Acute normovolemic hemodilution to avoid blood transfusion during intracranial aneurysm surgery in a patient with atypical antibodies.

Acute normovolemic haemodilution (ANH) has been used in neurosurgical operations to reduce the incidence of homologous blood transfusions. We report a case of anterior communicating artery aneurysm in a patient with atypical antibodies in the serum, who was posted for clipping of the said aneurysm, and was managed with ANH in the perioperative period in order to avoid blood transfusions.

INTRODUCTION

Early surgery is advocated in aneurysmal subarachnoid hemorrhage due to increased morbidity and mortality associated with rebleeding.[1] Blood loss can be significant in these surgeries if the aneurysm ruptures in the intraoperative period.[2] Hence, blood grouping and cross-matching is routinely done for this group of patients. Many centers keep blood readily available in the operation theatres during aneurysm surgeries. We report anesthetic management of a case of anterior communicating artery aneurysm (ACOM) patient with atypical antibodies in the serum scheduled for craniotomy and clipping of the aneurysm.

CASE REPORT

A 59-year-old male, weighing 60 kg, with recently diagnosed hypertension on irregular treatment, presented to the casualty with history of sudden onset severe headache and loss of consciousness for 10 min. He regained consciousness spontaneously, following which, he had four episodes of vomiting. On examination, the patient was conscious and oriented, with Glasgow Coma Scale 15. Central nervous system examination revealed nuchal rigidity with no focal neurologic deficits. Computed tomography (CT) scan confirmed the diagnosis of subarachnoid hemorrhage with blood seen in Sylvian fissures and interhemispheric fissure. CT angiography revealed, an ACOM aneurysm 10 mm × 4 mm facing anteriorly and inferiorly. The patient was planned for right pterional craniotomy and clipping of the ACOM aneurysm.

He was started on tablet phenytoin 100 mg TDS, and tablet nimodipine 60 mg 4 hourly. The patient's baseline investigations revealed haemoglobin of 15 g/dl and haematocrit of 45%. All other reports like serum electrolytes and renal function tests were normal. 5 ml blood was sent to the blood bank for blood grouping and cross-matching for 2 units of homologous blood. Blood bank informed that the patient's blood group was O positive and further reported the detection of atypical antibodies in the serum, with no compatibility to any of the blood bags available in the blood bank.

Because of the urgency of the surgical procedure, we planned for acute normovolemic haemodilution (ANH) in the patient. All standard monitors were attached, and vital parameters noted. Under aseptic precautions, a 16 gauge intravenous line was secured in the right antecubital vein and 900 ml of blood was withdrawn in two 450 ml blood bags containing citrate-phosphate-dextrose–A solution. During this procedure, equal volumes of 6% hetastarch was infused using a separate intravenous access. Vital parameters were monitored and recorded during the process. The collected blood was labelled as “for autologous use only” and stored at room temperature.

The patient was induced using fentanyl 2 mcg/kg, propofol 1.5 mg/kg and vecuronium 0.1 mg/kg. He was intubated with 8.0 cuffed endotracheal tube, and anesthesia was maintained with 1–1.2 minimum alveolar concentration isoflurane in the oxygen-air mixture. To reduce the intraoperative blood loss, we used 10 mg/kg bolus of tranexamic acid and 1 mg/kg/h infusion in the intraoperative period.[3] The approximate blood loss in the intraoperative period was 1000 ml and both the units of autologous blood were transfused to the patient intraoperatively. The patient was carefully monitored for any adverse reactions associated with blood transfusion. The rest of the surgical procedure was uneventful. Postoperative haematocrit on day 1 was 33%, and the patient was discharged on the 5th postoperative day after satisfactory recovery.

DISCUSSION

The annual incidence of aneurysmal subarachnoid haemorrhage is 6–8/100,000 population, with 1 out of 8 patients dying before reaching the hospital.[4] After the initial bleeding, the risk of rebleeding is 3–4% in the initial 24 h and 1–2% each day during the 1st month.[5] Reported cumulative 8–10 years incidences of late rebleeding (more than 1-year after initial subarachnoid haemorrhage) vary from 0.1% to 3.2%.[6] Recurrent haemorrhage carries a case fatality rate approaching 70% and is currently the most treatable cause to limit bad outcomes.[5] Hence, the current trends in neurosurgery is to clip or coil the aneurysm as early as possible.

