Neuroanesthesiology Update

Intraoperative arterial pressure and delayed cerebral ischemia in patients with aneurysmal subarachnoid hemorrhage after surgical clipping: A retrospective cohort study

Background

Delayed cerebral ischemia (DCI) is the major predictor of poor outcomes in patients with aSAH. Previous studies have attempted to assess the relationship between controlling blood pressure and DCI. However, the management of intraoperative blood pressure in reducing the occurrence of DCI still remains inconclusive.

Methods

All patients with aSAH who received general anesthesia for surgical clipping between January 2015 and December 2020 were prospectively reviewed. Patients were divided in the DCI group or the non-DCI group depending on whether DCI occurred or not. Intraoperative arterial pressure was measured every minute and recorded in an electronic anesthesia recording system along with intraoperative medication and other vital signs. The initial neurological function score, aneurysm characteristics, surgical and anesthetic information, and outcomes were compared between the DCI and the non-DCI groups.

Results

Among 534 patients who were enrolled, a total of 164 (30.71%) patients experienced DCI. The baseline characteristics of patients were similar between the groups. The World Federation of Neurosurgical Societies (WFNS) Scale > 3, age ≥ 70 years, and the modified Fisher Scale > 2 were significantly higher in patients with DCI than those without. Though it was the second derivative of the regression analysis, 105 mmHg was adopted as the threshold for intraoperative hypotension and was not associated with DCI.

Conclusions

The threshold of 105 mmHg was adopted as intraoperative hypotension even though it was the second derivative of the regression analysis and could not be proved to be associated with delayed cerebral ischemia adjusted by the baseline severity of aSAH and age.

Blood Pressure and End-tidal Carbon Dioxide Ranges during Aneurysm Occlusion and Neurologic Outcome after an Aneurysmal Subarachnoid Hemorrhage

EDITOR’S PERSPECTIVE

What We Already Know about This Topic

It remains unknown what end-tidal carbon dioxide and mean arterial pressure are optimal for surgical management of patients with an aneurysmal subarachnoid hemorrhage

What This Article Tells Us That Is New

The investigators retrospectively evaluated 1,099 patients who had endovascular coiling or surgical clipping for subarachnoid hemorrhages

There were no clinically important or statistical significant associations between either end-tidal carbon dioxide or mean arterial pressure thresholds and Glasgow Outcome Scale at discharge or three months

Other prognostic factors are more important than carbon dioxide and blood pressure, at least within the observed clinical ranges

Background

Hypocapnia, hypotension, and hypertension during aneurysm occlusion in patients with an aneurysmal subarachnoid hemorrhage may lead to a poor prognosis, but evidence for end-tidal carbon dioxide (ETco2) and mean arterial pressure (MAP) targets is lacking. Within the ranges of standardized treatment, the authors aimed to study the association between hypocapnia (Paco2 < 35 mmHg), hypotension (MAP < 80 mmHg), and hypertension (MAP >100 mmHg) during general anesthesia for aneurysm occlusion and neurologic outcome.

Methods

This retrospective observational study included patients who underwent early aneurysm occlusion after an aneurysmal subarachnoid hemorrhage under general anesthesia. ETco2 and MAP were summarized per patient as the mean and time-weighted average area under the curve for various absolute (ETco2 < 30, < 35, < 40, < 45 mmHg; and MAP < 60, < 70, < 80, > 90, > 100 mmHg) and relative thresholds (MAP < 70%, < 60%, < 50%). Clinical outcome was assessed with the Glasgow Outcome Scale at discharge and at three months, as primary and secondary outcome measure, respectively.

Results

Endovascular coiling was performed in 578 patients, and 521 underwent neurosurgical clipping. Of these 1,099 patients, 447 (41%) had a poor neurologic outcome at discharge. None of the ETco2 and MAP ranges found within the current clinical setting were associated with a poor neurologic outcome at discharge, with an adjusted risk ratio for any ETco2 value less than 30 mmHg of 0.95 (95% CI, 0.81 to 1.10; P < 0.496) and an adjusted risk ratio for any MAP less than 60 mmHg of 0.94 (95% CI, 0.78 to 1.14; P < 0.530). These results were not influenced by preoperative neurologic condition, treatment modality and timing of the intervention. Comparable results were obtained for neurologic outcome at three months.

Conclusions

Within a standardized intraoperative treatment strategy in accordance with current clinical consensus, hypocapnia, hypotension, and hypertension during aneurysm occlusion were not found to be associated with a poor neurologic outcome at discharge in patients with an aneurysmal subarachnoid hemorrhage.

The effect of dexmedetomidine on cerebral perfusion and oxygenation in healthy piglets with normal and lowered blood pressure anaesthetized with propofol-remifentanil total intravenous anaesthesia

BACKGROUND

During anaesthesia and surgery, in particular neurosurgery, preservation of cerebral perfusion and oxygenation (CPO) is essential for normal postoperative brain function. The isolated effects on CPO of either individual anaesthetic drugs or entire anaesthetic protocols are of importance in both clinical and research settings. Total intravenous anaesthesia (TIVA) with propofol and remifentanil is widely used in human neuroanaesthesia. In addition, dexmedetomidine is receiving increasing attention as an anaesthetic adjuvant in neurosurgical, intensive care, and paediatric patients. Despite the extensive use of pigs as animal models in neuroscience and the increasing use of both propofol-remifentanil and dexmedetomidine, very little is known about their combined effect on CPO in pigs with uninjured brains. This study investigates the effect of dexmedetomidine on CPO in piglets with normal and lowered blood pressure during background anaesthesia with propofol-remifentanil TIVA. Sixteen healthy female Danish pigs (crossbreeds of Danish Landrace, Yorkshire and Duroc, 25-34 kg) were used. Three animals were subsequently excluded. The animals were randomly allocated into one of two groups with either normal blood pressure (NBP, n = 6) or with induced low blood pressure (LBP, n = 7). Both groups were subjected to the same experimental protocol. Intravenous propofol induction was performed without premedication. Anaesthesia was maintained with propofol-remifentanil TIVA, and later supplemented with continuous infusion of dexmedetomidine. Assessments of cerebral perfusion obtained by laser speckle contrast imaging (LSCI) were related to cerebral oxygenation measures (PbrO2) obtained by an intracerebral Clark-type Licox probe.

