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There 110 Yearbook of Anesthesiology-6 is a good correlation between perioperative cardiovascular instability and catecholamine release from pheochromocytoma buy metoclopramide 10mg with visa gastritis recipes. An intake of 2–3 L of saline in alpha-blocked patients decreases the severity of orthostatic hypotension and post-excision hypotension discount 10 mg metoclopramide fast delivery gastritis diet oatmeal cookies. An echocardiogram is valuable in detecting ventricular dysfunction purchase metoclopramide 10mg on-line gastritis diet plans, evaluating improvement with therapy cheap metoclopramide 10 mg with visa gastritis pdf, diagnosing dilated cardiomyopathy and timing of surgery. Further, Witteles31 and Emerson32 have described outpatient preparation, which reduces the burden on hospitals. Improved morbidity figures started appearing from 1964 with Goldfein’s series,35 who used preoperative preparation, invasive monitoring, epidural analgesia and painstakingly recorded hemodynamic changes (Fig. With the advent of laparoscopic adrenalectomy for pheochromocytoma, most intraoperative morbidity, especially related to gland manipulation, has virtually been eliminated. Understanding catecholamine physiology, need of vasodilators, good analgesia and volume management are fundamental to good management of laparoscopy. Laparoscopic technique does not do away with invasive monitoring, alertness on the part of the anesthesiologist or titration of anesthetic depth and/or vasodilators. It imposes an extra burden of monitoring changes related to pneumoperitoneum, but the overall reduced morbidity is worth the effort. Thus, one can trace a link between dose and timing of alpha blockade, surgical expertise and good recovery. Laparoscopic approach to adrenalectomy was first reported by Gagner in 1992, in a series of 3 patients. Five years later, a series of 100 cases of laparoscopic adrenalectomy,37 which included 25 cases of pheochromocytoma, was published. This has been followed by numerous other series testifying to not only the safety but also the positive advantages of this technique over open adrenalectomy. Apart from minor advantages in the form of better cosmesis, less pain and early ambulation, significant advantages include decreased intraoperative hemodynamic fluctuations and blood loss. Humoral changes in the form of increased catecholamines, vasopressin and cortisol levels have also been reported. Earlier series on laparoscopic pheochromocytoma reported a relationship of hypertensive surges with initiation of pneumoretroperitoneum, and intra–abdominal pressures (Table 9. Successful management of laparoscopic excision of pheochromocytoma thus involves careful understanding of the possible effects of pneumoperitoneum on Pheochromocytoma: Current Concepts and Management of Laparoscopic Excision 113 Table 9. Initial work up, pharmacological testing and localization are as for open procedure. Anesthetic management begins with a thorough preoperative evaluation and optimization of blood pressure, volume status, glycemic control and alleviation of symptoms. Preoperative Explanation and Premedication It is imperative to visit the patient multiple times during pharmacological optimization for the following reasons: • Patient recognizes you as primary caregiver • Confidence and familiarity reduce anxiety • Ensure compliance • Enable assessment of effect of treatment • Appropriate modification There is no substitute for these repeated preoperative visits. Patient is explained about the need for, and the technique of invasive vascular cannulation prior to induction of anesthesia. All adult patients by this time are very compliant and comfortable with all explanations and it is the author’s personal experience of more than 110 cases (Figs 9. Premedication Oral benzodiazepines and H2 receptor antagonist are suitable premedicants. Short-acting selective a-1 adrenergic blockers should be administered in the morning to continue a blockade during the procedure. If the patient is on long- acting a-1 adrenergic blockers (phenoxybenzamine/doxazosin), they should be stopped 12–24 hours before. Intraoperative hypertensive crises occur during: • Stimuli like intubation and positioning • Pneumoperitoneum • Handling of the gland • Squeezing the gland against the diaphragm to control bleeding Establishing invasive arterial and central venous monitoring before induction helps prompt detection and rapid correction by infusion of vasodilators into the central circulation. The ‘minimally’ invasive nature of laparoscopic pheochromocytoma excision is minimal only with respect to the size of the incisions! Pheochromocytoma: Current Concepts and Management of Laparoscopic Excision 115 