Aneasthesia Pearls July 2014

ANAESTHESIA PEARLS

DIGITAL NERVE BLOCKS AND ADRENALINE

DIGITAL NERVE BLOCKS AND ADRENALINE
NAESTHETIC CONSIDERATION IN AIDS PATIENTS
This age old myth has been taught over the generations, handed down from from medical eminence to medical students & junior doctors alike.
Where it Came From
Several publications of case reports in the 1940s cited digital nerve blocks with epinephrine as a cause for gangrene of the finger in the post-op period. This was further propagated in the surgical texts of the day (see references below).
It is widely accepted now that the actual cause of the gangrene was thermal injury secondary to boiling hot soaks in boric acid solution post-operatively, which was recommended practice back in the day.
Current evidence
Numerous reviews have examined this – most recently this study by Chowdhry et al in the December 2010 edition of the journal of Plastic and Reconstructive Surgery :
BACKGROUND:
Epinephrine in digital blocks has been condemned by traditional medical theory. The authors provide a retrospective review of 1111 cases involving digital block anesthesia with epinephrine in conjunction with an extensive literature review.
METHODS:
The authors conducted a retrospective review of 1111 cases involving digital and hand surgery. Observations were made concerning the location of and indication for surgery, age, sex, type of block used, type and dose of anesthetic, use of epinephrine and concentration, use of a tourniquet, follow-up, and complications. Dorsal and transthecal techniques were used exclusively. Patients with vascular compromise did not receive epinephrine and were excluded from the study.
RESULTS:
One thousand one hundred eleven cases were reviewed, distributed among 692 male patients and 419 female patients. Sites of surgery ranged throughout the hand and all fingers for a variety of indications. Five hundred patients received injections of 1% plain lidocaine with a dosage range of 2 to 10 cc and an average of 5.7 cc. Six hundred eleven patients received injections of 1% lidocaine with epinephrine (1:100,000) in a dose range of 0.5 to 10 cc and an average dose of 4.33 cc. Nine hundred eighty-six patients (88.75 percent) followed up in the clinic. No patients suffered from digital gangrene in the epinephrine group.
CONCLUSIONS:
After reviewing 1111 cases, there were no complications associated with the use of epinephrine in digital blocks. The authors suggest that correct application of epinephrine in digital blocks is appropriate, and defend its use.
Ref: Plast Reconstr Surg. 2010 Dec;126(6):2031-4.
The following caveats apply:
Digital blocks may be contraindicated in patients with disease processes involving the digital vessels at the base of the proximal phalanx
Adrenaline / epinephrine should be used cautiously in patients wth known cardiac disease, hypertension & peripheral vascular disease.
Source:
Myth Buster Episode 3 – Digital Nerve blocks and adrenaline / epinephrine. ED Trauma Critical Care Blog.
References :
Plast Reconstr Surg. 2010 Dec;126(6):2031-4.
Kaufman, P. A. Gangrene following digital nerve block anesthesia. Arch. Surg. 42: 929, 1941.
McLaughlin, C. W., Jr. Postoperative gangrene of the finger following digital nerve block anesthesia. Am. J. Surg. 55: 588, 1942.
O’Neill, E. E., and Byrne, J. J. Gangrene of the finger following digital nerve block. Am. J. Surg. 64: 80, 1944.
Bunnell, S. Surgery of the Hand, 1st Ed. London: Lippin- cott, 1944. Pp. 100–105.

