous return from the head, thus increasing intracranial venous pressure and eventually parenchymal intracranial pressure. Decreased systemic venous return may also decrease cardiac output and blood pressure which will decrease oxygen delivery and perfusion to the already jeopardized cerebral...

Apparent stress polycythemia

Apparent ('stress') polycythemia (P.e.ais.on, 1991.) is poorly understood, but the contracted plasma volume may be improved by occasional venesection if the hematocrit exceeds 0.55. Although not proven, it is thought that a change of lifestyle for patients with a contracted plasma volume may be beneficial. Therefore such patients should be firmly encouraged to stop both smoking and excessive alcohol intake. Their doctors should avoid prescribing them diuretics, using vasodilators and...

Complications

Acute traumatic rhabdomyolysis can cause three types of complication acute renal failure, the compartment syndrome, and calcium and phosphate derangement. The liberation of large amounts of myoglobin and other muscle cell contents in the blood leads to hyperkalemia, hyperphosphatemia, hypocalcemia, and metabolic acidosis (Table. 2). These abnormalities begin when serum urea and creatinine concentrations are still within normal limits. Hyperkalemia may cause life-threatening ventricular...

Factors affecting tidal volume

Maintenance of eucapnia is sometimes only possible with strategies that increase the risk of ventilator-induced lung injury, including the use of a tidal volume that causes alveolar overdistension. In these situations (e.g. acute lung injury), the risk can be reduced by decreasing tidal volume and therefore peak alveolar pressure. If the respiratory rate, physiological dead-space, and CO 2 production remain constant, Paco2 will rise. This may be appropriate if there is no significant...

Indications for chest physiotherapy techniques

Intermittant lateral turning is indicated for sedated patients and those presenting a neuromuscular disease, or hypoxemia in certain positions, when patients present risk factors for atelectasis or proven sputum retention, or when patients are intubated or tracheostomized. Postural drainage is indicated to eliminate secretions in patients who have excessive production, ineffective cough, cystic fibrosis, or bronchiectasis, in patients who are intubated, and as treatment for atelectasis and...

Key messages

The Glasgow Coma Scale (GCS) is the best available measure of the impact of disease or injury on neurological function. The GCS score is such an important determinant of patient outcome that it is used in most contemporary severity scoring systems. When combined with abnormal brainstem responses, the GCS score identifies individuals at high risk of death or a vegetative state. The Glasgow Coma Scale (GCS) was described in 1974 as a practical method for assessing coma. Impaired consciousness...

Approach to assessment of development of fever in the ICU patient

In assessing a patient with fever the following questions must be considered. 3. Did it commence abruptly at a particular clinical event 5. Is it constant or intermittent The chronology of a febrile episode is particularly important. If the patient had been in hospital for some time before admission to the ICU, temperature charts from that time period or any recent previous admissions should be reviewed and collated with the present charts. The pattern of fever may be helpful traditionally, a...

Methods of measuring energy expenditure

Energy expended, in the form of heat produced, could be measured by placing the entire patient in an insulated chamber and measuring temperature change. This process (direct calorimetry) is obviously impractical for critical care. Indirect calorimetry, developed and validated using direct calorimetry, is the calculation of energy utilization based on measurement of O2 consumption (Vo2). Vo2 can be measured directly or calculated using the Fick equation. Once Vo2 has been measured, the metabolic...

Diagnosis

The diagnosis of rhabdomyolysis made by the measurement of serum creatine phosphokinase and serum and urinary myoglobin is usually systematic. Serum creatine phosphokinase should be at least six times the upper normal value (100 IU l) for diagnosis. Serum creatine phosphokinase begins to rise 2 to 12 h after the injury and reaches its peak value, ranging from several hundred IU per liter in mild muscle injury to over 200 000 IU l in the full-blown crush syndrome, 1 to 3 days after injury the...

When should acute hemolysis be suspected

Acute anemia and its pathophysiological effects 3. Acute intravascular hemolysis 4. Activation of proteolytic systems and the consequences thereof complement and kinin systems shock, anaphylactic anaphyloid reactions cytokine activation and release cytokine storm, systemic inflammatory response syndrome 5. Dark urine hemoglobinuria, bilirubinuria 6. Laboratory presentation hemoglobinemia, hyperbilirubinemia, high lactate dehydrogenase 8. Cold agglutinins microvascular occlusion The primary...

Continuous positive airways pressure CPAP

The application of positive pressure in a closed breathing system through spontaneous breath cycles is known as CPAP it increases mean airway pressure and may decrease the work of breathing by moving tidal ventilation to a more compliant part of the volume-pressure curve ( Fig 1). CPAP acts as a pneumatic splint, promoting alveolar re-expansion in areas of atelectasis, and may prevent the need for endotracheal intubation and conventional ventilation in certain patients. The hemodynamic effects...

Effects of starvation

The initial response to starvation is glycogenolysis to maintain blood glucose concentration. However, glycogen stores become exhausted within 2 to 3 days, and an alternative source of glucose is required to fuel tissues such as the brain which generates energy exclusively from glucose. Structural body protein is broken down to provide amino acids as a substrate for gluconeogenesis. This protein breakdown is halted by an adaptive process by which the brain uses ketones as its metabolic fuel. In...

Tracheoesophageal fistula

Esophagorespiratory fistulas most commonly occur between the trachea and the esophagus and are referred to as tracheo-esophageal fistulas. They may occur secondary to malignancy, radiation therapy, chemotherapy, or photodynamic therapy. Malignant tracheo-esophageal fistula is a devastating and often terminal complication occurring in a variety of malignancies. In the largest series of tracheo-esophageal fistulas, 207 malignant cases were reported ( Bu.dLe.t a.l 1991). The most common tumors...