Invasive vascular access is, therefore, best obtained prior to induction. Propofol, fentanyl and vecuronium are very satisfactory agents for induction and provide good hemodynamic stability and intubating conditions. Intubation is performed expeditiously under adequate depth of inhalational anesthesia (isoflurane or sevoflurane). The supine route is preferred in cases of suspicion of malignancy or multiple tumors where the abdomen and contralateral adrenal can be examined in the same sitting. For lateral transperitoneal or retroperitoneal approaches, the patient is kept on the side and a roll is placed under the dependent costal margin (Fig. Hypercarbia, catecholamine release and hypertensive crises are directly related to the carboperitoneum pressures. The main advantages of the laparoscopic approach for pheochromocytoma are evident after the surgeon has mastered the learning curve. One of these is minimal blood loss owing to increased magnification and accurate hemostasis. From the anesthetic management point of view, the most significant advantage is the decreased amplitude of hypertensive surges during gland manipulation. As the tissue attaching the tumor to surrounding structures is dissected and devascularized, the patient is ‘dissected away’ from the tumor, with consequent minimal actual handling of the tumor. If the disturbance Pheochromocytoma: Current Concepts and Management of Laparoscopic Excision 117 is predominantly dysrhythmias/tachycardia, esmolol bolus (0. With progressive vascular disconnection, both the frequency and severity of hypertensive surges decrease. Generally, hypotension at the conclusion of surgery is minimal, easily controlled with small doses of noradrenaline, and can be tapered off within 6–8 hours. Pressor support is best provided with norepinephrine which mimics the preoperative condition, till the downregulated adrenoceptors regain their sensitivity. Smooth intraoperative course is directly dependent on the expertise of the surgeon. Small doses of hydrocortisone (25–50 mg) may be required for 2–3 days in cases of bilateral adrenalectomy. Single shot intrathecal morphine (100–300 g) has been extremely effective, in the author’s personal experience of more than 50 cases. Pheochromocytoma during Pregnancy Pregnancy may be complicated by pheochromocytoma. If the pregnancy is less than 24 weeks, after a 2-week preparation, laparoscopic excision has been successfully performed. Hypertensive crises may occur in response to preoperative anxiety, tracheal intubation, positioning and/or tumor manipulation with suboptimal preoperative preparation and inadequately titrated anesthetic depth. Further, pheochromocytoma may present as hypertensive crisis for the first time during unrelated surgery, endoscopic procedure or administration of beta blockade alone for hypertension. A high index of suspicion, treating severe hypertension with magnesium sulphate and/or calcium channel blockers and always keeping pheochromocytoma as a 118 Yearbook of Anesthesiology-6 Flow chart 9. Chromaffin tumors in other parts of the sympathetic chain are termed as ‘paragangliomas’, which may or may not be functional. However, in spite of smaller incisions, hemodynamic fluctuations are expected intraoperatively, so invasive monitoring and intensive care facilities should be available. A current review of the etiology, diagnosis, and treatment of pediatric pheochromocytoma and paraganglioma.
Am J Neuroradiol 165:1245–1250 Kornienko V order 10mg metoclopramide with mastercard gastritis diet , Pronin I generic metoclopramide 10mg with amex gastritis symptoms in spanish, Serkov S et al (2003) Neuroradiologic diag- nosis of the primary brain lymphomas purchase metoclopramide 10mg on-line gastritis meaning. J Med Visualis 1:6–15 (in Cuccia V et al (2003) Subependymal giant cell astrocytoma in chil- Russian) dren with tuberous sclerosis cheap metoclopramide 10mg otc gastritis diet . Child Nerv Syst 19:232–243 Korshunov A et al (2004) The histologic grade is a main prognostic Dolgushin M, Kornienko, Pronin I et al (2004) Complex diagnos- factor for patients with intracranial ependimomas treated in the tics of metastatic diseases of the brain. Dis Nerv Syst 16:86–92 Lacroix M et al (2001) A multivariate analysis of 416 patients with Farwell J, Dohrmann G et al. Petersburg (in Russian) Forbes G, Cohen A (1992) Primary cerebral lymphoma: an associa- Matthay K et al (2003) Central nervous system metastases neuro- tion with craniopharyngioma or cadaveric growth hormone ther- blastoma: radiologic, clinical, and biologic features of 23 patients. Cambridge University in Lhermitte-Duclos disease (dysplastic cerebellar gangliocyto- Press, Cambridge ma). Radiology 222:715–721 Selch M (1998) Gangliogliomas: experience with 3 patients