Ch. Pieter Henny

The clinical importance of erythrocyte deformability, a hemorrheological parameter.

SummaryHemorrheology, the science of the flow behavior of blood, has become increasingly important in clinical situations. The rheology of blood is dependent on its viscosity, which in turn is influenced by plasma viscosity, hematocrit, erythrocyte aggregation, and erythrocyte deformability. In recent years it has become apparent that the shape and elasticity of erythrocytes may be important in explaining the etiology of certain pathological situations. Thus, clinicians have become increasingly interested in hemorrheology in general and erythrocyte deformability in particular. In the course of time, many clinical studies have been performed, but no concise review has thus far been published. This article encompasses a review of the clinically based literature on this subject.

Heart, kidney, and intestine have different tolerances for anemia

Organ systems do not respond uniformly to changes in systemic oxygen delivery because of global and local redistributive mechanisms. We hypothesized that progressive hemodilution would evoke a different response in the microvascular oxygenation of the heart compared with kidney and gut. To evaluate this hypothesis, we studied the effect of stepwise isovolemic hemodilution on systemic hemodynamic and oxygenation parameters as well as the relation between systemic hematocrit (Ht) and microvascular PO(2) (microPO(2)) in heart, kidney, and intestines in an anesthetized and mechanically ventilated rat model. Baseline conditions were similar in the hemodilution group and in the control group. In the hemodilution group, Ht was diminished from 46.6 +/- 3.8% to 7.0 +/- 1.8% [mean +/- standard deviation (SD)]. This group had no effect on measured hemodynamics; only when Ht fell below 10% did blood pressure start to decrease. The microPO(2) values in heart, kidney, and intestines did not respond uniformly. Renal microPO(2) (56 +/- 10 mm Hg at baseline) started to decrease at a Ht of 38.5 +/- 8.6%, whereas intestinal microPO(2) (59 +/- 6 mm Hg at baseline) did not start to decrease until Ht reached 17.4 +/- 7.1%. Finally, cardiac microPO(2) (40 +/- 6 mm Hg at baseline) decreased only in the ultimate stage of the experiment at Ht of 8.7 +/- 3.5%. Based on these observations, we conclude that the regulation of microvascular oxygenation during progressive anemia is specific for each organ system. The relation between these observations and organ function and damage needs to be determined.

Effects of interpleurally administered bupivacaine 0.5% on opioid analgesic requirements and endocrine response during and after cholecystectomy: a randomized double‐blind controlled study

In 30 patients undergoing cholecystectomy, a randomized double‐blind saline‐controlled study was performed using inaterpleural 0.5% bupivacaine with or without epinephrine (5 μg ml‐1) in combination with 0.8d̀· halothane inspired concentration in oxygen. The aim of the study was to investigate whether interpleural 0.5% bupivacaine could decrease the intraoperative opioid requirements and attenuate the metabolic endocrine response to surgical stress. Patients were randomly allocated to one of three groups: Group 1: 0.5d̀· bupivacaine; Group 2: 0.5% bupivacaine with epinephrine (5 μg ml‐1); and Group 3: saline. The interpleural catheter was inserted after induction of anesthesia in the spontaneously breathing patient. The study drug was injected 30 min prior to surgery. Peak plasma bupivacaine concentrations in the respective groups were 1.30 X 0.78 and 1.16 X 0.48 μ X ml‐1. In all patients concentrations were below suggested convulsive level. Two patients in Group 1 and two in Group 2 required intraoperative fentanyl (0.1 mg each). In contrast, eight patients in the saline group received an average of 0.21 mg (range 0.1 X 0.4 mg) fentanyl (P <0.05). Postoperatively, a second dose of the study drug was given. Subsequently, pain was assessed using a visual analog score and a verbal rating scale. Pain scores decreased significantly 30 min after the interpleural injection in both bupivacaine groups and remained unchanged in the saline group (P <0.05). Pain management by means of interpleural bupivacaine was successful in 17 of the 20 patients. In the saline group seven out of ten patients needed additional analgesics (P <0.05). Cortisol levels increased in response to surgery in all groups: maximum levels in Groups 1, 2 and 3 were: 1.09 X 0.29, 1.11 X 0.20 and 1.19 X 0.16 μol X 1‐1, respectively. Plasma glucose concentrations increased significantly in all groups: maximum levels in Groups 1, 2 and 3 were: 7.6 X 1.3, 7.3 X 1.7 and 8.3 X 1.7 mmol X 1‐1, respectively. The results of this study indicate that painful surgical stimuli can be attenuated by interpleural administration of 0.5% bupivacaine. The metabolic endocrine response, however, remained unaffected.

