The employer and insurer appeal from the compensation judge’s determination that the employee’s death from a prescription drug overdose was causally related to his work injury.  We affirm.

On July 27, 2007, John L. Bowman, the deceased employee, sustained an admitted work-related injury to his low back while working as a mover for A & M Moving & Storage Company, the employer, which was insured for workers’ compensation liability by Vanliner Insurance Company.  The employee was initially treated with physical therapy, a TENS unit, and medications, including ibuprofen, Flexeril, and Percocet.^[1]  A lumbar spine MRI scan performed on September 18, 2007, indicated a mild broad-based disc bulge with a small left lateral disc protrusion, mild to moderate left L4-5 neural foraminal narrowing, and mild bilateral facet degeneration.  The employee continued to receive conservative care.

In February 2008, Dr. John Dunne treated the employee by prescribing Naprosyn and Darvocet, continuing Flexeril, and discontinuing ibuprofen.  The employee’s symptoms continued to worsen, and Dr. Dunne recommended a neurosurgical evaluation.  In May 2008, Dr. Dunne discontinued Naprosyn and prescribed Celebrex and Ambien.  In July 2008, Dr. Dunne discontinued the Darvocet prescription, prescribed Percocet, and continued prescriptions for Ambien, Flexeril, and Celebrex.

The employee was referred to Dr. Francis Denis for a surgical consultation which occurred on September 22, 2008.  At that time, the employee was taking Oxycodone, methocarbamol, Ambien, and Celebrex.  Dr. Denis recommended a selective nerve block at L4, which provided temporary relief of the employee’s pain.  Dr. Denis then recommended decompression surgery at L4-5.  Dr. Dunne continued the employee’s prescriptions for Ambien, Celebrex, Oxycodone, and Robaxin^[2] in October 2008.  In November 2008, another doctor prescribed Vicodin.

On November 26, 2008, the employee underwent a bilateral L4-5 foraminotomy/discectomy performed by Dr. Denis.  The employee continued to have low back and leg pain.  In December 2008, Dr. Denis prescribed a Medrol Dose Pak and Oxycodone.  In January 2009, Dr. Denis continued the employee’s prescription for Oxycodone and also recommended a discogram.  In February 2009, Dr. Dunne continued the employee’s prescriptions for Ambien, Robaxin, Celebrex, and Oxycodone.  The employee made a request for the discogram in order to proceed with further surgery.  The insurer denied the request, citing the need for further investigation and access to the employee’s medical records.  After an independent medical evaluation of the employee at the employer and insurer’s request, Dr. Paul Wicklund opined that a discogram was not needed.  In March 2009, the employee was referred to a pain clinic for an evaluation to assess his prescription use of Oxycodone.  On April 6, 2009, the employee filed a medical request for approval of the pain clinic referral.  The parties eventually agreed that the employee could be evaluated by Dr. Matthew Monsein for a pain clinic program.  In addition, the lumbar discogram was approved, completed on May 6, 2009, and indicated concordant pain from L1 to L5.  Dr. Denis recommended a L4-5 nerve block, which the employee received on June 2, 2009.  Soon after, Dr. Denis recommended a fusion/ decompression surgery at L4-5.

Also in June 2009, the employee was evaluated by Dr. Monsein for a pain clinic program.  During the evaluation, the employee reported a history of alcohol abuse and chemical dependency treatment, and reported that he was currently taking prescription medications, specifically Oxycodone, Celebrex, and methocarbamol.  After the evaluation, Dr. Monsein was of the opinion that the employee was not a good surgical candidate due to his multilevel degenerative disc disease, and recommended that the employee attend a pain management and rehabilitation program.  In his report, Dr. Monsein stated his concern that the employee was at risk for misuse of his prescribed medication given his long term use of narcotics and previous history of alcohol abuse.

Dr. Dunne also expressed concern about the employee’s use of narcotics after a June 2009 appointment, but renewed the employee’s prescriptions for Celebrex, Robaxin, and Oxycodone, pending approval for the surgery.  In a report dated June 23, 2009, after another independent medical evaluation, Dr. Wicklund did not agree with the proposed surgery.  He instead suggested a reconditioning program, a psychological evaluation, and reduction of narcotic medication.  The employee sought approval of the proposed surgery from the insurer.  The insurer subsequently denied the employee’s request for the proposed fusion surgery, basing the denial on Dr. Wicklund’s and Dr. Monsein’s reports, and further requested an evaluation of the employee by a neutral physician.