and re- Lee M et al. Neuropathology 22:252–260 Shin J et al (2001) Choroid plexus papilloma in the posterior cra- Lev M et al. Radiat Med 22, 4, 275–282 and neuroimaging features and their diferential diagnosis. Neurosci 36:137–141 Child Nerv Syst 19:292–297 Nowak D et al (2002) Lhermitte-Duclos disease (dysplastic cerebel- Tarin S, Golby A (2007) Functional brain mapping and its applica- lar gangliocytoma): a malformation, hamartoma or neoplasm? Saunders, Philadelphia, pp 583–611 denko Jan-Mar;(1):6-11; discussion 11-12 (in russian) Osborn A (1994) Diagnostic neuroradiology. Epi- Yakovlev P, Wadsworth R (1946) Schizencephalies: a study of the demiologic considerations. Burdenko 3:9-13 (in russian) Pronin I, Konovalov A, Marjashev S (2002) Neuroradiologic features Zemskaya A (1985) Brain tumours of astrocytic line. J Med Visualis 1:6–15 (in Russian) ingrad (in Russian) Romodanov A (1965) Brain tumors in children. Mixed tumours and nontumoural masses Pineal region tumours are relatively rare, accounting for 0. Dermoid, epidermoid encountered in a higher percent of cases, roughly 3–8% (Bur- c. Vascular malformations (cavernoma) frequent site where supratentorial tumours occur in children (Ganti et al. Four main syndromes prevail among clinical features of tu- Although this region is small (as are the brain structures that mours of the pineal region: intracranial hypertension due to constitute it), the tumour histology in this region signifcantly compression of the Sylvian aqueduct, Parinaud’s syndrome varies—up to 17 forms of tumour have been described. Tumours predominantly located in the posterior portion of of the tumour relative to the third ventricle and adjacent tis- the third ventricle, with a diameter up to 2. Intermediate-size tumours (a combination of the frst and relationship with venous and other structures of the pineal the second variants), with a diameter up to 4 cm (Fig. Giant tumours totally or subtotally occupying the third years, it may be revealed in approximately 11% of cases. Tus, and the fourth ventricles, and invading the lateral ventri- calcifcation of the pineal gland in children is suggestive of cles, >7 cm in diameter (Fig. In addition, if there is displacement of calcifcation Such a subdivision allows planning treatment approaches in from the median axis and/or its location is a part of several patients with tumours of the pineal region—conservative, tumours, is helpful in making precise preoperative diferential surgical (including the approach and plan of operation), ra- diagnosis. Histologically, germ cell tumours taining tumour cells and large vesicular nuclei, encircled by are subdivided into several subtypes: germinoma, embryonal fbrous connective tissue with accumulations of lymphocytes carcinoma, endodermal sinus tumour, choriocarcinoma, tera- between fenestrae (Matsko 1998). Large tumours expand Tese tumours make up to a third of all tumours of the in the anterior direction into the third ventricle cavity, with pineal region. Tey are thought more frequently encountered infltration of thalami, and subtentorial growth is also noted. How- Usually their clinical manifestations are premature sexual de- ever, it is always encircled by the tumour tissue (Chang et al. Pineal gland petrifcates are make up 40% of all tumours of this region, but may be re- better detected on Т2- and Т2*-weighted images than on Т1- vealed in other parts of the brain (Sojima et al. Around the tumour on T2-weighted are suprasellar in 25–35% of cases, and in projection to basal images an area of increased signal is frequently seen, which ganglia in 10% of cases. It isbelieved these tumours are more refects perifocal oedema of brain tissue caused by tumour frequently encountered in boys than in girls, and their clinical invasion. Rarely, germinomas may have atypical structure manifestations are hydrocephalus, midbrain signs, and pre- with multiple cysts and haemorrhages (Fig. The peak of incidence in children hancement is usually prominent and allows ascertaining loca- is in the second decade of life (Fetell et al. The the axial projection (а) shows the tumour is weakly hyperintensive ventricular system is dilated, and the third ventricle is deformed. The to brain tissue, whereas on axial (b) and sagittal (c) projections T1- lamina tecti is pushed backwards Fig. T2-weighted image (а) in the axial projection the tumour is hyperintensive to brain tissue and hypointensive on the T1-weighted image (b). Small cysts hyperintensive on the T2-weighted image (а) and hypointen- sive on the Т1-weighted image (b) are seen in the depth of the tumour. Calcifcation of the pineal gland is located in the anterior inferior portions of the tumour (arrow) Pineal Region Tumours 493 Fig. On Т2-weighted (а) cifcation of the