Management of physiological variables in neuroanaesthesia: maintaining homeostasis during intracranial surgery

Brain-Relaxing Effect of Different Diuretic Regimens in Supratentorial Tumor Surgery: A Comparative Study Guided by Optic Nerve Sheath Diameter

Background:

Hyperosmolar therapy is a well-established method to approach brain relaxation during craniotomy. Mannitol is used with a wide range of dosing regimens, combination with loop diuretics exerts a synergistic effect resulting in both reduction of the dose and its complications. Ultrasound measurement of optic nerve sheath diameter (ONSD) gives reliable information about intracranial pressure (ICP) and avoids overdosing and complications of osmotherapy.

Aims and Objectives:

In this study, we compare the ordinary dose of mannitol with the low dose combined with furosemide and detect the effect on ICP by ONSD.

Setting and Design:

This is a prospective, randomized, double-blind study involving 60 patients undergoing supratentorial brain tumor surgery.

Materials and Methods:

Sixty patients were enrolled in this study, divided into two equal groups: Group M received mannitol 1 g.kg⁻¹: while Group F received mannitol 0.25 g.kg⁻¹ and furosemide 0.5 mg.kg⁻¹. Reduction in ONSD measurement was the primary objective, while brain-relaxation score (BRS), hemodynamic changes, urine output, serum lactate, and changes in serum electrolyte were the secondary objectives.

Statistical Analysis:

Data collected were analyzed using SPSS software, IBM, USA, version 22. P value was considered significant if <0.05.

Results:

ONSD and BRS showed no statistically significant difference between the studied groups. After diuresis, Group M showed significant reduction in heart rate and mean arterial blood pressure, serum sodium, potassium, and lactate (P = 0.02, P = 0.02, P = 0.001, P = 0.001, P = 0.001, P = 0.001 respectively), with increased urine output (UOP) and fluids replacement (P = 0.00, P = 0.01, respectively).

Conclusion:

Compared to high dose, adding loop diuretics to low-dose mannitol during supratentorial brain tumor surgeries resulted in comparable BRSs with a lower incidence of hemodynamic and metabolic disturbances.

Contemporary Management of Increased Intraoperative Intracranial Pressure: Evidence-Based Anesthetic and Surgical Review

Increased intracranial pressure (ICP) is frequently encountered in the neurosurgical setting. A multitude of tactics exists to reduce ICP, ranging from patient position and medications to cerebrospinal fluid diversion and surgical decompression. A vast amount of literature has been published regarding ICP management in the critical care setting, but studies specifically tailored toward the management of intraoperative acute increases in ICP or brain bulk are lacking. Compartmentalizing the intracranial space into blood, brain tissue, and cerebrospinal fluid and understanding the numerous techniques available to affect these individual compartments can guide the surgical team to quickly identify increased brain bulk and respond appropriately. Rapidly instituting measures for brain relaxation in the operating room is essential in optimizing patient outcomes. Knowledge of the efficacy, rapidity, feasibility, and risks of the various available interventions can aid the team to properly tailor their approach to each individual patient. In this article, we present the first evidence-based review of intraoperative management of ICP and brain bulk.

Definition, evaluation, and management of brain relaxation during craniotomy

The term 'brain relaxation' is routinely used to describe the size and firmness of the brain tissue during craniotomy. The status of brain relaxation is an important aspect of neuroanaesthesia practice and is relevant to the operating conditions, retraction injury, and likely patient outcomes. Brain relaxation is determined by the relationship between the volume of the intracranial contents and the capacity of the intracranial space (i.e. a content-space relationship). It is a concept related to, but distinct from, intracranial pressure. The evaluation of brain relaxation should be standardized to facilitate clinical communication and research collaboration. Both advantageous and disadvantageous effects of the various interventions for brain relaxation should be taken into account in patient care. The outcomes that matter the most to patients should be emphasized in defining, evaluating, and managing brain relaxation. To date, brain relaxation has not been reviewed specifically, and the aim of this manuscript is to discuss the current approaches to the definition, evaluation, and management of brain relaxation, knowledge gaps, and targets for future research.

Cerebral hyperaemia after isoflurane anaesthesia for craniotomy of patients with supratentorial brain tumour

BACKGROUND

Few studies look into cerebral blood flow (CBF) changes during emergence from general anaesthesia for craniotomy. The purpose of this study was to assess CBF changes during emergence from general anaesthesia for craniotomy, through monitoring blood oxygen saturation of jugular vein bulb (SjvO2 ) and transcranial Doppler (TCD).

METHODS

We enrolled 30 patients undergoing selective craniotomy (group C) for supratentorial brain tumour resection and 30 patients undergoing selective abdominal surgery (group A). Mean velocity of middle cerebral artery (Vmca), mean arterial pressure (MAP), SjvO2 (only measured in group C), and arterial CO2 partial pressure were measured before anaesthesia, at tracheal extubation, and 30, 60, 90, 120 min after extubation.

RESULTS

Vmca of the same side of tumour was significantly higher than contralateral Vmca before anaesthesia and at all times after extubation in group C. The ipsilateral Vmca increased significantly (95.7 ± 16.9 cm/s vs. 63.7 ± 6.7 cm/s, P < 0.01) at extubation in group C, then declined but still above baseline significantly in the first 2 h after extubation. While Vmca of the right side changed only slightly (63.6 ± 7.7 cm/s vs. 61.8 ± 8.1 cm/s, P < 0.01) but significantly at extubation in group A. SjvO2 increased significantly (81.4% ± 7.4% vs. 60.9% ± 3.7%, P < 0.01) at extubation in group C, and remained above baseline significantly for 2 h. There was no significant correlation between Vmca and MAP at any time.

CONCLUSIONS

Cerebral hyperaemia occurs after supratentorial brain tumour resection surgery. The hyperaemia is more pronounced on the same side as the tumour.

Hydroelectrolytic balance and cerebral relaxation with hypertonic isoncotic saline versus mannitol (20%) during elective neuroanesthesia

BACKGROUND AND OBJECTIVES

Cerebral relaxation during intracranial surgery is necessary, and hiperosmolar therapy is one of the measures used to this end. Frequently, neurosurgical patients have sodium imbalances. The objective of the present study was to quantify and determine cerebral relaxation and duration of hydroelectrolytic changes secondary to the use of mannitol versus hypertonic isoncotic solution (HIS) during neurosurgery.

METHODS

Cerebral relaxation and hydroelectrolytic changes were evaluated in 29 adult patients before de beginning of infusion, and 30 and 120 minutes after the infusion of equiosmolar loads of approximately 20% mannitol (250 mL) or HIS (120 mL). The volume of intravenous fluids infused and diuresis were recorded. A p < 0.05 was considered significant.

RESULTS

A statistically significant difference in cerebral relaxation between both groups was not observed. Although several changes in electrolyte levels and acid-base balance with mannitol or HIS reached statistical significance only the reduction in plasma sodium 30 minutes after infusion of mannitol, mean of 6.42 ± 0.40 mEq.L(-1), and the increase in chloride, mean of 5.41 ± 0.96 mEq.L(-1) and 5.45 ± 1.45 mEq.L(-1) 30 and 120 minutes after infusion of HIS, caused a transitory dislocation of serum ion levels from normal range. The mannitol (20%) group had a significantly greater diuresis at both times studied compared with HIS group.

CONCLUSIONS

A single dose of hypertonic isoncotic saline solution [7.2% NaCl/6% HES (200/0.5)] and mannitol (20%) with equivalent osmolar loads were effective and safe in producing cerebral relaxation during elective neurosurgical procedures under general anesthesia.