Sciatic neuropathy secondary to total hip arthroplasty wear debris

Sciatic neuropathy after total hip arthroplasty can result from several causes. We present a case in which a large cystic mass developed around a failed total hip arthroplasty. The lesion extended through the greater sciatic notch and into the pelvis producing sciatic nerve compression. The diagnosis was delayed, and the patient underwent a laminectomy without relief of symptoms before an abdominopelvic computed tomography (CT) scan revealed the mass. After revision of the components and excision of the accessible portion of the lesion, the symptoms improved. Resolution of the intrapelvic portion of the mass was demonstrated on follow-up CT scan, suggesting that retroperitoneal resection of this type of lesion may not be required at the time of revision of the components.

Plasma volume expansion with solutions of hemoglobin, albumin, and Ringer lactate in sheep

We have measured plasma volume expansion (Evans blue and hematocrit changes) and hemodynamic responses in conscious hemorrhaged and normovolemic splenectomized sheep after a 30-min infusion of either 20 ml/kg of diaspirin cross-linked hemoglobin (DCLHb), 20 ml/kg of human albumin (Alb), or 60 ml/kg of a solution of Ringer lactate (RL). All regimens expanded blood volume and increased blood pressure and cardiac output after hemorrhage. However, only 15 +/- 3% of the infused volume of RL was evident as intravascular expansion 10-min postinfusion, compared with 67 +/- 16% and 139 +/- 139% for Alb and DCLHb, respectively. DCLHb infusions were associated with higher blood pressures and lower cardiac outputs compared with RL and Alb infusions, but the increased oxygen content of blood with DCLHb resulted in systemic delivery of oxygen similar to that of the other infusions. These differences in hemodynamics and vascular volume continued for 6 h, and at 24 h vascular volume and all hemodynamics were similar in all three groups. The better volume expansion with DCLHb may be due to greater mobilization of endogenous interstitial protein or reduced transcapillary loss as total intravascular endogenous plasma protein increased after infusion of DCLHb, whereas there was an apparent loss of endogenous intravascular protein after infusions of Alb and RL. Vasoconstriction by DCLHb is one mechanism that could lower blood-to-tissue transport of fluid and protein. In addition to its oxygen-carrying capacity and vasoactivity, DCLHb is associated with volume expansion properties out of proportion to its colloid osmotic pressure.

L-arginine and endothelin receptor antagonist bosentan counteract hemodynamic effects of modified hemoglobin

Pyridoxalated hemoglobin polyoxyethylene conjugate (PHP), a nitric oxide scavenger, causes systemic and pulmonary vasoconstriction in normal and septic sheep. We studied the effect of L-arginine and the endothelin-1 (ET-1) antagonist bosentan on the PHP response to determine whether the PHP-induced vasoconstriction resulted predominantly from the action of ET-1 or solely from removal of NO. After 24 h of carrier solution (nonseptic sheep), sheep received PHP (20 mg/kg/h; n = 5), PHP plus L-arginine (at 28 h, 100 mg/kg bolus and 500 mg/kg for 1 h) plus bosentan (at 32 h, 10 mg/kg; n = 6), and only L-arginine and bosentan (n = 5). These protocols were repeated after 24 h of Pseudomonas aeruginosa (S, 6x10(6) colony-forming units/kg/h). PHP induced vasoconstriction in septic and nonseptic sheep for the duration of its infusion. In nonseptic sheep, neither L-arginine nor bosentan significantly lowered systemic (SVRI) and pulmonary (PVRI) vascular resistance and did not antagonize the PHP-induced vasoconstriction. During sepsis, SVRI fell and cardiac index (CI) rose. L-arginine and bosentan further decreased SVRI (L-arginine: 34+/-2%*, p<.05; bosentan: 35+/-5%*, p<.05) and PVRI (L-arginine: 28+/-2%*, p<.05; bosentan: 33+/-7%*, p<.05) and increased CI (L-arginine: 29+/-4%*, p<.05; bosentan: 11+/-5%, NS). Both agents antagonized the PHP-induced vasoconstriction lowering SVRI (L-arginine: 29+/-3%*, p<.05; bosentan: 26+/-5%*, p<.05) and PVRI (L-arginine: 27+/-4%*, p<.05; bosentan: 32+/-4%*, p<.05) to levels before PHP administration. Plasma ET-1 levels increased during sepsis (from 9.8+/-.2 to 15.6+/-.7* pg/mL, p<.05) and fell during PHP infusion (to 9.7+/-1.6* pg/mL, p<.05). In nonseptic sheep, ET-1 levels decreased during PHP (from 8.5+/-.6 pg/mL to 5.9+/-.6*, p<.05). Bosentan increased ET-1 levels 2.7 times higher in septic than in nonseptic sheep. We conclude that during sepsis, the NO scavenger PHP unmasks an underlying ET-1 mediated vasoconstriction, and its effect is antagonized by L-arginine and bosentan.