pineal gland is visualised in the depth of the tumour and T1-weighted images in axial (b) and sagittal (c) projections, there (hypointensive area). Metastasis is seen on the bottom of the third is a small tumour in the posterior portions of the third ventricle. Sagittal T1-weighted image (c) gives additional information about expansion of the tumour 494 Chapter 5 Fig. On Т2-weighted images, the tumour has multi- cystic structures resembling honeycombs Pineal Region Tumours 495 Fig. Prominent and homogenous contrast enhance- (а,b) and T1-weighted image (c) demonstrate a small tumour in the ment of the tumour is seen. Initial signs of obstructive hydrocepha- posterior portions of the third ventricle. The area of oedema/inva- lus are revealed (d–f) sion is hyperintensive on T2-weighted images and hypointensive on 496 Chapter 5 Fig. The solid part of the tumour intensively accumulates contrast medium, improving visualisation of expansion of the tumour and its internal structure. Germinomas frequently present as metastases along the subarachnoid spaces, and subependymally along the ventric- ular system and the spinal cord. As this type of tumours the subarachnoid space, nodes of atypical shape and struc- originates from three embryonic layers, they may contain hair, ture may form, which have no certain diferences, for example fat, bones, and teeth in diferent proportions. Afer 20 Gy, immature (malignant), which are represented by immature marked decrease in the tumour size may already be seen. Such a technique is called the biological biopsy of the Variability of tumour composition predetermines variabil- 9 Fig.
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Her mother had mildly elevated glycemia during her pregnancies but was not treated cheap 10 mg metoclopramide free shipping gastritis natural cures. It often is diagnosed before the age of 25 years and is estimated to cause up to 5% of diabetes diagnosed 1 before the age of 45 years buy 10mg metoclopramide with amex gastritis special diet. It is characterized by persistent endogenous insulin secretion and an absence of β-cell autoimmunity discount 10mg metoclopramide fast delivery diet gastritis adalah, obesity discount 10mg metoclopramide mastercard gastritis migraine, or insulin resistance. Glucokinase is a key regulatory enzyme in glucose metabolism and glucose-stimulated insulin secretion. This manifests as persistent, mild hyperglycemia and a mildly elevated HbA1c (<8%). Outside of pregnancy, it requires no treatment because it does not predispose to microvascular or 2 macrovascular complications. Usually, maternal hyperglycemia causes increased fetal insulin secretion resulting in an increased birth weight. Babies without the mutation are exposed to maternal hyperglycemia, secrete more insulin, and have an average 600-g increase in birth weight. This causes decreased insulin secretion and an average 500-g decrease in birth weight. The fetal genotype is inferred by fetal growth assessed by abdominal circumference measurement on ultrasound at the beginning of the third trimester (27 weeks). If the fetus is large (abdominal circumference >75th percentile for gestational age), the fetus most likely does not have the mutation and the treatment goal is maternal euglycemia to prevent macrosomia and postnatal hypoglycemia. The treatment is based on the genotype of the fetus, which is inferred by fetal growth. Systematic assessment of etiology in adults with a clinical diagnosis of young-onset type 2 diabetes is a successful strategy for identifying maturity-onset diabetes of the young. She was treated with metformin 1,000 mg twice daily, but her blood glucose levels remained in the 200s mg/dL (11. She had been told to limit her diet to control her diabetes and her weight decreased from 120 to 80 lb. The patient has a sister with thyroid disease and a daughter with multiple sclerosis. She had considerable muscle wasting and neurologic examination revealed diminished vibratory sensation in the lower extremities. At the time of evaluation, this patient was struggling with severe weight loss and peripheral neuropathy, symptoms characteristic of diabetic neuropathic cachexia. This syndrome was first described by Ellenberg in 1973 and most commonly occurs in middle-age men with fairly well- controlled type 2 diabetes but also may occur in women and in those 1 who have type 1 diabetes. Neuropathic pain and weight loss are both severe and rapidly progressive with patients losing up to 100 lb. Interestingly, most symptoms resolve within a year, although no specific therapy has been found to be effective, including improved glucose 2 control. This patient has poorly controlled diabetes, which progressed to requiring insulin in a short period of time. It is also the