Pain(ful) management?

Other than the ground-breaking results of John Carlisle that we have recently discussed, this latest issue of the Journal gives us food for thought in our management of acute pain. Pritchard et al present a unique cost-effectiveness analysis of using patient-controlled analgesia (PCA) vs standard care in patients admitted from the emergency department for the management of acute traumatic or non-traumatic abdominal pain. They assessed hourly visual analogue scale (VAS) pain scores for 12 hours in 20 patients meeting inclusion criteria, and determined the hourly rates patients were in moderate to severe pain (VAS ≥45). Cost-effectiveness was quantified by determining the additional cost per hour that moderate to severe pain was avoided with PCA rather than standard practice. As expected, overall costs were higher in the PCA groups but did this translate in to additional cost-effectiveness benefits? It turns out, an additional £24.77 and £15.17 per hour were incurred to avoid moderate to severe pain in the PCA group in traumatic and non-traumatic abdominal pain groups respectively. This was spent on a range of additional tasks and equipment that was not seen in the standard care group (Figure 1).Figure 1. PCA Costs

Figure 1. Time and staff costs for patient-controlled analgesia and standard care groups per participant during the 12-h study period. Values are mean (SD)

The question of whether these costs represent value for money, and a more philosophical approach to this evaluation was published in an accompanying editorial by Doleman and Smith. They argue that choosing a cut off VAS of ≥45 arbitrarily puts patients with a VAS of 44 and 46 in separate severity of pain categories, which might invalidate the economic evaluation. Additionally, they followed up on the baseline data reported by Pritchard et al and found that the usual care group had higher pain scores than the PCA group. Moreover, Doleman and Smith ask an invaluable question: is the choice of outcome measure (VAS) looked at really that important? If not, which outcomes are actually important? Despite some interesting criticism of the study, I think it is safe to say that the unique methodology taken by Pritchard et al is worthy of reviewing and applying in similar studies in the future.

 

Speaking of novel pain management research, Lyngeraa et al report a randomised, double-blind pilot study of a novel ‘suture-method’ peripheral nerve catheter. It consists of a curved suture needle, a needle hub, and a catheter that can be placed under ultrasound-guidance in close proximity to a target nerve, with the distal end of the catheter emerging at a distal site (Figure 2). Figure 2..png

Figure 2. The suture-method catheter. Left: The suture-catheter device. N, needle; H, hub; and C, catheter. Right: The suture-method catheter during insertion. The needle has been inserted past the nerve to exit the skin on the other side of the nerve

 

The idea behind this technique is that catheters might be easier to insert in the appropriate position and should displace less than traditionally sited catheters. Sixteen volunteers had bilateral ultrasound-guided sciatic nerve catheters placed with the suture-method catheter system, and were randomised to receive either local anaesthetic or saline in each leg. They reported a 94% success rate in the initial catheter placement, but only three-quarters were still effective after vigorous physical exercise. The study authors argue that the novel suture-needle design is as effective as other techniques, and speculate that it might be more secure due to the double skin penetration anchoring, whilst reducing local anaesthetic leakage as the catheter is the same diameter as the placement needle. They also suggest that it might be easier to insert and see on ultrasound than traditional catheter techniques.

 

Of course, they have little data to truly support their claims of superiority of the suture-needle catheter, argues Fredrickson. This design necessitates a more invasive insertion, catheter placement tangential to nerves, extra steps to catheter insertion, and technical challenges to inserting a curved needle, all of which are significant drawbacks of this design. Additionally, Fredrickson’s group often insert ambulatory catheters that patients can remove themselves at home, a strategy that would be impossible to achieve with the suture-needle system as it needs medical expertise to remove. Traditional catheter techniques, argues Fredrickson, are currently superior and should be increasingly used in clinical practice. Of course, some experts believe that there is no role for catheters at all in management of perioperative pain – but that is a discussion for a different day.

 

Our next pain study in this issue of the Journal comes from Holmberg et al, who compared the effectiveness of a pre-operative vs post-operative analgesic infraclavicular brachial plexus block in 52 patients having radial fracture fixation surgery. Patients were randomised, and the time to first rescue analgesia after emergence from general anaesthesia, as well as pain scores, rescue analgesia, and plasma stress markers. Surprisingly, patients who had the pre-operative blocks requested rescue analgesia on average more than three-hours later than those who had the post-operative blocks, and their absence of sensory and motor function lasted an hour longer (Figure 3).

