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Print version ISSN 0034-7094
Rev. Bras. Anestesiol. vol.55 no.1 Campinas Jan./Feb. 2005
Postanesthetic hematocrit changes in orthognathic surgery*
Alteraciones pos-anestésicas del hematócrito en cirugías ortognáticas
Tailur Alberto Grando, TSA, M.D.I; Edela Puricelli, M.D.II; Airton Bagatini, TSA, M.D.III; Cláudio Roberto Gomes, TSA, M.D.IV; Carolina Guerra Baião, M.D.V; Deise Ponzoni, M.D.VI
IResponsável pelo CET/SBA do
SANE. Anestesiologista do Instituto de Cardiologia/Fundação Universitária
de Cardiologia de Porto Alegre
IIDoutora pela Universidade de Düsseldorf, Alemanha. Chefe da Unidade de Cirurgia e Traumatologia Bucomaxilofacial do HCPA/FO/UFRGS. Chefe do Serviço de Cirurgia e Traumatologia Bucomaxilofacial do Complexo Hospitalar Santa Casa de Porto Alegre
IIICo-Responsável pelo CET/SBA do SANE. Membro do Comitê de Anestesia Venosa da SBA 2003-2005. Anestesiologista do Instituto de Cardiologia/Fundação Universitária de Cardiologia de Porto Alegre
IV Instrutor do CET/SBA do SANE. Anestesiologista do Instituto de Cardiologia/Fundação Universitária de Cardiologia de Porto Alegre
VMédica Estagiária do 1º ano CET/SBA do SANE
VIMestre e Doutora em Cirurgia e Traumatologia Bucomaxilofacial do HCPA/FO/UFRGS; Especialista em Disfunção da Articulação Temporo-Mandibular
BACKGROUND AND OBJECTIVES: Blood transfusions
have been heavily questioned due to the increased number of transfusion-transmitted
diseases This study aimed at evaluating perioperative blood loss and hematocrit
recovery in 14 days, in patients submitted to orthognathic surgery under induced
hypotensive anesthesia, with three different volume replacement techniques.
METHODS: This was a prospective study of consecutive patients submitted to orthognathic surgery in the period August 1985 to July 2003. Patients were distributed in three groups: group I with pre-operative self-donation of blood 7 days before surgery; group II with intraoperative self-donation; and group III with normovolemic hemodilution. Pre-medication, induction, maintenance, drugs and monitoring were standardized. Patients were submitted to induced hypotensive general anesthesia. The following data were evaluated: blood loss, anesthetic length, systolic, diastolic and mean blood pressure, heart rate, hematocrit and hemoglobin at pre-induction, 60 hours after the first sample and at 14th the postoperative day, as well as perioperative complications.
RESULTS: Blood loss was 1340.03 ± 427.97 in group I; 1098.08 ± 429.30 in group II; and 1044.71 ± 526.56 in group III, with statistical significance in group I as compared to groups II and III. There was significant decrease in pre-induction hemoglobin as compared to 60 hours and 83% hematocrit recovery in 14 days.
CONCLUSIONS: Perioperative blood loss for all groups was high, with need for allogeneic blood transfusion. Virtually all patients have tolerated blood loss since in general they were young patients, physical status ASA I and II without associated diseases. Hematocrit has not returned to preoperative values after 14 days.
Key words: ANESTHETIC TECHNIQUES, General: controlled hypotension; MEASUREMENT TECHNIQUES: hematocrit; SURGERY, Orthognatic
JUSTIFICATIVA Y OBJETIVOS: Con el aumento
de enfermedades transmisibles a través de las transfusiones sanguíneas,
sus indicaciones están siendo muy cuestionadas. Los objetivos de este trabajo
son evaluar la pérdida sanguínea peri-operatoria, y la recuperación
del hematócrito después de 14 días, en pacientes sometidos a
la cirugía ortognática, realizada bajo anestesia general e hipotensión
controlada, con tres diferentes técnicas de reposición volemica.
MÉTODO: Fue realizado un estudio prospectivo en pacientes sometidos consecutivamente a cirugía ortognática, en el período entre agosto de 1985 a julio de 2003. Los pacientes fueron divididos en tres grupos; grupo I, con autodonación previa de 7 días; grupo II, con autodonación intra-operatoria; y grupo III, con hemodiluición normovolemica. La medicación pre-anestésica, la inducción, el mantenimiento, los fármacos y a monitorización fueron estandarizados. Los pacientes fueron sometidos a la anestesia general con hipotensión arterial inducida y controlada. Fueron analizados la pérdida sanguínea, el tiempo anestésico, la presión sistólica, diastólica y media, la frecuencia cardiaca, el hematócrito y la hemoglobina antes de la inducción anestésica, y el hematócrito y la hemoglobina después de 60 horas y 14 días del post-operatorio bien como las complicaciones peri-operatorias.