most sensitive marker, as it is present in the early stages of the disease and has a long duration in the serum. A 12-year prospective study of the relationship between islet antibodies and B-cell function at and after the diagnosis of adult-onset diabetes. Autoimmune diabetes not requiring insulin at diagnosis (latent autoimmune diabetes of the adult): definition, characterization, and potential prevention. Over the past 4 months, she also experienced a 10 lb weight gain, with no changes in diet or exercise. There were no known medical problems, and she did not take any medications, alcohol, or recreational drugs. According to the American Diabetes Association, diabetes is defined by the following: 1) A1C ≥6. It is important to recognize that plasma venous blood often is used for laboratory determination, and glucose values can be different from capillary fingerstick glucose measurements. Furthermore, blood glucose values 2 have a coefficient of variation that is up to 14%. Data are expressed as glucose values at the time-points over 24 h each day for the duration of study. Because of the physiologic lag in equilibration between these two compartments, an increase or decrease in glucose levels will first be apparent in the blood, followed by the interstitial fluid. This discrepancy also can occur when there is an alteration in the glycation process or red cell survival, such as in hemoglobinopathies, 5 iron deficiency anemia, or chronic kidney disease, or from medications. A hemoglobin electrophoresis showed a pattern of heterozygous positivity for the −α 3. In conditions in which the red cell survival or hemoglobin structures are abnormal, the value of A1C does not accurately reflect the glycemic levels. When using the criteria for diagnosing diabetes, physicians should be aware that limitations may exist for using A1C because of ethnicity, hemoglobinopathies, and altered red cell turnover. Racial differences in glycemic markers: a cross-sectional analysis of community-based data. Differences in hemoglobin A1C by race and ethnicity among patients with impaired glucose tolerance in the Diabetes Prevention Program. Ann Biol Clin 2000;58:425–429 Case 25 An Unexplained Decline in HbA in Spite of Persistent 1c Hyperglycemia 1 David S. Her historically poor glycemic control had resulted in the development of proliferative diabetic retinopathy (treated with panretinal photocoagulation), cataracts, diabetic nephropathy, recurrent pyelonephritis, distal symmetric polyneuropathy, entrapment, autonomic neuropathies, and trigger fingers. She also had euthyroid Hashimoto’s thyroiditis, lumbar and cervical disk disease, depression, and dermatitis herpetiformis. While her home glucose monitoring readings were in the 250–350 mg/dL range and her serum glucose measured at clinic visits were in the 250–400 mg/dL range, her HbA1c had declined from the usual 10–13% range to the 6–7% range and had remained at that level for >2 years. Subsequently there was a further fall in the HbA1c to the 3–4% range in spite of continued poor glycemic control by glucose readings. Her home glucose meter readings were compared with clinic serum glucose levels, and her home glucose monitoring equipment was found to be accurate. In addition, her serum fructosamine levels, which estimate average glucose over a 3-week period by measuring the glycosylation of albumin, were elevated at 3. When confronted with a patient with diabetes and poor glycemic control but an artifactually low HbA1c, several etiologies should be considered. The first consideration should be etiologies that decrease the life span of the red blood cell, such as hemolytic anemia, spherocytosis, elliptocytosis, hemoglobin F, or any other hemoglobinopathy. In addition, any acute or chronic blood loss, recent blood transfusion, 1 pregnancy, or recent childbirth can all decrease the HbA1c level. A review of her medication showed that she had been prescribed dapsone by her dermatologist for dermatitis herpetiformis. When her HbA1c had dropped to the 6– 7% range, treatment with dapsone 50 mg daily had been initiated. Because of poor clinical response, her dapsone was later increased to 100 mg, which coincided with the decrease in her HbA1c to the 3–4% range. Dapsone also can be used in combination with trimethoprim as an alternative therapy for pneumocystis carinii pneumonia.