On August 6, 2009, the employee filed a medical request seeking approval of the fusion surgery.  The hearing on the medical request was scheduled for October 15, 2009.  The parties chose a neutral medical examiner, Dr. Paul Hartleben.  The compensation judge appointed Dr. Hartleben as the neutral physician by order dated September 28, 2009, and the neutral examination was scheduled for November 2009.  As a result, the hearing to address the disputed medical request seeking surgery was rescheduled before a compensation judge on December 22, 2009.  Pending the hearing, Dr. Dunne continued to prescribe Oxycodone to treat the employee’s pain.  In September 2009, Dr. Dunne prescribed Oxycontin and Oxycodone, as well as Celebrex, Robaxin, and Colace, but he continued to voice the opinion that the employee should decrease the use of pain medication.

In October 2009, the employee treated with Dr. Dunne and reported he was still waiting for his surgery, and was scheduled for the neutral physician examination in November 2009.  Dr. Dunne decreased the employee’s Oxycontin and Oxycodone prescriptions and continued the prescriptions for Celebrex, Robaxin, Colace, and Ambien.  On November 6, 2009, the employee underwent the neutral examination with Dr. Hartleben.  In a November 23, 2009, report, Dr. Hartleben opined that the employee was suffering from multilevel degenerative disc disease and discogenic pain from at least four lumbar discs, and that a one-level fusion surgery was not appropriate for the employee’s condition.

On November 26, 2009, the employee was found dead in his apartment.  The employee had spent the previous evening preparing for a Thanksgiving dinner with a friend.  He was found unresponsive the next day at about 4:45 p.m. and pronounced dead at 5:23 p.m.  His death certificate listed the cause of death as Oxycodone toxicity and the manner of death as “accident.”  An autopsy report, completed by Dr. Andrew Baker of the Hennepin County Medical Examiner’s office, listed Oxycodone toxicity at a level of 1.32 milligrams per liter as the diagnosis.  Dr. Baker testified that typical levels of Oxycodone are one-fifth to one-tenth of that level, and that the level found in the employee’s blood was life-threatening.  Dr. Baker ruled out natural causes, homicide, and suicide as the manner of death since there was no evidence to support any of them.  He concluded that it was more probable than not that the employee’s death was an accident.  In response to the employer and insurer’s questions, Dr. Baker also testified that he did not know the reason for the employee’s high level of Oxycodone, and agreed that level could be reached through inadvertence or recreational use.  The medical examiner’s report indicates that when Dr. Dunne was questioned regarding the possibility of the employee using medication illicitly or from outside sources, he denied any such knowledge and stated that he would have terminated the employee’s treatment if there were any questions about these issues.  Dr. Dunne also stated that the employee did not appear to be “med-seeking.”

Rick Kingston, Pharm.D., reviewed the employee’s most recent medical records, Dr. Baker’s reports, and the autopsy report at the employer and insurer’s request.  Dr. Kingston opined that the level of Oxycodone found in the employee’s blood at the time of death was inconsistent with the Oxycodone dosages prescribed for him.  Dr. Kingston also could not determine the reason for the employee’s high level of Oxycodone.

On February 15, 2012, Carol McIntire, the employee’s mother and the personal representative for his estate, filed a claim for dependency benefits or payment to the employee’s estate under Minn. Stat. § 176.111, subd. 22.^[3]   The employer and insurer denied the petition, arguing that substantial evidence did not support the petitioner’s claim that the employee’s death due to Oxycodone toxicity was causally related to the employee’s work injury.  A hearing was held on November 29, 2012.  The compensation judge found that the employee’s death was causally related to the employee’s July 2007 work injury, and awarded payment to the employee’s estate as well as funeral and burial expenses.  The employer and insurer appeal.

The Workers’ Compensation Court of Appeals must determine whether the findings of fact and order are clearly erroneous and unsupported by substantial evidence in view of the entire record as submitted.^[4]   Substantial evidence supports the findings if, in the context of the entire record, they are supported by evidence that a reasonable mind might accept as adequate.^[5]   Fact findings are clearly erroneous if the reviewing court, looking at the entire evidence, is left with a definite and firm conviction that a mistake has been committed.^[6]   Findings of fact should not be disturbed, even though the reviewing court might disagree with them, “unless they are clearly erroneous in the sense that they are manifestly contrary to the weight of the evidence or not reasonably supported by the evidence as a whole.”^[7]

The issue presented to the compensation judge at hearing was whether the employee’s death from a prescription drug overdose was causally related to his July 27, 2007, work injury.  On appeal, the appellants contend the petitioner failed to present sufficient evidence to prove a causal connection between the death and the work injury, and further contend the compensation judge failed to apply the appropriate standard of proof regarding causation to reach his ultimate finding that “the employee’s death due to Oxycodone toxicity was causally related to his admitted work-related back injury.”^[8]   We are not persuaded by the appellants’ arguments.

