Practical management of severe lung disease and injury (Proceedings)

The principles of management of patients with severe lung disease and injury are summarized and the cases depicting the use if these management techniques are presented.

Principle 1

Provide oxygen early and calm the patient with drugs so that they do not become more stressed.

Cats and small dogs that arrive should be immediately placed in a small box and this box flooded with high flow – 20-Liter per minute – of oxygen. It is preferred if the "struggling to breath pet be actually place in a cardboard box at the scene, before travel. If travel is being done by a pet ambulance carrier they should be instructed to provide this "high flow oxygen" into the box. Obviously those that are NOT CONSCIOUS require at least mouth to nose ventilation, or bag-valve-mask ventilation with near 100% oxygen.

Large dogs, that are too large for small boxes should receive a sedating drug on admission..prefer ketamine and butorphanol and acepromazine in doses of 1-2 mg/kg, 0.1 mg/kg and 0.01 mg/kg respectively given in the epaxial muscles and then as they settle oxygen is switched from giving by jet-flow and canopy techniques to bag-valve-mask with a tight fitting mask.

Animals that were initially placed in the small confined box should now be given the same cocktail of ketamine, butorphanol and acepromazine. This can be done by use of the IM epaxial route OR it may be that an IV rout can be provided by using an "oxygen bag-over-the cat technique" where the patient's small box is covered with a large enough clear-plastic bag and oxygen continued to be given at high levels enough to inflate the bag covering the box. The cat is "shaken" out of the box and into the clear-plastic flexible bag filled with oxygen. This technique is recommended to be able to give the cat its epaxial ket-but-ace cocktail – injecting right through the bag. It is very important not to try and handle the cat before it is sedated adequately enough. Ketamine is a very good bronchial-dilator and is good for the asthmatic case; the butorphanol is a redistributor of lung blood volume and a lowerer of vascular resistance and blood pressure which decreases intrapulmonary hemorrhage and edema in heart failure patients, the acepromazine cancels out the systemic hypertension caused by the ketamine. Together they work very well in most cases in my experience. This combination is also a good pre-anesthesia or pre-muscle blocker in those cases that will require rapid-sequence-induction and intubation to gain tracheal – airway control to allow for positive pressure ventilation, which many severe lung disease or injury cases will require.

Principle 2

If the animal is not responsive to supplemental oxygen is a very positive way with a very visible decrease in the patient's "work of breathing" then bag-valve-mask ventilation should be started and a PEEP valve on the end of the AMBU exhalation arm should be added and set for 5 cm H 2 O to start.

During that time an iv access should be gotten and other added medications considered to be given. These include further medication to calm the patient if needed, furosemide for cardiac and centroneurogenic induced pulmonary edema at 4-8 mg/kg body weight, mannitol for oxygen radical scavenging at a dose of 200 mg/kg body weight given very slowly, consider the use of methylprednisolone sodium succinate for the inflammatory component of pulmonary injury, at a dose of 2-4 mg/kg body weight. Note this is a very small dose compared to those used in the past which caused significant immune system compromise; and controversial but in my experience helpful in cases of aspiration pneumonia, severe lung hemorrhage and contusion and in suspected pneumonia, the delivery of a broad-spectrum bactericidal antibiotic such as a first generation cephalosporin, giving the first dose at double the regular dose to gain a tissue level rapidly. However, in these cases I recommend getting a culture of deep bronchus secretions and Gram's stain just before giving and tailoring subsequent iv doses with the finding on the Gram's stain and cytology. The sample collection is generally gotten before the iv antibiotics are given but the antibiotics not delayed past that time.