Devices to Support Circulation

Devices to Support Circulation in CPR
Over the past 25 years a variety of alternatives to conventional manual CPR have been developed in an effort to enhance perfusion during attempted resuscitation from cardiac arrest and to improve survival. Compared with conventional CPR, these techniques and devices typically require more personnel, training, and equipment, or they apply to a specific setting. Application of these devices has the potential to delay or interrupt CPR, so rescuers should be trained to minimize any interruption of chest compressions or defibrillation and should be retrained as needed. Efficacy for some techniques and devices has been reported in selected settings and patient conditions; however, no alternative technique or device in routine use has consistently been shown to be superior to conventional CPR for out-of-hospital basic life support.
Devices to Support Circulation
Active Compression-Decompression CPR
Active compression-decompression CPR (ACD-CPR) is performed with a device that includes a suction cup to actively lift the anterior chest during decompression. The application of external negative suction during the decompression phase of CPR creates negative intrathoracic pressure and thus potentially enhances venous return to the heart. When used, the device is positioned at midsternum on the chest.
Phased Thoracic-Abdominal Compression-Decompression CPR With a Handheld Device
Phased thoracic-abdominal compression-decompression CPR (PTACD-CPR) combines the concepts of IAC-CPR and ACD-CPR. A handheld device alternates chest compression and abdominal decompression with chest decompression and abdominal compression.
Impedance Threshold Device
The impedance threshold device (ITD) is a pressure-sensitive valve that is attached to an endotracheal tube, supraglottic airway, or face mask. The ITD limits air entry into the lungs during the decompression phase of CPR, creating negative intrathoracic pressure and improving venous return to the heart and cardiac output during CPR. It does so without impeding positive pressure ventilation or passive exhalation.
The ResQPOD impedance threshold device
It is an impedance threshold device (ITD) that provides Perfusion on Demand (POD) by regulating pressures in the thorax during states of hypotension. Originally, the ITD was used with a cuffed endotracheal tube during bag-tube ventilation and ACD-CPR.
ResQGARD impedance threshold device
ResVENT impedance threshold device
Mechanical Piston Devices
A mechanical piston device consists of a compressed gas- or electric-powered plunger mounted on a backboard; it is used to depress the sternum. Some incorporate a suction cup in the piston device while others do not.
The Lund University Cardiac Arrest System (LUCAS) is a gas- (oxygen or air) or electric-powered piston device that produces a consistent chest compression rate and depth. It incorporates a suction cup attached to the sternum that returns the sternum to the starting position. There are no randomized control trials comparing the device with conventional CPR in human cardiac arrests.
Gas powered LUCAS Electric-powered LUCAS
Load-Distributing Band CPR or Vest CPR
The load-distributing band (LDB) is a circumferential chest compression device composed of a pneumatically or electrically actuated constricting band and backboard.
Ref:
2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science; Part 7: CPR Techniques and Devices, Circulation. 2010; 122: S720-S728