Increased anion gap metabolic acidosis

Correction of underlying pathophysiology is perhaps most critical in lactic acidosis ( Arieff.1991 .i m m e.tt.1 , L 1992 Stacpooje.1993). In the critically ill, pathogenesis is often related to hypoxic and non-hypoxic mechanisms. Oxygen delivery and tissue perfusion must be improved with blood and or volume infusion, inotropes, and pressors, and oxygen consumption must be limited. Therapy should be instituted to correct non-hypoxic causes, including treatment of sepsis, administration of...

Clinical manifestations of hyponatremia

The signs and symptoms of hyponatremia are directly related to the development of cerebral edema, increased intracranial pressure, and cerebral hypoxia. The early symptoms of hyponatremia (from any cause) may include apathy, weakness, muscular cramps, nausea, vomiting, and headache. More advanced clinical manifestations include impaired response to stimuli, myoclonus, urinary incontinence, and hallucinations. More severe clinical manifestations of hyponatremia may include decorticate posturing,...

Contracted plasma volume syndromes apparent polycythemia stress polycythemia relative polycythemia or pseudopolycythemia

This is seen particularly in patients with hypertension and a lifestyle involving excessive smoking and drinking ( Pearson 1 9 9.1 ). Some of these patients are on diuretic therapy for hypertension, which further contracts plasma volume. Again, hematological diagnosis by estimation of blood volume is needed for certainty and rational management. High-dose diuretic therapy, for example furosemide (frusemide) given in a dose of 400 mg or more daily, will contract the plasma volume when the...

Acute necrotizing myopathy of intensive care

Rarer, but better defined, is 'acute necrotizing myopathy of intensive care' ( Zochodne et ai 1994). It may be precipitated by a wide variety of infective, chemical, and other insults, basically involving the differential diagnosis of acute myoglobinuria. It would be expected to occur with increased frequency in ICUs, in which there is a high incidence of trauma, infection, and use of various medications. Thus reported 11 cases, in which there was severe weakness with high levels of creatine...

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Ongoing respiratory failure, fever, sepsis, multiple organ dysfunction, hemodynamic instability, and biochemical derangements contribute to inadequate oxygenation and gas exchange. Obviously, if weaning is initiated before the precipitating illness has resolved significantly, it is more likely to fail. Decreased level of consciousness secondary to the primary illness is common and will also jeopardize the success of weaning if it is started prematurely. Unfortunately, there are no clinical or...

Secondary or compensatory polycythemia

This involves red cell proliferation, with measurable increases in red cell volume, and is almost always secondary to arterial hypoxemia. Cyanotic heart disease, chronic bronchitis, emphysema, and other pulmonary causes of arterial hypoxemia are particularly prominent. In these disorders the polycythemia represents a beneficial natural reaction to the hypoxemia leading to a hypervolemic erythrocytosis. This, in association with hematocrit values of 0.55 to 0.65 and a red cell volume of...

Peritraumatic and perioperative concepts of neuroprotection

Studies in laboratory animals and humans have shown that hyperglycemia is associated with worsened outcome following stroke or neurotrauma. The mechanisms by which normoglycemia may protect neuronal tissue include decreases in intracellular lactic acidosis and in membrane permeability with reduced cellular edema. Therefore plasma glucose concentration should be monitored closely and adjusted within the range of 100 to 150 g dl (5.5-8.5 mmol l). The term 'lazeroids' is frequently used to...

Pathogenesis of alveolar rupture

The various forms of pulmonary barotrauma (interstitial emphysema, pneumomediastinum, pneumoperitoneum, subcutaneous emphysema, lung cyst formation, and pneumothorax) are prominent among the iatrogenic causes of critical illness. Patients with acute respiratory distress syndrome appear to be at highest risk. Although direct rupture of the visceral pleura occasionally occurs, the barotrauma that complicates mechanical ventilation most frequently develops more circuitously. Alveolar rupture is...

Relationship between minute ventilation and PaCO

In normal exercising humans, the minute ventilation increases in proportion to both the metabolic rate and cardiac output. The alveolar ventilation increases because lung perfusion increases in proportion to the ventilation while the anatomical dead-space either decreases (due to larger tidal volumes) or remains unchanged. Thus both CO 2 production and alveolar ventilation increase during exercise, so that PaCO2 either remains the same or decreases slightly. In contrast, a normal subject on a...

Complications of falciparum malaria

Technically, cerebral malaria is unrousable coma without fits in the preceding 30 min with no cause except for malaria. Hypoglycemia should always be excluded. Mortality from cerebral malaria can be up to 30 per cent even with ideal treatment. Despite this, patients who survive seldom have significant neurological sequelae. Trials have shown that prophylactic intramuscular phenobarbital (phenobarbitone) improves outcome in cerebral malaria where this is not available it is likely that other...

Eliminate drug toxicity and treat drug withdrawal

The regular use of prescription drugs, the abuse of illicit drugs, and the withdrawal from either type of drug are all common causes of agitation and confusion. Narcotics and drugs with anticholinergic properties account for a large proportion of drug-induced confusional states. The first step in treating drug-induced delirium is to stop the offending drug and to find an alternative compound without similar adverse effects. If necessary, antidotes can be administered. 1. Naloxone hydrochloride...

Hypermetabolism and nutritional support

The hypermetabolic response to burn injury surpasses, in both magnitude and duration, that associated with any other disease process. It can be thought of as consisting of two distinct components. First is the increased heat loss from the destruction of the skin's barrier function. Homeostasis in the face of such heat loss demands increased heat production and hence hypermetabolism. This component of demand can be reduced by decreasing the heat loss with occlusive dressings or by raising the...