Figure 3..png

Figure 3. Kaplan-Meier curve showing the proportion of patients in each group not requiring opioid rescue analgesia. Red line, pre-operative block group; blue line, postoperative block group

Moreover, they had lower pain scores up to four hours after surgery, and lower analgesic consumption in the first post-operative week. However, there was no difference in ‘strong pain’ after block resolution, stress markers, and chronic pain between pre-operative and post-operative block groups. Overall, Holmberg et al have elegantly demonstrated the potential for pre-emptive regional analgesia to attenuate short-term pain.

 

Our final pain study was an interesting Cochrane systematic review assessing the analgesic efficacy of remifentanil patient-controlled analgesia (PCA) vs other parenteral analgesic strategies in labour. Jelting et al sought relevant randomised, controlled, and cluster-randomised trials reporting patient satisfaction with pain relief and adverse events. Twenty studies informed their analysis, although the outcomes they sought were poorly reported. When compared to other parenteral opioids, remifentanil PCA demonstrated superior satisfaction, but inferior patient satisfaction to epidural analgesia. There was not much to show for the difference in respiratory depression, nor low Apgar scores between remifentanil PCA and epidural analgesia. However, the authors attributed low or very low quality of evidence to most of the reported results. Does this tell us that we just don’t know yet?

 

The August issue of the Journal also sports some remarkable other studies. Did you know that we might be over-estimating the size of the cricothyroid membrane for emergency front of neck access? A size 6.0mm tube could just be too big – as we discovered in our recent TweetChat on the subject. We might also be over-nihilistic when considering surgery for patients with fractured necks of femur – are survival rates better than we think? What do you know about ventilation for lung transplant, or 3D-printed bronchoscopy simulators? These and more can be found in our August issue – I couldn’t put it down!

 

Kariem El-Boghdadly

Anaesthesia Fellow

Andrew Klein

Anaesthesia Editor-in-Chief

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New Blood, Old Money

“Blood alone moves the wheels of history” — Benito Mussolini

 

We often assume what we were always taught must always be true. But what if it’s not? What if we make efforts to go beyond dogma and do things differently; understand things differently? July’s issue of Anaesthesia might just encourage readers to do that by publishing work on anaemia, laryngoscopy grading, and more.

 

Haemoglobin is the vehicle that helps to keep us alive, and surgery is an insult that may remove that vehicle. But do we know enough about pre-operative anaemia and iron deficiency to optimise the vehicle? In this month’s issue of Anaesthesia, Muñoz and colleagues presented a retrospective cohort study of five centres in Spain addressing precisely this question. They assessed data from more than 3000 patients undergoing a range of surgical procedures in which the underlying pathology predisposes to anaemia, has an expected risk of > 500 ml blood loss, and/or has a > 10% transfusion risk. They found that one third of patients were anaemic (Hb < 130 g.l-1), of which two-thirds had either iron deficiency or iron sequestration, and, perhaps unsurprisingly, two thirds of anaemic patients were women. Notably, 62% of anaemic patients had absolute iron deficiency, but half of non-anaemic patients were iron deficient or had low iron stores. They took this information and incorporated the recently published game-changing international consensus statement on anaemia management to suggest management for different scenarios pertaining to iron deficiency (Fig. 1).

July_fig1.png

 

Figure 1. Patients’ classification, according to pre-operative haemoglobin levels and iron status, and *suggested actions to be taken, as per a recent international consensus statement. Absolute iron deficiency defined by ferritin < 30 μm.l−1 or ferritin 30–100 μm.l−1, plus transferrin saturation < 20% and/or C-reactive protein > 5 mg.l−1; iron sequestration defined by ferritin > 100 μm.l−1, plus transferrin saturation < 20% and/or C-reactive protein > 5 mg.l−1; low iron stores defined by ferritin 30–100 μm.l−1, plus transferrin saturation > 20%.