Intraoperative blood loss can contribute to morbidity in aneurysm surgeries. In a retrospective analysis by Le Roux et al., 134 of 547 patients (24.5%) patients undergoing aneurysm surgery required blood transfusion.[2] Among patients who received an intraoperative transfusion, patients' aneurysm rupture required significantly more homologous blood as compared to patients who did not have a rupture (3.6 ± 0.35 vs. 1.9 ± 0.12 units). Hence, preoperative blood grouping and cross-matching is routinely practiced in aneurysm surgeries.[7] In our patient, because of the presence of atypical antibodies, no cross matched compatible blood was available. Hence, we planned for ANH. 900 ml of blood was withdrawn to target a haematocrit of 35%. The amount of blood which can be drawn was calculated using the formula:

Volume = (Hi − Ht) × EBV/Ha

Where,

Hi – initial haematocrit

Ht – target haematocrit

Ha – average haematocrit and

EBV – estimated blood volume.

Acute withdrawal of blood can lead to hemodynamic disturbances and hypovolemia. This can increase the risk of cerebral vasospasm. Hence, we monitored vital parameters and replaced the intravascular volume with an equal amount of 6% hetastarch.

The use of tranexamic acid in cases of intracranial vascular surgery may generate concerns of possible cerebral thrombosis. The link with thrombosis associated with the use of tranexamic acid is mainly supported by case reports. However, a study of 256 pregnant women's taking tranexamic acid, of whom 169 delivered by caesarean section, found no increased risk of thrombosis.[8] While there is no doubt that tranexamic acid should be avoided if active thromboembolic disease is present, in our patient, who did not have any such risks, a risk-benefit analysis argued in favour of using the drug.

We used a synthetic colloid, hetastarch, for volume replacement during ANH. Due to escaping crystalloid fluids into the interstitial space after 30–40 min, the volume for replacing, in case we had chosen a crystalloid, would have been 3 times the volume removed, that is, for each 1 ml of blood removed, 3 ml of crystalloid solution would have to be infused. While albumin might have been an alternative to hetastarch in this regard, in our institution, the dilution process begins with the use of nonhuman colloid. Preparation of hetastarch is preferred because of the low cost and clinician familiarity. While FDA has issued a boxed warning on increased mortality and severe renal injury, as well as risk of bleeding, such warning has been issued for patients in specific settings such as patients in critical care units, sepsis, preexisting renal dysfunction, open heart surgery using cardiopulmonary bypass and patients with severe liver disease. The final word on the use of synthetic colloids in other patients undergoing elective noncardiac surgical procedures is awaited.

ANH has been successfully used in neurosurgical operations. Mitosek-Sabbo et al. induced postinduction haemodilution in 50 patients with intracranial aneurysm surgeries and 30 patients served as controls.[9] Perioperative haemodilution reduced the requirement for homologous blood transfusion. The Glasgow outcome scales were better at 1 and 6 months postdischarge in patients who underwent hemodilution. Oppitz and Stefani used ANH in 100 neurosurgical procedures with 47 aneurysm surgery patients acting as controls. They concluded that ANH is safe in neurosurgical procedures.[10] Daif et al. studied the cerebral effects of ANH during brain tumor resection surgeries.[11] They monitored jugular oximetry, arterial jugular oxygen content difference, and cerebral oxygen extraction. These cerebral oxygenation parameters were comparable in ANH and control groups. Naqash et al. evaluated ANH in forty neurosurgical patients undergoing meningioma resections. Homologous blood was required in only 5 of 20 (25%) patients in ANH group as compared to all patients in the control group.[12] We use ANH routinely in all brain tumor surgery patients with haematocrit >36% in our institute. Thus, ANH can be safely used to reduce the requirement for homologous blood transfusion in neurosurgical patients.

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Conflicts of interest

There are no conflicts of interest