Defending a traditional practice in the modern era: The use of lumbar puncture in the investigation of subarachnoid haemorrhage

Subarachnoid haemorrhage or traumatic lumbar puncture. Differentiation by cerebrospinal fluid parameters in a multivariable approach

Lumbar puncture (LP) is recommended in patients with thunderclap headache and negative computed tomography to rule out spontaneous subarachnoid haemorrhage (SAH). Blood contamination of cerebrospinal fluid (CSF) due to traumatic LP poses a diagnostic dilemma. Therefore, routine CSF parameters were investigated to distinguish between SAH and a traumatic LP. CSF red blood cell (RBC), white blood cell (WBC) count, total protein, CSF colour and supernatant were used for group comparisons of patients with SAH and 'symptomatic controls'. Due to variable time intervals between bleeding onset and LP in SAH patients in contrast to patients with traumatic LP, where blood contamination of CSF occurs at the time of LP, CSF variables were adjusted for decay in time to allow comparability. Logistic regression analysis identified bloody CSF [odds ratio (OR) 32.6], xanthochromic supernatant [OR 15.5] and WBCadjusted [OR 4.5 (per increase of 100/µl)] as predictors of SAH, while age, sex and CSF total proteinadjusted were no predictors. Optimal cut-point of RBCadjusted (determined at day 1 after bleeding) was > 3667/µl to identify SAH patients with a 97% sensitivity and 94% specificity. Combination of low RBC and clear CSF supernatant was found in none of SAH patients. Combined CSF RBC count and CSF supernatant reliably distinguished traumatic LP from SAH.

New method for the determination of the net bilirubin absorbance in cerebrospinal fluid that minimizes the interference of oxyhaemoglobin and biliverdin

The presence of oxyhaemoglobin and biliverdin interferes with the method recommended by the UK NEQAS Specialist Advisory group for EQA of CSF Proteins and Biochemistry for estimating of the net bilirubin absorbance in CSF. This is easily demonstrated by using solutions with different concentrations of these three substances.The two secondary peaks of the oxyhaemoglobin spectrum at 540 nm and 577 nm are used as reference to minimize these interferences. Those peaks have the same absorbance as at 456 nm in the oxyhaemoglobin spectrum, independent of its concentration. This wavelength is very close to the maximum absorption of bilirubin and, therefore, is suitable for estimating the net bilirubin absorbance.A preliminary study with 48 spectrophotometric analyses of CSF from patients who were suspected of having subarachnoid haemorrhage were used to compare both net bilirubin absorbance estimation methods.The new method is practically free of oxyhaemoglobin and biliverdin interference. This allows for higher sensitivity and a more realistic estimation of the bilirubin concentration in a sample.A better estimation of the bilirubin concentration can have special relevance for diminishing the amount of equivocal or inconclusive cases and also to improve the prematurity of the diagnosis.

Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

Aneurysmal subarachnoid hemorrhage (SAH) is associated with a mortality of more than 30%. Only about 30% of patients with SAB recover sufficiently to return to independent living.

METHODS

This article is based on a selective review of pertinent literature retrieved by a PubMed search.

RESULTS

Acute, severe headache, typically described as the worst headache of the patient's life, and meningismus are the characteristic manifestations of SAH. Computed tomog raphy (CT) reveals blood in the basal cisterns in the first 12 hours after SAH with approximately 95% sensitivity and specificity. If no blood is seen on CT, a lumbar puncture must be performed to confirm or rule out the diagnosis of SAH. All patients need intensive care so that rebleeding can be avoided and the sequelae of the initial bleed can be minimized. The immediate transfer of patients with acute SAH to a specialized center is crucially important for their outcome. In such centers, cerebral aneurysms can be excluded from the circulation either with an interventional endovascular procedure (coiling) or by microneurosurgery (clipping).

CONCLUSION

SAH is a life-threatening condition that requires immediate diagnosis, transfer to a neurovascular center, and treatment without delay.

A new method of subarachnoid puncture for clinical diagnosis and treatment: lateral atlanto-occipital space puncture

OBJECTIVE

Lumbar puncture may not be suitable for some patients needing subarachnoid puncture, while lateral C1–2 puncture and cisterna magna puncture have safety concerns. This study investigated lateral atlanto-occipital space puncture (also called lateral cisterna magna puncture) in patients who needed subarachnoid puncture for clinical diagnosis or treatment. The purpose of the study was to provide information on the complications and feasibility of this technique and its potential advantages over traditional subarachnoid puncture techniques.