RESULTADOS: La pérdida sanguínea fue de 1340,03 ± 427,97 en el grupo I; 1098,08 ± 429,30 en el grupo II; y 1044,71 ± 526,56 en el grupo III, con diferencia estadística significativa en el grupo I con relación a los grupos II y III. Hubo disminución significativa del hemoglobina antes de la inducción de la anestesia , comparado a los resultados logrados en 60 horas, y restauración del 83% del hematócrito, en 14 días.
CONCLUSIONES: La pérdida sanguínea peri-operatoria en los tres grupos fue considerable, con mínima necesidad de transfusión de sangre alogénico. La casi totalidad de los pacientes toleró la pérdida sanguínea, pues en general eran jóvenes, estado físico ASA I y II y sin grande comorbidade asociada. El hematócrito en 14 días no recobró el valor pre-operatorio.
Since hemolytic reactions, incompatible blood transfusions and blood transfusion-transmitted diseases, especially hepatitis B and C and AIDS were recognized, transfusion indications have been heavily questioned. There is also suspicion that blood stored for more than 15 days could lead to splanchnic ischemia and poorer survival of septic transfused patients 1.
Blood transfusions are usually indicated to increase oxygen transportation and intravascular volume 2. Messmer 3 suggests that oxygen transportation could be adequately achieved with hematocrit around 20% and the American National Institute of Health, in the latest Consensus Conference, has concluded that healthy patients with hematocrit above 30% seldom need perioperative transfusions 4.
Some surgical techniques do not ligate or cauterize blood vessels due to cicatricial fibroses responsible for lower quality bone callus. Orthognathic surgeries are becoming increasingly more complex, prolonging surgery duration and forcing the anesthesiologist to use controlled hypotension, normovolemic hemodilution and pre or intraoperative self-donation of blood.
These techniques may pose risks, and cost-benefit ratio should be evaluated in a case-by-case basis. Complications are uncommon in young and healthy patients, but the risk increases in elderly patients with associated diseases.
Pre or intraoperative self-donation of blood has been used to decrease transfusion reactions and transmission of diseases. However, their widespread use has been questioned and has concomitantly increased the use of normovolemic hemodilution techniques. Final decision on the solution to replace blood losses depends on several factors, including patient's preoperative conditions, surgery type and duration. Amount of fluid should be planned to maintain blood pressure and flow 5.
After blood loss, maturation of new red cells takes approximately 12 days, and peak bone marrow production estimated by reticulocytes count is seen in 8 to 10 days.
This study aimed at evaluating perioperative blood loss and hematocrit recovery after 14 days, in patients submitted to orthognathic surgery under general anesthesia with induced hypotension and with three different volume replacement techniques 6-12.
After the Ethics Committee approval, participated in this study patients submitted to orthognathic surgery and referred by the Service of Bucco-maxillo-facial Surgery and Traumatology, Instituto Puricelli, Porto Alegre, in the period August 1985 to July 2003. Patients were distributed in three groups: Group I, preoperative self-donation of blood 7 days before surgery; Group II, self-donation right before surgery; and Group III with normovolemic hemodilution.
Preanesthetic evaluation consisted of evaluation of anesthetic-surgical risk, patient's history, and physical and lab tests. Patients were premedicated with lorazepam (2 mg) or midazolam (15 mg) the day before surgery and clonidine (5 µg.kg-1) (ceiling of 300 mg) associated to midazolam (7.5 mg) one hour before surgery. Anesthesia was induced with thiopental (3 to 5 mg.kg-1), propofol (1 to 1.5 mg.kg-1) or midazolam (0.1 mg.kg-1), fentanyl (10 µg.kg-1) and pancuronium (0.1 mg.kg-1), and was maintained with halothane or isoflurane, droperidol (0.07 mg.kg-1) and metoprolol (0.10 mg.kg-1).
Sodium nitroprusside (SNP) (0.44 µg.kg-1.min-1) would be administered if surgical field bleeding was to be decreased. Patients were nasally intubated with latex spiral tube and high volume low pressure cuff.