 

This data was accompanied by a thought-provoking editorial by Butcher et al, who looked at the findings from a different perspective. Butcher et al. suggest that, as women generally have smaller circulating blood volumes than men, the same peri-operative blood loss would have a significantly larger effect on the former than the latter. Compounding this, we have long accepted that anaemia in women is defined by a lower Hb than that for men, and therefore females are more likely to require transfusion. This is a curious paradox, one which has received little consideration in the past. However, Butcher and colleagues point to Muñoz’s data as a demonstration that, if target Hb concentrations are the same between men and women, the latter are far more likely to be anaemic. It is imperative, therefore, that we readjust our age-old targets, and consider changing the arbitrary cut-offs of to 130 g.l-1, irrespective of sex. This novel thinking is likely to drive a significant amount of research in the future, and could perhaps increase the safety of patient management, no matter the gender.

 

O’Loughlin et al have assessed a question that many haven’t asked: what scoring system should to describe glottic visualisation at videolaryngoscopy? The authors compared the age-old Cormack and Lehane score (published in Anaesthesia just 35 years ago), the percentage of glottic opening (POGO) score, and the authors’ very own Fremantle score. As a quick reminder, the POGO score is an estimate of the percentage of the glottic inlet that is seen on laryngoscopy, and the Freemantle score is the three-component composite describing the view, the ease of intubation and the device use for intubation. The authors showed 20 videolaryngoscopic intubation videos to 74 critical care physicians, and compared accuracy with an expert panel assessment, as well as assessing intra- and inter-rater reliability. They found that the POGO and Fremantle score are superior to the Cormack and Lehane score in the outcomes assessed. However, O’Loughlin et al go one step further and suggest that, because their Freemantle score provides additional information about the ease of intubation, this should be the go-to scoring system. Of course, few anaesthetists in the UK apply this scoring system, and ultimately the reason to describe the view at laryngoscopy is for communication. The next question should be: does the Fremantle score improve communication enough to drop the tried and tested Cormak and Lehane score?

 

This issue of the Journal next takes us to a simple, yet novel method for determining the location of epidural needle placement using continues pressure wave-form monitoring. By attaching extension tubing attached to a pressure transducer to epidural needles, pulsatile waveforms synchronised with heart rate represent epidural placement (fig. 2). 93% of patients who had effective epidural block also had a clear epidural pressure waveform on transduction. This technique thus provides, in the authors words, a ‘simple adjunct to loss-of-resistance for identification of needle placement.’ Of course, can you imagine the challenge in routinely locating a transducer set, appropriate monitor, whilst meeting 30 minute to attendance for epidural placement limit that many departments work towards? Neither can McKendry and Muchatuta, who question the necessity for this technique in the obstetric environment, and suggest that not only should other techniques be explored, but one should always consider that problems with regional anaesthesia techniques might be addressed by ‘looking for the cause on the proximal end of the needle.’ So let’s work out how best to improve our technique!

 

July_Fig2

Figure 2. An example of a typical pulsatile waveform, synchronous with the arterial pressure trace, recorded from a correctly located epidural needle. Top trace–intra-arterial pressure; middle trace (labelled CVP)–epidural space pressure; bottom trace–pulse oximeter waveform.

 

Novelty is abound, and Leong et al have presented a vital signs-controlled remifentanil PCA technique.  By programming a PCA device to act based on feedback from vital signs, the authors demonstrated a reduction in adverse events. Scholten et al published an exciting systematic review of novel techniques to assist with needle tip identification during ultrasound-guided procedures. They summarise the data on needle guides (including lasers!), needle tip design, 3D and 4D ultrasound, magnetism, robots and more. The challenges of regional anaesthesia might be overcome by the plethora of technological advances. Feng, Liao and Huang demonstrated that internal iliac artery balloon catheters might not be as effective for placenta accreta than we once thought; Flubacher et al demonstrated what we probably know about the efficacy of ondansetron as an anti-emetic; and Brix and colleagues found that day surgery does not always mean single day care episodes.

 

That was our whistlestop tour of the July issue of the Journal, but much more can be found between the covers that is sure to excite, entice and enlighten all who read it!

 

Kariem El-Boghdadly

Trainee Fellow, Anaesthesia

Andrew Klein

Editor-in-Chief

 

Post art: Kariem El-Boghdadly