Fluid responsiveness

Patients on non-intensive care wards (such as our stroke unit) are not as simple to understand as a patient with arterial and central line, with ultrasound and more high tech equipment around every corner.

So assume a lady with advanced heart failure, medium size stroke and a decent aspiration pneumonia, who is raised to your attention by a stroke nurse that is worried about the blood pressure of 78/28 mmHg with a heart rate of 109/min (sinus rhythm). What do we have by way of judging her fluid status? More precisely, is she going to benefit from a decent fluid bolus (say 500 ccs of NS or LR)?

From all evidence-based reviews on the history and physical, we know that a hemorrhagic patient might be identifiable by postural hypotension, tachycardia and postural dizziness. But this might be hard to check in a patient who is not able to sit or stand such as ours. Even more, both history and physical fare just as badly as flipping a coin (an AUC of the ROC curve of 56%), at least in the hands of an intensivist… Jugular venous pressure might be interesting for cardiological reasons, but the connection to right ventricular preload is difficult to judge as we don’t know the compliance of the system.

What remains are dynamic studies of responses to fluid challenges, such as

  • Passive leg raising: flip the legs up to 45° and the trunk down to 0°, effectively keeping the standard angle of legs to trunk of about 30-45°, pushing about 400 ccs of blood up to the heart.
  • Controlled respiration with volumes high above the usual aim of 6 ml/kg and with proper pressures (this yields vast changes in pressures, volumes and fluid compartmentalization around the heart and thorax)
  • Saline bolus of 500 ccs.

So what are the physiological variables to monitor during such a maneuver? In order of increasing complexity and high-tech-yness

  • Blood pressure (MAP), or even better pulse pressure (syst – diastol)
  • Heart rate (if the carotid sinus reflex is intact and Bezold-Jarisch/Bainbridge keep quiet)
  • Perfusion measurement of your oxygen saturation monitor (reflecting stroke volume in the periphery, which is worse than central stroke volume, but better than most measures)
  • etCO2, if you happen to monitor it, reflecting minute volume
  • PPV or SVV if measured by pulse contour analysis (PICCO = LIDCO, both better than Vigileo)
  • Inferior vena cava diameter and collapsibility index
  • Stroke volume (if measured by TEE or pulmonary catheter)
  • Femoral artery (better carotid artery, but this hasn’t been studied) mean systolic velocity
  • NICOM (thoracic impedance boosted)
  • … many more devices I have never used

So on any normal ward with – say – a simple vital sign monitor, us Neurologists can do best with ultrasound of the IVC and the carotid artery and the pulse pressure plus (perhaps) heart rate during passive leg raise. But this isn’t too bad.

References:

Peripheral venous lines – rotate or not?

An age old discussion: should you change iv-lines after 72-96 hours, as proposed by any proper guideline out there?

This study finishes the discussion once and for all (it probably wasn’t an issue after some previous studies already) – there is no point in prophylactically resiting. Yet there are some important take homes for your care of iv-lines:

  • emergency lines (not inserted with maximum sterility) should be changed, if protracted iv-treatment is expected
  • non-emergency lines should be inserted with best possible sterility (3 times disinfection, give them time, use a proper sterile swab)
  • if there is any hint of thrombophlebitis, try to recover some germs from it before pulling it out (probably too late), then check the degree of local thrombosis. If there is any, consider heparin + antibiotics. If it extends to near deep veins, do an ultrasound and heparinize.

Central venous access

Have you ever experienced the following: you instruct a peer in how to do a particular procedure while he is doing it, but then realize that you cannot really presuppose knowledge about the theoretical facts, such as indications, anatomy and so on?

We use the case of central venous catheter access to review the most important indications, anatomy, differential access site indications and so forth, then go through the basic steps and try to list details that you could never explain if doing a live instruction.

References: any modern ICU book. I use Irwin & Rippe’s, which is rather conservative. For some cool facts, I can recommend the book Evidence-based critical care.

