Continuous cold therapy in total knee arthroplasty.

This article describes a retrospective study that assessed 52 consecutive patients who underwent total knee arthroplasty (TKA) between January 1, 1992 and September 15, 1992. Thirty-three patients underwent TKA and received cold therapy pads placed over a thin dressing in the operating room. Nineteen patients underwent TKA using an identical operative and postoperative procedure, but did not receive continuous cold therapy. Continuous cold therapy consisted of two sterile plastic pads connnected by rubber hoses containing cool water from an electric main unit that maintained a constant temperature of 42 degrees F for the immediate postoperative period. Cold therapy pads were used an average of 3 days and removed with the first dressing change. Patients who had continuous cold therapy averaged a 200 cc decrease in postoperative blood loss. There was no significant difference in the amount of narcotic use, transfusion requirements, or hospital stay between the two groups. Postoperative swelling and range of motion were not consistently recorded. Twenty-eight other variables also examined not significant. Based on these results, we cannot recommend continuous cold therapy or justify the extra expense for all patients who undergo TKA.

Color duplex Doppler ultrasound scanning for detection of deep venous thrombosis in total knee and hip arthroplasty patients. Incidence, location, and diagnostic accuracy compared with ascending venography.

Ninety-nine patients undergoing total hip arthroplasty (THA) or total knee arthroplasty (TKA) were prospectively studied for deep venous thrombosis (DVT) of the lower extremity. Eighty-three hips in 42 THA patients and 107 knees in 57 TKA patients were studied with noninvasive color duplex Doppler ultrasound flow scanning and ascending venography 3-9 days after surgery. In all patients, surveillance studies were performed within 24 hours. The ultrasonographer and radiologist were blinded to the study. The incidence of DVT was significantly greater following TKA (61%) than THA (17%) (P < .001). After TKA, significantly more DVT was found in the ipsilateral (32 of 57 patients) versus contralateral knees (3 of 50 patients), and more thrombi were located below the knee (34 of 107 knees) than above the knee (1 of 107 knees) (P < .001). More thrombi were found in the contralateral limb after THA (5 of 41 patients vs 3 of 42 patients), but this was not significant. Two patients developed nonfatal pulmonary emboli. The sensitivity of color flow scanning was relatively poor initially (67% of above-knee patients and 57% of below-knee patients), but improved in the last 50 patients (100% of above-knee patients and 79% of below-knee patients). Negative predictive values exceeded 90% in the THA group and 87% in the TKA group. Positive predictive values ranged from 89 to 100%. Specificity was always above 96%. Longitudinal ultrasound scanning with the newer Quantum 2000 angiodynograph (Issaquah, WA) provided the best image quality.(ABSTRACT TRUNCATED AT 250 WORDS)

Color-flow duplex scanning for the surveillance and diagnosis of acute deep venous thrombosis.

Compared with conventional duplex imaging, color-flow scanning facilitates the identification of veins (especially below the knee), decreases the need to assess Doppler flow patterns and venous compressibility, and allows veins to be surveyed longitudinally. These advantages translate into a less demanding and time-consuming examination. This study was designed to determine the accuracy of color-flow scanning for detecting acute deep venous thrombosis in patients in whom the diagnosis is clinically suspected and in asymptomatic patients at high risk for developing postoperative deep venous thrombosis. The diagnostic group included 77 limbs of 75 patients, and the surveillance group included 190 limbs of 99 patients undergoing total hip or knee replacement. All patients were prospectively examined with color-flow scanning and phlebography. In the diagnostic group, the incidence of thrombi in below-knee veins (47%) was approximately equal to that in above-knee veins (43%); but in the surveillance group, the incidence of thrombi in below-knee veins (41%) far exceeded that in veins above the-knee (3%). Nonocclusive clots and clots isolated to a single venous segment were more common in the surveillance group. In symptomatic patients, color-flow scanning was 100% sensitive and 98% specific above the knee and 94% sensitive and 75% specific below the knee. In the surveillance group, color-flow scanning was significantly (p less than 0.001) less sensitive (55%) for detecting thrombi, 93% of which were confined to the tibioperoneal veins. Negative predictive values were 100% and 88% for the diagnostic and surveillance limbs, respectively. Positive predictive values were 80% for the diagnostic limbs and 89% for the surveillance limbs. Color-flow scanning effectively excludes above-knee deep venous thrombosis in symptomatic patients and asymptomatic high-risk patients and predicts the presence of above-knee thrombi in patients in the diagnostic group with reasonable accuracy (97%). We conclude that color-flow scanning is as accurate as conventional duplex imaging and, because of its advantages, is the noninvasive method of choice for evaluating patients with suspected deep venous thrombosis. Its role in the surveillance of patients at high risk remains to be determined and awaits further clinical evaluation.

