Đang tải... (xem toàn văn)
(BQ) Part 2 book Improvised medicine providing care in extreme environments presents the following contents: Circulation/cardiovascular, dehydration/rehydration, medications pharmacy/envenomations, anesthesia—local and regional, sedation and general anesthesia, surgical interventions
10 Circulation/ Cardiovascular Few improvised methods are available for diagnosing and treating cardiovascular abnormalities The most basic treatment, cardiopulmonary resuscitation (CPR), can be performed without extra equipment However, not even MacGyver would really be willing to try cardioversion without a defibrillator, and the most basic treatments used for cardiovascular care require at least certain medications and equipment DIAGNOSIS: ELECTROCARDIOGRAM No Calipers To measure electrocardiogram (ECG) intervals without calipers, mark a card or piece of paper with vertical lines: | | | | | | | | | The marks can be spaced to match the top of the R or the P waves, depending on what you are looking for Move the marks to another part of the ECG to determine if the rates are constant or to find a P wave hidden in a QRS complex Alternate Electrocardiogram Positions and Leads If there is no room to lay a patient down, the ECG with the patient in a standing position (Fig 10-1) The resulting ECG is just as interpretable as one done in a supine position Attaching Electrocardiogram Leads If an ECG or a cardiac monitor is available, but the way of attaching the leads to the patient is missing, several methods work well The key is to pull off any device hiding the bare metal leads (that usually are covered by devices that attach to tape leads on Western ECG machines) After removal, place the leads directly on small alcohol or saline pads or a lubricant (oil, K-Y jelly) FIG 10-1 Standing ECG with improvised leads 150 10 Cir Cu l a t io n /Ca r d io va s Cu l a r 151 FIG 10-2 Electrocardiogram leads attached using a variety of improvised methods between the skin and the lead, but that is not essential to obtain a good ECG reading Affix them in the normal locations using phlebotomy tourniquets If chest leads are needed, place these on the skin in the same manner, using tape to temporarily secure them If they must be kept on for some time or if the patient has injuries (e.g., burns) precluding the use of tape, insert small-gauge needles just beneath the epidermis and use alligator clips to make a connection (Fig 10-2) “12-Lead”Electrocardiogram Using Leads Normal 12-lead ECG machines may not be available when additional ECG information is needed for a diagnosis In this situation, clinicians can use a 3-lead machine to obtain an ECG tracing that produces most of the information provided by a 12-lead ECG To this, a tracing with the ECG pads placed in the normal 3-lead positions: White = right chest just below the clavicle Black = left chest just below the clavicle Red = left lower abdomen just above the umbilicus Then, four more tracings, each time moving the red (left leg) lead to the V1, V2, V3, or V6 positions (Fig 10-3).1 Many monitors can also show leads II, III, aVL, aVR, and aVF by moving a dial on the machine with the leads kept in their normal position Improve ECG Diagnostic Accuracy Standard ECG machines run at 25 mm/second Doubling the paper output speed to 50 mm/second makes subtle ECG findings more evident and improves diagnostic accuracy of narrow complex tachycardias A way to visualize this is to think about stretching the ECG tracing like a rubber band One group of physicians improved their diagnostic accuracy from 63% at the standard rate to 71% with the faster tracings Also, inappropriate use of adenosine decreased from 18% to 13% Everything, including the QRS complex and intervals, gets wider.2 Measure Central Venous Pressure Both the catheters and the manometers used for central venous pressure (CVP) monitoring are disposable, but, if necessary, they can be boiled (disinfected) and reused The danger in reusing catheters is that particulate matter may remain within them, so the disinfection may not be effective.3 152 Pa t iEn t a s s Es s MEn t /s t a Bil iZa t io n FIG 10-3 A normal ECG (I, V1, V2, V3, V6) done using only the three leads