[Preoperative hemodilution by erythrocytapheresis with homologous blood saving in total hip arthroplasty]. / Contribution de l'hémodilution préopératoire par érythrophérèse à l'épargne de sang homologue au cours de l'arthroplastie totale de hanche.

OBJECTIVES: To compare three techniques for decreasing homologous blood requirements in total hip arthroplasty (THA), including preoperative autologous donation (PAD), preoperative acute normovolaemic haemodilution with erythrocytapheresis (erythro) and intraoperative normovolaemic haemodilution (haemo). STUDY DESIGN: Prospective clinical trial. PATIENTS: The study included 45 patients scheduled for THA, under general anaesthesia and operated on by the same surgeon. The patients were allocated into three groups of 15 each. METHODS: Blood loss was assessed, during surgical procedure, by the weight of sponges and, the amount of blood collected in the suction bottles during and after surgery. The haemoglobin concentration was measured at the time of preoperative assessement (d-30), just prior to surgery (d-1), in the recovery room (d+3h), and 1, 3, and 8 days later (d8). The transfusion end-point in the three groups was to obtain a haemoglobin concentration of 100 g.L-1 from d+3h until d8. Every pack of red blood cells transfused was weighed and its haematocrit assessed to determine the accurate volume of red blood cells. RESULTS: In the three groups haemoglobin concentration was similar from d+3h until d8. In the PAD group, no patient required homologous blood transfusion. There was no significant difference between the two other groups in the mean volume of homologous red blood cells required (308 +/- 197 mL in erythro group and 331 +/- 202 mL in the haemo group, respectively). The intraoperative blood loss was significantly higher (P = 0.001) in the erythro group: 914 +/- 305 mL vs 665 +/- 263 in the PAD group and 512 +/- 146 mL in the haemo group, respectively. There was an inverse correlation between haematocrit at d-1 and intraoperative bleeding (r = -0.7) (P = 0.0001). The distribution of the points was fitted as an exponential curve. CONCLUSIONS: In THA, PAD is obviously the best technique to avoid homologous blood transfusion. However, when PAD is not feasible, removal of blood prior to surgery does not decrease requirements of homologous blood, as intraoperative blood loss is higher. Our results strongly question the use of major haemodilution during a surgical procedure exposing a major blood loss.

Shivering threshold during spinal anesthesia is reduced in elderly patients.

BACKGROUND: Both accidental and perioperative hypothermia are common in the elderly. The elderly are at risk because their responses to hypothermia may be delayed or less efficient than in those of younger subjects. For example, the vasoconstriction threshold during isoflurane anesthesia is approximately 1 degree C less in elderly than younger patients. However, the extent to which other cold defenses are impaired in the elderly remains unclear, especially in those older than 80 yr. Operations suitable for spinal anesthesia provided an opportunity to quantify shivering thresholds in patients of varying ages. Accordingly, the hypothesis that the shivering threshold is reduced as a function of age during spinal anesthesia was tested. METHODS: Twenty-eight ASA Physical Status 1-3 patients undergoing lower extremity orthopedic procedures were studied. Spinal anesthesia was induced without preanesthetic medication, using bupivacaine sufficient to produce a dermatomal level near T9. Electrocardiogram signals were recorded at 10-min intervals. Subsequently, an observer masked to patient age and core temperature identified the onset of sustained electromyographic artifact consistent with shivering. The tympanic membrane temperature triggering shivering identified the threshold. RESULTS: Three patients did not shiver at minimum core temperatures exceeding 36.2 degrees C. Fifteen patients aged < 80 yr (58 +/- 10 yr) shivered at 36.1 +/- 0.6 degrees C; in contrast, ten patients aged > or = 80 yr (89 +/- 7 yr) shivered at a significantly lower mean temperature, 35.2 +/- 0.7 degrees C (P = 0.002). The shivering thresholds in seven of the ten patients older than 80 yr was less than 35.5 degrees C, whereas the threshold equaled or exceeded this value in all younger patients (P = 0.0002). CONCLUSIONS: Age-dependent inhibition of autonomic thermoregulatory control in the elderly might be expected to result in hypothermia. That it usually does not suggests that behavioral regulation (e.g., increasing ambient temperature, dressing warmly) compensates for impaired autonomic control. Elderly patients undergoing spinal anesthesia, however, may be especially at risk of hypothermia because low core temperatures may not trigger protective autonomic responses. Furthermore, hypothermia in the elderly given regional anesthesia may not be perceived by the patient (who typically feels less cold after induction of the block), or by the anesthesiologist (who does not observe shivering). Consequently, temperature monitoring and management usually is indicated in these patients.

Nifedipine and intraoperative core body temperature in humans.