RESULTS

Addition of dexmedetomidine resulted in a 32% reduction in median PbrO2 values for the LBP group (P = 0.03), but no significant changes in PbrO2 were observed for the NBP group. No significant changes in LSCI readings were observed in either group between any time points, despite a 28% decrease in the LBP group following dexmedetomidine administration. Caval block resulted in a significant (P = 0.02) reduction in median MAP from 68 mmHg (range 63-85) at PCB to 58 mmHg (range 53-63) in the LBP group, but no significant differences in either PbrO2 or LSCI were observed due to this intervention (P = 0.6 and P = 0.3 respectively).

CONCLUSIONS

Addition of dexmedetomidine to propofol-remifentanil TIVA resulted in a significant decrease in cerebral oxygenation (PbrO2) measurements in piglets with lowered blood pressure. Cerebral perfusion (LSCI) did not decrease significantly in this group. In piglets with normal blood pressure, no significant changes in cerebral perfusion or oxygenation were seen in response to addition of dexmedetomidine to the background anaesthesia.

[Neuroanesthesia]

Anesthesiological challenges during craniotomy result from the anatomically related low compensatory capacity of the intracranial space in response to increased volume and the low ischemic tolerance of brain tissue. The anesthetic agents used should therefore not increase the intracranial volume and improve the ischemic tolerance. An acute life-threatening increase of intracranial pressure can be temporarily treated by hyperventilation until measures, such as osmotherapy and infusion of intravenous anesthetics become effective. During an operation the homeostatic parameters including blood volume, blood pressure, partial pressure of carbon dioxide and oxygen in blood, plasma glucose concentration and core body temperature have to be closely monitored and kept normal (6 Ns). Optimal implementation of anesthesia necessitates a detailed knowledge of the surgical approach and potential complications. Postoperatively, patients should be extubated as soon as possible to closely monitor cognitive function so that potential deterioration can be detected.

Risk factors for post-operative respiratory failure among 94,621 neurosurgical patients from 2006 to 2013: a NSQIP analysis

INTRODUCTION

Post-operative respiratory failure can occur after neurosurgical operations. Identification of risk factors for respiratory failure after neurosurgery may help guide clinical decision-making, decrease length of stay, improve patient outcomes, and lower costs.

METHODS

We performed a search of the ACS-NSQIP database for all patients undergoing operations with a neurosurgeon from 2006 to 2013. We analyzed demographics, past medical history, and post-operative respiratory failure, defined as unplanned intubation and/or ventilator dependence for more than 48 h post-operatively.

RESULTS

Of 94,621 NSQIP-reported neurosurgical patients from 2006 to 2013, 2325 (2.5 %) developed post-operative respiratory failure. Of these patients, 1270 (54.6 %) were male, with an overall mean age of 60.59 years; 571 (24.56 %) were current smokers and 756 (32.52 %) were ventilator-dependent. Past medical history included dyspnea in 204 patients (8.8 %), COPD in 198 (8.5 %), and congestive heart failure in 66 (2.8 %). The rate of post-operative respiratory failure decreased from 4.1 % in 2006 to 2.1 % in 2013 (p < 0.001). Of the 2325 patients with respiratory failure, 1061 (45.6 %) underwent unplanned intubation post-operatively and 1900 (81.7 %) were ventilator-dependent for more than 48 h. The rate of both unplanned intubation (p < 0.001) and ventilator dependence (p < 0.001) decreased significantly from 2006 to 2013. Multivariate analysis demonstrated that significant risk factors for respiratory failure included inpatient status (p < 0.001, OR = 0.165), age (p < 0.001, OR = 1.014), diabetes (p = 0.001, OR = 1.489), functional dependence prior to surgery (p < 0.001, OR = 2.081), ventilator dependence (p < 0.001, OR = 10.304), hypertension requiring medication (p = 0.005, OR = 1.287), impaired sensorium (p < 0.001, OR = 2.054), CVA/stroke with or without neurological deficit (p < 0.001, OR = 2.662; p = 0.002, OR = 1.816), systemic sepsis (p < 0.001, OR = 1.916), prior operation within 30 days (p = 0.026, OR = 1.439), and operation type (cranial relative to spine, p < 0.001, OR = 4.344, Table 4).

CONCLUSIONS

Based on the NSQIP database, risk factors for respiratory failure after neurosurgery include pre-operative ventilator dependence, alcohol use, functional dependence prior to surgery, stroke, and recent operation. The overall rate of respiratory failure decreased from 4.1 % in 2006 to 2.1 % in 2013 according to these data.

Postoperative complications of spine surgery

A variety of surgical approaches are available for the treatment of spine diseases. Complications can arise intraoperatively, in the immediate postoperative period, or in a delayed fashion. These complications may lead to severe or even permanent morbidity if left unrecognized and untreated [1-4]. Here we review a range of complications in the early postoperative period from more benign complications such as postoperative nausea and vomiting (PONV) to more feared complications leading to permanent loss of neurological function or death [5]. Perioperative pain management is covered in a separate review (Chapter 8).