from a monitor The additional limb lead tracings taken by changing settings on the monitor are not shown The “normal” tracing is lead I, although on most machines it also can tracings of the other limb leads For measuring CVP, attach a manometer to either a three-way stopcock or a sterile “Y” tube Construct a manometer from another intravenous set taped over or beside an upright ruler or cardboard marked in centimeter increments Fill the manometer from the intravenous bottle and then connect it via a central line to the patient Any drip going through the line is stopped The zero point is the mid-axillary line, with the patient in a supine position.4 (The normal reading is 5-10 cm H2O.) To be accurate, the zero (“0”) mark on the CVP manometer must be level with the supine patient’s mid-axillary line Use a long piece of wood with a level taped on top, so you can check that it is parallel with the floor Place one end of the wood at the patient’s mid-axillary line and, while watching the level, attach the CVP manometer to an intravenous (IV) pole so that the zero (“0”) is even with the wood’s other end An alternative is to use a piece of IV tubing that has been half-filled with colored water and then formed into a loop by connecting the two ends The two menisci (where the water meets the air) in the tube will always be at the same level if the loop is held vertically Figure 10-4 illustrates how to use such a tube to adjust the manometer height.3 Pulmonary Embolism Diagnosis Even if you cannot calculate the probability of a patient having a pulmonary embolus (PE) using one of the standard clinical decision rules (Wells and revised Geneva scores), your gestalt assessment will be sufficient In fact, physicians’ gestalt assessment is better at selecting patients with a low or high probability of PE than are the scoring systems.5 TREATMENT Paroxysmal Supraventricular Tachycardia The simplest and most available method to convert paroxysmal supraventricular tachycardia (PSVT) is to use vagal maneuvers However, if the patient is unstable, cardiovert immediately if 10 Cir Cu l a t io n /Ca r d io va s Cu l a r 153 FIG 10-4 Makeshift CVP monitor with leveling loop that option is available If using paddles, make contact with the patient using either saline pads or the same gels that are used for ultrasound examinations Valsalva Maneuvers The Valsalva maneuver (VM), bearing down against a closed glottis, is the most consistently effective vagotonic technique Optimize the VM by placing the patient in a supine position, which generates greater vagal tone than Trendelenburg posturing This position produces the largest transient heart rate decrease Its efficacy can be increased further by pressing firmly over the right hypochondrium (over the liver) while the patient exhales and bears down This increases venous return to the right side of the heart and augments the effect on cardiac stretch receptors, thereby increasing the chance of successfully terminating the arrhythmia.6 Older Vagal Stimulation Methods Other useful vagal maneuvers include blowing into a tube connected to a sphygmomanometer for 15 seconds to achieve a pressure of 40 mm Hg and stimulating the human dive reflex by applying a cold pack to a patient’s face for 30 seconds.7 Stimulating the diving reflex works best on children Ask children who are old enough to cooperate to hold their breath and dunk their face into a pan of ice water resting on their lap Do not force their head into the water or hold it under! For younger children, have a parent hold a towel that has been dipped in ice water over the child’s face Be sure to keep the airway clear Pressor drugs can occasionally terminate atrioventricular (AV) nodal reentry by inducing reflex vagal stimulation mediated by baroreceptors in the carotid sinus and aorta This requires the systolic blood pressure (BP) to be elevated to about 180 mm Hg, and so should be used carefully or not at all in the elderly and in patients who have structural heart disease, significant hypertension, hyperthyroidism, or an acute myocardial infarction Given over to minutes, the adult doses for these agents are phenylephrine 1%, (0.1 mL) to 10 mg (1 mL); methoxamine, to mg; or