Nursing care of patients with Induced Hypothermia Danny Chan NO ICU 24/9/2010

Introduction Numerous studies have been performed in an effort to demonstrate that hypothermia provides neuroprotection to an injured brain, preventing or altering the biological cascade of secondary injury Hyperthermia appears to be detrimental, worsening the degree of injury produced by the primary and secondary injury processes

Introduction (continue) Induced hypothermia can be used to protect the brain from post-ischemic and traumatic neurological injury These side effects can be serious and, if not properly dealt with, may negate some or all of hypothermia’s potential benefits Many of these side effects can be prevented by careful monitoring of fluid balance, tight control of metabolic aspects such as glucose and electrolyte levels, prevention of infectious complications and various other interventions

Introduction (continue) The speed and duration of cooling and rate of re-warming are key factors in determining whether hypothermia will be effective Nurses need to realize hypothermia’s full therapeutic potential will therefore require meticulous attention to the prevention and/or early treatment of side effects, as well as a basic knowledge and understanding of the underlying physiological and pathophysiological mechanisms.

Introduction (continue) Cerebral injury occurs after any condition in which there is inadequate blood flow to the brain for more than 5 min. Cerebral ischemia produces a cascade of effects including ATP energy depletion, ion pump failure, release of free radicals and excitotoxic agents such as glutamate and calcium The formation of free radicals and release of glutamate into the extracellular space are proportional to the intraischemic temperature.

Effects of therapeutic hypothermia retardation of destructive enzymatic reactions suppression of free-radicals reactions reduction of the oxygen demand in low-flow regions reduction of intracellular acidosis inhibition of the biosynthesis, and release and uptake of excitatory neurotransmitters improves oxygen supply to areas of ischemic brain and decreases intracranial pressure (ICP) attenuated the ischemia-induced striatal glutamate and dopamine release during reperfusion, therefore reducing brain damage, ischemic neurons and excitotoxic processes

Non-invasive techniques of therapeutic hypothermia Cooling blankets Air-filled Water-circulating Ice packs Caps of helmets Air-filled Water-circulating Immersion in cold-water Self-adhesive hydrogel-coated cooling pads

Methods of cooling ( Non invasive) External cooling methods: ice packs, cooling blankets, wet towels and cooling helmets simple to use, widely available and may be used in the pre-hospital setting generally slow at reducing core temperature and it is difficult to control the core temperature when the target is reached.

Methods of cooling ( Non invasive) Complications, such as arrhythmias and infection, are more common if the temperature reduces below 30 ℃. Control of re-warming is also difficult.

External cooling methods Gaymar MEDITHERM 3 PATIENT COOLING / REWARMING THERAPEUTIC HYPOTHERMIA unit

Invasive techniques of therapeutic hypothermia Infusion of cold IV fluids Ringer’s lactate/ Saline Retrograde jugular vein flush Extracorporeal circulating cooled blood Cardiopulmonary bypass Femoral-carotid bypass Nasal, nasogastric and rectal lavage Peritoneal lavage with cold exchanges

Methods of cooling (Invasive) Intravascular cooling methods: with heat exchange catheters provides an effective method of reducing body temperature, and maintaining it within the desired range. a closed loop heat exchange device placed in the inferior vena cava, followed by control warming. enables tighter control of core temperature and allows slow, controlled re-warming

Intravascular cooling methods ALSIUS cooling catheter CoolGard 3000® thermal regulation system

Clinical paper Larsson, Wallin & Rubertsson (2010) Cold saline infusion and ice packs alone are effective in inducing and maintaining therapeutic hypothermia after cardiac arrest Resuscitation 81,15-19 Cooling methods Pt was given 4℃ NS IV of 30ml/kg at 100 ml/min via two IV catheters Covered ice packs ( NS infusion bags 250 ml ) applied in groins, axillae and along the neck Change/remove the ice pack PRN to keep core temp. 32-34 ℃ Cooling duration - 24 hr Passive rewarming to 36 ℃ over 8 hr

Discussion cold saline infusion combined with ice packs was found to be effective in inducing and maintaining therapeutic hypothermia and also in controlling rewarming all patients in the study (n = 38) reached the target temperature of 32–34 ◦C, on average 4.4 h from cardiac arrest and 3.4 h after initiation of hypothermia treatment the target temperature remained stable during maintenance of hypothermia treatment with only minor interventions, consisting either of application of ice packs when the temperature started to rise above 33.5 ◦C or removal of the ice packs when it fell below 32.5 ◦C.