Early Goal Directed Therapy

Early Goal Directed Therapy in Septic Shock (EGDT)
Early Goal Directed Therapy (EGDT) definition
Within 6 hours of presentation to the Emergency Department intensive monitoring of specific circulatory parameters with the aggressive management of 5 key parameters to specified targets to optimise oxygen delivery to tissues.
Parameters
CVP 8-12 mmHg
MAP 65 – 90 mmHg
Urine output >0.5 ml/kg/hr
Mixed venous oxygen saturation >65% / ScvO2 >70%
Haematocrit >30%
Interventions
Reduce work of breathing by early use of mechanical ventilation
Fluid resuscitation
Use of vasoactive agents: noradrenaline, dobutamine
Transfusion
See the Rivers et al, 2001 EGDT protocol
Venous Oximetry – The concept of SvO2 and ScvO2 !
SvO2 >75% Normal extraction O2 supply > O2 demand
75% > SvO2 > 50% Compensatory extraction Increasing O2 demand or decreasing O2 supply
50% > SvO2 > 30% Exhaustion of extraction Beginning of lactic acidosis O2 supply < O2 demand
30% > SvO2 > 25% Severe lactic acidosis
SvO2 < 25% Cellular death
• SvO2 – True mixed venous oxygen saturation
• ScvO2 – Central venous oxygen saturation
RATIONALE
The rationale for EGDT is that early optimization of O2 delivery will improve outcome in sepsis
• Evidence supporting use found by the landmark Rivers Trial (NEJM, 2001) that showed a 16% mortality reduction when ScvO2 monitoring added to standard resuscitation target, although patients in treatment arm received more dobutamine and RBCs transfusion as well.
The principle of applying EGDT for septic shock is based on the observations that:
Early treatment for Myocardial Infarction, Acute Ischaemic Stroke and Trauma improves patient outcomes
Patients presenting to ED with sepsis have measurable O2 deficit
O2 deficit is evidenced by high lactate and high ScvO2
For septic shock the hypothesis is that early optimization of the compromised septic circulation may reduce mortality
ARGUMENTS FOR
sensible end-point for O2 delivery as ScvO2 reflects supply-demand balance
our patients all have CVL in situ (in the ICU, not necessarily in the ED)
Rivers trial showed a substantial reduction in mortality with ScvO2 monitoring vs standard care
no other O2 delivery end point has been validated
recommended in Surviving Sepsis Guidelines
ScvO2 readily available
ScvO2 can have continuous monitoring
ScvO2 responds to therapy
ScvO2 is predictive of outcomes
ARGUMENTS AGAINST
Protocols for implementing EGDT usually result in more fluid being administered, more use of vasoactive medication and more use of blood transfusion which may lead to:
Fluid overload (e.g. APO, abdominal compartment syndrome, edematous tissues impedding oxygen flux to cells)
Arrhythmias and myocardial necrosis from inotropes
Adverse effects of blood transfusion
Effects of excessive oxygen delivery
End-points (which parameter, and which value) are numerous and essentially arbitrary
PCWP
CVP
systolic pulse pressure variation
pulse pressure variation
stroke volume variation
MAP
HR
SVRI
Q
SV
SpO2
Hb/HCT
DO2
GEDV
EVLW
ITLV
urine output
serum lactate
Endpoints based on cardiac output and other macrovascular parameters may not be very important
macrovascular flow doesn’t mean microvascular flow
changes in sepsis (microvascular thrombi with endothelial dysfunction)
impaired autoregulation
microflow is linked to outcomes
microflow can be manipulated (dobutamine)
Proscriptive targets may not suit all (eg higher MAP needed for elderly patients, lower MAP and Hct targets for young, fit patients)
EVIDENCE
Limitations of Rivers study include the following:
Study population limited to ED presentations and did not include ward patients
Single centre
Non-blinded
Control group had an above-average mortality rate and patients had high rates of comorbidities
‘Rivers effect’ (undivided attention of a critical care trained doctor in the intervention arm)
Unclear which interventions are most important – whole EGDT protocol or one single component
Target parameters are restrictive
Use of ScvO2 and pressure monitoring has not been tested in the target population
Transfusion target to improve DO2 contradicts restrictive transfusion practice and may be associated with increased mortality in the critically ill
Other approaches
there is clear evidence from meta-analysis(Jones et al, 2008) that quantitative resuscitation within 24 hours, including approaches other than EGDT, improve mortality
targeting lactate clearance is non-inferior to EGDT Jones et al, 2010)
Results of Australasian ARISE and related international studies (US ProCESS and UK ProMISE) Awaited
AN APPROACH
start early
optimize filling (dynamic tests of Starling curve: fluid responsiveness, swing)
best fluid controversial (not HES!)
optimise O2 carrying capacity
optimise oxygenation
optimize haemodynamics
augment contractility
can titrate to an end-point (ScvO2 or lactate) but it may not matter
await further higher quality evidence (e.g. ARISE, PROMISE and PROCESS)
We don’t use continuous ScVO2 monitoring
OXYGEN DELIVERY AND EXTRACTION
Oxygen delivery is determined by the content of the blood and cardiac output:
PaO2 (PAO2, PaCO2, RQ, atmospheric pressure, K)
SpO2
Hb (affinity of Hb for O2)
Q
Mechanisms that sustain oxygen flux
increased oxygen delivery (reflex mechanisms, redirection to essential organs)