metaraminol, 0.5 to 2.0 mg If edrophonium is used, administer it over 15 to 30 seconds—it is very short acting 154 Pa t iEn t a s s Es s MEn t /s t a Bil iZa t io n Adenosine Dosing Simplified The advanced cardiovascular life support (ACLS)-recommended dosing strategy of 6, 12, and 12 mg for adenosine may not be appropriate in every situation Caffeine is an adenosine blocker and can interfere with the successful reversion of PSVT In fact, ingestion of caffeine 1 mL/kg/hr, and non-cyanotic skin color Among survivors, 156 Pa t iEn t a s s Es s MEn t /s t a Bil iZa t io n those most likely to have a good neurologic outcome had initial Glasgow Coma Score (GCS) scores >7.26 Hypothermia after Return of Spontaneous Circulation Therapeutic hypothermia after return of spontaneous circulation (ROSC) improves survival and neurologic outcomes, especially in patients presenting with shockable rhythms (ventricular fibrillation/pulseless ventricular tachycardia) Both infusing cold intravenous fluids and surface cooling have been used successfully, although, with the latter, there is more temperature variation during the maintenance phase The optimal desired temperature is still unclear, but it seems to be less important than preventing the patient from becoming hyperthermic Most clinicians attempt to get their patients to a core temperature of 32°C to 36°C (89.6°F to 96.8°F) The prehospital sector has also had success with induced hypothermia, both during resuscitation and after ROSC Methods to induce hypothermia in both settings include infusing ice-cold IV fluids (500 mL to 30 mL/kg of 0.9% saline or Ringer’s lactate) and applying surface cold packs or cooling blankets Whenever possible during the cooling process, monitor core temperature using an esophageal thermometer or a bladder catheter temperature probe Axillary and oral temperatures are inadequate Continue induced hypothermia for 12 to 24 hours, or until the patient awakens.27 Disinfecting Cardiopulmonary Resuscitation Manikins Manikins are used throughout the world to teach CPR To prevent a possible transmission of herpes simplex virus and other pathogens among those who share manikins for mouth-to-mouth resuscitation training, disinfect the manikin’s contact surfaces at the end of each class To this, wet all surfaces with a 500 ppm sodium hypochlorite (bleach) solution, leave it on for 10 minutes, rinse with fresh water, and immediately dry Between students or after the instructor demonstrates a procedure, wipe the face and interior of the manikin’s mouth with 500 ppm hypochlorite solution or 70% alcohol.28 REFERENCES Personal communication and testing with Capt Shelley Metcalf, RN, USAF, McMurdo Station, Antarctica, September 2009 Accardi AJ, Miller R, Holmes JF Enhanced diagnosis of narrow complex tachycardias with increased electrocardiograph speed J Emerg Med February 2002;22(2):123-126 King MH, ed Primary Anesthesia Oxford, UK: Oxford University Press; 1986:142 Eggleston FC Simplified management of fluid and electrolyte problems Trop Doct 1985;15:111-117 Penaloza A, Verschuren F, Meyer G, et al Comparison of the unstructured clinician gestalt, the Wells Score, and the Revised Geneva Score to estimate pretest probability for suspected pulmonary embolism Ann Emerg Med 2013;62:117-124 Mitchell ARJ Augmented Valsalva’s maneuver terminates tachycardia Postgrad Med www.postgradmed com/pearls.htm Accessed September 23, 2007 Smith G, Broek A, Taylor DM, Morgans A, Cameron P Identification of the optimum vagal manoeuvre technique for maximising vagal tone Emerg Med J 2015;32:51-54 (online June 5, 2014) Cabalag MS, Taylor DM, Knott, JC, et al Recent caffeine ingestion reduces adenosine efficacy in the treatment of paroxysmal supraventricular tachycardia Acad Emerg Med 2010;17(1):44-49 Neumar RW, Otto CW, Link MS, et al Part 8: adult advanced cardiovascular life support: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Circulation 2010;122(18 suppl 3):S729-S767 10 Choi SC, Yoon SK, Kim GW, et al A convenient method of adenosine administration for paroxysmal supraventricular tachycardia J Korean Soc Emerg Med 2003;14(3):224-227 11 Habak PA, Mark AL, Kioschos JM, et al Effectiveness of congesting cuffs (“rotating