The anes- thesia provider should be able to assess intravascular Clinical estimation of intravascular volume must be volume with sufcient accuracy to correct exist- relied upon because objective measurements of fuid ing fuid or electrolyte defcits and replace ongoing compartment volumes are not practical in the clini- losses cheap 10 mg metoclopramide amex gastritis bad breath. Fluid Loss (Expressed as Percentage Regardless of the method employed generic 10 mg metoclopramide free shipping gastritis operation, serial evalua- of Body Weight) tions are necessary to confrm initial impressions Sign 5% 10% 15% and to guide fuid best metoclopramide 10mg high protein diet gastritis, electrolyte order metoclopramide 10 mg visa gastritis vs pregnancy symptoms, and blood component therapy. Multiple modalities should complement Mucous Dry Very dry Parched one another, because all parameters are indirect, membranes nonspecifc measures of volume; reliance upon any Sensorium Normal Lethargic Obtunded one parameter may lead to erroneous conclusions. Important fac- pressure tors include recent oral intake, persistent vomiting Urinary flow Mildly Decreased Markedly or diarrhea, gastric suction, signifcant blood loss rate decreased decreased or wound drainage, intravenous fuid and blood administration, and recent hemodialysis if the Pulse rate Normal or Increased Markedly increased >100 bpm increased patient has kidney failure. However, these measurements are vasodilating or negative inotropic efects of anes- only indirect indices of intravascular volume, and thetics, are most ofen used. Late acidosis (including lactic acidosis), urinary specifc signs of hypervolemia in settings such as congestive gravitygreater than1. During spontaneous ventilation used in patients with normal cardiac and pulmonary the blood pressure decreases on inspiration. During function when volume status is difcult to assess positive pressure ventilation the opposite occurs. Colloid and lef ventricular end-diastolic volume is altered by solutions help maintain plasma colloid oncotic pres- the presence of mitral valve disease (particularly ste- sure (see Chapter 49) and for the most part remain nosis), severe aortic stenosis, or a lef atrial myxoma intravascular, whereas crystalloid solutions rapidly or thrombus, as well as by increased thoracic and pul- equilibrate with and distribute throughout the entire monary airway pressures (see Chapters 5, 20, 21, and extracellular fuid space. Finally, one should recognize that nents of colloids justifably argue that by maintaining multiple studies have failed to show that pulmo- plasma oncotic pressure, colloids are more efcient nary artery pressure monitoring leads to improved (ie, a smaller volume of colloids than crystalloids outcomes in critically ill patients, and that echocar- is required to produce the same efect) in restoring diography provides a much more accurate and less normal intravascular volume and cardiac output. Crystalloid proponents, on the other hand, maintain I ntravascular volume status is ofen difcult to that the crystalloid solutions are equally efective assess, and goal-directed hemodynamic and fuid when given in appropriate amounts. Crystalloids, when given in sufcient amounts, are just as efective as colloids in restoring intravascular volume. R e placing an intravascular volume defcit with Crystalloids are usually considered as the initial crystalloids generally requires three to four resuscitation fuid in patients with hemorrhagic and times the volume needed when using colloids. S u r gical patients may have an extracellular fuid in patients undergoing plasmapheresis and hepatic defcit that exceeds the intravascular defcit. S e v e r e intravascular fuid defcits can be more eforts following initial administration of crystalloid rapidly corrected using colloid solutions. For losses primarily involv- defcits (eg, hemorrhagic shock) prior to the arrival ing water, replacement is with hypotonic solutions, of blood for transfusion, and (2) fuid resuscitation also called maintenance-type solutions. If losses in the presence of severe hypoalbuminemia or con- involve both water and electrolytes, replacement ditions associated with large protein losses such as is with isotonic electrolyte solutions, also called burns. Glucose is provided in most initial resuscitation protocols (and we strongly some solutions to maintain tonicity, or prevent keto- recommend that burn surgeons and anesthesia per- sis and hypoglycemia due to fasting, or based on sonnel develop a resuscitation protocol and follow tradition. Children are prone to developing hypo- it), but may be considered following initial resuscita- glycemia (<50 mg/dL) following 4- to 8-h fasts. M any clinicians also use colloid solutions in The most commonly used fuid is lactated Ringer’s c onjunction with crystalloids when fuid replace- solution. Although it is slightly hypotonic, provid- ment needs exceed 3–4 L prior to transfusion. It ing approximately 100 mL of free water per liter and should be noted that colloid solutions are prepared tending to lower serum sodium, lactated Ringer’s in normal saline (Cl− 145–154 mEq/L) and thus can generally has