increased extraction ratio
reduced VO2 (oxygen conservation behaviours)
anaerobic metabolism
regional variations
chronic adaptation
Predicting microvascular flow
clinical examination
haemodynamics
cardiac output based
clinical ‘tissue perfusion’ indicators
lactate
sublingual capillary flow
SmvO2
ScvO2
O2 extraction ratio
central-toe temperature gradient
gastric tonometry
ScvO2
higher extraction suggest stress
< 40-50% implies tissue dysoxia (high extraction)
samples upper body venous return largely
predictive of post op complications and mortality
suggested target: 65-70%
Processing new results in early goal-directed therapy of sepsis
The single center, randomized 263-patient Rivers study protocolized EGDT versus usual care in sepsis, back in 2001 had a huge impact around the world.
This study published more than a decade ago involving patients presenting to the emergency department with severe sepsis and septic shock, mortality was markedly lower among those who were treated according to a 6-hour protocol of early goal-directed therapy (EGDT), in which intravenous fluids, vasopressors, inotropes, and blood transfusions were adjusted to reach central hemodynamic targets, than among those receiving usual care. The ProCESS Investigators conducted a trial to determine whether these findings were generalizable and whether all aspects of the protocol were necessary.
Ref: A Randomized Trial of Protocol-Based Care for Early Septic Shock. N Engl J Med 2014; 370:1683-1693,May 1, 2014.
Patient enrollment took place from March 2008 to May 2013, incorporating 31 tertiary US centers. The patient inclusion criteria were essentially identical to the Rivers trial. /td>
In total, 1,341 patients were enrolled in the trial, split between EGDT (439), protocolized standard therapy (446) and usual care (456).
The ProCESS Investigators concluded that for patients presenting with early septic shock, in the setting of prompt recognition, prompt intravenous fluid bolus for hypotension, and prompt intravenous antibiotics, there is no apparent additional benefit of protocol-based resuscitation, mandatory central line placement in all patients, or ScvO2 monitoring, with triggers for blood transfusion and dobutamine.
Source:
Early Goal Directed Therapy in Septic Shock.
References and Links
LITFL
CCC — Central venous oxygen saturation (ScvO2)
CCC — Lactate Clearance vs ScvO2 Monitoring in Severe Sepsis
CCC —SvO2 vs ScvO2
  Journal articles and textbooks
1.Dellinger RP, et al. Surviving Sepsis Campaign: international guidelines for management of severe sepsis and septic shock: 2008. Crit Care Med. 2008 Jan;36(1):296-327. Erratum in: Crit Care Med. 2008 Apr;36(4):1394-6. PubMed PMID: 18158437. [Fulltext]
2.Jones AE, Shapiro NI, Trzeciak S, Arnold RC, Claremont HA, Kline JA; Emergency Medicine Shock Research Network (EMShockNet) Investigators. Lactate clearance vs central venous oxygen saturation as goals of early sepsis therapy: a randomized clinical trial. JAMA. 2010 Feb 24;303(8):739-46. PubMed PMID: 20179283; PubMed Central PMCID: PMC2918907.
3.Jones AE, Brown MD, Trzeciak S, Shapiro NI, Garrett JS, Heffner AC, Kline JA; Emergency Medicine Shock Research Network investigators. The effect of a quantitative resuscitation strategy on mortality in patients with sepsis: a meta-analysis. Crit Care Med. 2008 Oct;36(10):2734-9. Review. PubMed PMID: 18766093;PubMed Central PMCID: PMC2737059.
4.McKenna M. Controversy swirls around early goal-directed therapy in sepsis: pioneer defends ground- breaking approach to deadly disease. Ann Emerg Med. 2008 Dec;52(6):651-4. PubMed PMID: 19048659. [Fulltext]
5.Rivers E, Nguyen B, Havstad S, Ressler J, Muzzin A, Knoblich B, Peterson E, Tomlanovich M; Early Goal-Directed Therapy Collaborative Group. Early goal-directed therapy in the treatment of severe sepsis and septic shock. N Engl J Med. 2001 Nov 8;345(19):1368-77. PubMed PMID:11794169. [Fulltext].
FOAM and web resources
1.ALIEM —Paucis Verbis card: Early goal directed therapy
2.EMCrit —Severe Sepsis Resources
3.EMCrit Podcast 14 —EGDT Tirade
4.EMCrit Podcast 14.5 —A bit more on EGDT
5.EMCrit Podcast 22 —Non-Invasive Severe Sepsis Care
6.EP Monthly —Sepsis: EGDT Continues to Deliver versus Sepsis: Unbundling the Bundle (2012)
7.EP Monthly — PRO Should Early Goal-Directed Therapy Be the Standard for Sepsis? versus CON Should Early Goal-Directed Therapy Be the Standard for Sepsis? (2010)
8.Free Emergency Talks —Emanuel Rivers (USA): Lactate Clearance in Severe Sepsis (2012)
9.Free Emergency Talks —Emanuel Rivers (USA): Managing Sepsis in the Resuscitation (2012)
10.Free Emergency Talks — Alan Jones (North Carolina): Optimal Goals of Sepsis (2009)
11.Free Emergency Talks —Early Goal Directed Therapy – Michael Kuiper (2009)
12.Free Emergency Talks — Alan Jones vs Nate Shapiro: Is EGDT the standard of care? (2009)
13.Free Emergency Talks — Peter Greenwald: Early Goal-Directed Therapy in the Community (2010)
14.ICN — Podcast 33: Delaney on EGDT, Surviving sepsis and ARISE
15.PulmCCM.org — Surviving Sepsis Guidelines Updated: Preview from SCCM Meeting
16.PulmCCM.org — Should lactate clearance replace SvO2 in sepsis protocols? (Pro/Con, CHEST)
17.Surviving Sepsis Campaign
Posted in ANAESTHESIA PEARLS 2014

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