Discussion the infusion of cooled saline solution was targeted to a volume of 30 ml/kg and a rate of 100 ml/min to induce hypothermia did not result in any clinical signs of right heart failure or pulmonary oedema in any of the patients cooling below the target temperature range did occur but was not a major problem the temperature was monitored continuously and recorded every 15 min during hypothermia treatment and rewarming the rewarming time was 8.2 h and not exceeding 0.5 ℃/hr additional sedation was given or ice packs re-applied in an effort to prevent too fast rewarming The method is feasible in clinical practice at low cost and should be considered as an alternative to other methods of planned hypothermia treatment

Hypothermia protocols St. Mary’s Hospital Nevada USA Inclusion Criteria -> 18 yrs. -Cardiac arrest with ROSC -Persistent coma with GCS < 9 -BP > or = 90 mmHg Exclusion Criteria -Pregnancy -CPR > 45 min or downtime >10 min -Severe coagulopathy -Other causes of coma

Hypothermia protocols Cooling and rewarming protocals Initiate cooling with iced NS gastric lavage and ice packs on pt’s axilla and groin until cooling blanket started Place the cooling blanket according to instruction Select ‘Manual’ mode on the cooling machine to 5℃ till pt’s core temp to 33 ℃ (will take 3-8 hrs)

Hypothermia protocols Then select ‘Auto’ and set the target temp to 33 ℃ After 24 hrs, rewarm passively to 36.5 ℃ by setting the machine to ‘Manual’ mode and reset unit by increasing target temp by 1℃ every 2-4 hrs Stop all K+ supplement 8 hrs prior to rewarming – prevent rebound hyperkalemia Maintain complete sedation and paralysis as prescribed

Hypothermia protocols BP and Volume management SBP >90 mmHg, MAP >80 mmHg to maintain cerebral perfusion Medication and fluids NS 100 mL/hr Inotropes to maintain MAP> 80 mmHg Stop all K+ administration 8 hrs prior to rewarming

Hypothermia protocols Sedation Titrate Propofol / Midazolam accordingly to BIS reading 40-60 Paralysis Vecuronium to suppress shivering Discontinue paralytic after pt is warmed to 36.5 ℃

Nursing interventions VAP preventive measures DVT prophylaxis PUD prophylaxis Laboratory blood test

Effects of therapeutic hypothermia Hypothermia activates the sympathetic nervous system causing vasoconstriction and shivering. Shivering increases oxygen (O2) consumption by 40-100% which is undesirable in the post hypoxic pt. Hypothermia shifts the oxyhemoglobin curve to the left and may result in decreased O2 delivery.

Effects of therapeutic hypothermia Elderly pts will cool more quickly than younger or obese pts. Initiating paralysis in a pt who is already hypothermia should be avoided -> can result in a precipitous drop in core body temp. Precipitous Done with very great haste and without due deliberation Extremely steep

Effects of therapeutic hypothermia Hypothermia shifts the oxyhemoglobin curve to the left and may result in decreased O2 delivery. However, the metabolic rate is also lowered, decreasing O2 consumption/ carbon dioxide (CO2) production. Ventilator settings may need to be adjusted due to decreased CO2 production, using temperature corrected blood gases.

Effects of therapeutic hypothermia Hypothermia initially causes sinus tachycardia, then bradycardia. 1. Extremely important to keep temp >30ºC. 2. Temperatures: a. <30º C, increased risk for arrhythmias. b. <28º C, increased risk for ventricular fibrillation. Severely hypothermic myocardium (<30°C) is less responsive to defibrillation and medications

Effects of therapeutic hypothermia Hypothermia decreases cardiac output and increases systemic vascular resistance (SVR). Hypothermia can induce coagulopathy which is treatable with platelets and fresh frozen plasma Hypothermia-induced diuresis is to be expected and should be treated aggressively with fluid and electrolyte repletion. Magnesium, phosphorus and potassium should be monitored closely and maintained in the normal range.