Principle 3

If the bag-valve mask ventilation does not decrease the patient's work of breathing within minutes and the WOB is still very severe, make sure that the following have been ruled out: 1. Pneumo or hemo or hydrothorax either by auscultation, ultrasound or horizontal beam preferred radiology. 2. Diaphragmatic hernia by same methods. If able to decompress the pleural space conditions with chest aspiration this should be accomplished immediately. In some cases, rapid sequence induction (RSI), will still need to be completed to gain control of the patient to allow decompression to be able to completed with as little stress as possible. In cases of pneumothorax, please keep in mind that by using IPPV we may be making the pneumothorax considerably worse rapidly. In these cases it is imperative to move quickly to decompress the pleural space. If RSI was deemed necessary in this case a simple but very effective means of decompression is to ias is to perform immediate small opening thoracotomy. This can be later converted to chest tube entrance sight or at least a facilitator of the placement of a chest – tube (preferred). This mini-thoracotomy can also be used to collect blood should evidence of a hemothorax is also noted with the chest is entered. Again usually in blunt or penetrating trauma causes of hemothorax the immediate placement of a chest tube and the continued aspiration of the blood from the chest will cause the leaks in the lungs to stop or at least greatly slow down. If after a few minutes it is noted that this is not occurring either a parasternotomy or formal mid-thoracotomy should be performed.

Rapid Sequence Intubation carries some risks to it is imperative that the following be completed in the following steps to avoid complications:

1. The patient must be first receiving oxygen by non-invasive ventilation (bag-valve mask assisted or anesthetic circuit assisted). If intubation is attempted in the very acidemic or hypoxic patient this can cause vaso-vagal induced profound hypotension, bradycardia, or ventricular asystole or fibrillation.

2. Even though the term RSI has the word "rapid" in it the drugs that are given are titrated in to provide the effect needed and it is OK to wait for the drug to take effect and this may be slightly longer than anticipated, especially in cardiovascularly compromised patients.

3. Begin by giving a pain reliever as intubation is painful and also give a parasympatholylitic such as glucopyrolate (preferred) or atropine. I like hydromorphone at 0.05 – 0.1 mg/kg slowly given and then give a hypnotic that will allow intubation. In my experience I like ketamine WITH diazepam because the combination can be fairly safe in the cardiovascularly compromised patient. A one-one volume mixture of these are given, generally slowly at a rate of 0.1 ml/kg (one ml per20 lb body weight). This generally allows gentile and safe intubation and does not drop blood flow as much as Propofol in my experience. Some animals may only require the hydromorphone while others will be so amped up that they will require a bit more ketamine. If they continue to "buck the IPPV provided by the person doing the hand bagging or the anesthetic or ICU ventilator then a muscle blocker is recommended. I prefer atricurium at 0.25 mg/kg body weight and then half doses are repeated as needed. Of course isoflurane can also help but care is given to watch for hypotension or decreased blood flow.

Principle 4

Use a lung protective strategy (LPS) and ventilate for at least several hours to several days depending on arterial blood gases, end tidal CO 2 levels, spO2 and radiographic changes. The LPS involves keeping barotraumas and lung shear stresses minimized. This involves aiming for peak inspiratory pressures to be limited to 17-18 cm H2O, using PEEP at 5-12 cm H2O, delivering oxygen concentrations below 60 mmHg if at all possible.

Principle 5

Use airway suctioning as required to keep major airways open. Hyper-oxygenate as needed prior to suctioning and if needed perform a tracheostomy to be able to wean off the ventilator more rapidly and still allow good tracheal toileting. IN SOME CASES immediate placement of a tracheostomy for oxygenation and tracheal toileting is recommended. These include the handing of severe inhalation pneumonia and bacterial pneumonia that has been very productive or resistant to common medical management. This allows for a continued decrease in work of breathing because it decreases resistance to airflows, and allows for direct micro-nebulization and humidification.

Principle 6

Don't forget about the rest of the patient and his/her needs. These include hydration and nutrition. Patients that are requiring positive pressure ventilation have been done are the common every day practice that does not have a fancy ventilator. It can be done by using intravenous drip pentobarbital sodium at 1 mg/kg/hr or other medications such as ketamine, lidocaine and morphine, Propofol, isoflurane, dometore and other mixtures of medications. Don't think it can't be done. I do not have the right drugs or equipment. I have never done this before. It can't work. I am here to tell you it can work. We had a family of four ventilate their puppy though a severe bout of centroneurogenic pulmonary edema following a choking episode in the yard. They took turns squeezing the AMBU bag connected to the endotracheal tube and euthanasia sodium pentobarbital was diluted severely down and added to the iv fluids to keep the dog asleep and not fighting the ET tube that remained in place with an occasional change every 6-12 hours. After the 5th hour of by-hand ventilation with the AMBU bag connected to a PEEP Valve and oxygen at 3-4 LPM the dogs breath sounds improved greatly and weaning was able to start commencing the following morning. He was able to be extubated the following day and he recovered.