Ventilation was mechanically controlled with 8 to 10 mL.kg-1 tidal volume checked by arterial blood gases analysis or through capnography and oximetry. Patients remained intubated for at lest 8 hours in due postoperative period intermaxillary elastic immobilization associated to the development of edema and hematoma. Patients received oxygen through a T Ayre system in the immediate postoperative period and continuous nebulization with saline during the first 5 hours.
After this period, nebulization was applied for 20 minutes every hour. Intraoperative volume replacement was achieved with 5% glucose solution (1 mL.kg-1.h-1) with additional 1 mL.kg-1 for patients above 20 kg to replace fasting-induced losses, in a maximum period of 6 hours. Insensible and translocation losses were replaced with saline (4 mL.kg-1.h-1) and lost blood was replaced with saline (3 mL per mL lost). Hypotension was induced with SNP or other drugs (halogenate, fentanyl, beta-blocker and alpha-blocker). Anesthetic depth was maintained by varying inhalational anesthetic concentration and with fentanyl and midazolam in bolus or continuous infusion.
Systolic, diastolic and mean blood pressure were continuously monitored through left radial artery catheterization. A deep vein was catheterized by right subclavian vein puncture aiming and infusing fluids, drugs and central venous pressure measurement. Other variables were also measured: diuresis, temperature, ECG in two leads (DII and V5), heart rate, central venous pressure, pulse oximetry and capnography. All patients received 16G nasogastric tube and Foley's catheter (with exception of first 87 patients). Hemodynamic data were obtained by adequate device (Datascope Passport XG). Data were recorded for analysis in three moments: before induction, two and 4 hours after anesthetic induction.
Blood losses were evaluated by weighing gauzes and compresses, but especially by aspired volume, because surgical field irrigation is often used in these surgeries to help anatomic structures visualization. Total perioperative blood loss has considered volemia and percentage of preoperative hematocrit and that obtained 60 hours later. Patients of the three groups were evaluated, but intraoperative volume replacement was always achieved with crystalloids according to lost volume and clinical signs.
Gross' formula 13 was used to calculate admissible loss or as basis for lost volumes which, together with clinical signs, guide blood replacement.
New hematocrit count was asked 14 days after surgery to check patients' hematic recovery.
The following were considered complications: worsening of preexisting disease; extension of disease to other organs or presence of acute infection. Sequela was defined as temporary or permanent sign or symptom resulting from the anesthetic technique. Two systems were evaluated for complications before anesthesia and in the 5th postoperative day: central nervous system (consciousness, memory, motor function) and urinary system (creatinine dosage). Cardiovascular system was only intraoperatively evaluated to detect signs of myocardial ischemia and arrhythmias.
Continuous variables were described as mean and standard deviations, or median and 25-75 inter-quartile intervals. Categorical variables were described as proportions. Analysis of variance was used for continuous variables with symmetric distribution, Kruskal-Wallis test was used for asymmetric variables and Chi-square test was used for categorical variables. Critical significance level was 5%.
All groups were similar in age, height and weight, with predominance of females and physical status ASA I. Group I: 118 patients, Group II: 117 patients, and Group III: 110 patients. Demographics data are shown in table I.
Hemodynamic data are shown in table II.
Hematocrit and hemoglobin changes in all groups, related to donation moment and recovery are shown in table III. There has been statistical significant difference (p < 0.05) between groups I and II in hemoglobin values at 60 hours, and between groups I and II in preanesthetic hemoglobin values.
There were no postoperative sequelae. Complications were: vomiting and arrhythmias.
Incidence of vomiting was 39% being more common among females (44.9%) as compared to males (29.5%). Incidence of arrhythmias was 1.4%. Observed arrhythmias were: nodal rhythm in two cases, sinusal bradycardia in two cases and ventricular extrasystole in one case. Blood loss has been 1340.03 mL ± 427.97 mL in Group I; 1098.08 mL ± 429.30 mL in Group II; and 1044.71 mL ± 526.56 mL in Group III with statistical significant difference (p <0,05) of Group I as compared to Groups II and III. Five patients received postoperative allogeneic transfusion. Events influencing the decision of transfusing patient in the postoperative period were: congenital ictiosis worsened by surgical stress (one patient), formation of false urethral pathway by vesical catheter (one patient), postural hypotension (one patient), vomiting lasting for 4 days (one patient in psychiatric treatment) and pneumonia in the 10th postoperative day after hospital discharge (one patient).
Most patients were extubated and had their gastric, vesical, arterial and peripheral venous catheters removed the next morning.