Effects of therapeutic hypothermia Decreased insulin secretion and sensitivity leads to hyperglycemia, which should be treated aggressively. Re-warming must proceed slowly over 6-8 hours to prevent vasodilation, hypotension, and rapid fluid and electrolyte shifts.

Complications of Hypothermia Pneumonia Cardiac arrthymias Hypovolemia Electrolyte disorders Insulin resistance Decreased insuline secretion Thrombocytopenia Leukocytopenia Metabolic acidosis Impaired coagulation Shivering Hiccups

Monitoring Goal is to maintain patient’s core temperature between 32° and 34°C for 24 hours. a. If temp < 31° C, consider infusing 250 ml boluses of warm 40°C IV NS or LR until temperature > 32°C. b. Monitor closely for arrhythmias when temperature < 32°C.

Monitoring Hemodynamic Assessment: Continuous SaO2 monitoring Maintain MAP 65-120 mmHg with IV fluids, vasopressors, or nitrates as ordered.

Monitoring Laboratory tests: ABG, RFT, CBC, Clotting, Ca, PO4, Blood glucose Urine output: Hypothermia-induced diuresis is common. Aggressive IV fluid repletion may be required.

Re-warming Begin re-warming 24 hours after target temperature reached Re-warming too rapidly can cause vasodilatation, hypotension, and rapid electrolyte shift

Re-warming Prior to rewarming: Volume load aggressively with Normal Saline to compensate for reductions in BP, Scv02, and central venous pressure (CVP). K+ shifts to extra cellular compartment during re-warming. STOP all K+ containing fluids However, always correct hypokalemia, and other electrolytes, to the normal range.

Re-warming Re-warmed gradually in a controlled manner to avoid vasodilatation and hypotension. Goal is to re-warm the patient over 6-8 hours. Increase Cooling blanket setting by 0.5°C every 1 to 2 hour.

Re-warming Assess vital signs Monitor K+ every 4 hours and more frequently if needed Monitor serum glucose levels closely as insulin resistance resolves, increased risk for hypoglycemia. Follow ABGs as needed (temperature corrected) Adjust ventilator settings accordingly

Re-warming Anticipate reduction in venous return (cardiac output) and BP, as cooler blood shifts from core to extremities. Aggressive IV fluids may be necessary to maintain adequate volume status during re-warming. Maintain paralysis until patient temperature > 36°C. Once temperature > 36°C, paralysis can be stopped. Titrate sedation to comfort and ventilator synchrony.

Conclusion Evidences suggested that hypothermia can be used to prevent or limit damage to the injured brain It is important to induce hypothermia as quickly as possible, as protection appears to be greater when cooling is initiated early The successful application of hypothermia requires the use of strict protocols, vigilance and close attention to the prevention of side effects Some major side effects such as: hypovolemia, hypotension, electrolyte disorders, arrhythmias, hyperglycemia, bleeding complications, infection need to be monitoring closely and treated promptly The best cooling technique is one that is easy to use and at the same time effective.

References Laura H. Mcilvoy (2005) The Effect of Hypothermia and Hyperthermia on Acute Brain Injury AACN Clinical Issues Vol. 16, No. 4, pp. 488–500 Nursing practice manual (2007) Post Cardiac Arrest Therapeutic Hypothermia Hospital of the University of Pennsylvania Nov K. H. Polderman (2004) Application of therapeutic hypothermia in the intensive care unit Intensive Care Medicine I Larsson, E Wallin, S Rubertsson (2010) Cold saline infusion and ice packs alone are effective in inducing and maintaining therapeutic hypothermia after cardiac arrest Resuscitation 81 (2010) 15–19 A Alzaga, M Cerdan, J Varon (2006) Therapeutic hypothermia Resuscitation 70,369-380 T.M. Kozik (2007) Induced Hypothermia for Pt with Cardiac Arrest Critical Care Nurse Vol.26 No.5 OCT

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