the least efect on extracellular fuid also cause hyperchloremic metabolic acidosis (see composition and appears to be the most physiologi- above). Some clinicians suggest that during anesthe- cal solution when large volumes are necessary. The sia, maintenance (and other) fuid requirements be lactate in this solution is converted by the liver into provided with crystalloid solutions and blood loss bicarbonate. When given in large volumes, nor- be replaced on a milliliter-per-milliliter basis with mal saline produces a dilutional hyperchloremic colloid solutions (including blood products). Five per- and 25% solutions) and plasma protein fraction cent dextrose in water (D W5 ) is used for replacement (5%). Both are heated to 60°C for at least 10 h to of pure water defcits and as a maintenance fuid for minimize the risk of transmitting hepatitis and other patients on sodium restriction. Plasma protein fraction contains α- is employed in therapy of severe symptomatic hypo- and β-globulins in addition to albumin and has natremia (see Chapter 49). Gelatins are associated with histamine- The osmotic activity of the high-molecular-weight mediated allergic reactions and are not available in substances in colloids tends to maintain these solu- the United States. Although the intravascu- 70 (Macrodex) and dextran 40 (Rheomacrodex), 1 lar half-life of a crystalloid solution is which have average molecular weights of 70,000 20–30 min, most colloid solutions have intravascu- and 40,000, respectively. The relatively greater better volume expander than dextran 40, the latter cost and occasional complications associated with also improves blood fow through the microcircu- colloids may limit their use. Dextrans can also be antigenic, and both mild For the first 10 kg 4 mL/kg/h and severe anaphylactoid and anaphylactic reactions For the next 10 kg Add 2 mL/kg/h are described. Dextran 1 (Promit) may be adminis- tered prior to dextran 40 or dextran 70 to prevent For each kg above 20 kg Add 1 mL/kg/h severe anaphylactic reactions; it acts as a hapten and Example: What are the maintenance fl1 uid requirements for a 25-kg child? Hetastarch (hydroxyethyl starch) is available in multiple formulations, which are designated by sweating, and insensible losses from the skin and concentration, molecular weight, degree of starch lungs. Normal maintenance requirements can be substitution (on a molar basis), and ratio of hydrox- estimated from Table 51–3. A greater fast without any fuid intake will have a preexisting ratio of C2 versus C6 substitution leads to longer per- defcit proportionate to the duration of the fast. The starch molecules are derived defcit can be estimated by multiplying the normal from plants. Smaller starch molecules are eliminated maintenance rate by the length of the fast. For the by the kidneys, whereas large molecules must frst be average 70-kg person fasting for 8 h, this amounts to broken down by amylase. In fact, the real tive as a plasma expander and is less expensive than defcit is less as a result of renal conservation. Moreover, hetastarch is nonantigenic, and all, how many of us would feel the need to consume anaphylactoid reactions are rare. Coagulation stud- nearly 1L of fuid upon awakening afer 8 hours of ies and bleeding times are generally not signifcantly sleep? Preoperative bleeding, vomit- lower molecular weight formulations can safely be ing, diuresis, and diarrhea are ofen contributory. Occult losses (really redistribution; see below) due to fuid sequestration by traumatized or infected tis- sues or by ascites can also be substantial. Increased Perioperative Fluid Therapy insensible losses due to hyperventilation, fever, and Perioperative fuid therapy includes replacement of sweating are ofen overlooked. Everything related drapes, accuracy is important to guide fuid therapy to “third-space” fuid loss is controversial, including and transfusion. Trauma- surgical suction container and visual estimation of tized, infamed, or infected tissue can sequester large the blood on surgical sponges (“4 by 4’s”) and lapa- amounts of fuid in the interstitial space and can rotomy pads (“lap sponges”). A fully soaked 4 × 4 translocate fuid across serosal surfaces (ascites) or sponge is said to hold 10 mL of blood, whereas a into bowel lumen. More accurate esti- the interstitial space is especially important; protein- mates are obtained if sponges and “laps” are weighed free fuid shif across an intact vascular barrier into before and afer use, which is especially important the interstitial space is exacerbated by hypervolemia, during pediatric procedures. Use of irrigating solu- and pathological alteration of the vascular barrier tions complicates estimates, but their use should be allows protein-rich fuid shif.