BACKGROUND: Initial anesthetic-induced hypothermia results largely from core-to-peripheral redistribution of heat. Nifedipine administration may minimize hypothermia by inducing vasodilation well before induction of anesthesia. Although vasodilation would redistribute heat to peripheral tissues, thermoregulatory responses would maintain core temperature. After equilibration, the patient would be left vasodilated, with a small core-to-peripheral temperature gradient. Minimal redistribution hypothermia may accompany subsequent induction of anesthesia, because heat flow requires a temperature gradient. In contrast, similar vasodilation concurrent with anesthetic-induced vasodilation may augment redistribution hypothermia. Accordingly, the authors tested the hypothesis that nifedipine treatment for 12 h before surgery would minimize intraoperative redistribution hypothermia, whereas nifedipine treatment immediately before induction of anesthesia would aggravate hypothermia. METHODS: Patients undergoing hip arthroplasty were randomly assigned to: (1) 20 mg long-acting nifedipine orally 12 h before surgery, and 10 mg sublingually 1.5 h before surgery (n = 10); (2) nifedipine 10 mg sublingually just before induction of anesthesia (n = 10); and (3) no nifedipine (control, n = 10). Anesthesia was maintained with isoflurane and 60% nitrous oxide. Administered intravenous fluids were heated, but the patients were not otherwise actively warmed. RESULTS: Core temperature decreased 0.8 degree C in the first hour of surgery in the patients given nifedipine the night before and the morning of surgery, which was significantly less than in the control group (1.7 degree C in the first hour). In contrast, core temperature decreased 2.0 degrees C in the first hour of surgery in the patients given nifedipine immediately before induction of anesthesia. During the subsequent 70-130 min of anesthesia, core temperature decreased at roughly comparable rates in each group. After 130 min of anesthesia, core temperature in the two nifedipine-treated groups differed by 1.6 degrees C, and the temperatures in all three groups differed significantly. CONCLUSIONS: Vasodilation induced by nifedipine well before induction of anesthesia minimized redistribution hypothermia, presumably by decreasing the core-to-peripheral tissue temperature gradient. In contrast, redistribution hypothermia was aggravated by administration of the same drug immediately before induction of anesthesia. Drug-induced modulation of vascular tone thus produces clinically important alterations in intraoperative core temperature.

[Effects of nifedipine premedication on peroperative hypothermia]. / Effets de la nifédipine en prémédication sur l'hypothermie peropératoire.

The intraoperative time-course of core temperature in patients premedicated with nifedipine (n = 30) was compared to that of control patients (n = 30). Distal oesophageal temperature (TCORE) was recorded every five minutes during total hip replacement in 60 adults ranked ASA 1 to 2. Patients in the control group were only premedicated with 100 mg of oral hydroxyzine. The treatment group consisted of 30 patients taking nifedipine for blood pressure control or coronary insufficiency. They were given 10 mg sublingual nifedipine as well as the hydroxyzine premedication. Anaesthesia was induced with thiopentone, fentanyl and vecuronium, and maintained with nitrous oxide in oxygen and halothane in a semi-closed circuit. The slopes of the time-course for TCORE were established for each patient, using two linear regressions, between 0 and 0.5 h and from 1 to 2 h. The two groups did not differ in age, weight, ambient temperature, blood pressure, heart rate, and volume of unwarmed blood transfused. TCORE differed significantly from the 25th minute on until the end of the study period. Contrary to all expectation the TCORE at 2 h was higher in the nifedipine group (34.85 +/- 0.09 degrees C) than in the control group (34.01 +/- 0.14 degrees C, p < 0.001). TCORE decreased more rapidly in the control group during the first study interval (0 to 0.5 h), -1.50 +/- 0.60 degrees C.h-1 vs -2.34 +/- 1.02 degrees C.h-1 (p < 0.001). The second slopes did not differ particularly (-0.96 +/- 1.32 degrees C.h-1 vs -0.90 +/- 0.42 degrees C.h-1 respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

[Comparison of effects of Elohes and albumin on hemostasis in orthopedic surgery]. / Comparaison des effets de l'Elohes et de l'albumine sur l'hémostase en chirurgie orthopédique.

A prospective study was carried out to determine the effects of Elohes, a low molecular weight hydroxyethylstarch, on haemostasis. Sixteen patients due to undergo total hip replacement were randomly assigned to one of two groups: group A, who were to receive up to 21 of 4% albumin to replace blood loss, and group E, 1.51 of Elohes. Patients were then given concentrated red cell packs (RCP) and lactated Ringer's solution so as to have a haematocrit value of 30%, up to the fifth postoperative day. The amount of blood lost intraoperatively was calculated by weighing the swabs and measuring the volume aspirated. Haemostasis was investigated on the eve of surgery, 3 hours afterwards, and then every second day (days 1, 3 and 5). Total blood loss and the number of RCP transfused were similar in both groups: 1,517 +/- 425 ml and 3.5 RCP, and 1,428 +/- 250 ml and 3.25 RCP in groups A and E respectively. Blood albumin concentrations fell in group E as expected, the starch diluting blood proteins. Bleeding time (Simplate), activated partial thromboplastin time, prothrombin time changed in the same way in both groups throughout the study period after infusion of either Elohes or albumin. The concentrations in factors II, V, VII and X fell by 30% three hours after surgery. Values returned to normal between days 1 and 3, the concentrations of some factors rising to values greater than preoperative values because of the postoperative inflammatory process (fibrinogen, factor VIII von Willebrand). However, there were no significant differences between the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)