Lumbar Puncture =============== þ Review article: Straus, S. E., K. E. Thorpe, et al. (2006). "How do I perform a lumbar puncture and analyze the results to diagnose bacterial meningitis?" Jama 296(16): 2012-22. CONTEXT: Diagnostic lumbar punctures (LPs), commonly used to rule out meningitis, are associated with adverse events. OBJECTIVE: To systematically review the evidence about diagnostic LP techniques that may decrease the risk of adverse events and the evidence about test accuracy of cerebrospinal fluid (CSF) analysis in adult patients with suspected bacterial meningitis. DATA SOURCES: We searched the Cochrane Library, MEDLINE (using Ovid and PubMed) from 1966 to January 2006 and EMBASE from 1980 to January 2006 without language restrictions to identify relevant studies and identified others from the bibliographies of retrieved articles. STUDY SELECTION: We included randomized trials of patients aged 18 years or older undergoing interventions to facilitate a successful diagnostic LP or to potentially reduce adverse events. Studies assessing the accuracy of biochemical analysis of the CSF for possible bacterial meningitis were also identified. DATA EXTRACTION: Two investigators independently appraised study quality and extracted relevant data. For studies of the LP technique, data on the intervention and the outcome were extracted. For studies of the laboratory diagnosis of bacterial meningitis, data on the reference standard and test accuracy were extracted. DATA SYNTHESIS: We found 15 randomized trials. A random-effects model was used for quantitative synthesis. Five studies of 587 patients compared atraumatic needles with standard needles and found a nonsignificant decrease in the odds of headache with an atraumatic needle (absolute risk reduction [ARR], 12.3%; 95% confidence interval [CI], -1.72% to 26.2%). Reinsertion of the stylet before needle removal decreased the risk of headache (ARR, 11.3%; 95% CI, 6.50%-16.2%). The combined results from 4 studies of 717 patients showed a nonsignificant decrease in headache in patients who were mobilized after LP (ARR, 2.9%; 95% CI, -3.4 to 9.3%). Four studies on the accuracy of biochemical analysis of CSF in patients with suspected meningitis met inclusion criteria. A CSF-blood glucose ratio of 0.4 or less (likelihood ratio [LR], 18; 95% CI, 12-27]), CSF white blood cell count of 500/muL or higher (LR, 15; 95% CI, 10-22), and CSF lactate level of 31.53 mg/dL or more (> or =3.5 mmol/L; LR, 21; 95% CI, 14-32) accurately diagnosed bacterial meningitis. CONCLUSIONS: These data suggest that small-gauge, atraumatic needles may decrease the risk of headache after diagnostic LP. Reinsertion of the stylet before needle removal should occur and patients do not require bed rest after the procedure. Future research should focus on evaluating interventions to optimize the success of a diagnostic LP and to enhance training in procedural skills. þ Bassrupt's Disease - Hypertrophy of spinous processes - May explain some difficult LPs þ Spinal (post-LP) Headache: þ Normal CSF parameters for pediatrics: CSF Normal Normal Bact Viral 0-4 wks >4 wks Mening Mening ---------------------------------------- WBC <=25 <5 >1,000 50-500 <60% PMN 1-2 PMN >50% PMN >50% lymph Protein <=150 15-40 high normal or high Glucose 80% of >50% of low normal or low serum serum þ Color of CSF: - Xanthochromia: + Xanthochromia will occur in the CSF of a premature infant secondary to bilirubin crossing the immature blood-brain barrier. Ref: Rosen's CD ROM line 29802 - Turbidity: + If the CSF contains greater than 200 WBC's per mL or greater than 400 RBC's per mL, it will appear turbid. Ref: Rosen's CD ROM line 29801 þ Glucose in CSF - The normal serum to CSF glucose ratio is 1:0.6. With systemic hyperglycemia the ratio changes to 1:0.4. Ref: Rosen's CD ROM line 29803 þ Opening Pressure - A normal opening CSF pressure is 50 - 190 mm H2O. These values do not apply to a patient in the sitting position. Ref: Rosen's CD ROM line 29791 - Things that increase opening pressure: + sitting position + meningitis + subarachnoid hemorrhage + congestive heart failure - Things that decrease opening pressure: + Dehydration + obstruction above the puncture site Ref: Rosen's CD ROM line 29792 þ Meningitis with normal CSF is possible þ CSF Findings in Meningitis (adults): - Does a predominance of lymphocytes in the CSF rule out bacterial meningitis? No. The CSF of a patient with bacterial meningitis will have a predominance of lymphocytes in 6-13% of cases. Therefore a lymphocytic predominance does not rule out a bacterial etiology. Ref: Rosen's CD ROM line 29796 - Does pre-treatment with antibiotics affect CSF Gram's stain results in a patient with suspected meningitis? Yes. A Gram's stain will identify an organism in 80% of cases of bacterial meningitis which were not treated with antibiotics. This decreases to 60% if a patient was pretreated. Ref: Rosen's CD ROM line 29814 þ Traumatic Tap when testing for meningitis: - [Osborne JP, Pizer B. Effect on the white cell count of contaminating cerebrospinal fluid with blood. Arch Dis Child 1981;56(5):400-1.] Retrospective analysis of heavily blood-stained cerebrospinal fluid shows that there are fewer white cells found in this fluid than would be expected by calculations using the peripheral