Cardiac output changes after osmotic therapy in neurosurgical and neurocritical care patients: a systematic review of the clinical literature

Comparison of 4.54% hypertonic saline and 20% mannitol for brain relaxation during auditory brainstem implantation in pediatric patients: a single-center retrospective observational cohort study

BACKGROUND

Mannitol is frequently utilized to achieve intracranial brain relaxation during the retrosigmoid approach for auditory brainstem implantation (ABI). Hypertonic saline (HS) is an alternative for reducing intracranial pressure; however, its application during ABI surgery remains under-investigated. We aimed to compare the efficacy and safety between HS and mannitol for maintaining brain relaxation.

METHODS

This single-center retrospective cohort study included pediatric patients undergoing ABI surgery from September 2020 to January 2022 who received only 4.54% HS or 20% mannitol for brain relaxation. The analysis involved initial doses, subsequent doses, and dosing intervals of the two hyperosmolar solutions, as well as the time elapsed from meningeal opening to the first ABI electrode placement attempt. Additionally, the analysis encompassed electrolyte testing, hemodynamic variables, urine output, blood transfusion, second surgeries, adverse events, intensive care unit length of stay, and 30-day mortality.

RESULTS

We analyzed 68 consecutive pediatric patients; 26 and 42 in the HS and mannitol groups, respectively. The HS group exhibited a reduced rate of supplementary use (7.7% vs. 31%) and lower total urine volume. Perioperative outcomes, mortality, and length of intensive care unit stay did not exhibit significant between-group differences, despite transient increases in blood sodium and chloride observed within 2 h after HS infusion.

CONCLUSIONS

In pediatric ABI surgery, as an osmotherapy for cerebral relaxation, 4.54% HS demonstrated a lower likelihood of necessitating additional supplementation than 20% mannitol. Furthermore, the diuretic effect of HS was weak and the increase in electrolyte levels during surgery was temporary and slight.

Serial Assessment of Hemodynamic and Cerebrovascular Changes After Administration of Mannitol in Postoperative Neurosurgical Patients in the Intensive Care Unit: A Combined Transthoracic and Transcranial Color Doppler Study

INTRODUCTION

Mannitol is widely used in neurosurgical units to mitigate raised intracranial pressure and cerebral edema, crucial in postoperative management. Its hyperosmolar properties reduce brain extracellular fluid, thereby altering cerebral perfusion and cardiac dynamics. However, the temporal and combined effects of mannitol on cardiovascular and cerebrovascular parameters remain inadequately explored in postoperative settings.

METHODS

This prospective observational study enrolled 20 adult patients who underwent elective craniotomies for tumor excision. Mannitol was administered to the patients at a dose of 0.5 mg/kg/dose as a bolus dose over 20 to 30 minutes. The time interval was eight hours between the doses (scheduled dosing). Patients received their first dose of mannitol in the ICU after eight hours of intraoperative dose. The patients were given mannitol for two postoperative days and followed up for two days in the postoperative period. Transthoracic echocardiography and transcranial color Doppler were used to assess cardiovascular and cerebrovascular parameters at multiple intervals post-mannitol administration.

RESULTS

Significant increases in mean flow velocities were observed bilaterally immediately post-mannitol administration on the first postoperative day, indicative of improved cerebral blood flow. However, these changes were transient, with no significant variations noted on the second postoperative day. Cerebrovascular resistance, as measured by the pulsatility index, showed non-significant changes bilaterally across both days. Cardiovascular parameters, including stroke volume and cardiac output, remained stable throughout the study period.

CONCLUSION

Mannitol administration at 0.5 g/kg in postoperative neurosurgical patients transiently improves cerebral perfusion without causing significant hemodynamic instability. This study underscores the importance of monitoring both cerebrovascular and cardiovascular parameters post-mannitol administration to optimize patient management and outcomes.

Hyperosmolar Therapy in Elderly Neurosurgical Patients: Comparison of the Effect of Mannitol (20%) and Hypertonic Saline (3%) on Advanced Cardiovascular Parameters Using Transesophageal Echocardiography: A Preliminary Randomized Controlled Trial

OBJECTIVE

Osmotherapeutic agents increase the intravascular volume by withdrawing water from the brain followed by relative hypovolemia due to diuresis leading to significant changes in systemic hemodynamics which might have adverse consequences in the elderly. We studied the effect of mannitol (20%) and hypertonic saline (HTS) (3%) on left ventricular outflow tract velocity time integral (LVOT-VTI) and cardiac output (CO) in elderly patients undergoing supratentorial neurosurgical procedures using transesophageal echocardiography.

METHODS

We recruited 28 patients aged above 65 years undergoing supratentorial craniotomy who received equiosmolar solutions of 5.35 ml/kg of 3% HTS (group HS, n = 14) or 5 ml/kg of 20% mannitol (group M, n = 14). LVOT-VTI was recorded at baseline, 15, 30, 45, 60, and 90 minutes postinfusion and CO was derived. We also recorded heart rate, blood pressure, fluid balance, brain relaxation, vasopressor use, complications, and neurological outcome.