Differences in peripheral arterial and venous hemorheologic parameters

Abstract To evaluate the comparability of hemorheologic parameters in arterial and venous blood, we measured hematocrit, whole blood viscosity, plasma viscosity, erythrocyte deformability, erythrocyte aggregation, and erythrocyte indices in both arterial and venous blood from 20 consecutive patients scheduled for coronary artery surgery and/or valve replacement surgery. Hematocrit, whole blood viscosity at three shear rates (0.05 s–1, 0.5 s–1, and 70 s–1), plasma viscosity, and erythrocyte aggregation factor were statistically significantly higher in venous blood than in arterial blood. The differences may be explained by the difference in hematocrit. Erythrocyte deformability did not differ significantly. With the availability of more precise rheological measurement techniques, differences such as those encountered in this study may be of importance in clinical studies. It is concluded that arterial and venous blood samples are not entirely rheologically comparable.

The effects of propofol compared to high-dose fentanyl anesthesia on rheologic parameters in coronary artery surgery

Propofol has previously been found to decrease hematocrit values. Because hematocrit is an important determinant of blood viscosity, lower hematocrits may cause a decrease in blood viscosity, improving blood flow and oxygen delivery. This phenomenon may be beneficial in certain intraoperative situations. To study the influence of two anesthetic techniques on a variety of rheologic parameters, 32 patients scheduled for coronary artery bypass grafting (CABG) were divided into two groups. Group I (n = 18) was induced with high-dose fentanyl anesthesia (100 micrograms/kg), and group II (n = 16) with a combination of propofol and fentanyl anesthesia (1 to 1.5 mg/kg and 35 to 50 micrograms/kg, respectively). Maintenance anesthesia continued with infusions of the same drugs. Blood and plasma viscosity, hematocrit, erythrocyte aggregation factor, and erythrocyte deformability were measured preoperatively, intraoperatively, and up to 48 hours postoperatively. Whole blood viscosity was corrected to a standard hematocrit of 0.45. The two groups were comparable with respect to age, bypass duration, blood loss, urine output, transfusions, and fluid management. Erythrocyte deformability did not decrease during or after cardiopulmonary bypass (CPB). In both groups, hematocrit and blood and plasma were decreased significantly during and after CPB (P < 0.01) and returned to baseline levels 48 hours after surgery. After induction and before CPB, blood viscosity was only decreased in group II. However, the corrected blood viscosity was significantly elevated at all shear rates in group II compared to group I at 24 and 48 hours postoperatively (P < 0.01). In group II at these sampling times, this parameter was also significantly elevated compared to preoperative values.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytomegalovirus infection in the pregnant woman

Cytomegaloviruses (CMV) commonly infect man but overt disease only occurs in few patients; in the vast majority the infection is subclinical. We report on a HIV-negative pregnant woman. She suffered from a life-threatening ulcerating colitis due to CMV infection for which laparotomy was indicated. The case history is presented and suggestions are given for the surgical treatment of gastrointestinal complications such as haemorrhage, toxic colitis and perforation. Although CMV disease usually occurs in immunocompromised patients such as AIDS patients and transplant recipients, one should always keep the possibility of CMV infection in mind. The gastrointestinal tract is one of the sites of infection where the colon and terminal ileum are most frequently involved in complications such as bleeding and perforation. Gastrointestinal complications of CMV infection, although rare, can be life threatening and often require extensive surgery.

Are there simple measures to reduce the risk of HIV infection through blood transfusion in a Zambian district hospital

Summary objective  To quantify the potential impact of simple measures to reduce the risk of iatrogenic HIV infection through blood transfusion in a Zambian district hospital.

Red Blood Cell Velocity in Nailfold Capillaries during Hyperbaric Oxygenation

Microcirculatory hemodynamics of the skin during hyperbaric oxygenation were assessed by determination of nailfold capillary red blood cell velocity (Vrbc). Under hyperbaric conditions a continuous increase in Vrbc was found. Control values, 0.43 +/- 0.12 mm. sec-1 (mean +/- sem), were significantly (P < 0.05) lower compared with Vrbc at the end of hyperbaric oxygenation (0.62 +/- 0.16 mm.sec-1).

POSSIBILITIES TO DECREASE THE NEED FOR ALLOGENEIC BLOOD TRANSFUSION DURING SURGERY

Several risks are associated with transfusion of allogeneic blood and blood products. The risk of alloimmunisation is well known. Transmission of viral infections by allogeneic blood transfusion draw the attention. In addition, it is suggested that transfusion of allogeneic blood exerts a long-term immunosuppressive action with probably increased tumor growth and more post-operative infections. In many retrospective studies decreased survival is associated with transfusions. [ 11. However prospective studies including more patients are needed to evaluate the clinical importance of changes in the immune system. In human and in animal experiments depression of Natural Killer cell activity is longlasting while changes in lymphocytes subpopulations and in macrophage function are clearly demonstrated. [2,3]. Transfusion with donor blood may be diminished by predeposited autologous blood, intra-operative autotransfusion with a cell-saver and hemodilution techniques. Furthermore phase I, II studies are in progress, using artificial oxygencarriers like fluorocarbons and stroma free hemoglobin (Hb) solutions.

Effects of isovolemic hemodilution on microcirculatory parameters and skeletal muscle oxygenation during anaesthesia.

Isovolemic hemodilution shortly before starting a major surgical procedure has been developed to reduce the risks of homologous bloodtransfusions1,2.