tourniquets”) in patients with left heart failure Circulation 1974;50;366-371 12 Bertel O, Steiner A Rotating tourniquets not work in acute congestive heart failure and pulmonary edema Lancet 1980;8:171:762 13 Roth A, Hochenberg M, Keren G, et al Are rotating tourniquets useful for left ventricular preload reduction in patients with acute myocardial infarction and heart failure? Ann Emerg Med 1987;16:764-767 10 Cir Cu l a t io n /Ca r d io va s Cu l a r 157 14 Taylor R, Spencer TR Intraosseous administration of thrombolytics for pulmonary embolism J Emerg Med 2013;45(6):e197-e200 15 Yu GV, Schubert EK, Khoury WE The Jones compression bandage Review and clinical applications J Am Podiatr Med Assoc 2002;92(4):221-231 16 Orkin AM Push hard, push fast, if you’re downtown: a citation review of urban-centrism in American and European basic life support guidelines Scand J Trauma Resusc Emerg Med 2013;21:32 17 Birkenes TS, Myklebust H, Kramer-Johansen J New pre-arrival instructions can avoid abdominal hand placement for chest compressions Scand J Trauma Resusc Emerg Med 2013;21:47 18 Birkenes TS, Myklebust H, Kramer-Johansen J Time delays and capability of elderly to activate speaker function for continuous telephone CPR Scand J Trauma Resusc Emerg Med 2013;21:40 19 Tar C Can metronomes improve CPR quality? Emerg Med J 2014;31(3):251-254 20 Park SO, Hong CK, Shin DH, Lee JH, Hwang SY Efficacy of metronome sound guidance via a phone speaker during dispatcher-assisted compression-only cardiopulmonary resuscitation by an untrained layperson: a randomised controlled simulation study using a manikin Emerg Med J 2013;30:657-661 21 You JS, Chung SP, Chang CH, et al Effects of flashlight guidance on chest compression performance in cardiopulmonary resuscitation in a noisy environment Emerg Med J 2013;30:628-632 22 Cohn B Does the absence of cardiac activity on ultrasonography predict failed resuscitation in cardiac arrest? Ann Emerg Med 2013;62(2):180-181 23 Krikscionaitiene A, Stasaitis K, Dambrauskiene M, et al Can lightweight rescuers adequately perform CPR according to 2010 resuscitation guideline requirements? Emerg Med J 2013;30:159-160 24 Hong CK, Park SO, Jeong HH, et al The most effective rescuer’s position for cardiopulmonary resuscitation provided to patients on beds: a randomized, controlled, crossover mannequin study J Emerg Med 2014;46(5):643-649 25 McDonald CH, Heggie J, Jones CM, Thorne CJ, Hulme J Rescuer fatigue under the 2010 ERC guidelines, and its effect on cardiopulmonary resuscitation (CPR) performance Emerg Med J 2013;30: 623-627 26 Lin YR, Wu HP, Chen WL, et al Predictors of survival and neurologic outcomes in children with traumatic out-of-hospital cardiac arrest during the early postresuscitative period J Trauma Acute Care Surg 2013;75:439-447 27 Peberdy MA, Callaway CW, Neumar RW, et al Part 9: post-cardiac arrest care: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Circulation 2010 Nov;122(18 suppl 3):S768-S786 28 Rutala WA, Weber DJ Uses of inorganic hypochlorite (bleach) in health-care facilities Clin Microbiol Rev 1997;10(4):597-610 11 Dehydration/ Rehydration Sir William MacGregor, MD, at the end of his term as Papua New Guinea’s colonial governor, wrote: “Dysentery causes more deaths than any other disease in tropical countries No other malady is so universally distributed and of such constant occurrence … [Dysentery has become] the chief agent in the rapid depopulation of the Pacific.”1 Rehydration does not have the drama of other medical interventions—but it saves more lives than all other disease treatments combined ASSESSMENT Diarrhea Diarrhea causes most cases of lethal dehydration, especially among infants and children Acute diarrhea is three or more loose or watery stools per day or a definite decrease in stool consistency and an increase in stool frequency for the individual The volume of fluid lost through stools can vary from mL/kg body weight/day (approximately normal) to ≥200 mL/kg body weight/day.2 Because of the use of oral rehydration therapy (ORT), the annual worldwide deaths from diarrhea have decreased from >5 million in 1978 to 2.6 million in 2009 (1.1 million people >5 years old and 1.5 million children