RESULTS

We found a significant decrease in LVOT-VTI at 45, and 60 minutes in group M as compared to group HS [mean (standard deviation), 16.76 (1.81) vs. 20.78 (1.87), P < 0.001, 17.4 (2.38) vs. 19.16 (2), P = 0.044, respectively]. We also found a corresponding significant fall in CO [3863.16 (845.87) vs. 4745.59 (1209.33) ml/minute, P = 0.034] and systolic blood pressure (P = 0.039), at 45 minutes in group M. Urine output was higher in group M (P < 0.001). All other parameters were comparable.

CONCLUSIONS

HTS appears to be associated with better systemic hemodynamics (LVOT-VTI, CO) while providing equivalent brain relaxation as mannitol in elderly patients. A future larger study is required to confirm our preliminary findings.

Comparison of Equiosmolar Doses of 7.5% Hypertonic Saline and 20% Mannitol on Cerebral Oxygenation Status and Release of Brain Injury Markers During Supratentorial Craniotomy: A Randomized Controlled Trial

BACKGROUND

Hyperosmolar therapy is the mainstay of treatment to reduce brain bulk and optimize surgical exposure during craniotomy. This study investigated the effect of equiosmolar doses of 7.5% hypertonic saline (HTS) and 20% mannitol on intraoperative cerebral oxygenation and metabolic status, systemic hemodynamics, brain relaxation, markers of cerebral injury, and perioperative craniotomy outcomes.

METHODS

A total of 51 patients undergoing elective supratentorial craniotomy were randomly assigned to receive 7.5% HTS (2 mL/kg) or 20% mannitol (4.6 mL/kg) at scalp incision. Intraoperative arterial and jugular bulb blood samples were collected at predefined time intervals for assessment of various indices of cerebral oxygenation; multiple hemodynamic variables were concomitantly recorded. S100B protein and neuron-specific enolase levels were determined at baseline, and at 6 and 12 hours after surgery for assessment of neuronal injury. Brain relaxation and perioperative outcomes were also assessed.

RESULTS

Demographic and intraoperative data, brain relaxation score, and perioperative outcomes were comparable between groups. Jugular bulb oxygen saturation and partial pressure of oxygen, arterial-jugular oxygen and carbon dioxide differences, and brain oxygen extraction ratio were favorably affected by 7.5% HTS up to 240 minutes postinfusion ( P <0.05), whereas mannitol was associated with only a short-lived (up to 15 min) improvement of these indices ( P <0.05). The changes in cerebral oxygenation corresponded to transient expansion of intravascular volume and improvements of cardiovascular performance. Increases in S100B and neuron-specific enolase levels at 6 and 12 hours after surgery ( P <0.0001) were comparable between groups.

CONCLUSIONS

The conclusion is that 7.5% HTS has a more beneficial effect on cerebral oxygenation than an equiosmolar dose of 20% mannitol during supratentorial craniotomy, yet no clear-cut clinical superiority of either solution could be demonstrated.

Cardiac output changes after osmotic therapy in neurosurgical and neurocritical care patients: a systematic review of the clinical literature

AIM

Osmotherapy constitutes a first-line intervention for intracranial hypertension management. However, hyperosmolar solutes exert various systematic effects, among which their impact on systemic haemodynamics is poorly clarified. This review aims to appraise the clinical evidence of the effect of mannitol and hypertonic saline (HTS) on cardiac performance in neurosurgical and neurocritical care patients.

METHOD

A database search was conducted to identify randomized clinical trials and observational studies reporting HTS or mannitol use in acute brain injury setting. The primary end-points were alterations of cardiac output (CO) and other haemodynamic variables, while the impact of osmotic agents on intracranial pressure, brain relaxation, plasma osmolality, electrolyte levels and urinary output constituted secondary outcomes.

RESULTS

Eight studies, enrolling 182 patients in total, were included. HTS exerted a more profound cardiac output augmentation than mannitol, but no distinct difference between groups occurred. Central venous pressure, stroke volume and stroke volume variation were favourably affected by both osmotic agents, whilst the reported changes in blood pressure were inconclusive. HTS infusion yielded a larger intracranial pressure reduction than mannitol but had an equivalent effect on brain relaxation. Mannitol presented a more potent diuretic effect than HTS. Effect on serum osmolality was alike in both osmotic agents, but contrary to HTS-promoted hypernatraemia, mannitol use induced transient hyponatraemia.

CONCLUSIONS

Mannitol or HTS administration seems to induce an enhancement of cardiac performance; being more prominent after HTS infusion. This effect combined with mannitol-induced enhancement of diuresis and HTS-promoted increase of plasma sodium concentration could partially explain the effects of osmotherapy on cerebral haemodynamics.