The neurootological examination of dizzy patients

We do have many dizzy patients to work up in the ER. Nowadays with the HINTS or INFARCT scheme, life has become much easier if you have to distinguish between vestibular neuritis and central vertigo (stroke and migraine mostly) in an acute vestibular syndrome. But if they are only dizzy, you have to invest more work. In today’s session we concentrated on the neurophysiology of extraocular eye movements, the various categories and how to examine them.
From a physiological viewpoint you have to distinguish the following EOM categories:
  • Voluntary and involuntary (e.g. the correcting saccade of a nystagmus) saccades
  • VOR movements
  • Smooth pursuit
  • Optokinetic reflex
Here are the basic exam steps for a dizzy patient:
  • Spontaneous nystagmus (using Frenzel glasses or the penlight cover test)
  • Gaze directions: check gaze in all 9 directions at about 30-45° for diplopia and bulbar misalignment
  • Check for gaze evoked nystagmus in the same step
  • Head shaking nystagmus (quickly oscillate move the head between left 45° to right 45° with about 2 cycles per second)
  • Vergence movements (move the fixated pen from 60 to 10cm before the nose)
  • Saccadic eye movements: preferably use diagonal saccades between two pens
  • Smooth pursuit: estimate the speed at which the patient can still keep up with a moving pen, horizontally and vertically, compare sides
  • Horizontal VOR: use the head thrust maneuver (Halmagyi)
  • VOR cancellation: the easiest is to have the patient follow your finger with his head rather than the eyes, can also use a rotating chair
  • Dynamic visual acuity: have the patient read some text while moving his head rhythmically between left and right
  • Positional nystagmus: Dix-Hallpike, head roll test and head hanging test
  • Tragus test: occlude the ear and press on the tragus
  • Romberg’s and Unterberger’s test
  • Complete neuro examination including testing for extremity ataxia
I never use the drum roll because it does not properly test the optokinetic reflex (which is a non-foveal process).

Epidural blood patch

Neurology is an ER specialty nowadays and there are a few therapeutic interventions in emergency neurology that can really make your day, among them

  • cool treatments for migraine (propofol, ketamine, oxygen)
  • the BPPV liberation maneuvers
  • quick-and-easy thrombolysis
  • the epidural blood patch.

I find that many experienced neurologists don’t routinely do blood patches, but prescribe tedious bed rest and caffeine for weeks. Why that should be is not clear, yet we aim to improve matters by teaching the basic technique in one session.

Remark that there is indeed evidence for the blood patch (even the Cochrane nowadays recognises it).

Here is my recipe

  • Get two persons
  • Sterile garments for both of them
  • One traumatic LP needle (Quincke), standard size, a butterfly, 2 syringes 20 ml preferrably Luer lock
  • Prep both the arm for venipuncture and the standard LP field on your sitting patient (position as for sitting-LP)
  • Use maximum sterile technique (grade III: iodine-containing, 3 times, full exposition time)
  • Both put on sterile garments and simultaneously start working
  • Advance your Quincke needle 1 cm below the skin, pull out the mandrin, put on a syringe with about 10 ccs of air
  • Start oscillating the plunger and advance the needle until you can suddenly push in air (loss-of-resistance)
  • Fix the needle at this depth with your left hand (this is important)
  • Get the sterilly obtained 15-20 ccs of patient blood
  • Slowly push the blood in (there is some resistance here, continually increasing), noting that the patient feels the pressure
  • Expect the blood to explode suddenly, so beware to wear glasses
  • Pull everything out, put on a strip, then have the patient stand up and feel no pain anymore.

Isolated abducens nerve palsy

The more strokes you treat the less you remember the old wisdoms, such as IV and VI aren’t as bad as III. 

Presented a patient with isolated VI nerve palsy, what is the management? When could you forgo imaging?

  • Review the anatomy of VI, remarking how easy it is to harm, but nearly always requires concurrent symptoms of other areas (such as VII, sensory, paralysis, IV/III and so on)
  • do a proper exam to rule these symptoms out
  • if the clinical course and risk factors for microvascular damage are typical, you can do without imaging and observe.

References: This excellent article. 

Thunderclap headache

We encounter one of these at least every week, so the question of how much diagnostics to order after a painstakingly thorough history and a complete physical including fundoscopy is quite important. Obviously, CT and a spinal tap is always necessary, but then what? I think, the minimum in fact includes CT-angiography (using a delay of 8-10s) to image both arteries and veins, in order to rule out SVT and RCVS (both of which are highly relevant). In addition, I recommend a follow-up MRI after discharge from the ER.
We discuss the differential, consisting of at least:

  • SAH/sentinel headache
  • RCVS
  • Dissection
  • Stroke
  • SVT
  • ICH and other bleeds (retroclival hematoma)
  • PRES
  • Meningitis
  • SIH
  • Pituitary apoplexy
  • a lot of zebras, such as third ventricle colloid cyst, MI, Takotsubo, …

As a reference I recommend this article by Ducros of 2013 (he seems to be an authority on this topic as well as RCVS).