Positional hypoxemia in unilateral lung disease

morbidity and mortality associated with this condition, and the necessity for prompt and vigorous intervention, dictate that a high level of suspicion must be maintained for it in the assessment of the acutely sick, neurologically compromised child. [Editor's note: The clinical clues for the emergency physician are the biphasic nature of the disease: a child who appears to be recovering from a viral illness suddenly starts vomiting. It is important to think of Reye's syndrome rather than to conclude that the mother is inadequate or hyperanxious.] Tony Tercier, MD

ARTERIAL BLOOD GASES

sodium chloride. The manufacturer states that no physical or chemical incompatibilities with this material are known. Hetastarch has been widely used in Europe but not in the United States. Two small studies comparing Hetastarch with albumin found no significant differences in plasma volume expansion, hemodynamic function, or respiratory function. One large study found the incidence of severe reactions to hetastarch to be 0.006%. compared to 0.003% for plasma protein solutions. The plasma volume expansion effect from this material decreases over the 24 to 36 hours following administration. [Editor's note: With as much clin. ical experience, as well as research data. as exists concernmg the lack of need for colloid in management of hypovolemic shock, I fail to understand why search for these agents continues.] Stephen Cantrill, MD

Positional h y p o x e m i a in unilateral lung d i s e a s e Remolina C Khan AU. Santiago TV e t a N Engl J Med 304:523-525 Feb 1981

DIARRHEA GASTROINTESTINAL DISORDERS DIARRHEA

Diarrhoea: c a u s e s a n d s p e c i f i c t r e a t m e n t Arterial blood gases were analyzed in nine patients with unilateral lung disease. Measurements of fractional concentration of inspired oxygen were made with the patients in the supine, left lateral, and right lateral positions. It was found that arterial PO2 was significantly decreased with the diseased lung dependent 158.5 - 2.7 m m Hg) or with the pauent in the supine position ,66.8 ~ 3.3 m m Hg), while the PO2 was highest when the healthy lung was dependent (106.1 z 12.7 m m Hg). There were no significant differences in arterial pH and PCO2 with the changes in position. When the measurements were repeated after resolution of the lung disease in six patients, it was found that the positional PO~ differences had completely resolved. The authors postulate that the positional PO2 differences seen m these patients were due to ventilation/perfuslon mismatches produced by increased blood flow to the dependent lung with a diseased lung being unable to appropriately increase regional ventilation. [Editor's note: This article suggests that field transport of patients with suspected unilateral lung disease should have the good lung dependent.] Linda A. Wahby, MD

Kronborg IJ Howard A Drugs 21:62-68 Feb 1981

Diarrhea can be either acute or chronic. Acute diarrhea is primarily infective, and most cases are self-limiting, reqmring no special therapy. Infective diarrhea is further classified as either enterotoxic or enteroinvasive depending upon whether the infectious agent produces a diarrheogenic toxin or invades the gut mucosa. Therapy of severe infective diarrhea includes hydration with balanced glucose and electrolyte solutions, and antibiotics in some cases. The use of antimotility agents can increase bacterial retenuon, prolonging the illness and predisposing to sepsis. Acute diarrhea secondary to antibioucs is linked to overgrowth of clostridium difficile, a toxin-producing anerobe which is sensitive to therapy with vancomycin. Disorders associated with chronic diarrhea include inflammatory bowel disease, lactose intolerance, sprue, pancreatic insufficiency, laxative abuse, irritable bowel syndrome, and a variety of endocrine disorders. Acute exacerbations of chronic diarrhea are treated with supportive measures, while further therapy is aimed at the underlying condition Again, antimotility agents are to be used with caution, especially in ulcerative COLLOID ARTIFICIAL PLASMA VOLUME EXPANSION colitis, where such agents can precipitate toxic megacolon. Bulk binding agents leg, kaolinl have no proven benefit in the symptomatic management of diarrhea. Effective antiH e t a s t a r c h ( H e s p a n ®) D motility agents include Lomotil~, loperamide, and codeine a new plasma expander phosphate. Lomotil ® and codeine can cause respiratory The Medical .Letter 23.16 depression in children, whereas this does not appear to be a Feb 1981 problem with loperamide. [Editor's note: This is a useful review of diarrhea. A problem not covered is the transient patient who appears in the emergency department for relief Hetastarch (Hespan ® - - American Critical Care) is a newof his discomfort during vacation or business travel. Such ly marketed artificial colloid for use in plasma volume expatients will be very grateful for an antimotility agen t, pansion, which is claimed to be as effective and safe as albueven at the cost of prolonging the duration of illness.] min, but at a fraction of the cost; Hetastarch, a branched William Jantsch, MD polymer of glucose, is available as a 6% solution in 0.9% Annals of Emergency Medicine 110/101 11:2 February 1982