Robert Mineo

The effect of intravenous fixed-dose heparin during total hip arthroplasty on the incidence of deep-vein thrombosis. A randomized, double-blind trial in patients operated on with epidural anesthesia and controlled hypotension

Heparin was given in fixed doses intravenously during unilateral primary total hip-replacement operations in a prospective, double-blind trial to assess the effect on the incidence of deep-vein thrombosis. One hundred and fifty patients were randomly assigned to one of two groups before the operation. Twenty-four patients were excluded from the study, leaving 126 patients. Group I consisted of sixty-six patients who received saline solution intravenously, and Group II comprised sixty patients who received heparin. All patients had epidural anesthesia with controlled hypotension. Fixed doses of heparin were administered five minutes before the operative incision was made and every thirty minutes throughout the operation. Mean arterial pressures were maintained at between fifty and sixty millimeters of mercury in all patients. Ascending venography was done on the seventh day after the operation. The incidence of deep-vein thrombosis was 24 per cent (sixteen of sixty-six patients) in Group I and 8 per cent (five of sixty patients) in Group II; the difference is significant (p = 0.03). The intraoperative loss of blood averaged 220 +/- 79 milliliters in Group I compared with 269 +/- 109 milliliters in Group II. An average of less than one unit of blood was transfused for each patient in each group. Postoperatively, there was no difference between the groups with regard to the amount of drainage that was collected in a Hemovac device or the values for hematocrit.

Deliberate hypotensive epidural anesthesia for patients with normal and low cardiac output.

The use of hypotensive anesthesia is contraindicated in patients with ventricular dysfunction, even though afterload reduction often improves ventricular performance. The purpose of this study was to prospectively assess systemic hemodynamic responses to deliberate hypotension with epidural anesthesia in patients with chronic left ventricular dysfunction. Hemodynamic measurements were performed in 29 patients undergoing total hip arthroplasty under deliberate hypotensive epidural anesthesia using low-dose intravenous epinephrine infusion to maintain mean arterial pressure (MAP) at 50-60 mm Hg. Intraoperative MAP decreased from 100 +/- 16 to 56 +/- 9 mm Hg by 30 min after epidural injection (P < 0.0005). Concurrently, cardiac index (CI) increased from a preanesthetic baseline value of 2.9 +/- 0.5 to 3.3 +/- 0.9 L.min-1.m-2 at 30 min (P < 0.005) after epidural injection and stroke volume index (SVI) increased from 41 +/- 8 to 50 +/- 14 mL.beat-1.m-2 30 min after epidural injection (P < 0.005). Heart rate and central venous and pulmonary artery diastolic pressures were maintained under hypotension with epidural anesthesia in all patients. During deliberate hypotension with epidural anesthesia, patients with a history of congestive heart failure or low preanesthetic CI (< or = 2.5 L.kg-1.m-2) increased their CI and SVI into the normal range. There were no significant perioperative complications in either of these groups. Hypotensive epidural anesthesia can be used successfully in patients with low cardiac output from ventricular dysfunction undergoing total hip arthroplasty.

Complications after total hip replacement. The contralateral limb.

Six patients who had a total hip replacement, as well as a trochanteric osteotomy, while they were in the lateral decubitus position had complications involving the contralateral side. The complications included transient paresthesias, massive swelling of the thigh with myonecrosis, acute renal failure secondary to myoglobinuria, and arterial insufficiency that resulted in a below-the-knee amputation. In order to elucidate the causes of the complications, the external pressure of the contralateral femoral triangle and the blood flow to the contralateral foot were monitored intraoperatively in seventeen patients. The results supported the postulate that pressure at the groin is increased intraoperatively and that this can cause vascular compromise. Other proposed causes of the complications were pre-existing vascular disease, obesity, the lateral decubitus position of the patient on the operating table, and the use of hypotensive anesthesia. We found several techniques that may minimize complications in the contralateral limb during operations on the hip.

Acute exacerbation of carpal tunnel syndrome after radial artery cannulation.

Acute carpal tunnel syndrome that follows radial artery cannulation has been described. To determine the incidence and predisposing factors, we prospectively studied 151 patients who had perioperative radial artery cannulation. Postoperatively 9 of the 151 patients had symptoms of carpal tunnel syndrome with positive Phalen and Tinel signs on the side on which the radial artery catheter had been inserted. Eight of 12 patients with a prior history of carpal tunnel syndrome had acute exacerbation of symptoms postoperatively. By contrast, only 1 of 139 patients with no prior history of the disorder had symptoms. Fourteen patients had multiple arterial artery punctures or perforations of the posterior wall of the radial artery. In three of these, postoperative symptoms of carpal tunnel syndrome developed but did not reach statistical significance. The only patient with postoperative acute carpal tunnel syndrome but no prior history of the syndrome had multiple arterial punctures. The use of perioperative anticoagulation, the use of wrist-extension splints, and the duration of radial artery cannulation did not influence acute exacerbation of carpal tunnel syndrome. Patients with a prior history of carpal tunnel syndrome are at increased risk of recurrent symptoms after radial artery cannulation. We found no statistically significant relationship between traumatic cannulations and the development of symptoms of carpal tunnel syndrome.

Intraoperative adjusted-dose heparin thromboembolic prophylaxis in primary total hip arthroplasty.

Intraoperative, fixed, intermittent, low-dose intravenous heparin prophylaxis has been reported to significantly reduce the incidence of thromboembolic disease from 24.3% to 8.3% after primary total hip arthroplasty (THA). This study examined the potential efficacy of adjusted-dose intraoperative heparin administration, keeping the activated clotting time at 30%-50% greater than normal. It was hypothesized that prolongation of clotting parameters in a uniform manner would further decrease the incidence of thromboembolic disease postoperatively. Sixty-one patients completed the protocol. The overall incidence of thromboembolic disease was 9.8%. Five patients had a positive postoperative venogram: four in the calf and one in the proximal deep thigh vein. One patient had a symptomatic nonfatal pulmonary embolus diagnosed by ventilation-perfusion scan. There were no complications related to heparin administration. This approach was therefore equally as effective as the fixed-dose regimen, and it further confirmed the efficacy and safety of an intraoperative heparin prophylaxis regimen. The extra efforts required to maintain a constant intraoperative level of anticoagulation did not prove advantageous over the simpler, fixed-dose regimen in reducing the incidence of thromboembolic disease after primary THA.

Single versus staged epidural injections of 0.75% bupivacaine : pharmacokinetic and pharmacodynamic effects

Epidural anesthesia may be performed as a single injection or by staged doses. Thirty patients undergoing primary total hip replacement were randomly assigned to have epidural anesthesia using a single injection or a staged technique with 25 mL of 0.75% bupivacaine. Arterial plasma bupivacaine concentrations were significantly higher in the single injection group for the first 15 min but were not significantly different thereafter. Peak bupivacaine concentrations did not differ significantly between groups, but the time to achieve the peak concentration was delayed by staging injections (P = 0.001). Hemodynamic effects were similar between groups. Resolution of thoracic sensory block through T12 and duration of motor block measured by Bromage scale were both significantly longer in the staged injection group (P < 0.01). The method of epidural injection may affect resolution of neural block and the time to reach peak arterial plasma concentration of local anesthetic.