Minn. Stat. § 176.111 provides for a $60,000.00 payment to a deceased employee’s estate “[i]n every case of death of an employee resulting from personal injury arising out of and in the course of employment where there are no persons entitled to monetary benefits of dependency compensation.”^[9]   The petitioner has the obligation to present sufficient proof to meet the evidential burden that the death of the employee arose out of and in the course of employment.  Each case presenting the issue of what “arising out of and in the course of employment” means in a particular fact setting requires the compensation judge to take into consideration the sufficiency of the evidence offered to analyze the issue for determination.  The appellants contend there is no evidence to establish a causal connection between the employee’s death and the work injury.  We disagree.

The employee was prescribed Oxycodone for pain associated with his work injury.  The cause of death was acute Oxycodone toxicity.  While there was no one specific piece of evidence to explain the toxic level of oxycodone in the employee’s system, there were a number of facts in evidence which allowed the compensation judge to infer an explanation for the level of Oxycodone in the employee’s body^[10] and ultimately to reach a conclusion on a causal connection between his death and the work injury.^[11]

The appellants maintain that because there were multiple explanations for the acute level of Oxycodone in the employee’s body, there was no proof of cause or reason for the manner of death and thus no causal connection between the death and the work injury.  Conflicts in expert medical testimony and other reliable evidence to support or deny a causal connection must be resolved by the compensation judge.^[12]   For a causal relationship to exist between an employee’s death and a work-related injury, the condition need not be the sole or even the most direct cause of death, provided the petitioner demonstrates that the compensable injury was a contributing factor in the employee’s demise.^[13]   Injury or disability caused by medical treatment provided to treat a work-related injury is compensable.^[14]   Death resulting from an accidental overdose taken to relieve pain caused by a work-related injury may be compensable.^[15]

The compensation judge relied on the expert medical opinion of the chief medical examiner as well as other evidence to reach the ultimate determination on causation.  The employee had a work-related low back injury followed by an unsuccessful back surgery.  He was waiting for a surgical fusion and was treating his low back pain with Oxycodone and muscle relaxants prescribed by his treating doctors.  The parties agreed that the medications were prescribed for pain associated with the work injury and were reasonable and necessary medical treatment as prescribed.  The employee also was prescribed antidepressants because of depression caused by his frustration with insurance delays.  The employee died of Oxycodone toxicity.  His use of Oxycodone prescribed as a result of his work-related low back condition caused his death.

Dr. Baker, the chief medical examiner, performed a forensic examination, reviewed the employee’s orthopedic surgical history, and issued an autopsy report certifying the cause of death as Oxycodone toxicity and listing the manner of death as accidental.  Dr. Baker explained that in deciding the manner of death, he must choose from the following five options:  (1) natural death, (2) accident, (3) homicide, (4) suicide, or (5) undetermined.  In his deposition, Dr. Baker explained his rationale for his opinion:

By comparison, the employer and insurer offered the expert medical testimony of Dr. Kingston.  Like Dr. Baker, Dr. Kingston concluded that the employee died from Oxycodone toxicity.  Dr. Kingston also could not find any specific reason for the level of Oxycodone found in the body at the time of death.  Dr. Kingston discussed possible causes including suicide, drug abuse, recreational drug use, and therapeutic errors.  But unlike Dr. Baker, Dr. Kingston could not “find any particular theory more likely than another.”^[20]   On the basis of his own finding, Dr. Kingston provided an expert medical opinion that the employee’s manner of death could not be determined.

Here, the manner of death surrounding an unexplained overdose was reconciled by the compensation judge who accepted the expert medical opinion of Dr. Baker over the opinion of Dr. Kingston and found an accidental overdose of a drug prescribed for a work-related injury was sufficient evidence to conclude the employee’s death due to Oxycodone toxicity was causally related to his July 27, 2007, work injury.  The compensation judge did not erroneously shift the burden of proof to the employer and insurer.

Under the facts of this case, we conclude the judge’s assessment of the medical evidence on a causal relationship between the employee’s use of prescription pain medication for his work injury and his death by Oxycodone toxicity, as noted in the autopsy report, constitute sufficient evidence to support the findings that the employee’s death was more likely than not due to the accidental overdose of Oxycodone.  The compensation judge did not err in finding the employee’s death was causally related to the admitted work injury, and we affirm.