Extracellular fluid and its proteins: dehydration, shock, and recovery

This review highlights characteristics of extracellular fluid (ECF) that are often overlooked. ECF has, in addition to plasma and interstitial fluid (ISF) surrounding cells, a third large compartment, the ISF of skin and connective tissue. This acts as a reservoir that gives up ECF to plasma volume (PV) in order to sustain circulation in the event of either shock or dehydration. While Starling forces drive filtration, ECF is returned to PV more by lymph and less by Starling forces than previously appreciated. Lymph return to PV is dependent on physical activity and muscle contraction to overcome gravity. Regional change in metabolic rate alters the need for oxygen and nutrients that is met by a regional increase in capillary blood flow. Blood flow is controlled by vasoactive compounds released in response to a drop in PO₂; these relax capillary smooth muscle to increase blood flow and delivery of oxygen and nutrients. Plasma proteins, including albumin, are filtered into the interstitium through larger pores than those filtering ECF. The rate of protein filtration is set by size and charge of these larger endothelial pores and by size and charge of proteins. Charge of these pores, hence albumin permeability, is regulated by many of the same vasoactive compounds that control capillary flow. As a consequence, in response to gravitational stress and other forms of shock that reduce effective circulation, albumin as well as ECF is rapidly shifted from plasma and sequestered in ISF. When this has occurred, as in burn shock, restoration is better effected by generous expansion of ECF with Ringer’s solution alone, rather than with Ringer’s solution supplemented with human serum albumin or other colloid. Restoring both PV and ISF volume restores lymph circulation and returns sequestered albumin to PV. Received: 12 November 1998 / Revised: 30 March 1999 / Accepted: 2 April 1999     

Edema and acute renal failure

Acute renal failure (ARF) with overhydration and edematous state may follow Acute endocapillary proliferative glomerulonephritis and extracapillary glomerulonephritis, because of reduction of the glomerular capillary area available for filtration. But ARF may also be observed in edematous patients with minimal change nephrotic syndrome; it may require dialysis until recovery and is attributable to some of the following factors: (1) ischemic renal injury, (2) hypovolemia, (3) interstitial edema with tubular collapse, (4) redistribution of renal blood flow (RBF) from cortical to juxtaglomerular nephrons, (5) decrease of capillary filtration coefficient (Kf), (6) use of nonsteroidal antiinflammatory drugs. Congestive heart failure also leads to prerenal azotemia and edema formation secondary to salt retention. Multiple organ dysfunction syndrome (MODS) is frequently associated with ARF; but edema occurs even without ARF in septic patients with severe inflammatory response syndrome (SIRS). ARF may follow severe burns; burned patients are frequently edematous because of a rapid leak of fluid from the vascular bed into the wound; edema in undamaged areas occurs in the 'flow phase', because of a fall of oncotic pressure because of massive loss of plasma proteins into the wound. Edema must be treated with diuretics or by dialysis.     

Chronic dehydration stone disease

A study was made of 819 patients attending a metabolic stone clinic. A firm diagnosis was made in 708 (86%) and in 132 of these (19%) the diagnosis was thought to be chronic dehydration. The records were available for study for 87 males and 11 females in the chronic dehydration group. The mean age at presentation was 43 years. The causes of chronic dehydration were hot climate (62%), with hot occupation and low water intake almost equal in second place. In patients with a single cause of chronic dehydration, 57% also had a dietary risk factor for urolithiasis and this was most commonly high oxalate intake. Following dietary advice, the mean urinary volume increased from 1720 to 2475 ml/24 h. This was accompanied by a rise in mean urinary calcium from 6.02 to 6.96 mmol/24 h, presumably due to the calcium in the additional water drunk. Urinary oxalate did not change significantly. The mean follow-up time was 4.85 years and the stone recurrence rate was low. It was concluded that chronic dehydration is a common cause of urolithiasis; this can be treated satisfactorily by increasing water intake plus dietary advice in certain cases.     

Edema volume, not timing, is the key to success in lymphedema treatment

BACKGROUND: Prospective evaluation of the percutaneous tracheostomy by the guide wire dilating forceps (GWDF) technique. METHODS: In 50 selected patients percutaneous tracheostomy with fiberscopic control was performed and evaluated. RESULTS: Most percutaneous tracheostomies were performed without any adverse effect. No life-threatening complications or deaths were related to the procedure. The procedure was successful in 49 of 50 patients (98%). In 1 patient the procedure was converted to an open tracheostomy because significant bleeding occurred. Five perioperative complications, including this significant bleeding and four minor complications, occurred in 50 patients (10%). Early complications occurred in 6 of 48 patients (13%), including one significant bleeding and five minor complications. A subglottic stenosis occurred in 2 of 36 successfully decannulated patients (6%). In one case this was certainly due to prolonged endotracheal intubation. CONCLUSIONS: The GWDF technique is a safe and efficient bedside alternative to open tracheostomy. Fiberscopic control is recommended to increase the safety of the procedure. Although studies of late complications are necessary, it appears to be justifiable to consider percutaneous tracheostomy for patients who require tracheostomy.     

Brain Edema XII: Proceedings of the 12th International Symposium on Brain Edema and Brain Tissue Injury, Hakone, Japan, November 10-13, 2002 (Acta Neurochirurgica. Supplement 86.

Pain clinics used to be the preserve of anaesthetists who enjoyeddoing difficult nerve blocks, but then it was realized thattreating patients with chronic pain was rather more complexand we started to refer to ourselves as consultants in painmanagement. More recently, the concept of pain medicine seemsto be re-emerging, and this book is called Pain Medicine Manual.This is