Continuous infusion of pyridoxalated hemoglobin polyoxyethylene conjugate in hyperdynamic septic sheep

Cell-free hemoglobin solutions can scavenge nitric oxide and therefore increase mean arterial pressure (MAP). The present study investigated the effects of a continuous low-dose infusion of modified hemoglobin during ovine hyperdynamic sepsis. 13 sheep received a continuous infusion of live Pseudomonas aeruginosa bacteria for 48 h. Animals that survived the first 24 h of sepsis (n=12) were randomly assigned either to a treatment group that received 20 mg x kg(-1) x h(-1) pyridoxalated hemoglobin polyoxyethylene conjugate (PHP) for 20 h or to a control group that received the same volume of the vehicle for 20 h. MAP increased in the treatment group during 4 h of PHP infusion 12.7+/-1.7 mmHg (p < .05) and after 20 h of PHP infusion MAP was still 12.4+/-2.1 mmHg above the MAP before starting PHP (p < .05). MAP in the control group did not change significantly from 24 h to 48 h of sepsis. No differences in regional blood flow were seen between groups. Bacterial counts in the spleen and kidney were lower in the treatment group than in the control group. Continuous low-dose infusion of PHP can normalize systemic vascular resistance and MAP for long periods without deterioration of regional blood flow or bacterial clearance.

Pyridoxalated hemoglobin polyoxyethylene conjugate reverses hyperdynamic circulation in septic sheep

We investigated the effects of modified hemoglobin on regional blood flow and function of different organs during hyperdynamic sepsis. Fourteen sheep were surgically prepared for the study. After a 5-day recovery period, a continuous infusion of live Pseudomonas aeruginosa bacteria was begun and maintained for 48 h. At 24 h, after a hyperdynamic circulation had developed, the animals were randomly assigned to two groups: 1) a treatment group (n = 7) that received an infusion with 100 mg/kg pyridoxalated hemoglobin polyoxyethylene conjugate (PHP) over 30 min and 2) a control group (n = 7) that received only the vehicle. PHP infusion increased mean arterial pressure from 86 +/- 2.8 to 101.8 +/- 3.5 mmHg (P < 0.05) and systemic vascular resistance index from 769 +/- 42.1 to 1,087 +/- 56.8 dyn . s . m2 . cm-5 (P < 0.05). PHP infusion did not decrease regional blood flow, measured with fluorescent microspheres, below the baseline values in any of the analyzed tissues. None of the investigated blood chemistry variables showed any changes indicative of impaired organ function after PHP infusion. In our model of ovine sepsis we found no side effects after PHP infusion that would limit the use of PHP as a nitric oxide scavenger in sepsis.