blood red to white cell ratio. This phenomenon may disguise a true leucocytosis. - [Mehl AL. Interpretation of traumatic lumbar puncture. Predictive value in the presence of meningitis. Clin Pediatr (Phila) 1986;25(11):575-7.] Contamination of cerebrospinal fluid (CSF) with blood was studied prospectively in nine children with aseptic meningitis as the second phase of a study reported in this volume last month. Using criteria defined in the first phase, four of nine patients had recognizably abnormal CSF after experimental contamination with blood. As a third phase of the study, 53 children with bacterial meningitis were reviewed retrospectively to assess if hypothetical contamination of CSF with blood would have disguised their abnormal CSF studies. All but one of these 53 patients had either an abnormal CSF glucose or a positive gram stain (indicators independent of contamination with blood), and none would have gone undiagnosed with hypothetical contamination of up to 200,000 red cells per cubic millimeter. Guidelines for interpretation of laboratory studies following traumatic lumbar puncture are reviewed. þ LP in the diagnosis of subarachnoid hemorrhage þ LP or CT First? - A position paper from the AHA specifically sanctions the use of LP in SAH as a first procedure in certain situations. They state: "Patients suspected of having SAH or meningitis whose neurological examinations, including gait are normal and who will not be hospitalized if their CSF were clear should have a lumbar puncture in the physician's office or emergency ward. In this cirsunstance, CT is a low yield procedure and can probably be ommitted unless the CSF is bloody or xanthochromic." [Caplan LR, Flamm ES, Mohr JP, Toole J, Plum F, Fisher CM, Drake CG, Peerless SJ. Lumbar puncture and stroke. A statement for physicians by a Committee of the Stroke Council, American Heart Association. Circulation 1987 Feb;75(2):505A-507A.] - [Duffy GP. LP in the presence of raised ICP. Brit Med J 1969;1:407-9.] This descriptive study does not really describe the current population who are evaluated for possible CT before LP. "Many of the patients descibed in the Duffy study were obtunded or had focal findings, situations were most physicians would hesitate to perform an LP in the first place without excluding the presence of a space occupying lesion." -- H Louzon, MD - [Duffy GP. LP in spontaneous subarachnoid haemorrhage. Brit Med J. 1982;(285): 1163-4.] Says that death occurred "on the needle" in several cases; but study is poorly done. - [French et al. Lumbar Puncture in Subarachnoid Hemorrhage: yes or no? New Z J Med 1985;98:383-384.] Says LP before CT is safe. - [Patel et al. Lumbar Puncture and Subarachnoid Hemmorrhage. Post Med J 1986;62:1021-1024.] Says LP before CT is safe. - [Zisfein J, Tuchman AJ. Risks of LP in the presence of intracranial mass lesions. Mount Sinai J Med 1988;55(4):283-7.] Debunks Duffy's studies, above. - [Archer BD. CT before LP in acute meningitis: a review of the risks and benefits. Can Med Assoc J 1993;148(6): 961-5.] Has a nice summary of the current status of this topic. - [Baker NC, Kharazi H, Laurent L, Walker AT, Williamson DS, Weissman BN, Zamani A, Sanchez R. The efficacy of routine head CT prior to LP in the ED. J Emerg Med 1994;12(5):597-601.] Suggests that there is no correlation with papilledema and danger when doing LP. - [Gower DJ, Baker AL, Bell WO, Ball MR. Contraindications to LP as defined by computed cranial tomography. J Neurol Neurosurg Psychiatry 1987;50:1071-4.] Notes LP first described by Quincke in 1891, and Cushing noted in 1909 that LP could precipitate herniation. Suggests the following CT contraindications for LP: + lateral shift of the third ventricle or septum pellucidum + loss of suprachiasmatic and circummesencephalic cisterns (basilar cisterns) - [Korein J, Cravioto H, Leicach M. Reevaluation of LP. Neurology ??? 290-7.] - Anecdotal reports suggest LP with increased intracranial pressure may cause uncal herniation and death. But Rosen's textbook says: "In one study, it is shown that only one of 127 patients who underwent LP in the presence of known increased ICP deteriorated after the procedure." þ CT before LP for _meningitis_? - A 27 year review of the English language literature failed to reveal a single case of deterioration following LP for meningitis. He concluded that there were "no case reports, clinical trials or references of any sort supporting a causal relationship between lumbar puncture and poor outcome in meningitis." [Archer BA. Computed Tomography Before Lumbar Puncture in Acute Meningitis: A Review of the Risks and Benefits. Can Med Assoc J 1993;148(6):961-965.] - Rosen says CT before LP in cases of suspected meningitis if: + profoundly depressed mental status + papilledema + focal neuro findings (except ophthalmoplegia) + minimal or absent fever + history or evidence of head trauma (recent OR remote) + recent-onset seizure "These indications, however, must be carefully weighed against the patient's condition, the probabiity of meningitis, and the availability of the CT scan." - Tintinalli's textbook says "the focus is toward determining the presence of papilledema and/or a focal neurological deficit, either of which would be an indication for an emergency CT scan prior to LP."