Several Cases for Discussion if Time Permits

No-name

2 mo old M Jack Russell – stepped on by a horse – sustaining severe pulmonary injury, shock, suspected hemoabdomen, liver injury. The dog was intubated and ventilated and placed on a mechanical ventilator. Resuscitation continued with fluid and Oxyglobin support. A blood transfusion was also given and the dog was maintained on a BIRD anesthetic ventilator for 36 hours and gradually weaned off and onto nasopharyngeal oxygen. He made a complete recovery after another day of hospitalization, discharge and continued care by the RDVM.

Timber

2 yo German Sheppard Dog - Run over in the caudal thoracic region by a ¾ pickup truck, sustaining significant pulmonary contusion hemopneumothorax, hemoabdomen, shock, secondary vena cava obstruction caudally. Underwent resuscitation, chest tube placement, autotransfusion, DPL, exploratory celiotomy, liver packing and hemostatic agent application, continued autotransfusion, noninvasive support ventilation after extubation, CPAP with NP oxygen, enteral nutrition, and he made a complete recovery after an episode of severe ascities with the drainage of 3 L of fluid.

Noah

German Sheppard 6 month old male dog with severe pneumonia that had been to see several veterinarians. Each had prescribed antibiotics and expectorants. Subcutaneous fluids were also being given as prescribe by one of the veterinarians. Then a few days before admission he was hospitalized at another hospital and was given oxygen by cage, nebulization by cage and mask, and iv antibiotics of cephazolin, and iv fluids for two days. Despite this care he was determined to be getting much worse by the referring veterinarian. On admission radiographs revealed significant alveolar bronchograms throughout the ventral aspects of multiple lung lobes, he had a fever of 102.9 and was very depressed. He was showing an increase in respiratory rate and effort and breath sounds were decreased and there were wheezes bilaterally. The IV catheter site was slightly red and inflamed. On placing him on blow by oxygen there was some decrease in effort but rate was still increased. Based on the clinical signs it was recommended to perform some non-invasive ventilation to start after providing sedation and then performing RSI and after intubation to gain culture, cytology, Gram's stain. Then is was agreed upon to place him on the ventilator for a few hours and see if we could improve arterial gases, radiographs, etc., The owners agreed on this approach despite the poor prognosis that was provided. There was a suspicion that viral distemper might have been the cause of the pneumonia initially. The IV catheter site was cultured and the catheter changed. Labs were drawn and a left shift with 28,000 WBC and some toxic granulocytes as noted. Following IPPV with a bag-valve – mask the dog was anesthetized with hydromorphone, ketamine and acepromazine. When the trachea was intubated as sterilely as possible and a deep bronchial suctioning was completed. There was very thick secretions present and the Gram's stain revealed many rods and cocci and cytology revealed many degenerating neutrophils as well as others more normal in appearance. A culture was submitted. Based on the amount of exudate present within the lungs it was then suggested to the owners to have a temporary tracheotomy performed to allow for aggressive tracheal toileting that would still be able to done without the dog completely anesthetized which would decrease mucociliary clearance and suppress the immune system. The owners agreed and the tracheostomy was completed. While this was done PEEP at 5 cm H2O and a lung protective strategy was followed. An occasional sigh ventilation at 40 cmH2O was performed and continued for an hour post tracheotomy. Postural drainage, micronebulization with saline was gun and Amikacin was added to this at the conclusion of the ventilatory therapy. Throughout the next few days progressive improvement was observed and tracheal suctioning, micronebulization, breathing treatments with IPV and PEEP was delivered very 2-6 hours. Respiratory effort significantly improved and the suctioning was able to be discontinued after three days. It had begun as being needed several times an hour. The dogs tracheotomy tube was able to be removed on the third day and he recovered.