Nitric oxide synthase inhibition restores hypoxic pulmonary vasoconstriction in sepsis

Hypoxic pulmonary vasoconstriction (HPV) is inhibited by inhaled nitric oxide (NO) in healthy animals and is blunted in endotoxemia. We investigated whether the loss of HPV during sepsis could be reversed by NO synthase (NOS) inhibition. Hypoxic challenges were induced in intubated, awake sheep breathing 100% nitrogen to the left lung and 100% oxygen to the right lung. HPV was assessed as the decrease in left pulmonary blood flow during hypoxia, measured with an ultrasonic flow probe around the left pulmonary artery. Group I (n = 5) received carrier solutions and Groups II (n = 6) and III (n = 8) received an infusion containing Pseudomonas aeruginosa. After 24 h, Group III also received an infusion of 6.6 mg.kg.h-1 N omega-monomethyl-L-arginine (L-NMMA). After 24 h of sepsis, HPV decreased from 60 +/- 9% in Group II and 56 +/- 4% in Group III to 27 +/- 2% and 26 +/- 4%, respectively. Group I showed no change in HPV. During infusion of L-NMMA, HPV increased to 38 +/- 4%. Pulmonary shunt during hypoxia increased in Group III to 161 +/- 10% of its baseline value, and decreased to 121 +/- 11% during infusion of L-NMMA. We conclude that L-NMMA improves but does not restore HPV, indicating that other vasodilatory mediators besides NO also influence HPV in sepsis.

Pyridoxalated hemoglobin polyoxyethylene conjugate does not restore hypoxic pulmonary vasoconstriction in ovine sepsis

OBJECTIVES

Hypoxic pulmonary vasoconstriction, a protective mechanism, minimizes perfusion of underventilated lung areas to reduce ventilation-perfusion mismatching. We studied the effects of sepsis on hypoxic pulmonary vasoconstriction and attempted to determine whether hypoxic pulmonary vasoconstriction is influenced by pyridoxalated hemoglobin polyoxyethylene conjugate, a nitric oxide scavenger.

DESIGN

Prospective, randomized, controlled experimental study with repeated measures.

SETTING

Investigational intensive care unit at a university medical center.

SUBJECTS

Nineteen female merino sheep, divided into three groups: group 1, controls (n = 5); group 2, sheep with sepsis (n = 6); and group 3, septic sheep treated with pyridoxalated hemoglobin polyoxyethylene conjugate (n = 8).

INTERVENTIONS

All sheep were instrumented for chronic study. An ultrasonic flow probe was placed around the left pulmonary artery. After a 5-day recovery, a tracheostomy was performed and a double-lumen endotracheal tube was placed. Animals in groups 2 and 3 received a 48-hr infusion of live Pseudomonas aeruginosa (6 x 10(4) colony-forming units/kg/hr). After 24 hrs, sheep in group 3 received pyridoxalated hemoglobin polyoxyethylene conjugate (20 mg/kg/hr) for 16 hrs; sheep in groups 1 and 2 received only the vehicle. Hypoxic pulmonary vasoconstriction was repeatedly tested by unilateral hypoxia of the left lung with 100% nitrogen. Hypoxic pulmonary vasoconstriction was assessed as the change in left pulmonary blood flow.

MEASUREMENTS AND MAIN RESULTS

In the animals in group 1, left pulmonary blood flow decreased by 62 +/- 8 (SEM)% during left lung hypoxia and remained stable during repeated hypoxic challenges throughout the study period. After 24 hrs of sepsis, left pulmonary blood flow decreased from 56 +/- 10% to 26 +/- 2% (group 2) and from 50 +/- 8% to 23 +/- 6% (group 3). In the sheep in group 2, there was no adaptation over time. Pulmonary shunt fraction increased. Pyridoxalated hemoglobin polyoxyethylene conjugate had no effect on hypoxic pulmonary vasoconstriction or pulmonary shunt. The animals receiving the bacterial infusion developed a hyperdynamic circulatory state with hypotension, decreased systemic vascular resistance, and increased cardiac output. Pyridoxalated hemoglobin polyoxyethylene conjugate increased mean arterial pressure and systemic vascular resistance but did not influence cardiac index. Pulmonary arterial pressure was increased during sepsis and increased even further after pyridoxalated hemoglobin polyoxyethylene conjugate administration. Oxygenation and oxygen delivery and uptake were not affected by pyridoxalated hemoglobin polyoxyethylene conjugate.