Blood replacement objective is to maintain oxygen supply to tissues, and blood volume. Volume-by-volume blood replacement is not a current concept due to the high risk of infection, especially hepatitis B and C and HIV, in addition to high costs 14-18.
The increase of allogeneic blood complications has motivated numerous studies. Substitutes were autologous blood, crystalloid or colloid solutions and the acceptance of lower hematocrit and hemoglobin levels. Studies by Leone 19 on major surgeries have shown that hematocrit below 30% decreases blood viscosity, maintains cardiac output and promotes adequate oxygen supply to tissues. Clinically, hemodilution decreases transfusion needs and increases coronary and brain blood flow. The experience with chronic renal disease patients submitted to major surgeries or with Jehovah witnesses has contributed to change transfusion criteria 20.
In orthognathic surgeries some surgeons do not ligate or cauterize blood vessels because cicatricial fibroses would produce lower quality bone callus. Major orthognathic surgeries have considerable blood losses, forcing the anesthesiologist to use induced hypotension and normovolemic hemodilution techniques. Blood replacement is in general with pre or intraoperatively collected autologous blood 21-24.
Acute loss of 20% volume requires 20 to 60 hours for total plasma restoration. In humans, this is followed by extracellular mobilization of albumin-containing fluids, which promotes gradual hematocrit decrease during 2 to 3 days after acute loss 25. Volume of these patients should be replaced with crystalloids or colloids depending on severity, physical status and hypotension duration. Young and healthy patients may tolerate 50% to 60% volume losses; conversely, patients with advanced cardiovascular disease may suffer myocardial ischemia with losses below 30% 26,27.
Replacement of lost red cells in acute bleeding is a gradual process. It starts in response to erythropoietin stimulation on bone marrow parent cells which need minimum maturation of 2 to 5 days. Only acute losses above 2 liters promote marked erythropoietin release by kidneys. Bone marrow starts the process by releasing to circulation mature red cells and reticulocytes during 6 to 12 hours. Bone marrow proliferative response is already seen in the second day after blood loss, but young red cells need a longer period (5 days) to be released to circulation. Maximum bone marrow production level estimated by reticulocytes count is seen 8 to 10 days later. Patients with normal erithropoietic mechanism increase 2 to 3 fold red cells production with 10% to 20% blood loss, and may increase 5 times when hematocrit goes below 30% and iron reserves are adequate 28,29.
Orthognathic surgeries blood loss is significant reaching in average 1200 mL and one should consider the possibility of volume replacement with crystalloid or colloids, red cells preservation or self-donation 30,31.
In young and healthy patients, blood replacement with crystalloids, colloids or self-donation of blood has proven to be effective. Preoperative self-donation should be planned according to estimated blood loss, and most authors recommend volumes between 350 to 450 mL collected in 5 to 7-day intervals. Intraoperative blood collection aims at lowering exposure of red cells, which should not be maintained in the operating room for more than 8 hours 32,33.
Preoperative hematocrit was initially analyzed and then compared to 6 and 24 hours hematocrit. These two values have not shown the reality of intraoperative bleeding. Hematocrit at 6 and 24 hours would not evaluate total blood loss or there was fluid translocation to the interstitial space promoting relative hemoconcentration. Best hematocrit to reflect perioperative blood loss was that of 60 hours, when blood volume was reestablished.
This value was compared to preoperative hematocrit to evaluate inferred perioperative blood loss. Hematocrit at 14 days aimed at analyzing hematic mass reestablishment after perioperative blood loss. Observed recovery was 83%. Literature describes that after blood loss there will be volume replacement in 48 to 72 hours. Explanation is just hypothetical: minor blood loss to release higher amounts of erythropoietin, inadequate ingestion of nutrients as a consequence of surgery, or longer red cells maturation time.
In our study, allogenic transfusion was needed in five patients (1.4%) and was not directly related to anesthetic-surgical technique. Most patients had postoperative anemia, that was however well tolerated (mean Ht of 30%), with the exception of some cases with mild postural hypotension (1.1%).
Perioperative blood loss for all groups was considerable (mean of 1160 mL), with minor need for allogenic blood transfusion. Virtually all patients have tolerated blood losses because they were in general young, physical status ASA I and II without associated diseases. Hematocrit in 14 days has not returned to preoperative values. Observed recovery was 83% of initial values.
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Submitted for publication April 8, 2004
Accepted for publication September 21, 2004
* Received from Centro de Ensino e Treinamento da SBA/SANE, Porto Alegre, RS