METHODS

In total, 1008 lateral atlanto-occipital space puncture procedures performed in 667 patients were retrospectively analyzed. The success rate and complications were also analyzed. All patients were followed up for 1 week after puncture.

RESULTS

Of 1008 lateral atlanto-occipital space punctures, 991 succeeded and 17 failed (1.7%). Fifteen patients (2.25%) reported pain in the ipsilateral external auditory canal or deep soft tissue, 32 patients (4.80%) had a transient increase in blood pressure, and 1 patient (0.15%) had intracranial hypotension after the puncture. These complications resolved fully in all cases. There were no serious complications.

CONCLUSIONS

Lateral atlanto-occipital space puncture is a feasible technique of subarachnoid puncture for clinical diagnosis and treatment. It is associated with a lower rate of complications than lateral C1–2 puncture or traditional (suboccipital) cisterna magna puncture. It may have potential in the neurological diagnostic and treatment fields.

Assessment of Residents Readiness to Perform Lumbar Puncture: A Validation Study

BACKGROUND

Lumbar puncture is a common procedure in many specialties. The procedure serves to diagnose life-threatening conditions, often requiring rapid performance. However, junior doctors possess uncertainties regarding performing the procedure and frequently perform below expectations. Hence, proper training and assessment of performance is crucial before entering clinical practice.

OBJECTIVE

To develop and collect validity evidence for an assessment tool for lumbar puncture performance, including a standard to determine when trainees are ready for clinical practice.

DESIGN

Development of a new tool, based on clinician interviews and a literature review, was followed by an explorative study to gather validity evidence.

PARTICIPANTS AND MAIN MEASURES

We interviewed 12 clinicians from different specialties. The assessment tool was used to assess 11 doctors at the advanced beginners' level and 18 novices performing the procedure in a simulated, ward-like setting with a standardized patient. Procedural performance was assessed by three content experts. We used generalizability theory to explore reliability. The discriminative ability of the tool was explored by comparing performance scores between the two groups. The contrasting groups method was used to set a pass/fail standard and the consequences of this was explored.

KEY RESULTS

The interviews identified that in addition to the technical aspects of the procedure, non-technical elements involving planning and conducting the procedure are important. Cronbach's alpha = 0.92, Generalizability-coefficient was 0.88 and a Decision-study found one rater was sufficient for low-stakes assessments (G-coefficient 0.71). The discriminative ability was confirmed by a significant difference between the mean scores of novices, 40.9 (SD 6.1) and of advanced beginners, 47.8 (SD 4.0), p = 0.004. A standard of 44.0 was established which was consistent with the raters' global judgments of pass/fail.

CONCLUSION

We developed and demonstrated strong validity evidence for the lumbar puncture assessment tool. The tool can be used to assess readiness for practice.

Subarachnoid haemorrhage guidelines and clinical practice: a cross-sectional study of emergency department consultants' and neurospecialists' views and risk tolerances

OBJECTIVES

To establish if emergency medicine and neuroscience specialist consultants have different risk tolerances for investigation of suspected spontaneous subarachnoid haemorrhage (SAH), and to establish if their risk-benefit appraisals concur with current guidelines.

SETTING

4 major neuroscience centres in London.

PARTICIPANTS

58 consultants in emergency medicine and neuroscience specialities (neurology, neurosurgery and neuroradiology) participated in an anonymous survey.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome measure was the highest stated acceptable risk of missing SAH in the neurologically intact patient presenting with sudden onset headache. Secondary outcome measures included agreement with guideline recommendations, risk/benefit appraisal and required performance of diagnostic tests, including lumbar puncture.

RESULTS

Emergency department clinicians accepted almost 3 times the risk of a missed SAH diagnosis compared with the neuroscience specialists (2.8% vs 1.1%; p=0.02), were more likely to accept a higher risk of missed diagnosis for the benefit of a non-invasive test (p=0.04) and were more likely to disagree with current published guidelines stipulating the need for LP in all CT-negative cases (p=0.001).

CONCLUSIONS

Divergence from recognised procedures for SAH investigation is often criticised and attributed to a lack of knowledge of guidelines. This study indicates that divergence from guidelines may be explained by alternative risk-benefit appraisals made by doctors with their patients. Guideline recommendations may gain wider acceptance if they accommodate the requirements of the doctors and patients using them. Further study of clinical risk tolerance may help explain patterns of diagnostic test use and other variations in healthcare delivery.