Myocardial insulin resistance during acute endotoxin shock in dogs.

Myocardial insulin responsiveness was determined in open-chest pentobarbital sodium-anesthetized dogs before and after endotoxin administration. Animals were instrumented to measure mean arterial blood pressure (MABP), heart rate (HR), and coronary blood flow. Myocardial glucose uptake and myocardial oxygen uptake (MVO2) were determined during a basal control period and after a hyperinsulinemic-euglycemic clamp procedure over a wide range of insulin concentrations. The clamp was accomplished by intravenously infusing insulin (0-4000 mU/min) and 20% glucose in sufficient amounts to maintain arterial glucose concentrations within 5 mg/dl of the control value. In a separate series of experiments, myocardial insulin responsiveness was determined by use of a single dose of insulin (4000 mU/min). This was done to determine whether antecedent insulin infusions during the sequential clamp procedure would affect the responsiveness of the heart. In control experiments, myocardial glucose uptake increased without any changes in HR, MVO2, or MABP. Maximum myocardial glucose uptake occurred at an insulin infusion rate between 400 and 4000 mU/min. A single concentration of insulin resulted in similar increases in myocardial glucose uptake as with the sequential clamp protocol. Acute endotoxin shock was induced by bolus injection of 1 mg/kg Salmonella typhimurium endotoxin (Difco Labs, Detroit, MI). One hour after administration of endotoxin, basal myocardial glucose uptake was decreased compared with the control animals. After 1 h of endotoxin shock, the heart was refractory to all concentrations of insulin, suggesting the site for altered insulin response was being mediated by a postreceptor mechanism.

Myocardial depression during acute pancreatitis: fact or fiction?

Clinical and experimental evidence suggests that myocardial depression occurs during severe pancreatitis, but this evidence is derived from techniques that are not optimal for assessing myocardial contractility (e.g., rate of rise in ventricular pressure [dP/dt]). The slope of the left ventricular (LV) and systolic pressure dimension relationship (Ees), a better indicator of myocardial function, has not been measured in pancreatitis. Ten mongrel dogs underwent surgical instrumentation to monitor systemic arterial and LV pressure, cardiac output, LV dP/dt, and anterior LV wall thickness. End of systole was defined by the peak negative dP/dt. The end-systolic points used to calculate Ees were obtained by aortic and vena caval occlusion. After surgical recovery, pancreatitis was induced via cannulation of the pancreatic duct and injection of autologous bile (1 ml/kg) at 200 mm Hg perfusion pressure. All measurements were taken during a control period and daily after pancreatitis was induced. Pancreatitis was confirmed by a significant increase in serum amylase throughout the study and by autopsy finding of hemorrhagic necrosis. Ees was increased throughout the experimental protocol (1 to 7 days) (p less than 0.05). Myocardial performance as assessed by Ees was significantly increased and myocardial depression did not occur in untreated, conscious dogs with severe pancreatitis. Peak positive LV dP/dt was a poor index of contractility during pancreatitis since it decreased while myocardial contractility was increased. Cardiac depression in pancreatitis noted in other reports was likely due to decreased preload and not to intrinsic cardiac dysfunction.