Postoperative pain treatment on wards – USA experience

A large variety of treatment options are now available to experienced pain therapists. Effective doses of opioids can be administered by the oral, rectal, transdermal, or sublingual route, or by subcutaneous, intramuscular, or intravenous injection or infusion. Patient–controlled analgesia (PCA) is now familiar and commonly available. Most PCA pumps also offer the option to add a continuous background infusion to the basic patinet–controlled mode with the possibility of therapeutic benefits and new problems. Alternative delivery routes and PCA drugs have been reported.
A variety of neural blockade techniques can provide effective and safe analgesia. These include topical application, local infiltration of incicions, and blockade of peripheral nerves or plexuses. Intrathecal and epidural opioids are now commonly used to control pain following a wide variety of surgical procedures, but many questions remain to be answered.
The concept of postoperative pain management by anesthesiologists is growing in popularity in North America. It is not surprising that such a revolutionaryidea involving basic changes in long–established practices is receiving attention not only from clinicians, but also from economists and politicians. One manifestation of this attention in the United States is a clinical practice guideline entitled Acute Pain Management: Operative or Medical Procedures and Trauma. Important elements of the guideline include recognition of historic inadequacies in postoperative pain management and acknowledgement of the importance of effective pain control.     

Renal excretion of endothelin in children is influenced by age and diuresis

Mattyus I, Zimmerhackl LB, Schwarz A, Hentschel M, Brandis M, Miltenyi M, Tulassay T. Renal excretion of endothelin in children is influenced by age and diuresis. Acta Pædiatr 1994;83:468–72. Stockholm. ISSN 0803–5253 Endothelin is a peptide with vasoactive and diuretic potential. Its release has been demonstrated from endothelial and renal epithelial cells. Urinary excretion of endothelin, as shown by others, is thought to reflect intrarenal production. We measured endothelin by RIA in a population of healthy children from Germany and Hungary (group 1), neonates (group 3) and children before and during forced diuresis (groups 2a and 2b). Group 1 consisted of 24 children living in Germany and 13 children resident in Hungary. The age range in this group was 2.9–17 years. Daily excretion correlated significantly with age (r= 0.48, p < 0.001), but endothelin excretion corrected for body surface area remained constant with regard to the age group studied. This indicates that body or kidney size may influence endothelin excretion, respectively. There was no difference in endothelin excretion between the two countries. In premature infants and neonates (group 3), daily excretion of endothelin was highest in infants with very low gestational ages and decreased in full-term neonates to values not significantly different to the group of older children. The high values in premature infants may have been influenced by mechanical ventilation of physical stress, which cannot be differentiated in this study, however. In contrast to reported results in adults, renal excretion of endothelin was correlated positively to urine flow in all groups. Furthermore, the influence of forced diuresis was evaluated in 10 children with oncological disease before (group 2a) and during (group 2b) forced diuresis with fluid load (3 l/m²; n= 4) and fluid load with furosemide injection (0.3–1.0 mg/kg body weight; n= 6). During this diuretic state, endothelin excretion was enhanced significantly.     

Effects of intramedullary reaming and nailing on blood flow in rat femora.

The right femur in 40 rats was reamed, and in 40 others it was additionally nailed. Analysis of bone blood flow was performed by the distribution of radiolabeled microspheres at different postoperative time intervals. Blood-flow measurements were accompanied by analyses of hydroxyproline and calcium contents. Immediately after reaming, the blood flow of the diaphyseal part of the femur was reduced to approximately one third of that of the intact femur, whereas the contents of hydroxyproline and calcium were reduced by 10 percent. Within 1 week, the blood flow was normal. This study provides evidence that the presence of a nail does not interfere with the restoration of bone blood flow. Restoration of blood flow in bone apparently is a rapid process. The replacement of hydroxyproline and calcium contents seemed to be linked to flow, as no increase in these constituents were found until the blood flow had approximated the level of the intact femur.     

Effects of a distal venting hole in the femur during total hip replacement

In 18 patients who underwent total hip replacement, the intramedullary pressure in the femur was measured during the insertion of the femoral prosthesis component. Half the patients had a pressure release hole (diameter 4.5 mm) drilled into the medullary canal at the distal end of the femur, the other half not. In the patients without a venting hole, the intramedullary pressure increased transiently to a median of 390mmHg during the insertion of the femoral stem, while those with a venting hole only showed an increase to 23mmHg. A drop in arterial oxygen tension of 2.2kPa and in thrombocytes of 51 x 10(9)/1 was found in those without a venting hole, while the corresponding values in those with a venting hole were 0.9kPa and 20 x 10(9)/1. Furthermore, a significant correlation was demonstrated between the increase in intramedullary pressure and the drop in oxygen tension and in blood platelets. No significant change in blood pressure was measured during operation in either group.     

Does cement increase the risk of infection in primary total hip arthroplasty? Revision rates in 56,275 cemented and uncemented primary THAs followed for 0-16 years in the Norwegian Arthroplasty Register

Introduction The cementation of a total hip prosthesis may cause bone necrosis, either by direct toxicity or by generation of heat during the polymerization process. This necrotic bone may create conditions that encourage the growth of bacteria. We compared the revision rates due to infection in primary uncemented total hip arthroplasties (THAs) with those of cemented THAs with antibiotic-loaded cement and to those of cemented THAs without antibiotic cement.

Methods Data from the Norwegian Arthroplasty Register for the period 1987-2003 were used. To have comparable groups, we analyzed only primary THAs performed because of primary osteoarthrosis, and where both the acetabular and the femoral component of the prosthesis were either uncemented or cemented (n = 56,275).

Results In total, 252 revisions due to infection were reported. Compared to the uncemented THAs (n = 5,259), the risk of revision due to infection for THAs without antibiotic cement (n = 15,802) was increased 1.8 times (CI 1.0-3.1; p = 0.04). No differences could be detected when compared to THAs with antibiotic-loaded cement (n = 35,214) (RR 1.2, CI 0.7-2.0; p = 0.5). The average operating time for uncemented THAs was 15 min less than for cemented THAs.

Interpretation The risk of revision due to infection was the same for uncemented and for cemented arthroplasties with antibiotic-loaded cement, but higher for cemented arthroplasties without antibiotic cement. Our findings can be explained by reduced resistance to infection caused by the cement, which appears to be neutralized by adding antibiotic to the cement.