CONCLUSIONS

Hypoxic pulmonary vasoconstriction is blunted during sepsis and there is no adaptation over time. It is not influenced by pyridoxalated hemoglobin polyoxyethylene conjugate. Pyridoxalated hemoglobin polyoxyethylene conjugate reversed hypotension and, with the exception of an increase in pulmonary arterial pressure, had no adverse effects on hemodynamics or oxygenation.

Surgical correction of angular deformity of the knee in children with renal osteodystrophy

Twenty-nine children with renal osteodystrophy (RO) and angular deformities about the knee were studied, including 19 in whom 36 corrective operations were performed. Corrective osteotomy of the distal femur was performed in 20 knees, osteotomy of the proximal tibia in 11 knees, combined femoral/tibial osteotomy in three knees, and medial physeal stapling in two knees. The indication for surgery was a deformity significant enough to interfere with gait. Complications occurred in three patients and recurrence severe enough to require repeated surgery occurred in four patients. Patients who required repeated osteotomy appeared to have had poor metabolic control during the initial surgery, as measured by an increased alkaline phosphatase. Surgery for children with RO and knee deformities is quite feasible but requires careful surgical planning and preoperative metabolic stabilization. Whether to correct the femur or tibia can be determined by evaluating full-length films of the lower extremities.

Pulmonary blood flow regulation: influence of positive pressure ventilation

Positive pressure ventilation with PEEP has been reported to reduce hypoxic pulmonary vasoconstriction (HPV) and thus increase venous admixture. This effect was investigated in six chronically instrumented unanesthetized healthy sheep. The change in left pulmonary arterial blood flow (Qlpa, ultrasonic transit time) in response to unilateral lung hypoxia (10 min of N2 alternately to the left (LLH) and right lung (RLH) was evaluated during mechanical ventilation with and without PEEP of 10 cm H2O in comparison to spontaneous breathing. In the spontaneously breathing animal and during mechanical ventilation without PEEP, Qlpa decreased during LLH from 30% to 16% of cardiac index, during RLH it increased to 51%. With 10 cm H2O of PEEP, Qlpa showed an identical reaction to hypoxia both in the left and right lung. It is concluded that mechanical ventilation and PEEP up to 10 cm H2O does not interfere with pulmonary blood flow regulation to hypoxia.

The electrical effect of two commonly used clinical stimulators on traumatic edema in rats

The purposes of this study were to determine the effect of electrical stimulation on traumatic rat hind-paw edema and to establish whether there would be a difference in edema reduction when two types of stimulators were used. The animals were divided into a control group (n = 15) and two experimental groups, one group receiving monophasic pulsed current (MPC group, n = 15) and the other group receiving symmetrical biphasic pulsed current (SBPC group, n = 14). The right hind-paw volume of all groups was measured prior to traumatization and at 24, 48, 72, and 96 hours posttrauma. Following the 24-, 48-, and 72-hour measurements, 1 hour of electrical stimulation was administered to the experimental groups. The control group received sham treatment. Results revealed significant edema reduction in all groups over the 96-hour period, with each group's greatest change in paw volume occurring 48 hours posttrauma. At the final paw volume measurement, there was no significant difference between the MPC and control groups or between the MPC and SBPC groups. The SBPC group, however, showed less reduction in edema than did the control group. One hour of electrical stimulation per day over 3 consecutive days failed to demonstrate significant edema reduction in either the MPC group or the SBPC group as compared with the control group. The results of this study demonstrated that the electrical stimulation characteristics and procedures currently used in the clinic do not significantly reduce extant edema caused by trauma in rat hind limbs.